Link - Division of Inorganic Chemistry

INOR 1
Investigating the oxidation of olefins using derivatives of the non-heme iron catalyst [Fe(BPMEN)](OTf)2]
Claire A. Lidston1, [email protected], Matthew R. Davies1, Robert D.
Pike2, Christopher Goh1, [email protected]. (1) Dept of Chemistry, Williams College,
Williamstown, Massachusetts, United States (2) Colg of William Mary, Williamsburg, Virginia, United States
The complex [Fe(BPMEN)](OTf)2 (N,N‘-bis(2-pyridylmethyl)-1,2-diaminoethane) has been established as a highly active
and selective catalyst for the epoxidation of olefins using H2O2 as an oxidant by the pioneering work of Que, Jacobson,
and others. We examined the effects of systematically varying substituents on the amine backbone and on the pyridine
rings of the original BPMEN ligand framework on the efficiency of these iron (II) non-heme oxidation catalysts. The
substituents chosen differed in their steric effects and their electron donating and withdrawing properties. We structurally
characterized the complexes and tested their effectiveness in oxidizing alkenes (1octene, styrene, cyclohexene, oleic
acid). The complexes showed varying degrees of effectiveness in substrate consumption and product selectivity.
INOR 2
Metal cation detection using a novel small molecule chemosensor
Daniel T. de Lill, Arianna M. Gagnon, [email protected], Michael Brown, Kenneth
Shelley, [email protected], Mykela DeLuca. Chemistry and Biochemistry, Florida
Atlantic University, Boca Raton, Florida, United States
This presentation focuses on the continual research of a novel small molecule sensor, benzo[1,2-b:4,5-b’]dithiophene-4,8dione (“dione”), and its capacity to sense group one and group two metal cations using absorption spectroscopy as well
as ratiometric analysis of these spectra. Through weak intermolecular interactions, the dione can quantitatively detect
various metal cations by analyzing their absorption intensities and comparing them to their respective concentrations.
Current research is focused on ascertaining the detection limits of this chemosensor for each targeted metal cation.
Attempts to grow crystals of the dione with metal salts is currently in progress as experimental evidence for weak
intermolecular interactions. The dione’s capacity to sense biologically hazardous transition metal species will also be
studied.
The chemical structure of benzo[1,2-b:4,5-b’]dithiophene-4,8-dione (“dione”)--the chemosensor of interest.
INOR 3
Tripodal carbamoylmethylphosphine oxide (CMPO) ligands for f-element chelation: Solution photophysical
studies and lanthanide/actinide extraction properties
Eric J. Werner2, [email protected], Shannon M. Biros1, Shelby N. McGraw2, David A.
Hardy2, Hope T. Sartain1. (1) Grand Valley State University, Allendale, Michigan, United States (2) The University of
Tampa, Tampa, Florida, United States
The development of nuclear power as a viable alternative energy source creates the need for advanced waste
remediation processes. A major focus of nuclear waste treatment involves the separation and extraction of the various
actinide (An) and lanthanide (Ln) ions present to facilitate proper storage and further processing. Concerns related to both
the high-level radioactivity of select An elements and the value in recovery and recycling certain Lns for various
applications have encouraged recent research efforts aimed at the selective extraction of the f-elements. Inspired by the
current use of carbamoylmethylphosphine oxide (CMPO) in the TRUEX process for removing transuranic elements from
nuclear waste streams, we have initiated the development of novel tripodal CMPO-based ligands. In tethering three
CMPO chelators via a tripodal capping scaffold, high-denticity ligands are generated for further solution and extraction
studies. In this presentation, a new TREN-capped ligand will be discussed with regard to general solution coordination
chemistry and f-element extraction properties. Photophysical studies are used to probe the so-called “antenna effect”
displayed by this ligand, and luminescence decay lifetimes are measured to determine the number of bound solvent
molecules in solution. Finally, the selectivity of the ligand in extracting lanthanides is explored and quantified by ICP-AES.
INOR 4
Synthesis of a series of first row transition metal complexes containing a tetradentate ligand
Hannah F. Drake1, [email protected], Anastasia Blake2, Courtney M. Donahue2,
Scott R. Daly2, Brian J. Bellott1, [email protected]. (1) Western Illinois University, Macomb, Illinois, United States (2)
Chemistry, University of Iowa, Corravile, Iowa, United States
The reinvestigation of the synthesis of a series of first row transition metal complexes with the tetradentate ligand 1,3,7,9tetraaza-4,10-diketo-6,12-diphenyl-2,8 dithiocyclododecane will be reported. All complexes have been characterized via
FTIR, 1H NMR, melting point, and elemental analysis. Select single crystal structures will be reported and discussed.
Preliminary suflur and chlorine K-edge XAS results will be presented.
INOR 5
Lanthanides, chirality, and ionic liquids: Finding a niche with undergraduates
Todd Hopkins, [email protected]. Chemistry, Butler University, Indianapolis, Indiana, United States
Chiral ionic liquids (ILs) are ionic liquids that have a chiral cation and/or anion. Chiral ILs have been utilized in numerous
asymmetric applications, including asymmetric catalysis and enantiomeric separations. This presentation will describe our
group of undergraduate student’s efforts to measure and characterize the chiral discrimination by amino acid based chiral
ILs using circularly polarized luminescence (CPL) spectroscopy. Luminescent lanthanide (Eu 3+ and Tb3+) complexes are
ideally suited for the task, because of their luminescence and CPL properties. Results will be described from chiral
discrimination studies of europium complexes with amino acid methyl ester ILs (e.g. L-leucine methyl ester
bistrifluoromethanesufonimide), and
tetrabutylammonium amino acid ILs (e.g. tetrabutylammonium L-prolinate). The rewards and challenges working with
undergraduates on this research will be discussed.
INOR 6
Interconversion of eight-coordinate, dodecahedral, rhenium(V) isomers supported by a single chelating ligand
Harpreet Sodhi, Cristin P. Bosko, Sana Rashid, Gregory A. Moehring, [email protected]. Department of
Chemistry and Physics, Monmouth University, West Long Branch, New Jersey, United States
Several years ago Walton and coworkers reported the crystal structures for two eightcoordinate rhenium(V) isomers with
the formula [ReH2(mhp)(PPh3)2]+ (where mhp = the anion of 2-hydroxy-6-methylpyridine). Both isomers have
dodecahedral coordination and are best distinguished from one another by the coordination of the chelating ligands. In
one isomer, both of the chelating ligands constitute the four vertices of one of the dodecahedron's trapezoids while in the
other isomer both chelating ligands occupy coordination sites on both of the dodecahedron's trapezoids. Subsequent to
Walton's report, Crabtree and coworkers proposed a pseudorotational rearrangement for dodecahedral rhenium(V)
centers supported entirely by monodentate ligands. Serendipitously, we identified isomers of certain rhenium(V) centers
supported by monodentate ligands that included an unsymmetrical aromatic amine ligand. Those isomers related well to
the report by Crabtree. Through a study of one such eightcooridinate complex that included a chiral center, we found
support for the notion that the rearrangement of ligands at such centers includes a change in the steric relationship of the
B vertices of the dodecaheral coordination set consistent with Crabtree's proposed pseudorotational rearrangement
mechanism. The work presented here bridges the report by Walton regarding dodecahedral centers supported by two
chelating ligands and the work by Crabtree and ourselves which centered on dodecahedral centers supported entirely by
monodentate ligands. This work examines eight-coordinate dodecahedral centers supported by a single cyclometallated
iminecontaining ligand. We extended our previous report of reactions between benzaldimines and ReH7(PPh3)2, to make
the compounds for study, by expanding the aromatic group of the imine reactant to include a substituted pyrrole, a
substituted thiophen, and substituted 2-hydroxy-aromatic amines. The deprotonated 2-hydroxy-aromatic aminecontaining
products were of particular interest due to a change in the metallocylce size from five members to six members and
coordination of the ligand through oxygen and nitrogen rather than through carbon and nitrogen. Our variable temperature
NMR studies of these chelating ligand-supported, eight-coordinate, centers demonstrate that such compounds exist, in
solution, as isomers and allowed us to measure the activation entropy and activation enthalpy for the interconversion of
the isomers.
INOR 7
Methanobactin-inspired coordination chemistry with new mixed-donor ligands
Daniel Rabinovich, [email protected]. UNC Charlotte Chemistry, Charlotte, North Carolina, United States
We have been developing new bidentate ligands containing both pyridine and
N-heterocyclic thione (NHT) or selone donor groups with the goal of preparing synthetic analogues of methanobactin
(mb), a fascinating small protein that plays a key role in the acquisition and transport of copper ions in methane-oxidizing
bacteria. This presentation will outline recent advances in the synthesis and reactivity of several new mixed-donor ligands,
including some that are useful for mimicking the metal center in mb. The coordination chemistry of these ligands towards
a variety of main group and transition metal ions, including molybdenum(0), manganese(I), rhenium(I), copper(I), silver(I),
zinc(II), cadmium(II), mercury(II), indium(III), tin(IV), antimony(III) and bismuth(III), will be described.
INOR 8
Utilization of sulfonamides in crystal engineering
Christopher Hamaker, [email protected], Zachary E. Lawton, Mark
Oblazny. Chemistry, Illinois State University, Normal, Illinois, United States
Work in our group is focused on the investigation and utilization of functionalized sulfonamides for the preparation of
organic and metal-organic frameworks. Early investigations have focused on studying how other functional groups present
in the molecule affects the intermolecular interactions between the sulfonamide groups. Varying the substituents on the
arene rings of the molecule can lead to unique hydrogen-bonding patterns. This presentation describes our early results in
designing organic and possibly metal-organic frameworks based on sulfonamides.
INOR 9
Road to genome expansion is paved with good intentions: When DNA repair goes awry
Sarah Delaney, [email protected]. Brown University, Box H, Providence, Rhode Island, United States
Triplet repeat sequences, such as CAG/CTG, expand in the human genome to cause several neurological disorders.
Interestingly, the oxidatively damaged nucleobase 8oxo-7,8-dihydroguanine (8-oxoG) has been implicated in triplet repeat
expansion. Our overall objective is to define the molecular mechanism of triplet repeat expansion and determine the
extent to which 8-oxoG plays a role as the chemical founder event. We have identified a hot spot for DNA damage in the
non-canonical structures adopted by CAG/CTG DNA, and performed a comprehensive kinetic analysis of base excision
repair (BER) on these repetitive DNA substrates. These results have allowed us to propose a toxic cycle in which BER is
initiated on triplet repeat sequences and damage accumulates in repair intermediates, resulting in an incremental
expansion of the triplet repeat sequence. In fact, initiation of BER on triplet repeat DNA is detrimental and ultimately
results in disease-initiating expansion. Recent work has explored BER on CAG/CTG sequences in the context of
nucleosome core particles.
INOR 10
Snapshots of metallobleomycin-DNA recognition and binding: A tale of two tails Eric C. Long1, [email protected],
Millie M. Georgiadis1,2. (1) Department of Chemistry and Chemical Biology, Indiana University (IUPUI), Indianapolis,
Indiana, United States
(2) Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, IUPUI, Indianapolis,
Indiana, United States
Research efforts devoted to the study of metal complex–DNA interactions and DNA cleavage agents in general owe much
of their inspiration to the discovery and study of the family of natural products collectively referred to as the
metallobleomycins. In this area we were successful a number of years ago in applying an established host-guest
crystallization system to the investigation of DNA-bound metallobleomycins. In our initial structures of Co(III)•bleomycin B2
bound to a 5´-GTT site, details of the DNA-bound drug structure were revealed that complemented previous NMR
investigations. More recently, we have crystallized Co(III)•bleomycin A2 bound to the same 5´-GTT DNA recognition and
cleavage site. In these new structures, unlike all reported structures derived from NMR investigations (or our own previous
crystal structures of B2), a wholly
different, 180˚ "flipped" bithiazole intercalation insertion has been observed. Given that the difference between the
bleomycin congeners examined lies only in the chemical nature of their far C-terminal tails (B2 contains a guanidinium
while A2 contains a dimethylsulfonium), these new findings suggest that the far C-terminal "tail" moiety of the bleomycins
can be influential in determining the orientation of bithiazole intercalation at some DNA sites. These observations also
indicate that a "flipped" bithiazole orientation (accomplished through 180˚ rotation about the bond connecting the Cα
methylene–C2´ position of the amino terminal thiazole ring) remains competent to support DNA-drug binding. Ongoing
detailed studies of the metallobleomycins thus appear to continue to reveal interesting aspects of this drug–DNA binding
process that may further influence the overall study of metal complex–DNA interactions in the future.
INOR 11
Scrutinizing DNA damage
Megan Nunez, [email protected]. Chemistry , Wellesley College, Wellesley, Massachusetts, United States
DNA is constantly under attack by endogenous and exogenous agents that can alter its structure and thereby its function.
We use a variety of biophysical techniques to examine the structural, thermodynamic, and kinetic alterations caused by
base lesions, mismatches, and small-molecule binding. Our base lesion work has focused on three very different
alterations: 8-oxoguanine (8oxoG), spiroiminodihydantoin (Sp), and the cis-syn thymine dimer (TT). Careful examination
has shown 8oxoG to be almost indistinguishable by every technique from the guanine base from which it is derived,
whereas TT shows pronounced differences from its parent. Most notably, the equilibrium constant for base pair opening is
asymmetrically altered by the formation of the thymine dimer lesion, whereas base pair opening is unperturbed by the
8oxoG lesion. Our recent work focusing on packing of the Sp lesion into nucleosomes reveals that the core particle
structure can flexibly accommodate the lesion, although with surprising structural and thermodynamic effects. As we move
forward, new single molecule studies are beginning to reveal subtle thermodyamic and kinetic details about duplex
stability with lesions, mismatches and small molecules.
INOR 12
Formation and characterization of platinum adducts on ribosomal RNA
Xun Bao, Christine S. Chow, [email protected]. Department of Chemistry, Wayne State University, Detroit, Michigan,
United States
As major players in translation and the cell life cycle, ribosomal RNAs (rRNAs) exhibit a high level of structural diversity.
The anticancer drug cisplatin has been applied as a chemical probe to determine solvent and structural accessibility of
guanosine sites on rRNAs. Aquated cisplatin has been shown to accumulate faster on RNA than DNA, and Pt(II) adducts
are retained on rRNA at a variety of sites. The goal of our work was to design new RNA-targeting platinum(II) compounds
for chemical probing applications, as well as the development of anticancer drugs that could potentially overcome DNA
repair-related resistance. In this study, amino-acid-linked platinum(II) analogues were synthesized. Their reactivity and
product profiles were evaluated on the nucleoside level by using high performance liquid chromatography and nuclear
magnetic resonance spectroscopy. Tandem mass spectrometry was used to assess the effects of Pt(II)adduct formation
on glycosidic bond strength and to obtain an atomic-level understanding of the nucleoside-Pt(II) products. These results
reveal a cisplatin analogue with a template-independent adenosine preference, and demonstrate that Pt(II) reactivity can
be tuned by altering the carrier ligand(s).
INOR 13
Enhancing extracellular proteostasis through the unfolded protein response
Joseph Genereux2, [email protected], Jeffery W. Kelly1, Rockland Wiseman3. (1)
BCC 265, Scripps Rsrch Inst, La Jolla, California, United States (2) TSRI, La Jolla,
California, United States (3) The Scripps Research Institute, La Jolla, California, United
States
Extracellular protein aggregation is etiologically responsible for many amyloid disease pathologies. In intracellular
environments, organelle-specific stress-signaling pathways respond to the presence of misfolded proteins by inducing
chaperone expression to restore proteostasis. In contrast, extracellular environments such as the blood must rely on
protein secretion from cells to provide their proteome and do not have a defined mechanism to restore proteostasis in
response to stress. Because misfolding-prone proteins that reach the extracellular space typically originate in the
endoplasmic reticulum (ER), we hypothesized that the Unfolded Protein Response (UPR), the signaling pathway that
enhances ER proteostasis in response to misfolded protein in the ER, might also induce chaperone secretion to enhance
extracellular proteostasis.
We identified and validated the ER Hsp40 ERdj3 as a UPR-regulated secreted chaperone, both in cell culture and in living
mice. Secreted ERdj3 binds misfolded proteins in the extracellular space and substoichiometrically inhibits protein
aggregation, consistent with a holdase chaperone activity. ERdj3 also attenuates proteotoxicity of disease-associated
toxic prion protein, demonstrating that it can functionally enhance extracellular proteostasis. Under conditions where ER
chaperoning capacity through the Hsp70 cycle is overwhelmed, ERdj3 can co-secrete with destabilized, aggregationprone
proteins in a stable complex. This novel mechanism preemptively provides extracellular chaperoning of proteotoxic
misfolded proteins that evade ER quality control, and directly links ER and extracellular proteostasis. In summary, we find
that ERdj3 secretion provides a mechanism for the UPR to enhance extracellular proteostasis in response to threats
originating in the early secretory pathway.
INOR 14
Molecular shape control applied to the dynamic capture and release of biorelevant substrates
Anne Petitjean, [email protected]. Dept of Chem, Chernoff Hall 410, Queens University, Kingston,
Ontario, Canada
The shape of molecules is an important feature dictating their interactions (i) amongst themselves, and (ii) with others. In
this presentation, we will illustrate the impact of molecular conformations of artificial species on the capture and release of
organic and inorganic substrate, as well as on selective DNA binding, and, time permitting, on selfassembly. Applications
to drug development and drug delivery will be discussed.
INOR 15
Systematic material design using biomolecules
Takanori Tamaki, [email protected]. Chemical Resources Laboratory, Tokyo Institute of Technology,
Yokohama, Japan
We have proposed systematic material design to fully utilize the characteristics of biomolecules in enzymatic biofuel cells
and DNA-conjugated stimuli-responsive membranes.
Enzymatic biofuel cells can use non-toxic fuels like glucose and ethanol, and have the potential to power portable devices.
One important issue to be addressed is their low power density caused by their low current density. Considering the high
intrinsic activity of enzymes, the current density can be increased to reach 10 2 mA/cm2, a value comparable with that
observed in conventional direct methanol fuel cells. Our approach focused on the rate-limiting step in enzyme electrodes.
First, to overcome the ratelimiting step of electron conduction through the redox polymer, we proposed a highsurface-area
three-dimensional biofuel cell electrode made of redox-polymer-grafted carbon black to decrease the electron conduction
distance in the redox polymer. The effectiveness of this electrode was verified by experiments and a mathematical model.
Further study revealed that the deactivation of enzymes upon adsorption on hydrophobic surface of carbon black should
be decreased to obtain higher current density. We tried surface modification of carbon black to prevent the physical
adsorption of enzymes on carbon black and then immobilize enzymes using a method other than physical adsorption.
DNA-conjugated stimuli-responsive membranes coordinate the molecular recognition properties of DNA and actuator
properties of thermoresponsive polymer, poly(Nisopropylacrylamide) (pNIPAM), in pores of a porous substrate. In some
specific conditions, DNA-pNIPAM changes its dispersion state in response to whether conjugated DNA is single-stranded
(ss) or double-stranded (ds). This property was then combined with the molecular recognition of DNA aptamer; molecular
recognition of aptamer induced aggregation of DNA-pNIPAM via dissociation of conjugated dsDNA, leaving ssDNA on
pNIPAM. When this DNA-pNIPAM was grafted on pores of the porous substrate, permeability of the membrane increased
in the presence of the target molecule of the aptamer.
INOR 16
Measuring hydride donor ability to guide catalyst design for reduction reactions
Jenny Yang, [email protected], Charlene Tsay, Juliet Khosrowabadi Kotyk, Brooke
Livesay. Chemistry, University of California, Irvine, Irvine, California, United States
Transition metal hydrides are essential intermediates in a variety of catalytic reactions. Thermodynamic mesaurements of
the ionicity of the M-H bond, or hydride donor ability, can provide a framework for designing new catalysts for reduction
reactions. In these studies, we are measuring the hydride donor ability of a series of transition metal complexes in organic
solvents and water. This information is being used to rationalize reactivity and develop new catalysts for H 2O reduction to
H2 and CO2 reduction to HCO2−.
INOR 17
Next generation redox-active “ligands” from non-innocent coordination complexes
Alan F. Heyduk, [email protected]. Univ of California, Irvine, California, United States
Coordination of the redox-active (SNS) pincer ligand ((SNS)H3 = bis(2-mercapto-ptolyl)amine) to tungsten or molybdenum
affords a homoleptic complexes, M(SNS)2 (M = Mo, W), that display non-innocent electronic behavior and are best
described as as MIV species. These complexes themselves can be used as redox-active ligands or cofactors to another
metal center providing a new heterobimetallic architecture. This talk will focus on the synthesis and characterization of
novel M(SNS)2M'(L2) complexes (M = Mo, W; M' = Co, Ni, Cu; L2 = chelating phosphine or diimine) over multiple oxidation
states. Electrocatalytic activity of one derivative will be highlighted.
INOR 18
Synthetic chemistry as a wIndow into biology: Probing molecular complexity with small molecular species
A. S. Borovik, [email protected]. Department of Chemistry, Univ of California-Irvine, Irvine, California, United States
The local environment in which a metal complex resides has an instrumental role in determining physical and chemical
properties. These effects are best exemplified in metalloproteins, in which the local environments surrounding metal
complexes have a major impact on reactivity and selectivity of metal-mediated processes. Intramolecular hydrogen bonds
are one of the key interactions that aid in controlling the local environment, yet it is challenging to duplicate these types of
interactions in synthetic constructs. This talk will describe our latest designs of ligand systems that support intramolecular
non-covalent interactions within the secondary coordination of metal complexes and show how they are used to activate
small molecules. Included in the discussion is the detection of new transient species, including high valent iron and
manganese species with terminal oxo ligands.
INOR 19
Evaluating metal–carbon orbital mixing in metallocene dichlorides
Stosh A. Kozimor5, [email protected], Enrique R. Batista4, Justin N. Cross5, David L.
Clark3, Jason M. Keith1, Richard L. Martin6, Stefan G. Minasian7, David K. Shuh2, Chantal S. Stieber5, Julie A. Trujillo5,
[email protected] Tyliszczak8. (1) Dept of Chemistry,
Colgate University, Hamilton, New York, United States (2) Lawrence Berkeley Natl Lab,
Berkeley, California, United States (3) Natl Security Education Center, Los Alamos
National Laboratory, Los Alamos, New Mexico, United States (4) Theoretical Division,
Los Alamos National Laboratory, Los Alamos, New Mexico, United States (5) Los
Alamos Natl Lab, Los Alamos, New Mexico, United States (6) Los Alamos National
Laboratory, Los Alamos, New Mexico, United States (7) LBNL, Berkeley, California, United States (8) LBL, Berkeley,
California, United States
Advancing understanding of metal–light atom (C, N, and O) electronic structure and bonding is of widespread interest
because these interactions control the physics and chemistry of many important technological processes. This is
especially true for systems with σ and π M–C bonds, as demonstrated in industry through polymerization of organic
molecules and in nature through catalysis in organometallic reactions. Among the few experimental methods that can be
used to quantify metal-ligand orbital mixing, ligand K-edge X-ray absorption spectroscopy (XAS) stands out as unique.
Seminal work by Solomon, Hedman, Hodgon, and coworkers has established ligand K-edge XAS as a powerful technique
for quantifying covalency for M–Cl and M–S bonds. The method probes bound state transitions between core ligand 1s
and unoccupied molecular orbitals, which only have intensity if the empty acceptor orbitals contain ligand p character. In
principle, C K-edge XAS can also be used to quantify M–C orbital mixing because the underlying physics governing Cl
and S K-edge XAS also holds for carbon. However, the C K-edge (ca. 280 eV) is much lower in energy than that for Cl
and S (>2400 eV). Thus, acquiring quantitative C K-edge XAS data are complicated by weakly penetrating incident
radiation that is potentially susceptible to surface contamination and saturation effects from the samples. This
presentation will describe our efforts to overcome these technical challenges and document recent measurements made
on some organometallic systems, like (C5R5)2MX2. Results are presented in the context of previously-published Cl K-edge
XAS and DFT analyses of the same (C5H5)2MCl2 metallocenes, which provides a consistent bonding picture from the
perspective of both the ancillary C5H51- and reactive Cl1- ligands.
INOR 20
Covalency in actinide metallocene complexes
David L. Clark, [email protected]. Natl Security Education Center, Los Alamos National Laboratory, Los Alamos, New
Mexico, United States
Metallocene complexes have played a seminal role in our understanding of chemical bonding in the actinide series, and
form a unique family of structurally similar compounds with which to evaluate trends in metal-ligand bonding and
electronic structure across the actinide series. A review of recent spectroscopic evidence for covalency in actinide
metallocenes will be provided.
INOR 21
Bond strength in molecular f element compounds from the quantum theory of atoms in molecules
Qian-Rui Huang, Jennifer R. Kingham, Abigail Mountain, Nikolas Kaltsoyannis, [email protected]. Department
of Chemistry, University College London, London, United Kingdom
The strength of the bonds between f block metals and other elements is of great fundamental interest and also of
relevance to, for example, minor actinide partitioning technologies. The determination (either experimentally or
computationally) of f element bond strengths is, however, not straightforward. In recent years we have employed the
quantum theory of atoms-in-molecules (QTAIM) of Bader and co-workers [1] to study the electronic structure of f element
compounds, and have found that its electron density-based approach yields insights into chemical bonding which are
complementary to the more traditional tools of quantum chemistry [2-6]. In this presentation I will discuss our very recent
application of the QTAIM to the calculation of the strength of f element–ligand bonds [7-8].
[1] R. W. F. Bader, Atoms in Molecules: A Quantum Theory, OUP (1990)
[2] S. M. Mansell et al., J. Am. Chem. Soc. 133 9036 (2011)
[3] D. M. Schnaars et al., Inorg. Chem. 51 8557 (2012)
[4] N. Kaltsoyannis, Inorg. Chem. 52 3407 (2013)
[5] J. L. Brown et al., J. Am. Chem. Soc. 135 5352 (2013)
[6] M. B. Jones et al., Chem. Sci. 4 1189 (2013)
[7] A. R. E. Mountain and N. Kaltsoyannis, Dalton Trans. 42 13477 (2013)
[8] Q.-R. Huang et al., Dalton Trans. 43 (2014) DOI: 10.1039/C4DT02323D
INOR 22
Group 11 cluster chemistry: What I didn’t learn in the Evans Lab
Justin R. Walensky1, [email protected], Andrew Lane2, Pokpong
Rungthanapathsophon2. (1) Chemistry, University of Missouri, Columbia, Missouri, United States (2) University of
Missouri-Columbia, Chesterfield, Missouri, United States
Group 11 chemistry has applications in many facets of life from medicine to catalysis. Our interest is focused on
multinuclear group 11 clusters for their biomimetic and spectroscopic properties as well as multi-electron redox reactivity.
In nearly all cases, copper is coordinated through nitrogen (histidine) or sulfur (cysteine or methionine) in the protein. We
have endeavored to explore the structure, spectroscopy, and reactivity of di-, tri-, and tetranuclear group 11 metal
complexes with amidinate and dithiocarboxylate ligands. The synthesis, spectroscopy, and reactivity of these complexes
will be presented.
INOR 23
Practical models for organometallic chemistry
Warren Hehre, [email protected]. Wavefunction, Inc., Irvine, California, United States
Density functional models suitable for routine applications to transition metal organometallics and organolanthanides with
molecular weights up to 500-800 amu are described, assessed and illustrated. Focus is on elucidating molecular
structures and conformations, assigning NMR spectra and establishing thermodynamic and kinetic reaction preferences.
INOR 24
Spin coherence transfer using photogenerated spin-correlated radical pairs Michael R. Wasielewski, [email protected], Noah E. Horwitz, Brandon K. Rugg. Department of Chemistry, Northwestern University,
Evanston, Illinois, United
States
Controlling the spin dynamics of complex multi-spin molecular systems is a major goal in spintronics and quantum
information processing. Fast photo-initiated electron transfer within covalently-linked organic donor-acceptor molecules
having specific donoracceptor (D-A) distances and orientations results in formation of spin-entangled electron-hole pairs
(i.e. radical ion pairs, RPs) having well-defined initial spin configurations, while time-resolved electron paramagnetic
resonance (TREPR) techniques provide an important means of manipulating and controlling these coherent spin states.
Organic RPs display coherent spin motion for up to ~100 ns, which makes it possible that this coherence may provide the
basis for new quantum information processing strategies based on organic molecules.
INOR 25
Spin transport in organic materials: From single molecules to crystals
Stefano Sanvito, [email protected]. CRANN, Trinity College Dublin, Dublin, Ireland
The description of spin transport in organic devices poses a formidable challenge to theory and modeling. One has to
understand first how spins are injected from a ferromagnetic metal into an organic material and then a theory should be at
hand for describing spin transmission across the organic. These two aspects require a theory which is microscopic in
nature, but also scalable to large and complex organic crystals, namely they call for a fundamental multi-scale approach.
In this talk I will review how such a multi-scale approach can be constructed. Firstly I will look at the problem of spin
injection into an organic molecular layer. In particular I will correlated electronic structure theory results with spin- and
energy-resolved two photon photoemission data. Such comparison will reveal that electron-phonon coupling plays an
important role in determining the spin polarization of injected current. Secondly, I will present our multi-scale approach to
the calculation of the mobility and spin-relaxation length of organic materials. In particular I will show how a coarsegrained theory can be obtained by combining density functional theory with maximally localized Wannier functions, and
how this can be solved with Monte Carlo techniques. Results on rubrene and durene single crystals will be presented.
INOR 26
Probing spin-exciton and spin-charge interactions in open-shell organic semiconductors
Trisha L. Andrew, [email protected]. Chemistry, University of WisconsinMadison, Madison, Wisconsin, United
States
Stable organic radicals, net-neutral spin ½ molecules, are rarely invoked as useful materials, excluding isolated uses as
molecular magnets and organic batteries. This deficiency is partly because the organic materials community largely
ignored radical compounds and, instead, optimized closed-shell molecular and polymer materials for various device
applications. Another factor is the invisibility of organic radicals to the device engineering community, to whom radicals
are non-commercially-available specialty chemicals. Most importantly, the fundamental solid-state properties of these
materials remain uncharacterized, effectively precluding radicals as suitable materials for devices.
Our group is interested in synthesizing a tailored selection of radical-containing organic semiconductors, fabricating thin
films of these materials and characterizing the effects of the spin ½ moiety on charge and exciton transport in thin films. I
will discuss our group's efforts toward elucidating the structure-property relationships dictating the fundamentals of spin
transport though films of organic semiconductors and the interfacial phenomena determining spin injection into films of
organic semiconductors. Preliminary efforts at fabricating spintronic devices incorporating open-shell organic
semiconductors will also be discussed.
INOR 27
Evaluating magnetic properties of molecules with strong anisotropy based on electronic configuration and
geometry
Kim R. Dunbar4, [email protected], Maria Ballesteros 4, Stephen Hill2,
Dawid Pinkowicz1, Mohamed R. Saber5, Toby J. Woods3, Yuan-zhu Zhang4, Han-hua
Zhao4. (1) Jagiellonian University, Cracow, Poland (2) NHMFL and Florida State
University, Tallahassee, Florida, United States (3) Texas A&M University, College
Station, Texas, United States (4) Texas AM Univ, College Station, Texas, United States
(5) Chemistry, Texas AM University, College Station, Texas, United States
Molecular magnetism research incorporates fundamental concepts of coordination and organometallic chemistry and
merges them with physics with one of the highest profile current topics being molecules that exhibit bistability, known as
“Single Molecule Magnets” (SMMs). Recent strides in designing new generations of tiny magnets that retain their memory
effect at higher temperatures provide promising evidence that they may be useful for new generations of nanoscale
electronic devices and computers. The overarching goal of our research in this area is the use of discrete building units to
control molecular architecture and the resulting magnetic properties. The implementation of this strategy is helpful for
gleaning valuable information about how magnetic properties are affected by electronic as well as geometric structure as
well as weak and strong chemical interactions. This talk will cover various topics including combining specific metals of
the periodic table to enhance the magnetic properties. Experiments are being conducted to test the validity of several
independent theoretical studies that predict that specific metal combinations will lead to higher temperature magnets with
cyanide bridges. Experimental results are correlated with theory and augmented by the use of special techniques
involving neutrons and high frequency and high-field spectroscopies.
INOR 28
Magnetic ordering and conductivity in heavy atom and multiband radicals
Aaron Mailman2, Stephen M. Winter2, Joanne W. Wong2, Di Tian4, Craig M. Robertson3, Paul A. Dube5, Stephen R.
Julian4, Stephen Hill1, Richard T. Oakley2,
[email protected]. (1) NHMFL and Florida State University, Tallahassee, Florida, United States (2) Univ of Waterloo
Dept of Chem, Waterloo, Ontario, Canada (3)
Chemistry, University of Liverpool, Liverpool, United Kingdom (4) Physics, University of
Toronto, Toronto, Ontario, Canada (5) Physics, McMaster University, Hamilton, Ontario, Canada
We are interested in the design and characterization of radical-based materials with conductive and magnetic properties.
Historically, charge transport has been difficult to achieve in these materials because of the intrinsically high onsite
Coulomb barrier U to charge transfer; designing radicals with a sufficiently large bandwidth W to overcome U is a major
synthetic challenge. Our approach to this problem is to use highly delocalized, heavy atom (sulfur and selenium)
heterocyclic radicals, in which the combination of heavy (soft) heteroatoms and a highly delocalized spin distribution
lowers the value of U, while the enhanced intermolecular interactions afforded by the spatially extensive S/Se valence
orbitals increases W. While these materials remain Mott insulators at ambient pressure, their conductivity is significantly
improved over that found for conventional light atom radicals. The heavy heteroatom effect also amplifies magnetic
exchange interactions and magnetic anisotropy, and has allowed the rational design of organic ferromagnets with Tc > 10
K and Hc > 1000 Oe.
We have also discovered that both conductivity and magnetic properties in radicalbased materials can be improved by the
use of multiband systems, that is, radicals which possess low lying π-acceptor levels, or essentially a quasi-degenerate
SOMO. In the solid state, these systems enjoy an intrinsically lower U, and ferromagnetic exchange interactions are also
favored. In this presentation the structures, magnetic and charge transport properties of key examples of heavy atom and
multiband radicals, at ambient and elevated pressures, will be described.
INOR 29
Spin-selective charge recombination in complexes of CdS quantum dots and organic hole acceptors
David J. Weinberg1, [email protected], Scott M. Dyar1,3, Zane Khademi1, Michal
Malicki1, Seth R. Marder2, Michael R. Wasielewski1,3, Emily A. Weiss1,3. (1) Chemistry,
Northwestern University, Evanston, Illinois, United States (2) Georgia Inst of Technology, Atlanta, Georgia, United States
(3) Argonne-Northwestern Solar Energy
Research (ANSER) Center, Northwestern University, Evanston, Illinois, United States
This paper describes the mechanisms of charge recombination on both the nanosecond and microsecond timescales in a
donor-acceptor system comprising thiol-modified bis(diarylamino)4,4’-biphenyl (TPD) molecules attached to a CdS
quantum dot (QD) via the thiolate linker. Transient absorption measurements, in conjunction with EPR and magnetic field
effect studies, demonstrate that recombination on the nanosecond timescale is mediated by radical pair intersystem
crossing (RP-ISC), as evidenced by the observation of a spin correlated radical ion pair, the formation of the localized
3*TPD state upon charge recombination, and the sensitivity of the yield of 3*TPD to an applied magnetic field. These
experiments show that the radical spins of the donor-acceptor system have weak magnetic exchange coupling (|2J|<10
mT), and that the electron donated to the QD is trapped in a surface state rather than delocalized within the QD lattice.
The microsecond-timescale recombination is probably gated by diffusion of the trapped electron among QD surface
states. This study demonstrates that magnetooptical studies are useful for characterizing the charge-separated states of
molecule-QD hybrid systems, despite the heterogeneity in the donor-acceptor geometry and the chemical environment of
the radical spins that is inherent to these systems.
INOR 30
Base metal catalysis for hydrocarbon manipulation
Paul J. Chirik, [email protected]. Dept of Chem, Princeton University, Princeton, New Jersey, United States
The development of vast shale gas resources has resulted in an overabundance of ethylene and ethylene-derived
products such as linear alpha olefins. New reaction chemistry is needed to fully exploit these hydrocarbon building blocks.
My lecture will focus on the application of iron and cobalt catalysts that by virtue of their tailored electronic structures
promote new reactivity with these important molecules. Specifically advances in the development of intra- and
intermolecular [2+2] cycloadditions as well as methods for C-H functionalization will be highlighted. The mechanistic
pathways that govern the observed reactivity will also be discussed.
INOR 31
Tandem catalytic hydrogenation of carbon dioxide to methanol
Melanie S. Sanford, [email protected]. Chemistry, University of Michigan, Ann Arbor, Michigan, United States
This presentation will highlight our recent progress in the development of tandem sequences of catalysts for the
hydrogenation of CO2 to methanol. Catalytic processes that operate under acidic conditions (via ethyl formate as an
intermediate) as well as under basic conditions (via dialkyl carbamates and dialkylformamides as intermediates) will be
described. In addition, mechanistic features of the catalysts will be discussed in detail.
INOR 32
Functionalization of C–H bonds by iodate and chloride: Mechanistic studies
T B. Gunnoe1, [email protected], John T. Groves2, George C. Fortman1,5, Nicholas C. Boaz2, Steven E. Kalman1, Roy
A. Periana3, Michael M. Konnick4. (1) University of Virginia, Charlottesville, Virginia, United States (2) Princeton Univ,
Princeton, New
Jersey, United States (3) Chemistry, The Scripps Research Institute, Jupiter, Florida,
United States (4) The Scripps Research Institute, Jupiter, Florida, United States (5) Arkema, Philadelphia, Pennsylvania,
United States
Heating iodate or periodate with chloride in protic media (e.g., trifluoroacetic acid or acetic acid) with light alkanes results
in the formation of alkyl esters as the major product. Using this method, methane, ethane and propane can be
functionalized with conversions up to 30% and selectivity for mono-functionalized product that is generally > 80%. The
incorporation of chloride is essential to the success of the transformations. The transformations are effective over a broad
range of temperatures (100 - 235 ºC) and pressures (240-6900 kPa) in non-superacidic media. The presentation will focus
on mechanistic studies that shed light on the active reagents that are formed from iodine oxide, chloride and acidic solvent
at elevated temperature.
INOR 33
Amazing nonheme high-valent iron-oxo reactivity landscape
Lawrence Que, [email protected]. Univ of Minnesota, Minneapolis, Minnesota, United
States
Biological oxidation reactions are often catalyzed by metalloenzymes via high-valent iron centers generated by dioxygen
activation. Key nonheme iron examples are the mononuclear oxoiron(IV) oxidants associated with TauD and related
oxygenases and the FeIV2O2 diamond core found for intermediate Q of soluble methane
monooxygenase. Oxoiron(V) species may also be involved in the mechanisms of some dioxygenases. Our efforts have
focused on generating synthetic analogs of such reactive species; low temperatures are used to extend their lifetimes and
allow their spectroscopic characterization. Appropriate ligand design is required to enhance the prospects of success in
generating the target high-valent iron-oxo unit. The synthesis, structures, and reactivity of these novel intermediates will
be discussed.
INOR 34
Concerted multiple-site proton-coupled electron transfer (PCET): Effects of separating the proton and electron
James M. Mayer3, [email protected], Miriam A. Bowring4, Virginia Manner1,
Jeffrey J. Warren7, Jessica Wittman5, Liam R. Bradshaw4, Daniel R. Gamelin2, Wesley
D. Morris6, Todd F. Markle3. (1) MS C920, Los Alamos National Laboratory, Los
Alamos, New Mexico, United States (2) Chem Dept, Univ Washington, Seattle,
Washington, United States (3) Yale University, New Haven, Connecticut, United States
(4) University of Washington, Seattle, Washington, United States (7) Simon Fraser University, Burnaby, British Columbia,
Canada
The concerted transfer of one electron and one proton is a fundamental chemical process. Often the e– and H+ transfer
together from one reagent to another, which is typically called hydrogen atom transfer, but it can also occur with
substantial separation of the e– and H+. This presentation will describe a number of different types of such multiple-site
PCET processes. For example, the ruthenium-bipyridine complexes with a distant carboxylic acid shown here (n = 0 or 1)
react readily with reagents such as the nitroxyl radical TEMPO despite the up to 11 Å separation of the proton from the
ruthenium center. The dependence of the rate constants on the e–/H+ coupling will be discussed, including in related
termolecular reactions. A unimolecular photo-induced system has also been developed, coupling a phenol-base to a
photoexcitable anthracene as shown below. This system allows studies of very rapid PCET process from high to very low
temperatures. The results will be interpreted using versions of Marcus theory to give insight into this important class of
reactions.
INOR 35
Harry Gray as a young investigator: Paradigms lost, found, and going up in gas Richard Eisenberg,
[email protected]. Dept of Chem, Univ of Rochester, Rochester, New York, United States
Beginning slightly more than a half century ago, metal complexes with unsaturated dithiolate chelate ligands synthesized
and studied. The complexes were notable for facile one electron transfers, intense solution colors and unusual magnetic
properties that defied conventional oxidation state descriptions. The bis complexes were in general square planar,
including the first examples of this geometry for paramagnetic complexes and different formal d n configurations, whereas
a number of neutral and monoanionic tris complexes were found to have trigonal prismatic coordination. A summary of
this early work will be followed with a discussion of the light-driven generation of hydrogen from water which is the
reductive side of the water splitting reaction. Recent efforts on the use of 3d metal dithiolene complexes as catalysts for
light-driven hydrogen generation will be described. In these complexes, the sites for electron addition are of mixed metal
and ligand origin, and the sulfur donor atoms can also serve as sites for protonation in the process of assembling the two
electrons and two protons into H2.
INOR 36
Gray nation: Out of this world
Morgan L. Cable1, [email protected], James P. Kirby3, Adrian Ponce4, Amanda M. Stockton4, Maria F. Mora4,
Peter Willis4, Tuan H. Vu4, Patricia M.
Beauchamp4, Harry B. Gray2. (1) Instrument Systems Implementation and Concepts
Section, NASA Jet Propulsion Laboratory, California Institute of Technology, Montrose,
California, United States (2) California Inst of Tech, Pasadena, California, United States
(3) Planetary Science Institute, Tucson, Arizona, United States (4) NASA Jet Propulsion Laboratory, Pasadena, California,
United States
The Gray Nation’s foray into planetary science began with an investigation of bacterial spores, the most robust form of life
and the most likely to survive an interplanetary journey. We improved a rapid technique to detect bacterial spores using
lanthanide luminescence, increasing sensitivity by three orders of magnitude. This could be used to detect life in extreme
environments such as Mars or Europa, or to ensure proper spacecraft sterilization before launch. Following this work,
exploration of life detection methods led to development of ultrasensitive protocols for biomolecules, including short- and
long-chain fatty acids. These microfluidics-based techniques are ideal for in situ planetary missions where mass, power
and volume are severely limited. We have also applied these protocols to unraveling the complex organics formed when
simulating the atmospheric chemistry of Titan, a moon of Saturn. Further work involving the lakes of Titan has revealed
that benzene and ethane form a unique inclusion complex, which may indicate surface processes capable of selectively
sequestering and storing ethane in surface materials. These explorations into planetary science, with a strong foundation
in organic and inorganic chemistry, have laid the groundwork for the next generation of sensitive, selective instruments
with a focus on life detection.
INOR 37
Molecular systems for photocatalytic hydrogen oxidation
Michael D. Hopkins, [email protected], Hunter B. Vibbert, Mark Westwood, Nathan T. La Porte. Department of
Chemistry, The University of Chicago, Chicago, Illinois, United States
Hydrogen is a renewable source of reducing equivalents that could replace conventional organic sacrificial donors in
artificial photosynthetic systems, fulfilling a prerequisite for the storage of solar energy. The development of transitionmetal chromophore/catalyst complexes and pairings that drive hydrogen oxidation with light, and are suitable components
for artificial photosynthetic systems, will be described. The
chromophore/catalyst complexes are d2-configured tungsten–alkylidyne compounds of the type W(CR)L4X (R = aryl, L/X =
neutral/anionic ligand). These luminophores are powerful photochemical reductants, with excited-state oxidation potentials
of < –3 V vs FeCp20/+ (near the one-electron reduction potential of CO2). Upon oxidation, they react sequentially with H2
and a Brønsted base to regenerate the d2 chromophore. The design parameters that allow control over redox potentials,
excited-state energies, and emission lifetimes will be described. Separately, photocatalytic hydrogen oxidation has been
accomplished through redox sensitization of DuBois-type Ni(PR2NR2)2n+ catalysts by chromophores including Ru(bpy) 32+
and ZnTPP. These systems proceed via reductive quenching of the chromophore by Ni(P R2NR2)2+, with transient
Ni(PR2NR2)22+ being trapped irreversibly by H2 prior to back electron transfer. A mechanism will be described in which
turnover is achieved without an external sacrificial oxidant. The integration of these chromophore/catalyst pairs with CO 2
reduction catalysts will be discussed.
INOR 38
Artificial hydrogenases for solar hydrogen production
Kara L. Bren, [email protected], Banu Kandemir, Jesse G. Kleingardner,
Lenore Kubie. Chem Dept, Univ of Rochester, Rochester, New York, United States
The development of hydrogen (H2) as an environmentally friendly fuel requires catalysts capable of efficient proton
reduction. Ideally, these catalysts would be active in water near neutral pH, insensitive to oxygen, and insensitive to
added ions and impurities. Biomolecules are attractive scaffolds to use for engineering artificial hydrogenases because of
their compatibility with aqueous media and the wide range of derivatives that can be accessed using site-directed
mutagenesis and protein chemistry. In this presentation, progress toward the development of biomolecular artificial
hydrogenases will be presented. One class contains cobalt porphyrin active sites that display high activity and stability at
neutral pH in the presence of air. Turnover numbers of over 100,000 have been achieved under electrocatalytic
conditions. To demonstrate successful solar energy storage, a zinc porphyrin-based photosensitizer has been paired with
cobalt porphyrin-based catalysts to yield hundreds of turnovers. The catalysts also display high activity in seawater, the
world's most abundant proton source. Ongoing refinements are toward further increasing stability and lowering
overpotential by engineering protein structure. A new class of artificial hydrogenases based on metallopeptides also will
be presented.
INOR 39
Designing metalloproteins with tunable redox potentials and reorganization energies for efficient long-range
electron transfer
Yi Lu1,3, [email protected], Nicholas M. Marshall1, Parisa Hosseinzadeh3, Ole Farver4,
Scot E. Wherland2, Israel Pecht5. (1) Dept of Chemistry, Univ of Illinois, Urbana, Illinois,
United States (2) Washington State Univ, Pullman, Washington, United States (3)
Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana,
Illinois, United States (4) Department of Analytical and Bioinorganic Chemistry,
University of Copenhagen, Copenhagen, Denmark (5) Department of Immunology,
Weizmann Institute of Science, Rehovot, Israel
With the global energy crisis, there are growing interests in making redox reagents for applications ranging from fuel cells
to solar energy transfer. A critical barrier to the success is the design of such reagents with tunable redox potentials (E°)
and reorganization energies (λ) for efficient long-range electron transfer (ET). A longstanding issue is how the E° can be
fine-tuned over a broad range with little change to the metal-binding site or other ET properties. To meet the challenge,
we have demonstrated tuning E° of a single cupredoxin, azurin, across a 700 mV range, which is broader than that of
native cupredoxins (~500 mV), through manipulation of secondary coordination sphere interactions such as
hydrophobicity, hydrogen-bonding and peptide bond oxygen interactions.1 We have also shown that these features are
additive, making redox potential tuning of azurin predictable.
Furthermore, lower λ in the ET process generally increase ET rate constants and efficiency. However, rational design of
ET centers to lower the λ has rarely been demonstrated. Such a task is particularly challenging for ET proteins like the
azurin, which have been shown to possess very low λ in comparison to the majority of other proteins. We have reported
an analysis of the intramolecular ET from pulse radiolytically produced disulfide radicals to Cu(II) in the above rationally
designed azurin mutants, and showed that the λ of ET is indeed smaller than that of native azurin, interpreted as being
due to an increased flexibility of the copper site. 2
Finally, we have also provided experimental support for the Marcus “inverted region” behavior in a protein only system
and found it to be related to the lower λ. It has been hypothesized that the dramatically different forward and backward ET
rates in the photosynthetic center is due to the lower λ and large activation barrier for the reverse processes that result
from the inverted region. Therefore, our report of successful lowering of λ, achieving the Marcus inverted region and
establishing the relationship between these two features furthers the understanding of ET reactivity in proteins and may
facilitate de novo design of ET centers for applications such as advanced energy conversions.
1. N. M. Marshall et al. Nature 462, 113-116 (2009).
2. O. Farver et al. Proc. Natl. Acad. Sci. USA 110, 10536-10540 (2013).
INOR 40
Time-resolved spectroscopic studies of electron and proton transfer in biologically relevant systems
Maraia E. Ener4,1, [email protected], Harry B. Gray2, Thomas G. Spiro3. (1) Chemistry, California Inst of Technology,
Pasadena, California, United States (2)
California Inst of Tech, Pasadena, California, United States (3) Chemistry, Univ. of
Washington, Seattle, Washington, United States (4) Chemistry, University of Washington, Seattle, Washington, United
States
Biological systems are elegantly tuned to drive chemical reactions, often by controlling movements of the smallest
chemical reactants: the electron and the proton. In carefully designed systems, electron and/or proton transfer can be
photo-triggered, allowing the reaction process to be spectroscopically probed on rapid (sub-millisecond) and ultrafast
(sub-picosecond) timescales. Time-resolved electronic absorption and vibrational studies of electron and proton transfer
in biological and small molecule systems will be discussed.
INOR 41
Understanding plasticity in molecular recognition
Deborah S. Wuttke, [email protected], Thayne H. Dickey, Marissa
McKercher. Chemistry and Biochemistry, University of Colorado, Boulder, Colorado,
United States
Structural plasticity underlies the ability of many proteins to bind partners with a continuum of specificity. This ability to
bind a range of ligands is utilized widely in biology. For example, it allows DNA-binding proteins to bind several of
biologically important sequences and also permits peptide-binding domains to act as hubs, interacting with many binding
partners to stimulate an array of signaling networks.
We have investigated the structural and dynamic origins of plasticity in ligand binding systems that share the ability to bind
a flexible ligand. Telomere end-binding proteins specifically bind the conserved G-rich single-stranded overhang present
at all eukaryotic chromosome ends. From this vantage point, they regulate the key functions of the telomere. Pot1 is the
single-stranded DNA-binding protein important for genome stability and telomere length regulation, functions that rely on
its ssDNA-binding ability. Structures of Pot1 bound to various ssDNA sequences reveal a unique plasticity at the DNAbinding interface. This structural plasticity explains the ability of Pot1 to accommodate the natural heterogeneity in
telomeric sequence. Furthermore, these mechanisms of accommodation allow for a high-affinity/low-specificity binding
mode that may be more widely used by other sequence nonspecific ssDNA and ssRNA-binding proteins.
SH2 domains, including the C-terminal SH2 domain of phospholipase C-g1 (PLCg1), may likewise utilize plasticity to
recognize diverse peptide ligands. Array experiments found that this SH2 domain exhibits a strong preference for small,
aliphatic, hydrophobic amino acids following the phosphotyrosine of a peptide ligand. This observation is supported by a
hydrophobic binding groove apparent in high-resolution structures of the domain in complex with canonical ligands.
However, even with this structural data, it is difficult to predict the binding specificity of the PLCg1-SH2 domain based on
knowledge of the binding pocket alone. Unexpected physiological peptides, containing charged residues or other
deviations next to the phosphotyrosine, interact with PLCg1-SH2. To investigate the structural extent of this biologically
defined plasticity, several protein/peptide complexes spanning a range of chemical properties within the ligand were
characterized using NMR and x-ray crystallography. Together, these systems illustrate how structural malleable at an
interface leads to unexpected recognition features. INOR 42
Bioinorganic chemistry in a gray area
Faik A. Tezcan, [email protected]. MC0356, UCSD Chemistry, La Jolla, California,
United States
This presentation will focus on my nearly 20-year long journey in bioinorganic chemistry, which started with Harry Gray
and is still being inspired by him - one way or another.
INOR 43
Sunlight-driven hydrogen formation by membrane-supported photoelectrochemical water splitting
Nathan S. Lewis, [email protected]. Caltech, Pasadena, California, United States
We are developing an artificial photosynthetic system that will utilize sunlight and water as the inputs and produce
hydrogen and oxygen as the outputs. We are taking a modular, parallel development approach in which three distinct
primary components-the photoanode, the photocathode, and the product-separating but ion-conducting membrane-are
fabricated and optimized separately before assembly into a complete water-splitting system. The design principles
incorporate two separate, photosensitive semiconductor/liquid junctions that will collectively generate the 1.7-1.9 V at
open circuit necessary to support both the oxidation of H2O (or OH-) and the reduction of H+ (or H2O). The photoanode
and photocathode will consist of rod-like semiconductor components, with attached heterogeneous multi-electron transfer
catalysts, which are needed to drive the oxidation or reduction reactions at low overpotentials. The high aspect-ratio
semiconductor rod electrode architecture allows for the use of low cost, earth abundant materials without sacrificing
energy conversion efficiency due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the
high surface-area design of the rod-based semiconductor array electrode inherently lowers the flux of charge carriers over
the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent
density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. A
flexible composite polymer film will allow for electron and ion conduction between the photoanode and photocathode while
simultaneously preventing mixing of the gaseous products. Separate polymeric materials will be used to make electrical
contact between the anode and cathode, and also to provide structural support. Interspersed patches of an ion conducting
polymer will maintain charge balance between the two half-cells.
INOR 44
Challenges in photoelectrochemical water splitting materials
John A. Turner, [email protected]. National Renewable Energy Laboratory, Golden, Colorado, United States
Forty years after the first reported photoelectrochemical (PEC) water splitting experiment, commercial hydrogen
production from PEC is still a dream.
INOR 45
Enabling solar fuels technology by high throughput discovery of earth abundant oxygen evolution reaction
catalysts
Joel Haber1, [email protected], Dan Guevarra1, Ryan Jones1, Aniketa Shinde1, Natalie Becerra1, Chengxiang
Xiang1, Slobodan Mitrovic1, Suho Jung1, Christian
Kisielowski2, Junko Yano2, Jian Jin2, John Gregoire1. (1) Joint center for Artificial Photosynthesis, California Institute of
Technology, Pasadena, California, United States
(2) Joint center for Artificial Photosynthesis, Lawrence Berkeley National Lab, Berkeley, California, United States
The High Throughput Experimentation (HTE) project of the Joint Center for Artificial Photosynthesis performs accelerated
discovery of new earth-abundant photoabsorbers and electrocatalysts. We will describe several new screening
instruments for high throughput (photo-)electrochemical measurements and summarize the discovery pipelines. This
approach will be illustrated using the high throughput discovery, followon verification, and device implementation of a new
quaternary metal oxide catalyst. Discovering improved electrocatalysts for the oxygen evolution reaction (OER) is of great
importance for efficient solar fuels generation, regenerative fuel cells, and recharging metal air batteries. We report a new
Ce-rich family of active catalysts composed of earth abundant elements, which was discovered using high-throughput
methods to produce 5456 discrete compositions in the (Ni-Fe-Co-Ce)Ox composition space. The activity and stability of
this new OER catalyst was verified by re-synthesis and extensive electrochemical testing of samples in a standard format
in 1.0 M NaOH. Characterization of selected compositions by XRD, XPS, SEM, TEM, EDS, XRF mapping, and EXAFS
both as-synthesized and after electrochemical testing, reveal the importance of nanostructure to the observed
electrochemical performance. The discovery of additional electrocatalysts by expansion of the composition space
investigated and of new composition spaces tested for OER activity and stability under acidic conditions will be reported.
INOR 46
Tin nitride spinel semiconductor for photoelectrochemical water oxidation
Christopher Caskey1,5, Jason A. Seabold5, Vladan Stevanovic6, David S. Ginley3, Nathan Neal7, Ryan M. Richards2,
Stephan Lany7, Andriy Zakutayev4, [email protected]. (1) Colorado School of Mines, Golden, Colorado, United
States (2) Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado,
United States (3) NREL, Lakewood, Colorado, United States (5) National Renewable
Energy Laboratory, Golden, Colorado, United States
The grand materials chemistry challenge for photoelectrochemical hydrogen production is development of new
semiconductor anodes for water oxidation side of the water splitting reaction. Currently, the most widely studied
candidates are metal oxides (e.g. Fe2O3, TiO2, BiVO4) and III-V compound semiconductors (e.g. GaP, InGaAs). Despite
the significant progress made in recent years towards improvement of charge transport of the former and the increasing
the operational stability of the latter, the search for alternative materials options is still on.
Metal nitrides constitute an interesting class of compounds for this application because of stability similar to metal oxides
and charge transport properties similar to compounds semiconductors. In particular tin (IV) nitride, Sn3N4, is a
semiconductor composed of Earth-abundant elements, making it a potential candidate for very larger scale hydrogen
production applications. Here we report on synthesis and semiconducting properties of Sn 3N4 for the hydrogen production,
as studied by thin-film experiments and firstprinciples theory.
Polycrystalline thin films of Sn3N4 with spinel crystal structure were synthesized by reactive sputtering of Sn target in
atomic nitrogen atmosphere as reported earlier for Cu 3N [1]. The optical absorption onset was determined at 1.6 eV in
good agreement with 1.5 eV calculated from GW theory. The electron concentration was found to be 10 18 cm-3 with
mobility of ~1 cm 2/Vs. Most importantly, calculations and experiments agree that Sn3N4 band gap straddled the water
oxidation and reduction potentials.
The measured photocurrent in the polycrystalline Sn3N4 thin films was limited by the 50100 nm minority carrier (holes)
diffusion length, on the order of the grain sizes, calling for further improvement in thin film growth process to achieve
larger grains. Another contribution to this short minority carrier diffusion length is the calculated large hole effective mass
(12.9me), which contrasts with very small electron effective mass (0.18m e). Theoretical calculations suggest that alloying
Sn3N4 with other group-IV nitrides can improve hole effective masses by both changing the electronic structure (band
engineering) and crystal structure (polymorphism). [1] Mater. Horiz., 1, 424 (2014)
INOR 47
Electrolysis of urea for the sustainable production of hydrogen
Gerardine Botte, [email protected]. Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio, United States
Typically, water is the source for the electrochemical production of hydrogen, using alkaline or proton exchange
membrane electrolysis. However, there are limitations with water electrolysis such as high-energy consumption, high
capital costs, and high purity of the source (water). To circumvent these problems, the Center for Electrochemical
Engineering Research (CEER) at Ohio University has been working in the development of novel, simple, suitable, and
environmentally friendly electrochemical technologies to produce hydrogen from nonconventional sources such as urea.
The electrolysis of urea for hydrogen production takes place in alkaline media. In the process, the electrochemical
oxidation of urea to nitrogen and carbon dioxide takes place at the anode of the electrolytic cell in nickel-based electrodes,
while hydrogen evolves at the cathodic compartment [1,2]. The process, with a theoretical cell voltage of 0.37 V at
standard conditions, is thermodynamically more favorable than water electrolysis. Because of its low energy consumption
and the use of inexpensive catalysts, the technology finds applications for the production of hydrogen on demand
requiring only the storage of urea.
In addition to direct production of hydrogen on demand, urea-rich wastewaters can be remediated via urea electrolysis to
prevent toxic ammonia emissions and nitrate contamination that currently results from leaving these waters untreated.
In this talk, Dr. Botte will present a summary of the technology including catalysts, oxidation rates, and progress on
understanding of the reaction mechanism.
[1]
G. G. Botte. Electrolytic Cells and Methods for the Production of Ammonia and Hydrogen. US Patent 8,303,781
2012.
[2]
B. K. Boggs, R. L. King, G. G. Botte. Urea Electrolysis: Direct Hydrogen Production from Urine. Chem. Commun.
2009; 32: 4859-4861.
INOR 48
Sulfur Sulfur thermochemical hydrogen production cycle: A new thermochemical cycle employing only earth
abundant elements
Nicholas AuYeung3, Kevin Caple3, Peter Kreider2, Alexandre F. Yokochi1, [email protected]. (2) School of
Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, Oregon, United States (3)
School of
Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon, United States
Of the 52.6 million tons of hydrogen consumed worldwide in 2010 (~60% for ammonia production, ~30% for Oil refining,
and ~10% for MeOH production), nearly all was produced by fossil hydrocarbon steam reforming. Transition to a “CO 2
lean” infrastructure requires development of options for the production of hydrogen from noncarbon based energy
resources. Thermochemical cycles are an option of particular interest, as these have potential high thermal exergetic
efficiencies.1 From the several thermochemical cycles, those employing only fluids, such as the Sulfur-Iodine (SI) cycle,
shown below in Eqns. SI1-SI3, are percieved as simpler to implement, and therefore preferred.2
SO2 + I2 + H2O → H2SO4 + 2HI (SI1)
2HI → H2 + I2 (SI2)
H2SO4 → SO2 + ½O2 + H2O (SI3)
Unfortunately, the requirement for extremely large amounts of the relatively low earth abundance element Iodine for
implementation of an SI thermochemical hydrogen plant suggests that this would consume the world’s output of iodine for
one year (per plant). With support from the NSF we have been examining the feasibility of an all thermal cycle employing
Ionic Liquids as a reaction medium for the low temperature reactions, and which employs Iodine in a catalytic role. In this
system, all circulating fluids are Sulfur based species, and compose a cycle we have named the Sulfur-Sulfur (SS) cycle,
given by Eqns. SS1 through SS4.
SO2 + I2 + H2O → H2SO4 + 2HI (SS1)
H2SO4 + 8HI → H2S + 4I2 + 4H2O (SS2)
H2S + 2H2O → 3H2 + SO2 (SS3)
H2SO4 → SO2 + ½O2 + H2O (SS4)
We have demonstrated the unique parts of the SS cycle represented by Eqns. SS1SS3, with the thermal cracking of
H2SO4 (Eqn SS4) identical to that in the SI cycle and previously demonstrated by others. The SS cycle also avoids
materials compatibility issues in the SI cycle, in particular with the extremely corrosive aqueous HI solutions, and has a
high exergetic efficiency which we estimate at ~60% (though practical implementations will be necessarily lower).
In this contribution we will present a summary of our work on the development of the SS cycle.
1
– Steinfeld, A. “Solar thermochemical production of hydrogen––a review” Solar Energy 2005, 78, 603–615
- Besenbruch, G. “General Atomic sulfur iodine thermochemical water-splitting process.” Proceedings of the
American Chemical Society, Div. Pet. Chem. 1982, 27, 4853.
2
INOR 49
Lithium metalorganic complex used to clean hydrogen sulfide for hydrogen production and/or storage
Xuemin Li1, [email protected], Rachel Morrish3, Colin A. Wolden3, Yongan Yang2, [email protected]. (1) Chemistry,
Colorado School of Mines, Golden, Colorado, United States (2) Dept Chem Geochem Coolbaugh Hall 120B, Colorado
School of
Mines, Golden, Colorado, United States (3) Colorado School of Mines, Golden, Colorado, United States
Hydrogen sulfide (H2S) is a major pollutant created by many natural sources and industrial activities, at the scale of
millions of tons per year. It is extremely hazardous to human health, highly corrosive to equipment, and poisonous to
many catalysts. The currently prevailing industrial H2S abatement technologies typically convert H2S to S and H2O, two
low-value chemicals. Consequently, these techniques are economically non-sustainable, because S production has
exceeded its demand and tremendous amounts of H2 exiting in the form of H2S from the oil refinery industry lose the
chance to be recycled. Thus, the Holy Grail of H2S treatment would be a process that liberates H2 (in the gas form or
stored in high-value chemicals) while producing valuable Scontaining products. Such a process must be scalable and
ideally capable of being executed at near ambient conditions without the need for significant energy input. Although a
variety of approaches have been examined toward the goal, they all essentially operate a variant of equation H 2S--> H2 +
S(s), which is thermodynamically unfavorable and significantly endothermic. Regardless what form of energy is used to
execute this reaction, all such techniques face massive challenges with respect to both scale, cost and/or conversion,
making them unviable for practical implementation. Our presentation will demonstrate a new approach that alters
thermodynamics to work in our favor by reacting H2S with a lithium metalorganic complex. The reaction is supposed to be
2Li + H2S -->Li2S + H2, Delta_Gmo = - 407 kJ/mol. Surprisingly and interestingly, the observed products are LiH and S,
which indicates the actual reaction to be 2Li + H2S -->2LiH + S, Delta_Gmo = - 103 kJ/mol. This reaction is also simple,
spontaneous, complete, irreversible, and can be conducted at ambient conditions. A further heating treatment completes
the reaction to produce Li2S and H2. This actual two-step process, different from our expectation to directly release H 2,
provides an alternative strategy of recovering hydrogen by storing it temporarily in the form of LiH, which holds the highest
volumetric and gravimetric density among all solid-state hydrogen storage materials. The presentation will focus on
understanding the intriguing chemistry of this process.
INOR 50
Tetracarbene iron(IV) intermediates for catalytic aziridination
Steven A. Cramer2, Raul Hernandez Sanchez1, Preeti P. Chandrachud2, Desirae F.
Brakhage2, David M. Jenkins2, [email protected]. (1) Chemistry and Chemical Biology, Harvard University, Cambridge,
Massachusetts, United States (2) Chemistry, University of Tennessee, Knoxville, Tennessee, United States
The direct synthesis of aziridines from alkenes and nitrene sources (C 2+N1) with the correct functionality on the nitrogen
atom has remained an elusive goal in synthetic chemistry. Our group is expanding the scope of catalytic aziridination to
include electron donating aryl azides and aliphatic alkenes through the use of novel tetracarbene iron catalysts. To
improve the design of next generation catalysts, a detailed understanding of the mechanism and intermediates is vital.
The reaction of organic azides with tetracarbene iron(II) complexes leads to high valent iron(IV) intermediates, including
metallotetrazenes. Both first and second generation tetracarbene ligands support these iron(IV) complexes. The structural
and spectroscopic properties of these unusual iron(IV) complexes will be discussed as well as their group transfer
reactions.
INOR 51
Synthesis and reactions of (C2F5PCP)Ru(cod)H.
Bhusan Thapaliya, [email protected], Gabriel A. Venegas, Navamoney
Arulsamy, Dean M. Roddick. Univ of Wyoming, Laramie, Wyoming, United States
Treatment of (h4-C8H12)(h6-C8H10)Ru with 1,3-C6H4[(CH2)P(C2F5)2]2 under H2 in THF followed by addition of L (L = cod or
nbd) yields the ruthenium acceptor PCP complexes
{1,3-C6H3[(CH2)P(C2F5)2]2}(Ru)(L)H. A survey of catalytic hydrocarbon dehydrogenation activities will be presented.
INOR 52
Synthesis and metal coordination chemistry of
(Rf)
2(PNP)
and (Rf)2(PONOP) (Rf =
CF3, C2F5) chelates
Philip Miller1, [email protected], Dean M. Roddick1. (1) Chemistrt, University of
Wyoming, Laramie, Wyoming, United States (1) Univ of Wyoming, Laramie, Wyoming,
United States
The synthesis of new tridentate donor/acceptor PNP pincer ligand 1,3-NC5H3(CH2P(Rf) and 1,3-NC5H3(OP(Rf) (Rf = CF3,
C2F5) are reported. Addition of these ligands to Ir(I) and Ru(II) complex precursors and subsequent reaction chemistry will
be discussed.
INOR 53
Experimental and computational investigation of Csp3-N, Csp3-F, and Csp3- Csp2 reductive elimination from
model palladium (IV) complexes
Ian M. Pendleton1, [email protected], Paul M. Zimmerman2, Melanie S. Sanford1,
Monica Helvia Perez-Temprano3. (1) Chemistry, University of Michigan, Ypsilanti,
Michigan, United States (2) University of Michigan, Ann Arbor, Michigan, United States
(3) Depatment of Chemistry, University of Michigan, Ann Arbor, Michigan, United States Full mechanistic evaluation of new
reactions requires significant time and resources. One potential way of reducing the chemical footprint of mechanistic
discovery is through the development of autonomous reaction finding (ARF) through quantum chemistry. Recently, our
group reported the development of a program designed for rapid quantum mechanical investigation of reaction pathways.
We then set out to test this program via a tandem experimental and computational investigation of Csp 3-N, Csp3-F, and
Csp3- Csp2 reductive elimination from model palladium (IV) complexes. Through analysis of more than 1500 transition states
we evaluated the relevant portions of the potential energy surface of this system. Using these data we successfully predicted
the most effective substrates for Csp3-N reductive elimination. Experimental kinetics data indicated that the predicted ΔGǂ
were in close correlation with experimentally measured values. Furthermore, we were able to use the initial reaction
information generated by the ARF program to put forth a plausible mechanism for the remaining Csp 3-F and Csp3- Csp2
reductive elimination process and predict qualitatively correct product distributions for various substrates. The predicted
products and ratios were confirmed experimentally demonstrating the plausibility of computationally driven development of
new main group and group 10 reactions.
INOR 54
Investigation of acid and base co-catalysts for the palladium(II) and platinum(II) catalyzed hydroarylation of
acetylene
Christine Hahn, [email protected], Mostafa Manjahi. Chemistry, Texas AM
University Kingsville, Kingsville, Texas, United States
The dicationic ethylene complexes [M(PNP)(C2H4)]X2 (M = Pd, Pt; X = BF4, SbF6, PNP = 2,6bis(diphenylphosphinomethyl)pyridine) were found to be efficient catalysts for the hydroarylation of acetylene in the
absence of any co-catalyst at room temperature. However, the reaction rate can be substantially increased in the
presence of either few equivalents of acid HX or of water. While the acid has an impact on the M-C protonolysis step, a
base (water) promotes the proton transfer. Details of the individual reaction steps of the Friedel-Crafts type mechanism
have been studied and the advantages and disadvantages for the use of either acid or base co-catalysts for the alkyne
hydroarylation are discussed.
INOR 55
Synthesis and metal (M = Ir, Ru) coordination chemistry of (tBu)(Rf)(PCP) (Rf = CF3, C2F5) chelates
Suman Debnath1, [email protected], Dean M. Roddick2. (1) Chemistry, University of Wyoming, Laramie, Wyoming,
United States (2) Univ of Wyoming, Laramie, Wyoming, United States
The synthesis of the new hybrid donor/acceptor PCP pincer ligand 1,3C6H4(CH2P(tBu)(Rf) (Rf = CF3, C2F5) is reported. Synthesis of Ir(III), Ir(I), and Ru(II) complexes and a survey of catalytic
hydrocarbon dehydrogenation will be presented.
INOR 56
Influence of Lewis acids on migratory insertion: Applications to C-C bond formations
Graham Dobereiner, [email protected]. Temple University, Philadelphia,
Pennsylvania, United States
The kinetic and thermodynamic influence of Lewis acids on migratory insertion reactions has been repeatedly
demonstrated in stoichiometric cases, yet few examples have yet provided compelling examples of the benefit of Lewis
acid additives to catalytic reactions of CO. This study aims to examine the role of Lewis acids on Pd-catalyzed
carbonylation reactions.
INOR 57
Cross-coupling catalysis in water – a versatile approach
Jorg Eppinger, [email protected], Dinesh Sawant, Anna V.
Zernickel. KAUST Catalysis Center - PSE Division, King Abdullah University of Sci Tech, Thuwal, Saudi Arabia
Water is cheap, generally available, non-toxic and non-flammable. Hence, research on application of water as a benign
and sustainable alternative to organic solvents has become a highly active research field addressing upcoming
requirements in synthesis and catalysis. Chemically, water is a unique solvent as it combines high nucleophilicity with and
donor-strength with a large dielectric constant and excellent hydrogen-bonding ability as well as the intrinsic availability of
protons. While most of these properties commonly limit applications of aqueous reactions due to the low stability and
solubility of reactants as well as catalysts, we recently established cross-coupling protocols utilizing the high polarity of
water for straightforward product isolation by basic filtration since lipophilic coupling products separate from the aqueous
phase under optimized conditions. [1, 2, 3]
In this presentation we detail our studies on the influence of water as a solvent on palladium catalysed cross-coupling
reactions, which represent one of the most powerful tools in organic synthesis. We report new palladacyclic and amino
acid derived catalysts achieving high activities at room temperature at typical catalyst loadings of 0.02 mol-% in aqueous
Suzuki-Miyaura, Sonogashira and Tsuji-Trost cross-coupling reactions, the addition of arylboronic acids to aldehydes and
the borylation of aryl halides. Under certain conditions the combination of aqueous protocol and microwave heating only
requires 10-5 mol-% of palladium to achieve quantitative conversions in 15 min. The high activity achieved by our catalyst
motifs in water facilitates the application of cross-coupling reactions in combination with biocatalysis and biologic ligands.
Based on our aqueous organometallic cross-coupling protocols we are able to introduce sitedirected transformation on
proteins, which contain a suitable unnatural amino acid. Overall, our results show that water is a particularly versatile
solvent for palladium catalysed cross-coupling reactions.
INOR 58
Synthesis of silicon-germanium alloy nanoparticles for thermoelectric applications
Allon Hochbaum1,2, Trevor Cornell2, [email protected]. (1) Chemical Engineering and
Materials Science, University of California, Irvine, Irvine, California, United States (2)
Chemistry, University of California, Irvine, Irvine, California, United States
Approximately 90% of the world’s energy is produced from heat engines working near
40% efficiency. Annually, this results in the loss of 30 PWh of wasted heat for the 20 PWh of usable energy produced.
Thermoelectric materials, which convert heat directly into electrical energy, present a way to utilize this wasted heat.
Group IV elements are attractive as thermoelectric materials due to their nontoxicity and relative abundance. Silicon–
germanium alloys have been studied for their thermoelectric properties for decades. However, the high cost of germanium
and moderate efficiency has traditionally limited their usefulness. Recent studies have shown that incorporation of as little
as 5% germanium into silicon has been shown to greatly improve thermoelectric properties in bulk systems. However, the
successes seen in bulk alloying studies have not yet been translated to nanoscale materials. Nanoscaling of
thermoelectric materials provides greater flexibility for manipulating the parameters that govern a material’s thermoelectric
performance, such as band gap, electrical and thermal conductivity, and carrier concentration. Development of a colloidal
synthesis of Group IV-based materials could allow for the generation of tunable thermoelectric materials in a scalable
manner, from commercially available materials. Here, we present a solution-based bottom-up approach to the synthesis of
alloyed silicon-germanium nanoparticles in a noncoordinating solvent and illustrate the effect of compositional tuning on
the resulting products.
INOR 59
Energy transfer by demand in well-defined hybrid materials
Natalia B. Shustova, [email protected], Derek E. Williams, Ekaterina A.
Dolgopolova. Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, United
States
Efficient light-harvesting and energy conversion are research areas necessary to address the grown demand of energy
utilization. In the natural photosystem, the high efficiency of solar energy utilization is contingent on the ensemble
chromophore behavior. To mimic a well-defined chromophore arrangement achieved in nature, the molecular selfassembly process for effective design of artificial light-harvesting arrays should be utilized. Such control of the
chromophore order can be achieved in metalorganic frameworks, which possess a high degree of structural and chemical
tunability, imposing a very few restrictions on the chromophore of choice. We built a novel welldefined light-harvesting
material with a predesigned pathway for the energy transfer. The prepared system allowed us to control the excited state
decay pathways in the large light-harvesting array through alternation of incident light. Thus, our studies demonstrate a
novel concept missing in the natural photosystem and allow one to control the energy transfer through a photoswitchable
linker in multidimensional lightharvesting matrices by external stimuli.1
References:
1. Williams, D. E.; Rietman, J. A.; Maier, J. M.; Tan, R.; Greytak, A. B.; Smith, M. D.; Krause, J. A.; Shustova, N. B. J. Am.
Chem. Soc. 2014, 136, 1186.
INOR 60
CdSe sensitized photocathodes on a mesoporous transparent conducting oxide scaffold
Michael R. Norris, [email protected], Brandi M. Cossairt. Chemistry, University of Washington, Seattle, Washington,
United States
Quantum dots (QDs) are promising materials for solar energy conversion given their process-ability, absorption profile,
and expression of quantization effects that allow for tuning of optical and electronic properties. Although photovoltaics are
a promising route for harvesting sunlight, approaches for meeting global energy demands make it necessary to store solar
energy in chemical bonds (solar fuels). The focus of this project is the attachment of metal chalchogenide nanoparticles to
nanoparticulate tin-doped indium oxide films (nanoITO), a mesopourous, transparent conducting oxide, for use as a
photocathode in the reduction of protons to H2. Electrodes coated with nanoITO were synthesized and provide
approximately 5 times the surface roughness of planar electrodes as determined by electrochemical and
spectrophotometric analysis. We have shown that CdSe QDs can be bound to the surface of a nanoITO electrode through
bifunctional organic ligands bound to solution-processed CdSe QDs. UV-vis characterization of the films shows solutionsynthesized CdSe QDs attached via organic linkers maintain a narrow distribution of sizes, which is controllable through
the initial synthesis. Utilization of these electrodes in photochemical and photoelectrochemical experiments with methyl
viologen (MV2+) as an electron acceptor demonstrate the importance of controlling the quantum dot interfaces to affect
electron transfer rates. The use of a sacrificial electron donor in solution gives photochemical reduction of MV 2+ as
evidenced by the appearance of the strongly absorbing cation radical. When an electrochemical bias is used to fill the
holes instead of the sacrificial electron donor, however, MV2+ is not reduced, indicating a slow electron transfer process
from the electrode to the QD hole. To combat this slow electron transfer, we have coated the nanoITO electrodes with thin
films of ZnTe, a p-type semiconductor with appropriate band energies relative to CdSe such that excitation of the CdSe
leads to a hole in the valence band of ZnTe and an electron in the conduction band of CdSe. The films have been
characterized by UV-vis spectroscopy and SEM imaging. These electrodes are now being used in the photochemical and
photoelectrochemical reduction of MV2+ and show promise as a way to increase electron-hole separation distances to
slow down recombination.
INOR 61
Exploring the potential of nanostructured black silicon toward catalyst-assisted photoelectrochemical reduction
of water
Nicholas C. Anderson1, [email protected], Yixin Zhao4, Nathan R. Neale2, Howard Branz1, Paul W. King3. (1)
National Renewable Energy Laboratory, Denver,
Colorado, United States (2) Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado,
United States (3) 3313, National Renewable
Energy Lab, Lakewood, Colorado, United States (4) Shanghai Jiao Tong University, Shanghai, China
Nanostructuring the surface of silicon substrates for photoelectrochemical reduction of protons (i.e., water splitting) affords
many benefits compared to planar silicon. Recently, nanoporous silicon (also called “black silicon”) has been shown to
both (1) mitigate reflective losses of incoming light and (2) promote rapid bubble evolution, eliminating the need for
surfactants in the electrolyte. In addition, the increased surface area yields better kinetics for hydrogen production,
decreasing the over-potential required to reduce protons. Incorporating hydrogen production catalysts onto black silicon
surfaces further reduces the kinetic barrier for hydrogen production. For example, burying platinum nanoparticles in the
nanopores of black silicon reduces the onset potential required to reduce protons while simultaneously protecting the
catalytically active surface sites from oxidation. In this presentation, we will detail the chemistry at the platinum
nanoparticle catalyst/black silicon interface that affords the reduced onset potential for proton reduction and high stability
of this system toward oxidative degradation. We will also discuss the unique ability of black silicon to serve as a potential
universal photoelectrode for both inorganic and bio-inspired HER catalysts.
INOR 62
Zeolite protected nanocatalysts; Using a hard framework for selection and protection
Joseph Palomba2, [email protected], Joseph V. Morabito1, Chia-Kuang Tsung3. (1)
Boston College, Newton, Massachusetts, United States (2) Chemistry, Boston College,
Shrewsbury, Massachusetts, United States (3) Merkert Chemistry Center, Boston
College, Chestnut Hill, Massachusetts, United States
The benefits of zeolite materials have been carefully studied for the past century and applied in many catalytic, industrial
applications, including oil refinement. Often overlooked are the benefits of zeolites as a porous material. This study proves
that the highly stable and ordered structure of zeolite materials can be utilized as a singlecrystalline shell for metal
nanoparticles. In addition to selectivity of the pore network, this system improves catalysis by interacting a second
catalytically active material in close contact with the nanoparticle.
INOR 63
Mesoporous metal sulfides: Synthesis and photocatalysis
Feng Jiao, [email protected]. Chemical Engineering, University of Delaware, Newark, Delaware, United States
Mesoporous transition metal based materials have attracted much attention due to their great potential as catalysts,
electrodes, and magnetic materials. Since the nanocasting method was introduced, a wide range of mesoporous
transition metal oxides, such as Fe2O3, MnO2, Co3O4, NiO, and TiO2, with ordered pores and crystalline walls have been
synthesized from SBA-15 and KIT-6 silica templates. Some unique behaviors for nanocast materials have been found in
Li-ion batteries, catalysis, and optoelectronics.
Metal sulfides are of particular interest because of their potential applications in lightemitting diodes, sensors, separations,
catalysts, solar cells, fuel cells and batteries. Pioneer work by Zhao showed the possibility to synthesize ordered
mesoporous metal sulfides via the nanocasting method. In the case of CdS, a unique cadmium thioglycolate compound
was used as the source of Cd and S. Through a thermal treatment CdS was formed inside a mesoporous silica SBA-15
template, and after NaOH washing bundles of CdS nanowires were obtained. In another report from the same group,
mesoporous MoS2 and WS2 with highly crystalline walls have been fabricated using H2S as the source of sulfur. Although
some important progress has been made, the range of ordered mesoporous metal sulfides that can be synthesized is still
very limited.
In this presentation, we will show an oxide-to-sulfide transformation method to make well-ordered mesoporous metal
sulfides through a modified nanocasting oxide-to-sulfide process. Three first-row transition metal sulfides, FeS2, CoS2,
and NiS2, with highly ordered mesoporous structures and crystalline walls will be presented for the first time. To
demonstrate the properties of these newly synthesized mesoporous metal sulfides, a preliminary photocatalytic
investigation has been performed. As a photocatalyst, all the mesoporous metal sulfides exhibited significantly higher
activity under visible light compared to bulk metal disulfide counterparts. This work may be extended to other mesoporous
metal chalcogenides for a variety of potential applications.
INOR 64
Control of doping in Cu2SnS3, a novel photovoltaic absorber, through defects, alloying, and annealing
Lauryn Baranowski1,2, [email protected], Pawel Zawadzki2, Steven Christensen2, Stephan Lany2, Lynn
Gedvilas2, Eric Toberer1,2, Andriy Zakutayev2. (1)
Physics, Colorado School of Mines, Golden, Colorado, United States (2) National Renewable Energy Laboratory, Golden,
Colorado, United States
As the world’s demand for energy grows, the search for cost competitive and earth abundant photovoltaic (PV) materials
is becoming increasingly important. One promising material system for earth abundant PV is the Cu-Sn-S family, in which
several ternary compounds, including Cu4SnS4, Cu4Sn7S16, and Cu2SnS3, have been suggested as PV absorbers in prior
literature. Our work focuses on the Cu2SnS3 phase, which in our previous studies has been shown to avoid the numerous
problems associated with Cu4SnS4 and Cu4Sn7S16 compounds. Despite the relatively narrow band gap of Cu2SnS3, we
believe it to be the most promising absorber material in the Cu-Sn-S family (Appl. Phys. Lett., 103, 253902 (2013)).
In this study, we used combinatorial sputtering to deposit cubic Cu 2SnS3 films with a spatial gradient in Cu:Sn ratio across
each sample library. Experimentally, we found that the cubic Cu 2SnS3 has a large phase width, in contrast to previous
reports that show Cu2SnS3 as a line compound on the Cu2S-SnS2 pseudobinary phase diagram. We are able to
synthetically control the S chemical potential during film growth, which allowed us to synthesize combinatorial Cu 2SnS3
libraries under high, intermediate, and low S chemical potentials. We find different phase progressions in each library as a
result of the changing Cu:Sn ratio across each sample. These phase progressions can then be mapped onto the chemical
potential phase space as lines of constant S chemical potential (Chem. Mater., 2014, 26(17) 4951-4959).
By establishing synthetic techniques to access the entire range of Cu 2SnS3 on the chemical potential phase space, we
were then able to explore how the chemical potentials of the constituent elements affected the electrical properties of the
material. We found that hole concentrations varied between 1018 cm-3 – 1021 cm-3, depending on the chemical potentials of
Cu and S. The lowest carrier concentrations (desirable for PV applications) were achieved at low Cu and S chemical
potentials, when Cu2SnS3 is in equilibrium with SnS. Using this understanding, we performed post-deposition anneals in
an SnS atmosphere, which resulted in further reductions in the carrier concentration.
The project “Rapid Development of Earth-Abundant Thin Film Solar Cells” is supported as a part of the SunShot initiative
by the U. S. Department of Energy, Office of Energy
Efficiency and Renewable Energy under Contract No. DE-AC36-08GO28308 to NREL.
INOR 65
Symmetry breaking charge transfer in zinc dipyrrins for OPVs with open circuit voltage in excess of 1.3 V
Andrew Bartynski1, [email protected], Mark E. Thompson2. (1) Chemical
Engineering, University of Southern California, Los Angeles, California, United States
(2) Department of Chemistry, University of Southern California, Los Angeles, California,
United States
Over the past several years, the internal quantum efficiency for state of the art organic photovoltaic devices has
approached unity. This has been in large part due to precise understanding and control of the morphology present and
phenomena occurring within the devices. However, despite the gains achieved in efficient photocurrent production, the
open-circuit voltage (VOC) of organic devices are generally low and serves as a substantial limit to overall device
performance. The poor open-circuit voltages can ultimately be traced back to limitations imposed by fullerenes which,
despite their widespread use, typically between exhibit voltages of only 0.6 - 0.8 V. Intermolecular symmetry breaking
charge transfer (SBCT) has the potential to reduce the losses by creating a system where the electron and hole are
spatially separated, lowering the strength of their coulombic interaction. A zinc chlorodipyrrin (ZCl) is shown to undergo
SBCT in polar environments similar to the D/A interface. In OPVs with the same donor, tetraphenyldibenzoperiflanthene
(DBP), a ZCl acceptor yields a VOC of 1.33 V, 0.45 V larger than the analogous device with C60. The dramatic increase in
VOC and concominant increase in CT state energy reveals that devices containing ZCl are able to separate charges with
significantly lower recombination losses. The results presented for ZCl are the first documented application of a material
which undergoes SBCT in an OPV and the resultant VOC illustrate the great potential of this family of materials, and the
application of SBCT in general, in OPVs. INOR 66
Charge storage in cation incorporated α-MnO2
Matthias Young1, [email protected], Aaron Holder2,1, Steven M. George2,3, Charles Musgrave1,2. (1)
Chemical and Biological Engineering, University of
Colorado Boulder, Boulder, Colorado, United States (2) Chemistry and Biochemistry,
University of Colorado Boulder, Boulder, Colorado, United States (3) Mechanical
Engineering, University of Colorado Boulder, Boulder, Colorado, United States
Electrochemical supercapacitors utilizing α-MnO2 offer the possibility of both high power density and high energy density.
Unfortunately, the mechanism of electrochemical charge storage in α-MnO2 and the effect of operating conditions on the
charge storage mechanism are generally not well understood. Here, we present the first detailed charge
storage mechanism of α-MnO2 and explain the capacity differences between α- and βMnO2 using a combined theoretical
electrochemical and band structure analysis. We identify the importance of the band gap, work function, the point of zero
charge, and the tunnel sizes of the electrode material, as well as the pH and stability window of the electrolyte in
determining the viability of a given electrode material. The high capacity of α-MnO2 results from cation induced chargeswitching states in the band gap that overlap with the scanned potential allowed by the electrolyte. The charge-switching
states originate from interstitial and substitutional cations (H +, Li+, Na+, and K+) incorporated into the material. Interstitial
cations are found to induce charge-switching states by stabilizing Mn-O antibonding orbitals from the conduction band.
Substitutional cations interact with O[2p] dangling bonds that are destabilized from the valence band by Mn vacancies to
induce charge-switching states. We calculate the equilibrium electrochemical potentials at which these states are reduced
and predict the effect of the electrochemical operating conditions on their contribution to charge storage. The mechanism
and theoretical approach we report is general and can be used to computationally screen new materials for improved
charge storage via ion incorporation.
INOR 67
(CrxFe1-x)7C3 Solid solution as an efficient electrocatalyst for oxygen reduction and evolution reactions in both
acidic and alkaline media
Cheng Wan2, [email protected], Brian M. Leonard1. (1) Dept 3838, UWY Chemistry,
Laramie, Wyoming, United States (2) Chemistry, University of Wyoming, Laramie, Wyoming, United States
Regenerative fuel cells and other renewable-energy technologies relying on oxygen electrochemisty need efficient and
durable bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is a
big challenge up to date. Precious metals, like Pt, have high catalytic activity, however, their high price, poor durability,
and unsatisfactory OER activity make them unsuitable as bifunctional catalysts. Transition metal carbides (TMCs) have
been considered as possible solutions to solve this problem because some TMCs have similar electronic structure to Pt
and very comparable ORR activity. In addition, lower binding energy between oxygen and carbide surfaces provides the
possibility for TMCs to be better catalysts than Pt for OER. We have synthesized a group of phase pure (CrxFe1-x)7C3 solid
solutions with Mn7C3 structure for the first time as nanomaterials using aminemetal oxides composite method. These
bimetallic carbides were tested for both ORR and OER applications in both acidic (0.1 M HClO4 and 0.1 M KOH)
electrolytes. All (CrxFe1-x)7C3 solid solutions exhibit better ORR and OER activities than Cr 3C2 and Fe3C. Among the solid
solutions, (Cr0.4Fe0.6)7C3 show slightly poorer ORR activity and much higher OER activity than Pt on carbon.
INOR 68
Production of chemical feedstocks from pyrolytic lignin using transition metal oxidation catalysts
Michael S. Fortin1, Megan D. Mohadjer Beromi1, Amy Lai1, Charles A. Mullen2, Akwasi A. Boateng2, Nathan M. West1,
[email protected]. (1) Department of Chemistry and Biochemistry, University of the Sciences in Philadelphia,
Philadelphia, Pennsylvania, United States (2) Eastern Regional Research Center, United States
Department of Agriculture, Lansdale, Pennsylvania, United States
Fast pyrolysis of biomass produces a crude bio-oil from which lignin can be extracted during upgrading to hydrocarbon
fuels. In order to utilize this pyrolytic lignin as a feedstock for the production of valuable chemical products its structure
and properties must be evaluated to facilitate development of an effective depolymerization catalyst. We report here the
structural investigations of pyrolytic lignin from various biomass sources as well as the catalytic deconstruction of these
lignins. Transition metal oxidation catalysts, in particular Mn, Fe, and Cu complexes, have been investigated for their
ability to reduce the molecular weight and produce monomeric aromatic products from pyrolytic lignin. The effect of radical
mediating co-reagents, such as TEMPO and phenols has been investigated. These studies provide insight into the
mechanism of enzymatic lignin degradation. Schiff base ligands have been used to optimize the cleavage reaction;
including bifunctional ligands designed to assist in hydrogen atom abstraction.
INOR 69
On the use of cobalt complexes as mediators in dye sensitized solar cells: Instability of high-potential complexes
Joel T. Kirner1, [email protected], C M. Elliott2. (1) Chemistry, Colorado State
University, Loveland, Colorado, United States (2) Chemistry, Colorado State University, Fort Collins, Colorado, United
States
Dye-sensitized solar cells (DSCs) have been identified as a promising alternative technology for solar energy conversion
when compared to conventional devices, due to the DSC’s potential for cheap commercialization while still achieving
relatively high conversion efficiencies. Much research of late in this area has been focused on the use redox mediators
alternative to the prototypical iodide/triiodide couple, with the goal of tuning the redox potential in order to increase the
open-circuit potential, and therefore the power, of the DSC.
Cobalt complexes are particularly promising alternative mediators because they have smaller visible light absorption than
iodide solutions, they are non-volatile and noncorrosive to metal cathodes, and their redox potentials can be synthetically
tuned by altering the structures of their ligands. It should be beneficial to the field as a whole to have a library of mediators
with different redox potentials. In studying cobalt complexes with novel ligands employing highly electron-withdrawing
groups in order to make highpotential complexes, we have observed very low performance in DSCs. We have
characterized the novel complexes and have attributed their low performance to complex instability due to ligand lability—
a result which has been scantly addressed in the current literature. With this information, we can propose alternative
ligand structures for the further study of high potential cobalt mediators for application in DSCs.
INOR 70
Dipyridyl ketone based catalysts for carbon dioxide reduction
Heather Meylemans, [email protected], Paul Goodman. NAWCWD,
Ridgecrest, California, United States
As the amount of carbon dioxide (CO2) in the atmosphere has steadily increased over the last few decades, so has the
interest in finding a way to convert it into a useable energy source. Specifically, the catalytic reduction of carbon dioxide to
liquid fuel is a rapidly growing research area. In an effort toward production of solar fuels a novel series of catalysts for
CO2 reduction were synthesized and characterized. Catalysts of the type [M(dpk 2)]n (n = 0, +1, +2,+3; M = Cu, Co, Ni, Mn)
were studied for their interactions both CO2 and water. A proposed mechanism for these interactions was modeled and
products of the reaction are investigated by GC-MS to determine their usefulness as fuel precursors.
INOR 71
Enhancement of CO2 absorption utilizing zinc-based homogenous catalysts in primary amine solution
Moushumi Sarma1, Cameron Lippert1, Rachael A. Burrows1, Leland R. Widger1, [email protected], Christine
Brandewie1, Sean Parkin2, Kunlei Liu1. (1) Center for Applied Energy Research, University of Kentucky, Lexington,
Kentucky, United States
(2) Department of Chemistry, University of Kentucky, Lexington, Kentucky, United
States
Recent results in the development of homogenous catalysts for enhanced kinetics in post-combustion CO2 capture will be
discussed. Concern over rising global CO2 emissions has led to new regulations that will require carbon capture and
storage (CCS) systems on new coal-fired power plants. However, a significant decrease in the cost of this technology will
be required to make CCS from coal combustion viable in the current market. In order to meet the DOE goal of $40/ton for
CO2 capture, reduction in both capital and operating costs will need to be achieved. Recent work in our group has
involved the development of homogenous catalysts for improved kinetics of CO2 absorption, which would allow a
reduction in the size of the absorber tower and significant capital cost savings. Two novel Zinc(II) complexes that
incorporate ionic liquid moieties on the ligand backbone were found to be active homogeneous catalysts for CO2 capture
in the primary amine solvent MEA. The catalysts were thermally stable up to 145 °C and unaffected by flue gas
contaminants found in industrially-relevant post-combustion carbon capture conditions. However, two analogous Zn(II)
complexes that lack the the ionic liquid moiety do not show any catalytic activity towards the CO 2 hydration process in
amine solutions. The implication of these results on designing nextgeneration catalysts will also be described.
INOR 72
Exploring charge transfer induced spin cross-over redox mediators in quantum dot sensitized solar cells
Andrew J. Haring, John D. Godward, Michelle E. Pomatto, Amanda J. Morris, [email protected]. Chemistry, Virginia Tech,
Blacksburg, Virginia, United States
Quantum dot sensitized solar cells are primarily composed of mesoporous nanocrystalline titanium dioxide and cadmium
chalcogenide quantum dots. With the report of multiple exciton generation, these solar cell constructs have the potential to
reach efficiencies of 40% (8% over other single junction architectures). However, to date the highest efficiency
demonstrated with a QDSSC is ~7%. The reported efficiencies are low due to the inability to extract charge from the
photoanode. There exist no suitable redox mediators to complete the circuit in these liquid junction devices. To address
this critical need, presented herein is a study of a series of manganese complexes for use as charge transporters. These
mediators realized a 50% average increase in efficiency over cobalt trisbipyridine, a commonly used small molecule
mediator. This increase in efficiency is due to (1) the more positive reduction potentials of the complexes leading to
increase VOC and (2) higher fill factors indicative of decreased parasitic back electron transfer. The decreased rate of back
electron transport is most likely due to the barrier imposed by the charge transfer induced spin crossover exhibited by the
manganese complexes. Systematic manipulation of the ligand environment will be discussed as a method to increase
efficiency beyond the current set-point. Also, a detailed study of the recombination kinetics between electrons in TiO 2 and
the redox mediator will be presented.
INOR 73
Controlling interfacial energetics for efficient hybrid bulk heterojunction solar cells
Andrew J. Haring, Amanda J. Morris, [email protected]. Chemistry, Virginia Tech, Blacksburg, Virginia, United States
Hybrid bulk heterojunction solar cells (HBHJs) that combine metal oxide acceptors with polymeric donors provide a lowcost solid state device architecture and controllable donor/accepter interface morphology. These two benefits propel the
potential of these devices over that of other so-called next generation solar cells including dye-sensitized solar cells
(DSSCs) and traditional bulk heterojunctions (BHJs). Although HBHJs have been studied since the late 1990s, these
potential advantages have not been fully realized and efficiencies of only 2% have been reported. Indeed, the
photocurrents in these hybrid devices have been surprisingly low (5.6 mA/cm 2). To elucidate the underlying properties that
result in this low current, a detailed understanding of interfacial properties is required. Presented herein is a detailed
spectroelectrochemical and x-ray photoelectron spectroscopic study of the interfacial energetics that results upon
heterjunction formation. The results quantify a vacuum level offset of 0.8 eV between the polymer and the TiO 2 created by
spontaneous charge transfer from the polymer to deep trap states in the TiO2. This offset creates an approximate 0.7 eV
barrier to charge separation at the TiO2-polymer interface and explains the poor performance of cells to date. New
materials for improved photocurrent are proposed by tuning the energetics of the heterojunction.
INOR 74
Oxidation of carbon monoxide in basic solution catalyzed by nickel cyano carbonyls at ambient condition and the
prototype of a CO-powered alkaline flow battery type fuel cell
Wenfeng Lo, Tyler Berenson, Nathaniel Tracer, Daniel Shlian, Michael Khaloo,
Jianfeng Jiang, [email protected]. Department of Chemistry, Yeshiva University, Fort Lee, New Jersey, United States
The carbonylation of nickel(2+) hydroxide in the presence of one or two equivalents of cyanide quantitatively yields
nickel(0) cyano carbonyls: Ni0(CN)(CO)3- or Ni0(CN)2(CO)22-. Carbon monoxide is the reducing agent to reduce nickel(2+)
to nickel(0) and it was converted to carbonate. Both nickel(0) cyano carbonyls are structurally characterized. Both
complexes can react with oxygen gas and other oxidants readily to form nickel(2+) cyanide/hydroxide so that they can be
used as carbon monoxide oxidation catalysts in basic solution. An initial kinetics study of carbon monoxide oxidation by
oxygen gas was performed and the rate law suggested that the catalyzed carbon monoxide oxidation was first order on
oxygen partial pressure. A very crude fuel cell was constructed to demonstrate the feasibility of a carbon monoxide
powered alkaline flow battery type fuel cell.
INOR 75
Unassisted energy storage using layered chalcogenide semiconductors
James R. McKone3, [email protected], Rebecca A. Potash3, Francis J. DiSalvo2,
Hector D. Abruna1. (1) Cornell Univ, Ithaca, New York, United States (2) Cornell
University, Ithaca, New York, United States (3) Chemistry and Chemical Biology,
Cornell University, Ithaca, New York, United States
Photochemical water electrolysis is a promising approach for storing intermittant solar energy, but to date demonstrations
of this technology have suffered from challenges related to efficiency, cost, and durability. We are interested in exploring
alternative electrolyte systems that circumvent the challenges of solar water splitting to afford efficient, robust, and
scalable solar energy conversion and storage. To this end, we have characterized crystalline n-type layered chalcogenide
semiconductors that can photochemically oxidize halide electrolytes with high efficiency and stability. We have found that
illuminated n-WSe2 photoelectrodes, for example, can facilitate HI electrolysis to H2(g) and HI3(aq) at appreciable rates
without application of an external electrical bias. We have further developed and characterized a functional example of a
"solar flow battery," based on aqueous iodide and anthraquinone redox couples, that integrates solar energy capture,
storage, and subsequent liberation of the stored energy with high round-trip (i.e. photons in to electricity out) efficiency.
We will discuss the construction and characterization of these systems in detail, as well as opportunities to expand the
field of solar-driven galvanic cells.
INOR 76
Heterometallic mixed-valent molecular precursors for the synthesis of transition metal oxides
Evgeny Dikarev, [email protected], Craig M. Lieberman, Zheng Wei, Alexander S. Filatov. Univ of Albany Suny,
Albany, New York, United States
Mixed-ligand approach has been used to obtain homometallic mixed-valent diketonates Fe(II)/Fe(III) and
Fe(II)/Fe(III)/Fe(II) with dinuclear and trinuclear structures, respectively. The synthetic methodology has been extended to
design heterometallic diketonates with different metal:metal ratios. Mixed-transition metal heteroleptic complexes
Mn(II)/Fe(III) and Ni(II)/Fe(III)/Ni(II) have been successfully isolated and structurally characterized. Highly volatile
heterometallic diketonates have been utilized as single-source precursors for the low-temperature synthesis of the M2O3
and MO type mixed-transition metal oxides, proficient catalysts for the oxygen evolution reaction.
INOR 77
Ruthenium(II) complexes supported by electron-rich aromatic ligands for small molecule activation and catalysis
John P. Lee, [email protected], Michael J. Hankins, Ashley D. Riner. University of
Tennessee at Chattanooga, Chattanooga, Tennessee, United States
A series of piano-stool Ru(II) complexes of the type [Ru(p-cymene)(L)(Cl)2] {L = tris(4fluorophenyl)phosphine, tris(4trifluoromethylphenyl)phosphine, tris[3,5bis(trifluoromethyl)phenyl]phosphine, tris(2,2,2-trifluoroethyl)phosphite, and
tris(1,1,1,3,3,3-hexafluoro-2-propyl)phosphite} have been prepared from the dimeric complex [Ru(p-cymene)(Cl)2]2 and
two equivalents of L at room temperature. These complexes have been fully characterized by multi-nuclear NMR
spectroscopy, UV-vis spectroscopy, and single crystal X-ray diffraction. All have been isolated as analytically pure orange
to red solids, and as the number of fluorine atoms increase the color becomes more red. Initially, the complex [Ru(pcymene){P(OCH2CF3)3}(Ph)(OTf)] (1) has been synthesized from [Ru(p-cymene){P(OCH2CF3)3}(Cl)2] as a potential
catalyst for olefin hydroarylation. Olefin hydroarylation is defined as the formation of a new C-C bond via addition of an
aromatic C-H bond across an olefin. Complex 1 has been isolated as an analytically pure yellow solid and fully
characterized by multi-nuclear NMR spectroscopy. Preliminary catalysis attempts involving the reaction of benzene and 1hexene with 2 mol% 1 yielded a stoichiometric amount of 2-phenyl-1-hexene by GC-MS. Salient characterization details of
these complexes, the reactivity of 1 for potential catalysis, and future directions will be discussed.
INOR 78
Investigating the mechanism of N-H bond activation by a sterically congested PCP-iridium complex
David A. Laviska, [email protected]. Department of Chemistry, Lafayette College, Easton, Pennsylvania, United
States
The activation of N-H bonds has been shown to be an important step in a variety of organometallic reaction mechanisms.
For example, the iridium fragment (tBuPCP)Ir
(tBuPCP = {κ3-2,6-bis[(di-tert-butylphosphino)methyl]phenyl}) has been shown to catalytically convert secondary and
tertiary amines into imines and enamines, respectively. My group has previously reported results of studies with various
primary amines, including the catalytic production of nitriles with selected alkyl amines. However, aryl amines yield more
complicated product mixtures due to competing C-H activation mechanisms. In order to better understand these latter
mechanisms, a series of amine and imine substrates were studied using (tBuPCP)Ir and norbornene as a hydrogen
acceptor. The results of our experiments show that a remarkably diverse gallery of products can be generated depending
on the steric and conformational attributes of the initial substrate.
INOR 79
Progress toward the synthesis, characterization, and catalysis of iridium complexes containing [N,N,N]-dianionic
pincer ligands
Hussnain Sajjad, [email protected], Abby R. O'Connor. Chem Dept, College of New Jersey, Ewing, New Jersey, United
States
Transition metal complexes that can mediate the cleavage of otherwise strong bonds are highly sought after for the
purposes of use in synthetic processes. C-H bond functionalization is an important transformation in organic chemistry as
it can permit the conversion of cheap and abundant molecules like alkanes into value-added compounds, such as
converting methane into methanol. Prior research in this field has shown limited success with the use of platinum
complexes, but the need for a stoichiometric platinum oxidant has prevented the work from developing into a practical
process. Thus, there is a need for more active and less expensive catalysts for C-H activation. Work in the O’Connor lab
is focused on the synthesis of new electrophilic iridium complexes that are capable of catalytically activating strong C-H
bonds, which could then be functionalized. By exploiting the stabilizing effects of chelating, electronically rich ligand
scaffolds we hope to attain and stabilize the higher oxidation states on iridium, in particular the Ir(III)-Ir(V) couple. We
report here the synthesis and characterization of new [N,N,N]-dianionic pincer ligands and iridium complexes containing
these new ligands. Preliminary results highlighting catalytic H/D exchange reactions with benzene are also described.
Efficiency of the catalysts has been analyzed in terms of turn-over number and frequency with the end goal of developing
more active and selective catalysts for this C-H activation.
INOR 80
Copper-catalyzed acyloxylation of aromatic halides
Fabiola Barrios-Landeros, [email protected], Benjamin Ben-Zvi, Abraham E. Kessler,
Brian W. Goodman, David Y. Drory, Dov L. Levine. Chemistry, Yeshiva University, New York, New York, United States
Cross-coupling reactions catalyzed by transition metals have revolutionized the field of organic synthesis facilitating the
formation of a variety of C-C and C-heteroatom bonds. However, carboxylic acids have rarely been used as the coupling
partner for the formation C-O bonds to synthesize aryl carboxylates. We have identified reaction conditions to successfully
couple aryl halides with aliphatic and aromatic carboxylic acids using salts of copper(I) and silver(I). This reaction offers
an alternative to the traditional esterification methods which require phenol as starting material. The effect of solvent,
bases and addition of O and N ligands will be discussed. The reaction progress has been monitored by GC, MS, IR and
UV/Vis to better understand the reaction mechanism and the active metal intermediate species. The results are consistent
with a catalytic cycle were transmetalation to the Cu(I) salt is the first step followed by oxidative addition and reductive
elimination.
INOR 81
Microwave-assisted copper-catalyzed reactions of aryl halides via concurrent tandem catalysis
Douglas J. Brown, Shirley Lin, Amy H. Roy MacArthur, [email protected]. United States Naval Academy, Annapolis,
Maryland, United States
Concurrent tandem catalytic (CTC) methodologies have been developed for the hydrodehalogenation and the cyanation
of aryl halides using a multifunctional copper catalyst. New CTC methodologies are currently under development for C-N
bondforming reactions such as the amination and amidation of aryl halides. The proposed CTC mechanism consists of an
initial halide exchange step to form aryl iodides from less reactive aryl bromide and aryl chloride substrates. As the aryl
iodide intermediate is generated, it is consumed as the substrate in a subsequent C-H, C-C, or C-N bondforming reaction.
Optimized conditions and substrate scope for these reactions, along with evidence that these reactions are occurring via a
CTC mechanism, will be presented. INOR 82
Ambiphilic late-metal silyl and silylene complexes for cooperative activation of small molecules
Alexander Deetz1, [email protected], Matthew T. Whited2. (1) Carleton College,
Boulder, Colorado, United States (2) Department of Chemistry, Carleton College, Northfield, Minnesota, United States
Metal-ligand multiple bonds are noteworthy for their ability to engage in interesting reactivity, especially in cases where
incomplete bonding leads to significant disparity of electron density, creating adjacent Lewis-basic and -acidic sites. The
coordinative and redox flexibility of organosilicon ligands make them particularly well-suited for exploring cooperative
reaction pathways that exploit these electronic properties. We have targeted late-metal complexes containing such
“electronically-frustrated” linkages incorporated into pincer-type ligand architectures in an effort to stabilize these
otherwise highly reactive moieties. We will present studies on the synthesis and metallation of several related ligand
scaffolds with group 9 metal precursors and the reactivity of the resulting complexes.
INOR 83
Modulation of tris(diphenylphosphinomethyl)phenylborate donor ability via introduction of M(CO) 3 units at the
boron-bound phenyl substituent
Paul J. Fischer, [email protected], Alexander B. Weberg, Trent D. Bohrmann,
Hanyue Xu. Chemistry, Macalester College, Saint Paul, Minnesota, United States
Tris(diphenylphosphinomethyl)phenylborate (PhBPPh) is a member of a class of strong field ligands that are envisioned as
hybrids of classical, facially-capping, soft phosphines such as triphos (CH3C(CH2PPh2)3) and the hard nitrogen-based
donor hydrotris(1-pyrazolyl)borate (Tp). The success of PhBPPh ligands in supporting novel chemistry is attributed in part
to the impact of the seemingly insulated borate negative charge (at least via simple resonance forms) at metal centers.
Various strategies have been adopted for effective modulation of R'BPR donor ability, including changing the phosphine
substituents (R) and the substituent at the bridgehead boron atom (R'). This presentation will describe our efforts to
influence the electronic impact of the borate charge via coordination of 12-electron group VI metal M(CO)3 fragments at
the electronrich boron-bound phenyl substituent. The resulting bimetallic complexes feature a new binding mode for
PhBPPh in which two M(CO)3 fragments are bridged. The synthesis and characterization of zwitterionic Mn(CO) 3(PhBPPh),
the first Mn(I) complex containing a facially-capped R'BPR to isolated in pure form, will also be discussed.
INOR 84
Cyclic hydroboration using azaferrocene-stabilized borenium cations
Timothy J. Brunker1, Sarah Krause2, [email protected], Arnold L.
Rheingold3. (1) Dept of Chemistry, Towson University, Towson, Maryland, United States (2) Chemistry, Towson
University, Towson, Maryland, United States (3) UCSD, Carlsbad, California, United States
Azaferrocene-boranes (Cp*FePyr-BH3) have been prepared with varying substituents at the α- position of the pyrrolyl ring,
either by use of preformed pyrrolyl ligands or by deprotonation of less substituted azaferrocene-boranes and electrophilic
quenching. Deprotection yields the free azaferrocene. X-ray crystal structures have been obtained in several cases and all
compounds thoroughly characterized by NMR spectroscopy. The corresponding borenium cations [Cp*FePyr-BH2]+ were
prepared by hydride abstraction utilizing trityl tetra(pentafluorophenyl)borate and were characterized by NMR
spectroscopy. Hydroboration with 1,5-cyclooctadiene yielded variable amounts of both the [3.3.1] and [4.2.1]
dialkylborenium species in ratios dependent upon the steric environment. In some cases hydride abstraction from the
corresponding azaferrocene9-BBNH (9-BBNH = 9-borabicyclo[3.3.1]nonane) adduct was performed and also gave similar
mixtures of [3.3.1] and [4.2.1] dialkylborenium species. Rapid isomerization via a dehydroboration-hydroboration
sequence is proposed to explain these observations. Compared to neutral boranes, these isomerization processes are
considerably more facile with these cationic hydroborating agents. Similar reactions with isoprene gave results consistent
with partial dihydroboration. Conversion of the intermediate alkylborenium species to neutral boranes was performed in all
cases to confirm the assignments.
INOR 85
Trends observed during the nickel-catalyzed dehydrogenation of ammoniaborane utilizing asymmetrical
triazolylidene ligands
Meghan O. Talbot1, [email protected], Marites Guino-o2. (1) University of St.
Thomas, Stillwater, Minnesota, United States (2) Chemistry Department, University of
St. Thomas, Saint Paul, Minnesota, United States
In 2007, Baker demonstrated that Ni(TPT)2 (TPT = 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4triazol-5-ylidene) gave one of the
highest extent of dehydrogenation for ammoniaborane compared to a series of transition metal catalysts. In recent years,
our group has steadily reported preliminary results of the synthesis and stereo-electronic ligand effects of asymmetrical
triazolylidenes towards the nickel center. Herein, we report observed trends in hydrogen gas evolution when asymmetrical
triazolylidenes were used during the nickel-catalyzed dehydrogenation of ammonia-borane. We will also report on reaction
trends observed utilizing 11B {1H} NMR Spectroscopy.
INOR 86
Roles for metal cofactors of MutY enzymes in preventing DNA mutations
Sheila S. David, [email protected]. Dept Chemistry, Univ of California, Davis, California, United States
DNA repair processes play an important role in maintaining the chemical integrity of DNA and preserving its informational
content. The damaged base 8-oxoguanine (OG) is particularly sinister due to its subtle structural change that evades
detection during replication and results in incorrect insertion of adenine to form OG:A mismatches. The bacterial and
mammalian MutY glycosylases prevents mutations by excising adenine from OG:A mismatches as the first step in base
excision repair. In addition to an [4Fe4S] cofactor, we recently identified a new “zinc linchpin” motif in a region of
mammalian MutY that connects the catalytic base excision domain and the OG recognition domain. In vitro and cellular
assays on WT and Cys to Ser mutants have revealed an important function for zinc coordination within this region on
overall protein stability, iron-sulfur cluster insertion, and ability to mediate DNA damage repair. We have also found that
mammalian MutY enzymes are more sensitive to biological oxidants than their bacterial counterparts due to the presence
of this Zinc linchpin motif. In addition, we have evaluated several human MutY homolog (MUTYH) variants associated with
colorectal cancer in this region to determine the influence of these variations on zinc coordination, and DNA repair activity.
INOR 87
New ROS-activated agents that specifically targert AML cancer cells
Edward J. Merino, [email protected]. Deptartment of Chemistry, University of Cincinnati, Cincinnati, Ohio, United States
Some cancers, like acute myeloid leukemia (AML), are addicted to reactive oxygen species and display large increases in
their concentrations. The reactive oxygen form of hydrogen peroxide is used to activate cell growth pathways when a
growth signal is present. High levels of endogenous hydrogen peroxide allow the cancer cells activate the pathways at
will. We designed a new hydrogen peroxide-activated agent with two key modules. The first module is a peroxideacceptor and the second is a pendant amine. The acceptor module is an amidohydroquinone that oxidizes into a lethal
form in the presence of hydrogen peroxide. The pendant amine module induces selectivity between AML and normal
cells. Synthesis and testing of fourteen compounds that differed at the pendent amine led to the identification of an agent
with two micromolar activity against AML cancer cells and an eleven fold-lower activity in healthy blood stem cells.
Interestingly analysis shows that upon oxidation the pendant amine cyclizes with the hydroquinone to give a bicyclic
aromatic compound with the amine’s substituents out of the plane. This new bicyclic compound is highly reactive with a
variety of nucleophiles. Structural characterization and rates of reaction will be discussed. Thus, using this chemical
approach we have obtained a simple, potent, and selective ROSactivated anti-cancer agent.
INOR 88
Evidence of histidine and aspartic acid phosphorylation in human prostate cancer cells
Alan E. Friedman, [email protected]. Environmental Medicine, University of Rochester, Rochester,
New York, United States
We have developed a method to identify previously undetected histidine and aspartic acid phosphorylations in a human
prostate cancer progression model. A phosphoproteome of our cell line model is presented, with correlation of modified
protein expression between the three states of cancer: non-tumorigenic, tumorigenic and metastatic cells. With the
described interaction proteins potentially phosphorylated by NM23-H1, cellular responses to motility and conformational
change stimuli would be achievable. We detect 20 novel histidine phosphorylated (pHis) and 80 novel aspartic acid
phosphorylated (pAsp) proteins with diverse functions, such as metabolism, protein folding, and motility. Our data indicate
that pHis and pAsp are much more prevalent than previously appreciated and may provide insight into the role of NM23H1 and signaling events that are critical for metastasis. Using the described method for detecting histidine and aspartic
acid phosphorylations and our prostate cancer progression cell system, the potential function of NM23-H1 in suppressing
metastasis with a two-component regulation system will be discussed.
INOR 89
Nitric oxide regulation of bacterial biofilms
Elizabeth M. Boon, [email protected]. Stony Brook University, Stony Brook, New York, United States
Bacteria colonize most surfaces, forming multicellular, antibiotic-resistant, communities known as biofilms. Biofilms cause
chronic infections and persistent biofouling of medical implants, marine vessels, and environmental sensors. Biofilm
dispersal by nanomolar nitric oxide (NO) appears to be a general phenomenon, but fundamental questions remain
concerning the identity of the NO sensor and mechanism of signal transduction. NO has been reported to disperse
bacterial biofilms through regulation of intracellular cyclic-di-guanosine monophosphate (c-di-GMP) concentrations. C-diGMP is a tightly regulated second messenger-signaling molecule that is tightly correlated with biofilm formation. H-NOX
(heme-nitric oxide/oxygen binding) proteins are well known NO sensors in eukaryotes that are also conserved in many
environmental and opportunistic pathogenic bacteria. Indeed, we have shown that NO/H-NOX signaling disperses
bacterial biofilms through a mechanism consistent with c-di-GMP signaling. However, H-NOX proteins are not conserved
in most human pathogens, even those for which the mechanism of action is known to involve c-di-GMP signaling.
Therefore, an alternate NO sensor must also exist. We have identified a potential alternate NO sensor, a novel
hemoprotein we named NosP (nitric oxide sensing protein). NosP domains are conserved in 91% of bacterial genomes,
they bind NO, but not molecular oxygen, as expected for a NO-specific sensor, and they are encoded as fusions with, or
in close chromosomal proximity to, proteins annotated as c-di-GMP synthesis or hydrolysis enyzmes. Therefore we
hypothesize that NO generally disperses bacterial biofilms through regulation of intracellular c-di-GMP concentrations, but
the sensor varies; both NosP and H-NOX can fill this role. Evidence from biochemical characterization of proteins in the
NosP and H-NOX signaling pathways, as well as genetic and biofilm growth studies, will be presented to support our
hypothesis
INOR 90
DNA-protein self assemblies on millimeter length scales: Artificial light antenna systems
Challa V. Kumar, [email protected]. Univ of Connecticut, Storrs Mansfield, Connecticut, United States
Protein-DNA complexes play a major role in biology and they provide unprecedent control over the organization of small
molecules embedded in these biological macromolecules. Cationized bovine serum albumin, for example, binds to double
helical DNA with high affinities and these self assemble into extremely large structures on millimeter length scaltes. While
the origin of such assembly is a fascinating story, these macromolecules provide unique opportunities to organize small
molecules for practical applications. For example, an artificial antanna system has been created where three consequitive
FRET steps are demonstrated. Our system consists of four different fluorescent dyes, double helical DNA and cationized
bovine serum albumin which are all self assembled on glass by simple drop-casting. Imging studies show that the
proteinDNA complex self assemles into superhelices which further form coils of coils and unltimately coiled ropes and
extremely flat, extremely large assemblies with nearlyperfect geometries on millimeter length scales. These assemblies
absorb in the 300-600 nm window of the visible spectrum, and excitation of any one of the three different donor dyes
resulted in efficient energy transfer to the terminal acceptor, which resulted in intense emission around 610 nm, with an
overall efficiency > 88%. Excitation spectra clearly support energy transfer among the four dyes, and excitation moved
from higher energy donors to the appropriate acceptors in a step-wise manner (energy cascade). Excitation transfer
stopped when one of the jumper dyes were omitted, which provided direct evidence for cascade transfers. The entire
assembly continued to function efficiently even after exposure to 80˚C for 56 days, an important consideration for field
applications. These unusually stable, highly efficient, multi-chromophoric, selfassembled, artificial antennas are the first of
their kind demonstrating cascade energy transfer, and they could facilitate the construction of inexpensive bio-solar cells
from dyes, proteins and nucleic acids.
INOR 91
Assay and mechanistic investigations of iron oxidation catalysts
Cynthia M. Dupureur2,1, [email protected], Yang Song2,1, Howard Mayes2,1, Eike B.
Bauer2,1. (1) Department of Chemistry, Saint Louis, Missouri, United States (2) Univ of Missouri, Saint Louis, Missouri,
United States
The use of iron catalysts in the oxidation of organic molecules has broad advantage and application. Iron is cheap,
abundant and environmentally benign. We have undertaken absorption spectroscopic studies to understand the kinetics
and mechanism of oxidation reactions catalyzed by iron complexes. More specifically, we are working with the
commercially available White-Chen catalyst and a small series of iron(II) αaminopyridine complexes, the two most
commonly used oxidants H2O2 and tBuOOH, and a variety of substrates with visible absorption spectra. By following both
spectral changes and fitting absorbance changes as a function of time, we are able to characterize changes in both the
metal complex and the substrates. This allows us to isolate the kinetic signatures of multiple processes that accompany
the reactions. For example, does peroxide (pre)react with the complex to prepare the catalytic species? Are these
coincident with substrate oxidation? These and related questions are addressed in this study.
INOR 92
Synthesis without the solvent: Mechanochemical approaches to organometallic complexes
Nicholas R. Rightmire, David L. Bruns, Timothy P. Hanusa,
[email protected]. Vanderbilt Univ Dept Chem, Nashville, Tennessee, United
States
Mechanochemical synthesis, usually performed by the grinding or milling of reagents with little or no solvent, presents an
opportunity to investigate the preparation of compounds under conditions that complement those encountered in solutionbased routes. It enjoins a rethinking of the “parameter space” of synthetic methodology, e.g., the suitability of starting
materials and the range of products that can be expected from a given reaction. In organometallic chemistry, for instance,
useable solvents may interfere with the interaction of reagents, or solvent molecules may bind strongly to the products,
and change their structure and reactivity. Conversely, some reactions that proceed easily in organic media may result in
decomposition if the dry reactants are simply ground together. Metal complexes with sterically demanding allyl ligands,
specifically those of the form A′xM (A´= [1,3-(SiMe3)2C3H3]–), starkly illustrate these points. Thus the unsolvated species
A´3Al can be prepared through the milling of AlX3 and K[A´], although attempts to prepare the compound in solution are
not successful (Organometallics, 2014, doi: 10.1021/om5009204). In contrast, the reaction of NiBr 2(dme) with K[A´] in
THF readily yields the nickel complex A´2Ni, whereas milling the reagents results in decomposition and the formation of
the substituted hexadiene {A´}2. Opportunities and limitations of mechanochemical activation in this area of organometallic
synthesis will be discussed, including computational investigations of the reactivity differences. INOR 93
f-Element single-molecule magnets
Katie R. Meihaus, Selvan Demir, Jeffrey D. Rinehart, Michael Nippe, Joseph M. Zadrozny, Jeffrey R. Long,
[email protected]. Department of Chemistry, University of California, Berkeley, California, United States
Scientists have long employed lanthanide elements in the design of materials with extraordinary magnetic properties,
including the strongest magnets known, SmCo5 and Nd2Fe14B. The properties of these materials are largely a product of
fine-tuning the interaction between the lanthanide ion and the crystal lattice. Recently, synthetic chemists have begun to
utilize f-elements—both lanthanides and actinides—for the construction of single-molecule magnets, resulting in a rapid
expansion of the field. The desirable magnetic characteristics of the f-elements are contingent upon the interaction
between the single-ion electron density and the crystal field environment in which it is placed. Taking advantage of this
interaction, new approaches for synthesizing singlemolecules magnets based upon lanthanide and actinide ions will be
presented. Focus will be on recent work involving: (i) the use of an equatorial ligand field to create erbium(III) singlemolecule magnets, (ii) the synthesis and characterization of radicalbridged dilanthanide complexes exhibiting strong
magnetic exchange and record high blocking temperatures, (iii) the observation of ferromagnetic exchange coupling
between uranium(IV) and transition metal ions in chloride-bridged complexes, and (iv) the observation of slow magnetic
relaxation in mononuclear uranium(III) complexes.
INOR 94
Monomeric rare-earth metal imide complexes
Reiner Anwander2,1, [email protected], Dorothea Schaedle2,1, Cäcilia
Maichle-Mössmer2,1, Christoph Schädle2,1. (1) University of Tuebingen, Tuebingen,
Germany (2) Institut für Anorganische Chemie, Tübingen, Germany
During the past decade molecular rare-earth metal (Ln = Sc, Y, La - Lu) chemistry has witnessed several breakthroughs in
the field of organometallic complexes containing multiple bonding interactions with main-group fragments. Monomeric
[Ln=NR] imide complexes remained scarce for lack of efficient synthesis protocols. In 2010, Ln(III) imide chemistry was
stirred by the successful isolation of the first scandium(III) terminal imide compound by Chen et al, exploiting a Lewis
base-induced alkane elimination. We have developed organoaluminum-promoted syntheses of rare-earth metal imide
complexes featuring even the large metal centers lanthanum and cerium. Recent progress in this area will be reported.
INOR 95
RE-cycle efforts for nationally critical elements: Fundamental coordination chemistry of scandium
Timothy J. Boyle1, [email protected], Jeremiah M. Sears1, Michael L. Neville1,
Daniel T. Yonemoto1, Roger Cramer3, Timothy N. Lambert4, Ryan F. Hess2, Leo J. Small4. (1) Advanced Materials
Laboratory, Sandia National Laboratories, Albuquerque,
New Mexico, United States (2) MS 0892, Sandia National Laboratories, Albuquerque,
New Mexico, United States (3) Chemistry, U. of Hawaii - Manoa, Honolulu, Hawaii, United States (4) Sandia National
Laboratories, Albuquerque, New Mexico, United
States
The Congress of the United States of America has declared a number of elements of nationally critical interest, a
significant number of which are the lanthanides. Often considered with the lanthanides are the Group 3 cations, La and Y.
Overlooked but just as critical due to its rarity is Sc. This presentation will focus on the extraction, manipulation, and
deposition of Sco as a means to recycle the rare earth metals. A number of Sc salts (NO 3, SO4, PO4, O2CR), solvates,
halides, amides, and alkoxides have been synthesized and characterized for the first time. A variety of solvent systems
have been explored including novel ionic liquids for the electrochemical deposition of Sc o. The synthesis, characterization,
and electrochemical properties of these novel compounds will be presented.
_______________________
This work was supported by the Laboratory Directed Research and Development (LDRD) program at Sandia National
Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a
wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DE-AC04-94AL85000
INOR 96
Role of lanthanide ions in metal-seamed organic nanocapsules
Jerry L. Atwood1, [email protected], Harshita Kumari2, Kyle Feaster1. (1) Univ of
Missouri, Columbia, Missouri, United States (2) Univ of Missouri, Columbia, MO 65211, Missouri, United States
One of our earliest reports on organic nanocapsules and related supramolecular architectures noted the key presence of
lanthanide ions at the core of the capsule: Science, 285, 1049 (1999). Since that time, lanthanide ions have been shown
to seam nanocapsules and other architectures in the solid state and in solution: ChemComm, 50, 109 (2014). In
particular, the elucidation of solution structures using SANS techniques has revealed remarkable results. In this
presentation, emphasis will be placed on new results regarding the relation of solution architecture to solid state structure.
INOR 97
To cluster or not to cluster
Gerd Meyer1,2, [email protected]. (1) Department of Chemistry, Iowa State
University, Ames, Iowa, United States (2) Department of Chemistry, University of Cologne, Cologne, Germany
The rare-earth elements have essentially three valence electrons; the 4f electrons may be treated as core electrons. The
divalent state comes in two varieties, with electronic configurations of [Xe]4fn5d06s0 or [Xe]4fn-15d16s0. The first gives rise
to alkaline-earthmetal salt-like behavior; in the latter case the 5d1 electron may either be delocalized into a 5d
(conduction) band (solid state) or trapped in an anion with superbulky ligands (organometallics). Furthermore, 5d orbitals
play a decisive role in the formation of rareearth metal (R) clusters encapsulating an endohedral transition metal atom (T).
These clusters may be isolated─although not naked─or condensed via common edges (frequent), faces (rare) or vertices
(extremely rare) to oligomers, chains, layers or networks. All of these polar-intermetallic clusters are built into solids with
the addition of halide ligands (X). Bonding in these cluster complexes is predominantly heteroatomic, T─R and R─X,
respectively, with little, nevertheless important, homoatomic T─T (if possible) and R─R interactions. INOR 98
iPhone glues: An introduction to the chemistry of reliable and reworkable capillary-flow underfills
Timothy Champagne, [email protected]. Henkel, Irvine, California, United States
Henkel Electronic Materials is a global leading provider of qualified materials and adhesives for the electronics industry.
One important class of adhesives in the industry is capillary-flow underfills for solder joint encapsulation. An underfill
typically must be thermally and mechanically robust, humidity resistant, electrically inert, and possess strong substrate
adhesion to meet the reliability requirements. However, in addition to being a strong glue, the underfill must also be easily
removable to meet rework-ability requirements to recover manufacturing cost. These opposing forces between reliability
and rework-ability invite innovative chemical solutions for the product chemist to find the appropriate balance. Thermallytriggered Diels-Alder adducts composed of dicyclopentdiene and alpha-alkoxy ester moieties have been incorporated as
one balanced solution. The application and performance of developed underfills will be discussed.
INOR 99
Synthesis of sodium borohydride without sodium metal
Nathan Allen1, [email protected], Robert Butterick1, Dean M. Millar1, David C.
Molzahn2. (1) The Dow Chemical Company, Midland, Michigan, United States (2) Dow
Chemical Company, Midland, Michigan, United States
Sodium borohydride is commecially made by the Schlesinger Process, which uses 4 equivalents of sodium hydride with
trimethylborate, B(OCH3)3 + 4 NaH → NaBH4 + 3
NaOCH3. A production route that produces sodium borohydride without sodium metal would be preferrable. Presented
here is a process utilizing aluminum metal, sodium hydroxide, and boric acid as starting materials to produce both either
sodium borohydride or sodium hydride.
INOR 100
Multi-metallic materials containing f-elements
Joy H. Farnaby1, [email protected], Polly L. Arnold2, William J. Evans3, F. Geoffrey N. Cloke4. (1) Chemistry,
Imperial College London, London, United Kingdom
(2) Univ of Edinburgh Sch of Chem, Edinburgh, London, United Kingdom (3) Dept of
Chemistry, University of California Irvine, Irvine, California, United States (4) Chemistry, University of Sussex, Brighton,
United Kingdom
The best magnetic materials are multi-metallic e.g. Nd2Fe14B. Organometallic lanthanide and actinide complexes have
been found to be single molecule magnets, with competitive working temperatures. Heterobimetallic materials, which
combine lanthanides with depleted uranium have the potential to outperform the current state-ofthe-art. However, to
actualize the unique properties of the f-elements, our understanding of their fundamental bonding and structure must
improve. The research presented here utilizes known and new uranium precursors, to study the synthesis of actinide
materials, and in combination with lanthanide precursors or materials, to develop new multi-metallic molecules and
materials. Drawing on previous work, several
synthetic strategies for the formation of heterobimetallic f-organometallics are presented, including the use of metal
vapour synthesis.
INOR 101
Aggregates of Mn3 single-molecule magnets: Synthesis, properties, and quantum effects
George Christou1, [email protected], Tu N. Nguyen1, Muhandis Shiddiq2, Andrew
M. Mowson1, Khalil A. Abboud1, Stephen Hill2. (1) Department of Chemistry, Univ of
Florida, Gainesville, Florida, United States (2) NHMFL and Florida State University, Tallahassee, Florida, United States
Single-molecule magnets (SMMs) are molecules that function as nanoscale magnets at low temperature and also display
interesting quantum properties. They have consequently been proposed as molecular components of spin-based quantum
computation and spintronics devices. For such applications, coupling of SMMs to each other or to other components of
the device is essential, but the coupling must be very weak in order to maintain the intrinsic single-molecule properties of
each SMM. We have thus been exploring the linkage of two or more SMMs into aggregates that would exhibit very weak
(but non-zero) inter-SMM interactions. The challenge has been to link multiple units together in a way that gives robust
non-polymeric products, with only very weak coupling between them, and ideally with their easy-axes parallel. The latter is
to allow the search for nebulous and fragile quantum effects such as quantum superposition states/entanglement of the
SMMs. We have been using Mn3 SMMs with S = 6 for this work and have developed two general ways to link them
together into oligomers, through specially designed dioximate groups, or a variety of dicarboxylates. The syntheses,
structures, magnetic properties and HF-EPR spectra of a selection of these aggregates will be described.
INOR 102
Theoretical approaches to the control of spin states in molecules
Carmen Herrmann, [email protected]. Department of Inorganic Chemistry, University of
Hamburg, Hamburg, Germany
The control of spin states in molecules is crucial not only for a variety of potential applications such as molecular memory
elements or switches, but also with respect to fundamental science. This control can be achieved, e.g., by manipulating
the chemical composition of spin centers and bridging ligands, by varying temperature, pressure or external fields, or by
mechanical means. We discuss examples for how theory can help in achieving spin state control, and which challenges
this poses for present-day theoretical methodology, in particular for Kohn-Sham density functional theory.
DFT-optimized structures for a photoswitchable dinuclear Co complex in its ferromagnetically coupled state (BP86/TZVP). Complex
synthesized by Juergen Heck and coworkers, University of Hamburg.
INOR 103
Development of redox and environmental switches for control of magnetic communication in molecular
complexes
Matthew P. Shores1, [email protected], Robert Higgins2, Christina Klug2, indrani bhowmick2, Stephanie
Fiedler3, Anthony K. Rappe2. (1) Department of Chemistry, Colorado State University, Fort Collins, Colorado, United
States (2)
Colorado State University, Fort Collins, Colorado, United States
Toward designing multifunctional molecule-based magnetic materials, we have focused on understanding the noncovalent interactions that control spin states and magnetic communication in metal-centered complexes. I will present our
group’s recent results in developing hybrid materials for guest-dependent spin-state switching. I will also outline new
efforts in switching the redox state of a bridging ligand (p-TEPA = tris(4ethynylphenyl)amine) to control magnetic
communication in trinuclear first-row metal complexes. The syntheses, structural and magnetic characterizations, and
electronic structure calculations for key components of these families of complexes will be presented.
INOR 104
Metal silicide nanowires for detection and manipulation of magnetic skyrmions
Song Jin, [email protected]. Univ of Wisconsin, Madison, Wisconsin, United States
Skyrmions, novel topologically stable spin vortices, hold promise for next-generation magnetic storage due to their
nanoscale domains to enable high information storage density and their low threshold for current-driven motion to enable
ultralow energy consumption. One-dimensional (1D) nanowires are ideal hosts for skyrmions since they not only serve as
a natural platform for magnetic racetrack memory devices but also can potentially stabilize skyrmions. We have
developed methods to synthesize free standing nanowires of many silicides, including the B20 monosilicides (MnSi, FeSi,
CoSi) and their alloys (FexCo1-xSi), many of which display exotic helimagnetic and skyrmion magnetic orderings. Using
Lorentz TEM and magnetotransport measurements, we have found that magnetic Skyrmions are stable over a larger
magnetic field-temperature range in MnSi nanowires compared to bulk crystal and thin films. We have developed a
method based on Andreev reflection spectroscopy to electrically determine the spin polarization ratios and a general
method to measure Hall effect in nanowires. Using the topological Hall effect (THE) of MnSi nanowires, we further
confirmed the extended phase stability and demonstrated the current-driven motion of skyrmions in this extended
skyrmion phase region. These results open up the exploration of nanowires as an attractive platform for investigating
skyrmion physics in 1D systems and exploiting skyrmions in magnetic storage concepts.
INOR 105
Monolayer-protected nanoclusters: Structurally precise building blocks for spintronic applications
Kenneth L. Knappenberger, [email protected], Thomas D. Green, Chongyue
Yi. Florida State University, Tallahassee, Florida, United States
Monolayer-protected nanoclusters (MPCs) are an emerging class of inorganic nanomaterials that can be synthesized and
isolated with atomic precision. Control over MPC composition results, in part, from electron filling of Superatom orbitals,
yielding colloidal metal nanoparticles of specific magic sizes. These synthetic advances overcome many limitations of
inherently heterogeneous colloidal metal nanoparticle syntheses. Recently, post-synthetic electrochemical methods for
manipulating the oxidation state of stable MPCs have been demonstrated. Here, femtosecond timeresolved and magnetooptical spectroscopy studies of a family of MPCs in the 1-2 nm size range will be presented. These results show that the
optical, electronic and magnetic properties of MPCs are extremely sensitive to the electronic configuration of Superatom
orbitals. For example, the magnetic properties of Au25(SR)18, where SR represents an alkanethiol, can be switched
reversibly by oxidative opening of the eightelectron Superatom P orbital. Collective interactions between assembled
MPCs also exhibit spin-dependent magnetic phenomena not present in the isolated building blocks. Magnetic Circular
Dichroism and time-dependent spectroscopy on dimerized 20-atom MPCs reveal inter-particle spin-dependent dynamics
not observed for the monomer. Importantly, these results indicate that the magnetic properties of gold MPCs result from
the electronic configuration of metal-based Superatom orbitals.
INOR 106
Mechanism of dopant incorporation in SrTiO3 bulk powders and colloidal nanocrystals
Keith A. Lehuta, William Harrigan, Kevin R. Kittilstved,
[email protected]. Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts,
United States
SrTiO3 and related titanium-based oxide perovskite semiconductors have attracted interest from researchers for decades
due to their interesting cooperative electronic properties and recently for their potential to exhibit controllable ferroelectric
and ferromagnetic properties when doped with transition metal ions. In this talk, we present our latest results on the
mechanism of dopant incorporation into SrTiO3 bulk powders by a modified sol-gel processing route. Specifically, we will
present evidence of dopant incorporation into the metastable Sr2TiO4 phase prior to conversion to Cr3+-doped SrTiO3. This
Sr2TiO4 phase is the first in the series of alternating SrO(SrTiO3)n layeredperovskite compounds that have interesting
possibilities for spin-based electronics themselves that will also be discussed. Finally, we will present new results on the
synthesis and dopant-specific spectroscopic characterization of the elusive Cr3+-doped SrTiO3 colloidal nanocrystals.
INOR 107
Photomagnetic switching in highly conductive Fe(II) spin-crossover complexes with organic radicals
Hoa Phan1, Shermane Benjamin2, Eden Steven2, James Brooks2, Michael Shatruk1, [email protected]. (1)
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States (2) National High
Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States
Multifuntional materials have received a great deal of attention in the quest for miniaturizing electronic devices and
increasing their efficiency. The combination of different properties in one material should allow the control of one property
through variation of the others. Organic radical conductors and transition metal spin-crossover complexes have been
studied extensively vis-à-vis their appealing physical properties combined with high synthetic tunability. Combining these
two phenomena within one material might offer a possibility to modulate the electrical conductivity by such external stimuli
as temperature or photoexcitation, which are known to cause magnetic state switching in spin-crossover complexes. In
this contribution, we show that incorporation of TCNQ d–·/DCNQId–· organic radicals with fractional oxidation states into
Fe(II) complexes leads to highly conducting hybrid materials that exhibit both temperature- and light-driven spin crossover
(TCNQ = 7,7,8,8-tetracyanoquinodimethane; DCNQI = 7,8-dicyanoquinodiimine). The correlations between spincrossover induced structural changes and transport properties of the materials will be discussed.
INOR 108
Inorganic chemistry of biological nitrogen fixation
Dennis Dean4, Brian M. Hoffman1, [email protected], Dmitriy Lukoyanov1,
Lance C. Seefeldt2, Sudipta Shaw2, Zhiyong Yang3. (1) Chemistry, Northwestern
University, Evanston, Illinois, United States (2) Chemistry and Biochemistry, Utah State
University, Logan, Utah, United States (3) Dept of Chemistry Biochemistry, Utah State
University, Logan, Utah, United States (4) Biochemistry, Virginia Tech, Blacksburg, Virginia, United States
Biological nitrogen fixation — the reduction of N2 to two NH3 molecules — is catalyzed by the enzyme nitrogenase. N2
binds to the active-site multi-metallic cluster in the nitrogenase MoFe protein, the FeMo-cofactor ([7Fe-9S-Mohomocitrate-C]; FeMo-co), and is reduced only after the MoFe protein has accumulated four electrons/protons. This raises
the fundamental question, how can a cluster progressively accumulate four reducing equivalents, given that they are
delivered one-at-a-time from a protein with a fixed and only modestly low reduction potential? As a followup question,
what is the process by these equivalents activate FeMo-co to bind and reduce the extremely stable N2 molecule. But
perhaps the greatest mystery of nitrogenase function has been, why does the enzyme exhibit a limiting stoichiometry that
requires eight reducing equivalents not the six required chemically,
N2 + 8e- +16ATP + 8H+ → 2NH3 + H2 + 16ADP + 16Pi
a stoichiometry that incorporates obligatory generation of H2 upon N2 binding. As the delivery of each electron requires the
hydrolysis of two MgATP, the formation of H2 thus apparently ‘wastes’ 25% of the total energy supplied by the hydrolysis
of ATP. We have discovered connections among such questions, and proposed the answers to these and others, through
enzymological and advanced paramagnetic resonance studies of intermediates formed with nitrogenous substrates, in
combination with fundamental considerations of the redox properties and catalytic reactivity of metal clusters. These
answers are grounded in the ‘hydride chemistry’ of FeMo-co, and rely strongly on parallel studies with the alternate
substrate, C2H2, and on the organometallic chemistry of alkynes and alkenes, as well as on spectroscopic studies of
inorganic biomimetic complexes.
INOR 109
Thermodynamics and mechanism of C-H bond activation by the Cu(III)-OH core
William B. Tolman, [email protected]. Chemistry Dept, University of Minnesota, Minneapolis, Minnesota, United States
Inspired by the unusual active site structures and reactivities exhibited by copper enzymes, we seek to prepare and
characterize synthetic complexes in order to test hypotheses developed to explain the novel functions of the biological
sites.
Monocopper-hydroxo complexes at high oxidation states are proposed intermediates in oxidation catalysis by copper
enzymes and other catalysts, and thus are key targets for synthesis and characterization. Recently, we identified a Cu(III)OH complex supported by a pyridine(dicarboxamide) ligand, and found that it performed hydrogen atom abstraction
reactions at high rates. In this lecture, progress toward understanding the basis for these high rates will be presented.
Evaluation of the thermondynamics of the process, as well as kinetic and mechanistic features of the reactions of Cu(III)OH complexes supported by various ligands will be described.
INOR 110
Ligand switching in the control of cytochrome c redox function
Ekaterina V. Pletneva, [email protected]. Chemistry, Dartmouth
College, Etna, New Hampshire, United States
Cytochrome c (cyt c) is a small mitochondrial protein with critical functions in oxidative phosphorylation and apoptosis. The
iron ligands His18 and Met80 as well as the covalent attachment of the heme group are important for the fold and the
relatively high redox potential of this electron-transfer (ET) protein. However, environmental factors, including biologicallyrelevant changes in pH and membrane composition, alter the heme ligation state affecting the protein redox activity. The
Met80 to Lys73/79 switch has been suggested to control the directionality of cyt c ET with cyt c oxidase. A similar ligand
switch as well as a more substantial protein unfolding upon cyt c interactions with cardiolipin (CL)-rich membranes have
been implicated in triggering the increase in the protein peroxidase activity, which is instrumental for membrane
permeabilization during apoptosis. Analysis of dye-to-heme distance distributions in fluorescently labeled cyt c and their
time-dependent evolution has revealed the nature of the CL-bound species and the mechanism of their formation.
Mutations targeting the intraprotein hydrogenbonding network have identified the likely triggers of the Met-to-Lys ligand
switch. The Lys-ligated protein is as compact as the native cyt c but, owing to perturbations in the polypeptide packing, its
peroxidase activity is higher. Building on our understanding of protein folding and heme coordination principles, we
employ the cyt c scaffold to engineer a variety of switchable proteins where interchanging ligands are Met, Lys, Cys, and
His. Redox reactions in these proteins are gated by the ligand exchange and accompanying protein rearrangements.
INOR 111
Raman spectroscopy and computation reveal how hemoglobin controls oxygen
affinity
Thomas G. Spiro, [email protected]. Chemistry, Univ. of Washington, Seattle, Washington, United States
New experimental and computational approaches are revealing the molecular mechanism responsible for cooperative
binding of oxygen by hemoglobin. Pump-probe UV resonance Raman spectroscopy establishes that the transition
between the R and T quaternary structures occurs in two distinct steps, successively involving the hinge and switch
contacts at the a1b2 subunit interface1. This finding supports the sequential quaternary pathway computed by Karplus and
coworkers using the conjugate peak refinement method2. Slowing of quaternary motions by gel encapsulation has
permitted the further discovery that prior tertiary evolution shifts the stretching frequency of the bond connecting the heme
Fe to the proximal histidine residue between values associated with high and low oxygen affinity states, a finding
confirmed by computation using the PELE conformational search program of Gualar and coworkers 3. This result
establishes the occurrence of alternative high- and low-affinity tertiary structures within each quaternary structure,
consistent with the recent tertiary two-state model of Eaton and coworkers4. The new view of cooperative binding is that
affinity is determined by tertiary conformation, within the constraints of a given quaternary structure, and that the evolving
tertiary populations drive the quaternary change, along a pathway that is not a simple interpolation between the alternative
quaternary structures. These characteristics may be relevant to other multi-subunit allosteric proteins.
1.
Balakrishnan, G.; Case, M. A.; Pevsner, A.; Zhao, X.; Tengroth, C.; McLendon, G. L.; Spiro, T. G. Journal of
molecular biology 2004, 340, 843.
2.
Fischer, S.; Olsen, K. W.; Nam, K.; Karplus, M. Proceedings of the National Academy of Sciences of the United
States of America 2011, 108, 5608.
3.
Jones, E. M.; Balakrishnan, G.; Spiro, T. G. J Am Chem Soc 2012, 134, 3461 4. Henry, E. R.; Bettati, S.;
Hofrichter, J.; Eaton, W. A. Biophysical Chemistry 2002, 98, 149.
INOR 112
Structure/function correlations over non-heme iron enzymes
Edward I. Solomon, [email protected]. Chemistry Dept MC 5080,
Stanford University, Stanford, California, United States
Non-heme iron enzymes either activate substrate using a ferric center or dioxygen using a ferrous site. The latter has
been extremely difficult to study. Thus we have developed new spectroscopic methodologies that provide geometric and
electronic structural insight into the ferrous center, its interaction with cosubstrates for activation of dioxygen, and the
nature of the Fe(III)-OOH and Fe(IV)=O intermediates generated in this reaction.
INOR 113
Singlet fission in carotenoid aggregates and dimers
Michael J. Tauber, [email protected]. Chemistry and Biochemistry, University of California San Diego, La Jolla,
California, United States
In recent years, it has been recognized that an intermolecular mechanism known as singlet fission could increase the
maximum thermodynamic energy conversion efficiency of certain photovoltaics by as much as 50%. Singlet fission is a
spin-allowed process whereby one singlet excited state creates a pair of triplets on neighboring molecules. We have
investigated the dynamics of singlet fission within a variety of carotenoid assemblies. The systems include aggregates
(nanoparticles) composed of thousands of carotenoids, or small multimers, or covalently-bound dimers. The excitedstate
dynamics of these systems are probed with transient absorption spectroscopy, and time-resolved resonance Raman
spectroscopy. Triplet formation occurs within one picosecond for all carotenoid assemblies of our experiments, and the
yields approach 200% (i.e. two triplets per absorbed photon). The application of the carotenoid assemblies to
photovoltaics is probably limited because of rapid annihilation of the triplet excitons, as well as their relatively low energy.
Nevertheless, these studies provide fundamental insights into the singlet fission process.
INOR 114
Probing pathways of excited-state proton-coupled electron transfer reaction
Jillian L. Dempsey, [email protected], Thomas T. Eisenhart, James C.
Lennox, William C. Howland. CB 3290, University of North Carolina, Chapel Hill, North Carolina, United States
In contrast to proton-coupled electron transfer (PCET) reactions between molecules in their ground states, comparatively
little is known about PCET reactions with electronically excited molecules. In order to reveal the pathways by which light
absorption and proton/electron transfer can be integrated, we are examining excitedstate PCET reactions in a series of
model systems. Using transient absorption spectroscopy, we have obtained key mechanistic and kinetic information about
this class of light-driven reactions.
INOR 115
New sensitizers for solar hydrogen production
Randy Sabatini2, Bo Zheng3, William T. Eckenhoff6, Alexandra Orchard7, Kacie Liwosz7, David Watson4, Michael Detty7,
Richard Eisenberg5, David W. McCamant1, [email protected]. (1) Univ of Rochester, Rochester, New
York, United States (2) University of Rochester, Rochester, New York, United States (3) Chemistry
Department, University of Rochester, Rochester, New York, United States (4) Dept of
Chemistry, Buffalo, New York, United States (5) Dept of Chem, Univ of Rochester,
Rochester, New York, United States (6) Chemistry, Hobart William Smith College,
Geneva, New York, United States (7) Chemistry, SUNY Buffalo, Buffalo, New York, United States
Our labs have developed new sensitizers for solar hydrogen production and characterized important photophysical
characteristics of those dyes with hydrogen production assays and ultrafast transient absorption spectroscopy.
Specifically, we are developing a series of chalcogenorhodamine dyes that absorb from 500-600 nm in monomeric form
and from 400-620 nm when in a solvent environment that induces aggregation. In conditions for solar hydrogen
production, the dyes bind to titanium dioxide in monomeric form and tend to perform slow electron transfer to the
semiconductor. Hence, these dyes benefit from the incorporation of Se, which induces rapid intersystem crossing to the
triplet state, preserving the excitation energy long enough for electron injection to occur. We have also developed a
molecular dyad, in which absorption occurs on the strongly absorbing Bodipy chromophore, before energy transfer to a
Pt(diimine)(dithiolate) occurs and subsequent electron transfer into a semiconductor scaffold.
INOR 116
Toward spying on individual working catalyst molecules
Randall H. Goldsmith, [email protected]. Chemistry, University of Wisconsin
Madison, Madison, Wisconsin, United States
Single-molecule spectroscopy is a powerful tool for the mechanistic investigations of chemical and biological dynamics
because unsynchronized processes can be directly observed. However, the traditional reliance upon fluorescence for
single-particle measurements limits such investigations to systems where the target is fluorescent, a difficult requirement
for organometallic catalysts. We present our progress toward realizing our goal of being able to spy on individual working
catalyst molecules, including use of optical microresonators as extremely sensitive probes of local electronic structure.
INOR 117
Exploring the mechanism of small molecule metal ion chelators as chemotherapeutic agents against pathogenic
bacteria
Thiago Santos3, Maoquan Zhou3, Matthew Lammers3, Madhusudan Rajendran3,
Katherine Hurley1, Ye-Jin Eun3, Douglas B. Weibel2, [email protected]. (2)
Departments of Chemistry, Biochemistry, and Biomedical Engineering, University of
Wisconsin Madison, Madison, Wisconsin, United States (3) Department of
Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States
Divin is a recently discovered, broad-spectrum small molecule antibiotic that inhibits bacterial cell division by preventing
the localization of division machinery to the division plane and impeding peptidoglycan remodeling. In addition to its
bacteriostatic activity against rapidly dividing bacteria, divin is a potent chemotherapeutic agent for treating biofilms.
Recent biochemical and molecular characterization of the mechanism of action of divin demonstrates that it is an
intracellular metal chelator that selectively disrupts bacterial iron homeostasis in vivo and inhibits late stages of bacterial
cytokinesis. Consistent with its chelation properties, divin-treated bacterial cells have low levels of intracellular iron and
activate global iron-starvation response. Excess iron antagonizes the biological activity of divin in vivo and overexpression
of iron transporters reduces bacterial sensitivity to divin. This talk characterizes the chemical, biochemical, and cell
biological activity of this family of small molecules, builds the first biochemical connection between metal chelators and
bacterial cell division, and provides insight into new classes of antibiotics that target bacteria by sequestering essential
metal ions.
INOR 118
Thermodynamic and kinetic measurements of cation exchange in chalcogenide nanocrystals by isothermal
titration calorimetry
Nicholas Sturgis1, Robert M. Rioux2,3, [email protected]. (1) Chemical Engineering, Pennsylvania State University,
University Park, Pennsylvania, United States (2) Dept of
Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania,
United States (3) Chemistry, Pennsylvania State University, University Park, Pennsylvania, United States
A variety of methods have been developed to synthesize nanomaterials of various sizes and composition. Often these
methods rely on a hot injection synthesis scheme, but these are generally developed on a case-by-case basis and not
appropriate for all compositions of matter. Cation exchange of nanocrystals is a useful method for the modification of welldefined template materials into a number of derivatives with controlled composition and crystallinity that are otherwise
unavailable via traditional synthetic methods. While a general thermodynamic understanding of the processes that occur
in cation exchange is established, very little quantitative data of the thermodynamics and kinetics of cation exchange at
the nanoscale have been published. These measurements are hindered by the fact that cation exchange occurs in
solution at a buried solid-liquid interface. Traditional techniques used to characterize cation exchange primarily probe
structural and optical properties which provide no information on the thermodynamics of cation exchange.
Recently, we have applied isothermal titration calorimetry (ITC) to study the thermodynamics of CdSe cation exchange.
These ITC experiments involve the incremental titration of a cation source into a cell containing CdSe nanocrystals and
measurement of the heat evolved. With incremental titration, the enthalpy and the equilibrium constant for a reaction are
simultaneously measured. We have applied this method to measure how nanocrystal size, cation source (Ag, Cu), and
temperature impact the thermodynamics of the reaction.
Additionally, the kinetics of cation exchange can be determined from the calorimetry data, and compared directly to a
more traditional kinetic measurement technique, stopped-flow spectroscopy. We will demonstrate that the kinetics are
influenced by expected variables, such as temperature, but the particle size is a major influence on the observed kinetics
of cation exchange.
We will summarize the similarities and differences between the thermodynamics and kinetics of cation exchange in
nanoscale and bulk materials. The fundamental thermodynamic and kinetic data measured in this work will enable the
development of robust synthesis-structure relationships in cation-exchange that will enable the development of nanoscale
materials with tailored properties for catalysis, photonics and electronics.
INOR 119
Luminescent copper-doped semiconductor nanocrystals
Kathryn E. Knowles, [email protected], Heidi D. Nelson, Patrick J.
Whitham, Daniel R. Gamelin. Chemistry, University of Washington, Seattle, Washington, United States
Copper-doped semiconductors have been used as phosphors for nearly a century. Recently, attention has turned to the
interesting new optical properties that can be obtained in colloidal copper-doped semiconductor nanocrystals (NCs).
Photoluminescence (PL) in copper-doped semiconductor NCs originates from a charge transfer transition involving an
electron in the conduction band and a (formally) Cu2+ ion that is generated upon trapping of the photogenerated hole by a
Cu+ dopant. This recombination mechanism results in a broad PL spectrum that is significantly lower in energy than the
semiconductor band gap, and tunable by varying the size and composition of the NC. This tunability, combined with the
minimal overlap of the absorption and PL spectra, makes copper-doped semiconductor NCs attractive phosphors for
numerous applications in optical imaging and spectral conversion. To optimize these materials as phosphors, it is
important to understand their electronic structures and photophysical properties in detail. This talk will present data from a
combination of continuous wave and time-resolved measurements investigating the spectroscopic properties of copperdoped semiconductor NCs. These data elucidate details of the electronic structures of these materials, with particular
focus on properties of the luminescent excited state in various copper-doped lattices.
INOR 120
Metal nanoparticles trapped in unfolded proteins: Synthesis, characterization, and unique materials properties
Matthew R. Hartings1, [email protected], Douglas Fox2, Abigail E. Miller3. (1)
Chemistry, American University, Gaithersburg, Maryland, United States (2) American
University, Washington, District of Columbia, United States (3) Chemistry, American University, Washington, District of
Columbia, United States
Biomineralization produces a variety of materials geometries in Nature and does so while arranging proteins on length
scales that range from nanometers to centimeters. Using several facile biomineralization protocols, we have produced
new biocompatible materials that incorporate transition metal and semiconductor nanoparticles within unfolded proteins.
These materials include gold nanoparticles, quantum dots, iron oxide particles in protein microgel spheres, and 1-D fibers
of gold nanoparticles within a matrix of unfolded proteins. During this presentation, I will discuss the synthesis,
characterization, and potential uses for these materials.
INOR 121
Molecular studies of gas clathrate hydrates
Carolyn A. Koh, [email protected]. Colorado School of Mines, Golden, Colorado, United States
Gas clathrate hydrates are crystalline compounds containing a network of hydrogenbonded water cages that can trap
small gas molecules. Understanding the structureproperty relations of gas clathrate hydrates is important in energy
storage of fuels such as methane or hydrogen [1]. This paper reviews the application of molecular tools including neutron
diffraction to investigate the formation, decomposition, and structure properties of gas clathrate hydrates. Neutron
diffraction studies can be performed using high pressure, variable temperature reactor vessels, which enables in-situ
structure analysis to be performed. In-situ measurements and analysis are needed to advance our understanding of the
mechanisms of gas hydrate formation and decomposition. This paper presents examples in which neutron diffraction
methods have been applied to investigate the formation and decomposition processes and structural characteristics of
methane, propane, and binary hydrogen hydrates.
References
[1] Sloan, E.D. & Koh, C.A., Clathrate Hydrates of Natural Gas, 3rd Ed. CRC Press, 2007.
INOR 122
Fueling the future: Safe, dense, reversible hydrogen storage in hybrid nanomaterials
Jeff Urban, [email protected]. Berkeley Labs, Berkeley, California, United States
Historical trends have shown gradual decarbonization of our fuel sources over hundreds of years, the ultimate endpoint of
which is hydrogen. Hydrogen fuel cell applications offer safe, emissions-free energy and all of the major auto
manufacturers have made commitments to the technology. However, despite this technological push, there remain
fundamental scientific issues that have delayed widespread adoption of the technology. In this talk, I’ll discuss ongoing
work in my group to develop hybrid nanomaterials approaches to safe, energy-dense, and reversible hydrogen storage in
metallic Magnesium nanocrystals and 2D hybrids. I will specifically highlight advances toward room-temperature storage
and the atomic limit of selective encapsulation.
INOR 123
Development of metal hydrides for high temperature thermochemical energy storage
Ewa Ronnebro, [email protected]. MSIN K2-03, Pacific Northwest National Lab, Richland, Washington, United
States
Thermal energy storage (TES) is an emerging technology market which recently has been identified as a key enabling
storage method for more efficient energy use in heating and cooling applications. Key challenge is that the materials
currently used are not efficient enough and of too high cost. TES can be used in various areas, including with renewable
energies. State of the art of TES for concentrating solar power (CSP) is molten salt storage, but energy storage density if
low. Other requirements to consider for heat storage are cost, charging rate, reversibility and long cycle life of 30 years.
The materials with highest energy density are based on thermochemical reactions and include metal hydrides and metal
oxides. We are developing a dual bed metal hydride heat storage based on reversible hydrogen absorption/desorption
reactions. The technical concept is based on a system that consists of a high-temperature (HT) metal
hydride bed for heat storage operating at ≥675°C and 4.5 bar pressure connected to a second metal hydride bed
operating at low temperature (LT) which is used to store H
INOR 124
Water-mediated cooperative migration of chemisorbed hydrogen on graphene Yufeng Zhao1,
[email protected], Thomas Gennett 2. (1) National Renewable
Energy Laboratry, Golden, Colorado, United States (2) MS3213, NREL, Golden, Colorado, United States
Hydrogen chemisorption on graphene has attracted considerable attention because it provides an ideal matrix for
investigating the fundamental interactions on an idealized surface. Conventional theoretical investigations have shown
that chemisorbed H atoms on graphite surface, or one side of a graphene sheet, are highly immobile and the energetics of
the diffusion barrier is much higher than that for the desorption of recombined H 2 molecules. However, recent
experimental results on hydrogen storage in carbon infer the opposite conclusion: in carbon areas away from a catalytic
centers, no noticeable H recombination can be observed; whereas, diffusion of chemisorbed H away from the catalyst
particle apparently happens to form very stable C-H interactions. Reconciliation of the two opposite observations was our
theoretical challenge.
In our recent paper, we address the above issue through systematic density-functionaltheory calculation. Unlike the
conventional experimental study of H chemisorption using atomic H source, the hydrogen storage uses molecular
hydrogen source; therefore, the chemisorption state must be in a much lower energy level. In order to lower the total
energy, each chemisorbed H atom must be paired up with another H atom on the opposite side of the graphene sheet.
The two H atoms in a pair are strongly correlated and it is found they must move cooperatively. In this situation,
recombination of H atoms on the same side is mostly suppressed because each recombination breaks two Hbonded pairs
and is energetically very unfavorable. Surprisingly, we found that, H migration can actually happen at room temperature
through a cooperative motion of H pairs when they are mediated by water molecules. This study is important for both
hydrogen storage technology and organic chemistry in terms of C-H bond activation.
INOR 125
Spectroscopic studies of proton-coupled electron transfer in the mechanism of H2 activation by [FeFe]hydrogenases
David W. Mulder1, Michael W. Ratzloff1, Maurizio Bruschi2, Claudio Greco2, Yisong
Guo3, Evangeline Koonce4, John W. Peters4, Paul W. King1, [email protected]. (1)
Biosciences Center, National Renewable Energy Lab, Golden, Colorado, United States
(2) Department of Earth and Environmental Sciences, University of Milano-Biocca,
Milan, Italy (3) Department of Chemistry, Carnegie Mellon University, Pittsburgh,
Pennsylvania, United States (4) Department of Chemistry and Biochemistry, Montana State University, Bozeman,
Montana, United States
Proton-coupled electron transfer (PCET) is a fundamental process at the core of oxidation-reduction reactions for energy
conversion in biology. The [FeFe]hydrogenases catalyze reversible H 2 activation through a unique metallocofactor, the
Hcluster, that is finely tuned by the surrounding protein environment to undergo fast PCET transitions. The H-cluster is
comprised of a [4Fe-4S]H cubane subcluster linked by cysteine (Cys) to an organometallic [2Fe] H subcluster with CO and
CN- ligands. Defining the PCET steps that coordinate redox transitions at the H-cluster have been difficult to resolve
experimentally due to inherently fast (≥104 s-1) enzyme turnover. We have recently investigated the effects of a Cys→Ser
substitution at a conserved site (169) in the PT network of Chlamydomonas reinhardtii [FeFe]-hydrogenase (CrHydA1).
Cys169 lies proximal to, and mediates proton exchange with, the H-cluster. The Cys169Ser variant of CrHydA1 showed a
substantial decrease in catalytic activity, and the electron paramagnetic resonance (EPR) and Fourier transform infrared
(FTIR) spectroscopic properties revealed enrichment of unique H-cluster states under reducing conditions. Reduction with
H2 or sodium dithionite led to an EPR spectra with signals consistent with a reduced [4Fe-4S]H1+ subcluster, and FTIR
spectra that showed upshifts of vCO modes to energies consistent with an increase in oxidation state of the [2Fe]H
subcluster. Density Functional Theory analysis corroborated this redox transition and provided additional insights on shifts
in [2Fe]H vCO modes during H2 activation. In contrast to wild-type CrHydA1, spectra associated with the so-called
"reduced" states
(Hred and Hsred) were less populated in the Cys→Ser variant, demonstrating that the exchange of -SH to -OH alters how
the H-cluster equilibrates among reduced states of the catalytic cycle under steady-state conditions. This presentation will
summarize the results in the context of a model for H2 activation by [FeFe]-hydrogenase and the role of proton-transfer in
the catalytic cycle.
INOR 126
Molecular electrocatalysts for the oxidation of hydrogen: Pendant amines as proton relays
R Morris Bullock, [email protected], Tianbiao Liu, Jonathan M. Darmon, Elliott
B. Hulley, Monte Helm. Pacific Northwest National Laboratory, Richland, Washington,
United States
Solar and wind are carbon-neutral, sustainable energy sources, but their intermittent nature requires reliable energy
storage. Catalysts that efficiently interconvert between electrical energy and chemical bonds (fuels) are needed for
sustainable, secure energy in the future. Electrocatalysts based on inexpensive, earth-abundant metals (“Cheap Metals
for Noble Tasks”) are needed since low-temperature fuel cells generally use platinum, an expensive, precious metal.
Nickel catalysts for production of H2 and oxidation of H2 have been developed using pendant amines as proton relays.
Iron complexes with pendant amines on the diphosphine ligand are also being studied, showing that it is possible to
rationally design catalysts based on abundant, inexpensive metals as alternatives to precious metals. Organometallic
Fe(II) complexes derived from CpFe(diphosphine)H, with pendant amines in the diphosphine ligands are electrocatalysts
for oxidation of H2 (1 atm) at room temperature. The equilibrium between a Fe(H 2) dihydrogen complex and the product of
heterolytic cleavage can be altered by changing the substituents on the diphosphine ligands. The product of heterolytic
cleavage has a Fe-H • • • H-N dihydrogen bonding interaction between the hydridic Fe-Hδ- and the acidic N-Hδ+ on the
pendant amine. Mn(I) complexes containing pendant amines on the diphosphine ligand exhibit unusually fast (>107 s-1 at
22 °C) reversible heterolytic cleavage of H2.
This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center
funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
INOR 127
Hydrogen fuel cell electric vehicles: new possibilities?
Yuyan Shao, [email protected]. MS K2-12, Pacific Northwest National
Laboratory, Richland, Washington, United States
It has been widely recognized that decarbonization of transport sector is an important strategy to stabilize global climate.
Currently, the transport sector accounts for about 27% of global final energy consumption and is expected to increase
50% by 2035; it emits about 6.3 Gt CO2 or 24% of the total global CO2 emission, second only to power generation sector
(40%). To electrify transportation is on the top of the few choices to achieve that goal and probably the only choice for
zero emission at use site. Developing hydrogen fuel cell electric vehicles (FCEV) is a strategic direction to achieve that
goal. However, it has been hindered mostly by H2 infrastructures. It is also competing with other technologies such as
battery electric vehicles (BEV) in terms of attracting resources for its development. Recently, the U.S. Energy Department
launched a new public-private partnership -H2USA- with the aim to advance hydrogen infrastructure, which is believed to
re-energize FCEV development. In this talk, we will discuss some new possibilities of developing hydrogen FCEVs with a
focus on cost analysis, resource constraint of key materials, infrastructure, etc.
INOR 128
Efficient cyclometalated platinum and palladium complexes for displays and lighting applications
Jian Li, [email protected]. Materials Science Engineering, Arizona State University, Tempe, Arizona, United States
The successful development of alternate low cost technology for current lighting devices will have a significant impact on
the U. S. economy and national security. White organic light emitting diodes (OLEDs) with potentially high power
efficiency are considered as strong candidate for the next generation of illumination devices. Moreover, the use of
environmentally benign organic materials in white OLEDs and their potentially low fabrication cost makes them an
attractive technological prospect. In this presentation, we will discuss our continuing efforts on the design, synthesis and
characterization of novel platinum and palladium complexes for displays and lighting applications. The photo-physics,
electrochemistry and electroluminescent properties of these novel metal complexes will be discussed. The rational
molecular design enables us to develop cyclometalated Pt and Pd complexes with both photon-to-photon (in thin film) and
electron-to-photon (in device settings) conversion efficiency close to 100% for OLED applications. We will also discuss
our approaches to achieve high efficiency and stable white OLED based on such materials.
INOR 129
Solvent-dependent fluorescence of substituted quinoxalines
Scott P. Sibley, [email protected]. Goucher Colg, Baltimore, Maryland, United
States
A new quinoxaline-containing molecule has been synthesized that exhibits extremely solvent-dependent fluorescence.
The behavior of the fluorescence is consistent with the formation of a twisted intramolecular charge transfer (TICT) state
for this molecule in polar solvents. The photodegredation behavior of the molecule in various solvents has also been
studied. Derivitization of this molecule, the effects of substituents upon the fluorescence behavior, and possible molecular
probe applications will also be discussed.
INOR 130
Excitons and OLEDs: You can’t live with them and you can’t operate without them
Stephen Forrest, [email protected]. University of Michigan, Ann Arbor, Michigan,
United States
A persistent challenge with optoelectronic devices based on organic materials is overcoming their relatively short
operational lifetime compared with inorganic semiconductor devices. This has been a limiting factor in their applications to
displays and lighting based on OLEDs, and in organic photovoltaic (OPV) cells. We have found that the intrinsic source of
degradation is the presence of high energy excitons 1, 2 that often dissipate their energy by breaking bonds, and hence
destroying the active electronic molecular species. Unfortunately, excitons are also responsible for all of the beneficial
optoelectronic properties of such devices. The question then becomes: can we enhance the benefits of excitons without
leading to device degradation? In this talk we discuss the achievement of long-lived blue electrophosphorescent OLEDs
(PHOLEDs); a problem that has prevented their widespread use for over a decade in spite of their very high emission
efficiencies. We demonstrate a blue PHOLED that results in a lower exciton density compared to a conventional device
without sacrificing efficiency. A lifetime of 616±10 hrs (time to 80% of the 1000 cd/m 2 initial luminance) with chromaticity
coordinates of [0.15, 0.29] is observed, representing a ten-fold lifetime improvement over a conventional blue PHOLEDs 3.
Prospects for increasing PHOLED lifetime by another factor of 10 – 100 in view of our understanding will be discussed.
1. N. C. Giebink, B. W. D’Andrade, M. S. Weaver, P. B. Mackenzie, J. J. Brown, M. E.
Thompson and S. R. Forrest, J. Appl. Phys. 103, 044509 (2008).
2. X.Tong, N. Wang, M. Slootsky, J. Yu and S. R. Forrest, Solar Energy Materials & Solar Cells 118, 116 (2013).
3. Y. Zhang, J. Lee and S. R. Forrest, Nature Commun., Nature Communications, 5, 5008, DOI: 10.1038/ncomms6008
(2014).
INOR 131
Synthetic control of photoinduced structural change and dual emission of phosphorescent molecular butterflies
Biwu Ma, [email protected]. Florida State University, Tallahassee, Florida, United States
We report a series of butterfly-like phosphorescent pyrazolate bridged platinum binuclear complexes with controlled
photoinduced structural change and dual emission. All these molecular butterflies can undergo molecular structure
change in which the Pt– Pt distance shortens upon photoexcitation, which leads to the formation of two distinct excited
states and dual emission in the steady state, that is, greenish-blue emission from the high-energy excited state at the long
Pt–Pt distance and red emission from the low-energy excited state at the short Pt–Pt distance. The manipulation of
photoinduced structural change and dual emission can be realized by controlling the bulkiness of the cyclometallating
ligand and pyrazolate bridging ligand. By introducing bulky groups into the cyclometallating ligand, the photoinduced Pt-Pt
distance shortening can be slowed down, resulting in dual emission with higher greenish-blue/red ratio, while introducing
bulky groups into the pyrazolate bridges can speed up the photoinduced structural change, resulting in dual emission with
higher red/greenish-blue ratio. Computational studies suggest that these molecular butterflies have various energy
barriers for the photoinduced structural change and therefore different excited state dynamics. Overall, by careful control
of the molecular structure, we have obtained colorful molecular butterflies flapping wings at various frequencies under
light.
INOR 132
Exploiting nonradiative decay of cyclometalated iridium complexes to perform in situ analysis of degradation
products in OLEDs
Peter I. Djurovich, [email protected]. Chemistry, University of Southern California, Los Angeles, California, United
States
Cyclometalated iridium complexes, e.g., Ir(2-phenylpyridyl)3, are widely used as phosphorescent dopants in organic light
emitting diodes (OLEDs) due to their highly efficient luminescence. The photoluminescence efficiency (PLE) from these
complexes can approach 100%, yet many derivatives, particularly blue emitters, have values that are significantly lower
(PLE < 1%) at room temperature. The PLE is mainly dependent on the type of process that contributes to the nonradiative
decay. Phosphorescence from these compounds typically originates from a mixed ligand-centered/metal-to-ligand charge
transfer excited state. Nonradiative deactivation of the excited state occurs through several distinct mechanisms; selfquenching, direct vibrational decay to the ground state, or thermal population to ligand field states. The third mechanism
becomes dominant for complexes with high (blue) triplet energies and can lead to decomposition of the complex due to
loss of ligand(s). We show that the last mechanism can used to study the formation of degradation products in OLEDs
through appropriate design of the device architecture. This method is employed to serve as an in situ assay for the
stability of phosphorescent dopants for use in OLEDs.
INOR 133
High efficiency phosphorescent OLEDs
Jason Brooks, [email protected]. Universal Display Corporation, Ewing, New Jersey, United States
Heavy atom induced phosphorescence is an attractive means for creating high efficiency OLED devices. For most organic
compounds, emission from the triplet state is a formally spin forbidden process that is weakly emissive at room
temperature and has a long excited state lifetime on the order of milliseconds or even seconds. However, heavy atoms
are known to exert a strong spin-orbit coupling effect on electronic transitions that converts singlet excited states to the
triplet state with high efficiency. Devices incorporating these heavy atom phosphorescent emitters have been shown to
approach the internal quantum efficiency limit of 100%.
In particular, iridium complexes based on the 2-phenylpyridine ligand have demonstrated high efficiencies and long
lifetimes as emissive materials incorporated in electroluminescent devices. The Universal Display Corporation team has
further developed phosphorescent materials and device structures and has demonstrated high efficiency (>20% external
quantum efficiency) green, red and blue emitting devices with red and green long lifetimes at display level brightness
(>100,000 hours) thus making red and green commercially viable for display applications. Progress on blue PHOLED
lifetime is accelerating towards commercial entry levels.
Direct carrier trapping on the dopant has been described as an important mechanism for high efficiency phosphorescent
devices. Dopant charge trapping is a result of large energetic offsets between the highest occupied molecular orbital
(HOMO) or lowest unoccupied molecular orbital (LUMO) levels of the host and dopant. In addition, charge transport
materials that are adjacent to the emissive layer can affect device efficiency by shifting the zone of recombination or
through the blockage of charge. In this paper, we will present device design and results which enable a high efficiency
and lifetime product to demonstrate the strong performance of phosphorescent OLEDs.
INOR 134
Stoichiometric and catalytic reactivity based on late-metal/main-group cooperation
Matthew T. Whited, [email protected]. Department of Chemistry, Carleton
College, Northfield, Minnesota, United States
The coordinative and redox flexibility of organosilicon ligands makes them ideal partners for late transition metals in
potential cooperative applications. Here I will present recent findings from our research group on the utility of silylamides
as nitrene-group and nitrogen-atom delivery agents as well as cooperative processes occurring at late-metal silyl and
silylene complexes supported by rigid pincer-type ligands.
INOR 135
Investigating the trap state landscape of cadmium halide-treated CdSe nanocrystals
Richard L. Brutchey, [email protected]. Department of Chemistry, University of
Southern California, Los Angeles, California, United States
Solution processing of semiconductor thin films offers the potential for reduced cost and high throughput device fabrication
as compared to traditional processing techniques. One way that such thin films can be solution deposited is by the use of
colloidal semiconductor nanocrystal inks. Nanocrystal-based solar cells derived from such inks have recently reached
power conversion efficiencies > 8% as a result of improved surface passivation strategies. The enabling chemistry behind
this improved performance has been surface treatment with halides or metal halides. Aside from the obvious improvement
in transport properties stemming from decreased interparticle separation associated with these halide or metal halide
ligand shells, less is understood about the influence of such ligands on the electronic structure of the nanocrystals. To
date, a systematic investigation into the effects of metal halide surface ligands on CdSe nanocrystals is lacking. With this
in mind, we developed a simple and robust colloidal route for the installation of halide ligands on the surface of CdSe
nanocrystals using CdX2 (X = Cl, Br, I). Photoelectrochemical measurements on solution-cast nanocrystal thin films reveal
a striking influence of surface cadmium halide on photocurrent response, with mildly annealed, CdCl 2-treated CdSe
nanocrystal films showing the greatest enhancement in photocurrent to above band gap illumination. The strong
dependence of photoresponse on surface halide is investigated using ultrafast transient absorption, time-resolved
photoluminescence, and surface photovoltage spectroscopies. From these measurements, we develop a model that
accounts for electron and hole trapping at the nanocrystal surface in which annealed, CdCl2-treated CdSe nanocrystal
films undergo a thermal removal of electron trap states without the introduction of deep hole traps, whereas analogous
CdBr2 and CdI2 treatments introduce deeper hole traps that prevent surface passivation and large photoresponse.
INOR 136
Charge dynamics in next-generation energy conversion materials
Cody W. Schlenker, [email protected]. Chemistry , University of Washington, Seattle, Washington, United States
We study charge generation and recombination in organic and hybrid solar cell materials by combining spectroscopy,
time-resolved device measurements, and thin film structural probes. We describe how recombination via low-lying triplet
excited states at organic/organic interfaces can be controlled by a balance between energy landscape and hierarchical
film structure. Our recent work also focusses on using spectroscopic tools with temporal and structural sensitivity to better
understand the dynamics of charge generation in emerging solar cell materials, such as hybrid organo metal halide
perovskites. Our results bring new insight into the molecular properties that determine charge carrier dynamics and
suggest new strategies for materials design focused on kinetically suppressing recombination losses.
INOR 137
Photon upconversion and photocurrent generation via self-assembled bilayers on metal oxide surfaces
Kenneth Hanson, [email protected], Sean P. Hill, Tanmay Banerjee. Chemistry and Biochemistry, Florida State
University, Tallahassee, Florida, United States
Photon upconversion—combining two or more low energy photons to generate a higher energy excited state—is an
intriguing strategy for increasing the maximum theoretical solar cell efficiencies from 31% to greater than 40%. Molecular
upconversion, via triplettriplet annihillation (TTA), is particularly appealing strategy to achieve this goal because it can
occur even under low intensity, non-coherent, solar irradiation. However, there are currently no examples of directly
extracting charge from an upconverted state. In this presentation we introduce self-assembled bilayers on metal oxide
films as a new structural motif to facilitate molecular photon upconversion. More importantly we demonstrate that this
interface can be used to directly extract charge and generate photocurrent from the TTA unconverted state.
INOR 138
Thermal and photochemical reactions mediated by water-soluble host-guest supramolecular systems
Robert G. Bergman1,2, [email protected]. (1) Chemistry, University of
California, Berkeley, Berkeley, California, United States (2) Chemical Sciences, Lawrence Berkeley National Laboratory,
Berkeley, California, United States
In a collaborative study being carried out by the R. G. Bergman and K. N. Raymond research groups, several organic and
organometallic reactions have been shown to occur in the cavities of self-assembled water-soluble tetrahedral chiral
clusters (”nanovessels”). This talk will focus on stoichiometric and catalytic reactions that occur within the cavities of these
species, induced both thermally and photochemically.
INOR 139
Cation-modulated hemilability in pincer-crown ether complexes
Alexander J. Miller, [email protected], Matthew R. Kita, Jacob B. Smith. Dept of Chemistry, University of North
Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Ligand hemilability can confer upon catalysts an unusual combination of stability and activity, but tuning hemilability is
difficult. Pincer ligands bearing pendent crown ether macrocycles offer a unique strategy for fine-tuning hemilability
through cation-crown interactions. Hydrogen activation by iridium(III) complexes affords proof-of-principle: the reaction
rate can be tuned based on the choice of alkali metal cation catalyst, with rates enhanced by more than two orders of
magnitude. Design principles that have emerged in extending cation-tunable reactivity to catalytic reactions will be
discussed.
INOR 140
Redox reactions of nanoscale oxide materials: Thermodynamics and kinetics of hydrogen-atom and protoncoupled electron transfer processes
James M. Mayer2, [email protected], Carolyn N. Valdez2, Miles N. Braten2,
Jennifer Peper4, Ashley Soria3, Jessica A. Johnson3, Daniel R. Gamelin1, Alina M.
Schimpf5, Mitsuhashi Ryoji2, Chih-Chin Tsou2, Delina Damatov2, Hayle Larson2. (1)
Chem Dept, Univ Washington, Seattle, Washington, United States (2) Yale University,
New Haven, Connecticut, United States (3) University of Washington, Seattle, Washington, United States
Metal oxide materials have long been used as catalysts and catalyst supports. In addition to the traditional focus on their
acid/base properties, many metal oxides can undergo redox change, for instance in ‘hydrogen spillover.’ This presentation
will explore the addition of hydrogen – protons and electrons – to nanoscale metal oxides. It will described the chemistry
of soluble nanoparticles (quantum dots) of zinc oxide and titanium dioxide, in nonpolar organic solvents and in aqueous
solution/suspension. The different thermodynamic affinities of different oxides for electrons, protons, and hydrogen atoms
are being explored. In organic media, we are studying the relationship between the numbers of electrons and protons
added, which is related to the change in effective redox potential with proton content. This in some ways parallels the
strong dependence of the reduction potential on pH (proton activity) for aqueous nanoparticles. The reduced
nanoparticles have extensive proton-coupled electron transfer (PCET) reactivity toward organic substrates. The kinetics
are in many cases complex and multiexponential. The dependence of the rates of the reactions on the thermodynamic
properties and other parameters such as capping group densities will be discussed. Related reactivity of molybdenum
nitride and metal-organic frameworks may also be presented.
INOR 141
Relative reactivity scale of alkanes from C-H bond functionalization reactions
Andrea Olmos2, Riccardo Gava2, Barbara Noverges1, Daniel R. Enrique2, Kane Jacob3, Teresa Varea1, Ana Caballero2,
Michel Etienne3, Gregorio Asensio1, Pedro J. Perez2, [email protected]. (1) Univ De Valencia Quim Org Dept,
Burjassot Valencia, Spain (2) CIQSO, Universidad de Huelva, Huelva, Spain (3) LCC-CNRS, Toulouse Cedex 4,
France
Alkanes are considered as plausible raw materials in chemistry on the basis of their availability. However, their chemical
inertness has yet circumvented such use, that is yet restricted to a few examples. Moreover, this family of compounds
displays quite different behavior on the basis of the chain length: the lighter members (C1-C4) are gaseous at
atmospheric pressure, then the alkanes becoming liquids and solids when increasing the number of carbon in the chain.
Because of this, the direct comparison of their relative reactivity has been difficult to achieve, avoiding the accessibility to
a scale of reactivity for the overall group of C nH2n+2 hydrocarbons.
We have recently discovered the catalytic capabilities of silver-containing catalysts for the functionalization of alkanes
upon transfer of the carbene unit CHCO2Et from ethyl diazoacetate, including the C1-C4 members, on the basis of the
employment of supercritical carbon dioxide as the reaction medium. 1 We have now taken advantage of such catalytic
behavior to carry out a series of competition experiments from which an overall relative reactivity scale from methane to
adamantane has been built.
1. (a) Caballero, A.; Despagnet-Ayoub, E.; Díaz, A.; Díaz-Requejo, M. M.; GonzálezNúñez, M. E.; Mello, R.; Muñoz, B.K.;
Ojo, W.-S.; Asensio, G.; Etienne, M.; Pérez, P. J. Science 2011, 332, 835. (b) Fuentes, M.A.; Olmos, A.; Muñoz, B. K.;
Jacob, K.; González-Núñez, M. E.; Mello, R.; Asensio, G.; Caballero, A.; Etienne, M.; Pérez, P. J. Chem. Eur. J. 2014.,
20, 11013.
Alkane functionalization competition reaction
INOR 142
Synthesis and reactivity of high valent organometallic Ni complexes
Melanie S. Sanford, [email protected]. Chemistry, University of Michigan, Ann Arbor, Michigan, United States
This presentation will describe our recent progress in the design and synthesis of high oxidation state organometallic Ni
complexes. Detailed spectroscopic characterization of these species as well as their reactivity under a variety of different
conditions will be discussed. In particular, studies of the mechanisms of both C–C and C–heteroatom coupling at high
valent Ni will be presented.
INOR 143
Small molecule activation mediated by an iron half-sandwich complex, [Cp’FeX]2
Marc D. Walter1, [email protected], Matthias Reiners1, Miyuki Maekawa1, Peter G.
Jones1, Johannes Hohenberger2, Jörg Sutter2, Karsten Meyer2. (1) Institut für
Anorganische und Analytische Chemie, TU Braunschweig, Ludwigshafen, Germany (2)
Department of Chemistry & Pharmacy, Friedrich-Alexander University of Erlangen - Nürnberg (FAU), Erlangen, Germany
The iron half-sandwich complex [Cp’FeI]2 (1) (Cp’= 1,2,4-(Me3C)3C5H2) shows a rich reaction chemistry.[1] In this
contribution the reactivity of 1 with pseudohalides such as KSCN and NaN3 will be presented resulting in spontaneous
elimination of CN· radicals and N2 to form the μ-S and μ-N bridged dimers, [Cp’FeS]2 (2) und [Cp’FeN]2 (3), respectively.
Complex 3 can also be formed from the N2 activation product [Cp’3Fe3N2] (4). The electronic structure and further
reactivity studies of these complexes will also be discussed.
[1] (a)
M. D. Walter, P. S. White, New J. Chem. 2011, 35, 1842; (b) M. D. Walter, J.
Grunenberg, P. S. White, Chem. Sci. 2011, 2, 2120; (c) M. D. Walter, P. S. White, Inorg. Chem. 2012, 51, 11860; (d) M.
Maekawa, C. G. Daniliuc, P. G. Jones, J. Hohenberger, J. Sutter, K. Meyer, M. D. Walter, Eur. J. Inorg. Chem. 2013,
4097.
INOR 144
Promoting alkane dehydrogenation by C-H activation at IrIII
Ashley M. Wright2, Kate Allen2, Dale Pahls1, Thomas R. Cundari1, Alan S. Goldman3,
Dennis M. Heinekey2, Karen I. Goldberg2, [email protected]. (1) Univ of
North Texas, Denton, Texas, United States (2) Univ of Washington, Seattle,
Washington, United States (3) Rutgers Univ, Piscataway, New Jersey, United States Pincer IrIII dicarboxylate complexes
have been shown to dehydrogenate alkanes to form alkenes and Ir III-hydride complexes. The reaction is proposed to
proceed via a concerted metalation-deprotonation followed by β-hydride elimination. Reaction of the IrIII-hydride product
with O2 and acetic acid regenerates the IrIII-dicarboxylate providing a potential lead for a catalytic process using O 2 as the
oxidant. Our efforts to understand the mechanism of these reactions using both experiment and theory as well as our
efforts to optimize the reactions and promote catalytic activity will be described.
INOR 145
Chelate complexes of 1st row transition metals: Redox non-innocence and multiple metal-ligand bonds
Peter T. Wolczanski, [email protected], Ala'adeen Swidan, Brian M. Lindley, Spencer
P. Heins, Wesley D. Morris, Nick Livezey, Brian P. Jacobs, Rishi Agarwal. Cornell Univ, Ithaca, New York, United States
A diverse array of chelates, including tetra-, tri-, and bi-dentate species, have been employed in the synthesis of 1st row
transition metal complexes. Combinations of pyridine, imines, vinyl, and related connectivities have permitted the
investigation of redox non-innocent behavior, and have allowed the preparation of metal-ligand multiple bonds. Structural
and spectroscopic studies augment reactivity studies, and provide clues as to whether chelate redox capabilities are
involved.
INOR 146
Low temperature oxidations of iridium(Cp*) complexes
Christopher Turlington1, Maurice Brookhart3, Joseph L. Templeton2,
[email protected]. (1) Chemistry, UNC Chapel Hill, Chapel Hill, North Carolina, United States (2) UNC Chapel Hill,
Chapel Hill, North Carolina, United States (3) Univ of North
Carolina, Chapel Hill, North Carolina, United States
Oxygen atom transfer to iridium(Cp*) complexes with bidentate ligands will be discussed. Oxidations are conducted at low
temperatures, and intermediates and reaction products are characterized by NMR spectroscopy. Oxygen atom transfer to
the central carbon of a coordinated nitrile was observed using a soluble iodosylbenzene derivative and an
Ir(Cp*)(phenylpyridine) cation with an electron-deficient bis(trifluoromethyl)benzonitrile ligand. Insertion into the iridium-carbon bond of coordinated phenylpyridine followed rapidly,
forming a coordinated organic amide moiety. A second oxygen atom transfer occurs if no trapping ligands are present.
Comparable studies with nitrene transfer reagents have also been explored. The role of high valent metal intermediates in
metal mediated oxidation reactions will be discussed.
INOR 147
Hydrogenolyis reactions catalyzed by iridium pincer complexes
Jonathan M. Goldberg3, Gene W. Wong4, Travis Lekich5, Karen I. Goldberg1, Dennis M.
Heinekey2, [email protected]. (1) Univ of Washington, Seattle, Washington, United States (2) University
of Washington, Seattle, Washington, United
States (3) Chemistry, University of Washington, Seattle, Washington, United States
Pincer iridium complexes with sterically undemanding alkyl and alkoxide groups on the P atoms have been prepared. The
reduced steric profile at the Ir center leads to significant changes in reactivity. Application of these complexes in
hydrogenation/deoxygenation of various substrates will be described.
INOR 148
Well-defined iron catalysts for the acceptorless reversible dehydrogenation of alcohols and N-heterocycles
Sumit Chakraborty, William Brennessel, William D. Jones,
[email protected]. Department of Chemistry, University of Rochester, Rochester, New York, United States
Acceptorless dehydrogenation of alcohols and N-heterocycles was accomplished with well-defined and inexpensive ironbased catalysts supported by a cooperating PNP pincer ligand. Benzylic and aliphatic secondary alcohols were
dehydrogenated to the corresponding ketones in good isolated yields upon release of dihydrogen. Primary alcohols were
dehydrogenated to esters and lactones, respectively. Mixed primary/secondary diols were oxidized at the secondary
alcohol moiety with good chemoselectivity. Cyclic amines are dehydrogenated to give quinolines. The reverse
hydrogenation reactions were also observed under mild conditions. The active catalytic species in the dehydrogenation
reaction, is independently synthesized, characterized, and its structure is confirmed by X-ray crystallography. A transdihydride intermediate is proposed to be involved in the hydrogenation reaction and its existence is verified by NMR and
trapping experiments. The mechanism of the reaction was investigated using both experiment and DFT calculations and
the crucial role of metal-ligand cooperativity in the reaction was elucidated.
INOR 149
First row transition metals and Lewis acid co-cataylsts for carbon dioxide reduction
Wesley H. Bernskoetter1, [email protected], Nilay Hazari2. (1) Dept of Chemistry Box
H, Brown University, Providence, Rhode Island, United States (2) Department of Chemistry, Yale University, New Haven,
Connecticut, United States
The reduction of CO2 is a central part of society’s grand challenge of shifting from petroleum to renewable carbon source
for our chemical and energy needs. Earth abundant first row transition metals are well placed for the catalyst development
required to utilize CO2 on scales required to meet these demands. Our work on the development of first row metals as
catalyst for CO2 functionalization with olefins and dihydrogen will be presented. Particular emphasis will be placed on the
role of Lewis acids as co-catalysts for these CO2 reduction reactions.
INOR 150
Applications of tripodal ligands in bioinorganic and organometallic chemistry Gerard F. Parkin,
[email protected]. Columbia University, New York, New York,
United States
Multidentate ligands have received considerable attention due to their ability to tailor the steric and electronic properties of
a metal center. The research presented will focus on applications of various tridentate and tetradentate tripodal ligands,
as illustrated by (i) the tris(3-t-butyl-5-methylpyrazolyl)hydroborato ligand, [Tpt-Bu,Me], which features a [N3] donor array, (ii)
the tris(2-oxo-1-t-butylimidazolyl) hydroborato ligand, [Tot-Bu], which features an [O3] donor array, (iii) the tris(2-mercapto1-t-butylimidazolyl)hydroborato ligand, [Tm t-Bu], which features an [S3] donor array, and (iii) the tris(2-pyridylthio)methyl
ligand, [Tptm], which features a [CN3] donor array.
INOR 151
Isolation of a terminal organocerium acetylide complex and its reactivity with enolizable ketones
Jee Eon Kim, [email protected], David Weinberger, [email protected],
Patrick Carroll, Eric J. Schelter. Dept of Chemistry, University of Pennslyvania,
Philadelphia, Pennsylvania, United States
The Ce–C bond is used extensively in organic transformations of carbonyl substrates to form new carbon-carbon bonds.
Despite of its broad use in new carbon-carbon bond forming reactions, a detailed understanding of cerium hydrocarbyl
complexes along the reaction coordinate for selective carbonyl addition has not yet been achieved. We have synthesized
and fully characterized the terminal Ce(III) acetylide complex,
Na[Ce(CCPh)(bdmmp)3], by metathesis of NaCCPh with Na[Ce(OTf)(bdmmp)3] (bdmmp = bis(dimethylamino)-methyl-4phenolate). We reacted the trivalent cerium acetylide compound with a series of carbonyl substrates, benzaldehyde,
acetone, acetophenone and benzylideneacetone, and isolated their carbonyl addition products as cerium metal
complexes. To our knowledge, these are the first structurally characterized cerium propargylic alkoxide complexes
resulting from carbonyl addition reactions. We offer that the bdmmp framework is a viable model compound for
understanding the role of the cerium metal cation along the carbonyl insertion reaction coordinate. The results of these
synthetic studies, as well as DFT studies of related compounds along the reaction coordinate, will be discussed.
INOR 152
Ligand effects in the synthesis of Ln 2+ complexes by reduction of
tris(cyclopentadienyl) rare earth precursors including C–H bond activation of an indenyl ligand
Jordan F. Corbey3, [email protected], Chad T. Palumbo2, David Woen3, Joseph W.
Ziller1, William J. Evans2. (1) Univ of California, Irvine, California, United States (2) Dept of Chemistry, University of California
Irvine, Irvine, California, United States (3) Chemistry, University of California, Irvine, Irvine, California, United States
It was recently discovered that reduction of the tris(cyclopentadienyl) complexes,
Cp′3Ln, 1, (Cp′ = C5H4SiMe3; Ln = Y, lanthanides), with potassium graphite forms molecular complexes with the formula
[K(2.2.2-cryptand)][Cp′3Ln], 2, that contain yttrium and all the lanthanides (except Pm) in the +2 oxidation state. Although
these complexes are isolable and crystallographically characterizable, they are so highly reactive that measurements of
their physical properties are challenging. In search of more stable analogs of 2 that still utilize the features of the
tris(cyclopentadienyl) ligand scaffold, which allows these +2 metal ions to be isolated, the reduction chemistry of Cp x3Ln
complexes has been investigated where Cp x = C5H5, C5H4Me, C5H3(SiMe3)21,3, and C9H7. UV-Vis and EPR data indicate
the formation of Y2+ and Gd2+ complexes with all of these tris(cyclopentadienyl) ligand sets except when Cp x = C9H7. The
only isolable product obtained from reactions with the tris(indenyl) system was {K(2.2.2cryptand)}{[(C 9H7)2Dy(μ-η5:η1C9H6)]2}, a complex containing the first example of the indenide dianion, (C9H6)2−, derived from C–H activation of the
(C9H7)1− monoanion. The implications of this reductive chemistry in C–H bond activation will be discussed, and the
stability of the Cpx3Ln reduction products will be compared with that of 2.
INOR 153
Reactivity of the Ln2+ complexes [K(2.2.2-cryptand)][(C5H4SiMe3)3Ln]: Reduction of aromatic hydrocarbons
Christopher Kotyk1, [email protected], Matthew R. MacDonald1, Joseph W. Ziller2,
William J. Evans3. (1) Chemistry, University of California, Irvine, Irvine, California,
United States (2) Univ of California, Irvine, California, United States (3) Dept of
Chemistry, University of California Irvine, Irvine, California, United States
The reductive capacity of the recently discovered Ln2+ complexes [K(2.2.2cryptand)][Cp'3Ln], 1-Ln (Cp' = C5H4SiMe3; Ln =
Y, La, Ce, Dy), has been probed by examining their reactions with aromatic hydrocarbons. 1-Ln is capable of reducing
naphthalene to generate the naphthalenide dianion complex [K(2.2.2cryptand)][Cp' 2Ln(η4-C10H8)], as well as the ligand
redistribution product [K(2.2.2cryptand)][Cp'4Ln]. Complex 1-Ln also reduces biphenyl to form
[K(2.2.2cryptand)][Cp'2Ln(η6-C6H5Ph)] (Ln = Y), a complex which appears to have only one of the phenyl rings reduced.
Synthetic details and structural and spectroscopic analyses will be presented on these as well as reactions involving other
aromatic substrates.
INOR 154
Investigation on charge-transfer absorptions of uranyl UO22+(VI) and chemical reduction of UO22+(VI) to UO2+(V) by
UV-visible and EPR spectroscopies Xiaoping Sun1, [email protected], Derrick Kolling2, Hajer Mazagri1, Blake
Karawan1. (1) Department of Natural Sciences and Mathematics, University of
Charleston, Charleston, West Virginia, United States (2) Department of Chemistry, Marshall University, Huntington, West
Virginia, United States
The uranyl UO22+(VI) cation exhibited strong charge-transfer absorptions at 350-400 nm in the aqueous solutions
containing bromide and iodide. The charge-transfer absorptions originate from a single-electron transfer from a halide
anion to the uranium(VI) valence shell. Their intensities (absorbances at 375 nm) have been found to be directly
proportional to molar concentrations of the halide (bromide or iodide) and UO 22+ in solution, respectively, showing the
nature of a bimolecular interaction in the charge-transfer transition. The absorptions were also greatly enhanced by acid.
An EPR study has indicated that the charge-transfer also took place slowly in the dark, resulting in appreciable chemical
reduction of UO22+(VI) to UO2+(V) (g=2.08) by bromide and iodide. In addition, a stable bromide-bromine anion-radical pair
Br2-. (quartet, g=1.92, a=85G) was identified. In the presence of sulfuric acid, CH 3SOCH3 (DMSO) was shown by EPR to
undergo a charge-transfer oxidation by UO22+(VI) to a stable CH3SOCH2. (DMSO.) radical (g=2.01), and UO22+(VI) was
reduced to UO2+(V). A chemical oxidation-reduction of UO22+(VI) and phenol in acetone was found by EPR to give
UO2+(V) and a stable phenoxyl (PhO.) radical (g=2.00) via a charge-transfer pathway.
INOR 155
Facile synthesis of NpI4 in solution
Aaron T. Johnson, [email protected], Jana K. Pfeiffer, Martha R. Finck, Kevin P. Carney, Leigh R. Martin. Idaho
National Laboratory, Idaho Falls, Idaho, United States
Two novel aqueous based synthetic routes for the production of NpI4 have been developed. The first method involves
reduction of Np(V) in nitrate media to Np(IV) by controlled potential electrolysis. Following this reduction, Np(IV) is
extracted into an organic phase using thenoyltrifluoroacetone (TTA) whereby it is then stripped into concentrated iodide
media where the complex is formed. The second method uses controlled potential electrolysis techniques to directly
reduce Np in iodide media, thus generating Np(IV)-Iodide in situ. Confirmation of successful synthesis was performed
using UV-visible-nIR spectroscopy. Solid NpI4 is made from these solutions by inducing crystallization. Both methods
represent facile, low-hazard techniques to synthesize materials in sufficient quantities for actinide organometallic
chemistry studies. Additionally, adequate quantities of material can be made for investigations regarding the
thermodynamic properties and vapor pressure of this material. Techniques for synthesis of the similar NpI3 compound and
characterization will also be discussed.
INOR 156
Lanthanide ions in molecular magnets
Muralee Murugesu, [email protected]. Chem Dept, University of Ottawa, Ottawa, Ontario, Canada
Multimetallic rare-earth systems and especially DyIII, ErIII-based materials have sparked much interest in the area of
molecular magnetism due to the large intrinsic magnetic anisotropy of the lanthanide ions. When such a unique property
is combined with a high-spin ground state (S) in a molecular complex, it causes slow relaxation of the magnetization as
seen for Single-Molecule Magnets (SMMs). Lanthanide only SMMs are rare due to the difficulty in promoting the magnetic
interactions via the overlapping bridging ligand orbitals with the contracted 4f orbital of the ions. Toward the goal of
inducing significant magnetic interaction between lanthanide ions and subsequently isolating high-energy barrier SMMs,
our research is currently focused on the use of phenoxide bridges as superexchange pathways between spin carriers.1-4
In addition, organometallic lanthanide sandwich complexes provided an alternative approach for understanding intriguing
quantum mechanical properties of SMMs.5-8 References:
1. Lin, P.-H.; Murugesu, M.* and co-workers , Angew. Chem. Int. Ed., 2008, 47, 8848.
2. Lin, P.-H.; Murugesu, M.* and co-workers, Angew. Chem. Int. Ed., 2009, 48, 9489.
3. Long, J.; Murugesu, M.* and co-workers, J. Am. Chem. Soc., 2011, 133, 5319.
4. Habib, F.; Murugesu, M.* and co-workers, J. Am. Chem. Soc., 2011, 133, 8830.
5. Jeletic, M.; Murugesu. M.* and co-workers, J. Am. Chem. Soc., 2011, 133, 19286.
6. Le Roy, J.; Murugesu. M.* and co-workers, J. Am. Chem. Soc., 2013, 135, 3502.
7. Le Roy, J.; Murugesu. M.* and co-workers, J. Am. Chem. Soc., 2014, 136, 8003.
8. Le Roy, J.; Murugesu. M.* and co-workers, Angew. Chem. Int. Ed. 2014, 53, 4413.
INOR 157
Lanthanides-TTF complexes: Correlation between single molecule magnet behavior and luminescence
Lahcene Ouahab, [email protected], Fabrice Pointillart, Olivier Cador,
Stéphane Golhen. Umr 6226 CNRS Universiti, Rennes Cedex, France
Lanthanide ions are well-known to exhibit large magnetic moments and strong magnetic anisotropy and therefore they are
considered as good candidates for the elaboration of Single Molecule Magnets (SMMs). Complexation of these particular
metal ions by redox active ligands derived from TTFs led to electroactive SMM with antennae effect of the ligands as well
as very good correlation between magnetism and luminescence at the molecular scale. We report in this lecture several
compounds exemplifying these features [1,3].
Among them, dinuclear complexes of lanthanides associating both 4,5-Bis(thiomethyl) 4’-carboxylictetrathiafulvalene and
4,5-Bis(thiomethyl) -4’-ortho-pyridyl -N-oxide carbamoytetrathiafulvalene ligands have been elaborated. Dc magnetic
susceptibility measurements highlight ferromagnetic interactions between the metallic centres. The two Dy(III) and Yb(III)based analogues display SMM behaviour. Experimental and theoretical magnetic and photo-physical investigations have
confirmed that a multielectroactive luminescent SMM is obtained in the case of the Yb(III) analogue [3]. We will present
also the first Dy(III)/TTF complex which exhibit a memory effect both in solid state and in solution [4]
REFERENCES
[1] F. Pointillart, et al., Chem. Eur. J., 2011, 17, 10397
[2] F. Pointillart, et al., JCS Chem Commun., 2012, 48, 714
[3] F. Pointillart, et al., JCS Chem Commun., 2013, 49, 615
[4] T. Da Cunha, et al., J. Am. Chem. Soc., 2013, 135, 16332
INOR 158
Ionothermal effects on actinyl coordination chemistry using task-specific ionic liquids
Philip A. Smith2, [email protected], Peter C. Burns1. (1) Univ of Notre Dame, Notre Dame, Indiana, United States (2)
CEEES, University of Notre Dame, Notre Dame, Indiana, United States
Our interests lie in the synthesis and characterization of uranyl and neptunyl coordination complexes from task-specific
ionic liquid (TSIL) solvent systems. In particular, we are interested in the relationships between the uranyl and neptunyl
chemistries as typified by their structural unit topologies, interstitial complexes, and hydrogen bonding networks. Our
research has yielded several novel compounds, running the dimensionality gamut from monomeric species through threedimensional frameworks, of which include several novel topologies. Our results illustrate the utility that ionothermal
syntheses bring to bear in exploring hitherto unknown actinyl chemistries outside the realm of traditional hydrothermal
methods.
INOR 159
Synthesis, structure, and electronic spectroscopy of f-element thiocyanates
Justin N. Cross1, [email protected], Stosh A. Kozimor2, Chantal S. Stieber6,
Julie A. Trujillo7, Enrique R. Batista3, Richard L. Martin4, Scott R. Daly5. (1) Chemistry
Division, Los Alamos National Lab, Los Alamos, New Mexico, United States (2) Los
Alamos Natl Lab, Los Alamos, New Mexico, United States (3) Theoretical Division, Los
Alamos National Laboratory, Los Alamos, New Mexico, United States (4) MS B214
Theoretical Div, Los Alamos Natl Lab, Los Alamos, New Mexico, United States (5)
Chemistry, University of Iowa, North Liberty, Iowa, United States (6) Los Alamos
National Lab, Los Alamos, New Mexico, United States
A series of d-block and f-element element thiocyanate complexes in a variety of oxidation states have been prepared. The
structures of these compounds, which have an assortment of coordination geometries, are presented and the periodic
trends compared. The electronic spectra of these compounds have been analyzed by a widerange of methods, principally
X-ray absorption spectroscopy, and the results presented. Trends in orbital mixing were also investigated so that
differences in metal – NCS bonding between f-elements and transition metals could be quantitatively evaluated.
INOR 160
Unconventional metal-organic frameworks (UMOFs) for separation of lanthanides from actinides and americium
from curium
Rita M. Silbernagel1, [email protected], Jonathan D. Burns1, Donald T. Reed2, David T. Hobbs3,
Abraham Clearfield4. (1) Chemistry, Texas A M University,
College Station, Texas, United States (2) Cemrc, Carlsbad, New Mexico, United States
(3) Savannah River National Laboratory, North Augusta, South Carolina, United States
(4) Chemistry Dept, Texas AM Univ, College Station, Texas, United States
Our research is directed towards carrying out separations of lanthanides from actinides and actinides from each other.
The basis for the separation procedures is through a group of ion exchangers that are composed of Zr(IV) or Sn(IV)
phosphonatephosphates. A discussion of the phosphonate and phosphate roles in ion exchange will be discussed. These
compounds are porous and exhibit low affinity for ions of 1+ and 2+ charge but are highly selective for ions of higher
charges (3+,4+). By utilizing oxidation procedures and solution pH, it is proposed that a clean separation of lanthanides of
3+ charge and actinyl ions of 1+ charge can be effected. Work in separating lanthanides from actinides in mixtures of ions
is in progress. Our preliminary results indicate the possibility of achieving excellent separation of lanthanides from
actinides by control of pH and oxidation states of the actinides. We acknowledge the U.S. Department of Energy NEUP
for support of this work.
INOR 161
Mg deficient IONiC/VIPEr: An online community for inorganic chemists
Margret J. Geselbracht4, Anne K. Bentley3, [email protected], Hilary J. Eppley1, [email protected], Elizabeth R.
Jamieson5, [email protected], Adam R. Johnson6, [email protected], Chip Nataro2,
[email protected], Barbara A. Reisner7, [email protected], Joanne L. Stewart8, [email protected], Sheila R.
Smith9, [email protected], Nancy Williams10,
[email protected], Lori A. Watson11, [email protected]. (1)
Depauw Univ, Greencastle, Indiana, United States (2) Lafayette Colg, Easton,
Pennsylvania, United States (3) Dept of Chem, Lewis Clark College, Portland, Oregon,
United States (4) Dept of Chemistry, Reed College, Portland, Oregon, United States (5)
Ford Hall - Chemistry Dept, Smith Colg, Northampton, Massachusetts, United States (6)
Harvey Mudd College, Claremont, California, United States (7) Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia, United States (8) Dept of Chem, Hope College, Holland,
Michigan, United States (9) Dept of Nat Sci, University of Michigan, Dearborn, Michigan, United States (10) Keck Sci.
Dept., Claremont Colleges, Claremont, California, United States (11) Chemistry, Earlham College, Richmond, Indiana,
United States
The primary goal of the Interactive Online Network of Inorganic Chemists (IONiC) is to improve the teaching and learning
of Inorganic Chemistry. Although IONic has grown and evolved significantly in its eight years of existence, the Virtual
Inorganic Pedagogical Electronic Resource (VIPEr) website remains the foundation of this community. With over 750
registered faculty users from around the world, VIPEr is a vibrant community of committed educators. Recent
developments with the site include the ability to ‘favorite’ learning objects (LOs), collections of related LOs, a weekly blog
post (BITeS - Blogging Inorganic Teaching & Scholarship) and a new and improved search engine. However, the feature
of the greatest value to the majority of our users is the continued development of high quality LOs. Over 150 new LOs
have been published within the past two years. Many of these were developed at our summer Back to Grad School
Workshops. The site will continue to grow and improve with the valuable input from our users that is often the result of
meetings and workshops. VIPEr come for the content, stay for the community (www.ionicviper.org).
INOR 162
IONiC VIPEr workshops at the frontiers of inorganic chemistry
Sheila R. Smith1, [email protected], Laurel G. Habgood2,
[email protected], Shaun E. Schmidt3, [email protected], Karin Young4, [email protected]. (1)
Dept of Nat Sci, University of Michigan, Dearborn, Michigan, United States (2) Chemistry, Rollins College, Winter Park,
Florida,
United States (3) Chemistry, Washburn University, Topeka, Kansas, United States (4)
Chemistry, Centre College, Danville, Kentucky, United States
In July of 2014, the Interactive Online Network of Inorganic Chemists (IONiC) hosted its second NSF-funded summer
workshop. The workshop, hosted at Northwestern University, focused on Bioinorganic Applications of Coordination
Chemistry. The workshop brought together 24 participants including graduate students, post-docs, and faculty of all rank
from both research intensive and primarily undergraduate institutions.
The first day of the workshop introduced the Virtual Inorganic Pedagogical Electronic Resource (VIPEr) website, covered
the fundamentals of teaching using a learning object (LO) and discussed experimental techniques that would be crucial to
the remainder of the workshop. The remaining days were spent on the focal points of the workshop; having four experts in
the field of bioinorganic chemistry present talks on their research and then developing new LOs based on those talks. A
total of 46 new LOs were developed in conjunction of this workshop, with each participant being an author or co-author on
at least 2 LOs. Two of the participants and one member of the IONiC leadership council will discuss their experience at
the workshop and how their courses have been affected as a result. IONiC will be holding another workshop, HeteroGenius Catalysis: An IONiC summer workshop at the Frontiers of Inorganic Chemistry, at the University of Washington in
June of 2015.
INOR 163
Effect of oxidation state on the anticancer activity of several gold polypyridyl complexes.
DanielleJamie Gibler, [email protected], Allyn C. Ontko. Dept of Chem
Phys, Arkansas State University, State University, Arkansas, United States
Research in our group focuses on the anticancer activity of Au(III) coordination compounds containing extended p
systems such as the ubiquitous dipyrido[3,2-a:2',3'-c] phenazine or DPPZ ligand. While our compounds show significant
activity due to both groove binding and intercalation with double stranded DNA, we still question the contribution due to
the Au(III) à Au(I) redox couple. To this end, we have synthesized, characterized, and studied the anticancer activity of a
series of analogous Au(III) and Au(I) compounds containing identical polypyridyl ligand systems for comparison.
Measurement of LD50 values, generation of ROS in vitro, and solution chemistry under physiological conditions are
examined.
INOR 164
Novel gold(III) chelates of 7-substituted dipyrido[3,2-a:2',3'-c] phenazine and their evaluation as antitumor agents
Kamalakannan Palanichamy2, Connor Gatewood1,
[email protected], Allyn C. Ontko1. (1) Dept of Chem Phys, Arkansas
State University, State University, Arkansas, United States (2) College of Medicine, Ohio State University, Columbus,
Ohio, United States
The emergence of drug resistance to commonly utilized chemotherapeutics, like cisplatin, has necessitated a search for
new or improved anticancer agents. To this end, this work details the synthesis, characterization, and anticancer activity
of a series of gold(III) 7-substituted dipyrido[3,2-a:2',3'-c] phenazine complexes. This represents a continuation of our
previous work in which gold(III) dipyrido[3,2-a:2`,3`-c]phenazine was found to have significant anticancer activity when
tested in cisplatin-sensitive and – resistant cell lines. The aromatic heterocyclic functionality was changed by varying the
shape and polarity of the substituents with the hope that substituents may alter the extent of intercalation and bind to DNA
at sequence-specific regions. Anticancer activity and DNA interaction studies were conducted to determine whether
stacking interactions differ among this ligand series.
INOR 165
Gold (I) and Gold(III) compounds as substrates for zinc finger reactivity
James F. Beaton2, Camilla Abbehausen1, Paul Bacila2, Pedro Corbi1, Nicholas Farrell2, [email protected]. (1) University
of Campinas, Campinas, Brazil (2) Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia,
United States
Gold(III) diethylenetriamine compounds [(Au(III)(dien)L]3+ (L = N-bound purine, pyrimidine or pyridine) where, for example,
L = 9-EtGuanine or 4-NMe2pyr, stabilize the Au(III) oxidation state relative to [AuCl(dien)] 2+.[1] The compounds also act as
substrates for targeting the Cys3His zinc finger moieties of HIVNCp7, with subsequent loss of function. In search of more
stable analogs and to diminish cytotoxic effects a wider series of Au(III) chelates including substituted dien ligands where
the various NH groups are replaced by NMe groups, and sterically hindered N-donor heterocycles, especially 1-
MeCytosine, have been prepared and characterized. This contribution summarizes the results and comapres the
properties with those of the related Gold (I) compounds [(PR3)AuL]+.[2]
[1]
Spell, S.R. and Farrell, N.P. Inorg. Chem. 53:30-32 (2014) DOI: 10.1021/ic402772j PMID 24328316.
[2]
Abbehausen, C., Peterson, E.J., de Paiva, R.E.F., Corbi, P.P, Formiga, A.L.B., Qu, Y. and Farrell, N.P. Inorg.
Chem. 52:11280-11287 (2013). DOI: 10.1021/ic401535s.
PMID 24063530
This work was supported by NSF-CHE-1413189 and Science Without Borders
(UnICAMP project 154/2012)
INOR 166
Synthesis and photolysis of a novel family of photoactivatable HNO donors using the (3-hydroxy-2naphthalenyl)methyl photolabile protecting group
Yang Zhou 1, [email protected], Rohan S. Dassanayake1, Nicola E. Brasch2, Paul
Sampson1. (1) Department of Chemistry and Biochemistry, Kent State University, Kent,
Ohio, United States (2) School of Applied Sciences, Auckland University of Technology, Auckland, New Zealand
The development of new nitroxyl (HNO) donors has received increasing attention due to their promise for treating
congestive heart failure. We are developing new HNO donors, suitable for studying the fundamental bioinorganic
chemistry of HNO, which rapidly release HNO via photoactivation. Herein, we report the synthesis of a new family of
photoactivatable HNO donors 1 based on the use of the (3-hydroxy-2naphthalenyl)methyl (HNM) phototrigger.
Mechanistic photochemical studies of 1 leading to HNO generation (along with a competing side reaction) are discussed.
INOR 167
Correlating cytotoxicity of ruthenium(II) polypyridyl complexes with activation wavelength
Erin Wachter, [email protected], David K. Heidary, Amy Effinger, Edith C.
Glazer. Chemistry, University of Kentucky, Lexington, Kentucky, United States
Current chemotherapeutics have debilitating side effects, and new forms of treatment to reduce these side effects are
needed. Phototherapy is an increasingly promising modality for cancer treatment where drug molecules are “turned on”
with the application of light. The use of light to trigger a cytotoxic effect could reduce the off target damage by spatially
restricting the areas exposed to irradiation, decreasing side effects for cancer patients. The wavelength of activation
affects the depth of tissue penetrance, and compounds that are activated with red or near-IR light are appealing as this
would increase the types and regions of tumors that are accessible to phototherapy.
Ruthenium(II) polypyridyl complexes have tunable absorption characteristic that can be exploited to design complexes
that are inert until activated with different wavelengths of light, increasing their versatility as phototherapeutics. Chemical
modifications cause changes in the metal-to-ligand charge transfer state, an excited state that can lead to additional
chemical reactivity, electron transfer, and/or oxygen sensitization. Incorporation of π expansive ligands, such as 2,2’-
biquinoline or 2,2’-bi-1,8naphthyridine, results in a red-shift of the MLCT energy compared to Ru(bpy)3, a blue light
activated photosensitizer. Additionally, introduction of strain to the metal center allows for light activated ligand
dissociation, producing an active species that is capable of reacting with biomolecules. These complexes present
promising toxicity in in vitro studies with human cancer cell lines.
INOR 168
E. coli as a screening system to study potential anti-cancer agents with different mechanisms of action
Yang Sun, [email protected], Zhihui Zhang, David Heidary, Christopher I. Richards, Edith Glazer. Chemistry, University
of Kentucky, Lexington, Kentucky, United States
Inspired by Rosenberg's discovery of cisplatin, Escherichia coli is an informative model system to screen Ru(II) polypyridyl
complexes with potential anti-cancer properties. E. coli also provides a simpler biological system to facilitate studies of
mechanisms of action. Using the photo convertible protein Dendra2 as a reporter in E.coli, fluorescence-based assays are
used to study the mechanisms of action of different Ru(II) polypyridyl complexes with potential anti-cancer activity. These
studies were performed from the single cell level to population level. The kinetics of fluorescent protein production was
used to evaluate the difference between agents that inhibit transcription vs. agents that act as inhibitors of translation.
This research provides a simpler model system for biological studies to elucidate mechanistic details of cytotoxic agents.
INOR 169
New family of rhodium metalloinsertors with improved selectivity and potency against DNA mismatch repair
deficient cell lines
Kelsey M. Boyle, [email protected], Alexis Komor, Jacqueline K.
Barton. Department of Chemistry, California Inst of Tech, Pasadena, California, United
States
Rhodium metalloinsertors are a unique family of complexes that selectively bind DNA base pair mismatches. We have
seen crystallographically that insertion of the sterically expansive chrysi (5,6-chrysenequinone diimine) ligand into DNA at
a mismatched site leads to the ejection of the mismatched bases. This unique lesion may serve as the biological target
within the cell. Previously, it has been shown that rhodium metalloinsertors preferentially increase cell death and inhibit
proliferation of mismatch repair (MMR)-deficient colorectal cancer cell lines over their MMR-proficient counterparts.
Recently, a new family of rhodium metalloinsertors containing a rhodiumoxygen bond has been shown to have improved
potency in the nanomolar range as well as increased cytotoxic selectivity toward MMR-deficient cells. This family appears
distinct from previous metalloinsertors in that both the Δ− and Λ− isomers of these complexes bind mismatched DNA with
similar affinities. Current research is focused on extending the family to include new complexes that will allow us to
explain in detail the basis for the high cell selectivity and potency of this new family.
INOR 170
Development of light activated Ru(II) complexes applicable in photodynamic therapy
Aaron M. Kishlock, [email protected], Elizabeth A. Stimmell, Avijita Jain,
[email protected]. Chemistry, Indiana University of Pennsylvania, Indiana, Pennsylvania, United States
Photodynamic therapy (PDT), a noninvasive cancer therapy that uses light and a photoactive molecule to selectively kill
cancer cells has shown promise in cancer treatment. Currently used PDT agents induce 1O2 mediated DNA
photocleavage when exposed to visible light. The requirement of oxygen for the activity has limited the use of PDT agents
in aggressive tumors which are often hypoxic. In this work, we will present synthesis, characterization, and DNA binding
studies of Ru(II) based metal complexes containing bulky ligand, 2,2' biquinoline. These complexes were designed to bind
with DNA upon photoirradiation under hypoxic conditions.
INOR 171
Transition metal complexes used for the detection of mismatched DNA base pairs
Thomas N. Rohrabaugh1, [email protected], Claudia Turro2. (1) Chemistry and Biochemistry , The Ohio State
University , Columbus, Ohio, United States (2) Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio,
United States
Mismatched (non-canonical) DNA base pairing is the most common defect in DNA.
Usually, mismatched DNA base pairs are located and repaired via Mismatch Repair (MMR) machinery. However, if the
MMR machinery is defective, then mismatches can accumulated and the possibly of these cells becoming cancerous
increases. For this reason, the discovery of a molecule that can probe the existence of mismatches can prove to be a
useful tool for diagnosing MMR machinery defects and the probability of cancer formation. Recently, metallo-insertors
complexes have been developed that bind selectively to mismatched sites in double strand DNA. Though these
complexes have been found to bind selectively to mismatches, they lack a “light switch” behavior for mismatch binding
recognition. Herein, two novel ruthenium(II) polypyridyl complexes, [Ru(bpy) 2(4-(carbazol-9-yl)-phen)]Cl2 (bpy = 2,2'Bipyridine, phen = 1,10Phenanthroline) and [Ru(bpy) 2(4-(indol-1-yl)-phen)]Cl2, have been synthesized, characterized, and
the photophysical properties have been investigated. The selective binding to DNA mismatch, and “light-switch” behavior
was investigated by DNA titration with matched and mismatched double strand DNA monitored with UV-Vis and Emission
spectroscopy.
INOR 172
Spectroscopic studies of the biologically active peptide of low-molecular-weight chromium-binding substance
Hirohumi Arakawa, Ebony Love, John B. Vincent, [email protected]. Department of Chemistry, The University of
Alabama, Tuscaloosa, Alabama, United States
Low-molecular-weight chromium-binding substance (LMWCr) carries Cr from the tissues via the bloodstream to the urine
and has been proposed to be the biologically active form of Cr when subjects receive supra-nutritional doses of Cr.
Recently the contiguous peptide of LMWCr has been sequenced, and the synthetic peptide of this sequence in
combination with Cr increases glucose uptake and increases Akt phosphorylation by skeletal muscle cells in the presence
of insulin and increases insulin sensitivity in mice. The results of spectroscopic studies to elucidate the environment of the
chromic ions bound to the peptide are described.
INOR 173
Modeling matrix metalloproteinase inhibition with carbonic anhydrase
Whitney A. Richert2,1, [email protected], Daniel DeGenova1, Anthony Forchonie1, Rahil Patel1, Ania Plonski1,
Rithvik Venna1, Zachary Higgins1, Micah Morris1, Sameer Al-Abdul-Wahid2,1, David L. Tierney2,1. (1) Miami University,
Oxford,
Ohio, United States (2) Dept of Chem and Biochem, Miami University, Oxford, Ohio,
United States
Carbonic anhydrase (CA) is being used as a model for matrix metalloproteinases
(MMPs). CA is a more ubiquitous protein that binds zinc in the same manner as MMPs, His3(OH). Current MMP inhibitors
target both unregulated and normal functioning MMPs at the catalytic Zn(II) site, but show minimal specificity and high
toxicity. A new class of inhibitor building blocks are being evaluated as potential MMP inhibitor scaffolds, based on their
interactions with CA.
INOR 174
Toxic carbon monoxide removal by the soil bacteria Oligatropha carboxidavorans: Insights from In silico models
Morgan C. Dienst3, [email protected], Tao A. Large2, Dalia Rokhsana4, Marius
Retegan1, Frank Neese1. (1) for Chemical Energy Conversion, Max Planck Institute,
Muelheim an der Ruhr, Germany (2) Whitman College, Walla Walla, Washington,
United States (3) Chemistry, Whitman College, Walla Walla, Washington, United States Minor Outlying Islands (4)
Chemistry, Whitman College, Walla Walla, Washington, United States
Mo-Cu containing carbon monoxide dehydrogenase (CODH) from the aerobic soil bacteria Oligotropha carboxidovorans is
an important enzyme in the global carbon cycle, converting toxic carbon monoxide into less toxic carbon dioxide using the
reaction: CO + H2O →CO2 + 2H+ + 2e-. The catalytically active state is believed to be the Mo(VI)-Cu(I) state and is
reduced to Mo(IV)-Cu(I) during CO oxidation. Despite the close to atomic resolution structure (1.1Å), the active state and
the intermediates involved during catalysis are not yet clearly understood and several aspects of the active site remain in
question, such as ligand composition around the metal centers, oxidation and spin states of the metals, substrate binding,
and possible intermediates formed during the catalytic cycle. To gain further insights, computational models were
systematically developed starting from a small inorganic model containing only the first coordination sphere (~ 41 atoms),
and extended to a converged model (~ 179 atoms) incorporating important second sphere residues. As expected, smaller
models resulted in highly distorted geometries relative to the crystal structure due to the absence of important residues
involved in weak interactions around the metal centers. Using our converged model, the role of the important second
sphere residues was evaluated using in silico point mutations. Our results revealed that several of these residues are
critical to maintain the functionality of a realistic model. These models are currently being evaluated by comparing
spectroscopic and redox properties with the available experimental results. To assess the effects of the larger protein
environment on the active site, we are implementing integrated quantum mechanics and molecular mechanics (QM/MM)
models.
INOR 175
Overlap of protein inhibition and metal chelation: A case study
Ritika Gautam2, [email protected], Eman Akam3, Elisa Tomat1. (1)
University of Arizona, Tucson, Arizona, United States (2) Chemistry and Biochemistry,
University of Arizona, Tucson, Arizona, United States (3) Chemistry and Biochemistry, University of Arizona, Yuma,
Arizona, United States
Small organic compounds acting as protein inhibitors constitute a fast-growing class of FDA-approved drugs for treatment
of numerous diseases. Sirtinol is one of the first reported inhibitors of sirtuin proteins, a family of class III histone
deacetylases that are crucial for survival of cells in response to stress conditions. The sirtuin proteins are currently
undergoing intense investigation as potential drug targets for the treatment of age-related diseases like diabetes,
neurodegeneration, and cancer. We demonstrate that sirtinol chelates transition metals both in vitro and intracellularly.
With a scaffold that is similar to those of the isonicotinoyl hydrazone family of iron chelators, sirtinol features a tridentate
coordinating site. UV-visible absorption, mass spectrometry, elemental analysis and X-ray diffraction data indicate that
sirtinol binds Fe(II) and Fe(III) cations in organic solvents and in buffered aqueous solutions (pH 7.40). In addition,
intracellular scavenging of iron in Jurkat cells was determined by whole-cell EPR and by fluorescence measurements
using calcein as a probe of iron binding. This study demonstrates the metal chelating activity of sirtinol, which has the
potential to interfere with metal homeostasis within biological systems and therefore affect studies focused on the sirtuin
inhibition activity of this molecule.
INOR 176
Structural insights of a mononuclear iron center in 2,6-dichlorohydroquinone-1,2dioxygenase (PcpA) from in
silico models
Peter R. Carmichael, [email protected], Dalia Rokhsana, Timothy E.
Machonkin. Whitman College, Walla Walla, Washington, United States
The bacterial enzyme from Sphingobium chlorophenolicum, 2,6-dichlorohydroquinone1,2-dioxygenase (PcpA) utilizes a
unique mechanism to carry out an oxidative ring cleavage of halogenated aromatic substrates at a mononuclear iron
center. Recently, the crystal structure of the enzyme was reported at a 2.6 Å resolution and revealed that the iron is
coordinated with two histidines (His11 and His227) and a glutamic acid (Glu276) in the first coordination sphere. The
structural features of this enzyme are similar to the extradiol dioxygenase enzyme family around the mononuclear iron
center. However, they differ significantly in their substrate specificity towards halogenated aromatic compounds. Other
similar extradiol dioxygenases have been shown to be inhibited by the substrates of the PcpA enzyme. Despite the
geometric information from the crystal structure, the composition of the active site (number of weakly coordinating water
molecules), oxidation and spin states of iron, geometry of the iron center, and substrate binding remain uncertain. Due to
the lack of explicit structural insights, a computational investigation is undertaken. Different model complexes are
generated starting from the crystal structure and will extended until a converged model is achieved. Our initial
investigation primarily focused on the quantum mechanical (QM) models investigating the coordination geometry and spin
state of the Fe-center. To assess the protein and the solvation effects, we are concurrently developing integrated quantum
mechanics and molecular mechanics (QM/MM) models.
INOR 177
Synthesis and reactivity of manganese(III) complexes with tetradentate ligands that mimic superoxide dismutase
enzymes
Steven T. Frey, [email protected], Haley A. Cirka, [email protected], William
A. Gallopp, Prince B. Moses. Chemistry Department, Skidmore Coll, Saratoga Springs, New York, United States
Superoxide dismutases (SODs) are a family of enzymes that catalyze the dismutation of superoxide radical anions (O 2-) to
hydrogen peroxide and molecular oxygen, thereby protecting cells from this damaging reactive oxygen species. However,
an excess of O2- can be produced by the immune system in response to inflammatory diseases or strokes, overwhelming
locally available SOD. Low molecular weight compounds that mimic SOD activity are therefore of interest as potential
pharmaceuticals. The goal of our work is to synthesize complexes that resemble the active site center of manganese(III)
ion-containing SOD and to examine these complexes for their ability to dismutate superoxide ion. The synthesis and
characterization of two such complexes from tetradentate ligands containing either pyridine or quinoline moieties is
described herein. Characterization of these complexes has been achieved by FT-IR and UV-vis spectroscopy, and
elemental analysis. Using the Fridovich assay, we have demonstrated that these complexes are active SOD mimics.
INOR 178
Biochemical, kinetic, and spectroscopic characterization of a promiscuous metaldependent DMSP-lyase
Adam Brummett1, [email protected], Mishtu Dey2. (1) Chemistry, Univeristy of Iowa, Iowa City, Iowa, United
States (2) Chemistry, University of Iowa, Iowa City, Iowa, United States
Roseobacter Ruegeria pomeroyi expresses a cupin containing lyase responsible for dimethylsulfoniopropionate (DMSP)
catabolism, liberating the climatically active dimethylsulfide (DMS). Approximately 50 million tons of this biogenic volatile
sulfur gas is released to the atmosphere annually. R. pomeroyi uses DMSP as a sole carbon and sulfur source, and
DMSP lyases cleave DMSP releasing DMS. The enzyme is a member of a less characterized class of DMSP lyases and
shares some sequence similarity with other DMSP lyases. Despite the environmental significance of DMS, the
mechanism by which these lyases produce DMS is understudied primarily due to the lack of sufficient biochemical and
structural data. Sequence analysis suggests that the DMSP-lyase contains conserved cupin residues that bind metal ions
and contribute to the enzymatic activity. The metal-binding properties of the DMSP-lyase, DddW, expressed in E. coli
were investigated. Measurements of metal binding affinity and catalytic activity indicate that while Fe(II) is the most tightly
bound metal ion, both Fe(II) and Mn(II) are preferred catalytic metal ions. Stoichiometry studies suggest the DMSPlyase
requires one metallocofactor per monomer. The electronic absorption spectra of anaerobic Fe(II)-enzyme saturated with
NO indicate interaction of NO. Consistent with the absorption data, electron paramagnetic resonance (EPR) spectra of
Fe(II)-enzyme complexed with NO suggest NO binding to the EPR silent Fe(II) site giving rise to an EPR active species
(g= 4.29, 3.95, 2.00). The rhombicity of the EPR spectrum is increased in the presence of DMSP, indicating that the
substrate binds to iron site without displacing bound NO. While other DMSP lyases have been characterized, this is the
first thorough study of how a metallocofactor is involved in the metal-dependent lyase reaction.
INOR 179
Effect of mutations on the stability of P450BM3 as determined by chemical and thermal denaturation
Catherine Denning, [email protected], David K. Heidary, Edith Glazer. Chemistry,
University of Kentucky, Lexington, Kentucky, United States
Cytochrome P450s are a dynamic family of proteins capable of carrying out different reactions on several classes of
substrates, such as the breakdown of xenobiotics and the synthesis of steroids. Many of the human proteins are
membrane bound, making them difficult to study in vitro. As an alternative, P450BM3, a bacterial protein, can be used as a
model system. By introducing different point mutations, P450BM3 can be made promiscuous and able to catalyze a wider
range of reactions than the wild- type (WT) enzyme. Studying the stability, dynamics, and kinetics of these mutations in
the presence of different substrates can enhance our understanding of the relationship between substrate choice and
stability. In this work, we use two main techniques to investigate the stability of P450 BM3 with and without bound
substrates: pulse proteolysis and the N-[4-(7-diethylamino-4-methyl-3-coumarinyl)phenyl]maleimide (CPM) assay. Pulse
proteolysis examines protein degradation of P450BM3 in the presence of chemical denaturants. The results from pulse
proteolysis show stabilizing or destabilizing effects of substrates, and allow comparison of the stability of each mutant to
the WT P450BM3. The CPM assay monitors thermal denaturation of the protein via a chemical reaction of solvent-exposed
cysteines. Together these two assays provide complimentary techniques to assess the stability of P450 BM3 as a function
of mutation and substrate choice. Our results indicate that wild-type P450BM3 is most stable, but addition of substrates
decreases protein stability. In contrast, destabilized, promiscuous mutant forms of P450BM3 exhibit an increase in stability
upon addition of substrates. The results of this study suggest that there is trade-off between stability and promiscuity, and
suggests that there is an optimal compromise that allows for catalytic function.
INOR 180
Synthesis, characterization, and applicability of reactive biomimetic model complexes toward important
biological reactions
Kristin J. Meise2, [email protected], Elizabeth M. Brandes3, Roslyn Theisen1. (1)
Dept of Chem, University of Wisc - Eau Claire, Eau Claire, Wisconsin, United States (2) Chemistry, University of
Wisconsin-Eau Claire, Sheboygan, Wisconsin, United States
(3) Chemistry, University of Wisconsin-Eau Claire, Franklin, Wisconsin, United States
The catalytic mechanism of dioxygenase enzymes, such as the metalloenzyme quercetin 2, 3, dioxygenase (QDO), which
catalyzes the oxidation of two carbon-carbon bonds of quercetin and releases carbon monoxide and the corresponding
depside, is not well understood. This project involves the development, synthesis, and characterization of new biomimetic
model systems consisting of a tetra-dentate N3O– containing ligand (BPG) and divalent first-row transition metal ions
observed in bacterial and fungal QDO enzymes. The goal of this research is to understand how the unique active site of
this enzyme cleaves the O-heterocyclic ring of quercetin by evaluating the functionality of a series of metal complexes
with ligand systems similar in structure to the active site of QDO. Four metal complexes, [Co(BPG)]+1, [Cu(BPG)]+1,
[Zn(BPG)]+1, and [Mn(BPG)]+1, have been isolated, as well as two substrate enzyme model complexes which mimic the
QDO active site, [Cu(BPG)(Maltol)], and [Co(BPG)(Maltol)]. This poster will also report preliminary reactivity experiments
with O- and N-heterocyclic compounds.
INOR 181
Reduction of copper(II) by thioether sulfur: A synthetic model for the amyloid beta peptide
Matthew Wallace2, [email protected], Robert P. Houser1. (1) University of Northern Colorado, Greeley,
Colorado, United States (2) Chemistry & Biochemistry, University of Northern Colorado, Evans, Colorado, United States
Alzheimer’s disease (AD) is a severe neurodegenerative disease that is the most common form of dementia in people
over the age of 60. AD is characterized by the formation of fibrillary tangles and insoluble amyloid β (Aβ) plaques in the
brain. One of the more prevalent hypotheses suggests that the oxidation of methionine (Met) in Aβ by metal ions induces
oxidative stress and creates reactive oxygen species (ROS). Using a new ligand, containing a prydyl ring, two amide
groups, and two thioether groups, we were able to spontaneously reduce copper (II) and oxidize one of the thioether
groups into a sulfoxide. We believe that the pyridyl ring and amide groups act as an anchor to allow the thioethers and
copper to undergo spontaneous redox that would not normally occur, creating an initial radical cation and copper (I). This
cation radical then reacts with O2 to form the sulfoxide and a superoxide anion radical. In acidic conditions the superoxide
undergoes a disproportionation reaction creating O2 and H2O2. This formation of both a sulfoxide and an ROS would
indicate that this particular ligand system is an adequate model of reduction of copper by a Met residue in the Aβ peptide.
The reduction of the copper, formation of the sulfoxide, generation of H 2O2, and spectroscopic details including IR, UV-vis,
and Mass spectrometry will be presented.
INOR 182
Reactivity and electrostatics of ribosomal RNA hairpins with modified nucleotides determined by cationic metal
complexes
Gayani Dedduwa-Mudalige1, [email protected], Sofi Elmroth2, Christine S.
Chow1. (1) Department of Chemistry, Wayne State University, Detroit, Michigan, United
States (2) Department of Biochemistry and Structural BIology, Lund University, PO Box 122, SE-221 00, Lund, Sweden
Electrostatics associated with complex RNA molecules are important for their molecular recognition and function. Cationic
metal complexes like cisplatin have been shown to interact with different types of cellular RNA. In the initial step of
coordination to nucleic acids, RNA and activated cisplatin interact electrostatically to then form a platinumbased
nucleotide adduct. These interactions therefore provide a means to evaluate electrostatic environments of RNA and
determine the contribution of modified nucleotides on such atmospheres. The goal of the current study was to utilize
cisplatin as a probe to investigate electrostatics in model E. coli ribosomal RNA (rRNA) hairpins. First, the rates of
cisplatin coordination to rRNA hairpins were determined by gel shift assays. The kinetic data were then evaluated by
Brønsted-Debye-Hückel and polyelectrolyte theories to determine the influence of electrostatics. The GpG sites present in
rRNA were found to be the primary targets. Under low monovalent cation conditions different cisplatin reactivities were
observed for rRNA with modified nucleotides. Pseudouridine modifications did not alter the global electrostatics of rRNA;
however, altered electrostatics was observed with changing nucleotide sequences and in the presence of divalent cations
in the medium. Collectively, findings from this study show the differences in drug reactivities with RNA containing modified
nucleotides and the utility of cationic-metal-coordination kinetics to monitor electrostatics of RNA.
INOR 183
Fluorescently-labeled bioactive protein nanoparticles (prodots) for improved uptake by oral cancer cells
Bobbi Stromer1, [email protected], Inoka Deshapriya2, Ajith
Pattammattel2. (1) University of Connecticut, Storrs, Connecticut, United States (2) Chemistry, University of Connecticut,
Storrs, Connecticut, United States
A simple and effective method for synthesizing highly fluorescent, protein-based nanoparticles (Prodots) and their facile
uptake by oral cancer cells is described here. Prodots made from glucose oxidase (nGO), bovine serum albumin (nBSA),
horseradish peroxidase (nHRP), catalase (nCatalase) and lipase (nLipase) were found to be 15-50 nm wide and have
been characterized by transmission electron microscopy (TEM), circular dichroism (CD), fluorescence spectroscopy,
dynamic light scattering (DLS) and optical microscopic methods. Data showed that the secondary structure of the protein
in Prodots is retained to a significant extent and specific activities of nGO, nHRP, nCatalase and nLipase were 80, 70, 65
and 50% of their respective unmodified enzyme activities. Calorimetric studies indicated that the denaturation
temperatures of nGO and nBSA increased while that of the other Prodots remained nearly unchanged, and the storage
half lives of Prodots increased 4 to 8-fold when compared to those of the respective proteins. Exposure of nGO and nBSA
to oral cancer cells indicated rapid uptake within 2.0-2.5 h. Uptake was accompanied by significant blebbing of the plasma
membrane and indicated nearly uniform distribution of the particles in the cells, as evidenced from optical microscopy
studies. The presence of nGO/glucose in the media enhanced the uptake of the other Prodots, and hydrogen peroxide
induced membrane permeability is responsible for this rapid uptake of Prodots. These are the very first examples of very
rapid cellular uptake of fluorescent Prodots, made from proteins and this approach is a simple and efficient method for
Prodot preparation and uptake into oral cancer cells.
INOR 184
New fluorescent probes for peptide nucleic acid (PNA) based diagnostics
Shankar Naik, [email protected], Eylon Yavin. Institute for Drug Research, School of Pharmacy, Faculty of
Medicine, The Hebrew University of Jerusalem, Jerusalem,
Israel
Fluorescent nucleobase surrogates provide nucleic acids with unique and interesting properties. The introduction of a
fluorophore as a base surrogate into peptide nucleic acid (PNA) oligomers has been well documented. Such PNA probes
signal hybridization by enhancement of fluorescence and also allow the measurements of local structure and dynamics of
nucleic acids. The increased fluorescence of such a dye when bound to nucleic acids has been attributed to the restricted
rotation of monomethine bond that connects the two aromatic systems. Previous studies in our lab has demonstrated the
ability of thiazole orange (TO) embedded PNA-molecular beacons (MBs) in discriminating complementary sequence from
mismatch mRNA sequences at a single base resolution in living cells. Realizing the potential of such fluorophores, a quest
for molecules that have the ability to absorb light at a longer wavelengths relative to TO, began with the synthesis of
acridine and indanone based fluorescent dyes. Acridine conjugated to benzothiazole derivative was introduced into the
Fmoc-2aminoethylglycine backbone yielding a PNA building block as a light-up probe. Similarly, indanone modified as its dicyanoand tetracyano derivatives acted as precursors for PNA monomer synthesis. These monomers were incorporated into the
PNA sequence by Fmoc-solid phase peptide synthesis. The fluorescent properties of these probes with respect to single
PNA strands and pairing DNA sequences are currently being studied and may pave the way to real-time in-vivo imaging
of RNA biomarkers for a variety of disease-related indications.
INOR 185
Efficient DNA photo modulation by PNA-Rose Bengal conjugates
Yossi Shemesh, Shankar Naik, [email protected], Eylon Yavin. Hebrew
University of Jerusalem, Jerusalem, Israel
Design and discovery of chemical agents capable of sequence specific DNA modification is a challenge with a wide
potential for the development of gene knockdown and gene repair technologies in molecular biology and medicine.
Previous work in our lab, showed an efficient light induced plasmid cleavage by the combination of L-tryptophan (Trp) and
a Thiazole orange(TO) conjugated to the N-terminus of a PNA (peptide nucleic acid) sequence. Mechanistic examinations
suggested that singlet oxygen generated by the dye is not strong enough to damage the DNA directly, but can oxidize the
Trp to an endoperoxide leading to DNA (plasmid) cleavage. In this work, we improved the system further by changing the
photo-sensitizer to Rose Bengal (RB), which is known in the literature as potent singlet oxygen generator, used often in
the research for photodynamic therapy (PDT) systems.
Interestingly, the new PNA conjugates present different mechanism of DNA damage; after irradiation, the generation of
high concentrations of singlet oxygen lead to crosslinking as corroborated by slow migrating bands on a native
polyacrlylamide gel. As RB emits in the Visible-NIR region it is a potential dye to be used in conjugation to PNA for sitespecific DNA and RNA modulation in an in-vivo setting.
INOR 186
Nanoconfinement of gold on the spatial location of titania nanotubes
Shammi A. Ferdousi1, [email protected], King L. Yeung 1,2. (1) Chemical and
Biomolecular Engineering Dept., The Hong Kong Univ of Sci Tech, Kowloon, Hong
Kong (2) Division of Environment, The Hong Kong University of Science and
Technology, Clear Water Bay, Kowloon, Hong Kong
Spatial doping of gold on the core, surface and interlayer spaces of the titania nanotube was successfully demonstrated
using a new synthesis procedure. The titaniumcontaining precursor was first converted into an intermediate layered
nanostructure followed by their exfoliation and conversion into nanotube structure. Gold precursors with different affinity
for the layered nanostructure are introduced to control the spatial location of the gold in the final nanotube. Precursor with
low affinity to the layered nanostructure will preferentially decorate the nanotube surface, whereas strong affinity will lead
to gold being embedded between the interlayer spaces of the nanotube. Intermediate chemical affinity achieved through
chemical alteration will result in gold slugs or gold nanoclusters filling the core volume of the nanotubes. Spectroscopic
study was carried out to investigate the chemistry and electronic properties of the spatially doped gold titania nanotubes.
INOR 187
Lipid signaling through NM23-H1 as a possible suppressor of metastasis
Michelle R. Friedman1, [email protected], John D. Lapek2, Alan E.
Friedman2. (1) University of Rochester, Rochester, New York, United States (2)
Environmental Medicine, University of Rochester, Rochester, New York, United States
This work defines the potential roles of nucleoside diphosphate kinase A (NM23) and lipid signal molecules in metastasis
regulation. This is significant to understand the mechanism of NM23-H1 metastasis suppression and to discover novel
pathways for clinical stimulation of metastasis suppression. The decrease of NM23-H1 concentration with metastasis has
been documented in many cancers. We believe NM23-H1 regulates metastasis through lipid signal modulation, and will
show the interaction of NM23-H1 with the lysophosphatidic acid receptor 1 (EDG2) and two lipid messengers,
lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC). NM23-H1 is a known histidine and aspartic acid kinase,
and we used our novel detection method to quantitate the H/D phosphorylations gained and lost on the interaction
partners of NM23-H1, focusing on the Ras oncogene network (RON) proteins and EDG2. We have observed the
decrease of NM23-H1 throughout cancer progression and an inverse relationship between NM23-H1 and EDG2. EGD2 is
important in lipid signaling, and the connection between lipid signaling and metastasis has not been fully explored. Our
central hypothesis is that NM23-H1 serves as a go/no go switch for metastasis, using phosphorylations to modulate both
the RON proteins and the lipid signal concentrations through the EDG2 receptor, thereby mediating cellular responses.
Phosphorylationbased regulatory processes could have evolved from ancient bacterial regulatory mechanisms, adapted
to the needs of eukaryotic cells. NM23-H1 regulation through lipid signaling could represent the first characterized human
two-component regulation system. INOR 188
Probing the effects of environments on pKa values: Interaction of aniline with reverse micelles as monitored
using by 1H NMR spectroscopy
Jarukorn Sripradite3,1, Susannah A. Miller1, Anan Tongraar3, Michael D. Johnson2,
Debbie C. Crans1, [email protected]. (1) Colorado State University, Fort
Collins, Colorado, United States (2) Chem Msc 3c, New Mexico State Univ, Las Cruces,
New Mexico, United States (3) chemistry, school of science, Nakhon Ratchasima, Nakhon Ratchasima, Thailand
How interfaces affect the properties of compounds in their vicinity depends on their charge, structure and steric
interactions. In the following study we examined how changing the size (wo) of Aerosol-OT(AOT) reverse micelles affect
the pKa values of compounds located in the micellar interface. The 1H NMR spectra of aniline were examined in aqueous
solution as a function of pH leading to determining the pKa value of the anilinium ion. Complementary studies were
performed in a reverse micellar environment to investigate the effect on the aniline pKa as the compound approaches the
interface. Measurements at different pH values were carried out to determine the pKa of the anilinium ion in reverse
micelles at varying wo sizes (4, 6 and 10 where the w0 = [water]/[AOT]). The results obtained by the 1H NMR spectra
showed the chemical shift pattern of aniline in reverse micelles of Hb > Ha > Hc which is in contrast to that observed in
aqueous solution where Hb > Hc > Ha. These differences suggest that aniline is at least in part penetrates into the
interface. This was subsequently confirmed with 2D NOESY spectroscopy. Using the titration curve generated at each w0
value, the apparant pKa of the anilinium ion in various environments. In summary, the pKa value for protonated aniline
decreases as the reverse micelle size gets smaller., These results are consistent with results obtained for other
compounds investigated in our laboratory.
INOR 189
Electron withdrawing capability of ligating histidine adducts influence the reduction potential of the [2Fe-2S]
cluster of the Rieske protein
Laura M. Hunsicker Wang, Chris Hertz, [email protected], Nicholas
Karagas. Chemistry, Trinity University, San Antonio, Texas, United States
The Rieske protein is an electron transport protein found in the bc1 complex that contains a [2Fe-2S] cluster ligated by two
cysteines and two histidines. The Thermus thermophilus Rieske protein was probed by mutating and chemically modifying
the protein. Different chemical modifiers which result in adducts of the ligating histidines that vary in electron withdrawing
capabilities have been explored. Previous studies showed that diethyl pyrocarbonate (DEPC) both modifies and reduces
the cluster in a pH dependent manner, likely due to the electron withdrawing properties of the adduct. A second modifier,
methyl bromoacetate (MBA), modifies the histidines leaving an adduct that is less electron withdrawing. The wild type and
several mutant proteins that alter the reduction potential of the cluster all react with MBA. These proteins react in a pH
dependent manner like DEPC, but modification with MBA does not result in reduction of the cluster. Presently, work is
being done to purify the MBA-modified Rieske proteins from the unmodified species, which would both confirm the initial
results and potentially help to obtain a crystal structure of the modified protein. The current data indicates that the
reduction potential of the [2Fe-2S] cluster can be altered by having adducts on the histidine ligands of varying electron
withdrawing capabilities. This finding is important as it points to a way that the interaction between the Rieske protein and
its substrate in the bc1 complex might influence how the electron transfer might occur.
INOR 190
Semiquinone stabilization via de novo designed protein scaffolds
Ivan Sokirniy1, [email protected], Gozde Ulas2, William F. Degrado2, Amanda J.
Reig1. (1) Chemistry, Ursinus Colelge, Phoenixville, Pennsylvania, United States (2)
UCSF, San Francisco, California, United States
Catecholic compounds are ubiquitous in nature. Enzymatic oxidation of catechol species is thought to play a role in
formation of reactive oxygen species (ROS) in the cell. Certain natural metalloproteins form the semiquinone (SQ) radical
as a catalytic intermediate, such as in catecholic estrogen-mediated cytotoxicity and mutagenesis. Although synthetic
metal-SQ complexes have been studied for decades, protein-based metal-SQ species are less well characterized. The de
novo designed Due Ferri (DF) scaffold, which contains a bimetallic active site within a four helix bundle motif, has been
used to model the coordination chemistry involved in SQ radical formation and stabilization within a protein-like
environment. The SQ complex can be formed using a variety of first row transition metals and has been detected by
electron paramagnetic resonance and UV-visible absorption spectroscopy. In this work, we have varied the ligand
composition at the metal coordination site in an effort to further understand the factors that contribute to SQ radical
stabilization within the DFsc scaffold. Ultimately, these studies can provide molecular-level insight into the factors that
govern formation, stabilization, and reactivity of biologically-relevant metal-SQ species.
INOR 191
Structural and functional characterizations of 4-His/3-carboxylate G4DFsc proteins
Katie O'Shea, [email protected], Kristen Biernat, Amanda J. Reig. Chemistry, Ursinus College, Collegeville,
Pennsylvania, United States
G4DFsc is a de novo designed, single-chain four-helix bundle protein created to mimic the structural, electronic, and
functional properties of di-iron carboxylate enzymes such as ribonucleotide reducatase and methane monooxygenase.
The active sites of these proteins are comprised of two iron atoms ligated by two histidine and four carboxylate residues at
the center of a four-helix bundle motif. In recent years, additional binuclear non-heme iron enzymes have been discovered
that share similar structural features but exhibit remarkably different reactivity. One example is the Flavin-dependent nitric
oxide reductase FprA. FprA contains a 4-His/3-carboxylate iron-binding motif and catalyzes the reduction of two
equivalents of NO to N2O and H2O. In an attempt to understand how the altered active-site configuration in FprA optimizes
the enzyme for NO reduction relative to O2-dependent oxidation, we have created and characterized two new G4DFsc
variants containing 4-His/3-carboxylate active site configurations. While both proteins remain helical in the presence of
divalent metal ions, they exhibit differences in metal stoichiometry and in their catalytic properties relative to one another
and to the original G4DFsc protein. Preliminary geometric and electronic structure studies provide molecular-level insights
into their functional differences, and will ultimately provide a better understanding of the roles single amino acid residues
play on the stability and reactivity of natural binuclear non-heme iron enzymes.
INOR 192
Creation and characterization of rubrerythrin and symerythrin model proteins
Jenna Pellegrino2, [email protected], Rachel Z. Polinski2, Sabrina N. Cimerol2,
Ari Jacobs3, Edward I. Solomon1, Amanda J. Reig2. (1) Chemistry Dept MC 5080,
Stanford University, Stanford, California, United States (2) Chemistry, Ursinus College,
Collegeville, Pennsylvania, United States (3) Chemistry, Stanford University, Stanford, California, United States
The ferritin-like superfamily (FLSF) is a class of proteins that contain a diiron active site and participate in important
biochemical pathways, including fatty-acid desaturation and the formation of deoxyribonucleotides. The canonical FLSF
sequence contains four carboxylate and two histidine metal-binding ligands in the active site. However, the rubrerythrins
(Rbr) and symerythrin contain one and two additional carboxylate residues, respectively, in their active sites. Interestingly,
these proteins also exhibit enhanced reactivity with hydrogen peroxide relative to other members of the FLSF, but the
correlation between the additional carboxylate residues and the altered functionality is currently not well understood. To
investigate this phenomenon, models for Rbr and Sym were created based on G4DFsc, which is a small, de novodesigned 4-helix bundle protein that mimics the canonical structure and reactivity of FLSF enzymes. Carboxylate
residues, either aspartate (D) or glutamate (E), were introduced at positions G14 and/or G47 to generate Rbr- and Symlike active sites within the G4DFsc bundle. Metalbinding, protein-folding, and reactivity assays have been used to
characterize the geometric and electronic structures of these systems and provide insight into how these particular
carboxylate residues in the G4DFsc active site affect its ability to react with hydrogen peroxide.
INOR 193
Modeling the activity of the tungsten-containing nitrate reductase of Pyrobaculum aerophilium
Kayla Scott1, [email protected], Rebecca Page1, [email protected], Brooklynn Trujillo1,2,
Matthew A. Cranswick1. (1) Department of Chemistry, Colorado State University - Pueblo, Pueblo, Colorado, United
States (2) South High School, Pueblo, Colorado, United States
Mononuclear molybdenum and tungsten enzymes are paramount to the global carbon, nitrogen, and sulfur cycles, with
molybdoenzymes carrying out the bulk of these catalytic cycles. Thermophilic bacteria and hyperthermophilic archaea
thrive at biologically-high temperatures (50-100 °C), in anoxic conditions, and are dependent upon bioavailable tungsten.
From an evolutionary standpoint, these organisms represent some of the oldest species on Earth and give insight into
what early life on Earth may have been like. Until recently, all known Group 6 dependent nitrate reductases (Nar) were
shown to be molybdoenzymes (Mo-Nar), even in thermophiles and hyperthermophiles. It was reasoned that the reduction
potential of tungsten was thought to be too low to carry out the redox chemistry of nitrogen. Recently, a Wcontaining Nar
was isolated and shown to be structurally identical to its Mo-Nar counterpart in Pyrobaculum aerophilium (de Vries, et al,
Biochemistry, 2010, 49, 99119921). This W-Nar was shown to have a two-fold slower turnover rate, but the same KM
value for nitrate (46 mM) as Mo-Nar. We present initial studies of W-Nar activity using an oxotungsten(IV)bis(dithiolene)
complex as a model for the active site of this enzyme, and show that the rate of nitrate turnover is proton dependent.
INOR 194
Toward understanding the reaction mechanism of the tungstoenzyme, acetylene hydratase
E. Christine Vergunst1, [email protected], Brooklynn Trujillo1,2, Matthew A. Cranswick1. (1) Department of
Chemistry, Colorado State University - Pueblo, Pueblo, Colorado, United States (2) South High School, Pueblo, Colorado,
United States
Mononuclear tungsten and molybdenum metalloenzymes play significant roles in the global carbon, nitrogen, and sulfur
cycles, and are found in nearly all organisms. Tungsten is the only known 3 rd row transition metal currently found in
metalloenzymes. All tungstoenzymes known to date are found in anaerobic, thermophilic bacteria and hyperthermophilic
archaea. Acetylene hydratase (AH) is a tungsten-containing enzyme that catalyzes the nonredox hydration of acetylene
(C2H2) to acetaldehyde (CH3CHO). AH is unique in several aspects: (1) it is the only known nonredox Mo/W enzyme, (2) it
is the only known enzyme to use C2H2 as its native substrate, and (3) these organisms use C2H2 as their sole carbon and
energy source, for which AH catalyzes the first step in carbon and energy acquisition. Chemical routes to the hydration of
acetylene are known, but the mechanism of AH remains elusive. To date three reaction mechanisms have been proposed
computationally, two of which invoke the formation of a W IV(η2C2H2) complex. The purpose of this research was to gain a
better understanding of the reaction mechanism of AH by experimentally determining if a viable W IV(η2-C2H2) complex
forms. A known tungsten model complex was utilized that mimics the active site of AH, and this complex was then reacted
with different acetylene derivatives (RC2R’) in order to determine whether coordination between the acetylene derivative
and the tungsten center of the model complex occurred. The identity of the oxygendonor ligand and its role in substrate
coordination was also explored.
INOR 195
Interactions of acrylamide with heme models
Colin Lingafelt, Nan Xu, [email protected]. Penn State Altoona, Altoona, Pennsylvania,
United States
Acrylamide is one of the simplest primary amides. It is a very inquisitive substance for chemists due to the fact that it is
toxic and potential carcinogenic to humans. It has been known that cytochrome P450 2E1, a heme protein, plays a major
role in the metabolism of acrylamide in mice and humans. Recently, an acrylamide analogue was found as a soluble
guanylyl cyclase (sGC) activator, which results in the dilation of blood vessels. We are interested in studying the
interactions between acrylamide and various heme models as well as determining the binding mode of acrylamide to the
heme centers. A series of five- and six-coordinate acrylamide metalloporphyrin complexes has been prepared and
structurally characterized. In addition, the related acetamide metalloporphyrin analogues are also presented and
discussed.
INOR 196
Derivatives of a metallopeptide-based mimic of nickel-containing superoxide dismutase
Tyler Detomasi1, [email protected], Jennifer Schmitt1, Jason M. Shearer2. (1) Chemistry, University of Nevada,
Reno, Reno, Nevada, United States (2) University of Nevada, Reno, Nevada, United States
Superoxide dismutases (SODs) are enzymes that convert the ROS superoxide (O 2–) into H2O2 and O2 through a pingpong type mechanism by alternating between reduced and oxidized redox states. A newly discovered SOD contains a Ni
center (NiSOD) and has been found to be widely expressed in aquatic and soil bacteria. As its name suggests, NiSOD
possesses a redox active Ni-cofactor that cycles between reduced Ni(II) and oxidized Ni(III) oxidation states. In the Ni(II)
oxidation state the nickel ion is found in an N2S2 coordination environment with ligands derived from the protein Nterminal
amine nitrogen, an amidate nitrogen from Cys(2), with two cysteinate sulfur atoms from Cys(2) and Cys(6). We have
extensively used metallopeptide mimics based on the primary NiSOD sequence to probe the reactivity and properties of
NiSOD. This study presents efforts towards diversifying the reactivity and properties of these metallopeptide-based
maquetts. Derivatives of the parent peptide sequence (HCDLPCG) will be prepared that will contain unnatural amino-acid
residues. We will present the design, synthesis, properties, and reactivity of the metallopeptide-based mimics.
INOR 197
Investigation of sugar-Cu(II) and Zn(II) complexes' interactions in aqueous alkaline media
Mayra A. Pedraza, [email protected], Christopher Stewart, Hadi Arman, Ghezai T. Musie. Univ of Texas, San
Antonio, Texas, United States
Sugar-metal ion interactions are not only ubiquitous in biological processes but are also vital in functions such as signal
transduction, intercellular recognition and targets of bacterial or viral infections in cells. In an attempt to understand these
interactions, water soluble synthetic models with carboxylic rich ligand, N-[2-carboxybenzomethyl]-N[carboxymethyl]-βalanine (H3camb), with Zn2+and Cu2+ metal ions have been synthesize and fully characterize using several spectroscopic
and crystallographic techniques. The complexes are found to be very active in interacting with biologically important
sugars such as D-Glucose, D-Xylose, D-Mannose and a polyalcohol enzyme inhibitor (Xylitol) in aqueous alkaline
conditions. The synthesis, characterization and interaction of the complexes with the substrates, determination of binding
constants and specific mode of binding will be discussed.
INOR 198
Synthesis and characterization of BIAN iron dihalide complexes
Michael J. Supej2, [email protected], Kraig A. Wheeler1, Charles E. Schulz3, Helen
M. Hoyt2. (1) Eastern Illinois University, Charleston, Illinois, United States (2) Chemistry,
Knox College, Oswego, Illinois, United States (3) Physics, Knox College, Galesburg, Illinois, United States
Metal complexes bearing α-diimine ligands have recently shown promise in catalysis.
New anhydrous iron dihalide complexes bearing dpp-BIAN and MesAr-BIAN ligands
(dpp = 2,6-diisopropylphenyl; MesAr = 2,4,6-trimethylphenyl;
BIAN=bis(imino)acenaphthene) were prepared and characterized by 1H NMR spectroscopy. The structures of the iron
complexes were investigated by single crystal x-ray diffraction (XRD), Mössbauer spectroscopy, and ongoing work
investigates magnetrometry using a superconducting quantum interference device (SQUID). Currently, the effectiveness
of the complex as a catalyst is pending investigation.
INOR 199
Synthesis and reactivity of iron compounds containing acid functionalized 1,4,7triazacyclononane ligands
Emma Foerster, [email protected], Gerard Rowe. Chemistry and Physics, University of South Carolina Aiken,
Aiken, South Carolina, United States
We have synthesized acid- and ester-functionalized 1,4,7-triazacyclononane (tacn) ligands complexed to iron(II). When
synthesized, this compound will be probed for its ability to form an iron(IV)-terminal-oxo species when exposed to
hydrogen peroxide. We hypothesize that the acid-functionalized iron-tacn will form a hydrogen bond interaction with an
iron(II)-bound peroxide facilitating heterolytic O-O bond cleavage. The ester form, which lacks the ability to form such an
interaction, should not. To identify any iron(IV)-oxo intermediates, these reactions will be monitored using UV/Vis
spectroscopy and Raman spectroscopy. We will also be probing the ability of these compounds to catalyze the oxidation
of substrates such as phosphines, sulfides, and hydrocarbons.
INOR 200
Ligand donor effects in copper(I) and copper(II) complexes of polydentate heteroaromatic-amine ligands in the
ATRP of styrene
Tamuka Chidanguro1, [email protected], Lillian Ma1, Sarah L.
Guillot1,3, Robert D. Pike2, Christopher Goh1, [email protected]. (1) Dept of
Chemistry, Williams College, Williamstown, Massachusetts, United States (2) Colg of
William Mary, Williamsburg, Virginia, United States (3) Chemistry, University of
Wisconsion, Madison, Wisconsin, United States
Atom transfer radical polymerization (ATRP) is a versatile, metal-mediated method of producing polymers with controlled
compositions and molecular weights. Control is attained through the equilibrium between the active radical chain-end
state and a dormant state, established by the reduction-oxidation cycling of the metal catalyst. Ligand structure has been
shown previously to strongly impact the catalysts’ activity and ability to control the polymerization, and polydentate ligands
of amine and pyridine donor moieties have produced some of the most active ATRP catalysts. In this work, a series of
closely related copper(I) and copper(II) bromide complexes of tridentate and tetradentate heterocyclic-amine ligands were
synthesized and characterized, and their utility in the ATRP of styrene explored. We examined how differences in ligand
structure affected the redox potential and structure of the complexes, and how these properties in turn impacted the
efficiency of the ATRP of styrene.
INOR 201
Isolation and characterization of group 13 bis(2-(1-methylimidazolyl)methyl)amine complexes
Nicholas B. Kingsley, [email protected], Tyler J. Doyon. University of MichiganFlint, Flint, Michigan, United States
In recent years there has been a plethora of research in the area of main group organometallic catalysts incorporating
calcium, magnesium, and aluminum. Our research group has particular interest in the use of organoaluminum complexes
in organic transformations. Recently we have started investigating the use of the bis(2-(1methylimidazolyl)methyl)amine
ligands as a support framework for aluminum and gallium alkyls.
We have prepared a series of group 13 ligated complexes (metal = Al, Ga) that will serve as precatalysts for
hydroamination of aminoalkenes. Details of the syntheses and characterization of ligands and complexes will be
presented.
INOR 202
Tuning the photophysical properties in a series of Re(I) charge transfer complexes
Josué Breaux1, [email protected], Alexander Leeds2, James Yarnell1. (1)
Department of Chemistry & Chemistry Research Center, United States Air Force
Academy, Colorado Springs, Colorado, United States (2) Department of Chemistry and Life Science, United States
Military Academy, West Point, New York, United States
The synthesis and photophysical properties of a series of new Re(I)-carbonyl diimine complexes are reported. The ligand
is based on a 1,8-naphthalimide that was covalently attached to a 1,10-phenanthroline. The energy levels of the ligand
have been modified through the addition of electron donating/withdrawing functional groups at the 4 position of the
naphthalimide. Since these bichromophore systems have been found to exhibit “ping-pong” energy transfer, the
modification of only the ligand centered excited state changes the excited state equilibrium, and thus the overall
energetics of the system.
INOR 203
Bidirectional “ping-pong” energy transfer in a Ir(III) charge transfer complex
Alexander Leeds2, [email protected], Josué Breaux 1, James Yarnell1. (1)
Department of Chemistry & Chemistry Research Center, United States Air Force
Academy, Colorado Springs, Colorado, United States (2) Department of Chemistry and Life Science, United States
Military Academy, West Point, New York, United States
The synthesis and photophysical properties of a new luminescent Ir(III) diimine complex covalently attached to one 4piperidinyl-1,8-naphthalimide (PNI) chromophore, [Ir(ppy) 2(phen-PNI)](PF6)2, is presented. This compound represents a
new class of visible light-harvesting Ir(III) chromophores that exhibit greatly enhanced room temperature metal-to-ligand
charge transfer (MLCT) emission lifetimes as a result of intervening ligand centered (LC) triplet states present on the
pendant naphthalimide chromophore. In the Ir(III) complex, the intense singlet fluorescence of the pendant PNI
chromophore is nearly quantitatively quenched and was found to sensitize the MLCTbased photoluminescence. The title
chromophore represents an interesting example of “ping-pong” energy transfer wherein photon excitation first migrates
away from the initially prepared 1LC* excited state and then ultimately returns to this moiety as a longlived excited triplet
which disposes of its energy by equilibrating with the photoluminescent Ir(III) MLCT excited state.
INOR 204
Development of gold(III) complexes containing ligands designed for chelationassisted functionalization of strong,
sp3-hybridized C-H bonds
Rebecca Miller1, [email protected] , Josh E. Thompson1, Matt Sleck1, Alexander Brown1, Shiloh
Summi1, Daniel Ohlson1, Brent Williams1, Isaac Brown1, Erin Nissen1, Thomas Stutzriem1, Arnold L. Rheingold2, David R.
Weinberg1. (1) Department of Physical and Environmental Sciences, Colorado Mesa University, Grand Junction,
Colorado, United States (2) Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla,
California, United States
Novel gold(III) complexes are being developed for the functionalization of strong sp 3hybridized C-H bonds. In order to
facilitate C-H bond activation, these complexes contain ligands that have the potential to direct C-H bonds toward the
gold(III) metal center via chelation. Two types of ligands have been used: 2-tert-butyl-1,10phenanthroline (tBuPhen) and
amide derivatives of 8-aminoquinoline. The reaction of tBuPhen with KAuCl4 in the presence of AgBF4 generates a novel
gold(III) complex in which the tBuPhen ligand is bound to gold(III) in a monodentate fashion. When this complex is
reacted with excess AgBF4 in acetone-d6, the reaction seems to result in the activation of a strong sp 3-hybridized C-H
bond in the tert-butyl substituent of the ligand. Under these conditions, AgBF4 appears to be necessary both for the
production of the initial tBuPhen-gold complex and for the C-H bond activation; however, attempts at metallation of the 8aminoquinoline derived ligands in the presence of AgBF4 lead to the production of undesired oxo-bridged gold(III) dimers.
In the absence of AgBF4 but in solutions containing both an organic solvent and water, the reaction of these ligands with
tetrachloroaurate(III) leads to novel monomeric gold(III) complexes. Further attempts are underway to optimize the
syntheses of the gold(III) complexes and to achieve high-yielding C-H bond activation reactions.
INOR 205
Gold(I) complexes of 2- and 6-mercaptoazulenes: Syntheses, molecular and electronic structures, and reactivity
profiles
Bryce A. Tappan1, [email protected], Andrew D. Spaeth1, Orlando Torres-texidor1,
Nikolay Gerasimchuk2, Mikhail V. Barybin1. (1) Chemistry, University of Kansas,
Lawrence, Kansas, United States (2) Chemistry, Missouri State University, Springfield, Missouri, United States
Azulene is a nonbenzenoid aromatic hydrocarbon that consists of an edge sharing combination of five- and sevenmembered carbon rings. Azulene-containing substances often exhibit unusual photophysical properties due to their
emission from the second singlet excited state, which violates Kasha’s Rule. This presentation will discuss the synthetic
accessibility, molecular and electronic structures, reactivity, as well as photoluminescent behavior of several
mercaptoazulenes and their complexes with monovalent gold. These compounds constitute attractive platforms for
developing new, relatively non-toxic, photoluminescent materials for possible applications in optical sensing.
INOR 206
Molybdate hydrolysis of phosphonothioate neurotoxin
Kristina M. Dill, [email protected], Louis Y. Kuo, Yusef Shari'ati. Chemistry, Lewis & Clark College, Portland, Oregon,
United States
Organophosphate pesticides are neurotoxins that have become ubiquitous in the environment due to their heavy usage.
One class of organophosphates are phosphonothioates R2P(O)(OR1)(SR2), which have been used as agricultural
pesticides. Alkaline hydrolysis has proven to be an effective tool for degrading these esters to yield both P-S and P-O
scission. We report several molybdenum (VI) oxide complexes that catalytically hydrolyze O,S-diethylphenyl
phosphonothioate (DEPP) under extremely mild conditions (pH 7, room temperature). Moreover, this hydrolysis proceeds
exclusively via P-S scission to yield an innocuous phosphonate product; the leaving group is ethanethiolate. The aqueous
speciation of molybdates is extremely sensitive to pH, and it yields Mo 8O264-, Mo7O246- and MoO42- at pH 4.0, 5,5 and 7.5,
respectively. In this connection we found the maximal rate of DEPP hydrolysis by molybdates occurs at pH 7.5 - 8.0 which
indicates the monomeric MoO42- is the active species. That MoO42- did not bind to the ethanethiol of DEPP hydrolysis is
consistent with the turnover results. Parac-Vogt has seen similar catalytic hydrolysis of peptides, and attributes it to Lewis
acid activation of amides through coordination to the Mo(VI) center. To this end, we will present O-18 labelling
studies/results on Ph-P(18O)(OEt)(SEt) that delineate this hypothetical mode of activation of phosphonothioates. In
addition, structure-activity results on the hydrolysis of derivatized phenyl phosphonothioates by MoO 42- seek to confirm the
presence/absence of a putative Mo-S interaction that promotes DEPP hydrolysis.
INOR 207
Theoretical investigation of trends in the HOMO to LUMO transition energies of tris(2,2’-bipyridyl)ruthenium(II)
complexes containing various substituted ligands
Jon Gold1, [email protected], Christopher Wisniewski2, Joseph Sluzevich2. (1) East
Stroudsburg UNiversity, E. Stroudsburg, Pennsylvania, United States (2) East Stroudsburg University, Stroudsburg,
Pennsylvania, United States
A theoretical investigation of various modified forms of substituted forms of tris(2,2’bipyridyl)ruthenium(II) were performed
using PM3 (semi-empirical) and ab-initio levels of calculation. Selected molecules included single and multiple
substitutions at one, two and three bipyridine moieties. The effects on HOMO and LUMO orbital energies differences were
studied as a function of substitution. Substitutions included varying the numbers and types of halogens on the bypyridines.
In addition the effect of the addition of conjugated propenes to the bipyridine was investigated and compared to changes
observed by the addition of saturated chains. A complex behavior attributed to both inductive and conjugation effects was
observed for these modelled complexes. Substitution of hydrogen by fluorine was particularly anomalous. However, the
substitutions did not affect the HOMO or LUMO orbitals’ essential ligand-based ππ* character. INOR 208
Developing a method of copper(II) oxidation catalyst synthesis
Constance Anderson1, [email protected], Joseph Rumreich1, [email protected], Jeffrey Bodwin2. (1)
Minnesota State University Moorhead,
Andover, Minnesota, United States (2) Minnesota State Univ Moorhead, Moorhead, Minnesota, United States
Transition metal coordination complexes are widely studied as catalysts due to their readily accessible electronic
properties and facile tuning of physical properties. This research explores the synthesis of 2-picolinamide ligands and their
copper(II) compounds. Initial studies have shown interesting optical properties of the 2picolinamide ligands and their
precursors that will be tuned via substitution to modify the electronic properties of the ligand as well as steric accessibility
of the Cu(II) binding site and general solubility of the ligands and resulting complexes. Successfully synthesized
complexes will be screened for catalytic activity in oxidation of a variety of substrates.
INOR 209
Probing the selectivity of luminescent lanthanide complexes toward biologically relevant anions
Katherine R. Johnson, [email protected], Kayla H. Felix, Eric J.
Werner. The University of Tampa, Tampa, Florida, United States
There is a vast array of applications for lanthanides because of their luminescence properties. One application is the
potential of the complex to act as a biosensor. A complex selective for a particular substrate can be used to determine if
that substrate is present in an unknown solution and to quantify its presence. For example, complexes can exhibit
selectivity towards a biologically relevant anion and respond to binding through changes in luminescence properties. Once
attached to the metal within a complex, a competitive anion can replace water molecules from the coordination sphere
which results in a reduction of luminescence quenching. The consequent increase of luminescence can be monitored and
determine the binding efficiency and selectivity of a
particular lanthanide complex. In this study, a tripodal pyridine/Schiff base ligand for lanthanide metal complexation was
synthesized and its potential sensor applications were explored. This complex was made from the TRIPy ligand (TRENtris-iminepyridine) which effectively binds Eu(III) in a hexadentate manner, leaving room for solvent water molecules to
coordinate to the exposed metal. Additional anions have the ability to attach to the complex via the empty Eu(III)
coordination sphere. Based upon preliminary studies, it was determined that the TRIPy complex exhibited a larger change
in luminescence intensity when exposed to oxalate versus other biologically relevant anions tested suggesting a
selectivity for the oxalate anion. To further explore selectivity toward anionic oxygen donor anions, additional binding
studies were performed in MES buffer with solutions of malonate, succinate, and lactate. Anion binding studies of mixed
anion solutions were also explored and the results will be discussed.
INOR 210
Rational design of catalysts for water-gas shift reaction
Joshua Fox, Adriana Dinescu, [email protected]. Wilkes University, Wilkes Barre, Pennsylvania, United
States
Molybdenum-containing carbon monoxide dehydrogenase catalyses a reaction similar to water-gas shift reaction.
Biomimetic catalysts, in which ligands and metal centers of the dithiolene-Mo-Cu model inspired from molybdopterin
cofactor are replaced by analogous structures, can increase the catalytic activity of the native model. A measure of the
catalytic activity is based on the structure and energy of the transition state of the identified rate-limiting step. By
employing density functional theory, evaluation of electronic properties of intermediates and transition states of various
inorganic complexes with different ligands and metal centers yield a series of promising catalysts for water-gas shift
reaction. Most analogous catalysts show a better performance due to avoiding the low energy intermediate that is formed
with the dithiolene-Mo-Cu model.
INOR 211
Luminescence and extraction properties of novel tripodal CMPO ligands
David A. Hardy2, [email protected], Michael T. Peruzzi1, Shelby N.
McGraw2, Shannon M. Biros1, Eric J. Werner2. (1) Grand Valley State University,
Allendale, Michigan, United States (2) The University of Tampa, Tampa, Florida, United
States
With the gradual development of alternative energy, our energy needs still rely heavily on fossil fuel and nuclear based
methods. The spent fuel from nuclear power generation in particular contains mixtures of lanthanides (Ln) and actinides
(An) which complicate storage and processing. Currently, the separation of these heavy metals are done by using liquidliquid extraction methods that employ carbamoylmethylphosphine oxide (CMPO) derived ligands. While these ligands are
known to extract An ions, more efficient methods are needed to increase selectivity of extraction and potentially separate
the lanthanides. We are studying extraction efficiencies of the f-elements with tripodal ligands based on the classic CMPO
chelating group. In the attempt to make nuclear energy viable as a legitimate energy source, these ligands are designed
to selectively and strongly bind Ln and An ions to process existing and future nuclear waste. Of these ligands, some have
shown selectivity for terbium(III) over the remaining Ln ions. In addition to extraction efficiencies, we are studying
luminescence properties of these ligands by fluorescence spectroscopy. These studies provide insight into the general
solution chemistry and coordination numbers of our novel complexes.
INOR 212
Utilizing diphenylacetate lability in the synthesis of mixed ligand copper (II) dimers
Minda Chen, [email protected], Thomas W. Clayton. Chemistry, Knox College,
Galesburg, Illinois, United States
Copper(II) carboxylates react with copper(II) chloride dihydrate to form orange intermediate complexes with bridging
carboxlylate ligands detected by FT-IR. The intermediate complexes react with stoichiometric amounts of carboxylate
salts with chain lengths varying from 4-16 to produce heteroleptic dimers which have been characterized by elemental
analysis, DSC and polarized optical microscopy.
Heteroleptic products containing diphenylacetate as one of the carboxylate ligands may exhibit liquid crystalline
mesophases depending upon chain length for the other ligand and the number of diphenyl acetate ligands.
INOR 213
Synthesis, characterization, and photochemical studies of solvated dinuclear Ru(II) compounds with quinoxaline
and pyrazine based bridging ligands
Sayan Saha2, [email protected], Bruno Pena2, Bryan A. Albani1, Claudia
Turro1, Kim R. Dunbar2. (1) The Ohio State University, Columbus, Ohio, United States (2) Texas A&M University, College
Station, Texas, United States
Metal based drugs have shown great promise as anticancer chemotherapeutic agents over the past five decades. Due to
the lack of specificity and detrimental side effects of platinum drugs which are heavily used in the chemotherapeutic
regimens, however, scientists are striving to find alternatives. On that topic, Ru-based drugs have emerged as a potential
alternative to Pt therapy due to fewer side effects as well as more activity towards Pt drug resistant cells. Ruthenium
complexes have reactive excited states, such that selective activation of Ru drugs by means of visible light, an approach
known as Photodynamic Therapy (PDT), is a promising strategy for endoscopically accessible tumors. 1 One issue
however is that PDT therapy relies on singlet oxygen (1O2) generation and a problem arises with many malignant tumors
which are often hypoxic and thus new strategies are in order. In this vein, our group has developed a series of solvated
dinuclear Ru(II) compounds, [Ru2(μ-BL)(NCCH3)8](PF6)4 [(μ-BL) = dpq (2,3di(pyridin-2-yl)quinoxaline) (1); dpb (2,3di(pyridin-2-yl)benzo[g]quinoxaline) (2)] and
[Ru2(μ-tppz)(NCCH3)6](PF6)4 [(μ-tppz)= (2,3,5,6-tetra(pyridin-2-yl)pyrazine) (3)]. By using highly electron withdrawing
ligands we can red-shift the 1MLCT transition closer to the therapeutic window (600 nm- 850nm) for PDT. Irradiation of the
compound with a suitable wavelength of light can photorealease “caged” acetonitrile molecules inside the cell and the
resulting coordinatively unsaturated compound can bind to DNA in a manner akin to cisplatin. 2 NMR techniques,
electronic absorption spectroscopy, electrochemical measurements, elemental analysis and X-ray diffraction were used to
characterize the compounds. The crystal structures of (1) and (3) were further employed to interpret our results based on
computational analyses. The photochemical studies were performed with compound (3) using NMR techniques and
electronic absorption
irradiation. Compounds
(1) and (2) are also under investigation and recent results will be presented.
3
Liu, Y.; Turner, D.; Singh, T.; Angeles-Boza, A.; Chouai, A.; Dunbar, K.; Turro, C. J. Am. Chem. Soc., 2009, 131, 26-27.
INOR 214
Computational exploration of the noncovalent interactions involved in the inhibition of malate synthase for
treatment of tuberculosis Jill F. Ellenbarger1, [email protected], Steven E. Wheeler1, James C. Sacchettini1,2,
Kim R. Dunbar1. (1) Department of Chemistry, Texas A&M University,
College Station, Texas, United States (2) Department of Biochemistry and Biophysics,
Texas A&M University, College Station, Texas, United States
The continued global tuberculosis epidemic has motivated drug design targeting specific enzymatic processes of the
infectious bacterium, Mycobacterium tuberculosis. One such process within the tricarboxylic acid (TCA) cycle, the
1
Dolmans, D. E. J. G. J.; Fukumura, D.; Jain, R. K. Nat. Rev. Cancer 2003, 3, 380-387.
Sgambellone, M. A.; David, A.; Garner, R. N.; Dunbar, K. R.; Turro, C. J. Am. Chem.
Soc. 2013, 135, 11274-11282.
2
glyoxylate shunt, has garnered particular interest. The glyoxylate shunt bypasses two traditional CO 2generating steps in
the TCA cycle by incorporating a molecule of acetyl-coenzyme A as the carbon source, therefore propagating the TCA
cycle under carbon limiting conditions during chronic infection. Of the two enzymes involved in the glyoxylate shunt,
malate synthase was targeted for structure-based drug design by the Sacchettini lab for its large, conformationally static
active site1. Inhibition was observed for phenyl-diketo acid and various phenyl-substituted derivatives. Upon inhibition, the
diketo acid backbone binds to the catalytic Mg2+ ion and participates in hydrogen-bonding interactions with nearby
residues while the terminal aryl group participates in an anion-π interaction with an aspartate residue. Previous
computational studies by another group identified the importance of long range electrostatic interactions during inhibition2.
In collaboration with the Wheeler and Sacchettini labs, we are further exploring the energetic underpinnings of the
interactions involved in enzymatic inhibition for thirteen inhibitors, including the electrostatic interactions with the Mg 2+ ion,
the series of hydrogen bonding interactions along the backbone, and the anion-π interaction present at the aryl moiety.
From the series of inhibited protein crystal structures, the appropriate model active site is extracted and analyzed
computationally using a DFT method well established in handling non-covalent interactions (M06-2X/6-31G+(d)). Analysis
of the anion-π interaction in response to substitution on the aryl moiety is pursued to develop an efficient screening
method for the determination of new, potent inhibitors for further drug development targeting the glyoxylate shunt in
Mycobacterium tuberculosis.
Krieger, I. V. et al. Chemistry & Biology, 2012, 19, 1556–1567. Estarellas, C. et al. ChemPhysChem, 2013, 14, 145-154.
INOR 215
“Reinventing the wheel” with heptacyanomolybdate(III)
David K. Kempe, [email protected], Hanhua Zhao, Toby J. Woods, Mohamed R.
Saber, Kim R. Dunbar. Department of Chemistry, Texas A&M University, College Station, Texas, United States
Single molecule magnets (SMMs) are important for applications in high density data storage and spintronics, but
significant improvement is still necessary if these types of molecules are to be used in devices 1. Although there are
proposed building blocks that could improve these properties such as [Mo(CN)7]4- these efforts remain underexplored due
to synthetic difficulties in isolating pure, crystalline products. The work represented here involves a new compound that
incorporates [Mo(CN)7]4- by mimicking a structure that is known for another cyanometallate. In 2010, a molecular wheel
compound containing [W(CN)8]4- and Ni(L)2+ was published,2 but no magnetic data were reported due to the diamagnetic
nature of the tungsten containing ion which would render such information relatively uninteresting. The structure
incorporates six [W(CN)8]4- and twelve Ni(L)2+ units and the substitution of [W(CN)8]4- for [Mo(CN)7]4- produced a similar
molecular wheel which exhibits ferromagnetic coupling. Future plans involve creating a series with other 3d metals and
modifications to the ligand used to chelate those metals. Given the track record of discrete molecules that incorporate
[Mo(CN)7]4-, further modifications are expected to lead to improved magnetic properties.
1 Gatteschi, D.; Bogani, L.; Cornia, A.; Mannini, M.; Sorace, L.; Sessoli, R. Solid State Sci. 2008, 10, 1701-1709.
2 Zhang, D.-P.; Zhang, L.-F.; Li, G.-L.; Ni, Z.-H. Chem. Comm. 2013, 49, 9582-9584.
Figure 1. Structure of the [Ni(L)]12[Mo(CN)7]6 wheel.
INOR 216
Cyanide-bridged single chain magnets with hexacyanomanganate
Yuanzhu Zhang2, [email protected], Hanhua Zhao3, Edward S. Funck2, Kim
R. Dunbar1. (1) Texas AM Univ, College Station, Texas, United States (2) Chemistry, Texas A&M University, College
Station, Texas, United States
Cyanometalate complexes provide a convenient platform for the isolation of structurally related materials by
using a building-block or modular synthetic approach. Introduction of suitable chelate/capping ligands on
metallic centers may effectively tune the ligand field, redox potentials, as well as electronic configurations
without changing structural archetypes. As such, targeted materials with expected physical properties can be
systematically studied. Since the first cyanide-bridged single chain magnet (SCM) with the formula of
{[FeIII(L)(CN)4]2CoII(H2O)2}·4H2O (L = 2,2¢-bipyridine or 1,10-phenanthroline), which consists of neutral cyanidebridged FeIII-CoII double zigzag chains, or the “so-called” 4,2-ribbon chain, was reported in 2003, several related
cyanide SCMs have been developed with the same basic architecture that contain a favourable parallel
arrangement of the anisotropic metal units. We recently prepared a new tape-like SCM by introducing
[MnIII(CN)6]3- anions into the centrosymmetric linear trinuclear compound [(tptz)2MnII3(OAc)6] (1, tptz = 2,4,6-tri(2pyridyl) -1,3,5triazine): {[(tptz)MnII(H2O)MnIII(CN)6]2MnII(H2O)2}n×4nMeOH×2nH2O (2). Magnetic studies reveal that 2
exhibits long-range magnetic ordering below 5.1 K due to both intra- and inter-chain antiferromagnetic couplings
as well as SCM behaviour at lower temperatures with an effective energy barrier of 40.5(7) K.
Figure 1 X-ray structure of 1 and 2 and variable temperature AC susceptibilities for 2
INOR 217
Ligand effects and geometrical control of the magnetic anisotropy in mononuclear SMMs
Mohamed R. Saber, [email protected], Kim R. Dunbar. Chemistry, Texas AM University, College Station, Texas,
United States
During the quest for SMMs with enhanced properties it became obvious that magnetic anisotropy is the most important
criterion for engendering slow relaxation of the magnetization, a characteristic that is affected by the molecular symmetry,
the ligand field and the single ion effects of spin-orbit coupling (SOC) and zero-field splitting (ZFS).1 Several routes have
been employed to enhance the global anisotropy of molecular materials such as increasing single-ion anisotropy via
incorporating heavier 4d and 5d transition metal ions. In other studies, reports of slow paramagnetic relaxation of the
magnetization in transition metal–based mononuclear complexes provide ample evidence for the importance of
geometrical control of the local anisotropy in metal complexes. Indeed, the rational design of low coordinate iron
complexes has led to an extraordinary example of a mononuclear SMM with an energy barrier that even surpasses the
benchmark Mn12-acetate SMM. Attaching heavier halides with their larger spin orbit coupling parameters to metal centers
is known to enhance the magnetic anisotropy of metal complexes. We report herein a magnetic study of a series of
mononuclear distorted tetrahedral cobalt complexes; Co(L) 2I2 (L = quinoline (1), triphenylphosphine (2) and
triphenylarsine (3)).2 The group 15 donor atom was varied from the first row to the third row element in order to investigate
the effect of the
softness and larger spin orbit coupling constant of the ligand with heavier donor atoms on the global magnetic anisotropy
of the metal complexes. The axial ZFS parameter D was found to vary from +9.2 cm -1 in 1 to – 36.9 cm-1 in 2 and - 74.7
cm-1 in 3 which indicates that ligands with heavier and softer main group donor atoms significantly enhance the global
magnetic anisotropy of the metal complexes. Compounds 2 and 3 exhibit slow relaxation of the magnetization under an
applied dc field up to 4 K, indicating SMM behavior.
(1) Ruiz, E.; Cirera, J.; Cano, J.; Alvarez, S.; Loose, C.; Kortus, J. Chem. Commun.
2008, 0, 52.
(2) Saber, M. R.; Dunbar, K. R. Chem. Commun. 2014, 50, 12266.
Molecular structure (left) and Frequency-dependent AC susceptibility (right) of 3
INOR 218
Semiconducting and magnetic properties in metal-TCNQ-based functional materials
Xuan Zhang1, [email protected], Hanhua Zhao1, Zhao-Xi Wang2,1, YuanZhu Zhang1, Kim R. Dunbar1. (1)
Department of Chemistry, Texas A&M University,
College Station, Texas, United States (2) Department of Chemistry, Shanghai University, Shanghai, China
Molecule-based multifunctional materials are of high interest because of the coexistence of two or more properties such
as magnetic, electrical conducting, ferroelectric or optical properties. TCNQ (tetracyanoquinodimethane) is an excellent
electron acceptor that has been extensively studied in electrically conducting/switching and magnetic materials due to the
fact that its radical form can either stack into electron conducting pathways or act as a spin carrier to mediate magnetic
coupling between paramagnetic metal ions.
A novel semiconductor Cd2(TCNQ)3.5(H2O)2 with non-integer valences of TCNQ was synthesized which is the first
example that exhibits four bridging modes of TCNQ in one structure. Despite the rather large stacking distance of 3.687(1)
Å between the two μ3TCNQ, which constitute a “broken link” in the electron conducting pathway, the semiconductor
exhibits a room temperature conductivity of 5.8×10-3 S∙cm-1.
In another vein, we synthesized a promising quasi-1-D compound by the self-assembly of organic TCNQF-• radicals and
the anisotropic [Tb(valpn)Cu]3+ dinuclear cations. Magnetic characterizations revealed that the effective energy barrier for
the reversal of the magnetization in this rare hetero-tri-spin compound was significantly larger than the reported singlemolecule magnet with the isolated ‘TbCu’ dinuclear cores and the supramolecular stacking interactions of TCNQF -•
radicals was found to be essential for the 1-D correlation of the magnetic behavior.
INOR 219
Series of trigonal bipyramidal Co(II) complexes that display SMM behavior
Maria F. Ballesteros-Rivas, [email protected], Toby J. Woods, Kim
R. Dunbar. Texas A&M University, College Station, Texas, United States
In recent years small molecules have been explored as promising molecular magnetic materials (SMMs). Molecules with a
single paramagnetic center responsible for the SMM behavior provide simple model systems for studying magnetic
anisotropy. Reports in the literature of complexes with a single lanthanide ion exhibiting SMM behavior and of SMM
behavior in mononuclear Co(II) complexes are increasing rapidly. Several iron complexes and very recently a Ni(I)
complex were also reported to show SMM behavior.
In this work, we prepared the isostructural series of complexes,
[Co(TPMA)(MeCN)](BF4)2 and [Co(TPMA)(X)](X) (TPMA = tris-(2-pyridylmethyl)amine, X = Cl-, Br-, I-) to explore the
effects of the axial ligand on the magnetic properties. In all of the complexes the Co(II) ion exists in a trigonal bipyramidal
(TBP) geometry, with local C3 symmetry and small deviations in the equatorial bond angles. The four compounds behave
as SMMs in the presence of a static DC field. Comparison with other previously reported Co(II) complexes with TBP
coordination environments reveal that relatively minor structural changes can lead to distinct differences in the magnetic
properties. This poster will present and discuss the SMM behavior of four Co(II) complexes with a TBP geometry.
Thermal ellipsoid plot of the cationic unit of [Co(TPMA)(MeCN)](BF 4)2
INOR 220
Dinuclear lanthanide complexes containing a radical bridging ligand
Toby J. Woods, [email protected], Maria F. Ballesteros-Rivas, Kim R.
Dunbar. Texas A&M University, College Station, Texas, United States
Research on Single Molecule Magnets (SMMs) is of high interest due to the possibility of using bistable molecules for new
types of memory devices and for quantum computing applications. In the years since the initial report of SMM behavior in
Mn12Ac it has become apparent that molecular anisotropy is an important aspect of designing SMMs with enhanced
properties. The inherent anisotropy of lanthanide ions renders them excellent prospects for SMMs with higher operating
temperatures. Another ingredient that contributes to higher SMM blocking temperatures is a strong magnetic exchange
between the spin carriers. Due to the contracted nature of the f orbitals of lanthanide ions, exchange coupling between
them is generally quite weak which prevents the rare earth ions from realizing their full potential as magnetic molecules. It
has recently been shown that the use of an additional spin carrier as a bridge, e.g. an organic radical, can greatly increase
the magnitude of the interaction between lanthanide ions. In fact, the use of an organic radical bridge between two Tb(III)
ions led to the observation of a magnetic hysteresis loop at temperatures up to 14 K which is the current record. The focus
of this presentation is a description of our efforts to use the stable, radical anion form of bmtz (bmtz = 3,6-bis(2’-pyrimidyl)1,2,4,5-tetrazine) as a bridge between two lanthanide ions. Our goal is to understand how the nature of the radical orbital
affects the strength of the magnetic coupling between lanthanide centers and, by extension, how the coupling strength
affects SMM behavior.
INOR 221
Biological studies of dirhodium(II,II) based compounds and their applications as photochemotherapeutic agents
Amanda David1, [email protected], Zhanyong Li1, Bruno Pena1, JeanPhilippe Pellois2, Kim R. Dunbar1. (1) Chemistry, Texas A&M University, College
Station, Texas, United States (2) Biochemistry & Biophysics, Texas A&M University, College Station, Texas, United States
Much effort over the past five decades has been devoted to the design and synthesis of metal-based anticancer agents.
Metal-based antitumor agents can target DNA by forming covalent lesions or by intercalating into the double helix of DNA.
Current therapies have limitations stemming from the lack of specificity and systemic toxicity. Our group has shown that
Rh2(µ-O2CCH3)4 and other derivatives containing electron accepting ligands can bind in vitro to nucleotides, form intrastrand DNA cross-links and interact with other biologically relevant molecules. As part of our interest in metal anticancer
agents, we have targeted a series of dirhodium(II,II) complexes with different types of bridging and chelating ligands in the
same molecule, work that led to the isolation of families of such compounds that are inactive towards cancer cells in the
dark but which are toxic upon irradiation has been synthesized and characterized. Formamidinate compounds of the type
[Rh2(F4form)(µ-O2CCH3)(N-N)2][OAc]2with electron accepting chelating ligands (N-N) (N-N = dpq (dipyrido[3,2-f:2',3'h]quinoxaline), dppz (dipyrido[3,2-a:2’,3’-c]phenazine) and dppn (benzo[i]dipyrido[3,2a:2’,3’-h]quinoxaline)) were studied as
well as the partial paddlewheels [Rh2(2pyrrolidinato)4(CH3CN)2],[Rh2(2-pyrrolidinato)3(CH3CN)6]2+ and (7)
[Rh2(2pyrrolidinato)2(η1-pyrrolidinato)(CH3CN)5]2+
[Rh2(F4form)(µ-O2CCH3)(CH3CN)6]2+(8)
and
[Rh2(PC6H4Ph2)(µO2CCH3)(CH3CN)6]2+. The cytostatic effect of these compounds were tested against cervical and ovarian cancer cells in the
dark and also upon irradiation. Fluorescence probes were used to elucidate possible cell death mechanisms of action.
NIC/ADR-Res cells were incubated with the compounds for 2 h in the dark and then irradiated for 1 h. The compound
([Rh2(F4form)(µO2CCH3)(dppn)2][OAc]2) is the most effective at inhibiting cell growth with an LC50 value of 336 ± 55 µM in the dark and 19
± 4 µM upon irradiation. The results of a JC-1 assay indicate that several of the compounds induce changes in the
mitochondrial membrane potential as early as 2 h as observed from a time lapse experiment. Annexin V binding studies
indicate that t some of the compounds induces cell death through mitochondrial mediated pathways.
INOR 222
Structural study of Prussian blue
Andrew Brown1, [email protected], Han-hua Zhao3, Kim R. Dunbar2. (1)
Chemistry Department, Texas AM University, College Station, Texas, United States (2)
Texas AM Univ, College Station, Texas, United States (3) Texas A&M University, College Station, Texas, United States
Prussian blue, the inorganic evergreen, is one of the oldest known coordination compounds. Throughout history this
compound has been most famous for its use as a blue pigment. Despite being known since the early 1700s, Prussian
blue has been reported with a variety of structural characterization problems due to the varying potassium content,
defective sites, and particle size. Each of these properties in turn, have a profound effect on the shade of blue that is
observed in the resulting products. This presentation will shed light on the structural variances of Prussian blue and
support the notion that the compound is not described by a single formulation, but rather a spectrum of possibilities
dependent on synthetic preparation. Prussian blue compounds have been prepared with 1-5 point defects and levels of
hydration ranging from 6 to 28 moles of water. In one special case, single-crystal X-ray diffraction solved for the socalled
“soluble” Prussian blue, KFeIII[FeII(CN)6]. Six sodium containing Prussian blue analogs have also been prepared with
varying levels of hydration ranging from 2 to 15 moles of water. Thermal gravimetric analysis (TGA), elemental analysis,
and magnetic data are presented for the determination of molecular formulas and to ascertain the dependence of the
Curie temperature on structural variance.
INOR 223
Solvent effects on the spin transitions in discrete cyanide-based magnetic material
Codi Sanders2, [email protected], Heather Stout3, Catalina Achim3, Doros Petasis1, Kim R. Dunbar2. (1)
Allegheny Colg, Meadville, Pennsylvania, United States
(2) Texas AM University, College Station, Texas, United States (3) Carnegie Mellon University, Pittsburgh, Pennsylvania,
United States
Prussian blue (PB) type extended structures containing the [Fe(CN) 6]3- anion have been studied extensively over the
years and have been shown to behave as high temperature magnets as well as to exhibit many interesting magnetic
phenomena including spin crossover (SCO), charge transfer induced spin transition (CTIST), cyanide linkage isomerism
and photomagnetic behavior. Our group has popularized a discrete molecule emanating from the Prussian blue archetype
which have been shown to mimic the magnetic behavior exhibited by their extended analogs. These discrete molecules
with trigonal bipyramidal (TBP) geometry and formula [MII(tmphen)2]3[MIII(CN)6]2, (M3M2), (tmphen = 3,4,7,8tetramethylphenanthroline) offer several advantages over their extended counterparts such as increased solubility for
processing into films and lower densities; their properties are generally more easily tuned synthetically and they offer
greater accuracy in modeling magnetic properties.
Recently, we discovered that the SCO and CTIST events which occur in TBPs can be finely tuned or changed completely
by the solvent introduced into the interstitial sites of the molecules. We have found that the mother liquor in these
molecules undergo solvent exchange with many different solvents which alter the spin transitions in these molecules,
whether it be through electron transfer or SCO in origin. The work discussed here probes the effect of solvent exchange
or solvent loss on the spin transitions in TBPs of formula Fe3M2, where MIII = Co, Fe, Ru and Os. The figures below depict
DC temperature dependent magnetic susceptibility for TBPs of formula Fe3Ru2 (left), which indicates the effect of solvent
loss and Fe3Co2 (right), which reveals the effect of solvent exchange on the spin transitions inherent in these molecules.
INOR 224
Exploring and enhancing the functionality of tetrazine molecular switches
Christopher Benson2, [email protected], Amar H. Flood1. (1) Indiana Univ,
Bloomington, Indiana, United States (2) Chemistry, Indiana University, Bloomington, Indiana, United States
The proliferation of stimuli-responsive supramolecular switches has been driven by their potential to serve as functional
components in molecular-scale machinery. However, fulfillment of these ambitions has been slow to come as the bulk of
these switches typically demonstrate rather limited functions, and few have been investigated in-depth to better
understand the mechanism of their operation. Our lab has previously published several studies on the behavior of coppertemplated tetrazine [2]pseudorotaxane switches, but recently has greatly expanded the scope of their function. In the first
instance, discovery of a second complimentary recognition site (2,2’-bipyridine) for the switch enables [2]pseudorotaxane
directional switching not previously possible, and kinetic characterization of the switching processes also revealed
bilability in the switching mechanism. The expansion of this new site also showed “double switching“ behavior, permitting
access to a [3]pseudorotaxane morphology. Finally, this mechanistic understanding revealed the possibility of pathway
selection in molecular switching, allowing us to choose the mechanism by which switching takes place. The broad
functionality of this system suggests that this switching motif could be applied to a variety of possible molecular machine
designs.
INOR 225
Imaging studies of metal-containing nanoparticle as multimodal platforms for biomedical applications
Premrudee Promdet3,4, [email protected], Bárbara Rodríguez-García5,
Alexandria Henry6,10, Carl Blumenfeld7, Rex A. Moats8, Robert H. Grubbs2, Harry B.
Gray1,9, José Ramón Galán-Mascarós5, Karn Sorasaenee4,1. (3) Chemistry,
Chulalongkorn University, Pasadena, California, United States (4) Radiology,
Translational Biomedical Imaging Laboratory, The Saban Research Institute,Children's
Hospital Los Angeles, Keck School of Medicine of USC, Los Angeles, California, United
States (5) Institut Català d’Investigació Química, Tarragona, Spain (6) Radiology,
Translational Biomedical Imaging Laboratory, The Saban Research Institute, Children’s
Hospital Los Angeles, Keck School of Medicine of USC, Los Angeles, California, United
States (7) Chemistry, California Institute of Technology, Pasadena, California, United
States (9) Beckman Institute, California Institute of Technology, Pasadena, California, United States (10) University of
California, Los Angeles, California, United States
Molecular imaging contrast agents have been used for a variety of in vivo imaging applications. Magnetic resonance (MR),
fluorescence optical, and x-ray computed tomography (CT) imaging techniques are among the most commonly used
imaging modalities in biomedical research. Here, we present the studies of metal oxide, such as TiO 2 and BaTiO3, as well
as Prussian blue nanoparticles as potential multimodal platforms for molecular imaging. Surface functionalization of the
metal oxide nanoparticles with fluorescent molecules will also be addressed. By using both twophoton and confocal
fluorescence microscopy, we were able to produce second harmonic generation and fluorescence images of the selected
nanoparticles. Moreover, our studies of the Prussian-blue nanoparticles suggested that these nanomaterials could
potentially be used as multimodal imaging contrast agents for MRI, µCT and optical imaging.
INOR 226
Investigating the magnetic properties of metal complexes containing a
tris(amido)amine ligand
Francisco J. Birk2, [email protected], Kelsey Schulte2, Dawid
Pinkowicz1, Kim R. Dunbar2. (1) Jagiellonian University, Krakow, Poland (2) Chemistry, Texas A&M University, College
Station, Texas, United States
Molecular magnetism is an interdisciplinary field with promising applications in quantum computing, spintronics, and single
molecule magnets (SMMs). SMMs display magnetic bistability at the molecular level and possess an energy barrier for
reversal between magnetic states that depends on the spin and negative zero-field splitting (D) parameters.1 Recent
theoretical efforts to understand the effects of different coordination geometries and electronic configurations on SMM
behavior have led to predictions that transition metal compounds in a trigonal pyramidal geometry with specific electronic
configurations can exhibit either large positive or large negative D values. 2 Using the ligand3 (Me3SiNCH2CH2)3N used by
Schrock and co-workers, we are testing this hypothesis by synthesizing the 3d transition metals of Mn, Fe, Co, and Ni with
this ligand in which the trigonal symmetry is slightly distorted towards C s due to coordination of the Li(THF) cation. The
synthesis and magnetic properties of these compounds will be presented and discussed, including which compounds
show SMM behavior and the agreement between theory and experiment.
References:
1. Miller, J.S., Gatteschi, D. Chem. Soc. Rev., 2011, 40, 3065-3066.
2. Gomez-Coca, S.; Cremades, E.; Aliaga-Alcalde, N.; Ruiz, E. J. Am. Chem. Soc. 2013, 135, 7010-7018.
3. Greco, G. E.; O’Donoghue, M. B.; Seidel, S. W.; Davis, W. M., Schrock, R. R., Organometallics 2000, 19, 1132-1149.
INOR 227
Anion-π contacts in supramolecular architectures
Helen T. Chifotides, [email protected]. Texas AM Univ, College Station,
Texas, United States
In light of our broad interest in anion-π interactions, which are the newly recognized noncovalent contacts in
supramolecular chemistry, we are studying several supramolecular systems that are amenable to these interactions. 1,2
We surveyed several aromatic systems favoring anion-π contacts and have explored the subtle interplay between ligand
p-acidity, anion identity, and metal ions in mediating the ensuing architectures. These ligands afford unusual molecular
metallacycles that are highly stable in solution, yet exhibit remarkable flexibility allowing them to be interconverted to other
ring sizes, a process that is governed by anion encapsulation.3 Collective X-ray crystallographic, NMR, and computational
studies support the presence of anion-p contacts and their critical role in these systems.
Another topic of which we pioneered the study is the electron-deficient ligand HAT(CN)6 (1,4,5,8,9,12hexaazatriphenylene-hexacarbonitrile) in the presence of halides. The charge transfer contacts in these systems lead to
highly colored solutions/crystals, with {[HAT(CN) 6]2[X]3}3- entities exhibiting high association constants, thus rendering
them promising anion-sensing receptors.4 These self-assembled systems, wherein anion-π contacts are the driving
elements, pave the way for understandi ng their importance and nature in solution and in the solid state and lends insight
into the purposeful elaboration of larger supramolecular frameworks with interesting physical and chemical properties.
1. Helen T. Chifotides, Kim R. Dunbar. Acc. Chem. Res. 2013, 46, 894.
2. Brandi L. Schottel, Helen T. Chifotides, Kim R. Dunbar, Chem. Soc. Rev. 2008, 37,
68.
3. Helen T. Chifotides, Ian D. Giles Kim R. Dunbar. J. Am. Chem. Soc. 2013, 135, 3039. Helen T. Chifotides, Brandi L.
Schottel, Kim R. Dunbar, Angew. Chem. Int. Ed. 2010, 49, 7202.
INOR 228
Heteroleptic polypyridyl ligand cobalt(III) complexes
Sean E. Hightower, [email protected], Blaise A. Frenzel, Cole T.
Kuester. Chemistry/9024, University of North Dakota, Grand Forks, North Dakota, United States
The development of catalyst capable of performing redox transformation is a critical and fundamental process to
renewable fuels and chemicals. The majority of these catalyst are prepared from noble metals, which may significantly
increase the cost of fabrication of fuel and chemical devices. Catalysts composed from more abundant metals need to be
explored. To this end, catalyst made of cobalt have received increased attention due their advantages of low cost and
good activity. We will describe new heteroleptic [Co(mer-triamine)(diimine)Cl]2+ complexes in which the triamine is
2,2′:6′,2″-terpyridine (tpy) or 2,6-bis(8′-quinolinyl)pyridine (bqp) and the diimine is either 2,2′-bipyridine (bpy) or 1,10phenanthroline (phen). The preparation, structural characterization, electrochemistry and electronic structure will be
presented.
INOR 229
Transition metal complexes as paraSHIFT and paraCEST MRI contrast agents Pavel B. Tsitovich,
[email protected], Jordan M. Cox , Jason B. Benedict, Janet R.
Morrow. Department of Chemistry, SUNY at Buffalo, Amherst, New York, United States
Paramagnetic transition metal complexes that significantly shift proton resonances of ligands are utilized as molecular
imaging probes. ParaSHIFT (paramagnetic chemical shift imaging) and paraCEST (paramagnetic Chemical Exchange
Saturation Transfer) MRI contrast agents will be presented. Fe(II) and Co(II) complexes of TACN (1,4,7triazacyclononane) with three 6-methyl-2-picolyl pendents ([M(MPT)]2+, M2+= Fe2+, Co2+) are structurally similar, stabilized
in a single diastereomeric form, and have hyperfine (60-800 Hz linewidths) shifted proton resonances (–20 to +200 ppm)
in water. The structures of Fe(II) and Co(II) complexes based on CYCLEN (1,4,7,10tetraazacyclododecane) with four 6methyl-2-picolyl pendents are six-coordinate in aqueous solution, as well as in the crystalline state with only two transpendents coordinated to the metal center (Fig. 1A). Two methyl groups of the C2-symmetrical [Co(TMPC)]2+ complex are
shifted at -125 ppm from water and demonstrate the greatest temperature dependence with a temperature coefficient of
0.52 ppm/oC. Another CYCLEN-based Co(II) complex, [Co(BMPC)]2+, containing two 6-methyl-2-picolyl transpendents is
six-coordinate and has less shifted proton resonances compared to [Co(TMPC)] 2+ (Fig. 1B). The temperature-dependent
hyperfine-shifted 1H-NMR resonances make these complexes promising for in vivo paraSHIFT temperature sensing.
CYCLEN-based complexes of Fe(II) containing 2-amino-6-picolyl pendents demonstrate highly shifted NH proton
resonances suitable for paraCEST MRI. The metal ions are stabilized in +2 oxidation state and complexes are kinetically
inert over a wide range of pH values (5.0-8.5), as well as in the presence of biologically relevant cations and anions.
Figure 1.
INOR 230
Carbonato-bridged copper(II) complexes formed via fixation of atmospheric CO 2
Febee Louka1, [email protected], Franz A. Mautner3, Salah S. Massoud2. (1)
Chemistry Dept, University of Louisiana-Lafayette, Lafayette, Louisiana, United States
(2) Chemistry Dept, Univ of Louisiana at Lafayette, Lafayette, Louisiana, United States
(3) Institut für Physikalische and Theoretische Chemie, Technische Universität Graz , Graz , A-8010 Graz, Austria
In slightly basic solutions, the fixation of atmospheric CO 2 by metal complexes, through hydroxo-species to afford the
carbonato metal complexes is an interesting topic from the structural and magnetic point of views, bioinorganic and
environmental fields as well as catalytic studies. Two new bridged carbonato complexes: [Cu 3(L)3(µ3CO3)(ClO4)3]ClO4 (1) and [Cu2(istren)2(µ2-CO3)](ClO4)2·H2O (2) were isolated in slightly basic methanolic solution via
atmospheric CO2 fixation , where L = (3,5dimethyl-4-methoxy-2-pyridylmethyl)-((2-pyridyl)-2-ethyl)-methylamine and istren
= tris(2-isopropylethyl)amine (Chart 1). The two complexes were structurally characterized by spectroscopic techniques
and by single crystal X-ray crystallography. In these complexes, the bridged-carbonato ligands exhibit different
coordination bonding modes. The magnetic susceptibility of the complexes at variable temperature will be discussed in
relation to their structural parameters.
Chart 1. Structure formulas of the amine ligands
INOR 231
Synthesis and structural characterization of PTA derivative modified transition metals
Jeremiah M. Sears1,4, [email protected], Timothy J. Boyle2, Brian J. Frost3, WeiChih Lee3, Michael L. Neville1. (1)
Advanced Material Laboratory, Sandia National
Laboratories, Albuquerque, New Mexico, United States (2) Advanced Materials
Laboratory, Sandia National Laboratories, Albuquerque, New Mexico, United States (3)
Department of Chemistry/0216, University of Nevada, Reno, Nevada, United States (4) Chemistry, University of Nevada,
Reno, Reno, Nevada, United States
Previously unreported 1,3,5-triaza-7-phosphaadamantane (PTA) derivatives and the corresponding phosphine oxides
were synthesized and characterized. Some of these derivatives exhibited moderate to slight water solubility. Transition
metal complexes bearing these derivatives and other previously reported PTA derivatives were characterized. Complexes
were pursued for aqueous nitrile hydration or for material applications. Some of the ruthenium arene complexes and in
situ generated catalysts incorporating PTA derivatives were identified as catalytically active toward benzonitrile hydration.
Isolated air stable, water-soluble ruthenium arene complexes were further investigated for a variety of nitriles featuring
methoxy, nitro, pyridyl, benzyl, and alkyl functional groups. Material application work is ongoing.
INOR 232
Investigation of isomeric single amino acid chelate (SAAc) rhenium series
Nicholas J. Azzarelli1, [email protected], Michael P. Coogan3, James A. Platts4,
Robert P. Doyle2, Jon A. Zubieta1. (1) Syracuse University, Syracuse, New York, United States (3) Lancaster University,
Lancaster, United Kingdom (4) Cardiff University, Cardiff, United Kingdom
Luminescent metal complexes are an exceptional tool in the field of cellular imaging due in part to their long lifetimes, high
luminescence efficiency, large Stokes shifts, and a tunable excitation and emission wavelength. Compounds containing a
rhenium tricarbonyl core {Re(I)(CO)<sub abp="570">3}<sup abp="571">+ are of particular interest due to their high
stability and photophysical properties. Using N<sup abp="572">1,N<sup abp="573">1-bis(thiazol-4-ylmethyl)butane-1,4diamine as a tridentate ligand, a {Re(I)(CO)<sub abp="574">3}<sup abp="575">+core complex (<b abp="576">1) was
noted to exhibit the highly unusual behavior of emission wavelength varying with excitation wavelength. This phenomena
has been attributed to photoisomerization from the N,N ground state to the N,S and S,S excited state. Work herein
focuses on the synthesis, purification, characterization and photophysical properties of ground state isomeric analogues of
<b abp="577">1 to determine the effects of the coordination of N,S and S,S in the ground state on emission behavior.
Complementary DFT calculations on target complexes have shown that isomeric coordination to the {Re(I)(CO)<sub
abp="578">3}<sup abp="579">+ core impacts geometry, electronic structure, and shows favorable N,N coordination as
opposed to
N,S and S,S. Exploitation of this photo-isomerized series of complexes can lead to the production of photo devices.
INOR 233
Electronic structure and reactivity of d0 Mo and Ti complexes of a trisaminophenolate ligand
Travis Marshall-Roth, [email protected], Seth N. Brown. Department of Chemistry and Biochemistry, University of
Notre Dame, Notre Dame, Indiana, United States
Nonclassical redox reactions involve bond formation at a metal center facilitated by oxidation of the surrounding ligands.
In order to discourage ligand dissociation upon oxidation, a novel tripodal tris(aminophenol) ligand, tris(4-methyl-2-((3',5'di-tert-butyl-2'hydroxyphenyl)amino)phenyl)amine, MeClampH6, was prepared. Its diamagnetic molybdenum(VI) complex
features a capped octahedral geometry with significant π donation from the three redox-active amidophenolate orbitals.
Each amidophenolate displays a calculated metrical oxidation state of about -1.5 and a π bond order of 2/3. Analysis of
the optical bands representing the a (πnb) → e (dπ*) and e (πb) → e (dπ*) transitions in neutral (MeClamp)Mo gives an
estimate of 40 kcal/mol stabilization per π bond. The titanium(IV) analogue (MeClamp)Ti (shown below) is a diamagnetic,
unsymmetrical κ6 complex with a doubly oxidized ligand and weaker π bonding. Evidence of catalytic oxidation of benzylic
and aliphatic alcohols to aldehydes under aerobic conditions by (MeClamp)Ti will be presented.
INOR 234
Syntheses and characterizations of luminescent rare earth metals complexes
Pong K. Yuen1,3, [email protected], Cheng Man D. Lau2,3. (1) Universiry of
Macau, Macau, Macao (2) Macau University of Science and Technology, Macau,
Macao (3) Macau Chemical Society, Macau, Macao
The research of luminescent lanthanide complexes has been steadily growing mainly because of their unique spectral,
optical, electrical and magnetic properties.
Luminescent rare earth metals complexes are applied in fields ranging from materials sciences to biomedical sciences.
We have synthesized a series of homoleptic rare earth metals complexes containing the Salen-type Schiff-base ligands.
Here we report the syntheses and the characterizations of the mononuclear terbium complexes containing Salen-type
ligand with strong visible and luminescent characteristics.
INOR 235
Designing artificial monoamine transporters based on synthetic supercontainers
Uma Sambasivam2, [email protected], Zhenqiang Wang1, [email protected]. (1) Chemistry, University of
South Dakota, Vermillion, South Dakota, United States (2) Chemistry, University of SouthDakota, Vermillion, South
Dakota, United States
Monoamine transporters (MATs), proteins that regulate monoamine neurotransmitters, play an important role in neuronal
signaling. The ability to mimic the MATs in synthetic systems can lead to biomedical applications including controlled drug
delivery. We have developed a new family of synthetic containers, namely metal-organic supercontainers (MOSCs)
through the self-assembly of metal ions, sulfonylcalix[4]arene precursors and carboxylate linkers. In biological systems,
monoamine neurotransmitters interact with MATs through cation-π and H-bonding interactions. We envision that MOSCs
can provide unique opportunities to mimic MATs, thanks to their suitable structural features including multiple aromatic
moieties and novel dual-pore architecture. Binding of relevant monoamines (e.g., adamantanamine and acetyl choline)
with MOSCs has been probed using supramolecular titrations and co-crystallization techniques. Preliminary results show
that MOSCs can indeed preferentially bind with monoamine guests over non-amine analogous.
INOR 236
Interactions of coordination complexes with reverse micellar interfaces: The effects on MLCT bands and
coordinated ligand pKa values
Abram A. Cadena1, [email protected], Michael D. Johnson1, [email protected],
Jarukorn Sripradite2, Susannah A. Miller3, Debbie C. Crans4. (1) Department of
Chemistry & Biochemistry, New Mexico State Univ, Las Cruces, New Mexico, United
States (2) Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States (4) Department of
Chemistry, Colorado State, Fort Collins, Colorado, United States
Probing the interactions of coordination complexes with interfaces is important for understanding how metal based drugs
are taken up into cells and are subsequently affected in catalytic processes. Encapsulation of a series of metal complexes
within reverse micelles (RMs) formed with positively and negatively charged surfactants has been carried out. We have
used changes in the positions of the MLCT bands of pentammineruthenium(II) and pentacyanoferrate(II) complexes
possessing Nheterocyclic ligands as a probe to determine the extent of ligand penetration into the RM interfaces. Our UVvis spectroscopic results are supported by 1H-NMR spectroscopy. We have also used UV-vis spectroscopy to
spectrophotometrically determine the pKas of the protonatable N-heterocyclic ligands on the ruthenium(II) complexes. The
influence of RM sizes and interfacial charges along with ligand hydrophobicity and structure are reported. This work
shows that the observed pKa values decrease significantly (up to 4pKa units) by encapsulation as RM size decreases.
INOR 237
Study of glutathione interactions with anticancer Gold(III) diammines complexes using NMR, UV-VIS and
electrochemistry
Anvarhusein Isab, [email protected]. Chemistry, King Fahd Univ of Pet & Minerals, Dhahran, Saudi Arabia
The interaction of gold(III) diammines complexes [Au(en)Cl2]Cl, [Au(en)2]Cl3, and [Au(DACH)Cl2]Cl with Glutathione have
been studied spectroscopically and electrochemically in aqueous solution. The shifts in NMR resonance shows oxidation
of Glutathione to Glutathione disulfide (GSSG) and resonance for free diammine ligand obtained at reaction ratio (1:2)
gold(III) complex to GSH implying reduction of gold(III) to elemental gold(0). UV-VIS Kinetic scan shows formation of
intermediate with formula [Au(diammine)(SG)2]+ which is not observed in NMR the Kinetics of this substitution step was
also investigated using UV-VIS technique at three different temperatures, pseudo-first order rate constant and activation
parameters (∆Hǂ and ∆Sǂ) for intermediate formation were determined. ComplexaK M-1. min-1∆Hǂ kJ. mol-1∆Sǂ JK-1mol-1
[Au(DACH)Cl2]Cl16.5 + 0.2937.3 + 0.75-85.5 + 2.70
[Au(en)Cl2]Cl102 + 0.7118.3 + 0.94-136 + 2.92
[Au(en) 2]Cl350.5 + 3.0010.7 + 1.64-168 + 5.21
All values expressed as (Average + SDEV)
Acknowledgement
This research was supported by the KFUPM Research Committee under DSR project # IN121049.
INOR 238
Photocatalytic NADH regeneration and hydrogen production using Rh complexes and Pt nanoparticles
Jinheung Kim, [email protected], Soojin Kim. Chemistry & Nano Science, Ewha
Womans University, Seoul, Korea (the Republic of)
Photochemical hydrogen production is carried out using platinum nanoparticles (PtNPs) and visible light energy with
chemically generating rhodium-hydride species from molecular Rh complexes and sodium formate. Rh-hydrides not only
reduce NAD+ to generate NADH, but also react with protons by photoactivation in the presence of PtNPs to produce H 2.
PtNPs alone reduced NAD+ without another photosensitizer upon visible light irradiation. The chemically generated NADH
is sequentially photoactivated by PtNPs and eosin Y to produce hydrogen. These two different hydrogen production
pathways show different rate-limiting steps based on kinetic studies using Rh catalysts containing electron-donating and
electron-withdrawing groups.
INOR 239
Mechanistic studies of oxidative aliphatic carbon-carbon bond cleavage in Cu(II) chlorodiketonate complexes
Sushma L. Saraf, [email protected], Jay R. Argue, Lisa M. Berreau. Utah State University, Logan, Utah, United
States
One of the most important challenges for chemists in the 21st century is the development of ways to convert chemical
feed stock into useful products such as pharmaceuticals, polymers, and fuels in an environmentally benign and costefficient manner. Selective oxidative carbon-carbon bond cleavage is an area of relevance to this goal, in particular
reactions catalyzed by earth-abundant metals in which O2 is used as the terminal oxidant. Previous studies in the Berreau
lab have shown that a mononuclear copper(II) chlorodiketonate complex will undergo aliphatic carbon-carbon bond
cleavage within the diketonate unit upon exposure to O 2 at ambient temperature. Significantly, catalytic amounts of
chloride anion were found to accelerate the proposed oxygen activation step. In the results to be presented, we have
performed further mechanistic experiments to probe this system, including kinetic studies and evaluation of halide
analogs.
INOR 240
Coordination chemistry of cyanopyrazoles and cyanoscorpionates
David M. Eichhorn, [email protected]. Wichita State Univ, Wichita, Kansas,
United States
Our group has been investigating the synthesis and chemistry of pyrazoles with cyano substituents at the 4-position,
scorpionate (polypyrazolylborate) ligands derived from these pyrazoles, and metal complexes of both the pyrazoles and
scorpionates. These ligands incorporate the strongly electron-withdrawing cyano group and have the ability to mediate the
formation of polymeric species through coordination at both the pyrazole and cyano N atoms. Recent developments in this
chemistry will be presented.
INOR 241
Single and multiphoton turn-off fluorescent sensor for tin and iron
Rathnayaka M. Madawala1, [email protected], Ekkehard Sinn2. (1)
Western Michigan University, Kalamazoo, Michigan, United States (2) Department of Chemistry, Western Michigan
University, Kalamazoo, Michigan, United States
A new rhodamine based sensor A was synthesized and binding of A towards various metal ions (Ca2+, Mg2+, Na+, K+,
Fe2+, Fe3+, Ni2+, Cu2+, Co2+, Cr3+, Pb2+, Zn2+, Cd2+, Hg2+, Sn2+) at pH= 7 were examined through changes in fluorescence
and UV. A shows 172 times high absorption enhancement upon binding with Fe2+ and 140 times high absorption
enhancement upon binding with Fe3+. Upon binding with iron (Fe3+ and
Fe2+), A shows no fluorescent enhancement at all, but a very high fluorescent enhancement upon binding with Sn 2+.
Therefore sensor A is highly selective towards Sn2+ over other metal ions. High sensitivity and high association constant
values further confirm the strong affinity of A towards Sn2+. Two-photon excitation further enhanced the fluorescence of ASn2+ complex. A-Sn2+ complex shows a 165-fold fluorescent enhancement upon single-photon excitation and a 964-fold
fluorescent enhancement upon two-photon excitation. Fluorescence upconversion, quantum yield measurements, and
1HNMR titration were carried out to further understand the mechanism of Sn 2+ binding to sensor A.
INOR 242
Synthesis, NMR characterization, and MIC studies of a new series of alpha-(N)heterocyclic thiosemicarbazone
ligands and their Pd2+ and Cu2+ metal complexes
Jennifer D. Conner2, [email protected], Shawna D. Simpson 1,
Amanda L. Koch1, Edward C. Lisic1. (1) Dixie Ave, Tennessee Tech Univ Chemistry,
Cookeville, Tennessee, United States (2) Chemistry, Tennessee Technological University, Cookeville, Tennessee, United
States
Triapine®, which has recently made it to stage II clinical trials as an anticancer agent, and other similar alpha-(N)heterocyclic thiosemicarbazone ligands act as ribonucleotide reductase poisons. Copper complexes of these same
ligands also inhibit cell replication by an entirely different mechanism, attacking Topoisomerase IIα. The focus of this
research is on synthesis and characterization of three series of new alpha(N)-heterocyclic thiosemicarbazone ligands
based on thiazole-2-carboxaldehyde, 2acetylthiazole, and 2-acetyl-4-methylthiazole. To these three substrates, seven
different thiosemicarbazides were attached to form the thiosemicarbazones reported here. These 21 new
thiosemicarbazone ligands were then characterized by NMR, melting point, and MS. Once characterized and purified,
these mono-anionic tridentate ligands were then reacted with Cu2+ and Pd2+ to make the square planar metal complexes.
These were again characterized by UV/Vis, melting point, MS, and NMR, where applicable. All of the metal complexes
and ligands were tested with Minimum Inhibitory Concentration (MIC) studies using seven different microbes to test their
potency. As will be shown, many of the new compounds exhibit profound anti-microbial properties.
INOR 243
Borates in biomass conversion processes
David M. Schubert, Michelle K. McCray, [email protected]. R&D Dept.,
U.S. Borax Inc. / Rio Tinto, Greenwood Village, Colorado, United States
Interactions of borates with carbohydrates and other biological substrates play essential roles in the functioning of plants
and other living things. Consequently, borates are important commercial agricultural micronutrients. The chemistry
underlying the biological roles of boron are based on the dynamic formation of B-O-C ester linkages with alcohols, and
particularly 1,2-diols, that are abundantly present in biomass constituents. These same interactions may be exploited to
bring about or improve the selectivity of a range of transformations relevant to biomass utilization for the production of
biofuels, chemicals, and agricultural products. Borates form complexes with many natural products and catalyze or direct
isomerizations, dehydrations, and esterifications. Their presence can dramatically influence catalysis, pyrolysis and
fermentation processes. Borates also act as antioxidants in the protection of easily oxidized species such as phenolic
products resulting from lignan depolymerizations.
Examples of boric acid interactions with 1,2-diol and phenol functionalities abundantly present biomass constituents.
INOR 244
Late transition metal complexes for industrially relevant catalysis
Nicholas A. Swisher1, [email protected], Patricio Romero1, Robert H.
Grubbs2. (1) Caltech, Pasadena, California, United States (2) Cal Tech 164-30, Pasadena, California, United States
A variety of new metal complexes of tridentate pincer ligands are reported. An emphasis on combinations of strong donor
and mild acceptor substituents with unusual steric properties is shown. Applications of the pincer complexes to industrially
relevant catalytic reactions such as transfer hydrogenation of alkanes and alcohols are demonstrated. Additionally, an
alternative to the predominant industrial synthesis of ethylene glycol is shown in a one-pot, two-step procedure starting
from formaldehyde. N-heterocyclic carbene catalyzed condensation of formaldehyde to form a C2 compound,
glycolaldehyde, followed by homogeneous transition metal catalyzed transfer hydrogenation using methanol as reductant
gives ethylene glycol. Attempted optimization of both steps is described.
INOR 245
Cobalt-induced B-H and C-H Activation Leading to Facile B-C Coupling of Carboranedithiolate and
Cyclopentadienyl
Hong Yan, [email protected]. Nanjing University, Nanjing, China
We report the one-pot reactions of the 16e half-sandwich complex CpCoS2C2B10H10
(1), methyl propiolate and 3e-donor ligands which have led to selective Bfunctionalization at carborane with
cyclopentadienyl as a functional group at ambient temperature in good yields. Metal-promoted activations of both B–H
bond at carborane and C–H bond at Cp unit have taken place sequentially in the cooperation of organic ligands. The
reaction requires a 3e-donor ligand and an activated alkyne, therefore suitable for a broad range of substrates. This
investigation provides a simple and efficient synthetic route to B-functionalized carborane derivatives.
INOR 246
Polynuclear iridium-bismuth carbonyl clusters: Synthesis, chemistry, and applications
Gaya Elpitiya4, [email protected], Richard D. Adams4, Mingwei Chen3, Qiang
Zhang1, Robert Raja2. (1) Chemistry, Texas AM University, College Station, Texas,
United States (2) Chemistry, University of Southampton, Southampton, United Kingdom
(3) University of Georgia, Athens, Georgia, United States (4) chemistry and
Biochemistry, University of Southcarolina, Columbia, South Carolina, United States
A series of new IrBi carbonyl clusters (Ir3(CO)6(GePh3)3(µ3-Bi)(µ3-H)3 (1) ,
Ir3(CO)6(GePh2)3(µ3-Bi) (2), (Ir3(CO)6(SnPh3)3(µ3-Bi)(µ3-H)3 (3) , Ir3(CO)6(SnPh2)3(µ3Bi) (4) have being synthesized by
adding Ge and Sn ligands on to Ir3(CO)9(µ3-Bi) (5)
.Compound 1 and 3 exist as isomers in solution. The isomers rapidly interconvert on
NMR time scale by tripodal, trigonal- twist rearrangement mechanisms. The MOs and UV-visible spectra of 2 were
calculated and analyzed by ADF DFT computational treatments. Another interesting high nuclear IrBi cluster has being
synthesized (Ir5(µ3Bi2)(µ4-Bi)(CO)10) (6) by the reaction of Ir3(CO)9(µ3-Bi) with Ph3Bi in a hexane reflux. Both (Ir5(µ3-Bi2)(µ4Bi)(CO)10) and Ir3(CO)9(µ3-Bi) were used to make the first Ir-Bi bimetallic nano particles . These bimetallic nano particles
have being tested as catalyst precursors for the direct oxidation of 3-picoline to nicotinonitrile under mild conditions by
using acetyl peroxy borate (APB) as the source of oxygen and have shown promising results.
HOMO of Ir3(CO)6(GePh2)3(µ3-Bi)
LUMO of Ir3(CO)6(GePh2)3(µ3-Bi)
INOR 247
Alkene vs. alkyne hydroarylation catalyzed by electrophilic palladium(II) and platinum(II) complexes
Mostafa Manjahi, [email protected], Christine Hahn. Chemistry, Texas AM University Kingsville, Kingsville,
Texas, United States
The dicationic ethylene complexes [M(PNP)(C2H4)]X2 (M = Pd, Pt; X = BF4, SbF6, PNP = 2,6bis(diphenylphosphinomethyl)pyridine) can catalyze the hydroarylation of both ethylene and acetylene. In order to direct
the reaction path in a certain direction, the temperature is a critical parameter. The equilibrium system of alkene-alkyne
substitution, and arene addition across the double bond versus the across the triple bond have been studied at different
temperatures. It was found that at lower temperature the double bond arylation can be substantially retarded, while the
arene still adds at the triple bond at a relatively high rate. Various parameters such as nucleophilicity of the arene and the
presence of acid co-catalyst play an important for the chemoselectivity.
INOR 248
Theoretical studies of hydroformylation of butadiene
Camina H. Mendis1,2, [email protected], Tapan Maji1,2, Jon A. Tunge1,2, Ward H. Thompson1,2. (1) Dept of
Chemistry, Univ of Kansas, Lawrence, Kansas, United
States (2) Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas, United States
Rhodium-catalyzed hydroformylation of butadiene has attracted industrial interest as an atom-economical green route to
produce adipaldehyde, which is the starting material for Nylon-6,6 monomers, adipic acid, and hexamethylenediamine.
According to the proposed reaction pathway, rhodium catalyzes the hydroformylation of butadiene via a two-step reaction.
The regioselectivity of olefins are influenced by the steric and electronic properties of biphosphine/biphosphite ligands on
the rhodium catalyst. A detailed electronic structure study on the catalytic cycle of different
biphosphine/biphosphite ligands will be presented to understand the kinetics and the mechanism of the two-step
hydroformylation of butadiene. Results will help develop design principles for selective rhodium hydroformylation.
INOR 249
Control of cis-selectivity and tacticity in ring opening metathesis polymerization using ruthenium metathesis
catalysts
Lauren E. Rosebrugh, [email protected], Vanessa M. Marx, Tonia S. Ahmed,
John Hartung, Robert H. Grubbs. Chemistry and Chemical Engineering, California
Institute of Technology, Los Angeles, California, United States
A series of ruthenium metathesis catalysts containing a cyclometalated N-heterocyclic carbene (NHC) ligand were
examined in the ring opening metathesis polymerization (ROMP) of norbornene- and norbornadiene-derived monomers.
In general, the resulting polymers were found to be highly cis with syndiotactic-biased cis and trans regions, while
blockiness calculations showed that trans double bonds occurred randomly throughout the polymers. These structural
trends suggest that the controlling factor in cis selectivity and tacticity is the combined influence of the stereogenic
ruthenium center and the steric environment surrounding the alkylidene on monomer approach. These conclusions are
further supported by preliminary computational studies, which are ongoing and will also be discussed. It is expected that
these results will provide invaluable insight into the mechanism and mode-of-action of cyclometalated ruthenium
metathesis catalysts and will be instrumental in the design of future catalysts for cisselective metathesis transformations.
INOR 250
Enantioselectivity and substitution effects in rhodium catalyzed intramolecular hydroacylation
Brian P. Schumacher1, [email protected], Levi M. Stanley2, Joseph
Scanlon1. (1) Chemistry, Ripon College, Ripon, Wisconsin, United States (2) Chemistry, Iowa State University, Ames,
Iowa, United States
Hydroacylation is a useful synthetic method, allowing an aldehyde and alkene to form a ketone. Experimental research
has shown that rhodium(I)-BINAP complex catalyzed hydroacylation of vinyl benzaldehyde follows strict enantioselectivity
and substitution effects. Through use of M05-2X density functional, the cause of the substitution effects was determined
by analyzing the mechanism of the reaction in three scenarios: unsubstituted alkene, internal methyl substitution for R 1,
and terminal methyl substitution for R2. By constructing potential energy surfaces, these three scenarios were compared
to determine that the barrier for C-C bond formation for the internal substitution is favored over the terminal substitution by
a difference of 7.9 kcal/mol. Both enantiomeric pathways were also analyzed to determine the cause of enantioselectivity.
Figure 1. The general mechanism of rhodium catalyzed intramolecular hydroacylation.
INOR 251
Electrocatalytic reduction of CO2 to formate using iridium pincer complexes
Peng Kang2, [email protected], Sheng Zhang2, Zuofeng Chen2, Cheng Chen2,
Thomas J. Meyer1, Maurice Brookhart2. (1) University of North Carolina, Chapel Hill,
North Carolina, United States (2) Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States
The reduction of CO2 to high-energy, value-added chemical intermediates such as formic acid/formate is a key step in
utilizing CO2 for renewable production of fuels and chemicals. To accomplish such transformations, iridium pincer
dihydride complexes have been developed to catalyze the electrocatalytic two-electron reduction of CO2 to formate.
Ir PCP-type pincer complexes are able to reduce CO2 to formate electrocatalytically both in non-aqueous media and in
water with high efficiency and selectivity. Formate is the only reduced carbon product, produced in 93% Faradaic yield
with a small amount of H2 but no formation of CO. The high selectivity for formate production over H 2 originates from the
aqueous stability of Ir dihydride species, the active species for reduction of CO2. As a further pursuit of reducing CO2 with
high efficiency, an iridium pincer dihydride catalyst was immobilized on carbon nanotube-functionalized gas diffusion
electrodes by using a non-covalent binding strategy. High turnover numbers (~200,000) and turnover frequencies (~15 s –
1) were observed in aqueous solutions saturated in CO with added HCO – which is enabled by the novel electrode
2
3
architecture.
The developed Ir pincer complexes can be used as viable tools for photoelectrochemical CO2 reduction using solar
energy, and integration of these catalysts into Dye Sensitized Photoelectrosynthesis Cells (DSPEC) in conjunction with
molecular chromophores is currently underway.
INOR 252
Oxygen atom transfer to iridium(Cp*) complexes
Christopher Turlington1, [email protected], Maurice Brookhart2, Joseph L.
Templeton3. (1) Chemistry, UNC Chapel Hill, Chapel Hill, North Carolina, United States
(2) Univ of North Carolina, Chapel Hill, North Carolina, United States (3) UNC Chapel Hill, Chapel Hill, North Carolina,
United States
Results of oxygen atom transfers to iridium(Cp*) complexes with bidentate ligands will be presented. Oxidations are
conducted at low temperatures, and the reaction products characterized by NMR spectroscopy. Oxygen atom transfer
using a soluble iodosylbenzene derivative to an Ir(Cp*)(phenylpyridine) cation bearing an electrondeficient bis(trifluoromethyl)benzonitrile ligand was studied. Oxygen atom transfer to the central carbon of the coordinated nitrile was
observed, coupled with insertion into the iridium-carbon bond of coordinated phenylpyridine, forming a coordinated
organic amide. A second oxygen atom transfer follows if no trapping ligands are present, which generates an unstable
species that oxidizes phosphines. Oxidation reactions of complexes with bidentate ligands that prevent insertion
reactions, such as bipyridine, will be compared to oxidation of phenylpyridine complexes. The possibility of high valent
intermediates in oxidation reactions will be discussed.
INOR 253
Synthesis of branched ultrahigh-molecular-weight polyethylene using highly active neutral, single-component
Ni(II) catalysts
Zhou Chen3, [email protected], Milad Mesgar1, Peter S. White3, Olafs Daugulis1, Maurice Brookhart2. (1) U of
Houston, Houston, Texas, United States (2) Univ of North
Carolina, Chapel Hill, North Carolina, United States (3) Chemistry, University of North
Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Neutral nickel methyl complexes incorporating 2,8-diarylnaphthyl groups have been synthesized and characterized.
Salicylaldiminato nickel systems 1a,b are exceptionally active nickel single component catalysts for the polymerization of
ethylene capable of producing lightly branched ultra-high-molecular-weight polyethylene (UHMWPE). In addition, complex
1a shows a “quasi-living” polymerization behavior.
INOR 254
Living polymerization of ethylene and copolymerization of ethylene/methyl acrylate using “sandwich” diimine
palladium catalysts
Kate Allen3, [email protected], Jesus Campos Manzano3, Olafs Daugulis1, Maurice
Brookhart2. (1) U of Houston, Houston, Texas, United States (2) Univ of North Carolina, Chapel Hill, North Carolina,
United States (3) Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Cationic Pd(II) catalysts (1) incorporating bulky (8-p-tolylnaphthyl) substituted diimine ligands have been synthesized and
investigated for ethylene polymerization and ethylene/methyl acrylate copolymerization. Homopolymerization of ethylene
at room temperature resulted in branched polyethylene with narrow M w/Mn values (ca. 1.1), indicative of a living
polymerization. A mechanistic study revealed that the catalyst resting state was an alkyl olefin complex and that the
turnover-limiting step was migratory insertion, thus the turnover frequency is independent of ethylene concentration.
Copolymerization of ethylene and methy acrylate (MA) was also achieved. MA incorporation was found to increase
linearly with MA concentration. Isomerization of the product of MA insertion was monitored using low temperature NMR
studies.
INOR 255
Selective cross-dimerization of ethylene with substituted olefins
Philippa R. Payne, [email protected], Maurice Brookhart, Michel R. Gagne. UNC Chapel Hill, Chapel Hill,
North Carolina, United States
New synthetic approaches to the atom-economical conversion of low-cost feedstocks derived from shale gas, particularly
ethylene, to value-added chemicals are attractive to the agrochemical and fine chemical industries. Advances in the use
of dicationic, square planar d8 Ni(II), Pd(II), and Pt(II) complexes for the cross-dimerization of ethylene with substituted
olefins will be presented. Tightly bound, sterically bulky, neutral pincer ligands impart high catalyst stability and selectivity
in these systems. The impact of the identity of the dicationic metal center as well as the steric and electronic properties of
the pincer ligand on reactivity and selectivity will be discussed.
INOR 256
Applications of PC(sp3)P iridium complexes in transfer dehydrogenation of alkanes and ethers
David Bezier1, [email protected], Maurice Brookhart2. (1) CHEMISTRY, UNIVERSITY OF NORTH CAROLINA AT
CHAPEL HILL, Chapel Hill, North Carolina,
United States (2) Univ of North Carolina, Chapel Hill, North Carolina, United States
The dehydrogenation of alkanes transforms inexpensive hydrocarbon feedstocks into olefins, which are valuable reaction
intermediates in the synthesis of fine chemicals and fuels. In industry, catalytic alkane dehydrogenation is carried out on a
large scale at high temperatures and with low product selectivities. Homogeneous systems have also been developed and
best results have been obtained with the use of bis(phosphine) IrPCP and bis(phosphinite) Ir-POCOP pincer complexes.1
In order to develop highly active and stable catalysts at high temperatures (225 °C and above), we synthesized iridium
complexes based on PC(sp3)P pincer-type triptycene ligands.2 The complex 1, which bears isopropyl groups, has
demonstrated high stability and activity when used as a catalyst in the disproportionation of 1-hexene at 180 °C and in the
transfer dehydrogenation of linear and cyclic alkanes with tertbutylethylene as a hydrogen acceptor at 200 °C (Figure 1). 3
A similar complex bearing a CH2NMe2 group, 2, allowed support of the catalyst on γ-alumina for operation in a
heterogeneous mode. In addition, the catalyst 1 has shown to be very effective in the dehydrogenation of linear and cyclic
ethers.
1 Choi, J.; MacArthur, A. H. R.; Brookhart, M.; Goldman, A. S. Chem. Rev. 2011, 111, 1761-1779.
2 Musa, S.; Romm, R.; Azerraf, C.; Kozuch, S.; Gelman, D. Dalton Trans. 2011, 40, 8760-8763.
3 Bézier, D.; Brookhart, M. ACS Catalysis 2014, 4, 3411-3420.
Figure 1
INOR 257
Regioselective palladium-catalyzed hydrodebromination of 2,3,5tribromothiophene
Kristine L. Konkol, [email protected], Seth C. Rasmussen. Department of
Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota, United States
Functionalized thiophenes are widely used as building blocks in the synthesis of materials, natural products, and
pharmaceuticals. Halothiophenes, especially bromothiophenes, are useful and the most common synthetic precursors for
the production of functionalized thiophene species. The synthesis of these precursors can become more complex when
attempting to halogenate the less readily accessible βpositions, which requires either blocking of the α-positions or αbromination prior to βbromination. In such cases of polybromination, the undesired, but necessary αbromides must then
be removed. This process becomes even more complex in the
production of asymmetric bromothiophenes containing both α- and β-bromines. While replicating previously reported
catalytic conditions for the regioselective debromination of 2,3,5-tribromothiophene, the observed results were found to be
inconsistent with what was reported in the literature and a detailed study of this catalytic process will be presented. Under
non-catalytic conditions, 2,3,5-tribromothiophene reacts with NaBH4 to debrominate exclusively at the more electronically
favored 2-position, forming 2,4dibromothiophene. However, this reaction can be controlled with the addition of an
appropriate Pd-catalyst to selectively debrominate at the less reactive 5-position, forming 2,3-dibromothiophene. The
effects and interplay of electronics and sterics will be discussed, along with other experimental conditions that dictate both
selectivity and reactivity.
INOR 258
Ligand modification at a remote site to regulate iron-catalyzed olefin hydroboration
Kuei-Nin T. Tseng, [email protected], Jeff Kampf, Nathaniel K.
Szymczak. Chemistry, University of Michigan, Ann Arbor, Michigan, United States
The electronic properties of iron complexes are modulated by methylation of a remote site on the bMepi-ligand (bMepi =
1,3-bis(6’-methyl-2’-pyridylimino)isoindolate) backbone without rearrangement of the primary coordination environment.
This electronic difference at the iron center was used to regulate the activity and regioselectivity in catalytic hydroboration
of olefins.
INOR 259
Catalytic carbonylation of icosahedral dodecaborates
Kendall R. Kamp1, [email protected], Richard J. Staples2, Joel A. Dopke1. (1) Alma College, Alma, Michigan, United
States (2) MSU, East Lansing, Michigan, United States
The high-yield synthesis of functionalized dodecaborates has become of recent interest due to their application in fields
such as pollution remediation, cancer therapies, and clean energy production. To that end, we investigated the palladiumcatalyzed carbonylation of the iodododecaborate B12H11I2- under microwave conditions. The addition of CO to B12H11I2- to
produce B12H11CO- was achieved in high yield using a variety of commercially-available palladium catalysts, with best
results achieved by using Mo(CO)6 as a CO source. Reactions utilizing amines as in situ trapping agents provided
B12H11CO(NR2)-. Products were characterized by 11B, 1H and 13C NMR, ESIMS, and x-ray crystallography.
INOR 260
Copper-catalyzed addition of phenols to icosahedral dodecaborates
Chad Barnhart1, [email protected], Richard J. Staples2, Alejandro J. Ramirez3,
Joel A. Dopke1. (1) Alma College, Alma, Michigan, United States (2) MSU, East
Lansing, Michigan, United States (3) Baylor University, Waco, Texas, United States
The dodecaborate anion, B12H122-, and its derivatives have been of recent interest due to their high stabilities and low
toxicities. These properties allow the clusters to have potential use in a broad range of applications. As a result, the rapid,
high-yield synthesis of functionalized clusters could dramatically increase their availability for these emerging areas. The
iodododecaborate B12H11I2- readily reacts with a number of substituted phenols in the presence of a copper catalyst to
produce the substituted clusters, B12H11(OAr)2-, in high yield. The reactions of interest were conducted utilizing microwave
heating. Products were identified by 11B, 13C and 1H NMR and IR spectroscopies, ESI-MS, and x-ray diffraction.
INOR 261
Ruthenium-catalyzed substitutions of icosahedral dodecaborates
Luke R. Bent1, [email protected], Alejandro J. Ramirez2, Joel A. Dopke1. (1) Alma College, Alma, Michigan, United
States (2) Baylor University, Waco, Texas, United
States
The icosahedral cluster B12H122- and its derivatives have seen potential use in applications as varied as pollution
remediation and cancer therapies. Their high stabilities, electronic properties and low toxicities make them ideal
substrates for these fields. Our interest in the high-yield production of substituted dodecaborates has led us to investigate
the ruthenium-catalyzed substitution of B12H122- utilizing microwave heating. The reaction of B12H122- with CH2Cl2 or
C2H4Cl2 provided the substituted clusters B12H11Cl2- and B12H9Cl32-, respectively, in nearly quantitative yield. Additionally,
reactions utilizing o-C6H4Cl2 gave the clusters B12H11(Ar)2- and
B12H9(Ar)32- after purification by column chromatography. Products were characterized by 11B, 1H and 13C NMR, and ESIMS. Implications regarding the regiochemistry of the substitutions will be discussed.
INOR 262
Electrocatalytic oxidation of methylrhenium trioxide to methanol by an electrodeimmobilized ruthenium(II)
polypyridyl catalyst
Michael K. Coggins1, [email protected], Thomas J. Meyer2, Roy A. Periana3. (1)
Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina,
United States (2) University of North Carolina, Chapel Hill, North Carolina, United States
(3) Chemistry, The Scripps Research Institute, Jupiter, Florida, United States
The oxidative functionalization of metal-carbon bonds is a fundamental transformation with significance to the production
of new fuels. The single-site ruthenium(II) complex [Ru(Mebimpy)(4,4'-((HO)2OPCH2)bpy)(OH2)]2+ immobilized on tindoped indium oxide nanoparticle thin film electrodes has been found to electrocatalytically oxidize methylrhenium trioxide
to methanol with high selectivity in acidic aqueous solution. The RuIV(OH)3+ form of the catalyst is directly responsible for
this transformation and proceeds by the direct insertion of hydroxide into the rhenium-carbon bond of the substrate
through an observable intermediate species. A detailed electrochemical kinetics study has been performed with results
that are consistent with a single-site pathway for methylrhenium trioxide oxidation.
INOR 263
Twists and turns: WGS "catalysts" of Fe, Ru, and Os
Alexandra Eschmann1, Eugenia Wulff-Fuentes1, Drew Cunningham1, Brittany
Schreiber1, Lucas Burgan1, Zachary Hecht1, Garrett Seichter1, Arnold L. Rheingold2,
Jason S. D'Acchioli1, jason.d'[email protected]. (1) UW-Stevens Point, Stevens Point, Wisconsin, United States (2)
Chemistry, UCSD, Carlsbad, California, United
States
The synthesis and characterization of a series of Group 8 organometallic complexes has been undertaken in order to
probe their involvement in the so-called water-gas-shift
(WGS) reaction. We have shown in prior work that [(η5-Ind)Ru(CO)3]+ is active in the WGS reaction. Our current
investigations into Os analogues of the aforementioned Ru complex have generated some unusual new organometallic
octahedral Os complexes. Our presentation will address the chemistry of these complexes, as well as current progress
towards generating a true WGS catalyst.
INOR 264
Selective hydrogenation of phenylacetylene over supported gold catalysts
Elisabeth Purdy, [email protected], Bert D. Chandler. Chemistry Department, Trinity
University, San Antonio, Texas, United States
Supported gold nanoparticle catalysts, while not highly active for hydrogenation reactions, can be highly selective for
partial hydrogenations. The underlying support can have an important electronic influence on both catalytic activity and
selectivity; however, these effects are often difficult to quantify. Using the selective hydrogenation of phenylacetylene to
styrene as a probe reaction, we developed Hammett methodologies to help evaluate and understand how various metal
oxide supports affect the electronic properties of Au catalysts. Although alkyne hydrogenations are typically carried out
under high H2 pressures, we developed reaction parameters at atmospheric pressure in order to facilitate rapid and
convenient collection of kinetic data. We performed a full kinetic study to identify optimum reaction conditions and to
evaluate its utility as a test reaction. Michaelis-Menten interpretations of the kinetic data and interpretations of the
Hammett studies will also be reported.
INOR 265
Experimental and theoretical studies investigating the effect of solvent on 1JWH in Cp2WH2
Claudia I. Viquez Rojas, [email protected], T A. Mobley. Chemistry, Grinnell College, Grinnell, Iowa, United States
Recent work in our group has focused on the prediction of the one-bond indirect coupling (1JWH) between tungsten and
hydrogen in Cp2WH2 utilizing scalar and spinorbit relativistic DFT calculations. These studies indicate that minor changes
in the Cp2W structural core result in substantial changes in the W-H coupling constant. Moreover, previous NMR
experiments suggest that the isotropic coupling constant remains within one Hertz (~73.5) at room temperature despite
solvation changes in three different deuterated solvents: benzene, acetone and tetrahydrofuran. This implies that the
geometry of the molecule does not vary significantly as the solvent is changed. We realized that this would allow a subtle
test of the DFT calculations of 1JWH in these complexes. By carrying out identical computations in which the geometry of
the Cp2WH2 model is not altered but the solvent model is, we should expect to obtain similar coupling constants (even if
the absolute value of the coupling constants differ from those determined experimentally). Our interest in predicting the
structure of transition metal hydrides relates to the importance of understanding the nature and behavior of these
complexes, particularly in cases where obtaining neutron diffraction structures of them remain unfeasible. With this issue
in mind, we aim to compare the experimental and theoretical tungsten-hydrogen coupling constant in Cp2WH2 as it
represents a direct measure of the W-H interaction. This paper will describe our progress in these studies.
INOR 266
Low valent metal complexes of tris(diphenylphosphinomethyl)phenylborate
Alexander B. Weberg, [email protected], Trent D. Bohrmann, [email protected], Hanyue Xu, Paul J.
Fischer. Chemistry, Macalester College, Saint Paul, Minnesota, United States
Tris(diphenylphosphinomethyl)phenylborate (PhBPPh) is a facially-capping anionic ligand that creates appropriate
pseudotetrahedral metal (M = Fe, Co) environments for the stabilization of terminal imido complexes. Application of this
ligand in octahedral complexes is an emerging research area, with an emphasis to date on Ru(II) and Rh(III) chemistry.
This poster will discuss the syntheses of [Et4N][M(CO)3(PhBPPh)] (M = Cr, Mo, W), the first group VI metal complexes of
PhBPPh and rare zerovalent complexes of this ligand. Infrared spectroscopic studies suggest that PhBP Ph is a weaker
donor than hydrotris(1-pyrazolyl)borate (Tp) towards the zerovalent M(CO) 3 units in these anions. This ligand donor
ranking is apparently reversed towards [Mn(CO)3]+ fragments on the basis of the IR spectra of the zwitterionic,
monovalent manganese complex Mn(CO)3(PhBPPh). The boron-bound phenyl substituents of [Et4N][M(CO)3(PhBPPh)] and
Mn(CO)3(PhBPPh) are sufficiently electron-rich to bind group VI metal M(CO)3 fragments to afford bimetallics in which
tris(diphenylphosphinomethyl)phenylborate acts as a bridging ligand. The crystal structures of these bimetallics that detail
this new PhBPPh binding mode will be discussed.
INOR 267
Redox-active NHC pincer ligands for Ni-catalyzed aerobic dehydrogenative C–C cross coupling
Jerald E. Hertzog1, [email protected], Caleb F. Harris2, Jake D. Soper2. (1)
Department of Chemistry, Washington & Jefferson College, Washington, Pennsylvania,
United States (2) School of Chemistry and Biochemistry, Georgia Institute of
Technology, Atlanta, Georgia, United States
Sustainability and health concerns motivate efforts to replace Pd cross coupling catalysts with earth abundant and benign
later 3d transition metals. Previous work from our laboratory has demonstrated the capacity of redox-active aminophenolderived ligands to effect Co Negishi-type C–C cross coupling via Pd-like 2e– organometallic steps, including C–X oxidative
addition and C–C reductive elimination. This poster describes extensions to aerobic dehydrogenative C–C cross coupling.
A new Ni(II) complex containing a pincer redox-active bis(phenoxide) N-heterocyclic carbene ligand is shown to couple
benzoxazole and phenylacetylene in good yields (>60%) using LiOtBu as a base and O2 as an oxidant. Reactions that
define the scope and limitations of this Ni catalyst for related C–H bond activations/aerobic C–C cross couplings will be
reported.
INOR 268
Synthesis of palladium(II)-NHC compounds and their employment as crosscoupling catalysts
Dominick Colosimo, [email protected], Manuel Dominguez, [email protected], Gerard Rowe.
Chemistry and Physics, University of South Carolina Aiken, Aiken, South Carolina, United States
We have synthesized a series of palladium N-heterocyclic carbene (NHC) compounds that can successfully catalyze
cross-coupling reactions in aqueous solution. Classically, cross-coupling reactions are carried out in organic solvents,
using phosphine ligands, and in an inert atmosphere; our NHC palladium catalyzed cross-coupling reactions are carried
out in water without the need for an inert atmosphere. All of our reactions are performed utilizing a microwave reactor,
which allows us to reduce reaction times drastically. Our aim is to develop a highly efficient, air-stable, environmentally
benign catalytic system. These palladium catalysts perform well in water, which forms an important part of green
chemistry.
INOR 269
Sulfur-hydrogen bond activation by novel iridium diphosphine complexes
Haley N. Russ2, [email protected], Serge H. Schreiner1. (1) Chemistry,
Randolph Macon College, Ashland, Virginia, United States (2) Chemistry, RandolphMacon College, Ashland, Virginia,
United States
The activation of small molecules by transition metal complexes via ligand substitution or oxidative-addition has
historically received a great deal of attention since these reactions are requisite for catalytic processes.
Hydrodesulfurization (HDS) is an important process for the removal of sulfur from fossil fuels. Our work focused on the
synthesis and reactivity of iridium complexes stabilized by the aryldiphosphine, (C 6H5)2PCH2P(C6H5)2, and the alkyl
diphosphine, (C6H11)2PCH2P(C6H11)2. These complexes were reacted with sulfur-containing compounds to determine their
efficacy in the activation of sulfur-hydrogen bonds. The solution structures of resulting complexes complexes will be
described.
INOR 270
Synthesis of molybdenum carbon dioxide complexes via oxidation of a carbonyl ligand
Michael A. Pogash, [email protected], Gregory R. Lorzing, Joseph R. Vasta, Xuyao
Duan, Robert G. Carden, James J. Ohane, Peter M. Graham. Department of Chemistry,
St. Josephs University, Philadelphia, Pennsylvania, United States
The carbonyl compounds, TpRMo(NO)(L)(CO) where TpR = tris(pyrazolyl)borate (Tp) or tris(3,5-dimethylpyrazolyl)borate
(Tp*), and L = 1-methylimidazole (1-MeIm), 4dimethylaminopyridine (DMAP), PMe 3, pyridine, 3-chloropyridine, P(p-tolyl)3,
PPh3, or P(OMe)3 have been prepared from the dicarbonyl complex TpRMo(NO)(CO)2 by thermal displacement of CO. An
N-heterocyclic carbene complex has also been prepared where L = 1,3-dimethylimidazol-2-ylidene (NHC) using 1,3dimethylimidazolium-2-carboxylate. Oxidation of these TpRMo(NO)(L)(CO) complexes by cumene hydroperoxide, t-butyl
hydroperoxide, or O2 gives η2-carbon dioxide complexes, TpRMo(NO)(L)(η2-CO2), for L = 1-MeIm, DMAP, PMe3, NHC,
pyridine, or 3chloropyridine. These complexes have been characterized by X-ray crystallography, IR and NMR
spectroscopy. The η2-CO2 complexes are air stable and are thermally stable in solution at room temperature. Reduction of
TpRMo(NO)(L)(η2-CO2) back to TpRMo(NO)(L)(CO) can be accomplished using chemical reductants.
INOR 271
Microwave-assisted concurrent tandem catalysis (CTC) methodology for the copper-catalyzed amidation of aryl
halides
Elizabeth H. Shields, Matthew I. Lee, Douglas J. Brown, Shirley Lin, [email protected],
Amy R. MacArthur. Department of Chemistry, United States Naval Academy, Annapolis, Maryland, United States
A concurrent tandem catalytic methodology for the amidation of aryl halides are under investigation. The process starts
with a halide exchange reaction to form aryl iodides from less reactive aryl chlorides and aryl bromides. In a subsequent
step, the aryl iodide intermediate is consumed as the substrate for the C-N bond-forming reaction. Optimized conditions
for the transformation (metal/ligand loading, solvent, base, reaction time, temperature) will be presented as well as the
substrate scope for this methodology. Evidence that the reaction is occurring via a concurrent tandem catalytic
mechanism will be discussed.
INOR 272
Catalytic transfer hydrogenation of aryl-alkyl ketones using Cp*Ir(III)Cl pyridinesulfonamide complexes
Andrew Ruff1, [email protected], Benny C. Chan2, Abby R. O'Connor1. (1) Chem Dept,
College of New Jersey, Ewing, New Jersey, United States (2) The College of New Jersey, Ewing, New Jersey, United
States
Transfer hydrogenation is a useful method to reduce unsaturated bonds without the need for hydrogen gas. The
mechanism of hydrogen transfer commonly occurs via metal-ligand cooperativity between a basic moiety on the ligand
and the metal center. Although examples of iridium complexes containing diamine ligands that catalyze transfer
hydrogenation are known, no examples exist of iridium complexes that contain pyridinesulfonamide ligands, and the
catalytic activity of such complexes is not previously reported. The O’Connor group is interested in exploring new catalysts
for transfer hydrogenation catalysis using air and moisture tolerant iridium complexes containing pyridinesulfonamide
ligand scaffolds. Here we report the synthesis, characterization, and catalysis of new Cp*Ir(III)Cl (Cp* =
pentamethylcyclopentadienyl) complexes containing various pyridinesulfonamide ligands. These complexes are active in
hydrogen transfer catalysis, as aryl-alkyl ketones with electron withdrawing and electron donating substituents are
effectively reduced to an alcohol at 90oC (80-90% conversion) with 1 mol% of the iridium precatalyst. The reaction time
varies between 6 to 12 hours depending on the substrate; aryl-alkyl ketones that possess electron rich substituents are
reduced more slowly. Variation of the electronic parameters on the catalyst was also explored and it was found that the
addition of electron withdrawing groups slightly reduced catalytic activity. Preliminary results describing mechanistic
studies are also included in this presentation.
INOR 273
Catalytic transfer hydrogenation of aryl aldehydes using Cp*Ir(III) pyridinesulfonamide complexes
Christopher Kirby, [email protected], Abby R. O'Connor. Chem Dept, College of New Jersey, Ewing, New Jersey,
United States
Transfer hydrogenation is a powerful method to reduce polar bonds without the use of hydrogen gas. There are examples
of iridium and ruthenium based catalysts that reduce ketone and aldehyde substrates via transfer hydrogenation. The
most classic example is Noyori’s ruthenium-based catalysts that are able to hydrogenate a variety of aryl aldehydes and
ketones using 2-propanol as a hydrogen source. Work in the O’Connor
lab has focused on the synthesis of Cp* iridium(III)Cl complexes (Cp* =
pentamethylcyclopentadienyl) containing pyridinesulfonamide ligands and studying their ability to catalyze transfer
hydrogenation reactions. A library of iridium complexes possessing different pyridinesulfonamide ligands with electron-rich
and electron-poor substituents was prepared. These complexes were evaluated in the catalytic transfer hydrogenation of
aryl aldehydes. An exciting feature of this catalysis is that no additives are needed for these reactions and the catalysts
are tolerant of air and moisture. Benzaldehyde is efficiently reduced to benzyl alcohol in over 99% yield in reactions
conducted for 6 hours at 90°C using 1mol% of iridium complex. Five different iridium precatalysts containing different
pyridinesulfonamide ligands were screened for this reaction to explore the impact the electronics on the catalyst play on
the reduction reaction. Aryl aldehydes with electronically different substituents are also readily reduced to alcohols in good
yields under similar reaction conditions using the iridium precatalysts. Progress towards catalyst optimization and
preliminary mechanistic information are also included. INOR 274
pH-dependent ceria-doped titanate nanotubes
Yakub Fam1, Shammi A. Ferdousi1, [email protected], King L. Yeung1,2,
Yaping Du3. (1) Chemical and Biomolecular Engineering Dept., The Hong Kong Univ of Sci Tech, Kowloon, Hong Kong
(2) Division of Environment, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong
Kong (3) Center for Applied Chemical Research (CACR), Xi'an Jiaotong University, Yanta District, China
Titanate nanotube (TiNT) is one of 1D-TiO2’s derivatives having attracted much attention due to its large surface area,
reduced grain boundaries, and facile charge transport and have been commonly applied in photocatalysis. However, its
photoactivity limitation in the UV-region has been a challenge up until now and one of the well-known solutions is by using
dopants, such as metal/metal-oxide nanoparticles, to narrow its too wide band gap. Ceria is one of the most abundant
rare-earth metal oxides featuring such capability owing to its larger absorption of solar spectrum as well as some
favorable properties, like chemical inertness, inexpensive, stability against photoirradiation and non-toxicity. Despite
limited reports about ceria-doped TiNT, it has never been properly reported about the exact location of ceria and its
distribution in/on TiNT. In this study, a TiNT precursor was prepared by a hydrothermal synthesis and then doped with a
ceria precursor via wet-impregnation method. It was found out that the adjustment of pH during impregnation influences
the amount, stability, and location of doped ceria nanoparticles. Moreover, the amount of valuable oxygen vacancy in
ceria was also affected by the treatment with and without pH adjustment. Furthermore, the doping of ceria conforms the
significant red-shift of TiNT’s light absorption from UV to visible range.
INOR 275
Sythesis and characterization of quaternary misfit-layer-compound-like ferecrystals
Richard Westover1, [email protected], David C. Johnson2, Jeffrey Ditto1. (1)
Chemistry, University of Oregon, Springfield, Oregon, United States (2) Chemistry, University Of Oregon, Eugene,
Oregon, United States
A new family of quaternary [(MX)z]m(TX2)n[(MX)z']o(T’X2)p (where X = Se, M = Sn, T = Mo or Ta and T’ = V or Nb)
ferecrystal compounds have been synthesized by expansion of the modulated elemental reactants method. These
compounds are not available from bulk synthesis methods and represent unprecedented compositional control on the
local level. X-Ray Reflectivity (XRR), In-plane and out-of-plane X-Ray Diffraction (XRD), Electron Probe Micro Analysis
(EPMA), Scanning Transmission Electron Microscopy (STEM), as well as electrical transport properties were used to
characterize this new family of structures.
INOR 276
Self-assembly of organometallic molecular films based on the azulenic scaffold linearly functionalized with both
isocyanide and thiol termini
Monisola K. Okeowo, [email protected], Cindy L. Berrie, Mikhail V.
Barybin. Chemistry, University of Kansas, Lawrence, Kansas, United States
Isocyanide and thiolate anchoring groups are commonly employed in molecular selfassembly on metal surfaces. This
presentation will detail the formation, spectroscopic properties, stability and reactivity of self-assembled monolayer (SAM)
films of a linear azulenic π-linker incorporating isocyanide and thiol junctions in the same molecule. A Reflection
Absorption Infrared spectrum of one of such films on the Au(111) surface is shown below. Self-assembly and properties of
a few other related new azulene-based SAMs will be discussed as well.
INOR 277
Chiral amplification by metal-ligand conjugation in chiral magnetic nanoparticles Jihyeon Yeom2,
[email protected], Nicholas Kotov1. (1) University of Michigan, Ann Arbor, Michigan, United States (2) Macromolecular
Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Chirality of inorganic nanomaterials has been considered of much important because they are of prime fundamental and
practical interest due to the favorable power-law scaling of near-field enhancements. The interest in the synthesis of chiral
nanostructures has been fueled by the potential application of chiral nanostructures in biosensing, telecommunication,
display technologies, diffraction-free patterning, and chiral catalysis. Although often associated with biochemistry due to
the numerous chiral bio-molecules, today chiral inorganic nanostructures have attracted much attention as such their
optical properties remain largely unexplored.
Here we demonstrated overwhelmingly amplified optical activity of transition metal/ligand complexes in chiral magnetic
nanoparticles (NPs) which has not been reported. We synthesized Co NPs or Ni NPs using L- or D-cysteine as ligand
molecules and they showed extremely high circular dichrosim signals. Calculated anisotropic gfactor was over ~0.02
which which is comparable to the values obtained for Agenhanced Au nanohelices and Au nanorods/fiber composites.
These chiral magnetic particles hold promise in future applications such as chiral sensing and catalysis in various fields.
INOR 278
Structure and properties of sodium enneaborate
Doinita Neiner1, [email protected], Yulia Sevryugina2, David M. Schubert1. (1) R&D Dept., U.S. Borax Inc., Rio Tinto,
Greenwood Village, Colorado, United States (2) Dept. of Chemistry, Texas Christian University, Fort Worth, Texas, United
States
Borate materials in which boron is bonded exclusively to oxygen have attracted attention due to their rich crystal chemistry
and uses in current and emerging applications related to energy, urbanization and agriculture. From a structural viewpoint,
boron in these materials can be tri- or tetra-coordinated, forming BO3 and BO4 units that may link via oxygen corner
sharing to form rings, cages, chains, sheets and networks. This paper presents recent studies on sodium enneaborate,
2Na2O·9B2O3·11H2O, a long known but never fully characterized phase in Na2O-B2O3-H2O phase diagram. In particular,
the crystal structure of this compound was elucidated for the first time. Details of the synthesis, single crystal X-ray
structure, thermal and other physical properties will be presented.
Fundamental building block in sodium enneaborate structure.
INOR 279
Wet-spinning of graphene fibers from giant graphene oxide sheets by adopting a series of amine alcohol solution
as coagulation solution
Chunyan Zhao2, [email protected], Wenjin Zeng2, Songzhao Tong2, Shenbin Mo2, Jian Wang2, Tianju Fan2, Wei
Tang2, Chunqiu Yuan2, Yidong Liu1, Yong Min2. (1)
School of Advanced Materials, Peking University Shenzhen Graduate School, New
Albany, Ohio, United States (2) Institute of Advanced Materials, Nanjing University of Posts and Telecommunications,
Nanjing, China n this study, we use giant lamellar graphite (500μm) to prepare graphene oxide (GO).
The amine alcohol solution was adopted as a coagulation liquid to integrate the large GO sheets into macroscopic fibers
by wet-spinning method. A meters-long graphene fibers were continuously spun from GO suspensions followed by
chemical reduction with HI(40％). Then, the mechanical performances and the electrochemical performance of the fiber
were investigated. The mechanical strength of the fibers before reduction can be achieved about 200 MPa, and a 430MPa
was obtained after the reduction. Both of the fiber existed with good flexibility, and the electronic conductivity of the fiber is
about 38 S/Cm.
INOR 280
Water based PAN conductive coatings for antistatic application
Yafei Feng2, [email protected], Xingming Liu2, Cunliang Ma2, Jiaxin Shen2,
Zhangqing Xiao2, Tianju Fan2, Songzhao Tong2, Yidong Liu1, Yong Min2. (1) School of
Advanced Materials, Peking University Shenzhen Graduate School, New Albany, Ohio,
United States (2) Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing, China
As one of the highest electrical conductive polymer, polyaniline has been widely applied in the field of conductive coating.
The organic solvent-based polyaniline coatings are toxic and costly. While water-based PAN coating share the benefits of
odorless, low toxicity and low cost, which was widely used. With the in-deep study, water-soluble polyaniline syntheses
become possible as well. In this paper, ammonium NH4S2O8 (APS) was used as the oxidant, dodecyl benzene sulfonic
acid (DBSA) as emulsifier, dodecanol as auxiliary emulsifier, and dodecyl benzene sulfonic acid as both emulsifier and
doping acid. Aqueous polyaniline was synthesized through microemulsion chemical oxidation. Studying the content of
polyaniline in the reaction system, reaction time, temperature, and acid concentration effect on conductivity of polyaniline
brought up preferred polymerization conditions. Electrical conductivity, dispersion, stability, and surface structure were
characterized as well.
INOR 281
Facile method to fabricate transparent, flexible conducing graphene thin films via liquid phase deposition
Chunqiu Yuan2, [email protected], Wei Tang2, Jian Wang2, Shenbin Mo2,
Chunyan Zhao2, Tianju Fan2, Songzhao Tong2, Yidong Liu1, Yong Min2. (1) School of
Advanced Materials, Peking University Shenzhen Graduate School, New Albany, Ohio,
United States (2) Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing, China
Graphene, a carbon with one-atom-thick layer of bonded-sp2 carbon atoms packed into two-dimensional honeycomb-like
lattice，has attracted tremendous interests in nanoelectronic devices, especially in the transparent conductive grapheme
films. Since its first exfoliation from graphite in 2004, many efforts, including CVD, Vacuum filtration, self-assembly, spin
coating, spray deposition, have been directed toward synthesizing graphene films. However，these cannot meet the
requirements of industrialization. In this paper, we introduce a new way to fabricate Graphene thin film, i.e., layer by layer
depositing the GO solution on the substrate. The liquid phase deposited thin film was then reduced by hydrazine hydrate,
hydroiodic acid , or high temperature . The thin films were characterized by various equipment, such as，UV/vis, FTIR,
CV, SEM, TEM, TGA/DSC, Roman, etc. It was found that we can use this way to achieve the transparent conductive
films, which has many advanced features and performance. The corresponding industrial applications will be addressed
during the presentation.
INOR 282
Supercritical CO2 method of graphene preparation
Jiaxin Shen2, [email protected], Yafei Feng2, Cunliang Ma2, Xingming Liu2, Zhangqing Xiao2, Tianju Fan2, Songzhao
Tong2, Yidong Liu1, Yong Min2. (1) School of
Advanced Materials, Peking University Shenzhen Graduate School, New Albany, Ohio,
United States (2) Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing, China
We research the nonchemical method of graphene preparation , here the nonchemical method is that the supercritical
CO2 method of graphene preparation ,the supercritical CO2 fluid under high temperature and high pressure liquid and the
gas boundary has disappeared, Its viscosity is smaller than liquid,but spread faster than liquid, so it has better mobility
and transfer performance, in addition, according to the different pressure and temperature, the property will change. So
we try to let Graphite fully infiltrates in supercritical CO 2 by using these characteristics, make the supercritical CO2
permeate between graphite layers, then decrease the pressure to make it expand, because of thebond is the interaction
between graphite layers, this interaction is weaker than the covalent bond, so the supercritical CO 2 expand and destroy
interaction between graphite layers,then the slice layers of graphite have been peeled off and we can obtain the single
layer graphene.And then we compare the production by the supercritical CO 2 method with traditional methods such as
mechanical stripping and gas stripping method,and analysis the effect of preparation graphene with different condition of
supercritical CO2 under different temperature, different pressure, etc.
INOR 283
Production of graphene by dry ice ball milling method
Zhangqing Xiao2, [email protected], Jiaxin Shen2, Yafei Feng2, Cunliang Ma2, Xingming Liu2, Tianju Fan2,
Songzhao Tong2, Yidong Liu1, Yong Min2. (1) School of
Advanced Materials, Peking University Shenzhen Graduate School, New Albany, Ohio,
United States (2) Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing, China
Graphene, because of its excellent performance, has a great potential for industrial applications. States researchers have
actively studied in the production of graphene, a common method of chemical vapor deposition (CVD) on the chemical,
the epitaxial growth method, the mechanical peeling method physically. These methods are currently unable to mass
production, though graphite oxide in water by chemical peel can allow for large-scale production of graphene nanosheets,
but there are many drawbacks, including poor complicated preparation process, as well as product quality and other
shortcomings. In addition, the introduction of the graphene sheet oxidizing a variety of oxygen-containing groups (such as
hydroxyl group, carboxyl group, epoxy group), tend to make the functionalized complex and the subsequent noncontrolled, these factors may also cause performance degradation of graphene, for example, resulting in low electrical
conductivity, structural defects, poor thermal stability and mechanical stability. We demonstrated that a simple and
efficient preparation of graphene milling techniques, our experimental approach is to dry ice with simultaneous addition of
the graphite powder and the ball mill pot in a closed, high-speed operation by a ball mill, ball peeling layer or layers of
graphite obtained graphite, dry ice expanded role is played, the role of graphite foam, helps to speed up the release of
graphite, ultimately graphene. This method is simple, feasible and strong, pure graphene such as access to benefits. We
also added during the milling process of analyzing a specific chemical reagent appropriate to obtain graphene with special
functional groups, such as potassium hydroxide (KOH), to give the hydroxy-functionalized graphene (G-OH).
INOR 284
Preparation and properties of different phase of hydrothermal synthesis of 3D graphene
Shenbin Mo2, [email protected], Songzhao Tong2, Chunqiu Yuan2, Wei Tang2, Jian Wang2, Chunyan Zhao2, Tianju
Fan2, Jiaxin Shen2, Yidong Liu1, Yong Min2. (1) School of Advanced Materials, Peking University Shenzhen Graduate
School, New Albany, Ohio, United States (2) Institute of Advanced Materials, Nanjing University of Posts and
Telecommunications, Nanjing, China
Graphene, as a 2D material attracts plenty of attention just because its unique space structure. As reported recently,
graphene has lots of excellent properties, such as great conductivity, thermal properties and also huge capacitivity.3D
graphene is a top research owing to its large surface area. Here, we report a new hydrothermal method to synthesis 3D
graphene, and by series of characterization methods to observe the different graphene phase. After observing the
scanning electron microscopy (SEM) image of the 3D graphene, we can find a law that there is a phase change in
different synthesis situations, with the changing of the temperature, time, and concentration, the phase of the 3D
graphene presenting a wonderful change, and also, there is a huge promotion of the electrochemical properties. These
findings prompt the development of graphene ultra-capacitors.
INOR 285
Synthesis and instability of cuprous nitride nanocrystals
Malinda Reichert, [email protected], Javier Vela. Iowa State University, Ames, Iowa,
United States
Cu3N nanocrystals were synthesized by nitridation of Cu2O nanocrystals using one of two different nitrogen sources,
ammonia (NH3) or urea (2HNCONH2). The morphology of the original Cu2O nanocrystals is not maintained upon
conversion to the Cu3N with either nitrogen source. The Cu3N nanocrystals decomposed to nanocrystalline CuO in water
and air at room temperature. Optical absorption, XRD, and TEM were used to fully characterize these three different
nanocrystalline phases. Further, the amount of ammonia produced during spontaneous Cu 3N decomposition to CuO was
quantified using the colorimetric indophenol method. The mole ratio of Cu3N starting material to ammonia produced was
1:0.6, suggesting that this is a complex decomposition reaction where additional nitrogen products such as molecular
nitrogen (N2) are formed. The relative ease of inter-conversion between these materials is interesting because of their
possible application to catalysis/photocatalysis, optical storage devices, conductive inks, and high-speed integrated
circuits.
INOR 286
Categorizing defects in nanowires produced through electrodepostion
Kenneth J. Kysor1, [email protected], Duc Vu1, Colton Myers1, Benjamin D. Smith2. (1) Chemistry, Juniata College,
Port Allegany, Pennsylvania, United States (2) von Liebig Center for Science, Juniata College, Huntingdon, Pennsylvania,
United States
Our lives could be revolutionized by nanotechnology, technology based on the use of nano- and microparticles. These
particles have been studied for applications in a wide variety of fields such as medicine, renewable energy, and
electronics. Often, ordered particle assemblies are required for these applications. For instance, ordered arrays of
semiconductor nanowires have been used in electronic chemo- and biosensors as well as solar cells. Ordered arrays can
suffer due to particle inhomogeneity's and defects. Our project aims to classify and analyze images of nanowires to
determine relationships between the defects of wires and their physical properties. By measuring nanowire composition,
counting and categorizing defects, we will determine relationships between processes and outcomes of wire creation and
account for the common defects and abnormalities. The process can then be altered to yield the most ideal wires. In
addition, ideal wires will be harvested and integrated into ordered arrays separated from the ones that have common
defects. Understanding nanowire defects could provide a better capacity to improve nanoparticle assembly in the future.
INOR 287
Rapid synthesis of carbon nitride materials and composites for use in photocatalysis
Anthony Montoya, [email protected], Edward G. Gillan. Department of Chemistry, University of Iowa, Iowa City,
Iowa, United States
Graphitic carbon
nitride, g-C N or CN , has been extensively studied recently as a
and water splitting hydrogen generation. The focus of our research involves flexible precursor routes to porous nitrogenrich semiconducting carbon nitride networks. The
rapid solid state thermal decomposition (T ≤ 300 °C) of a reactive triazine-based precursor, trichloromelamine,
C3N3(NHCl)3 or TCM, under inert conditions results in the growth of thermally robust heptazine-based (C6N7 heterocyclic
ring) network structures. The cross-linked polymer-like CNx product is very thermally robust, surviving heating in air to
over 500 °C. Gas phase analysis (IR, MS) and solid-state analysis (IR, NMR, powder XRD, TGA, elemental analysis,
electron microscopy) are utilized to characterize these unusual non-crystalline nitrogen-rich carbon nitride materials.
Typically reactions yield yellow-orange colored, porous powders with formulas C3N4+xHy (0.5〈x〈0.8, 1〈y 〈3).
Hydrogen is typically present in nitrogen-rich CNx materials, but is often ignored or overlooked.
This presentation will detail recent success in both engineering porosity into TCMderived CN x using removable porogens
and also depositing CNx onto photoactive metal oxide powders (TiO2, WO3, CeO2) to form intimate composites. The assynthesized CNx materials and composites generally have visible absorption properties (E g ≈ 2.7eV for CNx) and some
were examined as photocatalysts for the oxidative photodegradation of methylene blue and methyl orange dyes under UV
irradiation. The photoactive CNx materials were also utilized to photodeposit 1-2 wt% noble metals (Pd, Pt, and Ag) onto
their surface from methanol solutions under UV irradiation. The metals appear to be well-dispersed on the carbon nitride
surface and have potential in hydrogenation or dehydrogenation reactions as well as water-splitting photocatalysis,
including catalysis using visible light. Preliminary investigations in select photocatalytic and electrocatalytic reactions will
be presented for select CNx materials and composites.
INOR 288
Thermal and electronic effects on the solvothermal formation of nanocrystalline WSe 2 in aromatic solvents
Michael P. Hanrahan, [email protected], Josh S. Edgar, Scott A. Darveau,
Christopher L. Exstrom. Department of Chemistry, University of Nebraska at Kearney, Kearney, Nebraska, United States
WSe2 is an earth-abundant semiconductor of interest for application as a photovoltaic absorber due to its high absorption
coefficient, phase stability, and a direct bandgap of 1.2-1.5 eV that matches well for optimum absorption by photovoltaic
cells. The solvothermal preparation method eliminates the need for expensive high-vacuum fabrication steps but the
formation of nanocrystalline WSe2 in solution has not been explored in detail. We report that the formation of WSe2, as
characterized by Raman spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, and inductively coupled
plasma optical emission spectroscopy (ICP-OES), in a series of aromatic solvents is sensitive to reaction temperature and
the electron donating/withdrawing nature of solvent molecule substituents. At temperatures of 155 oC and above, the
reaction between W(CO)6 and elemental selenium in yields WSe2 after heating for several hours. Conducting the reaction
at lower temperatures yields a material that has a Raman spectrum and XRD pattern consistent with trigonal crystalline
selenium; however, ICP-OES confirms the presence of tungsten. The role of the solvent in reaction intermediate formation
as linked to the favorability of WSe2 product generation will be discussed.
INOR 289
Formation of WSe2 thin films via annealing of a solvothermally prepared nanocrystalline precursor
Josh S. Edgar, [email protected], Michael P. Hanrahan, Christopher L.
Exstrom, Scott A. Darveau. Department of Chemistry, University of Nebraska at
Kearney, Kearney, Nebraska, United States
WSe2 is an earth-abundant semiconductor of interest for application as a photovoltaic absorber due to its high absorption
coefficient, phase stability, and a direct bandgap of 1.2-1.5 eV that matches well for optimum absorption by photovoltaic
cells. The solvothermal preparation method eliminates the need for expensive high-vacuum fabrication steps but the asmade nanoparticles do not exhibit a sufficient degree of crystallinity or specific crystalline face orientation be cast as
suitable thin films for photovoltaic devices. We have successfully fabricated phase-pure WSe2 thin films, as characterized
by Raman spectroscopy and x-ray diffraction, via the annealing of either nanocrystalline WSe2 or a tungsten-selenium
precursor material that was solvothermally prepared from W(CO) 6 and elemental selenium in an aromatic solvent.
Materials were annealed in a homemade physical vapor deposition apparatus in an argon atmosphere. The annealing
process significantly improved the crystallinity of asmade WSe 2 and successfully converted tungsten-selenium precursor
material to WSe2 films that were highly (002) face-oriented.
INOR 290
Metal-sulfur-arene semiconducting frameworks
Huaiyuan Hu1, [email protected], Thomas P. Vaid2. (1) chemistry , The university of Alabama, Tuscaloosa,
Alabama, United States (2) Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States
The metal-organic framework (MOF) [Pb3(C6S6)]n has been reported by our group. It has a band gap of 1.7 eV and a
room-temperature conductivity of approximately 2 x 10 -6 Ω-1cm-1. Doping [Pb3(C6S6)]n with In or Tl leads to an increase of
conductivity to approximately 3 x 10-5 Ω-1cm-1. To further study this type of semiconducting MOF, new arenepolythiols
need to be designed and synthesized. Naphthalene-octathiol, acetyl protected 9, 10-dimethylanthracene-2,3,6,7-tetrathiol
and pyrene-1,3,6,8-tetrathiol were synthesized and characterized. Pb, Cd and Tl were investigated to fabricate
metalsulfur-arene frameworks with naphthalene-octathiol and pyrene-1,3,6,8-tetrathiol. Among those, [Pb4(C10S8)]n,
[Tl8(C10S8)]n and [Tl8(C16S4)]n are semiconducting.
INOR 291
Sulfonium derivatives of the [closo-1-CB11H12]- anion as polar liquid crystals
Piotr Zagorski1, [email protected], Jacek G. Pecyna2, Piotr Kaszynski2,3. (1) Department of Chemistry, Middle Tennessee
State University, Murfreesboro, Tennessee, United States (2) Department of Chemistry, Vanderbilt University, Nashville,
Tennessee,
United States (3) Faculty of Chemistry, Universityt of Łódź, Łódź, Poland
Dielectric anisotropy, Δε, is one of the key factors affecting the electro-optical properties of materials for LCD applications.
Its magnitude is proportional to the molecular dipole moment: the higher the dipole moment, the higher the Δε and lower
Vth and operating voltage. Our previous investigations have shown that sulfonium zwitterions of the [closo1-CB9H10]- anion exhibit high Δε.[1,2] Analogous derivatives of the [closo-1-CB11H12]- anion are more attractive due to the
greater availability of the boron cluster. Here, we present the synthesis and investigation of liquid crystalline properties of
1-sulfonium (1) and 12-sulfonium (2) derivatives of the [closo-1-CB11H12]- anion. Thus, 12-alkyl derivatives 3 are converted
into thiols 4, which were then alkylated to give the corresponding sulfonium derivatives 1. Similarly, 1-alkyl derivatives 5
were thiolated at the B(12) position and subsequently converted to zwitterions 2. The new compounds were analyzed by
thermal, optical and dielectric methods.
References:
1. Pecyna, J.; Kaszynski, P.; Ringstrand, B.; Bremer, M. J. Mater. Chem. C, 2014, 2, 2956-2964.
2. Ringstrand, B.; Kaszynski, P. J. Mater. Chem. 2011, 21, 90-95.
INOR 292
Liquid crystalline derivatives of the [closo-B12H12]2- anion
Pawel Tokarz2, [email protected], Piotr Zagorski2, Piotr Kaszynski1,3. (1)
Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States
(2) Department of Chemistry, Middle Tennessee State University, Murfreesboro,
Tennessee, United States (3) Faculty of Chemistry, University of Łódź, Łódź, Poland
Our previous investigations demonstrated that the [closo-B10H10]2- anion is a viable structural element of highly
quadrupolar liquid crystals with interesting photophysical properties.[1] The analogous derivatives of the [closo-B12H12]2dianion were unavailable due to lack of appropriate synthetic methods. We now have developed functionalization of and
functional groups transformations in the [closo-B12H12]2- cluster and prepared quadrupolar derivatives of structure I and ion
pairs of structure II. We will present the new synthetic methodology and results of thermal, optical and spectroscopic
analyses of the new compounds.
References:
1. Jankowiak, A.; Balinski, A; Harvey, J. E.; Mason, K.; Januszko, A.; Kaszynski, P.;
Young Jr. V. G.; Persoons, A. J. Mater. Chem. C, 2013, 1, 1144
INOR 293
New network of Mn12 molecules
Annaliese E. Thuijs, [email protected], George Christou, Khalil A. Abboud. Department of Chemistry, Univ of Florida,
Gainesville, Florida, United States
The title dodecanuclear complex was synthesized by reaction of Mn2+ and Ce4+ in nitromethane and an excess of acetic
acid. The compound has the formula [Mn12O12(O2CMe)12(NO3)4(H2O)4] and is distinct from the previously known
[Mn12O12(O2CMe)16(H2O)4]. This new Mn12-type structure represents the first example of a Mn12 molecule containing
nitrate ligands that was made directly. Previous versions have been synthesized from the use of nitric acid and the
preformed
[Mn12O12(O2CCH2But)16(H2O)4], but resulted in low yields and required challenging reaction setups. Although many
derivatives of the Mn12 molecule have been synthesized with different carboxylate groups including benzoate, tert-butyl
acetate, pivalate, phosphonate, and dichloroacetate; there have been few changes observed in the overall core of the
structure regardless of the carboxylate employed. This complex is unique from other Mn 12 molecules in that there is a
pseudo 3-D network created by hydrogen bonds between the protons of the aqua and nitrate ligands of neighboring Mn12
molecules making this the first linked network of Mn12 molecules.
INOR 294
Functionalization of GaP substrates for use in photoelectrochemical cells
Owen Williams1, [email protected], Alan H. Cowley2, Michael J. Rose3. (1)
The University of Texas at Austin, Austin, Texas, United States (2) Dept of Chem
Biochem, University of Texas at Austin, Austin, Texas, United States (3) Dept of
Chemistry, University of Texas at Austin, Austin, Texas, United States
The use of group III-V semiconductors in photoelectrochemical (PEC) cells allows for the generation of the large voltage
differences necessitated by kinetically difficult transformations, while avoiding the use of metal oxide semiconductors.
Gallium phosphide (GaP) is well suited for the reduction of carbon dioxide due to its large band gap (2.24 eV), but suffers
from high defect densities at the surface due to corrosion. Previous reports indicate that passivation of GaP has been
achieved on both 100 and 111A surfaces, however, GaP(111B) surfaces are resistant to chemical modification due to the
reactivity of apical phosphine moieties. Preliminary work herein has focused on strategies to covalently modify these
surfaces, typically through nucleophilic attack by semiconductor P-OH moieties, which can be generated by a piranha
(H2SO4/H2O2) etch. In order to develop a strategy in parallel with chlorination procedures performed on Si(111) surfaces,
treatment with triflic anhydride has afforded a leaving group (-OTf) covalently attached to the surface. This surface was
shown to be susceptible to nucleophilic attack by carbanionic reagents. By using halogenated phenyl Grignard reagents, it
may be possible to further functionalize the semiconductor surface through C-C bond coupling reactions. In related work,
the development of a method for interfacing GaP or GaP/Al2O3 surfaces with metallic Cu is underway. Copper metal is
known to be catalytically active for CO2 reduction, and is unique in that it favors the production of hydrocarbons rather
than CO. Interestingly, reports of hybrid PECs with GaP/Cu are sparse in the literature. The preliminary findings and
challenges of assembling such a device utilizing atomic layer deposition will be presented.
INOR 295
Thermodynamic stability of aqueous metal clusters: A dynamic approach
Thomas J. Mustard, [email protected], Lindsay A. Wills, I-Ya Chang, Douglas A. Keszler, Paul H. Cheong.
Chemistry, Oregon State University, Corvallis, Oregon, United States
Metal hydroxide and oxide clusters have broad applications in electronics as thin film transistors. Understanding the vast
array of metal hydroxide and oxide clusters formed in aqueous solutions is a long-standing challenge in geochemistry with
broad consequences for the environment and high technology. The acid-base chemistry of these aqueous metal hydroxo
and oxo clusters in solution are poorly understood. Previous static studies of the mono aluminum cluster correctly
predicted the protonated and aquanated states at various pH values. Using both static and dynamic quantum models, an
array of protonation states of select aluminum aqueous clusters were investigated. Our computations predict that clusters
of medium to large size (Al2, Al3, and Al8) prefer at least one deprotonation is energetically favorable. The deprotonated
metal hydroxo cluster relative stabilities over a pH range will give insight to cluster formation conditions and selective
synthesis.
INOR 296
Computational study of polyoxometalate formation mechanisms
Lindsay A. Wills, [email protected], Dylan B. Fast, Michelle Dolgos, Paul H.
Cheong. Chemistry, Oregon State University, Corvallis, Oregon, United States
Polyoxometalates and metal hydroxo clusters exist in a vast array of structural forms under aqueous conditions, and some
of these clusters have recently been used in sustainable techniques for making metal oxide thin films. However, little is
understood about the formation processes from monomers to clusters and from clusters to thin films. Additionally, it is
very difficult to probe these processes through experimental techniques alone. We have used computations to determine
the likely pathways through which these clusters form and deposit into films. Dynamic simulations were performed
on Group V polyoxometalates to determine these mechanisms. Group V
polyoxometalates are a cluster family to start with because the films formed from these clusters are of particular interest
for applications in electronics. Additionally, as compared to metal hydroxo clusters, these clusters have a relatively
uncomplicated and well-defined protonation state, which reduces the complexity of the required simulation. With proper
understanding of cluster mechanisms, new clusters could be synthesized leading to higher quality films and devices.
INOR 297
Carbon nanofoams as porous scaffolds for iron-air battery electrodes
Maximillian F. Mayther, [email protected], Sean D. Murphy, [email protected], Justin C. Lytle. Chemistry, Pacific
Lutheran University, Tacoma, Washington, United
States
Metal-air batteries discharge greater amounts of specific energy than Li-ion batteries, but are limited to discharging lesser
amounts of specific power because the rates of the catalytic reduction of molecular oxygen and the corresponding
oxidation of metal anodes are kinetically limited. We hypothesize that if the surface area of metallic iron anodes is
increased by conformally depositing FeO x onto carbon nanofoams, then the specific power that these electrodes
discharge will increase because the amount of surface area on an electrode is directly related to the current density that it
can sustain. Carbon nanofoams are prepared by infiltrating and pyrolyzing phenolic monomer within carbon fiber matrices.
Then, conformal coatings of FeOx are deposited onto the macropore walls of carbon nanofoams. The resulting materials
were electrochemically cycled using CV to demonstrate that they undergo reduction to metallic iron and subsequent
oxidation. While bare carbon nanofoams display electrochemical capacitance, the FeOx/CNF materials display
pseudocapacitance and redox chemistry as iron atoms at the surface of each electrode are controllably reduced and then
oxidized. The specific power of these materials was evaluated by galvanostatic cycling to be capable of discharging for
~20 seconds at rates as high as 10 A/g. The capacity of these electrodes appears to fade rapidly (50% loss in 10 cycles),
which led us to measure the concentration of iron cations in solution by UV-vis spectroscopy in order to see if the loss of
iron from the electrode corresponds with the loss of redox capacity that was observed. Future work will include
approaches to improve the cyclability of these materials, as well as to compare the specific power output of this system to
a nonporous and planar analogue.
INOR 298
Doping Cu2ZnSnS4 nanorods with tetrahedral, high spin metals: Co2+, Mn2+, and
Ni2+
Michelle Thompson1, [email protected], Malinda Reichert2, Javier Vela-Becerra3. (1)
Chemistry, Iowa State University, Ames, Iowa, United States (2) Iowa State University,
Ames, Iowa, United States (3) Dept of Chem, Iowa State University, Ames, Iowa, United
States
Due to its large absorption coefficient and direct band gap (~1.5 eV), Cu2ZnSnS4 (CZTS) is a promising quaternary
semiconductor for solar energy conversion. CZTS is desired due to its composition of elements which are relatively nontoxic, earth abundant, and widely distributed. We show successful doping of the CZTS nanorods with three different first
row transition metals, characterized by Powder X-Ray
Diffraction, UV-Vis Absorption, Diffuse Reflectance, Transmission Electron Microscopy,
Energy Dispersion X-Ray Spectroscopy, Raman Spectroscopy, and Electron
Paramagnetic Resonance Spectroscopy. These high spin metal cations (Mn2+, Ni2+, and Co2+) could be capable of
inducing novel magnetic properties in the doped CZTS rods, with possible applications in data storage and spintronics.
INOR 299
Efficient dye degradation via non-photocatalytic route by perovskite type LaNiO3-δ materials
wei zhong2, [email protected], Chung-Hao Kuo3, Sheng-Yu Chen4, Steven L.
Suib1. (1) Univ of Connecticut, Storrs Mansfield, Connecticut, United States (2) Institute of Materials Science, University of
Connecticut, Willimantic, Connecticut, United States (3) University of Connecticut, Storrs, Connecticut, United States
Perovskite type materials LaNiO3-δ (LNO) was found to degrade Methyl Orange (MO) dye in aqueous solution at room
temperature without additional chemicals or light. The concentration of MO was decreased from 100% to around 10%
after 6h. Degradation mechanism was raveled by characterization techniques such as XRD, SEM, TGA, FTIR, XPS, UVVis, HPLC and ESI. MO was approved to have two intermediates, N, Ndimethyl-p-phenylenediamine (DPD) and Sulfanilic
acid, during degradation.
Degradation under such mild condition, MO was treated by two synergic effects. Nickel (+2, +3) is reduced during MO
degradation; Carbonate formed on LNO surface could speed up azo bond cleavage compared with much slower MO
degradation under N2 condition. Bulk and surface property of perovskite, like mixed valence state, is its advantage for dye
degradation and/or organic substrate reaction. Some organic reaction with LNO is under progress.
MO dye degradation under dark condition
Infrared spectra of MO(a),LNO before (b)and after(c) reaction
INOR 300
Functionalization of metal oxide surfaces for photoelectrocatalysis of CO 2 reduction
Satu K. Heiskanen1, [email protected], Joshua M. Ziegler1, David A. Rider2,
John D. Gilbertson1. (1) Chemistry, Western Washington University, Bellingham,
Washington, United States (2) Chemistry MS-9150, Western Washington University, Bellingham, Washington, United
States
Carbon dioxide is a major industrial waste product as well as a significant greenhouse gas. Conversion of carbon dioxide
to useful chemical feedstocks - such as syn-gas - is necessary for the development of a more carbon-neutral future.
Common electrodes have previously been demonstrated to catalyze the reduction of CO2 to other C1 products utilizing a
high over potential. Copper (I) oxide has demonstrated the ability to catalyze the reduction of CO 2 to C1 products in
aqueous systems and can be extended to organic media. 4-vinylaniline was covalently grafted to the surfaces of various
metal oxides including ITO, Cu2O and Al2O3 using a UV irradiation photografting procedure. The resulting surface was
characterized by XPS, AFM, FT-IR, and contact angle goniometry. The electrochemical and catalytic activities of the
samples were analyzed in organic media by cyclic voltammetry and potentiostatic methods. Gas chromatography of the
headspace of a photoelectrochemical reactor for CO 2 reduction was used to determine product selectivity and catalytic
activity. When irradiated with a monochromatic light source (l = 405nm), an increased reduction current was observed in
the Cu2O samples. The details of the photoelectrocatalysis of the CO 2 reduction using photografted, 4-vinylaniline-coated
Cu2O samples will be presented.
INOR 301
Control of the crystalline phase and morphology of CdS deposited on microstructured surfaces by chemical bath
deposition
Deshani Fernando1, [email protected], Mughees Khan2, Yolanda
Vasquez3. (1) Chemistry, Oklahoma State University, Stillwater, Oklahoma, United
States (2) Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, United States
Semiconductor materials prepared as nanostructured particles and thin films are extremely important in technology with
potential applications in optoelectronic devices, photo-sensors, transducers and as optical waveguides. Among several
synthetic methods that have been developed to produce nano-scale, micro-scale, and thin films of CdS, chemical bath
deposition (CBD) is one of the simplest and inexpensive largearea deposition techniques. The microtopography or
roughness of the surface, however, can affect the quality of the film by influencing the morphology, uniformity, or crystal
phase of the CdS film. Here, we have demonstrated that thin films of CdS can be successfully patterned on surfaces
bearing micropillars as a model surface for roughness. The phase purity of CdS deposited on the micropillar surfaces is
uniform and conformal with the formation of packed clusters on the micropillars at pH 10 that form flower-like structures at
long deposition times. Smaller crystallites were observed on micropillar arrays at pH 8 with “network” like structures
observed at long deposition times. Additionally, by controlling the pH and Cadmium to Sulfur ratio of the chemical bath,
the hexagonal and cubic crystal phases of CdS were both accessible in high purity. This study provides a way to control
the crystal phase and morphology of CdS on patterned surfaces at temperatures as low as 85°C.
INOR 302
Colloidal synthesis of silicon and germanium nanorods and nanowires
Xiaotang Lu1, [email protected], Brian Korgel2. (1) Materials Science and
Engineering Graduate Program, the University of Texas at Austin, Austin, Texas, United
States (2) McKetta Department of Chemical Engineering, the University of Texas at Austin, Austin, Texas, United States
Colloidal synthesis of silicon (Si) and germanium (Ge) nanorods and nanowires was studied using various metal seed
particles and reactant approaches. Luminescent Si nanorods were formed by tin-seeded solution-liquid-solid (SLS) growth
with trisilane reactant. The Sn-seeded growth of Si nanorods was further simplified to a single step by in situ reduction of
[Sn(hmds)2] by trisilane. Ge nanorods and nanowires could be produced using this approach with diphenylgermane and
the addition of trisilane as a Sn reducing agent. Isotetrasilane, neopentasilane and cyclohexasilane were also studied for
Si nanorod growth, and all three reactants enabled nanorod formation at lower growth temperatures. The single-step
growth of Si and Ge nanowires in supercritical solvents by supercritical fluid-liquid-solid (SFLS) growth was also studied
and so far, Ge nanowires grow by in situ formation of Mn, Fe, Ni, Ga, In, Pb, Bi seeds and Si nanowires by in situ
formation of Cu, Ga, In seeds.
INOR 303
Graphene oxide assisted hydrothermal carbonization of carbon hydrates
Deepti Krishnan1, [email protected], Kalyan Raidongia1, Jiaojing Shao2, Jiaxing Huang1. (1)
Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States (2) Materials Science,
Tianjin Univeristy,
Tianjin, China
Biomass is a cheap, ecofriendly and renewable raw material for the production of functional carbonaceous materials.
Hydrothermal carbonization (HTC) of biomass typically produces carbon materials that are insulating. Using simple
carbon hydrates such as glucose and cellulose as a model system for biomass, here we demonstrate that graphene oxide
(GO) sheets can promote HTC conversion. Adding a very small amount of GO to glucose (e.g., 1:800 weight ratio) can
significantly alter the morphology of its HTC product, resulting in more conductive carbon materials with higher degree of
carbonization. HTC treatment of glucose is known to produce a dispersion of micron sized carbon spheres. In the
presence of GO, HTC treatment results in dispersed carbon platelets of tens of nanometers in thickness at low mass
loading level, and freestanding carbon monoliths at high mass loading levels. Control experiments with other carbon
materials such as graphite, carbon nanotubes and carbon black show that only GO has significant effect in promoting
HTC conversion, likely due to its good water processability, amphiphilicity and two-dimensional structure that may help to
template the initially carbonized materials. GO offers an additional advantage in that its graphene product can act as an
in-situ heating element to enable further carbonization of the HTC carbon monoliths upon microwave irradiation. Similar
effect of GO is also observed for the HTC treatment of cellulose.
INOR 304
New multifunctional Schiff base as fluorescence sensor for Al 3+ and colorimetric sensor for CN- in aqueous
media: an application to bioimaging
Ga Rim You, [email protected], Yu Jeong Na, Seong Youl Lee, Ka Young Ryu,
Cheal Kim. Fine Chemistry, Seoul National University of Science & Technology, Seoul, Korea (the Republic of)
A multifunctional fluorescent and colorimetric receptor 1 ((E) N'-((8-hydroxy-1,2,3,5,6,7hexahydropyrido[3,2,1-ij]quinolin-9yl)methylene)benzohydrazide) for the detection of both Al3+ and CN- in aqueous solution has been developed. Receptor 1
exhibited an excellent selective fluorescence response toward Al3+. The sensitivity of fluorescent based assay (0.193 μM)
for Al3+ is far below the World Health Organization (WHO) guideline of the drinking water (7.41 μM). In addition, receptor 1
showed excellent detection ability at a wide pH range of 4-10 and also in living cells. Moreover, the receptor 1 showed a
highly selective colorimetric response to CN- by changing its color from colorless to yellow immediately without any
interference by other anions.
INOR 305
Colorimetric organic chemo-sensor for Co2+ in a fully aqueous environment
Hyun Yong Jo, [email protected], Seul Ah Lee, Jae Jun Lee, Yong Sung Kim, Cheal Kim. Seoul National University
of Science & Technology, Seoul, Korea (the
Republic of)
A new highly selective and sensitive colorimetric chemosensor 1 for Co2+ was developed. The receptor 1 sensed Co2+ by
changing its color from yellow to orange in aqueous solution. Moreover, 1 could be used as a practical, visible colorimetric
test kits for Co2+.
INOR 306
Water-soluble chemosensor for detecting Al3+ in aqueous media and living cells
JaeJun Lee1, [email protected], Pan-Gi Kim2, Cheal Kim3. (1) Seoul National
University of Science & Technology, Seoul, Korea (the Republic of) (2) Department of Forest & Environment Resources,
Kyungpook National University, Sangju, Korea (the
Republic of)
A new water-soluble carboxylic-functionalized chemo-sensor 1 was designed and synthesized. 1 exhibited the selective
fluorescence enhancement toward aluminum ions in aqueous solution. The binding mode of the 1-Al3+ complex was
determined to be a 1:1 complexation stoichiometry through Job plot, ESI-mass spectrometry analysis, and 1H NMR
titration. In addition, in vitro studies with fibroblasts showed fluorescence in the presence of both the receptor 1 and Al3+.
INOR 307
Investigation into zinc (II) ion coordination with tetracycline via fourier transform infrared spectroscopy
Botai Xuan, [email protected], Alex Gilbert, [email protected], Sabrina
G. Sobel. Chemistry, Hofstra University, Hempstead, New York, United States
Tetracycline is a broad spectrum polyketide antibiotic produced by the Streptomyces genus of Actinobacteria, indicated for
use against many bacterial infections. Essential zinc (II) ion present in extracellular matrix metalloproteinases (MMP’s) is
commonly found within ailments treated by tetracycline. It is speculated that tetracycline is involved in coordination of the
zinc (II) ions, thus lowering the availability of the zinc ions present within the extracellular MMP’s; however, exact
coordination sites of zinc on tetracycline is still unknown. This exploratory work aims to investigate tetracycline’s
coordination with zinc (II) ions in several pH controlled solutions. Previous research conducted via NMR and Spartan
computer modeling narrowed potential binding site to the phenolic oxygens and the tricarbonyl system. Fourier transform
infrared spectroscopy (FTIR) was used to analyze the vibrational modes of both tetracycline and zinc-bound tetracycline
in pH 6.0, 6.4, 6.8, 7.2 buffered solutions to determine the zinc binding mode. Differences in IR spectra revealed an
observable peak alteration within the fingerprint region of the spectra. Prominent amine scissoring at approximately 1600
cm-1 present within unbound tetracycline complexes is greatly diminished within zinc complexed tetracycline; this suggests
that the amine located on the tricarbonyl ring of tetracycline is the primary site for zinc (II) ion binding.
INOR 308
Measurement of NMR relaxation rates in a series of cobalt (II) β-diketonates
Robert R. Baum, [email protected], David L. Tierney. Dept of Chem and Biochem, Miami University, Oxford, Ohio,
United States
Relaxation of nuclear magnetic resonance in paramagnetic systems is sensitive to subtle structural dynamics. We report
here 19F NMR linewidths of a series of cobalt (II) β-diketonates, which have very clear structural dynamics based on
temperature. We are measuring NMR relaxation rates, in order to compare the effective electron relaxation rates of these
complexes. These will be compared to complexes that show more subtle dynamics. The longitudinal relaxation rate (T 1)
and transverse relaxation rate (T2) for both 19F and 1H will be reported at two different magnetic fields (4.7 T and 7.0 T).
The extracted correlation times (τ1c and τ2c) will also be reported.
INOR 309
Monitoring the ring opening polymerization of hexachlorocyclotriphosphazene through NMR spectroscopy
Jason A. Stiel1, [email protected], Claire Tessier2, Zin-Min Tun3. (1) Chemistry,
The University of Akron, North Canton, Ohio, United States (2) University of Akron,
Akron, Ohio, United States (3) Chemistry, The University of Akron, Akron, Ohio, United
States
Polyphosphazenes are the largest class of inorganic polymers, but due to irreproducibility of the polymerization for the
parent polymer [PCl2N]n, they have yet to reach their full potential for viable applications. A reason for the irreproducibility
is that mechanism is not fully understood, but it has been shown that superacids could play a significant role in the
polymerization. One way to possibly improve the synthesis of [PCl 2N]n is to have a better understanding of the thermal
ring opening polymerization of hexachlorocyclotriphosphazene. Our goal was to follow the polymerization in a sealed
NMR tube via 31P NMR. With this NMR study we hope to identify any possible superacids or intermediate species present
to further understand this polymerization.
INOR 310
Scalar and spin-orbit relativistic calculations of 1JWH in Cp2WH2 complexes
T A. Mobley, [email protected]. Chemistry, Grinnell College, Grinnell, Iowa, United
States
Our group has been investigating the structure, bonding and reactivity of tungstenocene hydride complexes that contain
stannyl ligands (Cp2WHSnClR2). Recently we reported DFT computational studies that in part described the influence of
the hydride ligand position on the 1JWSn coupling constant.1 During these investigations it became apparent that minor
modifications of the geometry (e.g. due to changes in the functional utilized in geometry optimization) resulted in rather
large changes in the 1JWH coupling constant. This poster describes our systematic study of these effects in the simpler
Cp2WH2 molecule, concentrating on the two most influential factors, namely the W CpCentroid distance and the angle that
the W Cp centroid vector makes to the plane of the Cp (see Figure 1). Variation in these two geometric parameters across
the values observed in experimental (microwave structure) and DFT minimizations using a variety of functionals spans the
range from 71 to 101 Hz (the experimentally determined value is 74 Hz with a small solvent dependence).
[1] T. A. Mobley, C. I. Viquez Rojas “Scalar and Spin-Orbit Relativistic DFT Calculations of Nuclear Spin-spin Coupling in
Cp2WXSnR2 Complexes,” Poster 108, SMASH NMR conference, Santiago de Compostela, Spain, September 22-25,
2013.
Figure 1. Representation of Z-matrix formulation of CpWH2 utilized to study geometric dependence of 1JWH.
INOR 311
Investigating the stereoelectronic consequences of diphosphine ligands on M-P and M-Cl covalency in late
transition metal complexes
Courtney Donahue2, [email protected], Brian J. Bellott 3, Anastasia Blake2, Chelsie M. Forrest3, Jason M.
Keith1, Sam McCollom1, Scott R. Daly2. (1) Dept of Chemistry, Colgate University, Hamilton, New York, United States (2)
Chemistry,
University of Iowa, Coralville, Iowa, United States (3) Western Illinois University, Macomb, Illinois, United States
Diphosphines are commonly used ligands in transition metal catalysis because their substituents and structures can be
modified to optimize catalyst performance. For example, variations to bite angle (i.e. the P-M-P angle) have been shown
to affect catalysis rates, but it is less clear how bite angle affects bonding between the metal and phosphorus atoms. To
investigate this relationship, we used ligand K-edge X-ray absorption spectroscopy (XAS) to determine how bite angle
variations affect covalency in metal-ligand bonds. This technique probes transitions between 1s electrons localized on the
ligand donor atom and the antibonding molecular orbitals of metal-donor atom bonds. Peak positions in the spectra
represent the energies of electronic transitions, while peak intensities relate to the amount of 3p ligand character mixing in
the MOs. P and Cl K-edge XAS data were collected on a series of NiCl2 and PdCl2 complexes to investigate differences in
M-P bonding and M-Cl bonding as ligands were systematically changed between PPh3, dppm, dppe, dppp, and dppb.
DFT and TDDFT calculations were performed to corroborate our experimental findings, as well as study the effects of bite
angle versus twist angle. Results from both P and Cl K-edge data showed the expected differences between tetrahedral
and square-planar geometries, as well as differences caused by changing the metal from a first row (Ni) to second row
transition metal (Pd). P and Cl K-edge data of the Pd chelating diphosphine complexes show a small systematic shift in
the position of the spectral features, but the intensities are closely matched except in the case of Pd(dppe)Cl 2.
INOR 312
Photoinduced properties of bimetallic polypyridyl complexes
Tyler J. Whittemore, [email protected]. Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio,
United States
In order to create molecules for photochemotherapy (PCT) it is vital to create photoactive molecules that absorb low
energy light and have tunable excited state properties. The monometallic complex [Ru(biq)2(dpb)][PF6]2 (biq = 2.2'biquinoline; dpb = 2,3-bis(2-pyridyl)benzoquinoxaline) is a potential new PCT agent that undergoes ligand dissociation of
the dpb ligand when irradiated with visible light. The dpb ligand is a known anticancer agent through the production of
singlet oxygen. The substitution of the dpb ligand is attributed to the steric strain of the molecule imposed by the bulkiness
of the biq ligands. This steric strain is demonstrated in the lengthening of the Ru-dpb bonds and twisting of the biq and
dpb ligands in the resulting crystal structure. The coordination of rhenium carbonyl chloride to the dpb bridging ligand to
yields [(biq)2Ru(dpb)Re(CO)3Cl][PF6]2. The absorption associated with the Ru-dpb 3MLCT of the bimetallic complex redshifts into the the optimum PCT window. However, the coordination of the second metal stabalizes the complex and, as a
result, no photosubstitution is observed. Despite the considerable torsional strain of the biq ligands in the crystal structure
of the bimetallic, the Ru-dpb bond lengths decrease, and the dpb ligand becomes more planar, indicating the stabilizing
effect of the rhenium carbonyl moiety. The results indicate that both electronic and structural considerations are critical in
the design of PCT agents that undergo photosubstitution of bidentate ligands. Furthermore, we have shown the possibility
of stabilizing photolabile Ru(II) complexes by coordinating another metal, which has applications in bimetallic catalysis.
INOR 313
Colorimetric “naked-eye” Cu(II) chemosensor and pH indicator in an 100% aqueous solution
Ye Won Choi, [email protected], Myoung Mi Lee, Gyeong Jin Park, Kwon Hee
Bok, Tae Geun Jo, Cheal Kim. Fine Chemistry, Seoul National University of Science & Technology, Seoul, Korea (the
Republic of)
A new, highly selective and sensitive colorimetric chem-osensor 1 for detection of Cu2+ ions in aqueous solution was
developed. Receptor 1 detected Cu2+ ions by changing its color from colorless to yellow. Moreover, the Cu 2+-sensitive
compound was used as a colorimetric pH detector based on a color change due to 1-Cu2+ complex formation identifiable
via naked eye.
INOR 314
Chiral conducting polymers as efficient spin filters
Prakash C. Mondal1, [email protected], Claudio Fontanesi3, Ron Naaman2. (1)
Department of Chemical Physics, Weizmann Institution of Science, Rehovot, Rehovot,
Israel (2) Dept Chemical Physics, Rehovot, Israel (3) Department of Chemical and Geological Science, University of
Modena, Modena, Modena, Italy
Chiral conducting polymers (CCPs)1 have been widely employed in enantio-selectivity, electrochemical asymmetric
synthesis and optoelectronic devices. In the present work we investigated the spin selective electron transport through a
chiral conducting polymer when deposited on ferromagnetic nickel. The spin selectivity observed result from the chiral
induced spin selectivity (CISS) effect reported recently. 2 This effect results in spin selective electron conduction through
chiral molecules and the preferred spin depends on the handedness of the molecules and the applied electric field. In
addition, enantioselectivity of the modified electrode was observed in presence of chiral redox probes. The combination of
the CISS effect and the conductivity of the polymer allow, in principle, the production of spin-OLED3 that does not require
any ferromagnetic material.
References
1. Kane-Maguire, L. A. P.; Wallace, G. G. Chem. Soc. Rev., 2010, 39, 2545-2576.
2. Naaman, R.; Waldeck, D.H. J. Phys. Chem. Lett., 2012, 3, 2178−2187.
3. Nguyen, T. D.; Ehrenfreund, E.; Vardeny, Z. V. Science, 2012, 337, 204-209.
INOR 315
Synthesis of “rare earths – magnesium” master alloys by high temperature exchange reactions
Andrey V. Krylosov, Konstantin V. Maksimtsev, Ilya B. Polovov, [email protected],
Vladimir A. Volkovich, Oleg I. Rebrin. Department of Rare Metals and Nanomaterials,
Ural Federal University, Ekaterinburg, Russian Federation
Traditional way of manufacturing master alloys based on magnesium and rare earth metals (REM) includes fusing the
alloy components in a steel crucible. One of the disadvantages of the process is the high temperature that exceeds the
melting temperature of the components by over 400-500 0С. High temperatures result in losses of metals due to
evaporation and increase the construction materials corrosion. Metallothermic reduction with simultaneous alloy formation
is free from the above problems. In general the process of REM reduction by magnesium is described by the following
equation:
2 MeX3 + 3 Mg ↔ 3 MgX2 + 2 Me + Q
Despite the positive value of the Gibbs free energy change for this reaction the reduction process becomes possible due
to the formation of an alloy of reduced metal with excess reductant.
Thermal analysis data indicate that the most prospective salt mixtures for magnesium reduction of REM from the fluorides
with “magnesium-REM” master alloy formation are the mixtures of sodium and potassium chlorides. These salts can be
easily separated from the alloy during subsequent mechanical processing.
In a series of experiments “rare earths – magnesium” master alloys were produced with varying experimental conditions,
temperature, time of exposure, sodium and REM fluoride molar ratio, quantity of salt and metal used. The results of the
experiments were characterized by REM content in the obtained alloys, completeness of separation of salt and metallic
phases, shape and integrity of the ingot. Analysis of the results showed that increasing temperature leads to increase of
REM recovery. However rising temperature to 820–830 0С or higher causes increased losses of salt and metallic phases
due to evaporation. The optimal sodium and REM fluoride molar ratio equals to 4:1. Exceeding this value leads to
changes of physico-chemical properties of the electrolyte (viscosity, surface tension, melting temperature) that make the
formation of a united ingot more difficult. Compacting the alloy into a single ingot is facilitated when ratio “metal-salt” ratio
increases to 1:2.
It was found that the method of magnesium addition into the reaction mixture does not influence the outcome. This allows
simplifying the equipment design for implementation of the process. The proposed method of the master alloy synthesis
can be applied for the production of different metallic compositions.
INOR 316
Synthesis, structural characterization, and magnetic properties of dinuclear, tetranuclear, and polynuclear
lanthanide(III) complexes of a symmetric ditopic carbohydrazone based ligand (H 2L)
Santokh S. Tandon1,3, [email protected], Scott D. Bunge1, Sonya K. Adas1, Laurence K. Thompson2, C. Robert Lucas2.
(1) Chemistry and Biochemistry , Kent State
University, Kent, Ohio, United States (2) Chemistry, Memorial University, St. John's,
Newfoundland, Canada (3) Chemistry and Biochemistry, Kent State University, Salem, Ohio, United States
The reactions of a symmetric ditopic carbohydrazone based ligand (H 2L) with lanthanide (Ln(III)) salts result in the
formation of a variety of different products, depending on the metal ions and the reaction conditions. Reactions of LnX3 (X
= Cl or NO3) with H2L in the presence/absence of triethylamine (TEA) form dinuclear complexes, [Sm 2(µHL1)2(NO3)4]·2CH3OH·2H2O (1), [Nd2(µ-HL1)2(NO3)4]·2CH3OH·
2H2O (2), tetranuclear complexes [Ln4(HL)4(OH)4](anion)x(solvent)y (Ln = Ho (3) and
Yb (4)), [Dy4(HL)4(O)(N3)4](anion)x(solvent)y (5) and polynuclear complex
{[Pr2(HL)2]2(HL)(anion)x (solvent)y)n (6) in which dinuclear (Pr2) units are linked together in a network via L. The x-ray
crystal structures, spectroscopic, and magnetic properties of these complexes will be reported.
INOR 317
Speciation studies between a novel pincerlLigand with lanthanum (III) salts
Daniel Kremer2, [email protected], Marites Guino-o2, Ana De Bettencourt
Dias1. (1) University of Nevada, Reno, Reno, Nevada, United States (2) Chemistry Department, University of St. Thomas,
Saint Paul, Minnesota, United States
Interest in lanthanide luminescence stems from an expanding need to implement luminescent materials in optical
telecommunications, coatings, biological probes, theranostics, and molecular imaging applications. Trivalent lanthanide
ions in particular are utilized in these applications as they possess sharp and easily recognizable emissions in the visible
and near-infrared ranges, unlike the broad emissions of organic chromophores. This unique optical property is a result of
4f shielding by filled 5s2 5p6 subshells leading to “buried” f-f transitions. For the same reason, however, lanthanide ions
possess low absorption coefficients. To remedy this problem, organic ligands are applied to sensitize the lanthanide ion
by transferring excited electrons from ligand to metal, thus making otherwise inaccessible f-f transitions accessible.
Herein, we report NMR scale speciation studies with lanthanum (III) salts and a novel pincer ligand.
INOR 318
Chiral light emitting ionic liquids
Ben Zercher, [email protected], Todd Hopkins. Chemistry, Butler University, Indianapolis, Indiana, United States
The generation of circularly polarized light is important in many applications, including holographic displays, 3-D movies,
and bioanalytical techniques. This presentation describes the synthesis and fluorescent analysis of chiral light emitting
ionic liquids made from lanthanide-doped chiral amino acid ionic liquids. The ionic liquids were composed of
tetrabutylammonium (TBA) cation countered with l-valine, d-valine, lproline, or d-proline anions. These ionic liquids of
varying amino acid composition were doped with europium trifluoromethanesulfonate (triflate) salt and analyzed by
circularly polarized luminescence (CPL). The sign of CPL signal corresponded to the handedness of the amino acids in
the ionic liquids. Europium triflate concentration dependent CPL in both [TBA][Val] and [TBA][Pro] ionic liquids was
measured from 5 to 30 millimolal. CPL concentration dependent results indicate that ionic liquid properties play an
important role.
INOR 319
New calix[4]arene based precursors for stationary phases useful in separation of rare earth metals
Sreejit Menon1, [email protected], Joseph A. Schmidt2. (1)
Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio, United States (2) MS 602, University
of Toledo, Toledo, Ohio, United States
The rare earth elements (REE), composed primarily of the fifteen lanthanides, find broad application in many modern
devices making these elements indispensable and important to the sustainable, green world approach prevalent these
days. Liquid-liquid extraction for the separation of lanthanides using a calix[4]arene scaffold with coordinating ligands on
its lower rim has been studied for many years. In the present work, we discuss the synthesis and characterization of new
chlorine and amine terminated 2-alkyl-p-tert-butylcalix[4]arenes with phosphine oxide, ketone, ester, and CMPO based
coordinating ligands incorporated on the lower rim. These new moieties will act as useful precursors for the synthesis of
functionalized stationary phases. Novel heterogeneous materials will be prepared by immobilizing the 2-functionalized
amine terminated calix[4]arene derivatives on the surface of a solid support like silica and will find application in
chromatographic separation of REE from a wide range of electronic wastes or slurries, subsequently helping to isolate
these metals in high purity. Before immobilization onto a solid support, we have investigated the extraction efficiencies of
these new calix[4]arenes for rare earth metals in liquid-liquid extraction in order to confirm that functionalization at the 2position of the calix[4]arenes does not interfere with the extraction properties of the coordinating ligands on the lower rim.
INOR 320
Magnetic properties of mononuclear uranium-acetylide complexes
Robert Higgins1, [email protected], Brian Newell2, Anthony K. Rappe1,
Matthew P. Shores3. (1) Colorado State University, Fort Collins, Colorado, United States
(2) 1872 Campus Delivery, Colorado State University, Fort Collins, Colorado, United
States (3) Department of Chemistry, Colorado State University, Fort Collins, Colorado,
United States
Magnetic properties of U(IV) molecules are poorly understood and coordination environment has yet to be correlated with
these properties.1 In this vein, [U(dmpe)2
(CCPh)4] (1) and [U(dmpe)2(CCPh)5](Li·Et2O) (2) , where dmpe = 1,2bis(dimethylphosphino)ethane, were prepared and characterized by UV-vis, IR and 1H NMR spectroscopy as well as
single crystal x-ray crystallography. At 300 K, χMT = 0.79 and 1.34 cm 3·K/mol for 1 and 2, respectively; the values
decreases to 0.17 and 0.47 cm 3·K/mol at 2 K. This These data indicate 1 and 2 have different excited state contributions
to the magnetic ground states. We believe that the unusual coordination environment around 2 gives rise to this
difference. The synthesis, magnetic properties and reactivity studies, specifically stabilization of the coordination
environment and reduction to U(III), will be presented.
(1) Kindra, D. R.; Evans, W. J. Chem. Rev. 2014, 114, 8865.
INOR 321
Optimization of rare earth element chromatography
Hans-Kristian Knutson, [email protected], Anders Holmqvist, Bernt Nilsson. Chemical
Engineering, Lund University, Lund, Sweden
Separating individual rare earth elements from a complex mixture with several elements is difficult and this is emphasized
for the middle elements: Samarium, Europium and Gadolinium. In this study we have conducted experiments with the
main focus to optimize the productivity rate, subject to a purity requirement of 99%, for each element. This was
accomplished through overloaded one-step ion-exchange high-performance liquid chromatography with an bis (2ethylhexyl) phosphoric acid impregnated column and nitric acid as eluent. An inductively coupled plasma mass
spectrometry unit was used for post column element detection.
The experimental data from the productivity rate optimization was utilized for calibrating a mathematical model of the
chromatography process. The calibrated model was employed to investigate a multiobjective optimization strategy with
respect to maximizing the productivity, yield and pool concentration.
INOR 322
Stability and cation exchange dynamics of γ-irradiated actinyl peroxide nanocapsules
Travis A. Olds1,2, [email protected], Benjamin J. Moeller1, Peter C. Burns1,2. (1) Univ of Notre Dame, Notre Dame, Indiana,
United States (2) Civil & Environmental Engineering and Earth Sciences, University of Notre Dame, South Bend, Indiana,
United States
Nanomaterials often exhibit novel and uniquely useful physical and chemical properties not observed in their larger, bulk
counterparts. The sheet-structured uranyl peroxide mineral studtite comprises one of the common ‘bulk’ (sensu lato)
alteration phases of used nuclear fuel, due to the radiolysis of water it is in contact with.1 Under such intense fields of
ionizing radiation, studtite is comparatively more susceptible to alteration with respect to other uranyl minerals; full
amorphization is rapid after absorbing 7.3 x 106 Gy from the TEM electron beam.2 However, when a similar uranyl
peroxide sheet topology is instead assembled into the spherical nanocapsule U 60 (Figure 1), its rigidity, capsulelike form,
and crystallinity are preserved in the solid state and as discrete macroanions in solution after receiving comparable doses
of γ-radiation (in excess of 5.3 x 106 Gy). A combination of ESI-MS, Raman spectroscopy, ammonia-gas sensing
electrode measurements, 7Li NMR, and pinhole SAXS suggest that fragmentation of the nanocapsules subsequent to
exposure may be dominated by cation exchange processes. Substitution of radiolytically produced ammonium with lithium
leads to minor size and spectroscopic variations that give insight into the mechanism of fragmentation. Coordinatingcation dynamicity heavily influences nanocapsule stability in an induced irradiation environment. The high surface to
volume ratio of the hollow nanocapsule and open ring topology, in relation to bulk studtite, allows the rapid and facile
transfer of radiolytic species and some encapsulated cations—significantly enhancing its radiation stability. Basic
correlations between the size and topology of a nanocapsule and its stability in gamma radiation are compared using the
smaller U24-Li and U24-K.
References:
[1] Armstrong, C. R., et al. PNAS, 2012,109, 1874-1877. [2] Rey, A., et al. Am. Mineral. 2009, 94, 229-235.
Figure 1. The nanocapsule U60.
INOR 323
Methylcyclopentadienide as a supporting ligand for a reduced dinitrogen complex of yttrium
David H. Woen1, [email protected], Joseph W. Ziller2, William J. Evans3. (1) Inorganic
Chemistry, University of California, Irvine, Irvine, California, United States (2) Univ of
California, Irvine, California, United States (3) Dept of Chemistry, University of California Irvine, Irvine, California, United
States
The reduction of dinitrogen using rare earth complexes has been studied extensively since the discovery of
[(C5Me5)2Sm]2(μ-η2:η2-N2), which displayed the first example of a planar M2(μ-η2:η2-N2) core with any metal. Although
many examples of this structure have subsequently been identified in the literature, the number of ancillary ligands that
support this four atom planar core is small. Most of the examples involve either (C 5Me5)1−, as in the first example, or
[N(SiMe3)2]1− and (C5Me4H)1− in the complexes {[(Me3Si)2N]2(THF)Ln}2(μ-η2:η2-N2) and [(C5Me4H)2(THF)Ln]2(μ-η2:η2-N2)
(Ln = yttrium and lanthanides), respectively. The isolated examples, {[C5H3(SiMe3)2]2Dy}2(μ-η2:η2N2), [(C5H2tBu3)2Nd]2(μ-η2:η2-N2), and [(ArO)2(THF)2Ln]2(μ-η2:η2-N2) (OAr = OC6H3tBu2-2,6 ; Ln = Dy, Nd) are also known.
Recently, in connection with the discovery of new Ln2+ ions in complexes such as [(18-crown-6)K][Cp¢3Ln] (Cp¢ =
C5H4SiMe3), a reduced dinitrogen complex supported by the Cp¢ ligand was discovered, [Cp¢ 2(THF)Y]2(μ-η2:η2-N2). In
efforts to widen the number of simple ancillary ligands that support Ln 2N2 cores, reduction reactions with Cp3Y(THF) (Cp =
C5H5) and CpMe3Y(THF) (CpMe = C5H4Me) have been studied. The EPR data of the products obtained under Ar that
support formation of Y2+ will be reported as well as the reactions under N2 which have led to the isolation of a reduced
dinitrogen complex with the simple CpMe ligand, [CpMe2(THF)Y]2(μ-η2:η2-N2).
INOR 324
Synthesis and f-element coordination of phosphine oxide decorated polypyridine ligand
Jeremy Dehaudt3, [email protected], Diane A. Dickie2, Benjamin P. Hay4,
Robert T. Paine1. (1) Chemistry, University of New Mexico, Albuquerque, New Mexico,
United States (3) Department of Chemistry and Chemical Biology, University of New
Mexico, Albuquerque, New Mexico, United States (4) Department of Chemistry,
Supramolecular Design Institute, Oak Ridge, Tennessee, United States
Over the past years we have designed in our group pyridine and pyridine N-oxide ligands decorated with phosphine oxide
[1] (1), amide [2], phosphonic acid [3] and dithiophosphoryl moieties [4]. These multidentate molecules have been found
to be strong and selective chelating ligands for trivalent lanthanide and actinide cations [5]. We have now extended this
work to the synthesis of new phosphine oxide functionalized polynitrogen ligands exhibiting higher denticity potential, such
as bipyridine derivatives 2 and 3. We also focused our attention on more preorganized structures such as phenanthroline
4 and acridines 5 and 6, that can increase the affinity for target cations by lowering the complexation energetic cost.
The synthesized ligands and their coordination chemistry with lanthanide cations have been studied by X ray
crystallography and computational molecular modeling.
[1] S. Pailloux, C. Edicome Shirima, A. D. Ray, E. N. Duesler, R. T. Paine, J. R. Klaehn, M. E. McIllwain, B. P. Hay, Inorg.
Chem., 2009, 48, 3104-3113
[2] S. Pailloux I. Binyamin, L. M. Deck, B. P. Hay, E. N. Duesler, L. N. Zakharov, W. Scott Kassel, A. L. Rheingold, R. T.
Paine, Polyhedron, 2009, 28, 3979-3984
[3] X-M. Gan, I. Binyamin, S. Pailloux, E. N. Duesler, Dalton trans., 2006, 3912-3917
[4] X-M. Gan, E. N. Duesler, S. Parveen, R. T. Paine, Dalton trans., 2003, 4704-4708
[5] D. Rosario-Amorin, S. Ouizem, D. A. Dickie, Y. Wen, R.T. Paine, J. Gao, J. K. Grey, A. de Bettencourt-Dias, B. P, Hay, L.
H. Delmau, Inorg. Chem., 2013,52, 3063-3083
INOR 325
Dinitrogen reduction and isoprene polymerization via photochemical activation of bis(cyclopentadienyl) rare
earth allyl complexes
Casey W. Johnson1, [email protected], Megan Fieser2, Joseph W. Ziller3, William J.
Evans4. (1) Chemistry, University of California, Irvine, Irvine, California, United States
(2) University of California, Irvine, Irvine, California, United States (3) Univ of California,
Irvine, California, United States (4) Dept of Chemistry, University of California Irvine, Irvine, California, United States
Recently, an unusual case of rare-earth based photochemistry was observed with the mixed-ligand tris(cyclopentadienyl)
complexes, (C5Me5)3-x(C5Me4H)xLn (Ln = Y, Dy, Lu; x = 1, 2): it was found that these complexes could be photoactivated
to reduce N2 to (N2)2-. Density functional theory analysis indicated that this powerful photo-reduction arose from excitation
of an electron in an orbital localized on a (η3-C5Me4H)1- ligand that has two ring carbons and one methyl group oriented
towards the metal. To further understand the requirements for this ligand-based excitation, irradiation of the
bis(cyclopentadienyl) rare earth allyl complexes (C5Me5)2Ln(C3H5), 1 (Ln = Y, La, Gd, Dy, Tb, Lu) was explored.
Dinitrogen can also be reduced by photochemical activation of 1 to form [(C5Me5)2Ln]2(µ-η2: η2-N2). This is the most facile
synthesis of these reduced dinitrogen complexes observed to date. Photolysis of 1 in isoprene also provides a rare photopolymerization of isoprene and yields a mixture of isoprene polymers. In the presence of elemental sulfur (S8), photolysis
of 1 leads to formation of S2- complexes. The 2-methylallyl complexes, (C5Me5)2Y[CH2C(Me)CH2], 2, also undergo
photoactivation and form reduced dinitrogen products. These results will be presented, as well as comparisons of the
photochemical activity of 1 and 2, their UV-Vis spectra, and analysis of the organic byproducts of these reactions.
INOR 326
Tuning of structural dimensionality in lanthanide cyanometallates
Richard Sykora2, [email protected], Frankie D. White1, Lam Pham1, KangRui Xaing1, Anthony T. Thames1,
Jeff Hendrich1, Jared D. Taylor1. (1) University of
South Alabama, Mobile, Alabama, United States (2) Chem 223, University of South Alabama, Mobile, Alabama, United
States
Aurophilic, argentophilic, and platinophilic interactions are gaining increasing attention as prominent examples of a more
general phenomenon of metallophilicity, and recognized as a major force determining structural dimensionality and
properties. The cyanometallate anions [M(CN)2]− (M = Ag, Au) and [M(CN)4]2− (M = Pt, Pd) have been extensively studied
as building blocks to form coordination polymers through cyanide bridging in monometallic systems, and in heterometallic
systems with transition metals, main group elements, and rare earth species. Our present studies have illustrated that
there is a strong possibility of a rich structural chemistry among the lanthanide cyanometallates. By varying factors such
as reaction solvent, stoichiometry, and choice of ancillary ligands, a large class of compounds with varying structural
properties can be prepared. For example, lanthanide cyanometallates structure types containing zero-, one-, two-, and
three-dimensional structures are all possible. This presentation will focus on the structural trends in this class of novel
materials.
INOR 327
Dicyanoaurate and tetracyanoplatinate compounds as potential chemical sensors for volatile organic compounds
Frankie D. White1, [email protected], Richard Sykora2, Jeff
Hendrich3. (1) University of South Alabama, Mobile, Alabama, United States (2) Chem
223, University of South Alabama, Mobile, Alabama, United States (3) Chemistry, University of South Alabama, Mobile,
Alabama, United States
Dicyanoaurates (DCAs) and tetracyanoplatinates (TCPs) have interesting properties that make them attractive for many
applications. One such property is that these compounds contain tunable metal-metal (M∙∙∙M) bond distances. Gold and
platinum compounds have been known to display a phenomenon called vapochromism due to changes in M∙∙∙M bond
distances. Vapochromic materials exhibit changes in spectroscopic properties upon exposure to volatile organic
compounds (VOCs). Utilizing
DCAs and TCPs tunable M∙∙∙M bond distances could be beneficial in developing chemical sensors for detecting different
VOCs in industrial and environmental settings. The synthesis and vapochromic behaviors of select DCA and TCP
compounds with certain alkali, first row transition, and lanthanide metals will be presented.
INOR 328
Emissive electropolymerizable lanthanide complexes
Margaret V. Tran, [email protected], Daniel J. Strohecker, Matthew T. Raiford,
Bradley J. Holliday. Chemistry, The University of Texas at Austin, Austin, Texas, United States
Complexes of the lanthanide ions display sharp luminescent emission emanating from ff transitions on the metal center.
The sharpness of the emission peaks originates from the shielding of the 4f orbitals by the 5s and 5p shells and leads to
high color purity of emission without the need to filter the emission. These materials have garnered interest for many
applications including incorporation into light-emitting diodes. For this application, the emissive lanthanide materials are
attractive because theoretical emissive quantum yields of 100% are possible. Very high quantum yields are possible due
to the ability of the lanthanide ions to harvest energy from both the singlet and triplet excited states of the donor ligand for
light emission. Unfortunately, direct excitation of the lanthanide emission is spin and parity forbidden, which necessitates
the use of an antenna ligand to absorb light and transfer energy to the metal ion from ligand-centered excited states. Ideal
antenna ligands utilize a conjugated organic backbone with multiple coordination sites to effectively bind the Ln(III) ion in
addition to having the appropriate donor excited-state energy level to sensitive metal-centered emission. Present work in
our research group has focused on developing a new class of bis(isoxazolyl)pyridine ligands. In some cases these ligands
are appended with electropolymerizable thiophene moieties to allow the lanthanide complexes to be incorporated into
conducting metallopolymer materials. The design, synthesis, characterization and photophysical properties of these
ligands and the corresponding lanthanide complexes will be presented.
INOR 329
Lanthanide-organic frameworks as asymmetric heterogeneous catalysts
Daniel T. de Lill, [email protected]. Chem Biochem Physical Sciences PS 110, Florida
Atlantic University, Boca Raton, Florida, United States
Chiral metal-organic frameworks (MOFs) have been studied for the past decade for their use in enantiomeric separations
and asymmetric catalysis, but most of these materials are assembled using transition metal ions. Chrial MOFs
constructed from lanthanide ions (lanthanide-organic frameworks, LOFs) are less common, and those that have been
reported have been utilized only for enantiomeric separations. Progress towards the evaluation of LOFs with homochiral
pores as asymmetric catalysts will be presented.
INOR 330
Synthesis and structural characterization of Y 2+ and Gd2+ in heteroleptic tris(cyclopentadienyl) rare earth
complexes
Chad T. Palumbo2, [email protected], Joseph W. Ziller1, William J. Evans3. (1) Univ of California, Irvine, California,
United States (2) University of California - Irvine, Irvine,
California, United States (3) Dept of Chemistry, University of California Irvine, Irvine, California, United States
Although recent studies have demonstrated that all the lanthanides (except Pm) can be isolated in the +2 oxidation state
as crystalline molecular compounds of the formula [K(2.2.2-cryptand)][Cp’3Ln], (Cp’ = C5H4SiMe3; Ln = Y, lanthanides),
there are still many questions about the factors that affect the stability of divalent lanthanide ions in molecular compounds.
For the larger metals, La and Ce, Lappert has shown that complexes with metals in the +2 oxidation state can be isolated
using the more sterically encumbering ligand [C5H3(SiMe3)2]1- in molecular compounds of the formula [K(18crown6)(Et2O)x][Cp”3Ln], (x = 1, 2; Cp” = C5H3(SiMe3)2). However, for the smaller metal Y, the reduction product of Cp”3Y with
potassium decomposes rapidly in solution perhaps because the (Cp” 3)3- ligand system is too large for the smaller rare
earths. To determine if a mixed ligand system could provide stable Ln 2+ complexes, the effects on stability of replacing
one of the Cp” ligands with Cp (C5H5) or CpMe (C5H4Me) in Cp”3Y and Cp”3Gd have been investigated. X-ray, EPR and
UV-Vis data will be presented describing the formation and isolation of just the second crystallographically characterizable
examples of Gd and Y in the +2 oxidation state using these heteroleptic tris(cyclopentadienyl) coordination environments.
Comparisons with [K(2.2.2cryptand)][Cp’3Ln] will be made.
INOR 331
Pt-Au and Pd-Au bimetallic heterostructures using mask assisted seeded growth
Cameron Crane, [email protected], Jingyi Chen. Chemistry and Biochemistry, CHEM
119, University of Arkansas, Fayetteville, Arkansas, United States
The application of multifunctional nanomaterials to complex problems in biomedicine and alternative energy is tempered
by the challenges arising in the design of synthetic approaches to produce segmented surfaces –especially in the size
range of ten nanometers. We expand upon a strategy that utilizes partially masked seed particles, restricting noble metal
growth to a single side of the seed particles, to produce asymmetric segmented nanoparticles. This seeded-growth
strategy was demonstrated with silica as a mask, directing the growth of Pt and Pd, yielding segmented Pt-Au, PdAu, and
Pt-Pd-Au particles. Recent progress has expanded to include non-noble metal components, extending the impact of the
mask assisted seeded growth approach.
INOR 332
Effective regulation of post-preparative cation exchange reactions in PbS quantum dots
Badri P. Mainali, [email protected], Paul G. Van Patten. Chemistry, Middle
Tennessee State University, Murfreesboro, Tennessee, United States
Cation exchange has become an interesting and useful process for structural and compositional modification of compound
semiconductor nanocrystals, or quantum dots (QDs). In principal, this process could be used for heavy doping, alloying,
and/or heterostructure formation, if the extent and distribution of exchanged cations can be controlled. In the present
work, we examine the factors that control the exchange of Pb cations with Cd cations in PbS QDs. The effects of
temperature, concentration, and composition of the ligand shell on the kinetics and extent of the exchange are
investigated via electronic spectroscopy, atomic absorption spectrometry, and transmission electron microscopy. Whereas
temperature can be used to increase the rate and extent of Pb exchange, very high temperatures (>150 °C) also degrade
the QDs and can lead to dissolution of the particles. Exchanging the ligands on the surface can also promote the
exchange reaction, allowing use of lower reaction temperatures. Using these strategies, we have successfully
demonstrated the production of thick, robust CdS shells surrounding PbS QDs. These thick shells can enhance the optical
properties, and can modify the carrier distribution within the QDs and allow partial charge carrier separation within the
particle.
INOR 333
Incorporation of transition metal cations into PbS QDs via cation exchange
Wayne Tilluck, [email protected], Amanda D. Evans, Jason K. Gurchiek, Clay
M. Mings, Alexander L. Morris, Paul G. Van Patten. Chemistry, Middle Tennessee State University, Murfreesboro,
Tennessee, United States
Cation exchange provides a method to synthesize altered semiconductor quantum dots (QDs) that can otherwise be
difficult to produce. The introduction of transition metal ions to a system offers possibilities for manipulation of the
structural, optical and magnetic properties of the QDs. With previous success in cation exchange with PbS QDs, we here
report the reactions of several transition metal cations, including cadmium, nickel, silver, iron, manganese, copper,
chromium, zinc and cobalt, under various reaction conditions. Ligand exchange, temperature, concentration, reaction time
and solvents are examined as important reaction parameters. Optical and structural properties are studied via electronic
spectroscopy, elemental analysis, and TEM imaging. Where appropriate, magnetic susceptibility results are also reported
as a function of composition and metal distribution within the QDs.
INOR 334
Supersaturation-precipitation strategies to colloidal hybrid nanoparticles
Carlos G. Read, [email protected], Adam J. Biacchi, Raymond E.
Schaak. Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, United States
Colloidal hybrid nanoparticles contain multiple inorganic domains that are joined together through strong solid–solid
interfaces, which often can lead to multifunctionality and to the emergence of new or enhanced properties. Manipulating
the interfaces of such materials in a controllable fashion could open the door to the synthesis of a wide range of new
functional structures in which specific physical and chemical properties are engineered from the bottom-up. Traditionally,
colloidal hybrid nanoparticles have been synthesized using heterogeneous seeded nucleation of one nanoparticle onto
the surface of another. However, to expand the materials diversity and the potential range of applications of such
systems, alternative routes to heterogeneous seeded nucleation are needed. Here we highlight our recent efforts in the
development of new methods for the synthesis of multicomponent hybrid nanoparticles comprised of plasmonic, catalytic,
semiconducting and magnetic domains, through the use of solution–liquid–solid and related supersaturation-precipitation
strategies. This alternate route to colloidal hybrid nanoparticles has facilitated the integration of previously inaccessible
group IV elements into these structures, and represents a useful addition to the total synthesis toolbox for the construction
high-order colloidal hybrid nanoparticles.
INOR 335
Synthesis of acetamide from acetonitrile hydrolysis using EEW catalyzed with metal nanoparticles
Elseddik Abdelkader1, [email protected], Steven W. Buckner2, Paul A.
Jelliss3. (1) Chemistry, Saint Louis University, Saint Louis, Missouri, United States (2)
Saint Louis University, Dept of Chem, Saint Louis, Missouri, United States (3) St Louis Univ, Saint Louis, Missouri, United
States
Abstract: Hydrolysis of acetonitrile to acetamide was achieved using a novel EEW technique with zinc as a catalyst. EEW
is very cost effective technique with the acetamide crystals physically separated from the zinc nanoparticles (ZNPs) after
the
reaction. The capacitance and charging voltage for the explosion are 96 μF and ~44.4kV, respectively. Other transition
metals as (Fe, Ti, Nb..) as well as s and p-block metals (Mg and Al) were used successfully to catalyze the hydration to
acetamide. Other nitriles such as acrylonitrile, propionitrile and benzonitrile were used to study the generalization of the
hydration, however only acetonitrile was effectively converted to acetamide. Generally, transition metal salts accompanied
by organic compounds were used to catalyze hydration to amides. However, this is the first report of this type of hydration
reaction using EEW without organic catalyst. Also, an investigation was made to determine if the NPs or metal atoms/ions
were the main catalyst to produce amides. During the synthesis, metal cyanide nanoparticles were also produced with
zinc and copper wires with core size of order 20nm. Transmission electron microscopy shows the spherical particles with
the metallic core embedded in a polymer matrix. Powder X-ray diffraction was used to confirm the identity of the metallic
NPs, cyanide NPs and the produced acetamide. ATR-IR was used to characterize the capping agent as well as the
synthesized acetamide.
INOR 336
Growth kinetics of zinc oxide quantum dots
Brandon Colon, [email protected], Hailey Egido-Betancourt, [email protected], Cynthia P. Mccord,
[email protected], Pamela P.
Vaughan, Alan K. Schrock, Karen S. Molek. Chemistry, University of West Florida, Pensacola, Florida, United States
Zinc Oxide quantum dots (QDs) were synthesized using a “seed” method, which produces a dispersion of highly modified
ZnO particles. Hydroxide solutions of LiOH, NaOH, KOH and CsOH were reacted with zinc acetate in concentrations of
0.4-1.0 mmol and 0.05-0.25mmol, respectively. The particles were characterized using UV-Vis and Fluorescence
spectroscopy. Varying solution concentrations produced QDs ranging in size as shown with fluorescence emissions
ranging from orange to purple. Higher LiOH and zinc concentrations produced small QDs with emissions around 400-500
nm whereas similar concentrations of NaOH and KOH yielded QDs with yellow, orange emissions around 600-650nm.
Transmission electron microscopy confirmed QD particle sizes.
INOR 337
Effect of synthetic levers on phosphorus incorporation in nickel phosphide nanoparticles: Ni5P4 and NiP2
Da Li, [email protected], Stephanie Brock. Chemistry, Wayne State University, Detroit, Michigan, United States
The unique redox and catalytic properties of nickel phosphides depend on their size and shape (in the nano regime) as
well as their composition. On the metal-rich side, Ni2P shows potential as powerful hydrodesulfurization and hydrogen
evolution catalysts; while on the more phosphorous-rich side, Ni5P4 and NiP2 are promising candidates for lithium ion
battery electrode materials. Arrested precipitation routes have proven to be effective for formation of metal-rich nickel
phosphide phases, and the ability to control particle size and phase (Ni 2P vs. Ni12P5) has been demonstrated.1 In this
study, a phase-control strategy enabling the synthesis of more phosphorus-rich nickel phosphides (Ni5P4 or NiP2) will be
described. The role of the key synthetic levers on the phase-purity and morphology of the product, including the Ni
precursor, the oleylamine (OAm) and trioctylphosphine (TOP) concentrations, and the intermediate Ni template formation
step, will be discussed in light of a comprehensive synthetic scheme to control phosphorus incorporation in nickel
phosphides.
1. Muthuswamy, E.; Savithra G.H.L.; Brock S.L. Synthetic Levers Enabling Independent Control of Phase, Size, and
Morphology in Nickel Phosphide Nanoparticles. ACS Nano, 2011. 5(3): p. 2402-2411.
INOR 338
Electrophoretic deposition of gold nanospheres for explosives detection
Keira Roberts1, [email protected], Yong J. Han2, Tammy Y. Olson2. (1) Lewis and
Clark College, Portland, Oregon, United States (2) Physical and Life Sciences
Directorate, Lawrence Livermore National Lab, Livermore, California, United States
The goal of this research is to utilize advances in nanotechnology to address major issues in national security. Our
research is focused on gold nanoparticles with the goal of designing inexpensive, discreet, sensitive detectors for
explosives. Gold nanoparticles are useful sensors because of their optical properties. A facile synthesis was optimized to
reliably produce monodisperse nanoparticles with tunable sizes. These nanoparticles, capped with citrate and
polyvinylpyrrolidone, were stable to resuspension in ethanol. Electrophoretic deposition was used to deposit the
nanoparticles onto boron-doped silicon wafers. The surface of the wafers was coated with poly (methyl methacrylate)
(PMMA) and electron-beam lithography was used to irradiate patterned areas where deposition was desired. The PMMA
coating dissolved in the irradiated areas during development, which exposed selected areas of the silicon wafer for
deposition. Gold nanoparticles were successfully deposited inside of the patterns with minimal deposition on the PMMA
coating. Patterned deposition areas ranged several microns to 500 nm in diameter. The controlled deposition of AuNPs
shown in this research marks a step forward in the quest to easily control the formation and functionalization of nanoscale
materials. Future work on this project will control the deposition of single particles as well as the size-selective deposition
of nanoparticles.
INOR 339
Formation of Ag nanoclusters via the direct dissolution of bulk Ag
Jessica R. Changstrom, [email protected], Christopher M. Sorensen. Kansas State
University, Manhattan, Kansas, United States
We have developed a process by which nanoclusters are formed by the direct dissolution of bulk metal. Previously, this
method has been used to make Ag, CdS, CdSe nanoclusters in a microwave reactor. In this work, we have attempted to
extend this method so that the process can be performed at ambient pressure and at the solvent boiling point.
Specifically, 250 μm silver powder was refluxed with either dodecylamine or dodecanethiol in tert-butyltoluene for 24
hours. The resulting yellow solution does not exhibit a plasmon, which would be indicative of nanoparticles, but does show
high absorbances below 360 nm, suggesting the presence of silver nanoclusters.
INOR 340
Ion exchange and protection-deprotection chemistry in the total synthesis of colloidal hybrid nanoparticles
James M. Hodges1, [email protected], Adam J. Biacchi3, Raymond E.
Schaak2. (1) Chemistry, Pennsylvania State University, State College, Pennsylvania,
United States (2) Pennsylvania State University, University Park, Pennsylvania, United
States (3) Nanoelectronics Group, National Institute of Standards and Technology, Rockville, Maryland, United States
Colloidal hybrid nanoparticles are an important class of materials that integrate multiple nanocrystals into a single system,
which can have properties not found in the individual components. Seeded-growth methods, where preformed
nanocrystals are used as seeds for growing additional domains in subsequent reactions, is often the preferred synthetic
method due to greater control over hybrid nanoparticle morphology. These step-wise reaction sequences can be thought
of as being analogous to molecular total syntheses, and provide a rational framework for producing sophisticated
nanoparticle architectures. This work focuses on developing this methodology, specifically using protection-deprotection
and chemical transformation motifs for attaining synthetically challenging hybrid nanoparticle targets. We expect these
techniques to allow access to a variety of new hybrid nanomaterials that will be candidates for applications that include
solar energy harvesting and heterogeneous catalysis.
INOR 341
Polyaniline/laponite/gold coordination polymer nanoassemblies for solar applications
Phaik Suan Quah, [email protected], Michael E. Hagerman. Union College,
Schenectady, New York, United States
We are exploring mechanochemical routes to fabricate solar heterojunction films based on
polyaniline/Laponite/coordination polymer nanoassemblies. Polyaniline in its emeraldine salt form serves as an electron
conductor while polythiophene serves as a hole conductor in these solar heterojunctions. Laponite clay nanoparticles are
used as a nanoscaffold to direct the self-assembly of the polymer networks and improve water processability of films. We
have employed dicyanoaurate coordination polymer (CP) networks to improve the polydispersity of CdSe semiconductor
nanocrystals and to optimize charge transport. The Au CP networks act as an intercalative backbone to link CdSe
nanoparticles with conductive polymer arrays. We have investigated various synthetic routes and film processing methods
and examined their effects on film quality and surface morphology in these tricontinuous polymer heterojunctions.
Scanning electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, and UV-visible spectroscopy
were used to verify syntheses and to study the heterointerfaces that control self-assembly, exciton formation, charge
separation, charge transport, and photoefficiency.
INOR 342
New routes to clean water: Laponite/copper oxide nanomaterials for bacterial remediation
Alexander J. Cavert1, [email protected], Michael E. Hagerman2. (1) Chemistry,
Union College, Schenectady, New York, United States (2) Union College, Schenectady, New York, United States
Copper oxide nanoparticles offer promising applications in water filtration, photocatalysis, and gas sensing owing to their
highly tunable nanostructure and reactivity. Controlling the specific micro- and nanostructure of these particles can
promote enhanced chemical reactivity and surface energy that also make them promising materials for antimicrobial
applications. To this end we have synthesized copper(I) oxide nanostructures with varied morphologies consisting of
octahedra, cubes, spheres and hexapods, and studied the effect of shape on their ability to remediate bacteria in
contaminated water. The copper oxide nanoparticles were incorporated within Laponite RD nanoscaffolds through water
based self-assembly to enhance water processability, polydispersity, and filter stability. Water samples contaminated with
E. coli bacteria were exposed to Laponite/Cu(I) oxide films for varying time periods and were then cultured and tested for
colony forming units. Morphological, compositional, and crystallinity studies of the nanocomposites were performed using
powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. These structureproperty studies offer important insight for water filter design strategies to utilize copper oxide nanomaterials for
antimicrobial and clean water applications.
INOR 343
Synthesis and characterization of titanium oxide nanopowders
Heather Chenoweth, [email protected], Lauren F. Barnes, [email protected], Christopher J. Van Leeuwen,
Karl A. Reyes, Christen K. Butterfield. Chemistry, University of West Florida, Pensacola, Florida, United States
A variation of excess hydrolysis synthesis was used to synthesize titanium oxide nanoparticles using Titanium
Tetraisoproproxide at varied pH values. The nanoparticles were left in solution from times varying between two hours and
twelve months. The synthesized nanopowders were then heated to temperatures between 80° C and 750° C varying
between one and two hour time increments at each temperature. Differential Scanning Calorimetry (DSC) was used to
further refine the heating ranges to get a more accurate range at which the nanopowders changed phase. Titanium oxide
nanoparticles left in solution for over twelve months were characterized without heating. After being synthesized, each of
the nanopowder samples were characterized according to their size, composition and phase, and absorbance properties
using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and UV-Vis Spectroscopy, respectively. The
spectra and diffraction patterns were used to determine the temperature required to induce a phase change from the
amorphous to anatase structure and anatase to rutile structures. The nanoparticles left in solution were characterized to
determine if they existed as a single crystalline phase. The resulting spectra were compared to literature spectra to ensure
that pure samples of each species of nanopowder were obtained.
INOR 344
Synthesis and characterization of spirocyclic monoalkylated organosilicon complexes of 1-hydroxy-2-pyridinone
James G. Koch1, [email protected], William W. Brennessel2, Bradley M. Kraft1. (1)
Chemistry, St. John Fisher College, Fairport, New York, United States (2) Chemistry,
University of Rochester, Rochester, New York, United States
A series of monoalkylated organosilicon compounds of the form RSi(OPO) 2Cl (OPO = 1-oxo-2-pyridinone; R = Me, tBu,
Ph, CH2Ph, p-tolyl) was synthesized and characterized by 1H , 13C, and 29Si NMR spectroscopy, and elemental analysis.
X-ray crystallographic analyses revealed two different coordination environments in the series, with 5coordinate
complexes formed with R = Me, tBu, and 6-coordinate complexes formed
with R = Ph, CH2Ph, p-tolyl. Dynamic behavior was observed in each of the five complexes using variable-temperature
NMR spectroscopy.
INOR 345
Synthesis and characterization of five-coordinate aluminum complexes that polymerize ε-caprolactone
Angela M. Longo, [email protected], Joseph M. Fritsch. Chemistry, Pepperdine University, Newbury Park,
California, United States
Aluminum complexes supported by ketoiminates bearing electron-donating groups were prepared through reaction with
tris-(2,6-dimethylphenoxy) aluminum under an inert atmosphere at room temperature. The water-sensitive complexes
were isolated by filtration in moderate yields and dried in vacuo. The complexes were characterized with 1H and 13C NMR
and absorbance spectroscopy, and x-ray crystallography. The aluminum complexes included a tridentate ketoiminate with
a pendant quinolyl moiety and two phenoxides. The complexes were assessed for their ring opening polymerization
activity with ϵ-caprolactone and were shown to be highly efficient in producing poly-caprolactone at elevated temperature.
INOR 346
Polymerization of ε-caprolactone by aluminum alkoxide complexes supported by tridentate ketoiminates bearing
electron-withdrawing groups
Alexandria M. McCollum1, [email protected], Arnold L.
Rheingold2, Joseph M. Fritsch1. (1) Chemistry, Pepperdine University, Malibu,
California, United States (2) Chemistry, University of California, San Diego, La Jolla, California, United States
A series of five-coordinate aluminum complexes were prepared from ketoimines bearing electron-withdrawing groups and
tris-(2,6-dimethylphenoxy) aluminum. The structure of the aluminum reagent is in its dimeric form ([Al(OR)3]2) with two
bridging alkoxides. In contrast to previous studies using CH2Cl2 as the reaction solvent which yielded the asymmetric
splitting of the aluminum dimer, this study utilized THF as the reaction solvent which lead to symmetric dimer splitting. As
a result, five-coordinate aluminum complexes including a tridentate ketoiminate and two alkoxides were prepared and
isolated. The complexes were characterized with 1H, 13C, and 19F NMR and x-ray crystallography and were shown to be a
highly effective ε-caprolactone polymerization catalysts.
INOR 347
L-Lactide and ε-caprolactone ring opening polymerization by binary catalysts systems that include bis-ligated
magnesium complexes
Reile M. Slattery1, [email protected], Arnold L. Rheingold2, Joseph M. Fritsch1. (1) Chemistry, Pepperdine
University, Newbury Park, California, United States
(2) Chemistry, University of California, San Diego, La Jolla, California, United States
A series of bis-ligated magnesium complexes supported by tridentate ketoiminates containing electron-donating and
electron-withdrawing groups were prepared. The complexes were characterized with 1H, 13C, and 19F NMR, absorbance
spectroscopy, and x-ray crystallography. The complexes were assessed for their ring opening polymerization activity with
L-lactide (L-lac) and ε-caprolactone (eCL) in binary catalyst systems with 4-fluorophenol at 100 °C. The magnesium
complexes supported by ketoiminates bearing electron-donating groups yielded greater percentage conversions from
monomers to polymers than those containing electron-withdrawing groups for both L-lac and eCL. The magnesium
complexes were more efficient at polymerizing L-lac than eCL, and di-block copolymers of PCL-PLA were produced by
the sequential polymerization of eCL followed by L-lac.
INOR 348
Polymerization of lactide by aluminum ion pairs studied with
27
Al NMR
Logan A. Schmitz1, [email protected], Arnold L. Rheingold3, David B. Green2, Joseph M. Fritsch1. (1)
Chemistry, Pepperdine University, Newbury Park,
California, United States (2) Natural Science Division, Pepperdine University, Malibu,
California, United States (3) Chemistry, University of California, San Diego, La Jolla, California, United States
Aluminum ion pair complexes containing an octahedral bis-ligated aluminum cation and a tetrahedral tetraphenoxide
aluminate anion have been shown to polymerize lactide into poly-lactic acid (PLA). The structure of the active catalyst was
investigated through the synthesis of aluminum complexes in different coordination environments were distinguishable by
27Al NMR (octahedral δ 23 ppm and tetrahedral δ 42 ppm). The bisligated octahedral cation with tetrachloro aluminate
(27Al NMR signals at δ 23 and 103 ppm) and lithium tetraphenoxide aluminate ( 27Al NMR signal at δ 46 ppm) were
prepared, studied with 27Al NMR, and their lactide polymerization activity assessed. Since neither fragment exhibited
polymerization characteristics similar to the original system, the ion pair complex was further studied with variable
temperature 27Al NMR.
INOR 349
Si-H and Ge-H bond activation by a platinum dimer
Lucas Matuszewski2, [email protected], Serge H. Schreiner1. (1)
Randolph Macon College, Ashland, Virginia, United States (2) Chemistry, RandolphMacon College, Ashland, Virginia,
United States
Polymers with heavier group 14 backbones are particularly useful semiconductors, photoconductors, photoresist
materials, and nonlinear optical materials due to sigma conjugation. While polysilanes have been studied extensively,
polygermanes are far less explored. The established method of polysilane and polygermane production is Wurtz-type
coupling using halosilanes and alkali metals. While this process produces high molecular weight chains, yields are
generally fairly poor. Recently transition metal catalysts have been used for the coupling of silanes and stannanes with
reasonable success, but transition metal catalysts for germane coupling are not as prevelant. In this study, the interaction
of a platinum dimer with phenylsilanes and phenylgermanes was investigated. Reaction times and stoichiometric ratios
were sytematically varied yielding a number of different products as determined by IR and multinuclear NMR
spectroscopy. Methodologies and proposed structures are herein presented.
INOR 350
Investigating the electronic coupling of quantum dots to crystal-bound thiols
Amadou M. Fall1, [email protected], Stephanie Castillo2, Nazharie K. Brandon3,
Michael J. Turo3, Andrew D. La Croix3, Janet E. Macdonald3. (1) Chemistry, Tennessee
State University, Nashville, Tennessee, United States (2) University of Central Florida,
Orlando, Florida, United States (3) Vanderbilt University, Nashville, Tennessee, United
States
Photocatalysis and photovoltaics exhibit an ever increasing importance in our search for renewable energies. Nanoscale
semiconductors, also known as quantum dots, are promising light absorbing materials in these applications. Traditional
colloidal synthetic methods, which are used to obtain monodisperse quantum dots leave the particles capped with long
chain ligands such as thiols. The Macdonald group has discovered a new binding mode for capping thiols which we call
"crystal-bound" where the thiols are coordinated into the crystal-lattice. We show that crystal-bound thiols have a
significant electronic effect on the band gap of CdSe when shelled with ZnS with a corona of crystal-bound ligand thiols.
This is seen through red shifts in absorbance and fluorescence. We also show that the crystal-bound thiols, when
compared to surfacebound thiols, improve charge transfer efficiencies in a photocatalytic reaction though the ZnS shell.
INOR 351
Synthesis and photovoltaic performances of di-acetylide platinum complexes in dye-sensitized solar cells
Travis Schuyler1, [email protected], Sébastien Gauthier2. (1) Chemistry, Northern
Kentucky University, Highland Heights, Kentucky, United States (2) Institut des
Sciences Chimiques, IUT Lannion, Université de Rennes 1 , Lannion, France
The increasing global demand in energy has triggered extensive research in the area of renewable energy sources, in
particular for solar energy. Recently, Dye-Sensitized Solar Cells (DSSCs) have been investigated as alternatives to
silicon-based solar cells. Our work has dealt with the development of novel dye molecules based on transition metal
complexes for potential applications in DSSCs. Here we present the synthesis, optical and electrochemical
characterization of five new di-acetylide platinum-based complexes 8a-e, comprising a pyranylidene ligand and functional
groups (i.e. phenyl, furan, bi- and tri-thiophene) of different natures and lengths as linkers separating the platinum unit
from the anchoring cyanoacetic group. The performances of these complexes in DSSCs were also studied. The D-π-M-πA combination resulted in dyes exhibiting an effective broadening of the light absorption spectrum, and consequently, in a
higher photocurrent production and a higher photoconversion efficiency (PCE). The photoconversion efficiency obtained
reaches 4.7 % for 8e (compound with the trithiophene segment), which is among the highest efficiencies reported for
platinum complexes in DSSCs.
D-p-M-p-A Structured Di-acetylide Platinum Complexes for Dye-Sensitized Solar Cells
INOR 352
New phase discovered in the Cu-Ge-Te system by high-temperature solid state reaction
Brea Hogan, [email protected], Jennifer A. Aitken. Duquesne University, Monroeville, Pennsylvania, United States
Copper chalcogenides have possible applications in thermoelectric technologies. Information regarding applications of
these materials are acquired from systematic and thorough assessment of the physicochemical properties. Hightemperature solid state reactions intended to prepare a quaternary telluride produced the intended compound as well as a
minute amount of large black cuboid crystals. Scanning electron microscopy coupled with energy dispersive spectroscopy
indicates that these crystals only contain Cu, Ge and Te in a ratio that is different from any known Cu-Ge-Te phase. X-ray
powder diffraction data of reactions to target this new material will be presented as well as optical diffuse reflectance
spectra.
INOR 353
Spectroelectrochemical determination of the Fe(III)/Fe(II) reduction potential in recombinant, cross-linked
hemoglobins
Rachel Bangle, [email protected], Claire J. Parker Siburt, R. Timothy Kreulen, Alvin L.
Crumbliss. Dept of Chem, Duke Univ, Durham, North Carolina, United States
Successful blood substitutes can potentially decrease the need for blood transfusions, making the process safer and
better able to meet future demand. Several types of molecules are being investigated as potential blood substitutes, and
one promising category is Hemoglobin-Based Oxygen Carriers (HBOC). Challenges in HBOC use arise from the behavior
of hemoglobin in an extracellular environment. Extracellular hemoglobin dissociates into dimers, undergoes oxidation and
ferric/ferryl cycling at their Fe centers, and damages membranes. In order to prevent this behavior, HBOCs are
engineered to prevent tetramer dissociation and increase the reduction potential to prevent oxidative damage. We use
spectroelectrochemistry to study the redox properties in native human hemoglobin (HbA 0) and engineered HBOCs. Here
we report our studies on Hb proteins with an intramolecular crosslink—a glycine covalently connecting the two alpha
subunits. We have investigated recombinant hemoglobin molecules that contain point mutations along with this glycine
crosslink. For example, rHb0.0 has only a Vα1M point mutation, while rHb0.1 has a Vα1M point mutation as well as a
glycine crosslink between the alpha subunits. rHb0.1 Providence contains a Kβ82D point mutation and a glycine crosslink.
rHb0.1 Presbyterian-Providence has both a
Kβ82D point mutation and a Nβ108K point mutation in addition to a glycine crosslink. Here we report the E 1/2 values and
electron transfer cooperativity for each of these proteins with a comparison to HbA0. In addition, our redox data are
discussed in relation to oxygen binding energetics and conformational states stability. These results are discussed in the
context of the MWC two-state (R/T) model and the possibilities for cross-linked Hbs to act as HBOCs without increasing
oxidative stress.
INOR 354
Green dechlorination via functional models of cyanocobalamin
Danielle Marquis1, [email protected], Katherine M. Van Heuvelen2. (1) Chemistry,
Harvey Mudd College, Claremont, California, United States (2) Department of
Chemistry, Harvey Mudd College, Claremont, California, United States
Carcinogenic groundwater pollutants such as tetrachloroethylene and trichloroethylene pose a public health risk. Vitamin
B12 (cyanocobalamin), being benign and operating at ambient temperatures, is a choice catalyst for dechlorinating these
pollutants into ethylene and acetylene. However, the method by which vitamin B12 dechlorinates tetrachloro- and
trichloroethylene is difficult to characterize. We are developing biomimetic catalysts that reproduce the dechlorination
activity of Viatmin B12. These catalysts employ cyclam ligands with appended functional groups to mimic the lower axial
dimethylbenzimidazol ligand found in cobalamin. These cyclam derivatives will be tested for their reactivity in
dechlorination and characterized by UV/vis spectroscopy.
INOR 355
Optical and thermal properties of lithium-containing thiostannate with potential nonlinear optical applications
Ashley Weiland1, [email protected], Jacilynn Brant1, Jian-Han Zhang1, Jennifer
A. Aitken2. (1) Duquesne University, Pittsburgh, Pennsylvania, United States (2) Duquesne Univ, Pittsburgh,
Pennsylvania, United States
Diamond-like semiconductors (DLSs) have applications in many areas such as photovoltaics and nonlinear optics. All
diamond-like semiconductors possess a noncentrosymmetric structure and are potential candidates for second harmonic
generation. Properties of these materials such as second-order nonlinearity in the IR can be tuned by employing a wide
range of predictable compositions. The majority of benchmark IR nonlinear optical (NLO) materials are DLSs. Compounds
of the formula Li2MSnS4 (where M = a divalent tetrahedrally coordinated metal) were prepared by high-temperature solidstate synthesis under vacuum. One of these compounds, Li2CdSnS4, was prepared as a phase-pure material as
determined by synchrotron X-ray powder diffraction and Rietveld refinement. Diffuse reflectance spectroscopy shows that
the compound exhibits a direct optical bandgap of 2.718(1) eV and an Urbach energy of 0.1994(6) eV. The compound is
relatively transparent (75-80%) from approximately 0.6 to 25 μm. Differential thermal analysis shows that the compound
melts at about 917 °C. The material is a promising candidate for nonlinear optical applications due to the wide bandgap,
broad range of optical transparency, relatively high thermal stability, and stability under ambient conditions.
INOR 356
Surface chemistry of gold nanoparticles in natural environments
Keira Roberts, Anne K. Bentley, [email protected]. Department of Chemistry, Lewis & Clark College, Portland, Oregon,
United States
Gold nanoparticles (Au NPs) are currently the subject of research efforts focused on developing highly sensitive sensors,
diagnostic techniques, and targeted drug therapies. As these NPs move from the research lab to large-scale production,
they will inevitably be released into the environment, and the eventual fate of these nanoparticles after release into the
environment is not well understood. The stability of gold nanoparticles capped with three typical ligands
(cetyltrimethylammonium bromide, polyvinylpyrrolidone, and bovine serum albumin) was examined in solutions that
mimicked natural environments: artificial seawater, locally gathered creek water, and a humic acid organic sediment
standard solution. Zeta potential measurements and UV/Vis spectroscopy were used to assess the stability of the NPs.
The zeta potential of all tested NPs moved closer to zero when resuspended in the creek water, indicating that the
capping agents had been replaced or overcoated by molecules in the water. The seawater caused all the particles’ zeta
potentials to move closer to zero, which may be an effect of the high ionic strength of the solution. The humic acid solution
caused a decrease in zeta potential of all tested NPs, likely due to the adsorption of carboxylic acids in the humic acid
onto the NP surfaces.
INOR 357
Investigation of novel polymorphic Li2-II-IV-S4 diamond-like semiconductors utilizing synchrotron X-ray powder
diffraction
Kasey P. Devlin1, [email protected], Kimberly Daley3, Meghann A. Moreau1, Jacilynn
Brant1, Jennifer A. Aitken2. (1) Duquesne University, Freeport, Pennsylvania, United
States (2) Duquesne Univ, Pittsburgh, Pennsylvania, United States (3) Duquesne
University, Pittsburgh, Pennsylvania, United States
Diamond-like semiconductors (DLSs) have structures derived from the cubic or hexagonal form of diamond. The I 2-II-IVVI4 DLS systems are of particular interest due to their tunable nature and possible technological applications in
photovoltaics, spintronics, and non-linear optics. Polymorphism may affect important physicochemical properties. Most
commonly, polymorphic DLS materials arise from differing modes of closest packing. In quaternary DLSs, polymorphism
may also be observed in structures that maintain the same anion packing, but differ in the cation ordering arrangement
within the tetrahedral holes. In this work, high-temperature solid-state synthesis in a Li2II-IV-VI4 system led to the
discovery of two polymorphs, crystallizing in the Li2CoSiO4 (Pna21) and wurtz-kesterite (Pn) structures. The two
polymorphs were analyzed using optical diffuse reflectance UV/Vis/NIR spectroscopy, single crystal X-ray diffraction, and
synchrotron X-ray powder diffraction together with Rietveld refinement. The National Science Foundation supports this
work under Grant No. DMR-1201729.
INOR 358
Precursor approach to probing host-guest binding of synthetic supercontainers
Alex Hammerstrom, [email protected], Fengrong Dai, Zhenqiang
Wang. Chemistry , University of South Dakota , Vermillion, South Dakota, United States
Container molecules exhibit a well-defined porous structure that potentially has a wide range of environmentally and
biologically-related applications including, encapsulation of otherwise unstable species, catalysis, storage and separation
of gases, and transportation of small molecules. We have recently shown that a new family of facedirected octahedral
metal-organic supercontainers (MOSCs) can be obtained from a variety of metal ions, sulfonylcalix[4]arenes and
tricarboxylate ligands via coordinationdriven assembling processes. The host-guest chemistry of these MOSCs in solution
has
been characterized using UV−Vis spectroscopy, which shows unambiguous host-guest interaction. To further understand
the mechanism of the host-guest interaction, herein we present the preparation of the neutral tetranuclear complex and
the UV-Vis titration study on the t-butylsulfylcalixerene (TBSC) precursor. The UV-Vis titration data indicates the strong
host guest interaction between the aspirin and H4TBSC with stoichiometric ratio of 2:1. The result is highly consistent with
that found in the MOSC.
INOR 359
Award Address (F. Albert Cotton Award in Synthetic Inorganic Chemistry sponsored by the F. Albert Cotton
Endowment Fund). Understanding and predicting the behavior of the actinides through organometallic chemistry
Jaqueline L. Kiplinger, [email protected]. Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Non-aqueous chemistry of the actinides has proved invaluable for gaining insight into the behavior and properties of these
elements in a variety of chemical environments. Our studies range from inert atmosphere syntheses of well-defined
actinide materials for nuclear fuel applications and materials science to addressing purely fundamental questions such as
the involvement of 5f-orbitals in bonding and reactivity. Using several metallocene platforms, and more recently the PNP
pincer ligand, we have discovered a variety of unusual reactivity patterns unique to the actinides. We couple our synthetic
efforts with spectroscopic and theoretical studies to gain insight into the role that forbitals and electrons play in the
reaction chemistry, electronic structure and bonding of actinide complexes. This talk will describe recent advances in this
area and their implications in applied actinide chemistry.
INOR 360
Award Address (ACS Award in Organometallic Chemistry sponsored by the Dow Chemical Co. Foundation).
Importance of organometallic chemistry in the discovery of new oxidation states of the rare earth and actinide
elements in molecular complexes
William J. Evans, [email protected]. Dept of Chemistry, University of California Irvine, Irvine, California, United States
Since the discovery of ferrocene six decades ago, organometallic chemistry has provided an extensive series of
breakthroughs that have advanced science and technology in many areas. One of the key ligands that has supported this
development is the cyclopentadienyl ligand. From the early involvement of C 5H5 in the discovery of metallocenes to more
recent highly-substituted variants that lead to sophisticated catalysts, the cyclopentadienyl ligand has been of central
importance in organometallic chemistry. Although efforts have been made to go beyond cyclopentadienyl ligands in the
“post-metallocene era,” cyclopentadienyl ligands still continue to make significant contributions. This talk will illustrate
another type of chemical advancement accessible using the cyclopentadienyl ligand: the discovery of new oxidation states
in the periodic table. A fundamental aspect of the chemistry of any element is the number of formal oxidation states
available in molecules for chemical reactions. The range of accessible oxidation states for all of the elements has been
continuously tested for decades and the boundaries were thought to be well-established across the periodic table.
However, recently the special environment provided by three silyl-substituted cyclopentadienyl ligands has led to the
discovery of the first examples of formal +2 oxidation states in molecular complexes of yttrium, holmium, erbium,
praseodymium, gadolinium, terbium, lutetium, uranium, and thorium. The synthesis, structure, and physical properties of
these complexes will be described as well as their reactivity. The implications of this organometallic approach for
increasing the range of oxidation states accessible in molecular complexes will be discussed.
INOR 361
Award Address (ACS Award in Inorganic Chemistry sponsored by Aldrich
Chemical Co., LLC). Metalloporphyrins in chemical and biological catalysis
John T. Groves, [email protected]. Princeton Univ, Princeton, New Jersey, United States
In this lecture I will discuss recent developments from our lab in the areas of biomimetic metalloporphyrin catalysts and
those of novel, heme-thiolate APO biocatalysts with active sites similar to that of cytochrome P450. A perspective of the
current state of the field will be presented with connections to key conceptual advances regarding the preparation and
characterization of high-valent metal-oxo species and their reactivity. We have directly observed and kinetically
characterized the reactive intermediate, « compound I », responsible for C-H hydroxylation by APO enzymes (1,2). Our
studies of C-H hydroxylation led to the discovery of a selective and efficient C-H fluorination mediated by a model
manganese porphyrin (3,4). The method allows the facile production of fluorinated drug analogs directly from the parent
drug. Further, fluorination with 18F sources may allow access to new PET imaging agents.
1. X. Wang, S. Peter, M. Kinne, M. Hofrichter, J. T. Groves, J. Am. Chem. Soc., 2012, 134, 12897.
2. X. Wang, S. Peter, R. Ullrich, M. Hofrichter, J. T. Groves, Angew. Chem. Int. Ed. 2013, 52, 9238.
3. W. Liu, X. Huang, M.-J. Cheng, R. J. Nielsen, W. A. Goddard, III, J. T. Groves, Science, 2012, 337, 1322.
4. X. Huang, W. Liu, H. Ren, R. Neelamegam, J. M. Hooker and J. T. Groves, J. Am.
Chem. Soc. 2014, 136, 6842.
INOR 362
Award Address (ACS Award for Creative Research and Applications of Iodine Chemistry sponsored by SQM
S.A.). Fifty years of Iodine research
Karl O. Christe, [email protected]. Univ of Southern California, Los Angeles, California, United States
A review will be given of our research in the field of iodine chemistry including the following topics. Using IF 5 as a solvent
for halogen fluoride ions, the IF6+, IF6-, I2F11- and I3F16- ions were synthesized and characterized. Subsequently, the IF 2-,
IF4-, IF4+, and IF4O- ions were prepared. The most interesting species was the IF52- anion which has an unprecedented
pentagonal-planar structure. The long-standing problems of the fluxionality of IF7 and the steric activity of the free valence
electron pair in the halogen hexafluoride anions were solved. At the limits of coordination and oxidation, the IF 5O2-, IF5O22and IF6O-, the first examples of pentagonal-bipyramidal AX5E2, AX5EO, AX5O2, and AX5YZ species, were prepared, and a
novel method for the stepwise replacement of two fluorines in iodine fluorides by an oxygen was developed. With I(ClO 4)3
and I(ClO4)4-, the first examples of highly explosive iodine perchlorates were discovered, and fluorocarbon perchlorates
were prepared by the reaction of fluorocarbon iodides with halogen perchlorates. Similarly, chlorine fluorosulfate and
perfluoroisopropyl iodide yield i-C3F7I(SO3F)2, a compound with an iodonium cation and an iodite anion. Iodine
fluorosulfate, ISO3F, can also be added across olefinic double bonds producing iodoperfluorocarbon fluorosulfates.
Further examples of the broad scope of this work are the syntheses of FOIF 4O, ClOIF4O, HOIF4O, and
tetrafluoroperiodates, and the study of the polymorphism in tetramethylammonium periodate. Recently, the long missing
I2O7 was synthesized and the potential of I2O6 as an agent for the defeat of weapons of mass destruction was
demonstrated. Most of these compounds are not only of academic interest but have many applications as High Energy
Density Materials, explosives, propellants, and chemical lasers.
INOR 363
Award Address (ACS Award for Distinguished Service in the Advancement of Inorganic Chemistry sponsored by
Strem Chemicals). Molecular magnetic and conducting materials inspired by coordination chemistry
Kim R. Dunbar, [email protected]. Texas AM Univ, College Station, Texas,
United States
Research in the field of Inorganic Chemistry continues to be inspired by the concepts of coordination chemistry that
originated with the brilliant and insightful work of Alfred Werner. Although research in transition metal coordination
compounds had long been focused on mononuclear and small polynuclear complexes, recent years have witnessed an
exciting renaissance, specifically the elaboration of larger architectures including extended structures. This progress has
been made possible largely by the advent of new characterization tools, not the least of which is the use of both powder
and single crystal X-ray diffraction methods as well as microscopy tools, gas uptake methodologies and the routine use of
SQUID magnetometers equipped with helium and capable of measuring exquisite changes in magnetic and conducting
properties over a large temperature range. In this regard the world of physics has merged beautifully with the world of
chemistry with this new type of coordination chemistry research. Properties of individual metal complexes and ligands can
be successfully mined for properties that were previously unknown or thought to be impossible for coordination
compounds. Classic cases of such achievements are the realization of room temperature magnets and conducting
materials that behave as metals with metal-nitrogen coordination bonds. Our foray into this topic has involved ligands
based on cyanide and organocyanide functional groups, research that has rewarded us with many exciting and valuable
insights into how to realize functional materials of the “soft” variety.
INOR 364
Award Address (Harry Gray Award for Creative Work in Inorganic Chemistry by a Young Investigator sponsored
by the Harry Gray Award Endowment). Colloidal quantum dots: Where d10 ions go to glow
Emily A. Weiss, [email protected]. Chemistry, Northwestern University, Chicago, Illinois, United States
Metal chalcogenide nanocrystals ("quantum dots") have been the model systems of choice to explore the effects of
nanometer-scale spatial confinement on the behavior of electrons in semiconductors for the last thirty years. The
relationship between the optical and electrical properties of quantum dots and the electronic and vibrational structure of
their inorganic cores is still an area of intense investigation, but the relationship between these properties and the
coordination chemistry at the surfaces of quantum dots has, in the last decade, emerged as an equally important area of
study. This talk explores the power of surface functionalization of nanocrystals to enhance and finely tune the dynamics of
electronically excited states and the redox activity of quantum dots, and their physical interactions with other
nanoparticles, molecules, and solvent, and demonstrates some powerful analytical techniques for characterizing the
complex, heterogeneous surfaces of these particles.
INOR 365
Award Address (ACS Award in the Chemistry of Materials sponsored by E. I. du Pont de Nemours & Co.). Use of
organometallic complexes to squeeze every last photon out of an organic LED
Mark E. Thompson, [email protected]. Department of Chemistry, University of Southern California, Los Angeles, California,
United States
We have developed a great deal of chemistry around phosphorescent iridium and platinum complexes for monochromatic
and white organic light emitting devices (OLEDs). These materials give OLEDs with efficiencies nearing the theoretical
limits. In this talk will discuss the evolution of organometallic emitters for OLEDs, highlighting our results with iridium and
platinum based materials and time permitting I will discuss our recent work with copper based phosphors for
electroluminescence. Copper based materials offer the possibility of using lower cost materials, but are typically less
stable than their Ir counterparts and have longer excited state lifetimes.
INOR 366
Solvent loss and reuptake in Na[BH(C2H3N3)3] frameworks
Barbara A. Reisner, [email protected], W. T. Price, Austin T. Muetterties. Chemistry and Biochemistry, James Madison
University, Harrisonburg, Virginia, United States
Frameworks derived from the hydrotris(1,2,4-triazolyl)borate ligand were synthesized. Na[BH(C2H3N3)3]·solvent (solvent =
H2O, DMF, IPA) crystallize as a porous framework with the distorted primitive cubic (pcu) topology. Solvent molecules
occupy the framework pores. The solvent of crystallization can be removed by heating. Isothermal thermalgravimetric
analysis shows that solvent loss is consistent with a 1-D diffusion mechanism. Variable temperature PXRD data show a
slight loss of crystallinity upon desolvation, indicating some framework decomposition, and that the materials adsorb water
from the atmosphere. The structures of Na[BH(C2H3N3)3]·solvent, their thermal behavior, stability and the kinetics of
solvent loss of will be reported.
INOR 367
Eggs in one basket: Is there a role for riboflavin binding protein in copper transport and storage?
Sheila R. Smith, [email protected], Marilee Benore, James I. Matchynski. Dept of Natural Sciences, University of
Michigan-Dearborn, Dearborn, Michigan, United
States
Copper is an essential metal in early fetal development. In the avian embryo, transport and storage is complicated by the
need to deliver a full complement of copper to the egg before laying and to store it safely in the unfertilized egg until it is
required. Two major components of egg protein, phosvitin and its precursor vitellogenin, have been shown to bind copper
in the egg, but the mode of delivery of copper to the egg remains largely undetermined. We have previously shown that
Riboflavin Binding protein, the primary transport system for the essential vitamin riboflavin, will also bind copper in vitro.
The active transport of this protein is well established, but its role in possible copper transport and storage is unexplored.
In the current work, we discuss the implications of copper binding for protein purification and examine the exchange of
copper between riboflavin binding protein and phosvitin.
INOR 368
Controlling electrochemistry in the synthesis of semiconductor nanoparticles
Amy L. Prieto1, [email protected], Emily Nock1, Patrick Reining1, Garrett P.
Wheeler2. (1) Chemistry Department, Colorado State University, Fort Collins, Colorado, United States (2) Chemistry,
University of Wisconsin, Madison, Wisconsin, United
States
We are interested in the development of solution-phase reactions for semiconductor colloidal nanocrystals. In particular,
this talk will focus on reactions where a key parameter that must be controlled is the oxidation state of a transition metal.
In the two cases I will discuss, chromium tellurides and copper zinc tin sulfides, the
electrochemistry of the transition metal is important for the goal of obtaining phase pure products.
INOR 369
Asymmetric hydroamination with titanium and tantalum: experiment and theory
Adam R. Johnson, [email protected]. Harvey Mudd College, Claremont, California, United States
Hydroamination is the atom economical addition of a N-H bond across an unsaturated C-C bond. When the substrate is
an aminoallene, the product of the reaction contains a stereogenic center. Early metal complexes with chiral bidentate
amide-alkoxide ligands have been used to catalyze the asymmetric hydroamination of aminoallenes with high
enantioselectivity. The catalytic reaction is thought to proceed through a [2+2] cycloaddition and DFT calculations have
been performed to examine ground and transition state energies. The impact of temperature and metal-to-ligand ratio on
the enatioselectivity of this reaction will be discussed, as well as future synthetic directions suggested by theory.
INOR 370
Reactivity of bis(phosphino)ferrocenediyl containing compounds
Chip Nataro, [email protected]. Lafayette Colg, Easton, Pennsylvania, United
States
Recent studies have found that the product of chloride abstraction from [M'Cl2(1, 1'bis(phosphino)metallocene)] (M' = Pd
or Pt) complexes is dependent on the 1,1'bis(phosphino)metallocene ligand (M(C 5H4PR2)2 where M = Fe, Ru or Os). With
most R groups, removal of the chloride yields a dicationic dimer with bridging chloride ligands, [(M(C5H4PR2)2M'(μ-Cl))2]+2.
However, when R = tBu the steric bulk of the R groups prevents dimerization upon chloride abstraction and instead yields
a monocation with a weak, non-covalent Fe-Pd interaction. This compound, [Pd(dtbpf)Cl]+ (dtbpf = 1, 1'-bis(ditertbutylphosphino)ferrocene) compound undergoes a temperature induced solid state isomerization to a structure in
which there is not a Fe-Pd interaction, but there is an apparent agostic interaction between the Pd and the tBu groups of
the dtbpf ligand. The chloride of [Pd(dtbpf)Cl]+ undergoes rapid halogen exchange with sources of Br - and I- to yield
[Pd(dtbpf)Br]+ and [Pd(dtbpf)I]+ respectively. The oxidative electrochemistry of this series of compounds shows a trend in
the potential at which the compound undergoes oxidation versus the halide. Computational studies indicate that the
strength of the Fe-Pd interaction follows this same trend. Additional reactions of [Pd(dtbpf)Cl] + will be discussed.
INOR 371
Allosteric and unexpected binding sites for small-molecule modulators
Michelle Arkin, [email protected]. Pharmaceutical Chemistry, University of
California, San Francisco, San Francisco, California, United States
Protein-protein interactions and allosterically regulated enzymes have been challenging but important targets for probeand drug discovery. We and others have found that fragment-based lead discovery can provide chemical starting points
and furthermore serve as insightful probes of protein conformation. The Tethering method of fragment discovery links thiol
containing compounds to specific cysteine residues and therefore serves as a site-directed approach to interrogating
‘cryptic’ allosteric sites and protein interfaces. We will describe examples of multiple discovery approaches targeting
proteins involved in cancer and neurodegeneration.
INOR 372
Aptamer technology for biosensing, therapeutics, and targeted release
Maria C. DeRosa, [email protected]. Chemistry, Carleton University, Ottawa, Ontario, Canada
The remarkable structural and functional features of DNA have made it a powerful and versatile building block for the
preparation of self-assembled materials and nanodevices. In our research lab, we are interested in DNA technology
driven by the molecular recognition properties of “aptamers”, synthetic DNA with the ability to bind tightly and specifically
to a molecular target. We are currently applying aptamer technology to biosensing and controlled release applications, as
well as developing aptamers for biologically-relevant target molecules. Our research group is particularly interested in
designing systems whereby the detection of a target molecule will lead to changes in a material and concomitant release
of a payload. As aptamers are negatively charged biopolymers, we are exploring the potential for their incorporation into
polyelectrolyte films as molecular recognition elements. We have successfully incorporated a DNA aptamer into a
multilayered polyelectrolyte thin film.[1] We have also incorporated aptamers into the walls of hollow polyelectrolyte
microcapsules in order to gauge the effect of aptamer-target binding on the permeability of the capsule walls.[2] In
microcapsules containing the sulforhodamine B aptamer within the multilayers, the diffusion coefficient for the dye was
nearly an order of magnitude greater than in microcapsules containing either a random DNA oligonucleotide, or those
comprised of synthetic polyelectrolytes alone. Our work suggests that this permeability effect is general and not limited to
the aptamer’s cognate target. More recently, we have developed stable polyelectrolyte microcapsules containing
encapsulated aptamers that serve as a scaffold to support the surrounding capsule walls. [3] Upon target-binding, the
walls collapse leading to a one-time burst release of the cargo. This presentation will highlight our latest work in this area
as well as in applying aptamers as receptors for both biosensors and in vivo use. Work in the selection of aptamers for
important small molecule and viral targets will also be described.
[1] Sultan, Y.; Walsh, R.; Monreal, C.; DeRosa, M. C. Biomacromolecules 2009, 10, 1149-1154.
[2] Sultan, Y. and DeRosa, M. C. Small 2011, 7, 1219-1226.
[3] Zhang, X.; Chabot, D; Sultan, Y.; Monreal, C.; DeRosa, M.C. ACS Appl. Mater. Interfaces 2013, 5, 5500-5507.
INOR 373
Electromechanical tissue reconstruction: A non-invasive surgical modality for reshaping cartilage of the head
and neck
Michael G. Hill1, [email protected], Jeremy Kallick1, Maya Herzig1, Bryan Hunter1,2. (1)
Chemistry, Occidental College, Pasadena, California, United States (2) Chemistry, California Institute of Technology,
Pasadena, California, United States
Functional and aesthetic defects in the head, neck, and airway that result from cancer surgery, trauma, or congenital
malformations have led to the development of surgical techniques to reshape cartilage in order to restore or recreate
damaged or absent structures. Conventional surgical techniques involve cutting, carving, or even morselizing cartilage
tissue—each of which requires classic open operations, with all the attendant medical risks and costs. We are exploring
electromechanical reshaping (EMR) as a novel tissue-reshaping technique that combines mechanical deformation with
the application of electric fields. In a typical embodiment of EMR, a cartilage sample is held in mechanical deformation by
a jig, needle electrodes are inserted into the tissue, and a constant potential is applied for 2-3 minutes. When the
electrodes and jigs are removed, the cartilage assumes a new shape that approximates the geometry of the jig (for
example, a 90o bend). Although several possible mechanisms may play a role (e.g., non-Faradaic protein and/or ion
migration through the tissue caused by applied voltage gradients) our work suggests that the dominant pathway involves
water electrolysis (and acidification) at the tissue/solution interface: (1) no EMR occurs unless at least one electrode in
contact with the cartilage is held at a potential positive of the water-oxidation limit; (2) EMR does not require a voltage
gradient across the tissue; and (3) the magnitude of EMR correlates directly with total anodic charge transferred (as
opposed to electrolysis time, applied potential, voltage gradient, etc.). In this talk, we correlate the degree of tissue
reconstruction with empirical maps of electrochemically generated pH gradients in mechanically strained tissue; we
additionally present landscapes for reactive-oxygen species associated with the electrolysis process. Taken together,
these results provide a roadmap for optimizing the conditions for effective shape change while minimizing tissue morbidity
and mortality.
INOR 374
19F MRI: Dream or reality
Valerie C. Pierre, [email protected]. Dept of Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
With sensitivity 84% that of 1H, 19F MRI has been an alluring alternative to 1H imaging for the last decade. 19F MRI is
particularly promising for responsive and targeted imaging, where the lack of fluorine nuclei in vivo results in near zero
background signal in vivo. In 19F MRI, any signal comes solely from the probe. This is a substantial advantage over
gadolinium-type responsive MRI contrast agents which have to contend with the background signal due to the high
concentration of H2O in the body.
Unfortunately, this is also the Achilles’ heel of this approach. The insensitivity of the MRI techniques requires M
concentrations of 19F for it to be observed in vivo. In order to render 19F MRI feasible, we thus have to start by improving
its sensitivity. We have followed a three-pronged approach to improving the sensitivity of these probes >100fold:
decreasing their relaxation times with appropriate lanthanides and iron complexes, incorporating symmetrically equivalent
nuclei in the same probe, and optimizing the rotational correlation time of the agent. Having optimized the sensitivity of
these probes substantially, we can now evaluate the feasibility of 19F MRI for in vivo imaging of specific biomarkers.
INOR 375
Real-time metabolic and molecular imaging In vivo by NMR hyperpolarization
Pratip K. Bhattacharya, [email protected]. Cancer Systems Imaging, The University of Texas, MD
Anderson Cancer Center, Houston, Texas, United States
Purpose: Hyperpolarized Nuclear Magnetic Resonance (NMR) is a non-toxic, nonradioactive method for assessing tissue
metabolism and other physiologic properties. Hyperpolarization allows for over 10,000-fold signal enhancement relative to
conventional NMR and MRI.
Methods: We have worked on different modalities of hyperpolarization for novel in vivo applications, including
Parahydrogen Induced Polarization (PHIP), Dynamic Nuclear Polarization (DNP) ( 13C), continuous flow DNP of water (1H)
as well as low temperature DNP of silicon nanoparticles (29Si).
Results: a) By PHIP, we have hyperpolarized diethylsuccinate and use this endogenous compound to image the
downstream metabolites of TCA cycle in real time in rodents within a minute [1]. Efforts are underway to fingerprint the 13C
resonances of the TCA cycle metabolome in different cancer models in vivo and correlate that with the gene expression
patterns. We have also developed DNP-based Chemical ReactionInduced Multi-molecular Polarization (CRIMP) to
generate multiple hyperpolarized agents to study multiple biochemical pathways and functions [2]. b) Employing water
hyperpolarized via continuous flow DNP, we were able to obtain perfusion contrast for ( 1H) MRI thereby providing
localized angiography of rat models in vivo [3]. The sensitivity gain of hyperpolarized water rivals that of gadolinium-based
contrast agents. c) We have demonstrated direct in vivo MRI of hyperpolarized 29Si nuclei in silicon particles [4]. 29Si
hyperpolarization was achieved via low temperature DNP utilizing the naturally occurring silicon dioxide defects at the
particle surface, and showed a longitudinal relaxation time of over 40 mins. Efforts are underway to employ this technique
for non-invasive virtual colonoscopy to detect polyps at an early stage as well as functionalize the nanoparticle surface for
targeted molecular imaging of cancers in vivo.
Conclusion: The three different hyperpolarized imaging modalities have opened up the possibilities for visualizing
metabolism and other molecular events in real time wherein the local status of cancer can be interrogated on the time
scale of seconds to minutes where both early detection as well as the monitoring of cancer therapy can be accomplished.
References: [1] Zacharias, et al. J Am Chem Soc 2012, 134: 934-43. [2] Lee, et al. Chem Comm 2014, 50: 13030-33. [3]
Lingwood, et al. Radiology 2012, 265: 418-25. [4] Cassidy, et al. Nature Nanotech 2013, 8: 363-68.
INOR 376
Structure and mechanism in the essential stereoinversion in carbapenem biosynthesis
Amie K. Boal, [email protected]. Penn State University, State College, Pennsylvania, United States
Carbapenem antibiotics are an important class of beta-lactam compounds used primarily as drugs of last resort in the
treatment of multidrug-resistant bacterial infections. Carbapenem resistance is rising at an alarming rate, resulting in
increased interest in understanding the biosynthetic pathways for these compounds as potential routes to novel drug
variants. Three enzymes (CarA, CarB, and CarC) are sufficient to produce the simplest naturally-occurring carbapenem,
(5R)-carbapenem-3-carboxylate.
CarA and CarB produce a bicyclic beta-lactam/2-pyrrolidine carbapenam precursor. CarC, an FeII and 2-(oxo)glutarate
(2OG)-dependent oxygenase, inverts the stereochemical configuration at bridgehead C5 to produce the active compound.
A longstanding mechanistic proposal, in which an FeIV-oxo intermediate abstracts a hydrogen atom from C5 followed by
HŸ-atom donation to the opposite face by a tyrosine residue, has never been experimentally verified because the enzyme
and carbapenam substrate are unstable. Taking advantage of recent technical advances in protein and substrate
preparation, we determined a 2.0 Å resolution X-ray structure of FeII-2OG-CarC bound to its substrate. The structure
reveals a new candidate (Tyr165) for the amino acid H-atomŸ donor. Owing to its location in a disordered loop near the
active site, Tyr165 was not visualized in previously published CarC structures lacking substrate. These studies set the
stage for mechanistic dissection of the stereoinversion reaction and highlight the importance of peripheral lid loops in
controlling reaction outcome in FeII/2OG oxygenases.
INOR 377
Preparation of isotopically labeled active site models for the [FeFe]- and [FeNi]hydrogenases
Thomas B. Rauchfuss, [email protected], Ryan Gilbert-Wilson, David
Schilter. A131CSLS Box 60-6, University of Illinois, Urbana, Illinois, United States
In this lecture we will review challenges and solutions in our efforts to prepare 57Felabeled models of the two hydrogenase
active sites. One class of targets are of the type
(diphosphine)(CO)Fe(SR)2MLn, which can be generated
from 57Fe(SR)2(diphosphine)(CO)2, generated via 57Fe2I4(iPrOH)4, obtained from iodination of 57Fe metal. A similar method
can be used to give (CO)357Fe(SR)2Ni(dppe), but proceeding via [(CO)357Fe(μ-I)(SR)2Ni(dppe)]+. Work on labeling the
diiron center is motivated by the recent report that synthetic [Fe2[(SCH2)2NH)](CN)2(CO)4]2- can be incorporated into an
apo-hydrogenase protein. We will review routes
to 57Fe2[(S2(CH2)n](CO)6 for n = 2 (efficient) and 3 (inefficient) from 57FeBr2. Finally we will describe new routes that enable
incorporation of the azadithiolate cofactor.
INOR 378
Studies of metal to ligand charge transfer states involving MM quadruply bonded complexes
Malcolm Chisholm, [email protected]. Chemistry, The Ohio State University, Columbus, Ohio, United States
Carboxylate and amidinate ligands bound to MM quadruply bonded metal centers (MM=Mo2, MoW and W2) allow for M2
δ to ligand conjugation and afford metal to ligand charge transfer absorptions that can span the region 400 - 1100 nm.
The 1MLCT states have relatively long lifetimes τ1 ~ 1 to 25ps before intersystem crossing to triplet states occur τ3 ~ 10
ns, MLCT and 1 - 100 μs for delta-delta start. The application of ultra-fast fs and ns spectroscopies allows these excited
states to be probed with respect to both
their dynamics and charge localization. Complexes having one, two, three and four πacceptor ligands have been studied
and examples of localized and delocalized excited states have been found. The experimental results have been
correlated with predictions based on electronic structure calculations based on singlet ground state and on calculations of
the anion. These studies underpin the application of these systems for photon harvesting for both photocatalysis and
photovoltaics. Applications to ground state photovoltaics have been made by photo-induced charge transfer to molecular
and solid state inorganic oxides.
UGC
INOR 379
Bimetallic actinide complexes of constraining macrocycles for small molecule activation
Polly L. Arnold1, [email protected], Natalie Potter1, Rebecca White1, Charlotte Stevens1, Michal Dutkiewicz1, Joy
Farnaby1, Roberto Caciuffo2, Christos Apostolidis2,
Olaf Walter2, Jason B. Love3, Nikolas Kaltsoyannis4, Michael Gardiner5. (1) Univ of
Edinburgh Sch of Chem, Edinburgh, London, United Kingdom (2) Institute for
Transuranium Elements, Karlsruhe, Germany (3) School of Chemistry, University of
Edinburgh, Edinburgh, United Kingdom (4) Department of Chemistry, University College
London, London, United Kingdom (5) Chemistry, University of Tasmania, Hobart, Tasmania, Australia
Organometallic f-block compounds have shown many interesting small molecule activation reactions in recent years, but it
is rare to be able to combine two of these reactive metal cations in the same ligand construct.
We will present new low-oxidation state f-block complexes of three different constrained-geometry aza-macrocyclic
ligands, focusing in particular on the synthesis of bimetallic early actinide adducts, and their reactivity towards small
molecules.
Time allowing, the electronic structure and magnetic behaviour of the uranium and neptunium complexes will be
discussed.
INOR 380
Rare earth doped alkali metal fluorides - promising new optical materials
Anja V. Mudring, [email protected]. Critical Materials Institute, Ames Laboratory, Ames, Iowa, United States
Rare earth elements are amongst the most critical materials – not only is the world market supply limited but also they are
crucial for a number of energy related technologies. However, due to their special photophysical propoerties rare earth
materials are of great interest as photonic materials. Substituting most of the precious rare earth ions and simultaneously
retaining the efficiency of the energy conversion phosphor at the nanoscale is a major and quite challenging goal. In that
context alkaline earth fluorides appear to be the cheapest, benign and readily available materials. Using alkaline earth
fluorides as with trivalent lanthanides as the optically active centers requires charge compensation as the the divalent host
cations get replaced by trivalent lanthanide ions. We have investigated the chare compensation mechanism thoroughly
with powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR
spectroscopy to gain a better understanding. In the end, which the knowledge of the subsitution mechanism we
mangaged produce nanoparticles of MF2 co-doped with Gd3+ and Eu3+ with a size of less than 10 nm where we reduced
the rare earth ion content by 94 % compared to typical GdF3:Eu VUV quantum cutting material while simultaneously
retaining the quantum cutting efficiency close to the theoretical limit (199 %). The synthetic technique also allows us to
use alkali metal fluorides as the host for divalent lanthanides such as Yb2+, Sm2+ and Eu2+. Due to the small particle size
this allowed us to study for the first time size-dependent effects such as quantum-confinement in the optical properties of
lanthanides.
INOR 381
Phosphorus- and arsenic-ligated lanthanide single-molecule magnets
Richard A. Layfield, [email protected], Thomas Pugh. Chemistry
Dept, Manchester University, Manchester, United Kingdom
Rare earth metal compounds containing soft heteroatom donor ligands have attracted considerable interest in recent
years. The combination of M3+ cations with heavy p-block donor atoms results in a so-called hard-soft 'mismatch' that can
lead to unusual bonding properties and to distinct reactivity. Within this context, rare earth complexes of anionic
phosphorus donor ligands have been extensively studied. Some analogous chemistry with anionic arsenic ligands is
known, but such compounds are still very rare. The use of P- and As-donor ligands in the design of lanthanide singlemolecule magnets (SMMs) is, however, entirely unknown. In this lecture, the dynamic magnetic properties of a series of
dysprosium complexes with phosphide, phosphinidene, arsenide and arsinidene ligands will be described. The
experimental studies are complemented by ab initio calculations, which have enabled us to construct a model for the
magnetic anisotropy and magnetization relaxation mechanisms in our SMMs. The theoretical model also provides insight
into how SMMs with larger anisotropy barriers may be designed, and selected new systems will also be presented.
INOR 382
Catalytic conversion of biomass to fuels
John C. Gordon2, [email protected], Andrew D. Sutton1, Amanda E. King4, Louis A.
Silks2, Ruilian Wu2, Marcel Schlaf3, Fraser Waldie3. (1) MS J582, LANL, Los Alamos,
New Mexico, United States (2) Los Alamos National Laboratory, Los Alamos, New
Mexico, United States (3) Chem Dept, University of Guelph, Guelph, Ontario, Canada
(4) LANL, Los Alamos, New Mexico, United States
It is essential to our National security that renewable alternatives to petrochemical feedstocks for hydrocarbon fuels are
developed. A constant, reliable supply of these fuels would help ensure that the transportation of food, medicine and
consumer goods about the country remains uninterrupted, regardless of sociopolitical conflict. Lignocellulose is a
promising source of energy derived from wood, agricultural waste, and woody grasses. The carbohydrates D-glucose
(C6), L- arabinose (C5), and Dxylose (C5) are readily obtained from the hydrolysis of lignocellulose and constitute the
most abundant renewable organic carbon source on the planet. Because they are naturally produced on such a large
scale, these sugars have the greatest potential to displace petrochemical derived transportation fuel. We have been
investigating a potentially transformational strategy aimed at obtaining high energy-density hydrocarbon fuels from nonfood based carbohydrate sources.
INOR 383
Half-sandwich metallatricarbadecaboranyl complexes at the interface of maingroup and organometallic chemistry
Larry G. Sneddon1, [email protected], Emily R. Berkeley1, Ariane PerezGavilan1,2, Patrick J. Carroll1. (1) Univ of
Pennsylvania, Philadelphia, Pennsylvania,
United States (2) Maastricht Science Programme, Maastricht University, Maastricht, Netherlands
The tricarbadecaboranyl anion, 6-R-nido-5,6,9-C3B7H9–, is a unique, highly versatile analog of the cyclopentadienide anion
that can function as either a mono-anionic h6, 6electron or an h4, 4-electron donor to transition metals. However,
compared to their metallocene counterparts, the metallatricarbadecaboranes have significantly greater oxidative,
chemical, thermal and hydrolytic stabilities, as well as an unprecedented ability to stabilize low-valent metals as a result of
the combination of their strong electron-accepting properties and hapto-sensitive structural flexibility. The syntheses,
structures and properties of a series of new half sandwich metallatricarbadecaboranyl (M = Co, Rh, Ir) that illustrate these
differences will be discussed.
INOR 384
Spin-orbit coupling: Not just for f elements
Joshua Telser3, [email protected], Skye Fortier8, Karsten Holldack7, Timothy A.
Jackson4, Jurek Krzystek1, Karsten Meyer2, Daniel J. Mindiola5, Joscha Nehrkorn7,
Andrew Ozarowski6, Alexander Schnegg7. (1) NHMFL, Tallahassee, Florida, United States (2) Anorganische Chemie,
Universitaet Erlangen, Erlangen, Germany (3) Dept of Chemistry, WB816, Roosevelt University, Chicago, Illinois, United
States (4) University of Kansas, Lawrence, Kansas, United States (5) Chemistry, University of Pennsylvania, Philadelphia,
Pennsylvania, United States (7) Helmholtz Zentrum Berlin für Materialien und Energie, Berlin, Germany (8) Chemistry,
University of Texas at El Paso, El Paso, Texas, United States
Russell-Saunders coupling, J = |L – S|, ..., L + S, i.e., maximum spin-orbit coupling (SOC), is the dominant factor in the
electronic structure of the f block ions. For the d block ions, this coupling is typically considered only in their free-ions atomic spectroscopy. In molecular complexes of the d block ions, the effects of orbital angular momentum are usually
ignored, or handled by a spin Hamiltonian model in which the effects of SOC are treated by a spin-only zero-field splitting
(zfs), usually given by a tensor that can be represented by a uniaxial component D and a rhombic component E (higher
order terms are also possible) and by anisotropy in the g matrix. This approach is perfectly reasonable when the
electronic ground state is orbitally non-degenerate, such for nickelocene (NiCp2), which has a 3A2 ground state. We will
present frequencydomain Fourier-transform THz electron paramagnetic resonance (FD-FT THz-EPR) data for NiCp2 that
demonstrates the successful use of a spin Hamiltonian for S = 1, giving D = 31 cm-1, along with an analysis using ligandfield theory and DFT calculations, as well as a comparison with other experimental techniques, such as magnetometry.
Experimental results for decamethylnickelocene (NiCp*2) will also be presented. In other high symmetry molecules where
the orbital angular momentum is unquenched (i.e., an orbitally degenerate ground state), then the spin Hamiltonian
analysis is not as appropriate, and a complete ligand-field treatment is preferable. We will demonstrate this by presenting
high-frequency and -field EPR (HFEPR) studies of chromocene (CrCp2), for which the ground state is likely 3E. We will
also discuss results from our own work and that of others where the application of a spin Hamiltonian may be improved
upon by use of a more complete treatment. These examples include complexes with unquenched angular momentum,
such as in tetragonal Ti(II), trigonal Fe(II), trigonal Ni(II), and 8-coordinate Co(II).
INOR 385
Bistability of magnetic molecules on surfaces: An overview
Roberta Sessoli1, [email protected], Matteo Mannini1, Luigi Malavolti1, Valeria
Lanzilotto1, Lorenzo Poggini1, Irene Cimatti1, Giordano Poneti1, Silviya Ninova1,
Federico Totti1, Andrea Cornia2. (1) Department of Chemistry, University of Florence, Sesto Fiorentino, Italy (2)
Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Modena, Italy
Exploitation of magnetic bistability of molecules in spintronic devices requires that the molecules are connected to
conducting substrates or electrodes. Transferring these peculiar single-molecule properties from the crystalline phase to
the device is however far from trivial. Evidences of success in this process are still scarce. One relatively fortunate
example is the family of Fe4 complexes that led to the first observation of Single-Molecule Magnet behaviour in a selfassembled monolayer, later extended also to thermally evaporable Fe 4 clusters. The possibility to manipulate these
molecules in UHV conditions allows an accurate control down to submonolayer coverages. A low temperature STM
investigation has revealed a layer by layer growth of the film with the molecules adopting short-range hexagonal order and
preferential orientation on the surface.
Organization in a strict 2D lattice can significantly influence the quantum dynamics of the magnetization of SMM by
enhancing the local dipolar fields and by altering the e evolution of the dipolar fields distribution during the relaxation
process.
Deposition on surfaces can also influence other degrees of freedom, stabilizing for instance different redox states, as
recently detected by X-ray photoemission spectroscopy in a self-assembled monolayer of functionalized TbPc2 molecules
on a silicon surface.
SMMs are not the only bistable systems of interest for spintronic applications. Indeed Spin Crossover materials have been
the target of an intense research focused at their switchable behavior when deposited on surface. Alternative switchable
systems are those exhibiting an externally induced interconversion between redox isomers, also termed Valence
Tautomerism, as in the case of cobalt complexes with dioxolene ligands.
An overview of the research activity carried in the recently-established surface-science facilities flanking the Laboratory of
Molecular Magnetism in Florence will be provided.
STM image of a submonolayer of Fe4 SMMs evaporated on Au(111)
INOR 386
New single-molecule magnets with high blocking temperatures
Katie R. Meihaus, Joseph M. Zadrozny, Selvan Demir, Xiaowen Feng, Philip C. Bunting, JeffrIIey D. Rinehart, Michael
Nippe, Jeffrey R. Long, [email protected]. Department of Chemistry, University of California, Berkeley, California,
United States
A number of strategies are being pursued for the synthesis of new single-molecule magnets exhibiting high blocking
temperatures. Mononuclear transition metal complexes with a low coordination number and appropriate electron
configuration can exhibit large orbital contributions to the magnetism, resulting in effective spin relaxation barriers as high
as 226 cm–1. The unquenched orbital angular momentum inate to the electronic structures of lanthanide ions such as
Tb3+, Dy3+, and Er3+, enable the design of large relaxation barriers in mononuclear complexes through matching of the
ligand field to the MJ level shape anisotropy. Further, the use of radical bridging ligands such as N 23– and [2,2′bipyrimidine]•– can lead to strong magnetic exchange coupling with lanthanide ions, supressing quantum tunneling
processes and resulting in molecules that display magnetic hysteresis up to a record of 14 K. Some new actinide-based
single-molecule magnets and the prospects for achieving large relaxation barriers in such species will also be discussed.
INOR 387
Molecular control of the magnetic exchange between self-assembled metal- complexes and ferromagnetic
surfaces: towards molecular spintronics
Victoria E. Campbell1,2, [email protected]. (1) CNRS, Cambridge,
Massachusetts, United States (2) Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts,
United States
Controlling the interface poses a challenge when constructing molecular spintronic devices. This study shows that it is
possible to modulate the magnetic response of a system with a molecule and control the interaction between the molecule
and the surface via the interface. A family of lanthanide complexes was synthesized by the subcomponent self-assembly
methodology. Molecular architectures, which were stable in solution and in ambient conditions, were designed by the insitu formation of ligands around metal ion templates (1: Co(II) and 2: Ni(II)). These molecules display magnetic anisotropy
and can be chemically tethered onto ferromagnetic surfaces. Anchoring induced, in the paramagnetic cobalt(II)containing complex, a magnetic ordering and hysteresis that was studied by X-ray absorption spectroscopy (XAS), X-ray
magnetic circular dichroism (XMCD) and time-of-flight secondary ion mass spectroscopy (TofSIMs). While, we do not
observe any coupling with the ferromagnetic electrode for the isostructural nickel(II)-containing complex. This result
highlights the fundamental effect that the electronic structure of the metal ion in conjunction with the nature of the organic
spacer has on the resulting molecule/electrode interaction.
Figure 1. Element-specific field dependence of the magnetization of the Co atoms of 1, the Ni atoms of 2 and of
the ferromagnetic substrate (Fe). Hysteresis curves of the Co atoms (blue), Ni atoms (green) and Fe atoms (grey)
obtained at the L2,3 edge XMCD maxima. (Monochromatized X-rays are set at the energy of the maximum absolute value
of the XMCD signal (i.e. hn = 787.5 eV for Co and hn = 851 eV for Ni) then the external magnetic field is switched step by
step from +6T down to -6T and back to +6T. At each step the magnetic field is switched from left to right circular
polarization to yield the element specific magnetization curves).
INOR 388
Ligand-field engineering of atomic clock transitions in molecular spin qubits
Stephen Hill1, [email protected], Muhandis Shiddiq1, Dorsa Komijani1, Yan Duan2,
Salvador Cardona-Serra2, Alejandro Gaita-Ariño2, Eugenio Coronado2. (1) NHMFL and Florida State University,
Tallahassee, Florida, United States (2) ICMol - Instituto de Ciencia Molecular, Universitat de València, Paterna, Valencia,
Spain
This presentation will focus on the potential utility of mononuclear HoIII (4f 10) and TbIII (4f 8) molecular nanomagnets (MNs)
encapsulated in polyoxometalate (POM) cages as molecular spin qubits. Multi-frequency continuous-wave (cw) and
pulsed electron paramagnetic resonance (EPR) measurements on single-crystals demonstrate that the lowest-lying pair of
Ligand-field (LF) states of these non-Kramers (i.e. integer moment) ions exhibit a series of optimal operating points, or
atomic clock-transitions at which the quantum spin dynamics become protected against most sources of dipolar
decoherence. Much of the presentation will focus on the HoIII system, where a significant magnetic anisotropy arises due
to a splitting of the spin-orbit coupled total angular momentum (J = L + S = 8) ground state in the POM LF. The
approximate D4d symmetry of the molecule results in a low-lying pair of mJ = ±4 singlets. High-frequency
(~50 GHz) cw EPR studies reveal a highly anisotropic eight line spectrum corresponding to transitions between the mJ =
±4 states, split by a strong hyperfine interaction with the I = 7/2 Ho nucleus (100% natural abundance). Meanwhile,
lowerfrequency studies reveal a series of avoided level crossings (tunneling gaps) between the 16 [(2I + 1) × 2] lowest-
lying electron-nuclear levels, close to zero-field, leading to a highly non-linear field-dependence of the low-frequency EPR
spectrum [1]. Electronspin-echo (ESE) measurements at X-band allow detailed studies of the coherent, coupled electronnuclear spin dynamics, including Rabi oscillations, ESE-envelopemodulation (ESEEM), and evaluation of the phase
coherence time T2. Remarkably long T2 times are found, even for the most concentrated samples, and at relatively high
temperatures (5 K). Results are analyzed for different hyperfine transitions (i.e. different ΔmI selection rules) and [HoxLn1-x]
concentrations. The long T2 times are attributed to the non-linear field effects, which give rise to points in the EPR
spectrum that are insensitive (to first order) to the applied field and, hence, immune to dipolar field fluctuations. These are
the so-called atomic clock transitions. Finally, we note that the POM encapsulation offers the possibility of preserving the
intrinsic properties of these lanthanide qubits outside of a crystal, e.g., on surfaces or in single-molecule devices [2].
[1] S. Ghosh et al., Dalton Trans. 41, 13697 (2012).
[2] J. Lehmann et al., Nat. Nanotech. 2, 312 (2007).
INOR 389
Magnetic cyanide-based coordination nanoparticles and heterostructures
Laure Catala1, [email protected], Yoann Prado2, Mauricio López Jordà1, Sandra Mazerat1, Talal Mallah1. (1)
Université Paris Sud, Orsay, France (2) CRPP, Pessac,
France
While Si-based CMOS still has some room for improvement, it is acknowledged that this technology will not continue
longer than the next decade and that the development of new materials and new paradigms is becoming increasingly
important. In this context, new functional materials based on assemblies of coordination nanoparticles are of particular
interest. Nanoparticles that may be tuned by several stimuli such as light, temperature, pressure, electric or magnetic
fields may be synthesized using coordination networks such as bimetallic cyanide-bridged compounds. During the past
few years, we have demonstrated simple and efficient routes to tailored heterostructures based on these kinds of
compounds leading to new magnetic properties. This communication will illustrate the potential of selected nano-objects
and various routes towards their integration in low power spintronics devices will be discussed.
INOR 390
Metal-molecule-metal junctions: A versatile platform to investigate molecular electronics/spintronics
Robert C. Bruce, Joshua D. Yablonski, Travis W. LaJoie, Wei You,
[email protected]. Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States
A wide variety of techniques have been employed to incorporate organic and small molecules into electrical devices, and
understanding the effects of device architecture and how the architecture impacts measured charge transport properties is
still an open endeavor. This talk will summarize our efforts in applying nanotransfer printing (nTP) to construct metalmolecule-metal junctions, which serve as a versatile platform to investigate the electron/spin transport behaviors of
organic molecules, from insulating alkanes to conjugated oligomers. Specifically, we will use a series of oligoparaphenylenedithiols to show that the nTP architecture can generate different charge transport properties compared to
different architectures that study identical monolayers. We will explain that the chemical bond formed between molecule
and electrode via our nTP technique can alter interfacial energy levels, leading to unique electrical output in
phenylenedithiol devices. We will also show a dependence of monolayer quality and charge transport property on
deprotection conditions used to remove ethyltrimethylsilane (ETMS) protecting groups on our monolayers. We propose a
mechanism of deprotection related to concentration of deprotectant added that may have an impact on the use of any
protecting group in SAM formation.
Figure 1. A) Diagram of nTP device which is characterized by cAFM. B) Representative 200 nm diameter gold contacts, printed via
nTP onto a tphDSH monolayer. Pad height is measured to be around 13 nm.
INOR 391
Transition metal-catalyzed nucleophilic (radio)fluorination
Abigail G. Doyle, [email protected]. Princeton University, Princeton, New Jersey, United States
An expansive array of medicines, agrochemicals, and materials contain fluorine due to the unique chemical properties that
the element confers on organic molecules. One of the chief obstacles to the discovery and production of these
compounds is the availability of synthetic methods for carbon–fluorine (C–F) bond formation. The most abundant and
inexpensive fluorine sources, nucleophilic fluoride salts, typically suffer from low solubility, high hygroscopicity, and strong
Brønsted basicity, rendering them recalcitrant reagents for chemical synthesis. Nevertheless, our laboratory has recently
identified strategies that achieve mild and efficient nucleophilic fluorination using transition metal catalysis. This lecture will
describe some of our recent progress in methodology development. Mechanistic studies will be discussed that contribute
a better understanding of the properties and reactivity of transition metal fluorides. Furthermore, this lecture will cover
application of our methods to the preparation of small-molecule tracers containing the radionuclide 18F for positron
emission tomography (PET).
INOR 392
Formation and reactivity of new primary copper(I)-dioxygen adducts
Kenneth D. Karlin, [email protected]. Chemistry Dept NCB 213, Johns Hopkins Univ, Baltimore, Maryland, United States
Mononuclear ligand-copper(I)-dioxygen adducts are best described as cupricsuperoxide complexes. Their structures,
properties and reactivity toward protons and-or electrons and-or substrates are of fundamental interest in chemicals
systems where O2reduction occurs (e,g,, in fuel cells) or where organic substrates are oxidized. Initially formed
mononuclear copper(I)-dioxygen adducts are also found in copper enzymes where they either attack a substrate or are
protonated-reduced. A primary research approach in copper-dioxygen chemistry focuses on ligand design and variation
and the use of cryogenic solution handling for the study of new complexes. In these contexts, a description of new
(ligand)Cu(II)-superoxo complexes will be presented, those which can effect the oxidation of C–H and O–H containing
substrates, or those undergoing reduction-protonation and/or (c) those where reversible reduction of a superoxo- to a
peroxo-dicopper(II) occurs. Progress toward the generation and study of cupric superoxo complexes possessing a
thioether ligand-donor or H-bonding moieties will be presented.
INOR 393
Effects of heme ruffling on vibrational dynamics, electronic structure, and electronic coupling
Kara L. Bren5, [email protected], Nicolai Lehnert4, Paul M. Champion2, Sean
J. Elliott1, Mary Grace Galinato3. (1) Boston University, Boston, Massachusetts, United States (2) Northeastern Univ
Physics Dept, Boston, Massachusetts, United States (3)
Penn State Erie, The Behrend College, Erie, Pennsylvania, United States (4) Univ of Michigan, Ann Arbor, Michigan,
United States (5) Chem Dept, Univ of Rochester, Rochester, New York, United States
Heme cofactors in proteins usually display distortions from planarity, and it has been proposed that distortions play a role
in determining reactivity. In cytochromes c, the heme cofactor is ruffled, but the effect of ruffling on function has not been
clear. To better understand the effects of ruffling on heme properties, cytochrome c variants with different amounts of
ruffling have been prepared and studied using electrochemistry, nuclear magnetic resonance (NMR), nuclear resonance
vibrational spectroscopy (NRVS), vibrational coherence spectroscopy (VCS), resonance Raman, and transient absorption
spectroscopy. The results indicate that increasing ruffling increases porphyrin ligand field strength and decreases
reduction potential. Furthermore, ruffling
decreases delocalization of Fe d(π)-based molecular orbitals to the β-pyrrole carbons, resulting in decreased coupling to
redox partners and lower electron transfer rates. In addition, ruffling influences iron vibrational dynamics, which are
strongly coupled to polypeptide vibrations. These results provide a basis for understanding the effect of cytochrome c
association with membranes on heme conformation and electron transfer activity.
INOR 394
Protein-like proton exchange in a synthetic host cavity
Kenneth N. Raymond2, [email protected], Robert G. Bergman3, Dean
Toste1. (1) Department of Chemistry, Berkeley, California, United States (2) Univ of
California, Berkeley, California, United States (3) University of California, Berkeley, California, United States
When dissolved in D2O, a metal-ligand host molecule (K12Ga4L6) undergoes amide hydrogen/deuterium exchange with the
bulk solution. A puzzling relationship between the rate of amide hydrogen/deuterium exchange and Ka of the guest
(alkylammonium or phosphonium) encapsulated was observed. Further experiments supported and hydrogen/deuterium
exchange mechanism that is driven by a host whose cavity is encapsulated by water. Variable rate vs. pH measurements
demonstrate that the mechanism of amide proton exchange is shifted by up to a factor of a million relative to well-studied
polypeptides. These results show that the unusual microenvironment of the K12Ga4L6 host can dramatically influence the
reactivity of associated in a manner reminiscent of polypeptides.
INOR 395
Cytochrome P450 oxidations: A controlled burn of inert organic compounds
Michael T. Green, [email protected]. Chemistry, Pennsylvania State University, University Park, Pennsylvania,
United States
Cytochrome P450 enzymes play critical roles in hormone synthesis and xenobiotic metabolism. Since the discovery of
P450s over four decades ago, chemists have been enamored with their ability to selectively functionalize a wide range of
organic compounds. Two enigmatic aspects of P450 chemistry are i) the enzyme’s use of an electron-rich thiolate ligated
heme to catalyze the oxidation of inert hydrocarbons and ii) the enzyme’s ability to perform these demanding oxidations
without damage to its own relatively fragile protein superstructure. It has been suggested that the electron-donating
thiolate ligand promotes C-H bond activation at biologically viable reduction potentials through the generation of basic
iron(IV)oxo (or ferryl) species. The metal-oxo pKa is thought to be a key thermodynamic parameter in C-H bond activation
with a unit increase in ferryl pKa allowing for a 59 mV drop in the one-electron reduction potential of compound I, the
active intermediate in P450 catalysis. It has been proposed that this drop in reduction potential decreases the driving force
for deleterious autooxidations, biasing the system for C-H bond activation. However, while experiments have confirmed
the basic nature of ferryl P450s, the full magnitude of the ferryl pKa’s role in hydrocarbon oxidations has proven difficult to
assess. Recently we identified a P450
(CYP158) whose ferryl form can be prepared in ≥ 90% yield over a wide pH range. Using Mössbauer and UV/Visible
spectroscopies (in conjunction with X-ray absorption measurements) we determined a ferryl pKa of 11.9. This value is
remarkable. It is at least 8.5 units higher than the ferryl pKas of histidine-ligated peroxidases and globins, allowing for
more than a 0.5V drop in the one-electron reduction potential of compound I. Arguments based on Marcus theory indicate
that this change in potential results in over a 10,000 fold reduction in the rate constant for oxidations of the protein
superstructure, making these processes noncompetitive with substrate oxidation.
INOR 396
Platinum and other third row transition metals for treating cancer
Stephen J. Lippard, [email protected]. Chemistry, Massachusetts Institute of
Technology, Cambridge, Massachusetts, United States
Platinum compounds are a mainstay of cancer chemotherapy, with over 50% of patients receiving a platinum drug. But
there is a great need for improvement. Major features of the cisplatin mechanism of action involve cancer cell entry,
formation mainly of intrastrand cross-links that bend and unwind nuclear DNA, transcription inhibition, and induction of cell
death programs while evading repair. Recently we discovered that platinum cross-link formation is not essential for
activity. Monofunctional Pt compounds like phenanthriplatin, which make only a single bond to DNA nucleobases, can be
far more active and effective against a different range of tumor types. Without a cross-linkinduced bend, monofunctional
platinum complexes can be accommodated in the major groove of DNA. Their biological mechanism of action is similar to
that of cisplatin. These discoveries opened the door to a large family of third row transition metal-based drug candidates,
including those of Os and Re. The osmium complex [Os(N)Cl3(o-phen)] has the remarkable ability to destroy cancer stem
cells thought to play a key role in cancer recurrence following conventional chemotherapy and in metastasis. This work
was supported by the National Cancer Institute and the Koch Institute for Integrated Cancer Research at MIT.
INOR 397
Coordination chemistry underlying the promise and pitfalls of Ti(IV) anticancer drugs
Ann Valentine, [email protected]. Temple University, Wynnewood, Pennsylvania, United States
Titanium anticancer drugs have not yet fulfilled their early promise. The medicinal chemistry of Ti(IV) is complicated partly
because its fundamental aqueous chemistry is so challenging: the ion is very prone to hydrolysis. We will report on our
studies of titanium coordination chemistry under biologically and environmentally relevant conditions, and of the
interactions of titanium ions and their complexes with biological molecules. Interactions with iron trafficking proteins are
particularly important. This chemistry is relevant to the bioactivity of many Ti(IV) complexes as well as to the effects of
formulation of the compounds used in human clinical trials, and thus to the fate of those trials. Ultimately, these
fundamental studies are relevant to ongoing efforts to realize the potential of titanium anticancer drugs.
INOR 398
Covalent photo-adducts of Ru-TAP complexes with DNA guanine bases: Their applications and mechanisms of
formation
Andree Kirsch-De Mesmaeker, [email protected], Lionel Marcelis. Chimie
Organique Photochimie, U L B (Université libre de Bruxelles), 1050 Bruxelles, Belgium
We have shown since many years that the illumination of Ru-TAP complexes (TAP = 1, 4, 5, 8-tetraazaphenanthrene) in
presence of guanine (G) bases either belonging to mononucleotides or DNA gives rise to formation of an irreversible
covalent adduct between the nitrogen 2 of guanine and the carbone in ortho position of the non chelated nitrogen of TAP.
The structure of this photo-adduct was determined previously by NMR.
Several biological applications more particularly in gene-silencing, have been developed with these Ru-TAP complexes
tethered to oligonucleotides. Photo-bridging can be obtained between such Ru-conjugates and G containing DNA or
oligonucleotides. In the frame of these investigations, we discovered that photo-bridging can also be observed between
two G bases of complementary oligonucleotides or DNA strands via a simple Ru-TAP complex (not tethered to an
oligonucleotide). This means that not only a monoadduct of a G base can be produced, but also a second addition of a
second G base can take place on the same Ru complex. This very interesting photo-induced bridging process was a bit
intriguing.
Indeed when the first photo-adduct was isolated for its characterization, it revealed no luminescence, in contrast to the
starting Ru-TAP complex, which is a good emitter. Therefore how would it be possible to add a second G moiety under
illumination of the mono-adduct when this latter is very short-lived in the excited state.
The study of the behaviour of the isolated mono-adduct will be presented and discussed in view of explaining its photoinduced oligonucleotide and DNA crosslinking observed by gel electrophoresis and AFM (Atomic Force Microscopy). A
mechanism will be proposed and discussed as a function of the solution pH, based on kinetic studies under steady state
and pulsed laser illumination from the femto and picosecond time domain to the nano and microsecond time-scale.
Photo-adduct
INOR 399
Metalloglycomics approach to antimetastatic platinum
Nicholas Farrell1,3, [email protected], Erica Peterson2, Mark von Itzstein3, Christopher
Parish4, Anna Bezos4, Susan J. Berners-Price3. (1) Department of Chemistry, Virginia
Commonwealth University, Richmond, Virginia, United States (2) VCU, Richmond,
Virginia, United States (3) Institute for Glycomics, Griffith University, Gold Coast,
Queensland, Australia (4) John Curtin School of Medical Research, The Australian
National University, Canberra, Australian Capital Territory, Australia
The high affinity for polynuclear platinum compounds (PPCs), including the Phase II clinical trial compound, BBR3464, for
glycosoaminoglycans (GAGs) has identified a new mechanism of cellular accumulation for this class of antitumor agents,
one not shared by the mononuclear cisplatin and oxaliplatin. [1] Cell-surface and extracellular matrix glycoaminoglycans
(GAGs) are complex oligosaccharides that regulate several aspects of cancer biology, including tumor progression,
invasion and metastasis. Tumors aberrantly express various glycans, where proliferation and motility of tumor cells is
potentiated by their ability to bind growth-factors, such as FGF and VEGF, and to directly activate tyrosine kinase
receptors.[2]
We here demonstrate that the strong binding of PPCs to oligosaccharides provides a new approach to glycan-based
targeting through protection against enzymatic cleavage by heparanase.[3] The end result of inhibition of heparanase
cleavage and growth factor binding to GAGs is a reduction in tumor invasion and angiogenesis.
Metalloglycomics - the study of defined coordination compounds with oligosaccharides - has rich and multiple applications
in the area of structure and function of this third major class of biomolecules after DNA/RNA and proteins. The inherent
ability to alter oxidation state, coordination number and geometry, and substitution lability of ligands allows study of a wide
variety of structural types to enhance shielding and enzyme inhibition. In this context, the polynuclear platinum structure
represents a potentially rich chemotype and has promise as a dual-function chemotherapeutic allying its DNA-binding
ability to that of anti-metastasis. References
[1] H. Silva, F. Frézard, E.J. Peterson, P. Kabolizadeh, J.J. Ryan, N.P. Farrell, Mol.
Pharm. 2012, 9, 1795-1802.
[2] M.M. Fuster, and J.D. Esko, Nature Rev. Cancer 2005, 5, 526-542.
[3] J.B. Mangrum, B.J. Engelmann, E.J.Peterson, J.J. Ryan, S.J. Berners-Price, N.P. Farrell. Chem. Commun. 2014, 50,
4056 – 4058.
INOR 400
Transient spectroscopic studies of enantiomerically-resolved intercalating ruthenium dipyridophenazine (dppz)
complexes bound to defined sequence DNA
John M. Kelly1, [email protected], Christine Cardin2. (1) Chemistry, Trinity College
Dublin, Dublin, Ireland (2) Chemistry, University of Reading, Reading, United Kingdom
While the DNA-binding properties of complexes [Ru(phen)2(dppz)]2+ and
[Ru(TAP)2(dppz)]2+ (phen= 1,10-phenathroline; TAP = 1,4,5,8-tetraphenanthrene; dppz = dipyrido[3,2-a:2’,3’-c]phenazine)
are expected to be similar (as illustrated by our recent high resolution X-Ray crystal structures 1), their photophysical
behaviour is strongly contrasting. Thus [Ru(phen)2(dppz)]2+ behaves as a DNA light-switch, being essentially nonluminescent in water,2 whereas the photoemission of
[Ru(TAP)2(dppz)]2+ is quenched by electron transfer when binding close to guanine. 3 Using the same defined sequence
nucleic acids as used for the crystal studies, we have carried out complementary time-resolved mid-infra-red (TRIR) and
visible spectroscopic measurements which not only provide new insights into the nature and the reactivity of the excited
states but also about their interactions at particular binding sites. The spectroscopic properties of the excited states of the
complexes have also been examined by DFT methods.
Acknowledgements. This work has been partially funded by the BBSRC (Grant No. BB/K 019279/1) and the Royal Irish
Academy/Royal Society. High-End Computing at the DJEI/DES/ SFI/HEA Irish Centre is gratefully acknowledged. Access
to the CLF Ultrafast laboratory was funded through EU FP7 (Appl. No 12240002) and Appl. No. 13230023.
1. (a) Hall, J. P et al. Proc. Natl Acad. Sci., 2011, 108, 17610-17614; (b) Niyazi, H et al. Nature Chemistry, 2012, 3, 621-628;
2.
3.
(c) Hall, J. P et al. J.Am.Chem.Soc., 2013, 135, 12652-12659.
McKinley, A.W.; Lincoln, P.; Tuite, E. M. Coord. Chem. Rev. 2011, 255, 2676-2692 and refs therein
Elias, B.; et al. Chemistry – Eur. J, 2008, 14, 369-375.
INOR 401
Selective binding of bifunctional Zn(II) complexes to G-quadruplex DNA
Matthew Fountain2, [email protected], Janet R. Morrow1, Kevin E. Siters1, Mariya Shapovalova2, Melissa Shively2.
(1) SUNY Buffalo, Buffalo, New York, United States (2)
Chemistry and Biochemistry Department, Fredonia, State University of New York, Fredonia, New York, United States
We have synthesized a series of bifunctional thymine recognition agents consisting of a Zn(II) cyclen macrocyclic motif
and an aromatic pendent group which selectively binds thymines in the lateral loops of G-quadruplexes. The binding of
these bifunctional complexes to various G-quadruplexes was characterized using isothermal titration calorimetry, circular
dichroism and fluorescence spectroscopy. In addition, a PCR stop assay was utilized to determine if these compounds
inhibit Taq polymerase by stabilizing the G-quadruplex. From these studies a Zn(II) cyclen with a bound dansyl pendent
group, Zn(DSC), exhibited selective binding to the H-Telo G-quadruplex with a Kd of 2.5 µM and a binding stoichiometry of
2:1. The PCR stop assay for H-Telo shows Zn(DSC) inhibits Taq polymerase with an IC50 of 3.0 ± 1 µM. The overall
results from this study shows that these bifunctional complexes can selectively bind and stabilize Gquadruplexes making
them potential therapeutic agents.
INOR 402
Multifunctional supramolecules for interactions with DNA and cancer cells exploiting photohemical activation
Roberto Padilla3, [email protected], Jose A. Rodriguez Corrales3, Jie Zhu2, Jerry Newman3, Reece Prussin3, Karen S.
Brewer1, Elise M. Naughton4,
[email protected]. (1) Virginia Polytech Inst, Blacksburg, Virginia, United States (2)
Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia,
United States (3) Virginia Tech, Blacksburg, Virginia, United States
Mixed-metal complexes have been prepared and studied with a number of sub-units to provide for multifunctional
supramolecules with multiple means of interactions with biomolecules. Sub-units are used as targets (TAR), delivery
vehicles (DEL), light absorbers (LA), luminescent reporters (LUM) bridging ligands (BL), thermally activated bioactive sites
(TAB), and photochemical activated bioactive sites (PAB). LA employed are Ru and Os polyazine MLCT absorbers, BL
are bis(diimine) ligands capable for connecting two metal centers together. TAB centers are cis-PtCl2 units that bind to
DNA thermally similar to cisplatin. PAB are of two types, oxygen dependent (MLCT ROS generators) and oxygen
independent (cis-RhCl2). The expansion of the structural diversity of these supramolecules has led to the development of
systems with complex interactions with biomolecules. Recent studies have shown a PAB(LA)-BL-TAB molecule to be
active as a light activated drug to kill rat malignant glioma F98 cells. LUM-LA(PAB)-BL systems have been developed as
initial test systems to study metal complex uptake and cellular distribution via confocal microscopy with oxygen dependent
phototoxcity. LA-BL-PAB systems have been prepared that allow for light activation with red light to lead to
photomodification of DNA through the PAB site. Other motifs will be described and relating structure and function. The
authors thank the NSF CHE-1301131 and VT ICTAS for generous support of this work.
INOR 403
Molecular spintronics: The role of chemistry
Eugenio Coronado, [email protected]. ICMol - Instituto de Ciencia Molecular, Universitat de València, Paterna,
Valencia, Spain
Spin-based electronics is one of the emerging branches in today’s nanotechnology and the most active area within
nanomagnetism. So far spintronics has been based on conventional materials like inorganic metals and semiconductors.
However, a new trend is emerging that uses molecule-based materials, or even single-molecules, as components of new
spintronic systems and devices. This new area, namely molecular spintronics is at the intersection of molecular
electronics, molecular magnetism and spintronics [1]. In this talk I will show the key role played by chemistry in molecular
spintronics. The first example will deal with the chemical design of single-molecule magnets which can be useful as qubits
in quantum computing [2]. The second example will concern the design of switchable nanodevices made on spincrossover nanoparticles [3]. The third example will focus on the fabrication of multifunctional molecular devices exhibiting
magneto-electro-luminescence (i.e., Spin-OLEDs).
[1] J. Camarero, E. Coronado, J. Mater. Chem. 19, 1678 (2009).
[2] J. M. Clemente-Juan, E. Coronado, A. Gaita-Ariño, Chem. Soc. Rev. 41, 7464 (2012).
[3] F. Prins, et al. Adv. Mater. 23, 1545 (2011).
INOR 404
Strong magnetic exchange, slow magnetic relaxation, and spin crossover in iminobenzoquinonoid dinuclear
complexes
Ie-Rang Jeon2, Jordan DeGayner2, Jesse G. Park1, Alexandra Gaudette2, David
Harris2, [email protected]. (1) Chemistry, Northwestern University, Evanston,
Illinois, United States (2) Dept. of Chemistry, Northwestern University, Evanston, Illinois,
United States
This presentation will describe our efforts (1) to synthesize single-molecule magnets with well-isolated spin ground states
by employing radical bridging ligands and (2) to study electronic effects on spin crossover in a series of Fe2 complexes.
First, a series of azophenine radical-bridged dinuclear was synthesized. Magnetic measurements of these complexes
reveals the presence of strong antiferromagnetic exchange between M II centers and azophenine radical, with estimated
coupling constants of J = −150 (Mn), −900 (Fe), −310 (Co), and J = −600 (Ni) cm−1. The Fe congener behaves as a
singlemolecule magnet with a relaxation barrier of Ueff = 50(1) cm−1. Additionally, a series of 3,6-disubstituted-2,5dianilino-1,4-benzoquinone-bridged Fe2 complexes with slightly different bridging ligand substitution (H, F, Cl, Br) was
synthesized to enable a systemic study of electronic effects on spin crossover. Variable-temperature dc magnetic
susceptibility provide transition temperatures of T1/2 = 160(1), 124(1), 121(1) and 110(1) K for X = H, Br, Cl, and F,
respectively, along with enthalpies of ΔH = 11.4(3), 8.5(3), 8.3(3) and 7.5(2) kJ/mol. When plotted as a function of the
Pauling electronegativity of the substituent, T1/2 and ΔH undergo a linear decrease. Further analysis of the lowtemperature
magnetic data, in conjunction with variable-temperature Mössbauer spectroscopy, suggest that the incomplete spin
crossover behavior in
[(TPyA)2Fe2(XL)]2+ is best described as a transition from purely [FeHS-FeHS] (HS = highspin) complexes at high temperature
to a mixture of [FeHS-FeHS] and [FeHS-FeLS] (LS = low-spin) complexes at low temperature, with the number of [FeHS-FeLS]
species increasing with decreasing electron-withdrawing character of the bridging ligand
INOR 405
Multifunctionality in spin-crossover complexes: Toward “molecular multiferroics”
Hoa Phan1, Jeremy J. Hrudka1, Jeff Lengyel1, Shermane Benjamin2, Eden Steven2, Nar
S. Dalal1, James Brooks2, Michael Shatruk1, [email protected]. (1) Dept of
Chemistry Biochemistry, Florida State University, Tallahassee, Florida, United States
(2) National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States
Multifuntional materials have received a great deal of attention in the quest for miniaturizing electronic devices and
increasing their efficiency. In particular, recent research on multiferroics and magnetoelectrics has been at the forefront of
solid-state chemistry. In striking contrast, the potential of molecular materials to exhibit coupling between magnetic
transitions and transport or dielectric properties remains essentially untapped. In this vein, the spin-state switching in the
complexes of transition metal ions is especially appealing, since such spin transitions are associated with dramatic
changes in the crystal packing that might be translated into abrupt modification of the conductivity or dielectric response.
In this contribution, we report our first steps toward the implementation of molecular multi-property materials akin to
multiferroics. We show that the known spin-crossover cations can be co-crystallized with organic radical anions to afford
molecular semiconductors that exhibit both temperature- and light-driven spinstate conversion. A similar co-crystallization
of the spin-crossover cations with hydrogen-bonding anions provides a material with the strong change in the dielectric
properties coupled to the spin transition due to magnetostructural correlations.
INOR 406
Recent fun in homo- and heterometallic manganese cluster chemistry
George Christou, [email protected], Annaliese E. Thuijs, Kylie Mitchell, Andrew
M. Mowson, Adeline Fournet, Khalil A. Abboud. Department of Chemistry, Univ of Florida, Gainesville, Florida, United
States
Manganese clusters hold a special place in the field of high spin molecules and singlemolecule magnets (SMMs). They
were the birthplace of the SMM phenomenon and the source of the majority of known high spin molecules. Their
interesting behaviors arise from the unusual properties of MnIII/IV, including their propensity to exhibit ferromagnetic
coupling on a regular basis, and the significant zero-field splitting of Jahn-Teller elongated MnIII. Our group has been
heavily involved in Mn chemistry for many years and yet is still regularly surprised by the unusual structural or magnetic
properties observed in new clusters that we synthesize. In this presentation, dedicated to Kim R. Dunbar on the occasion
of her well-deserved ACS award, the syntheses, structures, and magnetic and other selected properties of some new
compound types will be described.
INOR 407
Adventures in spin crossover phenomena: (Giant) memory effect in magnetic and in hybrid conducting materials
Jose Ramon Galan-Mascaros1,2, [email protected], Cristina Saenz de Pipaon1, Pilar Maldonado-Illescas1, Yong-Sung
Koo1, Veronica Gomez1. (1) Institute of Chemical
Research of Catalonia, Tarragona, Spain (2) Catalan Institution for Research and Advanced Studies (ICREA), Barcelona,
Spain
Spin crossover (SC) compounds are a paradigmatic example of bistable materials. In such metal complexes the magnetic
state can be tuned from a low-spin (LS) configuration into a low-lying meta-stable high-spin (HS) configuration through
external stimuli. They have been postulated as bulk components for new generation memory devices and sensors. 1 The
most remarkable compounds have been obtained in the coordination chemistry of octahedral Fe II, since the transition
from diamagnetic S = 0 to paramagnetic S = 2 includes major changes in magnetism, electronic and spectroscopic
properties, and even in size. When coordinated by triazole (trz) ligands, trz-bridged FeII 1D chains are formed with spin
transition occurring over room temperature, and exhibiting wide thermal hysteresis cycles (> 40 K), with those features
easily tuned by functionalization of the trz or by substitution of the counter ions.2
Here we will report how further modifications in the trz ligands yield novel coordination FeII complexes with thermal
hysteresis over 100 K in the solid state and around room temperature. We will also illustrate how these SC compounds
can be incorporated into conducting networks to deliver multifunctional materials where the electrical conductivity exhibits
also a memory effect, since the spin transition triggers a synergic switching in the transport properties (Figure 1).3
[1] A. Bousseksou et al. Chem. Soc. Rev. 2011, 40, 3313.
[2] O. Kahn and C. J. Martínez, Science 1998, 279, 44.
[3] Y. S. Koo and J. R. Galan-Mascaros, Adv. Mater. 2014, DOI:
10.1002/adma.201402579
Thermal hysteresis in the conductivity of a hybrid organic conducting polymer with embedded SC complexes
INOR 408
Magnetic metal-cyanide coordination clusters and chains
Xiaowen Feng, Danna E. Freedman, T. David Harris, Hye Jin Choi, Bart M. Bartlett,
David M. Jenkins, Hemamala I. Karunadasa, Joseph M. Zadrozny, Miriam V. Bennett,
Jeffrey R. Long, [email protected]. Department of Chemistry, University of California, Berkeley, California, United
States
In an effort to produce new examples of single-molecule magnets, we have explored directed assembly routes to highnuclearity metal-cyanide clusters. The use of multidentate capping ligands has led to the synthesis of a range of star-like
and polyhedral species featuring as many as 27 metal centers. Substitution of a variety of transition metal ions into these
geometries is shown to permit adjustment of the ground state spin and magnetic anisotropy associated with the
molecules. In particular, the use of second- and third-row transition metal ions with a large spin-orbit coupling is found
enhance magnetic relaxation barriers. Extension of this approach to the syntheis of cyano-bridged single-chain magnets
will also be discussed.
INOR 409
How to get what you want: A control freak’s guide to inorganic nanoparticle synthesis
Raymond E. Schaak, [email protected]. Pennsylvania State University, University Park, Pennsylvania, United
States
The targeted functions of inorganic nanostructures often place strict requirements on their materials characteristics, which
can include crystal structure, composition, and morphology, as well as connectivity in multi-component systems. Synthetic
capabilities must map onto these requirements and provide on-demand access to a growing number of highly
sophisticated nanostructural features. This talk will highlight two approaches for controlling key materials features of
hybrid nanoparticle systems, which have interesting and useful catalytic, plasmonic, and magnetic properties. First, a
chemical transformation approach for incorporating arbitrary materials into hybrid nanoparticle constructs will be
presented. Second, strategies for accessing multiple distinct isomeric configurations in ternary hybrid nanoparticle
systems will be discussed. These approaches provide new capabilities for controllably and predictably accessing desired
hybrid nanoparticle constructs with targeted functions.
INOR 410
Multifunctionality at extreme conditions: spin cross-over photomagnetic behavior induced by pressure
Dawid Pinkowicz, [email protected]. Faculty of Chemistry, Jagiellonian University, Krakow, Poland
Combination of long range magnetic ordering, pressure-induced spin-crossover transition and light induced excited spin
state trapping (LIESST) in a single cyanidebridged FeNb compound has led to the first observation of a LIESST–based
photomagnetic effect under high hydrostatic pressure and low temperature. Under ambient pressure FeNb shows long
range magnetic ordering at Tc = 9 K (ferrimagnetic) with large net magnetization (9.6 μB), magnetic hysteresis and
relatively strong antiferromagnetic superexchange interactions between the high-spin FeII (S = 2) and NbIV (S = ½)
centers: JFeNb = -3.1 cm-1 (H = -2.JFeNb.SFe.SNb). When the compound is subjected to high external pressure some of the
FeII centers undergo spin-crossover transition and become diamagnetic (low-spin, S = 0) leading to the change of the
magnetic ordering from ferrimagnetic to antiferromagnetic/metamagnetic at 5-10 kbar with large decrease of the
magnetization below 9 K (Figure 1a). FeNb shows also a distinct piezochromic effect at room temperature (Figure 1b).
Irradiation of the FeNb under 5-7 kbar using blue laser light (λ = 473 nm) results in the observation of an immediate
spontaneous magnetization with critical temperature at ca. 8 K and magnetic hysteresis. Such a significant increase of
magnetization is attributed to a photomagnetic effect under pressure. It is fully reversible: heating to 50 K under 5-7 kbar
restores the antiferromagnetic state and releasing the pressure restores the original long range magnetic ordering.
INOR 411
Spectroscopic and computational studies on a bimetallic hydroformylation catalyst system
George G. Stanley, [email protected], Ranelka Fernando, Marshall Moulis. Louisiana
State Univ, Baton Rouge, Louisiana, United States
New results on the hydroformylation of alkenes by dirhodium tetraphosphine complexes will be presented. The key role of
water in dramatically enhancing the activity and selectivity of our dirhodium catalyst has been discerned and will be
discussed along with spectroscopic and DFT computational studies on the mechanism, along with the key role of
bimetallic cooperativity. A new stronger chelating tetraphosphine ligand has been synthesized and results on the
dirhodium system based on this will be presented.
INOR 412
Activation of C-F bonds: The next stage
Thomas G. Richmond, [email protected]. Univ of Utah, Salt Lake City, Utah, United States
Highly fluorinated organic compounds are often technologically useful as a consequence of the great strength of the C-F
bond. Coupling the stability imparted by the C-F bond with the nonpolar nature of saturated perfluorocarbons often leads
to a lack of reactivity. There are now numerous examples across the periodic table, include the d- and f-block metals of
exploiting transition metals to activate and functionalize aromatic fluorocarbons. This talk will demonstrate that
perflurocarbons are indeed reactive molecules and susceptible to attack by both electrophilic and nucleophilic reagents
under mild conditions. For example, the classical [Co(bpy)3]+ coordination complex is capable of catalyzing defluorination
of perfluorodecalin utilizing sodium borohydride as the terminal reductant.
INOR 413
Dehydrocoupling: Then and now
Joyce Y. Corey, [email protected]. Chemistry and Biochemistry, University of MissouriSt. Louis, St. Louis, Missouri,
United States
The first experiment was unintentional and a mistake. The original experiment was to utilize ClRhPh 3, a known catalyst,
for conversion of SiH to SiOR (alcoholysis). Although successful, not only was the alkoxysilane obtained but also the
disiloxane which was not a reported product. With considerable effort, conditions were developed that eliminated the
disiloxane and hydride terminated disilane and trisilane oligomers were obtained from PhMeSiH2. The next stage was
initiated by a connection between two entirely different papers and led to the development of a simple route to a Ti or Zr
catalyst system that was not plagued by oxygenation of Si-Si bonds in the product. Aspects of the coupling reactions of
secondary and primary silanes were studied for about 17 years. Extension of dehydrocoupling to other main group
elements will be briefly addressed.
INOR 414
Interplay between theory and experiment in investigations of organo-actinide complexes: A retrospective
Philip J. Hay, [email protected]. Department of Chemistry and Biochemistry, University of Colorado, Golden,
Colorado, United States
Organoactinide complexes with N-containing ligands exhibit a variety of bonding schemes utilizing the 5f and 6d orbitals of
the metal center. Illustrations are presented of the synergy between synthesis, characterization and theory in
investigations of the properties of organoactinide complexes. The bonding, electronic properties and reactions of Th and
U complexes involving imido, ketimido, hydrazonato and pyridine ligands have been examined using theoretical
approaches employing density functional theory (DFT).
INOR 415
Covalency in the actinides probed with ligand K-edge X-ray absoprtion spectroscopy
Richard L. Martin, [email protected]. MS B214 Theoretical Div, Los Alamos Natl Lab, Los Alamos, New Mexico, United
States
The presence or absence of significant participation in chemical bonding by the forbitals in actinide materials has been a
subject of debate for many years. In this talk, I will discuss a relatively direct probe of actinide involvement in bonding,
ligand K-edge Xray absorption spectroscopy. Experimental and theoretical investigations for a number of actinide
complexes and solids will be presented and compared with the analogous transition metal complexes. The evidence for forbital — ligand bonding interactions, their origin, and the ramifications for actinide electronic structure will be discussed.
INOR 416
Small molecule activation by complexes of low-valent f elements
Marinella Mazzanti1, [email protected], Jacques Pécaut2, Clement Camp2, Victor Mougel2, Julie Andrez1. (1)
ISIC, EPFL, Lausanne, Switzerland (2) CEA, Grenoble, France
Complexes of low-valent f-elements and of uranium in particular are excellent candidates for small molecule activation.
Differing sterical and electronic environments at the U(III) and Ln(II) centers have a critical impact on the geometry,
stability and reactivity of the reduction products. Careful tuning of the ligand is also essential to promote two-electron
transfer which is rare in U(III) chemistry. Notably, bulky siloxide ligands can be used to isolate stable U(III) complexes
which act as two-electron reducing agent in the reaction with a variety of small molecules such as CS2, CO2 and azides,[1]
chalcogenides and reduce toluene to afford arene complexes. Moreover, the sterical demand and electron-rich
coordination environment of homoleptic siloxide complexes of Eu(II) and Yb(II) leads to the reduction of azobenzene,
carbon disulphide and carbon dioxide and the ready release of the reduction products, a prerequisite for the
implementation of catalytic cycles.[2] Finally, siloxide ligands lead to the formation of heterobimetallic complexes enabling
the multimetallic cooperativity in uranium mediated reduction of carbon dioxide. [3] The redox chemistry of f element
complexes with siloxides and other bulky ligands will be presented together with the structure and properties of original
compounds.
[1] C. Camp, J. Pécaut and M. Mazzanti, J. Am. Chem. Soc. 2013, 135, 12101. [2] J. Andrez, J. Pécaut, P-A. Bayle, M.
Mazzanti Angew. Chem. Int. 2014, 53, 10448– 10452.
[3] O. Cooper, C. Camp, J. Pécaut,, C. E. Kefalidis, L. Maron and M. Mazzanti, J. Am. Chem. Soc. 2014, 136, 6716–6723.
INOR 417
Selective transformations of organic vompounds mediated by transition metal complexes
Robert G. Bergman1,2, [email protected]. (1) Chemistry, University of
California, Berkeley, Berkeley, California, United States (2) Chemical Sciences, Lawrence Berkeley National Laboratory,
Berkeley, California, United States
Many stoichiometric and catalytic reactions are now known in which metal complexes mediate the synthesis of new
organic compounds. These processes have been used to convert simple organic compounds into more complex
functionalized materials, in many instances with substantial selectivity. Mechanistic experiments have played an important
part in bringing us to the current understanding of these transformations, providing rational ways to improve them, and
guiding the development of new reactions. The content of the lecture will be chosen from exploratory and mechanistic
research that has been carried out most recently. Examples will be taken from studies focused on the activation of
carbon-hydrogen and carbon-heteroatom bonds in organic compounds or organic and organometallic reactions that take
place in the cavities of self-assembled clusters.
INOR 418
Supramolecular chemistry of anions: Organic, inorganic and biological studies
Kim R. Dunbar, [email protected]. Texas AM Univ, College Station, Texas,
United States
Self-assembly of metal ion complexes harnesses the power of directional bonds between metals and organic molecules to
promote the formation of metallosupramolecular architectures. The focus of this work is to gain a deeper understanding of
the role and strength of a newly recognized player in supramolecular chemistry, namely anion interactions with aromatic
organic molecules, dubbed anion-π interactions. Our approach is to use nitrogen-containing molecules with
electropositive tetrazine rings. These ligands produce unusual molecular polygons that are highly stable in solution but
which exhibit remarkable flexibility that allows them to be easily converted to other ring sizes, reactivity that is governed by
the anion. Chemical reactions triggered by the sequestration of anions can be used to alter the physical and chemical
properties of the compounds, a concept that has important implications for the fundamental reactivity of molecules based
on weak interactions. Collective data from solid-state, solution, gas phase and computational studies are being used to
assess the strength of anion-pi forces and to assist in the prediction of structures.
One application of this knowledge is the design of large polyhedra by using the fivemembered ring molecules as building
blocks. Another topic that is being tackled is how enzymes may employ anion-pi interactions to govern the
stability/reactivity of an active site. This concept is being applied to understanding the inhibition of malate synthase for
improved tuberculosis drugs. References:
(1) Anion Template Effect on the Self-Assembly and Interconversion of
Metallacyclophanes. Cristian Saul Campos-Fernández, Brandi L. Schottel, Helen T.
Chifotides, Jitendra K. Bera, John Bacsa, John M. Koomen, David H. Russell and Kim
R. Dunbar J. Am. Chem. Soc. 2005, 127, 12909-12923.
(2) Anion-π Interactions: A Tutorial Review. Brandi L. Schottel, Helen T. Chifotides and Kim R. Dunbar, Chem. Soc. Rev.,
2008, 37, 68–83. (web release date: September 13, 2007).
(4)
The pi-Accepting Arene HAT(CN)6 as a Halide Receptor through Charge Transfer: Multisite Anion Interactions
and Self-Assembly in Solution and the Solid State. Helen Chifotides, Brandi Schottel and Kim R. Dunbar, Angew. Chem.
Int. Ed., 2010, 49, 72027207.
Chifotides, Michael Shatruk and Kim R. Dunbar, Chem. Commun., 2011, 47, 12604– 12606.
(5)
Anion-pi Interactions in Supramolecular Architectures. Helen T. Chifotides and Kim R. Dunbar, Acc. Chem. Res.,
2013, 46, 894–906.
INOR 419
Technetium halide chemistry
Alfred P. Sattelberger1,3, [email protected], Frederic Poineau3, Erik V. Johnstone3, William M. Kerlin3, Christos
Malliakas2,1, Paul M. Forster3, Ken
Czerwinski3. (1) Argonne National Laboratory, Lemont, Illinois, United States (2)
Chemistry, Northwestern University, Evanston, Illinois, United States (3) Chemistry,
University of Nevada Las Vegas, Las Vegas, Nevada, United States
Almost every element in the periodic table has well-defined halide chemistry. Technetium, the first radioelement, is a
notable exception. Prior to 2008, only 3 binary halides of technetium had been reported, viz., TcF 6, TcF5 and TcCl4. These
compounds were prepared almost 60 years ago from the reactions of the metal with F 2 or Cl2. Since 2008, we have
synthesized and characterized an additional 6 binary halides, including two polymorphs of both TcCl 3 and TcCl2, TcBr4,
TcBr3 and TcI3, and several related cluster compounds. These new halides can be binned into one of three categories: (1)
those that have molybdenum and/or ruthenium analogues, (2) those that have rhenium analogues and (3) those for which
no analogues with neighboring elements currently exist. The synthetic routes to the new halides and their relationship to
molecular technetium systems will be described. Solid-state structures, thermal stabilities, and selected aqueous and nonaqueous chemistry will be discussed. The synthesis of these new halide compounds opens up exciting new opportunities
for exploring the synthetic and mechanistic chemistry of low-valent technetium, as well as the possibility of new
applications for the nuclear fuel cycle.
INOR 420
Computational actinide chemistry: Searching for understanding and holy grails
Bruce E. Bursten, [email protected]. Chemistry, University of Tennessee, Knoxville,
Tennessee, United States
Some aspects of the authors' contributions in computational actinide chemistry will be presented with a particular
emphasis on linkage to Professor F. Albert Cotton. Areas of emphasis will include novel actinide-containing molecules,
some of which exist only because of the efforts of this year's recipient of the F. Albert Cotton Award in Synthetic Inorganic
Chemistry.
INOR 421
Reinventing natural product discovery
Doug Mitchell, [email protected]. Chemistry 345 RAL, University of Illinois, Urbana, Illinois, United States
Natural products have been, without question, the most prolific source of all medicines.
With the advent of massively parallel DNA sequencing, it has become apparent that Nature’s capacity to synthesize
complex molecules far exceeds those that are known. With our knowledge of natural product chemical space so
incomplete, the discovery of new natural products with unique structures and activities will undoubtedly lead to improved
and entirely new medicines. With this in mind, our group focuses on elucidating the biosynthesis, structure, and function of
novel natural products. This talk will highlight three successful natural product discovery strategies that have emerged
from advances in genome sequencing, bioinformatics, biosynthesis, and bioconjugation. Presented as case studies, this
talk will cover our recent discovery of the antibiotics plantazolicin, cyclothiazomycin C, and streptomonomicin.
INOR 422
Metals and Immunity
Elizabeth M. Nolan, [email protected]. MIT Department of Chemistry, Cambridge, Massachusetts, United States
First-row transition metal ions are essential nutrients for all organisms. Metal-ion withholding is one accepted mechanism
of innate immunity used by the vertebrate host to prevent microbial replication. In this strategy, the host employs an
arsenal of metalchelating proteins to limit the bioavailability of nutrient metals such as Mn(II), Fe(II) and Zn(II) at sites of
infection. Human calprotectin is an abundant metal-sequestering protein that is produced and released by neutrophils. It
inhibits the growth of a broad spectrum of bacteria and fungi by depriving these organisms of nutrient metals. Calprotectin
exhibits remarkable biological coordination chemistry. It houses six metalbinding sites per S100A8/S100A9 heterodimer.
Each S100 submit contains two EFhand domains for Ca(II) ions, and two sites for transition metals form at the
S100A8/S100A9 interface. On the basis of biochemical and biophysical studies, we present a working model whereby
calprotectin uses Ca(II) ions to enhance its capacity to sequester transition metals and thereby compete with invading
microbes for these important nutrients.
INOR 423
Synthetic cluster models of the biological oxygen evolving catalyst from photosystem II
Theodor Agapie, [email protected]. California Institute of Technology, Pasadena, California, United States
Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but their roles are currently not
well understood. With current schemes of energy conversion involving water oxidation and dioxygen reduction, a detailed
understanding of these systems is imperative for the rational development of practical catalysts. Targeting synthetic model
clusters of these catalysts, multinucleating ligands were developed for Earth abundant first-row transition metals (Mn2+,
Fe2+, Co2+, Ni2+, Cu2+, Zn2+). Trimetallic complexes were utilized as precursors to more elaborate metal oxide clusters.
Tetranuclear complexes displaying Mn4, Mn3Ca and other Mn3M motifs with varied number of bridging oxo ligands were
synthesized. The reduction potentials of these clusters span a window of over 1 V. With the pKa of the redox-inactive
metalaqua complex as a measure of Lewis acidity, structurally analogous series of clusters display linear dependence
between reduction potential and acidity. These findings provide a general strategy for tuning the clusters over a wide
range of potentials and reactivity modes. Implications for the function of biological and artificial oxygen evolving catalysts
will be discussed.
INOR 424
Biosynthesis and tailoring of acyl peptidic siderophores
Alison Butler1, [email protected], Michelle P. Kem1, Hiroaki Naka2, Hannah K.
Zane1, Margo G. Haygood2. (1) Department of Chemistry & Biochemistry, University of
California, Santa Barbara, Santa Barbara, California, United States (2) Institute of
Environmental Health, Oregon Health & Science University, Portland, Oregon, United
States
Iron is essential for microbial growth. Many bacteria growing aerobically in low iron environments produce siderophores to
sequester iron(III) and facilitate its uptake and transport. While hundreds of siderophore structures are known, the
prevalence of new acyl peptidic siderophores is increasing. In some cases acyl peptidic siderophores are produced as
suites, with variation in the nature of the fatty acid for a given headgroup which coordinates Fe(III). In other cases, an acyl
peptide is formed as an intermediate along the route to the biosynthesis and release of an unacylated siderophore. We
have been interested in the biosynthesis of acyl siderophores and the tailoring reactions which hydrolyze the fatty acid
during different phases of biosynthesis or growth. An acyl ligase may be a component of the first nonribosomal peptide
synthetase (NRPS) that initiates biosynthesis of the siderophore, or the acyl ligase may be external to the biosynthetic
gene cluster, such as in the biosynthesis of the amphi-enterobactins produced by the bioluminescent marine bacterium
Vibrio harveyi BAA-1116. Similar to the presence of an acyl ligase which incorporates a fatty acid, generally as an
initiation of siderophore biosynthesis, other acylases release the fatty acid during biosynthesis of some siderophores, or
during later stages of bacterial growth subsequent to the release of acyl siderophores; we are investigating the
significance of these N-terminal nucleophilic (NTN) hydrolase enzymes in modifying acyl siderophores.
INOR 425
Glycocalyx engineering toward probing cancer glycome evolution
Carolyn R. Bertozzi, [email protected]. Univ of California, Berkeley, California, United
States
While altered glycosylation patterns have long been identified as hallmarks of cancer, their functional significance with
respect to tumor progression are not well understood. Two examples are overexpression of mucin glycoproteins (densely
glycosylated cellsurface molecules with unusual physical properties) and hypermodification of glycoproteins with the
terminal sugar sialic acid. These glycosylation phenotypes are found on numerous cancer types with highly varied
underlying driver mutations and their magnitude tends to correlate with tumor aggressiveness. To test hypotheses
regarding the functional significance of cancer glycomes, we developed an approach to engineer the cell surface
“glycocalyx” with chemically defined glycopolymers that emulate cancerassociated structures. Using living polymerization
and chemoselective ligation chemistries, we synthesize glycopolymers functionalized with a biophysical probe on one end
and a lipid capable of membrane insertion on the other. These biomimetic structures can be displayed on live cell
membranes where they acquire functions analogous to natural mucin glycoproteins. Our work using this platform
suggests that hypersialylation protects tumor cells from innate immune surveillance, whereas mucin upregulation alters
the physical properties of the glycocalyx so as to promote focal adhesion formation and signaling. Both glycophenotypes
can thus be understood as evolutionary adaptations of cancer cells under various selective pressures.
INOR 426
Second-sphere tuning of enzymatic activity in noncanonical heme oxygenase
Matthew D. Liptak, [email protected], Amanda B. Graves, Cheryl L.
Lockhart. Department of Chemistry, University of Vermont, Burlington, Vermont, United
States
Two second-sphere amino acids, Trp66 and Asn7, are essential for Mycobacterium tuberculosis MhuD- and
Staphylococcus aureus IsdG-catalyzed aerobic degradation of heme to mycobilin and staphylobilin, respectively, but it
has remained unclear how these residues tune the heme substrate electronic structure to promote catalytic porphyrin
oxygenation and cleavage. A combined experimental and theoretical approach has been employed to address this issue
where optical and magnetic resonance spectroscopies were used to probe the active site electronic structure and
quantum mechanical calculations were utilized to provide a spectroscopically-validated framework for interpretation of
enzyme activity data. In cyanide-inhibited MhuD, substitution of Trp66 for a smaller amino acid decreased the rate of
heme degradation, as previously observed for S. aureus IsdI, but triggered a redshift of the Soret band, in contrast to the
blueshift previously reported for IsdI. In azide-inhibited IsdG, substitution of Asn7 by an alanine altered the circular
dichroism intensity and magnetic circular dichroism band energies, suggesting that a strong hydrogen bond exists
between the Asn7 side-chain and the iron-ligating atom of a π-donor ligand. Spectroscopicallyvalidated density functional
theory modelling of the heme electronic structures suggests that Trp66 distorts the porphyrin ligand from planarity due to
steric interactions, Asn7 orients the distal ligand through a hydrogen bonding interaction, and both second sphere
interactions trigger spin density delocalization onto the heme meso carbons. Ultimately, from these results a picture is
emerging whereby Trp66 and Asn7 work in concert to both geometrically and electronically prepare the heme substrate
for catalytic oxygenation by MhuD and IsdG.
INOR 427
Pif97 as a framework protein for association of organic-inorganic layers of nacre
So Yeong Bahn3, [email protected], Byung Hoon Jo2, Yoo Seong Choi1, Hyung
J. Cha2. (1) Department of Chemical Engineering, Chungnam National University,
Daejeon, Korea (the Republic of) (2) Department of Chemical Engineering, POSTECH,
Pohang, Korea (the Republic of) (3) School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang,
Korea (the Republic of)
The nacreous layer of molluscan shells consists of highly organized structure with calcium carbonate aragonite crystals,
which provides exceptional strength and toughness compared to pure mineral calcium carbonate. It has been assumed
that assemblies of proteins and polysaccharides were shown to induce and regulate this ordered aragonite formation, and
acidic matrix proteins named Pifs have been recently regarded as essential components for normal growth of nacre of
pearl oyster Pintada fucata. Here, we investigated features of N-terminal half of Pif, Pif97, which is posttranslationally
derived from a single Pif polypeptide. In this aspect, pif97 gene was genetically redesigned, and recombinant Pif97 protein
was successfully expressed and purified in Escherichia coli system. The binding properties of the recombinant Pif97 to
both organic chitin and inorganic calcium ion and mineral phase were investigated based on properties of naturally
extracted Pifs from P. fucata. Effect of complex mixture of recombinant Pif97 and polysaccharides was also examined in
in vitro calcium carbonate crystallization. We expect that the recombinant Pif97 protein can also regulate in vitro
biomineralization for production of calcium carbonate with superior mechanical properties. This study can also provide
clue to understand biomineralization mechanism of nacre.
INOR 428
Model compounds of [NiFe]-hydrogenase in the Ni-SIa and Ni-L states
Geoffrey M. Chambers1, [email protected], Thomas B. Rauchfuss 2, Edward J. Reijerse3, Katharina Weber3,
Wolfgang W. Lubitz3. (1) Chemistry, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States (2)
A131CSSL Box 60-6, University of Illinois, Urbana, Illinois, United States (3) Max Planck Institute for Chemical Energy
Conversion, Muelheim, Germany
While many [NiFe]-hydrogenase model complexes have been synthesized, only the
Ni(II)Fe(II)(μ-H) state, known as Ni-R, has been accurately modeled. We present here a model system that is the first
example of complexes akin to the Ni(II)Fe(II) and Ni(I)Fe(II) states of [NiFe]-hydrogenase, known as Ni-SIa and Ni-L
respectively. The triple-decker sandwich compound [Cp3Ni2]BF4 (Cp−=cyclopetadienide) reacts with Fe(pdt)(dppe)(CO)2 to
yield the heterobimetallic compound [CpNi(pdt)Fe(dppe)CO]BF 4 ([1]BF4) with concomitant elimination of nickelocene
(Figure 1). Compound [1]BF4 is reduced upon treatment with cobaltocene to yield the neutral, mixed-valent complex
CpNi(pdt)Fe(dppe)CO (1). EPR spectroscopic studies of 1 reveal strong coupling to the cyclopentadienyl protons and
weak coupling to the phosphorus center, indicating 1 is a nickel(I) paramagnet. Additionally, Mössbauer spectroscopy
suggests the iron centers in
[1]BF4 and 1 are best described as low-spin iron(II). Compound 1 reacts with stoichiometric acid to generate [1]+ and 0.5
equiv. of H2, indicating that this model system is formally a proton reduction catalyst (Figure 2).
Figure 1. Reaction of [Cp3Ni2]BF4 with Fe(pdt)(dppe)(CO)2 yielding nickelocene and [1]BF4.
Figure 2. Proposed catalytic cycle for proton reduction.
INOR 429
Evolution of thioether S-ligated primary CuI/O2 adducts: The 1st example of CuIIsuperoxo species with enhanced
reactivity
Jung Yoon C. Lee1, [email protected], Sunghee Kim1, Ryan Cowley2, Jake W.
Ginsbach2, Maxime Siegler1, Edward I. Solomon2, Kenneth D. Karlin1. (1) Department of
Chemistry, Johns Hopkins University, Baltimore, Maryland, United States (2)
Department of Chemistry, Stanford University, Stanford, California, United States
A cupric superoxo species has been proposed as the most reactive intermediate in peptidylglycine-α-hydroxylating
monooxygenase (PHM) and dopamine-βmonooxygenase (DβM), which can activate the C–H bond of the peptide prohormone and dopamine, respectively. These enzymes possess a “noncoupled” dicopper active site and the methionine Sligated CuM center known to bind O2 and substrate. A crystal structure reveals dioxygen bound to CuM in an end-on
superoxo fashion. Although the thioether ligand must play a critical role in determining the electronic structure and
functions of CuM site leading to C-H bond activation, the precise role of Met coordination has yet to be fully understood.
Thus, to elucidate the fundamental CuI/O2 chemistry and role of sulfurMet ligation in copper monooxygenases, we have
generated a new synthetic mononuclear Cu II superoxide species, (DMAN3S)CuII(O2•–), mimicking the initial CuI/O2 adduct at
the PHM active site. The characterization comes from UV-vis and resonance Raman spectroscopic evidence. The
influence of Sthioether-atom ligation in the CuII superoxo complex have been examined through CuI/O2 adducts possessing
analog ligands without sulfur. Enhanced reactivity towards both O-H and C-H substrates will be also discussed and can
be attributed to the S-ligation, in comparison to close analogues [(L)CuII(O2•–)]+, where L contains only nitrogen donor
atoms. This study will contribute significantly to the elucidation of the fundamental CuI/O2 chemistry and role of sulfurMet
ligation in copper monooxygenases.
INOR 430
Fundamental reactivity studies of hydrogen sulfide with metalloporphyrins
Daniel J. Meininger1, [email protected], Hadi Arman1, Zachary J.
Tonzetich2. (1) Chemistry, University of Texas at San Antonio, San Antonio, Texas,
United States (2) Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas, United States
Hydrogen Sulfide (H2S) has been subject of great interest since the discovery of its role as an important signaling
molecule in biological systems. It has been shown that H2S and its derivatives (such as HS−) are capable of reacting with
the metal centers in heme containing proteins. In order to understand the mechanisms of these interactions in greater
detail, we have prepared a variety of synthetic iron porphyrinate species and investigated their reactions with H 2S, HS−,
and other sulfur-containing molecules. The chemistry of H2S with both iron(II) and iron(III) porphyrinate systems will be
discussed along with reactions of other biologically important small molecules such as nitric oxide.
INOR 431
Dioxygen activation under ambient conditions using bio-inspired manganese(II) complexes to generate midvalent oxidants for catalytic O–H bond oxidations
Gayan B. Wijeratne1, [email protected], Andrew D. Burr1, Briana Corzine2, Timothy A. Jackson1. (1) Chemistry, The
University of Kansas, Lawrence, Kansas,
United States (2) Biochemistry, Vanderbilt University, Nashville, Tennessee, United States
Manganese-dependent dioxygen activation under mild conditions is common to a variety of biological enzymes including
lypoxygenase and homoprotocatechuate 2,3dioxygenase. In spite of these enzymatic examples, biomimetic manganese
model complexes that can activate dioxygen are rare, and designing such compounds continues to be a challenging task.
Furthermore, aerobic substrate oxidation using manganese catalysts is of great significance in developing green,
inexpensive metal oxidants for industrial applications. The main focus of this work is in designing novel bioinspired Mn(II)
species that are capable of activating dioxygen under ambient conditions, and using these compounds to gain insight into
O2 activation mechanisms and substrate oxidation pathways using O 2 as the oxidant. We report a series of monomeric
Mn(II) complexes supported by anionic ligands with axial amido coordination that activate dioxygen in solution to generate
mid-valent MnIII–OR compounds in quantitative yields. These Mn(III) complexes are extremely stable, and exhibit unique
kinetic properties in the oxidation of weak O–H bond substrates. The kinetic and thermodynamic properties of these midvalent oxidants and the prospects of this chemistry to be utilized in devising environmentally friendly O–H activation
catalysts are discussed.
INOR 432
Short peptides self-assemble to produce catalytic amyloids
Caroline M. Rufo1, [email protected], Yurii S. Moroz1, Olesia V. Moroz1, Jan Stoehr4,
Tyler A. Smith 1, Xiaozhen Hu5, William F. Degrado2, Ivan V. Korendovych3. (1)
Chemistry , Syracuse University , Syracuse, New York, United States (2) UCSF, San
Francisco, California, United States (3) Syracuse University, Syracuse, New York,
United States (4) Institute for Neurodegenerative Diseases and Department of
Neurology, University of California San Francisco , San Francisco , California, United
States (5) Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States
Metalloenzymes rely on their well-defined secondary structures to achieve remarkable selectivity and efficiency. We have
designed a series of short 7-residue peptides that self-assemble to create amyloid-like fibrils, which are capable of
catalyzing ester and phosphoester hydrolysis using zinc as a cofactor. The catalytic efficiency of the fibrils is on par with
those of computational designs and even natural enzymes. Experimental (UV-vis, fluorescence, TEM, etc.) and
computational modeling studies suggest that the zinc ion is coordinated to three histidine residues, an arrangement
similar to the one found in various hydrolytic enzymes (Fig. 1A). A water molecule, whose pKa is modulated through
coordination to zinc, occupies the fourth coordination site and facilitates hydrolysis.
The biomimetic self-assembly approach we used employed makes it possible to probe many different coordination
spheres by mixing different peptides (Fig. 1B). We demonstrate that different peptides synergistically interact upon selfassembly to further improve catalytic efficiency. This is the first demonstration that amyloid-like assemblies catalyze not
only their own assembly but also chemical reactions as well. 1
1. Rufo, C. M., Moroz, Y. S., Moroz, O. V., Stöhr, J., Smith, T. A., Hu, X., DeGrado, W. F., & Korendovych, I. V. Nat.
Chem. 2014, 6, 303.
Figure 1 A) A computationally derived model of the packed hydrophobic core formed from fibrils. B) Schematic representation of the
self-assembly of a mixture of peptides in the presence of metal.
INOR 433
New insights in the chemistry of nickel in urease
Luca Mazzei1, Stefano Benini2, Stefano Ciurli1, [email protected]. (1) Pharmacy and Biotechnology, University of
Bologna, Bologna, Bologna, Italy (2) Science and Technology, University of Bolzano, Bolzano, Bolzano, Italy
Urease is the most efficient enzyme known to date, and this efficiency relies on the presence of an active site containing
two Ni(II) ions. The structural properties of the enzyme in the native state and in complex with several inhibitors have been
the focus of our studies in the past several years. Recently, we determined the structural and kinetic determinants of
urease inhibition by fluoride, dimethylsulphoxide, phosphite and other small molecules. These results shed new light on
the chemistry of the metal ions in the active site of the enzyme.
INOR 434
Understanding the reaction mechanism of the tungstoenzyme, acetylene hydratase
Matthew A. Cranswick1, [email protected], E. Christine Vergunst1,
Brooklynn Trujillo1,2. (1) Department of Chemistry, Colorado State University - Pueblo, Pueblo, Colorado, United States (2)
South High School, Pueblo, Colorado, United
States
Acetylene hydratase (AH) is unique among the Mo/W family of enzymes. For instance, AH is the only known nonredox
Mo/W enzyme, it is the only known enzyme to use C2H2 as its native substrate, and these organisms use C2H2 as their
sole carbon and energy source, for which AH catalyzes the first step in carbon and energy acquisition. To date, the
reaction mechanism of AH is poorly understood and its reaction mechanism has been explored computationally, but not
experimentally. Of these computationally proposed reaction mechanisms, two of the three invoke the formation of a
W IV(η2-C2H2) complex. To better understand the reaction mechanism, we have used a known oxotungsten(IV)
bis(dithiolene) complex to model the active site of AH and determine if acetylene derivatives (RC 2R’) will coordinate the
tungsten center, as proposed by these computational models. The coordination of these acetylenic ligands , and the
identity of the oxygen-donor ligand and its role in substrate coordination will be presented.
INOR 435
Tethered C,N,S ligands containing an iron-carbamoyl motif as synthetic models of mono-iron hydrogenase
Michael J. Rose, [email protected], Gummadi Durgaprasad. Dept of Chemistry, University of Texas at Austin,
Austin, Texas, United States
The enzyme mono-iron hydrogenase (mono-[Fe] H2ase) catalyzes a hydride transfer directly from dihydrogen (H2) to the
organic substrate tetrahydromethenylmethanopterin
(H4MPT+), which acts as a C1 carrier in the methanogenic CO2→CH4 metabolic cyle. This hydride transfer is just one step
in the Fe-dependent (i.e. Ni-free) pathway of CO2 utilization. The active site contains several unique ligands, including an
iron-acyl unit, a pyridone-N donor (part of a GMP-based cofactor), and a cysteine thiolate. In this work, we have
assembled a chelating ligand that facilitates iron-carbon bond formation, as well as a bound pyridine-N and sulfur donor
(thioether). This results in a highly stable platform to study substitution reactions, as well as base-activation of the ligand
framework (carbamoyl NH). In the resulting complex [(CNS)Fe(CO)2(Br)], facile substitution of bromide leads to binding of
various L (PPh3, tBuiNC, pyr, MeCN) in the diamagnetic, structurally characterized cations of type [(CNS)Fe(CO) 2(L)][X] [X
= BF4, BArF]. Substitution of a single CO ligand using Me3NO, however, affords paramagnetic complexes of type
[(NCS)Fe(CO)(L)]0/+ (L = Br, PPh3). Investigations into ligand-metal cooperativity via deprotonation of the carbamoyl NH
unit (tBuOK, THF) result in desulfurization of the ligand, forming the cyclometalated product
[(CNC)Fe(CO)(PPh3)2]. This pincer-type complex is one of very few mononuclear, cyclometalated Fe(II) reported in the
literature, and the only one that exhibits the ironacyl motif. The implications of these reactivities for understanding the role
of this unique set of donors in the mono-[Fe] hydrogenase active site will be discussed.
INOR 436
Family of starch-active polysaccharide monooxygenases
Van V. Vu1, [email protected], William T. Beeson3, Daniel Suess4, Elise A. Span5,
Erik R. Farquhar2, R. David Britt4, Michael A. Marletta1. (1) Chemistry, The Scripps Research Institute, La Jolla, California,
United States (2) NSLS Building 725A-X3,
Brookhaven National Lab, Upton, New York, United States (3) Chemistry, University of
California-Berkeley, Berkeley, California, United States (4) Chemistry, University of
California-Davis, Davis, California, United States
Polysaccharide monooxygenases (PMOs) have recently been shown to play an essential role in the oxidative degradation
of crystalline cellulose and chitin. These enzymes activate O2 using a Type 2 mononuclear copper active site contained
within a flat substrate-binding surface to hydroxylate the C-H bonds of the glycosidic linkage, resulting in the cleavage of
hydroxylated linkage. The copper active site consists of two conserved histidine ligands in a motif termed histidine brace.
The N-terminal histidine
ligand in fungal PMOs is methylated at the ε position. Using this conserved histidine brace motif, putative PMO families
were found to utilize starch and other
polysaccharides as substrates. They do not act on chitin or cellulose. We subsequently expressed and characterized
NCU08746, a member of the starch-active PMO family that contains a predicted starch-binding domain in addition to a
putative N-terminal PMO domain. Activity assays showed that NCU08746 is a copper-dependent monooxygenase that
oxidatively cleaves starch substrates. XAS, EPR, and ESEEM studies indicated that the copper active site in NCU08746
is similar to that in cellulose- and chitin-active PMOs. These results suggest the existence of a PMO superfamily with a
much broader range of potential substrates. The starch-active PMO family provides a new perspective on studies of
starch metabolism and has potential applications in food and starch-based biofuel industries.
INOR 438
Biochemical and molecular modelling studies of the interaction of organometallic ruthenium complexes
containing thiosemicarbazones or curcuminoids as ligands with DNA and proteins
Floyd A. Beckford, [email protected], Kinsey L. Hall, Kelsey R. Webb. Natural
Sciences, University of Virginias College at Wise, Wise, Virginia, United States
We have used thiosemicarbazones and [(aryl)hepta-1,6-diene-3,5-dione]s
(curcuminoids), as ligands in the synthesis of organometallic ruthenium complexes of the type [(η 6-arene)Ru(ligand)Cl]
where arene = benzene, p-cymene or 1,4,7trithiacyclononane ([9]aneS3). The thiosemicarbazone ligands were derived
from piperonal and 9-anthraldehyde while the curcuminoids were synthesized from dimethylaminobenzaldehyde and
ferrocene carbaldehyde. The complexes have been characterized by elemental analyses and spectroscopic methods. The
interaction of the thiosemicarbazone complexes with topoisomerase II have been investigated by gel electrophoresis and
molecular docking. The curcuminoid complexes have been investigated by molecular modelling. Initial biophysical studies
investigations of reactions with DNA have also been carried out.
INOR 439
Formation and characterization of Langmuir-Blodgett films of lipid rafts
Donn L. Calkins1, [email protected], Ilya Kuznetsov1, Estela Magallanes1, [email protected],
Carmen Menoni2, Dean Crick4,3, Debbie C. Crans1,3. (1) Chemistry, Colorado State University, Fort Collins, Colorado,
United States (2) ECE,
Colorado State University, Fort Collins, Colorado, United States (3) Cell and Molecular
Biology, Colorado State University, Fort Collins, Colorado, United States (4)
Mycobacteria Research Laboratories, Colorado State University, Fort Collins, Colorado,
United States
Lipid rafts play a vital role in the function of cell membranes, including signal transduction, protein and lipid modification
and optimization of protein function. The lipid raft hypothesis posits that phospholipids, in the presence of cholesterol and
sphingolipids, can condense to form organized lipid domains known as “rafts.” The raft hypothesis has become a popular
model among cell biologists to explain a variety of important cellular processes. However, investigating raft formation and
function has proven to be challenging due to their transient nature and uncertainties regarding their size and composition.
Many of these difficulties can be reduced or minimized by the deposition of thin lipid films on solid substrates which are
more tractable for analysis. These multi-layer films, known as Langmuir-Blodgett (LB) films, can be successfully
generated using many different combinations of membrane components. We worked on preparing a series of samples
consisting of a number of lipid layers deposited on Indium Tin Oxide (ITO) float glass slides. One series of samples were
based on simple lipids such as palmitic acid and the other on combinations of 1-palmitoyl-2-oleoyl-sn-glycero3phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1,2-dipalmitoyl-sn-glycerol3-phosphocholine (DPPC) with cholesterol and sphingomyelin. With the membrane analogue essentially fixed in time and
space, therefore, techniques such as time of flight secondary ion mass spectrometry (ToFSIMS) can be used to image
these ordered lipid domains in great detail.
INOR 440
Functional model of the first and second coordination spheres of type 2 copper nitrite reductase
Gerard Rowe3, [email protected], Shelby L. Behnke4, Sarah Weaver5, Emma
Foerster3, Mark Bezpalko2, Bruce M. Foxman1. (1) Brandeis Univ, Waltham,
Massachusetts, United States (2) Chemistry Department, Brandeis University, Waltham,
Massachusetts, United States (3) Chemistry and Physics, University of South Carolina
Aiken, Aiken, South Carolina, United States (4) Chemistry and Biochemistry, The Ohio
State Unviersity, Columbis, Ohio, United States (5) Chemistry, University of California Santa Cruz, Santa Cruz, California,
United States
A 1,4,7-triazacyclononane-based ligand containing a pendant benzoic acid group has been synthesized and complexed
with Cu(II) for use as a model of the active site of type-2 copper containing nitrite reductase. The inclusion of an acidic
functionality into this metal complex facilitates the catalytic reduction of nitrite in the presence of ascorbate at a pH of 6,
while the analogous ester form of the compound exhibits no catalytic activity in the same time regime under the same
conditions. Density functional theory calculations provide insight into the ability of the acidic functionality to interact with
and activate a copper-bound nitrite group.
INOR 441
Voltammetric studies of the Rieske protein
Kevin R. Hoke, [email protected], Robert J. Quarles. Department of Chemistry, Berry
College, Rome, Georgia, United States
The Rieske center is a 2Fe-2S cluster found in complex III of the mitochondrial respiratory chain. Its role is to transfer
electrons from the quinol:quinone pool to cytochrome c. A key feature of the active site is its two histidines that ligate one
of the iron atoms in the cluster. These histidines can be successively deprotonated with increasing pH, drastically lowering
the reduction potential. Furthermore, the pKa values for these histidines in the oxidized state are physiologically relevant.
We have used direct electrochemistry to measure the reduction potential for a soluble version of the Rieske protein from
T. thermophilus, as well as those for a series of mutants designed to perturb the reduction potential. For example
introduction of polar groups or a negative charge near the active site will stabilize the reduced form of the protein, thereby
raising the reduction potential. Full pH profiles and modeling were used to extract pKa values for the two histidines in both
the oxidized and reduced states. While most of our results correlate with similar work for the bovine version of the protein
(see Leggate and Hirst, Biochemistry, 44, 7048–7058), some puzzling differences exist, especially for the L135E mutation
near the active site. We will also describe a simple approach for performing electrochemical measurements on protein
samples of small volume.
INOR 442
X-ray crystallographic analysis of reduction potential mutants of the Rieske protein from Thermus thermophilus
Laura M. Hunsicker Wang, [email protected]. Chemistry, Trinity
University, San Antonio, Texas, United States
Rieske proteins are electron transport proteins involved in several important biological processes that include respiration
and photosynthesis. They have a [2Fe-2S] cluster ligated by 2 cysteines and 2 histidines. A series of mutants, which alter
the properties of the iron sulfur cluster in the Rieske protein from Thermus thermophilus, have been designed and
produced (L135E, L135R, L135A, and Y158F). The reduction potentials of these mutants have been measured and the
crystal structures of each solved to 2.1 Å or better. The overall structure of the proteins are very similar, however there are
changes near the [2Fe-2S] cluster. In addition, a double mutant has also been crystallized at 1.3 Å and will be used to
probe if the effects of the mutations are additive. These subtle changes in the protein underscore why the accompanying
structural studies are needed in conjunction with mutational studies.
INOR 443
Understanding functional tuning in binuclear non-heme iron enzymes through systematic variation of the
G4DFsc active site
Amanda J. Reig, [email protected], Sabrina Cimerol, Jenna Pellegrino, Rachel
Polinski, Kale A. Drost, Connor L. Kanya, Kristen Biernat, Katie O'Shea. Chemistry,
Ursinus Colelge, Phoenixville, Pennsylvania, United States
Binuclear non-heme iron enzymes exhibit a broad range of catalytic functions despite the similarities of their active sites.
To investigate the role of specific active site residues in tuning a particular function, we have created and characterized a
series of proteins with systematic active site perturbations using the de novo designed G4DFsc scaffold. The G4DFsc
protein is uniquely suited for such structure-function investigations due to its simplicity, stability, and ease of mutation.
While the original G4DFsc protein contains a 2-His/4-carboxylate metal-binding site, we have rationally redesigned the
active site to mimic those proteins in nature that contain higher numbers of carboxylates (rubrerythrins, symerythrin) or
higher numbers of histidines (AurF, FprA, MIOX). We have characterized the secondary structure, stability, and metalbinding capacity of these new proteins and investigated their ability to catalyze a range of O 2- and H2O2dependent
reactions. By comparing the spectroscopic and geometric properties of these structurally-similar but functionally distinct
proteins, we can gain molecular-level insight into the roles of charge and coordination number in tuning catalytic activity in
binuclear non-heme iron enzymes.
INOR 444
Homoleptic transition metal complexes of the 7-azaindolide ligand featuring κ1N1 coordination
Monica Kiewit1, [email protected], Zachary J. Tonzetich2. (1) Chemistry , University of Texas at San Antonio , San
Antonio, Texas, United States (2) Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas,
United States
Due to their prevalence and natural occurrence in many biological systems, the indole family of molecules has been the
subject of intense research for several decades. Although studied primarily as precursors for pharmaceutical
development, compounds of the indole family exhibit a number of unique properties, making them useful and highly
desirable in a variety of non-health related applications. In the context of transition metal coordination chemistry, one
subset of indole derivatives of particular interest is the azaindoles. This paper will describe our efforts to prepare the first
examples of homoleptic 7-azaindole complexes of the first row transition metals. New complexes of the type,
Na2[M(AzaIn)4] (AzaIn = anion of 7-azaindole), have been successfully synthesized and characterized for Mn, Fe, and
Co. Each complex displays tetrahedral geometry in the solid state with exclusive coordination through the pyrrolic nitrogen
(κ1-N1), an uncommon coordination mode for 7-azaindole with transition metals. The sodium cations in each complex are
coordinated to the pyridine groups of the azaindolide ligands rendering the overall compounds soluble in arene solvents.
The structure, spectroscopy, and reactivity of each complex will be discussed including efforts to prepare multi-metallic
compounds.
INOR 445
Coupling oxygen consumption with substrate oxidation in bacterial multicomponent monooxygenases
Stephen J. Lippard, [email protected]. Chemistry, Massachusetts Institute of
Technology, Cambridge, Massachusetts, United States
Bacterial multicomponent monooxygenases react with hydrocarbons, dioxygen, electrons, and protons at carboxylatebridged diiron centers to generate alcohols, epoxides, and phenols under mild atmospheric conditions. These enzyme
systems typically comprise a hydroxylase of 200 kDa or more molecular mass, a reductase containing flavin and 2Fe-2S
units, in some cases a Rieske protein, and a regulatory protein that couples the consumption of electrons with oxidation of
the hydrocarbon substrate. The soluble methane monooxygenase from Methylococcus capsulatus (Bath) is the flagship
enzyme of these systems, using methane as its sole source of carbon and energy. Through X-ray crystallographic, rapid
kinetic, and advanced EPR methods we have elucidated the general principles by which these systems avoid functioning
as NADH oxidases, serving instead as monooxygenases. The strategy differs from that of the related heme enzymes
cytochromes P450, which perform similar chemistry, as will be discussed. This work was supported by a grant from the
National Institute of General Medical Sciences.
INOR 446
Are metal-associated misfolded proteins involved in Alzheimer’s disease?
Mi Hee Lim, [email protected]. Chemistry, Ulsan National Institute of Sci. Tech., Ulsan, Korea (the Republic of)
Neurodegenerative disorders impose an enormous financial and emotional burden on patients, their families, and
communities. More than 24 million people worldwide have Alzheimer’s disease (AD), a devastating and fatal
neurodegenerative disease that remains poorly treated due to an incomplete grasp on the disease etiology. A key
neuropathological hallmark of AD is amyloid-β (Aβ) plaques in the brain. The mechanisms driving formation of these
protein aggregates and their causal link to dementia are still unclear. An additional observation in the AD brain is the
accumulation
of metal ions, which has been proposed to be associated with Aβ aggregates and neuronal death, yet relatively little is
known, further sustaining the controversy surrounding this aspect of the disease. Even through a large body of
continuously
reported literature regarding metal ions and Aβ species, direct connection of metal-Aβ interaction with AD onset and
development has been neglected in this field due to lack of appropriate tools and/or tactics. Therefore, we have developed
chemical tools and/or tactics that are capable of specifically targeting metal-associated Aβ species and modulating their
interaction and reactivity. Using our chemical tools, we have been able to regulate metal-induced Aβ aggregation and
neurotoxicity in vitro, in living cells, and in primary neurons, along with cognition improvement in the AD mouse model.
Here, our rational structure-based design principle and recent findings for chemical tools and tactics for investigating
metal-Ab chemistry and biology in AD and/or potential therapeutic agents for AD will be discussed.
INOR 447
Cephalopod-derived materials for photonic and protonic devices
Alon A. Gorodetsky, [email protected]. Chem Eng Mtrl Sci, University of California, Irvine, Irvine, California,
United States
Cephalopods are known as the chameleons of the sea – they can alter their skin’s coloration, patterning, and texture to
blend into the surrounding environment. These remarkable capabilities are enabled by unique proteins and selfassembled nanostructures found within cephalopod skin. I will discuss our work on new types of photonic and protonic
devices fabricated from naturally occurring materials found in cephalopods. Our findings hold implications for the next
generation of stealth and bioelectronics technologies.
INOR 448
Exploring the physiological role of selenium redox chemistry
Marisa C. Buzzeo, [email protected]. Dept of Chemistry, Barnard College, New
York, New York, United States
Selenium is a trace element in the human body, found primarily in the form of selenocysteine and selenomethionine.
Selenium-containing proteins, such as glutathione peroxidases and thioredoxin reductases, are known to play an integral
role in several physiologically regulated processes. Interestingly, evidence of a diselenide bond, resulting from the
oxidation of two selenocysteine residues, has not yet been found in mammalian systems and reports on synthetic
selenoproteins indicate that thioredoxin, the predominant cellular reductant, cannot fully reduce the oxidized product. We
seek to better understand the biological significance and potential applications of selenium’s intrinsic redox activity. Our
efforts thus far have focused on the electrochemical behavior of selenocystine under physiological conditions with parallel
analysis performed on the well-studied sulfur analogue, cystine.
INOR 449
Nucleic acids in quadruplexes
Fangwei Shao, [email protected]. Division of Chemistry and Biological Chemistry, Nanyang Technological University,
Singapore, Singapore
Two quadruplex structures, G-quadruplex and i-motif, are folded by guanine rich and cytosine rich sequences,
respectively. Quadruplex folding sequences for the two motifs are widely spreaded in human genome and exist in many
biological essential regions, such as telomere and promoters of oncogenes. Our group has explored the biochemical
features and applications of quadruplex DNAs to drug discovery, biosensing and nanotechnology.
G-quadruplexes, the major family of quadruplex DNA/RNA containing two or three layers of G-tetrads, are readily folded
under physiological concentrations of potassium and soldium cations. The biological and therapeutic significances of Gqaudruplexes are well appreciated and the use of small molecules that promote the formation and/or stabilize Gquadruplex (GQ) structures has become attractive approaches in anticancer drug discovery. 1 Herein, we report several
Pt(II) and Ru(II) complexes that show high binding affinity and excellent selectivity to GQ over duplex DNA. By varying the
coordination geometry and ligand structures, specific targeting to variety of GQ topological structures can be readily
achieved, which provides a promising approach to develop personal drug and disease specific anticancer therapeutics.2
I-motifs are quadruplex DNA strucutures assembled via semi-protonated cytosine base pairs under acidic pH. The rigid
four stranded structure and unique sensitivity to pH make i-motif an ideal scaffold for biosensing and bioimaging. Exciplex
formed by single thiazole orange (TO) and adenines in the dual loops of i-motif show large Stoke shifts over 90 nm and
pH-driven reversible modulation between fluorescence of TO monomer and exciplex. 3 Further application of i-motif as the
scaffold for assembling nanocluster is developed to image pH variation during endocytic pathway in live cells. 4 The
concept expands the library of stimuli-responsive DNA structures for constructing miniature plasmonic and fluorescence
sensors.
Reference
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Balasubramanian, L. H. Hurley and S. Neidle, Nat. Rev. Drug Discovery, 2011, 10, 261; (c) D. Yang and K. Okamoto,
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Chem., 2010, 2, 619.
2. Wang JT, Lu K, Xuan S, Toh Z, Zhang D, Shao F, Chem. Comm. 2013, 49, 4758.
3. Xu B, Wu X, Yeow E, Shao F, Chem. Comm. 2014 50, 6402.
4. Wang C, Du Y, Wu Q, Xuan S, Zhou J, Song J, Shao F, Duan H. Chem. Comm 2013, 49, 5739.
INOR 450
Photochemical dynamics of stacked perylenediimide assembly constructed on DNA
Tadao Takada, [email protected]. Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan
DNA has been utilized as a template or scaffold to place functional molecules on it in a well-defined arrangement through
covalent chemical modification or non-covalent interactions, and various kinds of DNA with an array of functional dyes
organized along the helix axis have been prepared. Here we show an effective way to organize and arrange
perylenediimide (PDI) molecules on DNA. We also report photochemical dynamics of stacked PDI assembly constructed
within π-stack array of DNA, studied by photoelectrochemical measurements and femto-second time-resolved transient
absorption experiments. It was found that the cofacially stacked PDI dimer and trimer in DNA strongly enhanced the
photocurrent generation compared to an isolated PDI molecule. Femto-second transient absorption experiments showed
that the excitation of the stacked PDI molecules in DNA led to the delocalization of a negative charge over the PDI
molecules generated by photo-induced charge separation, causing the formation of the long-lived charge-separated state
in the PDI dimer and trimer with a lifetime of a few ns. These results suggest that the stacked arrangement of functional
chromophores in the π-stacked array is essential for the hole/electron transfer pathway and formation of the long-lived
charge-separated state, enabling us to develop molecular optoelectronics based on the DNA sequence and structure.
INOR 451
Highly selective chemical processes for tailored electronic materials: Interfaces, depositions, and treatments
Robert D. Clark, [email protected]. Thin Films Process Technology, TEL
Technology Center, America, LLC, Livermore, California, United States
The continued scaling of the Complementary Metal Oxide Semiconductor (CMOS) logic architecture and memory devices
according to Moore’s law has led to a doubling of the number of devices per unit area in semiconductor microchips every
2 years since 1962.1 This continued scaling has now forced device makers to adopt new 3dimensional device structures,
integration and new materials such as high K dielectrics for an expanding number of applications in order to overcome
fundamental physical limits.2 Highly tailored deposition processes are being used to fabricate functional dielectric material
layers for future device architectures. Interspersed treatments and doping have been used to modify the dielectric layers
physical structure, composition, and electrical properties in order to further optimize the resulting device behavior. In order
to improve device contacts, ultra-thin (<10Å) dielectric layers may be deposited inside of high aspect ratio contact
structures in order to suppress Metal Induced Gap State (MIGS) penetration into the semiconductor at metalsemiconductor interfaces, and therefore provide lower contact resistivity. The chemical reaction processes and
transformations governing film deposition, composition, structure and interface control will be described and discussed
with respect to materials requirements for future semiconductor devices.
1. (a) Moore, G. E., Electronics 1965, 38 (8); (b) Bohr, M., Technical Digest of the IEEE International Electron Devices
Meeting, Washington, D.C., 2011; pp 1-6.
2. Clark, R.D., Materials 2014, 7 (4), 2913-2944.
INOR 452
Progress toward fluid materials for chemical hydrogen storage
Benjamin L. Davis1, [email protected], Asa Carre-Burritt2, Brian D. Rekken3. (1) MPA11, Materials Synthesis and Integrated Devices, Los Alamos National Laboratory, Los
Alamos, New Mexico, United States (2) Department of Chemistry and Chemical
Biology, Cornell University, Ithaca, New York, United States (3) DOW-Corning, Midland, Michigan, United States
Recent advances in battery technology have resulted exciting new electric vehicles (EV), such as the Telsa S, and the
more affordable Nissan Leaf. Although a key part of a non-fossil fuel transportation paradigm, EVs will not address longer
distances, as battery energy density is limited and recharging time a large issue. The Department of Energy (DOE) has
been developing fuel cell and hydrogen storage technologies to address this need. Fuel cell vehicles (FCV) currently for
lease operate with high pressure H2 tanks (~ 700 bar) that yield impressive 265-500 mile ranges. Much work is being
done to reduce the cost of these tanks, but ultimately the volumetric density of H 2 is poor and the DOE has been exploring
alternative technologies (physisorption, metal hydrides, chemical hydrides) so less expensive FCVs might be realized. Los
Alamos has been exploring ways to transform the chemical hydride ammonia-borane (H3N-BH3) into liquid forms for rapid
loading/unloading from a vehicle. This talk will discuss our recent work with functionalized amine-boranes and their
efficient regeneration for H2 storage.
INOR 453
Effects of fast charging on lithium-ion cells
Ira Bloom, [email protected]. Argonne National Laboratory, Argonne, Illinois, United
States
The USABC+ test manual [1] contains a test determine the capability of a battery to accept charge at high charging rates.
Here, a battery is quickly charged from about 40% to 80% state of charge in 15 min. This test was written in the mid1990’s when nickelmetal hydride was the technology of choice for automotive applications. With the introduction of
lithium-ion battery technology, the test may not be benign. The high charge rates used may introduce new degradation
modes, causing the performance of the battery to decline faster than expected. To determine the effects of fast- charging,
we used commercially-available, cells, containing two different chemistries, and charged them at rates in the range of 0.7
to 6 C. In this study, the SOC returned was either 100% or 40% and the discharge rate was C/1 or C/3. Fig. 1 shows the
impact of charge rate on cell resistance. As the charge rate increased, the rate of resistance increase and its non-linearity
increased.
Post-test examination was used to identify physical factors that contributed to the observations in Fig. 1. Example findings
are shown in Figs. 2A and 2B, where the rate was held constant at 4C and the SOC returned varied. Clearly, the physical
damage (delamination) was greater in the case where charge returned was smaller. The extensive delamination seen in
Fig. 2B may the cause of rapid resistance increase due to lack of contact between the anode and the underlying copper
foil. This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies,
Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357.
Reference
1. Electric Vehicle Battery Test Manual, Rev. 2, January 1996. + US Advanced Battery Consortium.
Fig. 1. Average, normalize resistance vs. time and charge rate for one of the cell chemistries studied.
Fig. 2. Delamination of anode as a result of changing the SOC returned, A=100%; B=40%. The charge rate in both was 4C.
INOR 454
Peptido-mimetic sequence-defined polymers based on a new synthetic architecture
Jay W. Grate, [email protected], Kai-For Mo, MIchael Daily, Chunlong Chen. Pacific Northwest National Laboratory,
Richland, Washington, United States
Sequence-defined polymers, epitomized in nature by polypeptides and poly(nucleic acids), are polymers composed of a
multiplicity of monomers, each monomer distinguished from another by having a different side chain, and the various
monomers are sequenced into a polymer in a predetermined order. These are distinguished from random copolymers. In
nature, sequence-defined polymers create biomaterials, encode information, perform biocatalysis, participate in molecular
recognition, and shuttle species across membranes. To date the vast majority of synthetic sequence-defined polymers are
either laboratory examples of the natural sequence-defined biopolymers, or close analogs based on similar structural units
and bond-forming reactions. For example, peptides, pseudopeptides, and peptoids all rely on amino acid structures and
peptide bonds.
In this presentation we will introduce and describe a new class of synthetic sequencedefined polymers whose architecture
does not involve peptide bonds. The chemistry behind the architecture provides facile approaches for the incorporation of
side-chains as "R-groups" into the monomer structures, such that diverse monomers can be produced. These monomer
structures can be assembled into polymer chains in predetermined order to create sequence-defined polymers. The
synthesis can be carried out either 1) using protected monomers appended to a growing polymer chain, deprotecting the
terminus of the chain before each monomer addition, or 2) assembled by a submonomer synthesis approach that does
not require monomer protection or deprotection steps. We will describe the results of three polymer synthesis methods
using these R-group substituted monomers: 1) batch synthesis of homopolymers, 2) solution phase synthesis by addition
of one monomer at a time using deprotection steps, and 3) a solid phase method using a submonomer approach to create
sequencedefined polymers.
In addition, we will show the results of molecular simulations of these new types of structures, which illustrate
conformational order due to hydrogen bonding and other interactions that are suggestive of protein secondary structure. It
is anticipated that sidechain functionality, self-organizing conformations, and intermolecular self-assembly of these
sequence-defined soft polymer materials will lead to biomimetic functionality and application.
INOR 455
Development of a 3D composite for NASA's Orion spacecraft compression pad
Jay D. Feldman, [email protected]. ERC Inc. @ NASA Ames Research Center,
Moffett Field, California, United States
NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human
exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule
is a 3dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad
serves first as a structural component and later as an ablative heat shield partially consumed upon Earth re-entry.
This presentation will discuss the mission requirements for this novel material, manufacturing development of the 3D
quartz / cyanate ester composite, relevant environment testing, and the overall status of development for the 2017 flight
test.
Orion Multipurpose Crew Vehicle & Compression Pad View
Large 3D woven quartz-fiber preform (12" x 11" x 3") before and after infusion with cyanate ester resin system.
INOR 456
Optimizing the performance of polyolefins via stabilization chemistry and effects
Roswell E. King, [email protected]. Performance Chemicals, BASF Corporation, Pleasantville, New York, United
States
Although polyolefins were discovered around 70 years ago, the technology continues to advance via the development of
new catalysts, polymerization processes, and the design of olefin polymer compositions for specific end use applications.
Accordingly, the polymer producers, as well as the manufacturers of downstream products, are interested in additive
technologies that will not only maintain, but further improve the physical and aesthetic properties of their products.
This presentation will begin by providing an overview of stabilization fundamentals, and recent advances. The
presentation will close with a quick overview of new directions, above and beyond stabilization, highlighting new additive
technologies that provide innovative effects to the plastic articles for specific end use applications.
The overall goal of polymer stabilization is to ensure maintenance of molecular weight and molecular weight distribution;
thereby preserving the basic architecture of the polymer. These type of stabilizers also need to provide aesthetics, such
as low initial color and good color maintenance. In selected applications, long term thermal stability must also be
preserved.
Beyond these fundamental contributions, there are ancillary properties that are also important, such as, inhibition of gas
fade discoloration, sufficient additive compatibility, resistance to interactions with other additives, pigments and modifiers,
reduced taste and odor, and the suppression of ‘gels’ (visual imperfections).
We have examined the impact of these new stabilization chemistries, not necessarily to simply displace existing
stabilization systems, but also to differentiate and develop new markets and opportunities for polyolefins. As the polyolefin
industry has grown, so have the stabilizers product & technologies in an effort to meet various requirements of new
applications.
Parallel Growth of Polyolefins and Stabilization Technologies
INOR 457
Natural gas to ethylene in one step: Siluria technologies OCM (oxidative coupling of methane)
Gregory Nyce, [email protected]. Siluria Technologies, Pleasanton, California,
United States
The oxidative coupling reaction of methane (OCM) for direct, one-step conversion of methane to ethylene has been
known for many years but never commercialized. Siluria Technologies has succeeded in designing a commercially viable
OCM process by bringing together scientific advances of the past decade that were unavailable to earlier researchers in
this chemistry. The advances are (1) Nanowire Catalyst Design - a synthetic method that permits the influencing of
catalyst properties by changing the active sites, and which can be made under commercially scalable synthetic conditions,
and (2) High-throughput Screening – that allows for measuring gas-to-gas reactions orders of magnitude faster than in
traditional reaction screening.
Siluria's R&D and engineering work on the reaction has focused on commercially viable process conditions and reactor
configurations. Earlier work on this highly exothermic reaction used catalysts produced by conventional bulk methods and
resulted in temperatures, pressures, catalyst lifetimes, and other reaction conditions that were outside of a practical
commercial process window.
The recent and rapid pace of natural gas discovery and development in North America and other regions provides a very
strong business case for the deployment of this technology to produce on-purpose ethylene or liquid fuels.
INOR 458
Cobalt complexes containing pendant amines in the second coordination sphere as electrocatalysts for energy
storage
Ming Fang1, [email protected], Eric S. Wiedner 3, R Morris Bullock2. (1) Pacific Northwest National Laboratory,
Andover, Massachusetts, United States (2) MS K2-57,
Pacific Northwest National Laboratory, Richland, Washington, United States (3) Pacific
Northwest National Laborartory, Richland, Washington, United States A series of heteroleptic 17e cobalt complexes,
[CpCoII(PtBu2NPh2)](BF4),
[CpC6F5CoII(PtBu2NPh2)](BF4), and [CpC5F4NCoII(PtBu2NPh2)](BF4) (where PtBu2NPh2 = 1,5diphenyl-3,7-di-tertbutyl-1,5-diaza-3,7-diphosphacyclooctane, CpC6F5 = C5H4(C6F5), and CpC5F4N = C5H4(C5F4N)) were synthesized, and the
structures of all three were determined by X-ray crystallography. Electrochemical studies showed that the Co III/II couple of
[CpC5F4NCoII(PtBu2NPh2)]+ appears 250 mV positive of the CoIII/II couple of [CpCoII(PtBu2NPh2)]+ as a result of the strongly
electron-withdrawing perfluoropyridyl substituent on the Cp ring. The cobalt complex with the most electron-withdrawing
Cp ligand, [CpC5F4NCoII(PtBu2NPh2)]+, is an electrocatalyst for production of H2 using using [p-MeOC6H4NH3][BF4] as the
acid, with a turnover frequency of 350 s–1 and an overpotential of 0.86 V at Ecat/2 in CH3CN. Electrochemical and pKa
measurements were used to obtain thermodynamic data for cleavage of the Co–H bond.
This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center
funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
INOR 459
Zero-field spin polarization effects on Dexter transfer
J. Andrew Kouzelos1, Monica Soler2, James K. McCusker1,
[email protected]. (1) Department of Chemistry, Michigan State University, East
Lansing, Michigan, United States (2) Departamento de Ciencia de los Materiales, University of Chile, Santiago, Chile
The notion of conservation of angular momentum is one that is widely employed in the physical sciences, but its role in
influencing the kinetics and mechansim of chemical processes is elusive due to the difficulty in modulating spin properties
independent of other changes to the system. We are approaching this question by using Heisenberg spin-coupled
assemblies as a means of introducing changes in the zero-field spin properties of donor-acceptor systems with the goal of
assessing its impact on photoinduced electron and energy transfer processes. This presentation will focus on one such
system in which an antiferromagnetically-coupled dinculear Mn(II) complex has been incorporated as an acceptor in a
macromolecular assembly. Following photoexcitation of a covalently attached Ru(II) polypyridyl moiety, Dexter transfer
from the 3MLCT excited state of the donor into the Mn(II)Mn(II) core is observed. Detailed temperature-dependent timeresolved emission data acquired over a range of 10 - 300 K reveal pronounced changes in the rate constant for energy
transfer. Through a comparison of data on an isostructural Mn(II)Zn(II) analog, it will be shown that these observations are
linked to the presence of spin states within the excited ligand-field manifold of the Mn(II)Mn(II) assembly due to exchange
between the two high-spin Mn(II) ions and the concomitant introduction of new spin-allowed pathways for energy transfer.
INOR 460
Theoretical characterization of conduction-band electrons and magnetic exchange interactions in photodoped
and aluminum-doped diluted magnetic semiconductors
Xiaosong Li, [email protected], Joshua Goings. Department of Chemistry, University of Washington, Seattle, Washington,
United States
Colloidal semiconductor quantum dots (QDs) containing excess delocalized charge carriers play important roles in the
development of spintronic technologies. Such n- or ptype semiconductor QDs have been prepared using remote doping,
photodoping, aliovalent doping, or electrochemical oxidation and reduction. In this work, the electronic structures of n-type
ZnO nanocrystals formed via photochemical reduction and by aliovalent doping with aluminum are investigated using
time-dependent density functional theory. Connections between the density functional theory results and a simple
quantum mechanical particle-in-a-spherical-potential model are highlighted. Molecular orbitals obtained from density
functional theory reveal the often-invoked S-, P-, D-, ... type super orbitals used to characterize the absorption spectra of
these materials. The magnetic exchange interactions between the charge carrier of different electronic characteristics and
the magnetic dopant have been investigated and presented in this work.
INOR 461
Near-infrared paramagnetic manganese-doped PbS nanocrystals
Lyudmila Turyanska, [email protected]. School of Physics and astronomy, The University of
Nottingham, Nottingham, United Kingdom
L. Turyanska1, F. Moro1, O. Makarovsky1, A. Patanè1, M. W. Fay2, and P. C. M. Christianen3
d-shell electrons and the nuclear spins of individual Mn 2+ ions in the QDs (Fig. 1a), and long spin coherence times (~ 4 ms
at 5K) and Rabi oscillations [2]. Finally, we use high magnetic fields (up to 30T) to show that Mn-impurities provide a tool
for engineering the effective exciton g-factor (Fig. 1b) [3]. The observation of quantum oscillations and tuneable g-factor
makes these new nanocrystals attractive candidates for spin manipulation studies and quantum information applications.
Dual functionality, i.e. NIR luminescence and paramagnetism, of PbS:Mn also opens up exciting prospects for their future
exploitation as imaging labels for combined fluorescence and magnetic resonance imaging.
[1] L. Turyanska, et. al., Part. Part. Syst. Charact. 30 945 (2013).
[2] F. Moro, et. al., accepted in Phys. Rev. B (2014). [3] L. Turyanska, et. al., Nanoscale 6 8919 (2014).
1
School of Physics and Astronomy, The University of Nottingham, NG7 2RD, UK
Nottingham Nanotechnology and Nanoscience Centre, NG7 2RD, UK
3 High Field Magnet Laboratory, Radboud University, Nijmegen 6525 ED, The Netherlands
The controlled incorporation of dopant impurities in a single colloidal nanocrystal
(Quantum dot, QD) is a challenging field of research with potential for numerous
applications in nanotechnology. Here we report the successful incorporation of Mn in
colloidal PbS. Our QDs combine within one structure, paramagnetic properties of
transition metals with photoluminescence emission in the near-infrared wavelength range
(850-1200 nm) [1]. The electron spin resonance (EPR) studies reveal magnetic
resonance transitions between states that are split by the hyperfine interaction between
2
Fig.1 (a) EPR spectrum and (inset) HR TEM image of QDs with 0.5% Mn. (b) Dependence of the effective exciton g-factor on the
Mn-content in PbS QDs.
INOR 462
Chirality induced spin selectivity (CISS) effect-chiral molecules for spintronics
Ron Naaman, [email protected]. Dept Chemical Physics, Rehovot, Israel
Spin based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. In
the recent years a novel effect was demonstrated, the chiral induced spin selectivity (CISS) in which it was found that
electron transmission through chiral molecules is spin dependent.[1] This effect opens the ability to produce spin polarized
electrons without magnetic material. We will present the theory explaining the effect and its relevancy to electron transfer
in bio-systems [2,3] and in spintronics applications.
[1] R. Naaman, D.H. Waldeck, The Chiral Induced Spin Selectivity Effect, J. Phys.
Chem. Lett. (feature) 3, 2178−2187 (2012).
[2] D. Mishra, T.Z. Markus, R. Naaman, M. Kettner, B. Göhler, H. Zacharias, N.
Friedman, M. Sheves, C. Fontanesi, Spin-Dependent Electron Transmission through Bacteriorhodopsin Embedded in
Purple Membrane, PNAS, 110 (37) 14872-14876 (2013).
[3] I. Carmeli, K. . Kumar, O. Hieflero, C. Carmeli, R. Naaman, Spin Selectivity in Electron Transfer in Photosystem I, Angew.
Chemie 53, 8953 –8958 (2014).
INOR 463
Decoherence in crystals of quantum molecular magnet
Susumu Takahashi1,2, [email protected]. (1) Department of Chemistry, University of
Southern California, Los Angeles, California, United States (2) Department of Physics, University of Southern California,
Los Angeles, California, United States
Decoherence in nature has become one of the most pressing problems in physics. Many applications, including quantum
information processing, depend on understanding it. Experimental understanding of decoherence in molecular magnets
has been limited by short decoherence times, which make coherent spin manipulation extremely difficult. Here we show
that the theory for insulating electronic spin systems can make accurate predictions for decoherence in molecular-based
quantum magnets. Experimentally we reduce the decoherence in Fe8 molecular magnets and Mn3 molecular magnets
significantly by applying a strong magnetic field. For a single crystal of the Fe8 molecular magnet, the theory predicts the
contributions to the decoherence from phonons, nuclear spins, and intermolecular dipolar interactions [1]. In experiments
we find that the decoherence time varies strongly as a function of temperature and magnetic field [1-3]. The theoretical
predictions are fully verified experimentally - there are no other visible decoherence sources [1].
[1] S. Takahashi et al., Nature 476 , 76 (2011).
[2] S. Takahashi et al., Phys. Rev. Lett. 102, 087603 (2009).
[3] C. Abeywardana et al., in-preparation (2014).
INOR 464
Effects of the addition of spin on donor-acceptor excited state electronic structure
Benjamin Stein3, Christopher Tichnell4, Daniel Stasiw5, David Shultz1, Martin L. Kirk2, [email protected]. (1) Chemistry,
North Carolina State University, Raleigh, North Carolina, United States (2) The University of New Mexico, Albuquerque,
New Mexico,
United States (3) Chemistry and Chemical Biology, University of New Mexico,
Albuquerque, New Mexico, United States (4) Chemistry, NC State University, Raleigh, North Carolina, United States
Electron transfer/transport, magnetic exchange interactions, and spin-orbit coupling all feature prominently in the design of
molecular spintronic (spin electronic) materials. Radical elaborated Donor-Acceptor systems represent ideal platforms for
understanding key relationships between excited state exchange interactions, photomagnetic lifetimes, and long-range
spin correlation, all of which impact our understanding of design principles for the construction of molecular spintronics
materials. Here we utilize a combined spectroscopic approach to provide insight into the electronic structure of novel
transition metal – radical complexes. We will highlight how metal and ligand spin orbit effects conspire to dramatically
affect excited state lifetimes, and how radical elaboration of these systems allows for their excited states to be probed at
high resolution through the application of magnetic circular dichroism spectroscopy. The results show that spin elaboration
induces large excited state magnetic exchange interactions that result in a complex interplay between the exchange split
excited states and the interstate spin orbit interactions that admix these states. Implications for modifying intersystem
crossing rates and excited state lifetimes will be discussed. INOR 465
π-System superexchange in cross-conjugated donor-bridge-acceptor triads: Electronic structure contributions to
quantum interference
David Shultz1, [email protected], Daniel Stasiw1, Benjamin Stein2, Diana HabelRodriguez2, Martin L. Kirk2. (1) Chemistry,
North Carolina State University, Raleigh,
North Carolina, United States (2) The University of New Mexico, Albuquerque, New Mexico, United States
The electronic coupling (HDA) between a donor and an acceptor in a Donor-BridgeAcceptor (D-B-A) triad is a primary
factor in determining intramolecular electron transfer rates and the efficiency of electron transport in single-molecule
devices. This bridgemodulated electronic coupling can be evaluated effectively in the context of Anderson and McConnell
superexchange models. When the D-B-A triad is comprised of a crossconjugated π-system, electron transfer is slow and
electronic conductance is weak relative to a conjugated triad. However, theory has suggested that the conductance in
cross-conjugated triads can be varied with a suitable bridge probe, and thus such single molecule devices designed using
the construct form the basis for quantum interference effect transistors. We have shown the utility of D-B-A biradicals at
elucidating excited state contributions to HDA using a valence bond configuration model, and in particular we determined
the operative π-superexchange pathway that turns on substantial electronic coupling in cross-conjugated triads. The
electronic coupling in crossconjugated triads is manifest in antiferromagnetic coupling between donor (metal semiquinone)
and acceptor (nitronylnitroxide) spins in the ground state, in marked
contrast to the ferromagnetic exchange observed in the π-conjugated analogues. Herein, we will present new results that
further explore excited state electronic structure contributions to HDA in cross-conjugated D-B-A biradical complexes.
INOR 466
Thinking constructively about hydraulic fracturing fluid design in the new resource landscape
Bruce A. MacKay, [email protected]. Schlumberger, Sugar Land, Texas, United States
Economically efficient production of oil and gas from unconventional shale resources requires very large volume hydraulic
fracturing treatments. This talk explains the engineering objectives that drive decisions in the design and development of
fracturing fluids. It will also survey the current industry state of the art in terms of fracturing fluid development at a high
level, with a focus on chemical technologies that enhance production, resource management, and stewardship.
INOR 467
Review of industrial biocides used for microbial control in hydraulic fracturing
Terry M. Williams, [email protected]. Dow Chemical Company, Collegeville, Pennsylvania, United States
Water management is a critical component in the hydraulic fracturing process for recovery of oil and natural gas reserves.
Approximately 3-5 million gallons of water are used for the drilling and fracturing stages in unconventional hydrocarbon
extraction. Bacterial contamination in the surface and produced waters can result in sulfide souring by sulfate reducing
bacteria (SRB) and microbially influenced corrosion by the SRB and acid-producing bacteria (APB). Effective microbial
control programs are needed to minimize the adverse effects these bacteria on the quality of the produced hydrocarbon
and integrity of the asset and downhole formation. Industrial biocides, such as glutaraldehyde, quaternary ammonium and
phosphonium compounds, and alkylamines have been used to control bacterial growth in oil and gas operations for
decades. More recently, several additional classes of biocides have been employed in energy recovery applications to
meet the changing needs for microbial control and to advance beyond the traditional quick-kill strategy used in topside
treatment. These include both oxidizing and non-oxidizing antimicrobials. As a result, new biocide technologies and
combinations have been developed to broaden the range of effective treatments for longer-term microbial control under
more aggressive salinity and temperature conditions. This presentation will review the effectiveness, stability, compatibility
and environmental features of the various biocides used in hydraulic fracturing.
INOR 468
Electrochemically produced biocides: A greener disinfectant for waters used in hydraulic fracturing
Andrew K. Boal, [email protected]. MIOX Corporation, Albuquerque, New Mexico, United States
Treatment of water used in hydraulic fracturing is a highly complex process focused on delivering a fluid with the physical,
chemical, and biological properties desired for a given job. One critical aspect of hydraulic fracturing water treatment is
disinfection, which is primarily undertaken to prevent the growth of Sulfate Reducing Bacteria (SRB), Acid Producing
Bacteria (APB), Iron Related Bacteria (IRB), or other microbiological species once the water has been pumped down hole.
Without effective disinfection, production by a well can be severely limited, impeded completely, or the product soured by
the uncontrolled growth of bacteria once the well is in production. Traditionally, disinfection of these waters has been
accomplished using chemicals such as glutaraldehyde or chlorine dioxide. While effective at achieving the desired
microbiological inactivation, both chemicals have substantial operational limitations, severe associated worker hazards,
and are known to have negative environmental impacts. Recently, MIOX has been implementing the use of mobile OnSite Generation (OSG) platforms to produce highly effective and more environmentally friendly biocides for hydraulic
fracturing water disinfection applications. MIOX’s OSG systems employ the electrolysis of sodium chloride brines to
produce chlorine-based disinfectant solutions, which are then added to waters either on-the-fly during active hydraulic
fracturing processes or injected into waters in holding ponds between hydraulic fracturing jobs. Since the only chemical
transported to a work site is sodium chloride, and the disinfectant produced as a result of the electrolysis process is a
solution containing less than 1% chlorine by volume, MIOX’s process represents a tremendous improvement in terms of
worker and environmental safety compared to traditional disinfectant chemistries used in hydraulic fracturing. This talk will
present an overview of this technology and its general application to hydraulic fracturing water disinfection treatment with
a specific focus on experiences in the use of OSG-produced biocides for the disinfection of recycled produced water used
for hydraulic fracturing in a US shale play.
Photograph showing produced water (left) before and (right) after treatment with on-site generated biocide.
INOR 469
Reclaiming produced water: Using chemistry to convert a waste stream into a resource
Kevin Sikkema, [email protected]. Swire Oilfield Services, Conroe, Texas, United
States
Historically produced water has been seen a waste stream that needs to be disposed of. Due to the increasing costs of
disposing produced water and the diminishing supplies of fresh water, there is growing interest in treating produced water
so that it can be used to fracture the next well. The performance of chemicals used to fracture wells is affected by the
constituents in the produced water. Therefore the extent of treatment, i.e. what constituents to treat for and to what
concentrations, depends on what chemicals will be used to fracture the next well. Produced water is treated stepwise, first
to separate oil and suspended solids, then to reduce the concentration of scaling multivalent ions, and finally to reduce the
concentration of dissolved salts. There are a number of technologies available to treat each of the constituents in
produced water, each with their advantages and disadvantages. The presentation will give an overview of the chemistry of
the constituents in the produced water, and the technologies used to treat them.
INOR 470
Noncovalent recognition of "unusual" but active DNA and RNA structures
Michael J. Hannon, [email protected]. Chemistry, University of Birmingham, Birmingham, United Kingdom
DNA occupies its familiar duplex form when it is ‘asleep’ and not being processed.
When it is in action its structures are very different indeed.
The recognition of DNA replication forks and other Y-shaped DNA and RNA junctions using unique nanosized metallosupramolecular cylinder arrays [1-3] will be discussed together with work on new agents that recognise tetraplex DNAs
found in gene promoter regions.
We have shown that our cylinders bind strongly and preferentially to DNA fork structures and prevent DNA transactions in
vivo, that they are taken up readily into cells and rapidly localise in cell nuclei, where they interfere with the processing of
DNA leading to cell cycle arrest followed by apoptosis, without inducing genotoxicity or mutagenicity.
The key challenge of how to build from in vitro biophysical observations to demonstrate what chemistry is happening in
the cell, where and how quickly it is occurring and how that induces the biological response will be addressed.
References
1. S. Phongtongpasuk, S. Paulus, J. Schnabl, RKO Sigel, B. Spingler, M.J. Hannon, E.
Freisinger (2013) Angew Chem Int Ed 52, 11513-11516
2. C. Ducani, A. Leczkowska, N. J. Hodges, M. J. Hannon, (2010) Angew Chem Int Ed
49, 8942—8945
3. D. Boer, J. Kerckhoffs, Y. Parajo, M. Pascu, I. Usón, P. Lincoln, M. Hannon, M. Coll, (2010) Angew Chem Int Ed 122,
2386--2389.
Cylinder bound in the heart of a DNA 3WJ
INOR 471
Tuning in cellulo targeting and function of metal complex bioprobes
Jim A. Thomas, [email protected]. Chemistry, University of Sheffield, Sheffield, S Yorks, United Kingdom
Ruthenium(II) polypyridyl complexes that interact reversibly with DNA can display high binding affinities. We are
constructing complexes with specific sequence binding preferences, as well as interesting biophysical and photophysical
properties. Although such complexes offer potential as in cellulo probes for luminescence microscopy, poor cellular
uptake by live cells generally restricts the use of many such systems.
In recent studies we have developed complexes that are taken up by live eukaryotic and prokaryotic cells where they bind
to specific biomolecules. 1 These complexes function as multifunctional probes imaging intracellular structures2 and
biomolecules3 through a number of different high-resolution microscopy techniques, including conventional and timedomain4 optical microscopy and transmission electron microscopy. 5
(1) Rajput, C.; Rutkaite, R.; Swanson, L.; Haq, I.; Thomas, J. A. Chem. Eur. J. 2006, 12, 4611–4619.
(2) Gill, M. R.; Garcia-Lara, J.; Foster, S. J.; Smythe, C.; Battaglia, G.; Thomas, J. A. Nat Chem 2009, 1, 662–667.
(3) Gill, M. R.; Cecchin, D.; Walker, M. G.; Mulla, R. S.; Battaglia, G.; Smythe, C.; Thomas, J. A. Chem. Sci. 2013.
(4) Baggaley, E., et al, Angew. Chem. Int. Ed. 2014, 53, 3367–3371.
(5) Wragg, A., et al. Chem Commun, in press.
INOR 472
Platinum biomolecule target analysis using click chemistry
Jonathan D. White, Alan D. Moghaddam, Rachael Cunningham, Kory Plakos, Maire F.
Osborn, Michael M. Haley, Victoria DeRose, [email protected]. Department of Chemistry, University of Oregon,
Eugene, Oregon, United States
Platinum anticancer therapeutics, broadly used in frontline treatments of solid tumors, are known to crosslink cellular DNA
and trigger apoptosis. These agents bind other biomolecules, including RNA and proteins, and may influence numerous
regulatory pathways. Despite prevalent use, comprehensive identification of cellular targets that may lead to resistance,
side effects, and alternative apoptotic pathways is not available, nor has the potential for these compounds towards in
vivo structural analyses been explored. We have previously shown that cisplatin treatment results in significant platinum
accumulation on yeast ribosomal RNA [1], with specificity towards high-impact sites [2]. To further identify, isolate, and
visualize such targets we have developed platinum compounds modified for post-treatment ‘click’ azide-alkyne
cycloaddition reactions. Picazoplatin, an azide-modified picoplatin, readily undergoes binding and subsequent fluorescent
labelling with DNA and RNA [3] as well as proteins. Posttreatment fluorescent labelling of RNA extracted from S.
cerevisiae treated with picazoplatin as well as an additional reagent, 2-ADAPPt [4], demonstrates utility of these
compounds for in vivo exploration. The properties of additional Pt(II) compounds with azide and alkyne modifications, and
their efficacies in visualizing and analyzing Pt targets, will be presented.
Financial support by the National Science Foundation NSF CHE-1153147 is gratefully acknowledged.
1. Hostetter AA, Osborn MF, DeRose VJ (2012) ACS Chem. Biol. 7:218-225.
2. Osborn MF, White JN, DeRose VJ (2014) ACS Chem. Biol. 9: 2404–2411.
3. White JN, Osborn MF, Moghaddam AN, Guzman LE, Haley MM, DeRose VJ (2013) J Am. Chem. Soc. 135:11680-11683.
4. Moghaddam AN, White JN, Haley MM, DeRose VJ (2014) Dalton Trans, in press.
INOR 473
Catalytic metallodrugs: Structure-function and activity studies of a broad therapeutic platform
James A. Cowan, [email protected]. Chemistry and Biochemistry, The Ohio State University, Columbus,
Ohio, United States
The introduction of metal ions affords many opportunities to design new families of drugs with novel mechanisms of action
against specific therapeutic targets. This presentation will review recent progress in our laboratory on the design and
study of catalytic metallodrugs against nucleic acid, protein and carbohydrate targets of biomedical interest. Structural,
mechanistic, cellular and animal studies provide a glimpse of the therapeutic potential of such molecules and
improvements in the areas drug resistance and side effects. Kinetic and mechanistic studies reveal patterns of reactivity
that suggest pathways for improved in vitro and in vivo performance. These advances will be illustrated by selected
studies of metallodrugs designed against viral, bacterial, cancer, and cardiovascular disease targets.
INOR 474
Tuning the pharmacological properties of platinum-acridine anticancer agents using novel prodrug and
subcellular targeting strategies
Ulrich Bierbach, [email protected]. Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina,
United States
Platinum-acridine hybrid agents induce apoptosis in several solid tumors models at concentrations up to three orders of
magnitude lower than the clinical drug cisplatin. Unlike cisplatin, the hybrid molecules are strong dual inhibitors of
replication and transcription. The mechanism of action of these compounds involves formation of unique monofunctional–
intercalative DNA adducts in chromatin, which trigger cell-cycle arrest in late G1/early S phase. This presentation
discusses key features of the molecular mechanism, structure-activity relationships, and cellular pharmacology that have
guided the design and preclinical development of these agents.
Immunocytochemical and post-labeling techniques, in conjunction with confocal microscopy, were used to study the
hybrids in live and fixed cancer cells. The results of these studies and screening using a yeast-based chemical genomics
platform suggest that the hybrid adducts are a more severe form of DNA damage than the classical cisplatin-type crosslinks. Novel strategies of reducing the systemic toxicity of the agents based on unique prodrug designs and by directing
them to more cancer-specific targets are discussed. These include guanine-rich sequences of the human telomeric repeat
and ribosomal DNA transcribed by RNA polymerase I in the cell’s nucleolus.
INOR 475
Unusual synergism of serum transferrin titanium(IV) coordination brings insight into its potential transport and
bioactivity in the human body
Arthur D. Tinoco, [email protected]. Chemistry, University of Puerto Rico Rio Piedras, San Juan, Puerto Rico,
United States
The transferrin proteins are one of the best studied protein families and have long been acknowledged for their
contributions to the regulation of iron, an essential element. Serum transferrin especially has been studied for its transport
of iron(III) into cells from many different perspectives. These include the spectroscopic and affinity differences of Fe(III)
coordination to the two homologous metal binding sites, metal stabilization of the protein, and the molecular mechanisms
for the endocytosis and release of Fe(III) in cells. Recent studies suggest a more complex role of serum transferrin in
metal transport; one that alludes to environmental adaptation. Titanium, a ubiquitous and nonessential metal, finds its way
into the body via several means. It is especially prominent in people who have or have had titanium-based implants, with
their serum levels reaching micromolar amounts. Coordination by human serum transferrin (HsTf) to its hard metal binding
sites is largely attributed to the Ti(IV) blood speciation. Little is understood about how Ti(IV) coordinates to HsTf and what
the biological fate of this complex is. Our studies reveal an unusual synergism and mode of metal coordination to the
protein. Citrate, a metabolically important molecule present in serum at 100 μM, exhibits the previously uncharacterized
functions of transporting Ti(IV) to HsTf and serving as a synergistic anion for metal binding. Metal transport by citrate is a
property that has been little explored in the human body. That it serves as a synergistic anion is extremely novel
especially when considering that it plays a metal extraction role in Fe(III) interaction with the protein. NMR and UV-Vis
spectroscopy were used to develop a new model for Ti(IV) coordination to HsTf, one where the metal binds to two of the
four protein metal binding residues, and to the synergistic anions carbonate and citrate. This metal coordination results in
an open conformation for the protein as supported by differential scanning calorimetry data and in a less stabilized protein
relative to the Fe(III) bound form. Affinity studies performed at pH 7.4 and 25 °C show high metal affinity to the protein log
KC-site = 25.2 and log KN-site = 23.5. Despite differences in modes of coordination, these strengths suggest that Ti(IV) can
compete with Fe(III) for HsTf binding. Cellular studies elucidate the importance of the Ti(IV) binding synergism of HsTf
and citrate in regulating the metal’s bioactivity.
INOR 476
Drug membrane interactions and uptake as key aspects of drug action
Debbie C. Crans, [email protected]. Colorado State University, Fort Collins, Colorado, United States
Because the stability of coordination complexes is sensitive to their environment, the uptake of metal containing drugs is a
particularly important event for drug action as implied in consulting reviews on anti-diabetic vanadium compounds and
their modes of action.1 In the following, we examine the interaction of several classes of drugs, including organic2 and
inorganic3 metal-based anti-diabetic drugs, with interfaces and compare them with selected organic antimalarial 4 and
antituberculosis5 drugs. The vanadium-containing anti-diabetic drugs include both organic coordination complexes and
larger polyoxometalate-salt drugs. The interactions of several of these compounds with model membrane systems have
provided detailed molecular information on how these compounds interact in homogeneous systems. Depending on the
polarity and complementarity of the compounds with the interface, coordination complexes such as
bis(maltolato)dioxovanadium(V) and dipicolinatodioxovanadium(V) are found to penetrate the interface. 2 Inorganic
oxometalate and salts interact less readily with the membrane interface, however the counter ion can dramatically impact
this process.3 A pharmacokinetic study demonstrated that efficacy does not follow total vanadium but that speciation and
distribution is important.6 The interaction of the selected antimalarial or anti-tuberculosis drugs with the membrane
interface is non-trivial, in part because of the complex membranes and in part because the selected drugs are
protonophores.5 Despite the differences in modes of action, all these cases demonstrate how important interactions with
membranes are in drug action.
References
1.
K.H. Thompson, J. Lichter, C. LeBel, M.C. Scaife, J.H. McNeill, C. Orvig, J. Inorg. Biochem. 2009, 103, 554-558.
2.
D. C. Crans, S. Schoeberl, E. Gaidamauskas, B. Baruah, and D. A. Roess J. Biol. Inor. Chem. 2011, 16, 961-972.
3.
A. Chatkon, P. B. Chatterjee, M. A Sedgwick, K. J. Haller and D. C. Crans Eur. J. Inorg. Chem. 2013, 10-11,
1859-1868.
4.
N. Samart, C. Beuning, K. Haller, C. D. Rithner, D. C. Crans Langmuir, 2014, 30, 8697-8706.
5.
W. Li, A. Upadhyay, F. L. Fontes, E. J. North, Y. Wang, D. C. Crans, A. E. Grzegorzewicz, V. Jones, S. G.
Franzblau, R. E. Lee, D. C. Crick, and M. Jackson Antimicrob. Agents Chemotheraphy. 2014, In press.
6.
G. R. Willsky. K. Halvorson, M. E. Godzala III, L.-H. Chi, M. Most, P. Kaszynski, D. C. Crans, A. B. Goldfine, P. J.
Kostnyniak Metallomics 2013, 5, (11) 1491-1502. INOR 477
Understanding anion-π interactions: from substituted benzenes to Nheterocycles
Steven E. Wheeler, [email protected]. Department of Chemistry, Texas AM
University, College Station, Texas, United States
The concept of “π-acidic” rings is central to discussions of many non-covalent interactions, particularly anion-π
interactions. Despite the utility of anion-π interactions in myriad applications, popular explanations of their origin are
flawed. We will present a simple physical model of the origin of anion-π interactions. In the process, we will unveil many
misconceptions that accompany discussions of anion-π interactions, electrostatic potentials, and molecular quadrupole
moments of aromatic systems. For example, we will show that anion-π interactions involving N-heterocyclic azines arise
from the distribution of charges in the molecular plane, not changes in the aryl π-electron distribution. Moreover, the
positive electrostatic potentials and molecular quadrupole moments (Q zz) often attributed to the π-deficiency of these rings
are a consequence of the position of nuclear charges, not changes in the π-electron distribution as is widely assumed.
Ultimately, we will place anion-π interactions on a much more firm physical foundation, which should facilitate their use in
practical applications.
INOR 478
Role of inorganic chemistry in the activities of antimicrobial peptides
Alfredo M. Angeles Boza, [email protected]. University of
Connecticut, Storrs, Connecticut, United States
Antimicrobial peptides (AMPs) represent promising therapeutic agents against bacterial and fungal pathogens. Efforts to
improve peptide activity through structural modifications have traditionally remained away from the inorganic chemistry
toolbox. Interestingly, nature seems to exploit inorganic chemistry in the design of AMPs. A perusal of the Antimicrobial
Peptide Database shows that more than 40 peptides contain the Amino Terminal Cu(II)- and Ni(II)-binding (ATCUN) motif.
This sequence is capable of generating reactive oxygen species (ROS) after binding copper ions. We will discuss our
recent results on Ixosin (GLHKVMREVLGYERNSYKKFFLR), an AMP isolated from the hard tick Ixodes sinensis, and
show the importance of the ATCUN motif in its sequence. Our attempts to improve the antimicrobial activity of AMPs by
adding an ATCUN sequence will also be presented.
INOR 479
Highly unsaturated cationic metal complexes supported by pincer ligands
Oleg Ozerov, [email protected], Jessica C. DeMott, Rafael Huacuja. Chemistry, Texas AM University, College
Station, Texas, United States
Pincer ligands provide a robust and rigid supporting environment that allows generation of highly unsaturated transition
metal centers. This presentation will describe synthesis and reactivity of new cationic complexes of group 9 and 10
complexes. We will discuss how unsaturation leads to unusual electronic consequences, enables new types of ligand
non-innocence and permits facile reactions with C-H bonds. Our synthetic strategy involves abstraction of an anionic
halide or pseudohalide using salts of a reactive main group cation with a weakly coordinating carborane-based anion.
Carborane anions are especially attractive because of their resistance to high levels of Lewis acidity and oxidative power,
as well as their remarkable propensity for forming Xray quality single crystals.
INOR 480
Nonexistent compounds
Christopher C. Cummins2, [email protected], Robert Field1, Matthew Nava2, Barratt
Park2, Wesley Transue2, Alexandra Velian3. (1) Dept of Chem 6-219, MIT, Cambridge, Massachusetts, United States (2)
Department of Chemistry, Massachusetts Institute of
Technology, Dorchester, Massachusetts, United States (3) Chemistry, MIT, Cambridge, Massachusetts, United States
The book Nonexistent Compounds by W. E. Dasent gives consideration to compounds "... whose structures do not offend
the simpler rules of valence, but which nevertheless are characterized by a low degree of stability." One such compound
mentioned in the book is the diatomic molecule P2. The presentation will delineate synthetic access to sources of P2 that
may be regarded (depending upon mechanism) as thermal molecular precursors to P2 or as P2 transfer agents. We will
also describe our efforts to characterize volatilized species by molecular beam mass spectrometry and by spectroscopy.
New cycloaddition reactivity studies involving P2 will be described. Finally, time permitting, related studies on HCP and
cis-diazene will be discussed.
INOR 481
New Carbon-Hydrogen Activation Reactions by Titanium Alkylidynes and Phosphino-Alkylidynes
Daniel J. Mindiola, [email protected]. Chemistry, University of Pennsylvania, Bala Cynwyd, Pennsylvania, United
States
We will present the reactivity of a transient titanium alkylidyne [(PNP)Ti≡C tBu] and the
Ti(II) synthon (PNP)Ti(eta2-H2C=CH2)(CH2tBu) (PNP = N[2-P(CHMe2)2-4methylphenyl]2–). These systems engage in
intermolecular C-H activation and functionalization reactions of tertiary phosphines and phosphaylides. We have found
that phosphines and phosphaylides are activated and dehydrogenated and thus give rise to formation of phosphino
substituted alkylidenes and alkylidynes ligands. Independent synthesis of these species and mechanistic work will be also
presented.
INOR 482
Ligand and reagent effects in C–H borylation
Milton R. Smith, [email protected]. Department of Chemsitry, Michigan State University, East Lansing, Michigan,
United States
Ir-catalyzed C-H borylation exhibit regioselectivities that are often determined by steric effects, which makes this method
of arene functionalization complementary to transformations whose selectivities are electronically determined. Ligand
modifications can alter selectivities. In contrast, less is known about the effects of the boron reagents. The role of ligands
and reagents in controlling selectivities for challenging substrates will be discussed.
INOR 483
Carbene-stabilized allotropes: Synthesis, structure, and reactivity
Gregory H. Robinson, [email protected]. Univ of Georgia, Athens, Georgia,
United States
Recent efforts from this laboratory have resulted in a number of novel main group element diatomics stabilized by Nheterocyclic carbenes (L:) including L:Si=Si:L, L:PP:L, and L:As-As:L. The reactivity of these molecules has proven
particularly interesting and has afforded a N-heterocyclic carbene-based dimeric molecules. For example, a carbenestabilized molecule containing the long-sought phosphorus analog of dinitrogen tetroxide and the first structurally
characterized diarsenic radical have been recently reported. This talk will concern more recent results in our examination
of the reactivity of these unusual molecules.
INOR 484
Mobile zinc signaling in the brain – learning, memory, hearing, olfaction, and vision
Stephen J. Lippard, [email protected]. Chemistry, Massachusetts Institute of
Technology, Cambridge, Massachusetts, United States
Zinc released from glutamatergic vesicle in the hippocampus, auditory cortex, olfactory bulb, and optic nerve has both
physiological and pathological consequences. Through the use of chelating agents that rapidly sequester this mobilized
zinc, and by the application of fluorescent sensors to detect the time- and position-sensitive movement of the ion, we have
recorded (i) single synapse release of vesicular zinc in the hippocampus; (ii) modulation of extrasynaptic NMDA receptors
by synaptic and tonic zinc in cartwheel cells, a class of inhibitory interneurons in the molecular layer of the dorsal cochlear
nucleus that receive glutamatergic input from synaptic zinc-rich parallel fibers; (iii) release of zinc from glomeruli in the
olfactory bulb upon electrophysiological stimulation in slices and as delineated in sensory maps produced in live animals
following exposure to specific odorants; and (iv) mobile zinc release in the inner plexiform layer of the retina following
optic nerve crush, a phenomenon used to guide the application of a fast zinc chelator as a means to promote optic nerve
regeneration following crush. This work was supported by a grant from the National Institute of General Medical Sciences.
INOR 485
Covalency in lanthanides
Stosh A. Kozimor1, [email protected], Jason M. Keith2, Alison B. Altman5, Enrique R.
Batista3, David L. Clark4, Richard L. Martin1, Stefan G. Minasian5, [email protected]
Tyliszczak5, David K. Shuh5, Marianne P. Wilkerson1. (1) Los Alamos Natl Lab, Los
Alamos, New Mexico, United States (2) Dept of Chemistry, Colgate University,
Hamilton, New York, United States (3) Theoretical Division, Los Alamos National
Laboratory, Los Alamos, New Mexico, United States (4) Natl Security Education Center,
Los Alamos National Laboratory, Los Alamos, New Mexico, United States (5) Lawrence Berkeley Natl Lab, Berkeley,
California, United States
Covalency is a fundamental concept in chemistry used to describe chemical bonding in s-, p-, d-, and f-block elements.
Recently, we have made use of Cl K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional
theory (TDDFT) to evaluate covalency in Ln–Cl (Ln = lanthanide) bonds of Oh-LnCl6x- (LnIII = Ce, Nd, Sm, Eu, Gd; LnIV =
Ce) anions. The results have been evaluated as a function of (1) the lanthanide metal identity, which was varied across
the series, and (2) the lanthanide oxidation state (when practical, i.e. formally Ce III and CeIV). Our unexpected observation
of lanthanide 4f- and 5d-orbital participation in covalent bonding will be presented in the context of recent studies on both
tetravalent transition metal and actinide hexahalides, MCl62- (M = Ti, Zr, Hf, U, Pu).
INOR 486
Uranium-element multiple bond formation facilitated by redox-active pyridine(diimine) ligands: Synthesis,
characterization, and reactivity of a unique class
Suzanne C. Bart, [email protected]. Department of Chemistry, Purdue University, West Lafayette, Indiana, United
States
Pyridine(diimine) ligands have proven to be a versatile framework for supporting transition metals due to their ability to
exist in a variety of oxidation states. Recently, our laboratory has synthesized a series of tetravalent uranium complexes
with reduced pyridine(diimine) ligands, as mono-, di-, tri-, and tetraanions. The electrons stored in these ligands facilitate
multi-electron reactivity, enabling the synthesis of uraniumelement multiple bonds. These unique species and their
precursors have been characterized using a variety of spectroscopic and computational methods in addition to X-ray
crystallography, revealing interesting electronic structures in all cases. Additionally, the reactivity of the multiply bonded
species towards a variety of small molecules has also been tested and will be discussed.
INOR 487
Reactions of oxygen with late transition Metal Complexes
Karen I. Goldberg, [email protected]. Univ of Washington, Seattle,
Washington, United States
With the goal of developing organometallic catalysts that selectively oxidize hydrocarbons using molecular oxygen, our
laboratory has been investigating the reactions of a range of late transition metal compounds with molecular oxygen. The
formation of superoxo and peroxo complexes, the insertion of oxygen into metal-hydride and metal-alkyl bonds to form
metal-hydroperoxides and metal-alkylperoxides, respectively, and oxygen-induced reductive elimination have all been
observed. Mechanistic investigations and our nascent understanding of a variety of these oxygen reactions with late
transition metal complexes will be presented.
INOR 488
DFT studies of Cp2An(P)2 complexes as catalysts for pyridine and thophene ring opening
Enrique R. Batista1, [email protected], Aaron W. Pierpont1, Richard L. Martin1, Nicholas E. Travia2, Jaqueline L. Kiplinger2.
(1) Theoretical Division, Los Alamos National
Laboratory, Los Alamos, New Mexico, United States (2) MPA Division, Los Alamos
National Laboratory, Los Alamos, New Mexico, United States
As fossil fuels become more scarce and alternative energy sources are not ready to take their place new low-quality dirty
petroleum feedstocks become more needed options. Although these low-quality feedstocks are abundant, they typically
contain large amounts of heterocyclic organonitrogen and organosulfur compounds as impurities. To avoid the relase of
greenhouse gasses these feedstocks need to be “cleaned” via hydrodenitrogenation (HDN) and desulfurization (HDS) to
remove NH3 and H2S impurities. In this talk, DFT calculations are performed for the actinide systems Cp2Th and Cp2U.
Experimentally, these systems exhibit a rich chemistry towards heterocyclic substrates (C-H/C-N activation, ring-opening,
dearomatization). Computations will be performed to predict how well this chemistry extends to pyridine, thiophene, and
furan ring opening, as these have been some of the most difficult contaminants to process via conventional
HDN/HDS/HDO routes.
INOR 489
Pursuits of rare oxidation states in actinide chemistry
Mark R. Antonio, [email protected], Lynda Soderholm. Chemical Sciences &
Engineering Division, Argonne National Laboratory, Argonne, Illinois, United States
During our lifetimes, it is not likely that we will see the periodic table of the elements expand beyond Z = 118 to 172 as
suggested by Pekka Pyykkö (Phys. Chem. Chem. Phys., 2011, 13, 161). Rather, the best that we can hope to witness is
the discovery of a new vocabulary of oxidation states. In fact, there have been decades of research on transition-metaland f-elements alike to achieve rare—such as Jaqueline Kiplinger’s pentavalent uranium (5f 1) chemistry (Chem.
Commun., 2009, 3831)—as well as unusually low and unusually high states of oxidation. In this last pursuit, there has
been a resurgence of interest, both experimental and theoretical, in neptunium(VII) and plutonium(VII, VIII). These are the
subject of this talk. Although not as extreme as Pu(VIII), the solution structures and ground-state electronic properties of
Np(VII) and Pu(VII) are, nonetheless, unusual and not fully developed. For example, the results to be presented about the
f1 Pu(VII) ion will be shown to bear upon the issue of the possible existence of Pu(VIII) in strongly alkaline solutions
subjected to ozonation. In view of the profound reactivity predicted for Pu(VIII) in fluid media, it will take particularly
innovative synthetic chemistry—exactly like what our Cotton Award Winner is recognized for today—to isolate and
characterize a genuine Pu(VIII) species. Until that time, this work provides a definitive comparison of the coordination
environments of Np(VII) and Pu(VII) in alkaline solutions.
INOR 490
Perturbation of the electronic properties of non-innocent vanadium(V) complexes and the chemical properties of
vanadium and copper coordination complexes in inhomogeneous environments
Debbie C. Crans, [email protected], Irma Sánchez Lombardo, Jordan
Koehn, Estela Magallanes. Colorado State University, Fort Collins, Colorado, United
States
The effects of ligands and interfaces on vanadium and other metal complexes include changes in coordination complex
structure, stability, and reactivity. In the following presentation we discuss these effects and the nature of these changes.
Changes in ligands induced electronic changes in vanadium complexe's ranges from dramatic stabilization to rendering
the complex more redox active.1,2,3 The complexes properties can be monitored using solid and solution state 51V NMR
spectroscopic methods.1,2,3 Changes in complex properties induced by changes in its environment can lead to compound
hydrolysis or to stabilization of the complex, as reported for bis(maltolato)oxovanadium(IV)4 and the
oxovanadium(V)catecolate 1:1 complex, respectively.5 Changes in the properties of these complexes include proton
transfer6 and electron transfer-reactions7 and have been demonstrated in a series of vanadium and cobalt complexes.
Preliminary studies of amino acid and peptides complexes of Cu2+ were also performed to examine whether the effects of
the environment on coordination chemistry extend to copper coordination chemistry.
References
1. P. B. Chatterjee, O. Goncharov-Zapata, L. L. Quinn, G. Hou, H. Hamaed, R. W. Schurko, T. Polenova, and D. C. Crans
2.
3.
4.
5.
6.
7.
Inorg. Chem. 2011, 50, 9794-9803.
J. J. Smee, J. A. Epps, K. Ooms, S. Bolte, T. Polenova, B. Baruah, L. Yang, W. Ding, M. Li, G. R. Willsky, A. la Cour, O.
P. Anderson, D. C. Crans J. Inorg. Biochem. 2009, 103, 575-584.
P. B. Chatterjee, O. Goncharov-Zapata, G. Hou, T. Polenova, and D. C. Crans Eur. J. Inorg. Chem. 2012, 4644-4651.
D. C. Crans, S. Schoeberl, E. Gaidamauskas, B. Baruah, and D. A. Roess J. Biol. Inor. Chem. 2011, 16, 961-972.
B. G. Lemons, D. Richens, M. D. Johnson, A. Anderson, M. A Sedgwick, and D. C. Crans New J. Chem. 2013, 37, 75-81.
D. C. Crans and N. E. Levinger Acc. Chem. Res., 2012, 45, 1637-1645.
M. D. Johnson, B. B. Lorenz, P. C. Wilkins, B. G. Lemons, B. Baruah, N. Lamborn, M. Stahla, P. B. Chatterjee, D. T.
Richens and D. C. Crans Inorg. Chem. 2012 51 (20), 2757-2765.
INOR 491
Formation, characterization, and uses of metallacycles via coordination directed self-assembly
Peter J. Stang, [email protected]. Chem Dept, University of Utah, Salt Lake City, Utah, United States
Both an overview and our latest results in the coordination driven self-assembly of supramolecular metallacycles will be
presented
INOR 492
Interplay of metal ions and oxidative damage in DNA G-quadruplexes
Cynthia J. Burrows, [email protected]. Department of Chemistry, University of Utah, Salt Lake City, Utah, United
States
The folded structures of G-rich sequences in DNA and RNA are dependent on both the identity of the metal ion (K, Na, Li,
Mg or Ca) as well as the presence of oxidized base lesions in the sequence. The ability of G-quadruplex-forming
sequences to change shape based on the presence of various mono- and divalent metal ions as well as the role of
oxidized guanine sites will be discussed in the context of both the human telomeric sequence and various promoter
sequences.
INOR 493
Reduction chemistry with group 3 metals supported by a ferrocene diamide ligand
Paula Diaconescu, [email protected]. UCLA, Los Angeles, California, United States
Four types of mechanisms have been widely accepted for the C-H activation reaction involving transition metals: oxidative
addition with electron-rich, low-valent late transition metals, electrophilic activation with electron-deficient late transition
metals, 1,2-CH addition across a metal-element multiple bond, and σ-bond metathesis with polarized metal-carbon bonds.
So far, σ-bond metathesis is the only mechanism identified for group 3 metals (scandium, yttrium, lanthanum, and the
lanthanides). We will discuss a
new type of C-H activation mediated by group 3 metals that cannot be classified as σbond metathesis. This type of C-H
activation is related to the oxidative addition mechanism with late transition metals since the products of this reaction are
metal hydride and metal alkyl complexes. However, because this C-H activation requires reducing agents and the
oxidation state of the metal center stays the same, we believe the term “reductive cleavage” is appropriate to describe it.
INOR 494
Uranium imido complexes: A window into actinide-ligand bonding and reactivity
James M. Boncella1, [email protected], Neil C. Tomson1, Enrique R. Batista2, [email protected], Brian Scott3. (1) MS J514,
Los Alamos National Laboratory, Los Alamos,
New Mexico, United States (2) Theoretical Division, Los Alamos National Laboratory,
Los Alamos, New Mexico, United States (3) Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
We have discovered convenient synthetic procedures for the preparation of mononuclear imido complexes of uranium (IV,
V and VI). These compounds have allowed us to explore and compare the reaction chemistry and bonding in uranium
complexes that have the same or very similar ligand sets in three different oxidation states. The U(VI) bis(imido)
complexes have unusual chemical shifts in their NMR spectra that have been ascribed to temperature independant
paramagnetism (TIP). Investigations into the electronic structure of these compounds that give rise to the observed TIP
will be discussed. The redox chemistry of these compounds will be also discussed as will the reactivity of the imido groups
with electrophiles. Changes in the reactivity of the imido groups as a function of oxidation state correlate with changes in
the calculated U-N orbital interactions that make up the uranium-nitrogen multiple bonds in these compounds. The
relationship between the observed reactivity and the evolving view of covalency in U-L bonding will be discussed.
INOR 495
Bimetallic hydrides inspired by the hydrogenase active sites
Thomas B. Rauchfuss1, [email protected], Geoffrey M. Chambers2, Ulloa C.
Olbelina1, Wang Wenguang1. (1) A131CSLS Box 60-6, University of Illinois, Urbana,
Illinois, United States (2) Chemistry, University of Illinois, Urbana-Champaign, Urbana,
Illinois, United States
This lecture will cover our work on bimetallic hydride complexes with the nominal connectivity Fe-H-Ni and Fe-H-Fe.
Unlike many hydrogen evolution systems, these bimetallic hydrides are characterizable and show no tendency to release
H2 by protonolysis. This difference merits explanation and comparisons as well with the enzymes. The isolability of
bimetallic hydrides offers the opportunity to examine their redox behavior, which opens the way for characterization of
mixed valence hydrides of the type Fe(II)-H-Fe(I) and Fe(II)-H-Ni(I). Finally we will discuss progress in manipulating the
stability and reactivity of species of the type Fe-Fe-H, where a role for Fe(I)-Fe(II)-H entities is implicated.
INOR 496
Enzyme-like behavior achieved with amino acids in the outer coordination sphere of H 2 oxidation catalysts
Wendy J. Shaw, [email protected], Arnab Dutta, Dan DuBois, John
Roberts. Pacific Northwest National Laboratory, Richland, Washington, United States
Hydrogenases interconvert H2 and protons at high rates and with high energy efficiencies, providing inspiration for the
development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically
active site have led to the synthesis of amino acid derivatives of [Ni(P R2NR'2)2]2+ complexes, [Ni(PCy2NAmino acid2)2]2+ (CyAA).
It is shown that these CyAA derivatives can catalyze fully reversible H2 production/oxidation, a feature reminiscent of
enzymes. The reversibility is achieved in acidic aqueous solutions, 1 atm 25% H 2/Ar, and elevated temperatures (tested
up to 70 ˚C) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. At pH=1 and
70 C, rates of up to ~300 s1 H2 production and 20 s-1 H2 oxidation 348 K are observed. The effect of higher pressure and
the behavior of complexes without an outer coordination sphere will be discussed. These observations demonstrate that
outer coordination sphere amino acids work in synergy with the active site and can play an equally important role for
synthetic molecular electrocatalysts as the protein scaffold does for redox active enzymes.
INOR 497
Theoretical design of hydrogen-evolving molecular electrocatalysts
Sharon Hammes-Schiffer, [email protected]. Department of Chemistry, University of
Illinois at Urbana-Champaign, Urbana, Illinois, United States
Molecular electrocatalysts play an essential role in a wide range of solar energy conversion processes. The objective of
electrocatalyst design is to maximize the turnover frequency and minimize the overpotential for the overall catalytic cycle.
Typically the catalytic cycle for hydrogen evolution is dominated by key proton-coupled electron transfer (PCET)
processes comprised of sequential or concerted electron and proton transfer steps. This talk will focus on theoretical
investigations of the mechanisms, thermodynamics, and kinetics of PCET processes in electrocatalytic cycles. Several
molecular electrocatalysts for hydrogen production will be discussed, including cobalt complexes with diglyoxime or
dithiolene ligands, as well as nickel complexes with pedant amines to facilitate proton relays. The calculations have
revealed linear correlations that can be used to predict the impact of modifying the ligands, substituents, or metal centers.
These theoretical studies are assisting in the interpretation of experimental data and the design of more effective
molecular electrocatalysts.
INOR 498
Molecular proton reduction catalysts in metal-organic frameworks
Sascha Ott, [email protected]. Department of Chemistry, Uppsala University, Uppsala, Sweden
Evolution has optimized Nature’s catalysts for millions of years to work under optimal conditions required for a specific
process. Hydrogenases (H2ases), in particular the [FeFe] H2ases, are an interesting example in this context as their active
site may have been present already in the primordial soup. Ligated exclusively by inorganic ligands, the diirron complex
however only unfolds its full catalytic potential when surrounded by the appropriate peptide framework.
Bioinorganic models that closely resemble the enzyme active site have been prepared, have however been found to be
comparably poor catalysts, despite of the high structural similarities between the natural and the synthetic systems.
Considering the discrepancy in performance, third and fourth coordination sphere effects provided by the peptide matrix
are obviously crucial.
In this presentation, we discuss a novel approach to potentially control such effects by immobilizing molecular proton
reduction catalysts into three-dimensional coordination polymers, so-called metal-organic frameworks (MOFs). We will
show that structurally demanding catalysts such as a model of the enzyme active site (see Figure) can be introduced into
MOFs to afford materials that are superior proton reduction catalysts compared to the analogous homogenous systems. A
long-term goal of the project is to investigate the effect the MOF matrix has on catalytic performance. First results in this
quest will be presented on catalyst-containing MOF films grown on different conducting substrates.
INOR 499
Production of C1 sources via reduction of CO2 on redox active iron ligand platforms
John D. Gilbertson, [email protected]. Chemistry, Western Washington University, Bellingham, Washington,
United States
The production of CO from CO2 is an attractive route to the utilization of CO2 as a C1 source. CO is produced industrially
by steam reforming fossil fuels to produce syngas,
and is a versatile chemical precursor and fuel. Our recent work on a synthetic cycle for the CO 2-to-CO conversion (with
subsequent release of CO) based on iron(II) and redox active pydridinediimine (PDI) ligands will be presented. The
production of syngas from CO2 and protons will also be discussed, as well as the investigation into CO release from
iron(II) by tuning the secondary coordination sphere of these complexes. Lastly, our work employing tandem catalysts to
study dihydrogen-derived hydride transfer reactions to multiple variants of the FePDI complexes under CO 2 will also be
highlighted.
INOR 500
Harnessing heterobimetallic complexes for CO2 activation and reduction
Jenny Yang, [email protected], Steve Poteet, Jacob Ritter. Chemistry, University of
California, Irvine, Irvine, California, United States
Bimetallic interactions have been shown to facilitate CO2 reduction in a variety of synthetic systems, and is also believed
to be important in the active site of the CO Dehydrogenase enzyme. We have investigated this cooperative interaction
using a modular ligand set. Our general approach has been to pair an electron rich transition metal with a more Lewis
acidic transition metal or non-redox active metal. Our efforts towards cooperative activation and reduction of CO 2 will be
described.
INOR 501
Deep photoreduction of carbon dioxide to methanol and formate by ruthenium polypydridyl chromophores with
pendant pyridyl sites
Frederick M. MacDonnell, [email protected], Matthew West, David J. Boston, Norma de Tacconi. Univ of Texas,
Arlington, Texas, United States
The photochemical reduction of CO2 to deep reduction products, such as methanol, represents a net six electron process
and is difficult to reconcile with the one photonone electron stoichiometry of photochemical excitations, unless the process
can be broken down into sequential one-electron steps. Bocarsly and co-workers have shown that pyridine is a functional
electrocatalyst for the CO2 to methanol process, albeit with some dependence on the electrode material suggesting an
active role in the reduction mechanism by the metallic surface. 1 We recently demonstrated that a homogeneous mixture of
[Ru(phen)3]Cl2/pyridine/ascorbate yields formate and to a lesser extent methanol upon visible light irradiation. 2 This paper
will present our recent studies in this area in which we constructed a Ru chromophore-pyridine unimolecular catalyst in an
effort to improve performance. We have also expanded our studies to additional Rubased chromophores. The successes,
limitations, and future directions of this research will be presented.
References
1.
Cole, EB; Lakkaraju, PS; Rampulla, DM; Morris, AJ; Abelev, E; Bocarsly, AB. J Am Chem Soc. 2010 132(33),
11539-51.
2.
Boston, DJ; Xu, C.; Armstrong, DW; MacDonnell, FM J. Am. Chem. Soc., 2013, 135 (44), 16252–16255. Boston,
DJ; Pachon, YMF; Lezna, RO; de Tacconi, NR; MacDonnell, FM Inorg. Chem. 2014 53(13), 6544-6553.
INOR 502
Magic-size II-VI nanoclusters as semiconductor precursors
Yuanyuan Wang2, Yang Zhou2, Fudong Wang3, William E. Buhro1,
[email protected]. (1) Washington Univ, Saint Louis, Missouri, United States (2)
Chemistry, Washington University, Saint Louis, Missouri, United States
Ideal molecular inks for semiconductor processing should consist of soluble species kinetically stabilized by labile ligands,
and having the stoichiometries (compositions) of the target semiconductors. The so-called “magic-size” nanoclusters of
the II-VI semiconductors may be capable of this role. We and others have recently described the isolation and properties
of amine derivatives of the discrete nanoclusters (CdSe) 13 and (CdSe)34. We have also reported their facile conversion to
CdSe nanocrystals under extremely mild conditions, even at room temperature. We have now isolated amine derivatives
of discrete magic-size nanoclusters of CdS, ZnS, ZnSe, CdTe, and ZnTe. Their characterization and conversion to
crystalline semiconductors will be presented.
INOR 503
High throughput investigations of colloidal metal chalcogenide nucleation and growth
Jonathan S. Owen1, [email protected], Mark P. Hendricks1, Michael P.
Campos1, Suk Ho Hong1, Gregory T. Cleveland1, Emory Chan2. (1) Chemistry,
Columbia University, New York, New York, United States (2) The Molecular Foundry, MS:67-4112, Lawrence Berkeley
National Laboratory, Berkeley, California, United
States
Thio- and selenoureas can be conveniently prepared in single steps from commercially available starting materials. By
adjusting their organic substituents, the rate of their reaction with metal surfactant complexes can be adjusted and a
desired nanocrystal size can be prepared in quantitative yield without otherwise adjusting the crystallization medium.
Using this method of tuning the rate, we have probed the temperature dependence of nucleation and growth steps. I will
describe our current understanding of homogeneous nucleation and growth mechanisms and the important role of
precursor conversion kinetics in homogeneous nucleation and growth processes.
INOR 504
Photochemical reactions of semiconductor nanocrystals coupled with redox catalysts
Gordana Dukovic, [email protected]. Dept of Chemistry and Biochemistry,
University of Colorado Boulder, Boulder, Colorado, United States
We have assembled hybrid nanostructures that couple light harvesting II-VI nanocrystals with redox catalysts that perform
proton reduction and water oxidation. The functionality of such hybrid structures depends strongly on the charge transfer
kinetics between the photoexcited nanocrystal and the catalyst. We utilize ultrafast transient absorption spectroscopy to
examine the dynamics of nanocrystal-catalyst charge transfer and the competitiveness of this process with the energywasting charge recombination. Our recent findings identifying kinetic bottlenecks for photochemistry will be discussed.
Our ongoing efforts to design nanocrystal structure and surface chemistry to enhance the kinetic competitiveness of the
photochemical pathways will be described.
References:
M. B. Wilker, K. E. Shinopoulos, K. A. Brown, D. W. Mulder, P. W. King, G. Dukovic. “Electron transfer kinetics in
CdS nanorod-[FeFe] hydrogenase complexes an implications for photochemical H2 generation.” Journal of the American
Chemical Society, 2014, 136, 4316-4364.
1.
H-W. Tseng, M. B. Wilker, N. H. Damrauer, G. Dukovic. “Charge Transfer Dynamics between Photoexcited CdS
Nanorods and Mononuclear Ru Water-Oxidation Catalysts” Journal of the American Chemical Society, 2013, 135, 33833386.
2.
K. A. Brown, M. B. Wilker, M. Boehm, G. Dukovic, P. W. King. “Characterization of photochemical processes for
H2 production by CdS nanorod-[FeFe] hydrogenase complexes.” Journal of the American Chemical Society, 2012, 134,
5627–5636.
3.
INOR 505
All-inorganic design of colloidal nanocrystals: New inorganic ligands and new atomistic insignts into their
surface binding
Maksym Kovalenko, [email protected]. Lab Inorganic Chem, HCI H 123, ETH Zurich, Zurich, Switzerland
Chemically synthesized inorganic nanocrystals are considered to be promising building blocks for a broad spectrum of
applications in solid-state devices. To achieve high degree of electronic coupling, the nanocrystal packing, surface
chemistry and surrounding medium need to be properly designed. With the advent of inorganic capping ligands [1], a
considerable progress has been demonstrated towards nanocrystal-based photovotaics, photodetectors, electronics,
thermoelectrics, Li-ion batteries and other applications.
The search for new inorganic ligands, which enhance both the individual and collective properties of nanocrystals,
remains an important task. To this end, we have shown recently that metal halide complexes such as methylammonium
lead halides can act as versatile capping ligands, providing high colloidal stability and efficient electronic passivation [2].
Very little is known about the atomistic details of the interface between the nanocrystal surface and inorganic capping
ligands. We will discuss our most recent work in this direction, including novel surface-enhanced nuclear-magnetic
resonance spectroscopy [3], and comprehensive spectroscopic study (XAS, far-IR, NMR, Raman) on the binding of
halometallate and chalcogenidometallate anions to the nanocrystal surface [unpublished].
[1] Kovalenko, M. V.; Scheele, M.; Talapin, D. V. Science 2009, 324, 1417.
[2] D. N. Dirin, S. Dreyfuss, M. I. Bodnarchuk, G. Nedelcu, P. Papagiorgis, G. Itskos, and M. V. Kovalenko. J. Am. Chem.
Soc., 2014, 136, 6550–6553.
[3] L. Protesescu, A. J. Rossini, D. Kriegner, M. Valla, A. de Kargommeaux, M. Walter, K. V. Kravchyk, M. Nachtegaal, J.
Stangl, B. Malaman, P. Reiss, A. Lesage, L. Emsley,
C. Coperet, and Maksym V. Kovalenko. ACS Nano, 2014, 8, 2639–2648.
INOR 506
Novel fabrication strategies for heterostructured PbS and PbSe QDs via controllable cation exchange reactions
Matt C. Beard1, [email protected], Jianbing Zhang2, Joseph Luther2, Elisa Miller2,
Jianbo Gao4. (1) National Renewable Energy Lab, Golden, Colorado, United States (2)
National Renewable Energy Laboratory, Golden, Colorado, United States (4) Chemistry Department, UC Berkeley,
Berkeley, California, United States
We developed a cation exchange synthesis to produce PbSe and PbS QDs directly from CdSe and CdS starting QDs.
The cation exchange reaction is promoted by the using PbCl2 in oleylamine which forms a gel at room temperature. We
show that PbX QDs prepared from CdX QDs via the cation exchange reaction has improved airstability and PbSe QD-PV
devices can be fabricated with > 6% power conversion efficiency in ambient conditions. This new Cd 2+ à Pb2+ cation
exchange reaction provides a new tool in tailoring the composition and shape of the resulting nanocrystal. We show that
anisotropic nanocrystals can be formed in a controllable fashion. We explore how the optical properties change upon
gradual increase of PbS and PbSe within a heterostructured quasi-spherical nanocrystal.
INOR 507
Near-infrared photoluminescence enhancement in Ge/CdS and Ge/ZnS core/shell nanocrystals: Utilizing IV/II–VI
semiconductor epitaxy
Javier Vela-Becerra, [email protected]. Dept of Chem, Iowa State University, Ames, Iowa, United States
Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via
strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for
applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a
common strategy employed in the synthesis of highly luminescent II–VI, III–V and IV–VI semiconductor quantum dots.
Here, we use relatively unexplored IV/II–VI epitaxy as a way to enhance the photoluminescence and improve the optical
stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with
crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and
reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray
spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial
monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS
nanocrystals. The presence of an epitaxial II–VI shell greatly enhances the near-infrared photoluminescence and
improves the photoluminescence stability of Ge. Ge/II–VI nanocrystals are reproducibly 1–3 orders of magnitude brighter
than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest
radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II–VI
nanocrystals. We expect this synthetic IV/II–VI epitaxial approach will lead to further studies into the optoelectronic
behavior and practical applications of Si and Ge-based nanomaterials.
INOR 508
Infrared Spectroscopic tracking of Q-state particle formation in ionomers
Felicity A. Meyer1,3, [email protected], Jonathan H. Doan3, Erin Kingston4, Kierstyn P. Anderson2, Andy K. Vong2,
Eugene S. Smotkin3. (1) Chemistry, Simmons
College, Boston, Massachusetts, Afghanistan (2) Chemistry and Chemical Biology,
Northeastern University, Boston, Massachusetts, United States (3) Northeastern University, Boston, Massachusetts,
United States
CdS quantum dots were prepared by exposing Cd2+ exchanged sulfonated poly(ether ether ketone), (SPEEK), on a high
vacuum line, to H2S. The progress of Cd2+ exchangesite sulfidation is monitored by the peak splitting of IR bands
associated with the gradual conversion of ion exchanged sites to the protonated ionomer with near neighbor quantum
dots. Quantum dot grain sizes are tuned by diluting the Cd2+ exchange
solution with unreactive lithium ions before exposure to H2S. Quantum dot loaded SPEEK membranes with finely tuned
particle sizes can be recast to fabricate composite films containing an array of pixel-like quantum dots emitting at discreet
band gap energies.
INOR 509
Ultrasmall Cu nanoparticles: A greener synthesis and catalytic studies
Gillian A. Ferko, [email protected], Aaron D. Brumbaugh, Sarah K. St
Angelo. Department of Chemistry, Dickinson College, Carlisle, Pennsylvania, United
States
Ultrasmall copper nanoparticles (CuNPs) have been synthesized using lemongrass tea as a reducing agent. The nonplasmonic nanoparticles have been characterized by UVvis, NIR, electron microscopy, and elemental analysis
techniques. Electron microscopy has shown that the CuNPs have diameters of less than 5 nm. Experiments to determine
the reducing capacity of the lemongrass tea have been performed. The potential use of the CuNPs as catalysts for model
organic reactions has been studied. Example reactions have shown that the CuNPs can catalyze the reduction of organic
compounds in aqueous solution.
INOR 510
Synthesis, characterization, and utility of trifluoroacetic acid and fluoroalkoxy lanthanide precursors for
production of fluorinated lanthanide nanomaterials
Daniel Yonemoto1, [email protected], Timothy J. Boyle2, Michael L. Neville4, Ryan
F. Hess3, Samuel P. Bingham1. (1) Sandia National Laboratories, Albuquerque, New
Mexico, United States (2) Advanced Materials Laboratory, Sandia National
Laboratories, Albuquerque, New Mexico, United States (3) MS 0892, Sandia National Laboratories, Albuquerque, New
Mexico, United States
In order to reduce the US’s dependence on foreign oil supplies, the use of geothermal wells is being explored as an
alternative means to generate electricity. Critical to developing this technology is the ability to track the underground water
flow. For this project we are developing a series of ion sensors that can survive the harsh conditions of these more than 5
km deep wells that is capable of doing real time tracking of the water flow. One of the materials for the sensor platform is
lanthanide fluoride (LnF3). In particular, we have focused on nanomaterials due to their high surface area, which may
allow for a more sensitive detector. This talk reports on the synthesis of the trifluoroacetic acid (H-TFA) and fluorinated
alcohol lanthanide derivatives and their conversion to LnF 3 nanomaterials. Details of the synthesis, characterization and
processing will be reported.
This work was supported by the Geothermal Technologies Offices of the Department of Energy at Sandia National
Laboratories. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a
wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DE-AC04-94AL85000
INOR 511
Phenoxy-mercapto derivatives of group 4 alkoxides as core-shell precursors to group 4 ceramic-coinage metal
nanomaterials
Michael L. Neville1,3, [email protected], Timothy J. Boyle2, Ping Lu1, Marie V.
Parkes1. (1) Sandia National Laboratories, Albuquerque, New Mexico, United States (2)
Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, New
Mexico, United States (3) University of New Mexico, Albuquerque, New Mexico, United
States
Core-shell nanomaterials have attracted interest based on their potential to demonstrate modified properties from the
individual component’s characteristics. The shell feature offers many advantages to the core such as increasing: stability,
solubility,
biocompatability, controlled release/access, to mention a few. For coinage metal cores (i.e., Cu, Ag, Au), the coating of
this metal with ceramic oxides by soft chemistry methods is limited. Group 4 ceramic materials are of interest due to their
widespread utility in a variety of applications. A search of the literature indicates there are very few M(OR-SH)4
derivatives available for the Group 4 congeners. Therefore, we undertook the development of a set of [M(OR)4-x(O-RSH)x] precursors. For this effort, we focused on the 4-mercaptophenol (H-4MP) derivatives of the Group 4 species. The
products are identified as [(HOBut)(4MP)3M(µ-4MP)]2 where M = Ti, Zr, Hf . The Cu, Ag, and Au nanoparticles were
mixed with the metal alkoxide precursors to yield the core-shell nanomaterials. The synthesis and characterization of
these precursors and the generated core-shell nanomaterial’s will be explored. This work was supported by the
Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories. Sandia National
Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of
Lockheed
Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DEAC04-94AL85000
INOR 512
Oxidizing aldehydes with water: Catalysts for the aldehyde-water shift
Jeremy C. Tran2, [email protected], Timothy Brewster2, Dennis M. Heinekey2,
Karen I. Goldberg1. (1) Univ of Washington, Seattle, Washington, United States (2)
University of Washington, Seattle, Washington, United States
Carboxylic acids are ubiquitous in chemistry and find use in a variety of applications in both industry and in academic
research, including as polymer precursors, synthetic building blocks, and food preservatives. Modern routes to synthesize
these compounds often involve harsh conditions or reagents harmful to both the environment and human health. An
alternative synthetic route is the aldehyde-water shift reaction; in this relatively unknown reaction, an aldehyde is oxidized
by water to a carboxylic acid with release of molecular hydrogen. The use of water as both solvent and reagent and the
mild reaction conditions could potentially reduce the impact of aldehyde oxidation on the environment.
Two major classes of half-sandwich catalysts for this reaction have been investigated for activity in catalyzing this reaction
with a variety of aldehyde substrates: one series includes a bipyridine derivative with Ir(III), Rh(III), and Ru(II) metal
centers, while the other series features diamine ligands on Ru(II). Using 1H NMR and GC-FID to analyze reaction
products, many of the catalysts were observed to disproportionate aldehydes to alcohols and carboxylic acids in
competition with the desired dehydrogenative oxidation to carboxylic acids. Mechanistic studies and catalyst optimization
for selective dehydrogenative oxidation are presented.
INOR 513
Multifunctional nanoclusters for biomedical applications
Samuel Park1, [email protected], Suehyun K. Cho2, Wounjhang Park3. (1) University of Colorado Boulder,
Superior, Colorado, United States (2) ECEE, University of Colorado Boulder, Boulder, Colorado, United States (3)
University of Colorado at Boulder, Boulder, Colorado, United States
We report the development of multifunctional nanocluster composed of upconversion nanoparticle (UCNP) and gold
nanorod (AuNR). Antibody to epidermal growth factor receptor (αEGFR) is further conjugated with the nanocluster so as
to demonstrate specific binding to the EGFR-expressing bladder cancer cells and subsequent thermal ablation of the cells
upon near-infrared (NIR) irradiation.
AuNRs and UCNPs are synthesized by the methods reported in the literature. Since UCNPs are synthesized in an organic
solvent, surface modification is needed to make them water soluble and also to enable the subsequent coupling with
AuNR. For this, we use poly(maleic anhydride-alt-1-octadecene) (PMAO). By mixing PMAO and UCNPs in toluene,
PMAOs are attached on the UCNP surface through hydrophobic interaction. Upon subsequent addition of heterofunctional
PEG, the amine group of the PEG binds with PMAO, producing carboxylic groups. This consequently makes the polymer
hydrophilic and thus the coated UCNPs water soluble. The carboxylic groups are also used to attach αEGFR. Finally, the
thiol groups on the free ends of the PEGs are used to bind with AuNR, completing the nanocluster.
The synthesized nanoclusters are characterized by electron microscopy, optical microscopy and in vitro cell ablation
experiments. Electro microscopy showed the successful formation of nanoclusters made of UCNPs and AuNRs.
Fluorescence and dark-field optical microscopy revealed the presence of UCNPs, AuNRs and αEGFR on the cell
membranes. Finally, NIR laser irradiation led to selective cell killing by thermal ablation.
The successful demonstration of UCNP-AuNR nanocluster opens a door to new diagnostic and therapeutic approach for
cancer.
Scanning electron micrograph of UCNP-AuNR nanoclusters
INOR 514
Student explains international undergraduate research and cultural experiences
Ashlie Walker1, [email protected], Guy Royal2, Timothy J. Hubin1, Randy
Duran3. (1) Chemistry, Southwestern Oklahoma State University, Weatherford,
Oklahoma, United States (2) Université Joseph Fourier, Grenoble, France (3)
Chemistry, Louisiana State University, Baton Rouge, Louisiana, United States
A Louis Stokes Alliance for Minority Participation (LSAMP-NSF) undergraduate student discusses how her undergraduate
studies in Weatherford, Oklahoma progressed to a NSF funded international Research Experience for Undergradutes
(REU) in Grenoble, France. The focus will be how to become a successful undergraduate researcher,get involved with the
LSAMP program, apply for international REU’s, and what it is like to do research and the cultural experiences the students
will have. This presentation will give a personal account of how to approach a successful undergraduate chemistry career
and inspire others to take advantage of international opportunities in undergraduate chemistry research.
INOR 515
Computational and synthetic study of organic-inorganic conjugate dyes for solar energy harvesting
Robert E. Bachman1, [email protected], Ava E. Connor1, Sara A. Parks1, Michelle R. Leidy1, Nathan J.
Deyonker2. (1) Department of Chemistry, The University of the South, Sewanee, Tennessee, United States (2)
Department of Chemistry, Univeristy of Memphis, Memphis, Tennessee, United States
Interest in “organic” photovoltaic (OPV) devices such as dye-sensitized and heterojunction solar cells has increased
dramatically in recent years. Compared with traditional semiconductor based cells, OPV systems offer potential
advantages including low-cost manufacturing and lightweight, flexible architectures. In order to harvest solar energy,
molecularly based OPV devices typically rely on one of two classes of photoactive molecules—metal complexes of
polypyridines or highly conjugated organic molecules—each of which possess intrinsic advantages and disadvantages.
Recognizing the possibility of creating beneficial synergies by combining the properties inherent in these two classes of
dyes in a single system, we have recently begun to explore a new class of dyes based on conjugation of an inorganic and
an organic chromophore. Specifically, we have used both computational and synthetic approaches to examine the
conjugation of naphthalenemonoimide (NMI) and perylenemonoimide (PMI) moieties to aromatic diimines such as 1,10phenanthroline, which can in turn be utilized as a platform for the construction of metal complexes. In addition to
presenting our initial work on the the preparation and characterization of these conjugates, we will discuss the use of
theory as a guide to target selection.
INOR 516
Targeting mitochondrial DNA
Shana O. Kelley, [email protected]. University of Torotno, Toronto, Ontario, Canada
The mitochondria of human cells play a central role in the life and death of the cell due to the diverse processes and
proteins - such as energy production and cell death regulators - that it houses. The role of mitochondria in cancer
progression and tumorigenesis has been widely acknowledged. A major challenge to the study of mitochondrial processes
and the development of mito-targeted therapies is presented by the impermeability of the innermost mitochondrial
membrane and its highly negative membrane potential, which exclude most exogenous molecules from the organelle. We
have developed a new class of peptide-based mitochondria-targeting vectors that can deliver various cargos to this
previously impenetrable organelle. These vectors can be used to understand the chemical requirements for mitochondrial
entry, to study the effects of mitochondrial DNA damage, and to establish the presence of proteins not previously included
in the mitochondrial proteome. Insights into the unique chemical and biochemical features of this organelle gained from
the use of these conjugates will be presented.
INOR 517
Novel development of electrolytes in lithium ion battery
Yasutaka Tanaka, [email protected]. Shizuoka University, Hamamatsu Shizouka, Japan
The development of rechargeable batteries especially for vehicle installation is aiming at those to be small and light. The
other urgent requirement is that the batteries be longlived and functioning at high and low temperature. Attentions have
been focused on exploring novel materials such as electrodes and electrolytes involving electrolyte additives so as to
overcome issues above. On one hand boron is the element possessing low atomic number of five and poor flammability
indicating that this is a preferable element for battery materials. In particular it has already been adopted in LiBF 4, LiBOB,
and so on. The unique chemical property which boron has is attributed to the vacant p-orbital on it. The orbital enables
accepting a pair of electrons to result in facilitating the dissociation of supporting salts (Figure 1(a)) and withdrawing the
electrons from other electrolyte molecules via intermolecular interaction (Figure 1(b)). We have discovered that boric
esters (1) are functioning as electrolyte solvents in a lithium ion battery. When 1 included the electron withdrawing
element or group such as fluorine or nitrile the electrolyte itself exhibited the oxidation potential of over 5.0 V. We have
also found chemical and electrochemical properties of cyclic boric esters of alkoxyboroxines (2, Figure 1(c)). When a
small amount of 2 was added into the electrolyte as an additive the battery cell showed a stable maintenance ratio of
capacity as compared with no additives. This seems results from the solid electrolyte interface formation containing boron
elements. We have eventually realized the importance of theoretical calculation such as molecular orbital method, density
functional theory, and molecular dynamics simulation when design these materials because of recent decrease in the
calculation price and the development of useful graphic user interfaces.
Figure 1. Intermolecular interaction of boric ester (1) as Lewis acis, (a) with lithium salt and (b) with carbonyl compound as Lewis
base, and (c) chemical structure of alkoxyboroxine (2).
INOR 518
Peptide nucleic acids (PNAs) as diagnostic and therapeutic molecules
Eylon Yavin, [email protected]. Hebrew University of Jerusalem, Jerusalem,
Israel
PNAs are DNA mimics that consist of a neutral backbone allowing excellent hybridization to complementary DNA and
RNA targets.
In my talk I will describe our efforts for designing and using such molecules for cancer diagnostics and for down-regulating
gene expression in the lethal parasite P.
falciparum; the major cause of malaria.
We have previously shown that by designing a PNA molecule that targets the oncogenic form of kRAS (mutated kRAS)
we were able to detect this mutation in living cancer cells (1) as well as a lncRNA that is highly expressed in colorectal
cancer (2), by adopting the FIT (forced intercalation) approach described by Seitz and co-workers (3). We are currently
designing new fluorescent probes with the hope that these could be used in an in-vivo setting.
As a therapeutic approach I will discuss the use of PNA as a useful tool for gene silencing in Plasmodium falciparum.
PNAs, designed as specific antisense molecules, were conjugated to a cell penetrating peptide (CPP) to allow facile
internalization into P.
falciparum infected red blood cells. PNAs simply added to cell culture were found exclusively in infected erythrocytes. We
show that these PNAs specifically down regulated both a stably expressed transgene as well as an endogenous gene,
which significantly reduced parasites' viability (4).
References:
Kam et al., Mol. Pharm. 2012, 9(3), 685-693.
Kam et al., Cancer Lett. 2014, 352(1), 90-96.
Kohler et al., ChemBioChem 2005, 6, 69-77.
Kolevzon et al., Plos One 2014, 22:9(1), e86802.
INOR 519
Controlling molecular display and cell behavior with nanocrystals
Catherine J. Murphy, [email protected]. Box 59-6, Univ of Illinois at UrbanaChampaign, Urbana, Illinois, United
States
Inorganic nanocrystals made in aqueous solution invariably present a surface full of molecules and ions to the solvent.
How are these species quantified, and in the case of large adsorbates, how can their orientation or position be measured?
In this talk I will discuss methods to make these measurements, and show that nanocrystal surface chemistry can greatly
influence the interactions these crystals have with living cells. Long-term possibilities include reprogamming of cellular
behavior with enabling nanotechnology.
INOR 520
Sensitive and selective real-time electrochemical monitoring of DNA repair
Jason Slinker1, [email protected], Marc McWilliams1, Fadwa Anka3, Kenneth J.
Balkus2. (1) Physics, The University of Texas at Dallas, Richardson, Texas, United
States (2) Dept of Chemistry BE26, Univ of Texas, Richardson, Texas, United States (3) Chemistry, The University of
Texas at Dallas, Richardson, Texas, United States
Unrepaired DNA damage can lead to mutation, cancer, and death of cells or organisms. However, due to the subtlety of
DNA damage, it is difficult to sense the presence of damage repair with high selectivity and sensitivity. We have shown
sensitive and selective electrochemical sensing of 8-oxoguanine and uracil repair glycosylase activity within DNA
monolayers on gold by multiplexed analysis with silicon chips and low-cost electrospun nanofibers. Our approach
compared the electrochemical signal of electroactive, probe-modified DNA monolayers containing a base defect versus
the rational control of defect-free monolayers. We found damage-specific sensitivity thresholds on the order of femtomoles
of proteins and dynamic ranges of over two orders of magnitude for each target. Temperature-dependent kinetics were
extracted, showing exponential signal loss with time constants of seconds. Damage specific detection in a mixture of
enzymes and in response to environmental oxidative damage was also demonstrated. Nanofibers were shown to behave
similarly to conventional gold-on-silicon devices, showing the potential of these low-cost devices for sensing applications.
This device approach enables sensitive, selective, and rapid assay of repair protein activity, enabling a biological
interrogation of DNA damage repair.
INOR 521
Evolution of an idea born in my postdoc with Jackie Barton: From rhodiumpeptide conjugates to Alzheimer's
disease
Robert P. Houser, [email protected]. Chemistry & Biochemistry, University of
Northern Colorado, Greeley, Colorado, United States
Synthetic bioinorganic modeling chemistry can range from elegantly simple to intricately complex. What can be gained in
synthetic utility with simple ligands can be lost in their inability to mimic the complexities of metalloprotein sites. On the
other hand, overly engineered ligands that are designed to more precisely model the first and even second coordination
sphere of the metal site(s) in a metalloprotein may be unreasonably difficult to synthesize. And even when they can be
successfully synthesized, large and complex ligand often do not behave in the way for which they were designed as a
consequence of their larger number of degrees of freedom. It was the balance between these two extremes that framed
the launching point of my independent career in 1999 at the end of my postdoc in the Barton laboratory. The evolution of
the ideas that emerged from my DNA hydrolysis project with Jackie will be presented, starting with the Rh-peptide
conjugate that was designed to be a synthetic hydrolytic DNA cleavage agent, and ending with current investigations into
synthetic models of the copper redox chemistry hypothesized in the amyloid beta (Aβ) peptide associated with
Alzheimer’s disease.
INOR 522
Low temperature synthesis of (noncentrosymmetric) oxide-fluoride materials
Kenneth R. Poeppelmeier1, [email protected], Kelvin B. Chang1, Anastasiya
Vinokur1, Michael Marvel2. (1) Northwestern Univ, Evanston, Illinois, United States (2) Aurora University, Aurora, Illinois,
United States
Structures with deviations from Pauling’s second crystallographic rule (PSCR) can result in lower symmetry, including the
loss of an inversion center. According to PSCR, cations with the largest positive potential occupy sites with the largest
negative potential, and vice versa. One strategy to deviate from PSCR is to deviate from the valence matching principle,
which states that more stable structures form when the cation’s Lewis acidity closely matches the anion’s Lewis basicity.
Analysis of two polymorphs of KNaNbOF5 [1,2] demonstrates how violation of the valence matching principle can result in
a NCS compound. The NCS and polar polymorph contains a cationic network whose average Lewis acidity is lower than
that of the centrosymmetric polymorph. The slightly less acidic cationic network that corresponds to the polar polymorph
can be achieved synthetically if the K:Na ratio in the reaction solution is greater than 1:1 because the Lewis acidity of K is
less than that of Na [3]. The Lewis acidity of the reaction solution therefore matches the Lewis acidity of the cationic
framework. This synthetic principle has led to a procedure to grow large single crystals suitable for single crystal property
measurements.
[1] M. Marvel, J. Lesage, J. Baek, P. Halasyamani, C. Stern, K. Poeppelmeier, J. Am.
Chem. Soc. 129, 13963 (2007).
[2] R. Pinlac, C. Stern, K. Poeppelmeier, Crystals, 1, 3 (2011).
[3] K. Chang, A. Vinokur, R. Pinlac, M. Suchomel, M. Marvel, K. Poeppelmeier, Inorg. Chem. 53, 6979 (2014).
INOR 523
Low temperature synthesis of bimetallic carbide nanomaterials and their electrocatalytic activity
Samantha M. Schmuecker, [email protected]. Chemistry, University of Wyoming, Laramie, Wyoming, United
States
Metal carbides are good for everything from automotive parts, tool blades and bits, to electronics and catalysts. However
the high temperatures traditionally used to synthesize these materials causes agglomeration and dramatically decreases
the surface area of the final product. Thus very few methods have been developed for the synthesis of metal carbide
nanomaterials, especially materials that include multiple metals. Using a salt flux technique, we have synthesized several
bimetallic carbides as nano-sized materials that are unattainable through tradition solid state methods. These
nanostructured carbides have high surface area and are potential low cost catalysts for a variety of energy related
reactions including HER, ORR, and OER. Monometallic carbides have been used previously for these reactions but
bimetallic carbides have additional metals and crystal structures which provide a method for further optimization.
Bimetallic carbides of Nb, Ta, Cr, Mo, and W were synthesized because of their durability and previous catalytic studies.
These combinations of the bimetallic carbides have been synthesized with composition control and provide a wide variety
of materials for testing catalytic activity compared to their monometallic counterparts.
TEM image and SAED of Tantalum Tungsten Carbide
INOR 524
Single source precursor approach to metastable molybdate phases
Allen W. Apblett1, [email protected], Ahmed M. Moneeb1, Abdullah
Alabdulrahman2, Abdulaziz Bagabas2, Cory Perkins3. (1) Chemistry, Oklahoma State University, Stillwater, Oklahoma,
United States (2) KACST, Riyadh, Saudi Arabia
Barium molybdenum oxides are ceramic materials with numerous applications in electronics, catalysis, scintillators, and
phosphors. They often require high temperatures and extended time to be prepared by the ceramic method. For example
the synthesis of Ba2Mo2O7 requires over 300 hours at 500˚C. Higher temperatures cannot be used due to
disproportionation into BaMoO4 and MoO3. We have developed a low-temperature rapid synthesis for this material via a
single source precursor route. Barium benzilate was reacted with molybdenum trioxide to produce a compound that
contained a cismolybdenyl moiety complexed by two doubly-deprotonated benzilate ions. Two of the resulting anions
were complexed to barium via one of their molybdenyl oxo groups. Thermal decomposition of this precursor produces
Ba2Mo2O7 with considerable energy savings over the ceramic method. Using a similar approach, it was also possible to
prepare the metastable phase, beta-NiMoO4, an important catalyst material.
INOR 525
Mechanistic studies in kinetically controlled solid state synthesis: The case of [(SnSe) 1.15][VSe2]
Marco Esters, [email protected], Matthias Falmbigl, David C. Johnson. Chemistry,
University of Oregon, Eugene, Oregon, United States
The mechanism of formation of a chemical compound is a key component to the understanding of controlling the reaction
path in chemical syntheses. While many mechanisms of molecular reactions have been discovered, the mechanistic
investigation of solid state reactions is still in its infancy due to the thermodynamic control of most systems, the complex
heterogeneous nature of reacting systems, the reactions occurring at interfaces, and the small ratio of interfaces to the
bulk, which makes suitable experimental probes difficult to find.
Ferecrystals are layered compounds with the general formula [(MSe) 1+δ]m[TSe2]n (M = RE,Bi,Pb,Sn; T = transition metal)
where m MSe and n TSe2 units are stacked along the c axis. They are synthesized by physical vapor deposition via a
multi-layer precursor consisting of layers of the individual elements with only a few Ångströms in thickness. Short diffusion
lengths and designable layering sequences in the precursor lead to a large variety of kinetic compounds with more than
20,000 potential compounds for m,n
≤ 10 for each combination of M and T. The precursors for ferecrystals have a large interface to bulk ratio and the
interfaces occur periodically, which makes them a good candidate for mechanistic studies since processes at the interface
can be probed much better than in traditional solids. Analogous to molecular chemistry, knowing the mechanism of
formation of these compounds could lead to the targeted synthesis of new materials with desired properties.
The compound [(SnSe)1.15][VSe2] was chosen as a model system for our mechanistic investigations. Specular XRD shows
the formation of superlattice peaks forming between 100 °C and 200 °C. DSC shows an exothermal event at around 130
°C, indicating a single nucleation event. To investigate the formation more in-depth, the precursor was annealed at
different temperatures (100 °C, 200 °C, 300 °C, and 400 °C) and analyzed using various diffraction, microscopy and
spectroscopy techniques. Inplane x-ray diffraction data which shows the simultaneous growth of SnSe and VSe2 hk0
reflections that grow in intensity and get sharper until 400 °C. Additionally, reflections of SnSe 2 can be observed which
vanish at 400 °C, coinciding with the loss of Se according to EPMA. EXAFS and TEM will be used to gain information
about local structures to get detailed insight about the structure of the intermediates.
INOR 526
Following the journey from aqueous polyoxometalate to metal oxide
Yu Hou, Dylan Fast, Lauren B. Fullmer, May D. Nyman, Michelle Dolgos, [email protected]. Chemistry
Department, Oregon State University, Corvallis, Oregon, United States
Aqueous precursors tailored for solution deposition of thin film materials allow for the sustainable, simple, and low energy
production of advanced materials. However, the complex interactions between ions and water during dehydration
complicate the process. We have used lithium polyoxoniobate salts to understand the fundamental interactions of the
transition from precursor cluster to LiNbO3 oxide film. Small-angle Xray scattering of the solutions, total X-ray scattering of
intermediate gels, and morphological and structural characterization of the films reveal the atomic level path between
these states. Our studies show that 1) Lithium-[H2Nb6O19]6- has drastically different solution behaviour compared to
lithium-[Nb6O19]8-, linked to the precursor salt structure 2) in both compositions, the intermediate gel preserves the
polyoxoniobate clusters and show similar local order and 3) the morphology and phases of deposited films reflect the ions
behaviour throughout the journey from cluster solution to metal oxide. While each solution-to-gel-to-solid system for
aqueous preparation of metal oxides has unique characteristics and challenges associated with its specific chemistry; the
universal importance of the interaction of ions with each other and with water in solutions and gels cannot be
underestimated.
INOR 527
Synthesis of metal sulfides in sulfur/iodine flux using furnace or microwave reactions
Ryan Groom, Susan E. Latturner, [email protected]. Chemistry, Florida State University, Tallahassee, Florida,
United States
Metal sulfides and metal sulfide iodides are formed from the reactions of metals and metalloids in a low melting flux
mixture of sulfur and iodine. Addition of iodine to sulfur lowers its melting point and viscosity, producing a melt that can be
used as a low temperature reactive solvent toward most metals. The S/I 2 flux syntheses of copper sulfides, tin sulfides,
and bismuth sulfide iodides were investigated using both furnace and microwave heating, exploring the effects of reaction
time and temperature. The unusual temperature regimes of this synthesis method allow for the isolation of metastable
phases such as Bi19S27I3.
INOR 528
Extraction behavior of mesoporous silica SBA-15 for soluble uranyl peroxo clusters
Yi Liu3, [email protected], Alicia Czarnecki4, Jennifer E. Szymanowski5, Mateusz
Dembowski2, Ginger Sigmon6, Peter C. Burns1. (1) Univ of Notre Dame, Notre Dame,
Indiana, United States (2) Chemistry and Biochemistry, University of Notre Dame,
Mishawaka, Indiana, United States (3) Dept Chemistry Biochemistry, University of Notre Dame, Notre Dame, Indiana, United
States (4) CEEES, University of Notre Dame, Notre Dame, Indiana, United States
Uranyl peroxo clusters are of potential importance for uranium transport and remediation in aqueous environments
because of their controllable size and topology, and because of their significant solubility in water. In this work, extraction
of soluble uranyl peroxo clusters in water, such as U60 and U24P, by SBA-15, a solid sorbent made of mesoporous silica,
has been studied. SBA-15 shows different extraction properties for U60 and U24P clusters. When the initial uranium
concentration increases from 260 ppm to 2200 ppm, the extraction performance of SBA-15 for U60 exhibits a maximum,
while the extraction quantity of U24P in SBA-15 keeps increasing. The influence of pH, cluster size, and contact time of
sorbent-cluster solutions on the extraction performance of SBA-15 was investigated using SAXS, ESI-MS, Raman, N2
adsorption-desorption, and TEM. To further improve the extraction efficiency of SBA-15 towards uranyl clusters, 3triethoxysilyl propylamine was grafted onto the inner surface of SBA-15. The functionalized sorbent shows significant
improved extraction properties towards both U60 and U24P.
INOR 529
Negative thermal expansion and other anomalous properties in rock salt ordered mixed metal fluorides M (II)ZrF6
with a ReO3-type structure
Justin C. Hancock1, Cody R. Morelock1, Leighanne C. Gallington1, Karena W.
Chapman2, Gregory J. Halder2, Benjamin S. Kaplan1, Angelo Bongiorno1, Chu Han1, Si
Zhou1, Angus P. Wilkinson1, [email protected]. (1) Georgia
Institute of Technology, Atlanta, Georgia, United States (2) X-ray Science Division,
Argonne National Laboratory, Lemont, Illinois, United States
Some materials of the type M(II)M'(IV)F6 have a cubic-ReO3 structure, which makes them good candidates for negative
thermal expansion (NTE). Additionally, the simplicity of the cubic-ReO3 structure is appealing for studies focused on
understanding the factors governing thermal expansion. There is little published thermal expansion data for this group of
materials. Variable temperature and high pressure powder diffraction have been used to examine the behavior of CaZrF 6.
It remains cubic down to at least 10K and displays strong NTE from < 10K to above 1000K with a room temperature linear
CTE of -11 ppm·K-1. Its NTE at room temperature and below is far stronger than that of ZrW 2O8. On compression in
silicone oil, long range order is lost at ~ 400 MPa. First principles calculations of phonons for CaZrF 6 suggest a subtly
different mechanism for the NTE in CaZrF6 when compared to that for ScF3.
In contrast to CaZrF6, CoZrF6 undergoes a cubic-to-rhombohedral phase transitions near room temperature and display
much weaker negative thermal expansion in the cubic phase (linear CTE -3 ppm·K-1 at 400 K). An understanding of the
factors influencing the thermal expansion within this structure type may allow for the development of controlled, including
zero, thermal expansion materials.
INOR 530
Dark reactions project: a machine learning approach to materials discovery
Alex J. Norquist, [email protected]. Haverford College, Bryn Mawr,
Pennsylvania, United States
Organically templated metal oxides have been the focus of intense interest for several decades owing to a host of
technologically intriguing properties that they can exhibit. Most of these are produced through exploratory reactions.
Unfortunately, most of these reactions are deemed ‘unsuccessful’ in that they do not result in the formation of a new
unique phase. Such reactions are never reported in the literature, and there is no forum for collecting them, nor a means
to fully extract chemical information from them. Nevertheless, these "dark reactions" are valuable because they define the
bounds on the reaction conditions needed to successfully synthesize a product. A searchable online repository for
reaction data has been created that enables better management, sharing, and utilization of these dark reactions. Progress
in using the "dark reaction" dataset to accelerate exploratory synthesis by using machine learning will also be discussed.
Using this dataset, standard cheminformatics techniques are used to compute derived properties, and then trained a
decision-tree algorithm to predict the success of new reactions. Preliminary results in experimentally validating these
predictions will be presented.
INOR 531
Ferromagnetic behavior in non-metal anionic element reagent complexes
Michael P. Rowe1, [email protected], Ryan Desautels 2,1, Elizabeth Skoropata3,1, Johan van Lierop4. (1)
Toyota Research Institute of North America, Ann
Arbor, Michigan, United States (2) University of Manitoba, Winnipeg, Manitoba, Canada
We are all familiar with the notion of ferromagnetic metal-based systems. Equally known, but far less common, is that of
non-metals exhibiting ferromagnetic behavior. The mechanochemical reaction of either carbon or boron with LiBH4 has
been found to make just such unique materials. Referred to as anionic element reagent complexes (AERCs), XPS
analysis of the C(LiBH4)2 (C-AERC) and B(LiBH4)2 (B-AERC) complexes show remarkable -0.8 and -1.8 eV reduction
shifts in the 1s binding energies versus the elemental carbon and boron, respectively. Zero-field-cooled (ZFC)/fieldcooled
(FC) DC susceptibility measurements showed a strong irreversibility that persisted up to ~300 K. The ferromagnetic
behavior was indicated also by hysteresis loop measurements. For example, in figure 1b the temperature dependence of
the coercivity is shown for C-AERC, clearly ferromagnetic behavior up to 300 K. The mechanochemical combination of
these diamagnetic materials (carbon or boron and LiBH4) is a new path to a unique family of ferromagnetic
materials.Figure 1. a) zerofield-cooled (ZFC)/field-cooled (FC) DC susceptibility curves which demonstrate the
ferromagnetic behavior for C(LiBH4)2. b) Temperature dependence of the coercivity (Hc) for C(LiBH4)2.
INOR 532
Novel CeO2 yolk-shell structures loaded with tiny Au nanoparticles for highly catalytic reduction of p-nitrophenol
Cong-Min Fan, [email protected], An-Wu Xu. Division of Nanomaterials and
Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, , University of
Science and Technology of China, Hefei, , Anhui, , China
Direct fabrication of core-shell or yolk-shell functional nanomaterials via a facile template-free method remains a
challenge. In this work, we present a novel approach that involves straightforward chemical transformation and thermal
treatment of the infinite coordination polymer particles to obtain composition-tunable CeO2 yolk-shell structures. Uniform
CeO2 yolk-shell hollow spheres with a high surface area are promising support materials for tiny gold nanoparticles (ca. 4
nm), forming Au-CeO2 nanocomposites which exhibit a remarkable catalytic activity and high stability for the reduction of
p-nitrophenol. A possible mechanism for the formation of CeO 2 yolk-shell microspheres is also proposed.
INOR 533
Diphenyl ether based secondary phosphine oxide as preligand for nickelcatalyzed carbon-sulfur cross-coupling
reactions
Nadeesha P. Nambukara Wellala2, [email protected], Hairong Guan1. (1) Univ of
Cinn, Cincinnati, Ohio, United States (2) Chemistry, University of Cincinnati, Cincinnati, Ohio, United States
Transition-metal catalyzed carbon-sulfur cross-coupling reactions have received great attention among the organic
community due to their importance in the synthesis of pharmaceutically active compounds that contain an aryl sulfide
moiety. Air and moisture stable secondary phosphine oxides could be attractive preligands for transition-metalcatalyzed
carbon-sulfur cross-coupling reactions. Although secondary phosphine oxides exist predominantly as the pentavalent form
for the phosphorus center, they can tautomerize to the less stable trivalent phosphinous acid. The phosphinous acid
formed exhibits good coordinating capability toward transition metals. Compared to the wellknown monodentate
secondary phosphine oxides, bidentate secondary phosphine oxides are less explored but potentially more superior in
stabilizing active catalytic species. A novel bidentate secondary phosphine oxide was therefore synthesized from the
reaction between organolithium compounds and Cl(NEt2)PPh followed by hydrolysis in acidic media. This compound was
fully characterized and its ligated nickel complex was demonstrated to catalyze the thiolation of iodobenzene. Optimized
catalytic reaction conditions are 0.5 mol% of catalyst, 1.1 equiv. of KOH in DMF at 80 oC for 1 h. Investigation of substrate
scope is in progress.
INOR 534
Dehydration and dehydrogenation of ethanol over Au-exchanged ZSM-5 zeolite: A DFT study
Thana Maihom1,4, [email protected], Bundet Boekfa1,4, Jumras Limtrakul2,3, [email protected]. (1) Department of
Chemistry, Faculty of Liberal Arts and Science, Kasetsart University Kamphaeng Sean Campus, Nakhon Pathom, Nakhon
Pathom
73140, Thailand (2) Department of Chemistry and NANOTEC Center for Nanoscale
Materials Design for Green Nanotechnology, Kasetsart University, Bangkok, Bangkok
10900, Thailand (3) PTT Group Frontier Research Center, 555 Vibhavadi Rangsit Road,
PTT Public Company Limited, Bangkok, Chatuchak, Bangkok 10900, Thailand (4) Center for Advanced Studies in
Nanotechnology and Its Applications in Chemical, Food and Agricultural Industries, Kasetsart University, Bangkok,
Chatuchak, Bangkok 10900,
Thailand
The conversion of bio-ethanol, which is derived from energy crops, to sufficient chemicals has received considerable
important attention for the development of clean technology for the chemical industry. We investigated the reaction
mechanisms of the ethanol dehydration and dehydrogenation to ethene and acetaldehyde over Au exchanged ZSM-5
zeolite by using an efficient density functional, M06-L. In the dehydration pathway, the reaction is proposed to proceed in
three steps. It initiates from the ethanol O-H bond dissociation leading to form the ethoxide-hydroxide intermediate which
is followed by the hydrogen transfer from intermediate methyl to the hydroxide group producing the water molecule and
ethoxide with a carbonium ion intermediate. This intermediate is finally decomposed to an ethene product. The second
step is found to be a rate determining step with the activation energy of 23.1 kcal/mol. For the acetaldehyde pathway, the
reaction proceeds via two steps of the ethanol O-H bond dissociation to form an ethoxide intermediate and the
intermediate transformation to acetaldehyde. The rate determining step activation barrier of this pathway is 9.0 kcal/mol
which is significantly lower than the dehydration pathway. The results suggest that the ethanol dehydrogenation to
acetaldehyde is favored over the ethanol dehydration to ethene on Au-ZSM-5 zeolite.
INOR 535
Tuning the reactivity of molecular water oxidation catalysts
David W. Shaffer, [email protected], Javier J. Concepcion. Chemistry, Brookhaven
National Laboratory, East Setauket, New York, United States
[(bda)Ru(L)2], a ruthenium center supported by a planar tetradentate, bipyridyldicarboxylate (bda 2−) ligand and neutral
pyridine-based donors (L) is among the best water oxidation catalysts in the literature. The current study aims to
understand the factors controlling the efficacy of these catalysts by introducing substituents of varying electron–
withdrawing and –donating character into the bda2− backbone. Voltammetric experiments reveal increased oxidizing
power for complexes with electron-withdrawing substituents. These electron-poor catalysts are also faster than the
unsubstituted complex, as evidenced by stopped flow UV-vis absorption measurements with cerium(IV) as an oxidant.
Analysis of the kinetic data suggests that the relative electron density at the metal center affects the mechanistic pathway
for water oxidation. Furthermore, modification of positions coplanar with the complex’s binding site have a more
pronounced effect on reactivity than modification of the axial ligands. The complexes studied herein represent some of the
fastest molecular water oxidation catalysts reported and have potential applications in dye-sensitized
photoelectrochemical cells or other energy-storing devices.
INOR 536
Mesoporous Co3O4 catalyst for CO oxidation at -60C: Controlled porosity, reaction mechanism, and deactivation
reason
Wenqiao Song2, [email protected], Altug Poyraz2, Yongtao Meng2, Zheng
Ren2, Sheng-Yu Chen1. (1) Univ Connecticut, Storrs, Connecticut, United States (2) University of Connecticut, Storrs,
Connecticut, United States
Crystalline mesoporous cobalt oxides with improved catalytic activity in CO oxidation were synthesized using an inverse
surfactant micelle method. The prepared materials are monodispersed nanoparticle aggregates and the mesopores are
formed by interconnected intraparticle voids. The effect of heat treatment from 150 to 450ºC on structural parameters and
catalytic activity towards CO oxidation is discussed in detail. Powder X-ray diffraction (PXRD), N2 sorption, field emission
scanning electron microscope (FE-SEM) together with high-resolution transmission electron microscopy (HR-TEM)
revealed that both pore and nanoparticle sizes are enlarged with increasing thermal treatment temperature. Among these
catalysts, Mesoporous cobalt oxide calcined at 350ºC exhibited the best activity. Which can completely oxidize carbon
monoxide to carbon dioxide at -60ºC under normal condition (~ 3ppm H2O) and at 80 ºC under moisture rich condition (~
3ppm H2O). While the commercial Co3O4 reached 100% conversion at 220ºC under normal condition. X-ray photoelectron
spectroscopy (XPS), O2-temperature programmed desorption (O2-TPD), H2-temperature programmed reduction (H2-TPR),
CO-TPD and N2 sorption analyses indicated that the surface oxygen vacancy as well as large surface area promoted the
lattice oxygen mobility of the catalysts and contributed to their enhanced catalytic activities. The catalysts were
deactivated by accumulation of water and formation of carbonates but their activities can be easily restored by heating
under helium at moderate temperature (200ºC).
Song, W.; Poyraz, A. S.; Meng, Y.; Ren, Z.; Chen, S.-Y.; Suib, S. L.Chem. Mater., 2014, 26 (15), pp 4629–4639
INOR 537
Dinitrogen silylation facilitated by a dicobalt catalyst
Randall B. Siedschlag, [email protected], Konstantinos D. Vogiatzis, Varinia
Bernales, Nora Planas, Laura Gagliardi, Connie C. Lu. Department of Chemistry, University of Minnesota, Minneapolis,
Minnesota, United States
We examine the silylation of dinitrogen to tris(trimethylsilylamine) using a dicobalt catalyst. In regard to the challenging 6electron reduction of N2 to (TMS)3N, only monometalic molybdenum [turnover number (TON): 150] and to a lesser extent
iron (TON: 34) and chromium (TON: 5.4) complexes have proven catalytically competent. Notably, bimetallic complexes
featuring metal-metal bonds have not been previously
shown to facilitate this reaction. The synthesis and characterization of the aforementioned dicobalt system and its catalytic
activity toward dinitrogen silyation will be discussed.
INOR 538
Cyclic alkyl amino carbene (CAAC) ruthenium complexes as remarkably active catalysts for ethenolysis
Vanessa M. Marx1, [email protected], Alexandra H. Sullivan1, Mohand-Ameziane
Melaimi2, Scott C. Virgil3, Guy Bertrand2, Robert H. Grubbs1. (1) Chemistry and Chemical Engineering, California Institute
of Technology, Pasadena, California, United
States (2) Chemistry and Biochemistry, University of California, San Diego, San Diego,
California, United States (3) Center for Catalysis and Chemical Synthesis, California
Institute of Technology, Pasadena, California, United States
An expanded family of ruthenium metathesis catalysis bearing cyclic alkyl amino carbene (CAAC) ligands is reported.
These catalysts exhibited exceptional activity in the ethenolysis of the seed oil derivative methyl oleate. In many cases,
TONs >100,000 were achieved, at only 3 ppm catalyst loading. Remarkably, the most active catalyst system was able to
achieve a TON of 330,000, at only 1 ppm catalyst loading. This is the first time a series of metathesis catalysts has
exhibited such high performance in cross metathesis reactions employing ethylene gas, with activities sufficient to render
ethenolysis a truly sustainable process for the industrial scale production of linear alphaolefins (LAOs) and other terminal
olefin products.
INOR 539
Iron porphyrin carbenes as catalytic intermediates: Structures, Mössbauer and NMR spectroscopic properties,
and bonding
Rahul Khade, Yong Zhang, [email protected]. Chemistry, Chemical
BiologyBiomedical Eng., Stevens Institute of Technology, Hoboken, New Jersey, United
States
Iron porphyrin carbenes (IPCs) are thought to be intermediates involved in the metabolism of various xenobiotics by
cytochrome P450, as well as in chemical reactions catalyzed by metalloporphyrins and engineered P450s. While early
work proposed IPCs to contain FeII, more recent work invokes a double bond description of the iron carbon bond, similar
to that found in FeIV porphyrin oxenes. Here, we report the first quantum chemical investigation of IPC Mössbauer and
NMR spectroscopic properties, as well as their electronic structures, together with comparisons to ferrous heme proteins
and an FeIV oxene model. The results provide the first accurate predictions of the experimental spectroscopic observables
as well as the first theoretical explanation of their
electrophilic nature, as deduced from experiment. The preferred resonance structure is Fe II<-{:C(X)Y}0 and not
FeIV={C(X)Y}2-, a result that will facilitate research on IPC reactivities in various chemical and biochemical systems.
INOR 540
Electrochemical studies of cobalt (II) N2Py2 complexes and a nickel (II) bis(diphosphine) complex toward catalytic
proton reduction
Juliet F. Khosrowabadi Kotyk, [email protected], Jenny Yang. Chemistry, University of California, Irvine, Irvine,
California, United States
Divalent cobalt complexes of tetradentate N2Py2 incorporating a pendant base moiety in the second coordination sphere
have been synthesized and studied electrochemically for catalytic activity towards H+ and O2 reduction. Progress toward
proton reduction has been studied using H 2O, [PhNH3][BF4], and [HDMF][OTf] in organic solvents. A divalent nickel
complex of DHMPB (1,2-Bis(dihydroxy dimethylphosphino)benzene) has been synthesized and tested as an
electrocatalyst for proton reduction using [HTMG][BF4] and [PhNH3][BF4] in organic solvents.
INOR 541
Development of advanced polymers for hydraulic fracturing applications
Casie R. Hilliard, [email protected], Cesar Meza, Robert Schlemmer, James
Donovan. Dow Oil, Gas, and Mining, The Dow Chemical Company, Freeport, Texas,
United States
Over the last decade, hydraulic fracturing has gained momentum in the U.S., and advances in the application of fracturing
techniques have led to a resurgence of domestic energy production primarily from shale. As of 2013, estimates put the
total undeveloped technically recoverable resource (TRR) of shale oil and gas, including coalbed methane, remaining in
discovered shale plays in the U.S. at 741.8 tcf of natural gas and 23.8 billion barrels of oil (BBO).1 Given the growing
relevance of this application, gaining a better understanding of the chemical components of the fluids can help in
evaluating their use and impact. The primary ingredients for any hydraulic fracturing formulation are water and sand,
usually accounting for more than 99 wt%. To provide an effective aqueous medium for suspension and transportation of
the proppants downhole, water is typically thickened using a rheology modifier or gelling agent. Various classes of
polymers, including biopolymers (polysaccharides) and purely synthetic polymers, have served as rheology modifiers in
hydraulic fracturing fluids. Polymers must impart excellent rheological performance and suspension capabilities by forming
strong gel structures while still maintaining pseudoplastic behavior to eliminate energy losses when pumping the viscous
material.
The most commonly used polymer in the hydraulic fracturing industry today is guar gum. Although guar-based fluids are
able to provide the desired rheological properties for certain applications, they can suffer from fluid instability and can
cause irreparable formation damage. Emphasis in the industry has shifted towards focusing on new alternatives to guar,
especially for high temperature applications, in which the mannose backbone of guar is chemically unstable leading to a
significant loss in performance. New associative synthetic polymers have proved especially promising in lab testing and
will be given special attention. This seminar will provide a general overview of the function, evaluation, and rheological
requirements of polymers in hydraulic fracturing fluids as well as their desired temperature stability and salt tolerance
properties. Investigating the rheology of synthetic polymers in formulated hydraulic fracturing fluids and at elevated
temperatures (150-200°C) has proven their advantage over traditional biopolymers, as highlighted in this presentation.
1. Nangmenyi, G., “The U.S. market for fracking fluids”, BCC research, EGY121A, Feb 2014.
INOR 542
Shale gas and oil flowback and produced water modeling and treatment
Mason B. Tomson1, [email protected], Zhang Zhang1, Zhaoyi Dai1, Valerie Bolanos1,
Amy T. Kan1, Fei Yan1, Ross Tomson2. (1) Civil and Environmental Engineering, Rice
University, Houston , Texas, United States (2) Brine Chemistry Solutions, Houston, Texas, United States
The production of very high TDS produced waters and how to treat them for reuse is one of the major problems
associated with shale gas and oil production. As the flowback water is produced in the first few days, the TDS typically
increases to some peak value (often 100 to 200 k-mg/L TDS) and then levels off as the flowback water ends and the
lower rate of produced water commences. These flowback and produced waters are challenging to the operator. It would
be desirable to reuse 100% of these waters, but the presence of frac additives, friction reducers, the higher TDS, and
specific composition often prevents the water from being reused. In addition, there are significant challenges related to the
produced water composition, mineral scale formation, hydrogen sulfide, microbial contamination, and corrosion, to
mention a few. Testing and modeling of these complex produced water systems has been a focus of our research with
emphasis on modeling the unusually high TDS/compositions and special requirements of strictly anoxic (<< 1 ppb O 2)
scale and corrosion testing regimes. It has been found that most models of solution chemistry at high temperature,
pressure and compositions are inadequate and new measurements and modeling results have been developed that better
match field conditions. Finally, results will be presented that support the importance of strictly anoxic testing for scale and
corrosion inhibitor evaluation.
INOR 543
Dynamic microbial communities in hydraulic fracturing water: Implications for vhemistry and water management
Kelvin B. Gregory, [email protected]. Civil Environmental Engineering, Carnegie Mellon University, Pittsburgh,
Pennsylvania, United States
Recycling of produced water for subsequent hydraulic fracturing has emerged as an essential technology for economic
development of unconventional oil and gas resources. As a result, impoundments for storage of produced water are larger
and retention times longer. During impoundment, microbial communities evolve that produce malodorous compounds and
alter the fate of metals. Standard industry practices for management of produced water include aeration and biocide
amendment, both costly. The presentation will provide a brief introduction to produced water management and discuss
the how bacterial communities change from the make-up water through stimulation and production. The impact of water
management strategies on microbial communities and geochemistry will be discussed in the context of recycling of
produced water, emergent strategies for more sustainable hydraulic fracturing, and opportunities for novel chemistry in
treatment and microbial control.
INOR 544
Characterizing oil and gas exploration and production waste streams: Collaborative inter-laboratory comparison
Tzahi Y. Cath, [email protected]. CEE, Colorado School of Mines, Golden, Colorado,
United States
As the oil and gas industry expands in the United States, managing the high volumes of waste streams generated during
development and production becomes increasingly important when considering the preservation of ecosystems and
protection human health. Accurate characterization and quantification of constituents in oil and gas wastewater is
essential to ensure adequate treatment, discharge of reclaimed water, and disposal and residuals from the treatment
processes. The main objective of this study was to explore the methods used to analyze produced water and fracturing
flowback wastewater and to evaluate the differences in analytical results. This goal was carried out through an interlaboratory comparison of four oil and gas development and production wastewaters, including raw fracturing flowback,
treated fracturing flowback, raw produced water, and treated produced water, all obtained from the DenverJulesburg basin
in Colorado. The methods used to characterize these water samples were EPA Method 300.0, EPA Method 200.7, EPA
Method 200.8, SW 846 Method 6010C, and SW 846 Method 8015B.
Even with the consistent use of EPA testing methods across commercial laboratories, different EPA methods are often
used to characterize the same analytes. As an example, when analyzing for total recoverable cations, several EPA
approved methods can be chosen. Method choices range from those associated with the Clean Water Act (such as EPA
Method 200.7 and 200.8), to methods applied to solid wastes and wastewaters, such as the Solid Waste (SW 846)
Method series. Furthermore, different sample preparation methods may be used (such as SW 846 3010 and EPA 3052)
by the same laboratory, depending on the client’s request. In addition to the variability of methods used, methods are
often altered, as many are not able to handle the unique make-up of produced and flowback water.
The mean, standard deviation, and relative standard deviation of the results from this inter-laboratory comparison were
compared to the mean, standard deviation, and relative standard deviation found in each of the EPA methods validation
data. This comparison elucidated the variation resulting from the application of the EPA methods to the oil and gas
development and production wastewater matrices.
INOR 545
In vitro selection and characterization of metallo-DNAzymes and their delivery into cells for sensing and imaging
applications
Yi Lu1,3, [email protected], Kevin Hwang2, Peiwen Wu3, Seyed-Fakhreddin Torabi3. (1) Dept of Chemistry, Univ of Illinois,
Urbana, Illinois, United States (2) Department of
Chemistry, University of Illinois at Urbana-Champaign, Champaign, Illinois, United
States (3) Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois,
United States
One of the most important discoveries in the 20th century is that DNA and RNA are not only materials for genetic
information storage and transfer, but also enzymes for a variety of biological reactions. Since metal ions play essential
roles in the structure and function of catalytic DNA/RNA, the study and application of these new metalloenzymes has
become a new frontier in bioinorganic chemistry. While different classes of metalspecific proteins have been studied,
including a comprehensive understanding of their sequence, structural, and functional features specific to each metal
ions, similar information about metal-specific DNA/RNA is not available. Using in vitro selection methods, we have been
able to obtain new DNAzymes from a large DNA library of up to 10 15 different sequences that are specific to a metal ion of
choice, with high specificity.1 We have also carried out both biochemical and biophysical studies of these DNAzymes in
order to elucidate features responsible for the selective binding of metal ions by the DNAzymes. 2 Because of the high
selectivity, these DNAzymes have been converted into fluorescent, colorimetric, electrochemical sensors and magnetic
resonance imaging agents for detection of metal ions with high sensitivity (down to 11 ppt limit of detection) and selectivity
(up to millions of fold of selectivity).3 Recently, these DNAzymes have been delivered into cells through conjugation with
gold nanoparticles4 or cationic peptides.5 Together with photo-caged DNAzymes,5 these methods allow detection and
imaging of a wide variety of metal ions in living cells with high spatial and temporal resolution.
1. a) J. Liu et al., Proc. Natl. Acad. Sci. USA 104, 2056–2061 (2007); b) Y. Xiang and Y. Lu Inorg. Chem. 53, 1925–1942
(2014).
2. a) H.-K. Kim et al. Nature Chem. Biol. 3, 763-768 (2007); b) T. Lan and Y. Lu, in Interplay between Metal Ions and Nucleic
Acids", Metal Ions in Life Sciences, Vol. 10, A.
Sigel, H. Sigel, R. K. O. Sigel, eds.; Springer Netherlands; pp. 217-248 (2012).
3. J. Liu, Z. Cao, Y. Lu, Chem. Rev. 109, 1948–1998 (2009).
4. P. Wu, et al. J. Am. Chem. Soc. 135, 5254-5257 (2013)
5. K. Hwang, Angew. Chem. Inter. Ed. (in press: DOI: 10.1002/anie.201408333)
INOR 546
Is the geometry of Vanadium in active site of phosphatases important for inhibitor design and antidiabetic
properties of vanadium compounds
Debbie C. Crans1, [email protected], Benjamin J. Peters 1, M. L. Tarlton2,
Gail R. Willsky3, Craig C. McLauchlan2. (1) Chemistry, Colorado State University, Fort
Collins, Colorado, United States (2) Dept of Chemistry, Illinois State Univ, Normal,
Illinois, United States (3) Biochemistry,School of Medicine and Biomedical Sciences,
University at Buffalo (State University of New York, SUNY), Buffalo, New York, United
States
Vanadate, and vanadium compounds are insulin enhancing agents and representative compounds have been tested in
animal systems and human beings.1-3 The specific mode of action and the active species have remained elusive such
studies being complicated by the complex speciation. One mode of action of these compounds is believed to be inhibition
of phosphatases.1-3 In the following presentation we will investigate the structural aspects of oxovanadate and vanadium
complexes coordinated to phosphatases. Specifically, we examine the active sites of the 29 known X-ray structures and
analyze the coordination chemistry of the vanadium atoms in the active site and characterize them with regard to trigonal
bipyramidal or square pyramidal character. We also compare these systems with small molecule vanadium complexes to
determine if the forms in the protein complex is similar to the small molecules characterized.4 These considerations
demonstrate that a trigonal bipyramidal geometry is observed in the vanadium-phosphatase complexes even though the
square pyramidal geometry is more stable for the complexes themselves. These observations were compared to the
biochemical data available measuring Ki values for oxovanadates as well as other oxometalates and finally for vanadium
compounds. Together all these data are used to provide direction with regard to inhibitor design.
References
1. K.H. Thompson, J. Lichter, C. LeBel, M.C. Scaife, J.H. McNeill, C. Orvig, J. Inorg. Biochem. 2009, 103, 554-558.
2. B. I Posner; R. Faure; J.W. Burgess; A. P. Bevan; D. Lachance; G. Zhang-Sun; I. G. Fantus; J. B. Ng; D. A. Hall; B. S.
Lum J. Biol. Chem. 1994, 269, 4596-4604.
3. G.R. Willsky, L.-H. Chi, M. Godzala, III, P.J. Kostyniak, J.J. Smee, A.M. Trujillo, J.A. Alfano, W. Ding, Z. Hu, D.C. Crans,
4.
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Coord. Chem. Rev. 2011, 255, 2258-2269.
D.C. Crans, M.L. Tarlton, C.C. McLauchlan, Eur. J. Inorg. Chem., In press (2014).
Crans, D.C.; Keramidas, A.D.; Drouza,C. Phosphorus, Sulphur, and Silicon 1996, 109-110, 245-248.
McLauchlan, C.C.; Hooker, J.D.; Jones, M.A.; Dymon, Z.; Backhus, E.A.; Greiner, B.A.; Dorner, N.A.; Youkhana, M.A.;
Manus, L.M. J. Inorg. Biochem. 2010, 104, 274281.
7. Lu, L.; Yue, J.; Yuan, C.; Zhu, M.; Han, H.; Liu, Z.; Guo, M. J. Inorg. Biochem. 2011, 105, 1323-1328.
8. Lu, L.; Gao, X.; Zhu, M.; Wang, S.; Wu, Q.; Xing, S.; Fu, X.; Liu, Z.; Guo, M. BioMetals 2012, 25 (3), 599-610.
INOR 547
Metal ion incorporation in peptide nucleic acid triplexes
Catalina Achim, [email protected], Dilhara Jayarathna, Yookyung Bae, Heather
Stout. Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Substitution of nucleobases within duplexes of natural or synthetic nucleic acids with ligands has been used in the last
decade and a half as a method for the precise positioning of transition metal ions in the duplexes. The metal ion
incorporation can greatly expand the properties of the duplexes or higher order structures to include electronic, magnetic
and catalytic properties different from those of organic molecules and materials. While metal incorporation in duplexes
was the focus of many published studies, their incorporation in triplexes was not. As a larger variety of coordination
environments can be created by ligand incorporation in triplexes, we have examined the coordination ability of bis- and
tris-ligand sites created in triplexes upon hybridization of ligand-containing, homo-purine and –pyrimidine peptide nucleic
acid (PNA) strands. The quantitative evaluation of the factors that govern the incorporation of metal ions at specific
locations in the PNA triplexes shows that the supramolecular chelate effect exerted by nucleic acid hybridization on metal
coordination to ligands built in the nucleic acid is modulated by steric interactions between the metal-ligand complex and
the triplex. These findings are of value in the design of functional hybrid inorganic-nucleic acid architectures.
INOR 548
Development of redox-active ruthenium polypyridyl complexes as an anticancer agents for the treatment of
platinum resistant tumors
Frederick M. MacDonnell2, [email protected], Nagham Alatrash2, Eugenia Narh2,
Cynthia Griffith1. (1) Chemistry and Biochemistry Dept, University of Texas at Arlington,
Arlington, Texas, United States (2) Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas, United
States
The use of transition-metal complexes in oncology has enjoyed extensive attention given the tremendous success of
platinum-based chemotherapeutics. Unfortunately, their efficacy in many cancers is limited by the development of
resistance. We recently reported that ruthenium complexes, [(phen) 2Ru(tatpp)]Cl2 (RPC3) and ,
[(phen)2Ru(tatpp)Ru(phen)2]Cl4 (RPC4) exhibit low acute animal toxicity, hypoxia potentiated cytotoxicity , and 83% tumor
regression in non-small cell lung cancinoma (H358) human tumor xenografts. These RPCs cleave DNA under normoxic
and hypoxic conditions, however the extent of DNA cleavage is inversely proportional to the pO 2, suggesting enhanced
activity against cells under hypoxic stress. In screening these RPCs against a number of normal and platinum resistant
cell lines, we discovered that RPC4, in particular, showed good cytotoxicity against the platinum resistance lines. For
example, the IC50’s for RPC3, RPC 4, and cisplatin in human cervical cancer cells
(Hela) and platinum resistant Hela/CP are 15.1, 16.1, 7.0 and 34.0, 1.9, and 30.0 μM, respectively. RPC4 also showed an
IC50 of 8.4 µM against platinum resistant human squalmous lung cancer (HCC2450). This paper will present our current
understanding on the DNA cleavage mechanism and our findings on the cellular distribution. The normal vs malignant
cytotoxicity and animal toxicity the these RPCs, and a number of closely related homoleptic and heteroleptic ruthenium(II)
tris(diimines) will be compared and contrasted.
INOR 549
Cobalt Schiff base complexes as targeted inhibitors of transcription factors
Marie C. Heffern, Thomas J. Meade, [email protected]. Chemistry, Molecular
Biosciences, Neurobiology, Biomedical Engineering and Radiology, Northwestern University, Evanston, Illinois, United
States
Transcription factors (TFs) are key mediators of cancer signaling and disease progression. Snail family TFs are involved
in the onset of metastasis, a process responsible for the vast majority of cancer-associated fatalities. Gli family TFs
represent the final step in the hedgehog (Hh) pathway. Overactivation of the Hh pathway is associated with growth and
proliferation of a variety of tumors including basal cell carcinoma, medulloblastoma, and pancreatic cancer. Therefore,
inhibitors of these TFs are powerful research tools for cancer biology and have potential use as the chemotherapeutic
agents. We are developing cobalt(III) Schiff base complexes (Co(III)DNA) that inhibit TFs by a unique mechanism. The
complexes are targeted to specific proteins through decoy oligonucleotides mimicking the native binding partner of the
protein of interest. Coordination of the Co(III) complex to histidines in the protein disrupts structure, leading to irreversible
inhibition of transcriptional activity.
We have demonstrated selective inhibition of Snail and Gli TFs by Co(III)-DNA in nonmammalian embryo models of
development. Snail-targeted Co(III)-DNA block the known functions of the TF in the formation and migration of neural
crest cells in Xenopus embryos, while the Snail-independent pathways remain unaffected. In a similar fashion, Glitargeted Co(III)-DNA inhibited Hh-associated denticle belt formation in Drosophila embryos selectively at the site where
agent was injected. The mechanism of TF inhibition by the Co(III)-DNA was investigated spectroscopically with model
peptides of zinc finger motifs (the structures responsible for the DNA-binding activity of Snail and Gli TFs). The
mechanism we describe focuses on Co(III) Schiff base complexes that inhibit protein activity through selective histidine
coordination in the zinc fingers via dissociative ligand exchange. Histidine-coordination disrupts the ββα structural motif
required for gene regulation. We are investigating this versatile Co(III)DNA platform in mammalian systems to inhibit
Snail- and Gli-associated pathways in cancer.
INOR 550
Inhibition of cysteine proteases with ruthenium-caged compounds
Jeremy J. Kodanko, [email protected]. Wayne State University, Detroit, Michigan, United States
Cysteine proteases play an important role in many human disease states, including cancer, inflammation, osteoporosis
and heart disease. For this reason, inhibitors of cysteine proteases have undergone extensive development as potential
therapeutics. We recently developed a caging approach towards cysteine protease inhibitors that gives spatial and
temporal control over enzyme activity. Nitrile-based inhibitors are stable when bound to ruthenium complexes, then
released from the metal center using light. This method provides high levels of turn on for cysteine protease inhibition in
2D and 3D in vitro cell-based assays. Light-activated inhibitors of the cysteine cathepsins B and K are reported that
function as chemical tools and serve as the basis for developing highly specific, light-activated therapeutics.
INOR 551
Strategies for the photochemical uncaging of bioactive small molecules
Peter C. Ford, [email protected], John V. Garcia, Agustin Pierri, Meredith Crisalli,
Anthony W. DeMartino, Po-Ju Huang. University of California, Santa Barbara, California, United States
Photochemical strategies allow one to control location, timing, and dosage for the delivery of bioactive agents to
physiological targets. In this context, we have explored the photoreactions of various metal complexes that are precursors
for the targeted release of the small molecule bioregulators nitric oxide and carbon monoxide as well as of a potentially
therapeutic molecule, carbon disulfide. Since such precursors often display poor absorbances at longer visible
wavelengths, we have turned our attention to developing various mini-, micro- and nano-carriers that combine the
photochemical precursors with various types of antennas designed to utilize tissue penetrating red or near infrared light as
the excitation source. Of particular interest are quantum dots and NIR-to-visible upconverting nanoparticles that can serve
as multi-photon antennae for light absorption and subsequent photo-sensitization.
INOR 552
Lewis acidic properties of organoantimony compounds: From bidentate
distiboranes to perfluorinated stibonium cations
Francois P. Gabbai, [email protected]. Dept of Chem, Texas AM Univ, College Station, Texas, United States
After a review of the intrinsic Lewis acidic properties of simple organoantimony compounds, we will show that the Lewis
acidic properties of such compounds can be enhanced by both cooperative and electronic effects. The occurrence of
cooperative effects will be showcased in a series of bidentate distiboranes which form fluoride complexes with remarkably
stable Sb-F-Sb chelate motifs. The use of electronic effects will be illustrated by a discussion of the synthesis and
chemistry of the stibonium cation
[Sb(C6F5)4]+. This cation is a potent Lewis acid which abstracts a fluoride anion from
[SbF6]- and [BF(C6F5)3]- indicating that it is a stronger Lewis acid than SbF5 and B(C6F5)3. This cation is also a powerful
hydride abstracting agent which converts main group hydrides such as Et 3SiH into the corresponding cations.
INOR 553
Platinum diimine dithiolate chromophores and dyads for the light-driven generation of hydrogen
Richard Eisenberg, [email protected]. Dept of Chem, Univ of
Rochester, Rochester, New York, United States
Four-coordinate Pt complexes that contain a diimine ligand such as bipyridine and an unsaturated dithiolene ligand have
been known for more than 50 years. These complexes exhibit strong negative solvatochromism characteristic of a polar
ground state with a much less polar excited state. The complexes are solution luminescent and undergo electron transfer
quenching from an excited state that has been characterized as a mixed-metal-ligand-to-ligand' charge transfer
(MMLL'CT). When attached to TiO2
via the diimine ligand, these Pt complexes can yield photocurrent upon irradiation. The
ability of these complexes to transfer an electron to TiO2 has led to their use as photosensitizers for the generation of H 2
from water. However, because of their relatively modest light absorption, recent work has led to connecting the Pt diimine
dithiolate chromophore to organic dyes for enhanced visible light absorption and subsequent charge transfer. Recent
research using these systems for the light-driven generation of water will be discussed, as will excited state dynamics of
these systems.
INOR 554
Manipulation of the electronic structures of cerium complexes toward the development of a new class of
photosensitizers
Eric J. Schelter1, [email protected], Haolin Yin2, Patrick Carroll3. (1) Dept of Chemistry, University of
Pennslyvania, Philadelphia, Pennsylvania, United States (2)
Dept Chemistry Mb77, University of Pennsylvania, Philadelphia, Pennsylvania, United
States (3) Chemistry Department, University of Pennsylvania, Philadelphia, Pennsylvania, United States
The key chemical characteristic of cerium is its ability to cycle between trivalent and tetravalent redox states. This facile
redox chemistry is a unique attribute among the rare earths that is exploited broadly in materials- and synthetic chemistry.
In the coordination chemistry of cerium, work from our group has recently shown the sensitivity of the cerium(IV/III) redox
couple to the type of crystal field present at the cation. In the next phase of our work we have begun leveraging these
observations toward coupling cerium redox processes with external stimuli, namely light, based on the characteristic
electronic structure features of the element. Results on a new class of luminescent cerium complexes with quantum yields
up to ~50% and a related class of photosensitizers will be presented.
INOR 555
Control of excited states of transition metal complexes: Optimizing multiple excited state pathways
Claudia Turro2, [email protected], Kim R. Dunbar1. (1) Texas AM Univ,
College Station, Texas, United States (2) Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, United
States
Photoinduced ligand exchange, excited state charge transfer, photoisomerization, and sensitization of 1O2 production
represent important reactions initiated by light with potential applications that include photochemotherapy (PCT) and solar
energy conversion. Transition metal complexes possessing nitriles in the coordination sphere exhibit high quantum yield
of ligand exchange in coordinating solvents, such that irradiation of these complexes results in the formation of covalent
adducts between the metal and Lewis basic sites on biomolecules. These systems represent a new class of potential PCT
agents because their mode of action differs significantly from those currently in use, which rely on the production of
reactive oxygen species. The presentation will focus on new strategies to tune the electronic structure and steric bulk of
ligands to enhance photoinduced ligand dissociation. Ultrafast time-resolved studies will be presented which show the
unprecedented population of two reactive states in single molecules, such that two pathways useful for PCT can be
accessed simultaneously. In addition, these complexes are also able to deliver caged drugs when irradiated with visible
light. Strategies will be presented to improve the yields of the various excited state pathways possible in these multipleaction complexes. The application of these complexes to problems in solar energy conversion for the photocatalytic
production of H2 will be discussed.
INOR 556
Halogen photoelimination from Ni(III) complexes: An energy storing transformation
Seung Jun Hwang1, David C. Powers1, Shao-Liang Zheng1, Yu-Sheng Chen2, Daniel
G. Nocera1, [email protected]. (1) Department of Chemistry and Chemical Biology, Harvard University,
Cambridge, Massachusetts, United States (2) Center for
Advanced Radiation Sources, University of Chicago, Argonne, Illinois, United States
Nickel(III) halo-arylphosphine complexes have been designed for the efficient elimination of halogen upon photoexcitation,
both in solution and the solid state. Transient absorption spectroscopy identifies a pi-aromatic-halogen complex as the
critical photointermediate. Two other experiments support this contention: (1) the photoreaction quantum yield increases
monotonically with the amount of halogen radical character, as determined from EPR hyperfine couplings; and (2)
photocrystallography experiments show a significant lengthening of the Ni-axial halide bond upon irradiation. Calorimetric
measurements establish that the halogen photoreaction is uphill by as much as 25 kcal mol–1. The photochemistry, EPR,
transient absorption spectroscopy, calorimetry and photocrystallogrphy experiments for this energy storage reaction will
be presented.
INOR 557
How nickel/iron films catalyze the oxygen evolution reaction
Curtis P. Berlinguette, [email protected], Rodney D. Smith. CHEMISTRY, THE UNIVERSITY OF BRITISH
COLUMBIA, Vancouver, British Columbia, Canada
The electrochemical conversion of water into hydrogen fuel is a promising scheme for the large-scale storage of solar
electricity, but the efficiency of the process suffers from the substantial overpotential (η) required to produce hydrogen at a
meaningful rate. The development of efficient oxygen evolution reaction (OER) catalysts is therefore needed to improve
the multi-electron chemistry associated with converting water into hydrogen. While nickel has long been recognized to be
an excellent OER catalyst under alkaline conditions, recent findings by us and others have demonstrated that mixtures of
iron and nickel achieve state-of-the-art OER activities. There are, however, many open questions regarding how nickel
and nickel/iron films actually mediate the OER reaction. This presentation will challenge certain long-held notions
surrounding the electrochemistry of nickel oxy/oxyhydroxide films in order to provide clarity on this issue.
INOR 558
Inorganic chemistry, solution processed solar cells, and the era of perovskites
Mercouri G. Kanatzidis, [email protected]. Northwestern Univ,
Evanston, Illinois, United States
Organic-inorganic hybrid perovskites have gained considerable attention during the past two years and have
revolutionized the prospects of emerging photovoltaic technologies, in forms of both light harvesters and hole transport
materials. These organic-inorganic hybrid perovskite compounds adopt the ABX3 perovskite structure, which consists of a
network of corner-sharing BX6 octahedra, where the B atom is a divalent metal cation (typically Ge2+, Sn2+ or Pb2+) and X
is a monovalent anion (typically Cl−, Br−, I−); the A cation is selected to balance the total charge and it can be a Cs + or a
small molecular species. Such perovskites afford several important features including excellent optical properties that are
tunable by controlling the chemical compositions, ambipolar charge transport, and long electron and hole diffusion
lengths. Solar cells based on MeNH3PbI3 perovskites have gained enormous significance and reached a power
conversion efficiency close to 19%, approaching the efficiency of commercialized c-Si solar cells. Because of the toxicity
of Pb however the search is on for lead free alternatives. In this talk we report on the chemistry of tin-based perovskite
compounds their chemical and physical properties as well as phase transitions. We will present results on Pb-free solar
cell cells with good efficiency and stability. We will also present recent data on the design and fabrication of hybrid solar
cells: i) tin-based perovskites for the hole conducting layer while dye molecules is the sensitizer and ii) tin-based
perovskite as sensitizer and organic molecule as hole conductor.
INOR 559
Cyanide-bridged iron complexes as analogues of tri-iron arrangements in hydrogenase active site precursors
Allen M. Lunsford2, Christopher Beto3, Marcetta Y. Darensbourg1,
[email protected]. (2) Chemistry, Texas A&M University, College Station, Texas, United States (3)
Chemistry, University of Florida, Gainesville, Florida, United
States
Few ligands have impacted coordination chemistry to the extent of the soft but powerful diatomic anion, cyanide. The
unexpected discoveries of such toxic ligands as CO and CN - in the hydrogenase enzyme active sites, has fueled a subfield of bioorganometallic chemistry, and invigorated research into cyano-iron complexes that are mimetics of the active
sites. Recent reports have suggested that a cyanide bridge between the two-iron subsite of the [FeFe]Hydrogenase and
an iron-sulfur cluster, 4S4Fe-CN-[FeFe], is derived from a typical (µ-SRS)[Fe(CO)2CN]22- cluster.1 The linkage
isomerization thus displayed is related to observations in several studies from the Dunbar, Vahrenkamp, and Holm
groups.2-4 We report synthetic approaches to the assembly of triiron constructs using the (η5-C5H5)Fe(CO)2 as a mimic of
the iron-sulfur cluster. Appropriate order of reagent addition to suitably modified iron units yielded linkage isomers of the
form Fe-CN-[FeFe] and Fe-NC-[FeFe]. The structural, spectroscopic, reactivity and electrochemical properties of these
cyano-bridged tri-iron complexes confirm the preference for the (η5-C5H5)FeII(CO)2NC-FeIFeI arrangement while the
alternate linkage, (η5-C5H5)FeII(CO)2CN-FeoxFeox develops only for oxidized forms of the diiron unit, consistent with the
organometallic complexes reported by Vahrenkamp.3
References:
1) Berggren, G.; Adamska, A.; Lambertz, C.; Simmons, T. R.; Esselborn, J.; Atta, M.; Gambarelli, S.; Mouesca, J-M.;
Reijerse, E.; Lubitz, W.; Happe, T.; Artero, V.; Fontecave M. Nature. 2013, 499, 66-70.
2) Schelter, E. J.; Shatruk, M,; Heintz, R. A.; Gala´-Mascaro´s J. R.; Dunbar, K. R.
Chem. Commun. 2005, 11, 1417–1419. c) Shatruk, M.; Chambers, K. E.; Prosvirin, A. V.; Dunbar, K. R. Inorg. Chem.
2007, 46, 5155-5165. d) Shatruk, M.; DragulescuAndrasi,A.; Chambers, K. E.; Stoian, S. A.; Bominaar, E. L.; Achim,C.;
Dunbar, K. R. J. Am. Chem. Soc. 2007, 129, 6104-6116. e) Avendano, C.; Karadas, F.; Hilfiger, M.; Shatruk, M.; Dunbar,
K. R. Inorg. Chem. 2010, 49, 583–594.
3) Zhu, N.; Vahrenkamp, H. Chem. Ber. Recueil. 1997, 130, 1241 – 1252. 4) Lim, B. S.; Holm, R. H. Inorg. Chem. 1998, 37,
4898-4908.
INOR 560
Microfluidic separations for actinide processing and analysis
Rebecca M. Chamberlin1, [email protected], Stephen L. Yarbro2, Ning Xu1. (1)
Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United
States (2) National Security Education Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Los Alamos has initiated a broad, multi‐disciplinary program in microfluidic and microengineered plutonium separations.
Plutonium process capabilities can be maintained and advanced through microscale implementation in low‐hazard
facilities, then scaled up to high‐throughput systems when national needs require increased material production rates.
Analytical chemistry and bulk nuclear forensics have similar chemical separation needs, and microfluidic approaches can
enable significant sample size reduction and automated processing. Recent developments in both application areas will
be presented. The transferability of skills from synthetic organometallic chemistry to nuclear material separations and
analysis will also be discussed.
INOR 561
Production of Mo-99 for nuclear medicine
Aaron Anderson, Leo Bitteker, Michael Connors, Roy Copping, Matthew Cover, William
Crooks, Gregory Dale, Dale Dalmas, Michael Gallegos, Eduardo Garcia, Jack Gioia, Robert Gonzales, Debra Graves,
William K. Hollis, Michael Janicke, Charles Kelsey,
Iain May, Michal Mocko, Martin Pieck, Mohini Rawool-Sullivan, Sean D. Reilly, Daniel
Rios, Tobias Romero, Frances Stephens, Felicia Taw, [email protected], David Thorn, Keith Woloshun. Los Alamos
National Laboratory, Los Alamos, New Mexico, United
States
The daughter product of Mo-99, Tc-99m, is used in nuclear medicine to image nearly any organ in the body, including the
heart, lungs, kidneys, bone, and brain tissue. It is the most commonly used radioisotope, and is employed in over 20
million diagnostic procedures in the U.S. annually. Current supplies are predominantly derived from the irradiation of
highly enriched uranium targets in aging foreign nuclear reactors, which poses issues related to proliferation and
maintaining an uninterrupted and reliable inventory. Various efforts related to non-proliferant approaches to domestic Mo99 production will be discussed.
INOR 562
CO2 conversion using organometallic and organic molecular catalysts
Thibault Cantat, [email protected]. DSM / IRAMIS / NIMBE / LCMCE, CEA, Gif Sur Yvette, France
While greenhouse gases emissions are reaching alarming levels, fossil fuels still represent 80% of the world energy
portfolio and 95% of our chemical commodities rely on non-renewable resources, namely hydrocarbons. In this context,
utilizing CO2 as a C1 building block to produce platform chemicals as an alternative to petrochemistry has a double
advantage of reusing CO2 while sparing fossil resources and avoiding CO2 emissions from their use. We have developed
a strategy relying on the simultaneous use of a functionalizing reagent and a reductant that can be independently adjusted
to perform the reductive functionalization of CO2. The so-called diagonal approach will be discussed and exemplified with
novel catalytic processes to convert CO2 to formamides, N-heterocycles and methylamines, using hydroboranes,
hydrosilanes or formic acid as reductants. These new catalytic reactions rely on the use of simple organocatalysts or Zn,
Fe and Ru organometallic complexes. The mechanisms at play in these transformations will be presented, based on DFT
calculations and isolation of reactive catalytic intermediates.
INOR 563
Organometallic thorium azide complexes
Marisa J. Monreal, [email protected], Jaqueline L. Kiplinger, Brian Scott. Los
Alamos National Laboratory, Los Alamos, New Mexico, United States
Recently, we have been investigating the chemistry of organoactinide azide complexes. We have synthesized a family of
organometallic thorium azide complexes and have been exploring their reaction chemistry. Results from these reactivity
studies, in addition to the synthetic details and full characterization of all organometallic thorium azide complexes, will be
presented.
INOR 564
Pursuit of high-oxidation state phosphinidene complexes of the group 6 metals for metathesis reactivity
Robert K. Thomson, [email protected]. Department of Chemistry and Biochemistry, University of Oklahoma, Norman,
Oklahoma, United States
Phosphorus in low-coordinate environments has long been known to exhibit chemistry more similar to carbon than
nitrogen. The "carbon-copy" behavior of low-coordinate phosphorus is well-understood in the context of organic synthesis,
and recent work has also demonstrated that P=C bonds can undergo addition polymerization, analogous to that seen for
alkenes. Similar "diagonal" analogies to C=C bonds have not been demonstrated for metathesis reactions of P=C bonds.
Alkylidene complexes (M=CHR) of the group 6 metals have proven highly successful in catalyzing olefin metathesis
reactions, including the ring-opening metathesis polymerization of cyclic olefins. This talk will describe our recent efforts to
develop new high oxidation state phosphinidene complexes (M=PR) of the group 6 metals that are isolobal with group 6
alkylidene species, and the examination of their reactivity in the context of metathesis.
INOR 565
Aluminum chemistry featuring nitrogen-based ligands for stabilization of cations and radicals
Jason D. Masuda1,2, [email protected], William L. McClennan1,2, Nick A. Giffin1,2. (1) Deparment of Chemistry,
Saint Marys University, Halifax, Nova Scotia,
Canada (2) The Atlantic Centre for Green Chemistry, Saint Mary's University, Halifax, Nova Scotia, Canada
Our current research program involves the reactivity of main group cations and radicals supported by a number of
nitrogen and N-heterocyclic carbene (NHC) ligands. Recently we have moved from the phosphorus radicals and cations
to carbon- and aluminumcentered systems. We will report our recent progress on systems supported by amidinates,
NHCs and imidazolin-2-iminates and possible expansion to gallium and other M 3+ complexes.
INOR 566
Actinide speciation in aqueous chloride and pseudochloride solutions
Lynda Soderholm, [email protected], S. Skanthakumar. Argonne Natl Lab, Argonne, Illinois,
United States
A metal ion’s speciation can have a significant influence on its solution solubility, stability, and reactivity as well as the
nature and structure of its precipitates. Codissolved counterions compete with each other and with solvent molecules for
inner and outer-sphere ligation, thus impacting chemical and physical properties. Complementing studies of actinide
halides and pseudohalides in non-aqueous solvents, our studies focus on their speciation in aqueous solutions. Although
somewhat more restrictive than organic-based systems, the redox window permitted by water nevertheless allows the
stabilization of a variety of oxidation states for the lighter 5f ions U – Pu. Using highenergy x-ray scattering (HEXS) as a
direct structural probe of solution correlations, we are able to obtain metrical data that permits a coupling of structure with
thermodynamic stability constants. Examples include recent experiments on metal-halide and pseudohalide correlations
obtained for the purpose of determining the relative stability of complexes that form as a function of varying solution
conditions. By systematically varying counterion concentration, we are able to correlate a complexant’s concentration
along with its composition and structure. From these data it is possible to extract stability constants selected species and
relate them directly to chemical details of the metal-ion complexes. This approach is providing direct structural details
including bond distances and ligation in both first and second coordination spheres and thus providing new insights of
importance to theoretical efforts centered on simulating metal-ion energetics in solution relevant to predictive modeling.
This work was performed for the
U.S. DOE, OBES, Division of Chemical Sciences, Geosciences, and Biosciences, Heavy Elements Chemistry, and is
funded at Argonne National Laboratory under contract DE-AC02-06CH11357.
INOR 567
Synthesis and combustion of nitrogen-rich f-element complexes
Jacqueline M. Veauthier, [email protected], Jaqueline L. Kiplinger, Bryce C. Tappan,
Nicholas E. Travia, Kevin Browne, Brian L. Scott, Neil J. Henson, Alexander H. Mueller, David E. Chavez, Andrew T.
Nelson. Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Actinide nitrides are ideal materials for advanced nuclear fuels due to their high fissile metal densities, thermal stabilities,
and high thermal conductivities. The major impediment to the use of actinide nitride fuels is the synthesis of bulk high
purity material. Conventional methods are time-consuming and often lead to nitride products that contain carbon and
oxygen impurities which degrade the thermal properties of the resulting fuel materials. Our team is investigating a new
approach to the synthesis of high purity f-element nitrides through the synthesis of f-element complexes with nitrogen-rich
ligands. We have demonstrated that these types of complexes undergo a self-sustained combustion reaction to yield felement nitrides. The presentation will describe new complexes and their combustion reactions.
INOR 568
Actinide-arene interactions and their use in carbon-element bond forming reactions
Polly L. Arnold3, [email protected], Jamie McKinven3, Johann Hlina3, Rianne Lord3, Rami Batrice2, Nikolas
Kaltsoyannis4, Moris Eisen1, Michael Gardiner6, Jason B.
Love5. (1) Technion - Israel Institute of Technology, Haifa, Israel (2) Technion-Israel
Institute of Technology, Haifa, Israel (3) Univ of Edinburgh Sch of Chem, Edinburgh,
London, United Kingdom (4) Department of Chemistry, University College London,
London, United Kingdom (5) School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom (6) University of
Tasmania, Hobart, Tasmania, Australia
Organometallic f-block compounds have shown many interesting small molecule activation reactions, including
hydrocarbon C-H bond cleavage, and the study of interactions of f-block cations with soft hydrocarbon and arene ligands
provides important contributions to the understanding of covalency in f-element ligand bonding that is needed for nuclear
waste handling.
We will present new f-block complexes with simple ligands that bind and reduce arenes spontaneously, even at room
temperature, forming inverse arene sandwich complexes. The arenes are sufficiently activated, and the conditions
sufficiently mild, that a regioselective C-H bond functionalisation with boranes is possible. This has allowed studies of the
catalytic capabilities of these complexes, and the first f-element catalysed catalytic alkyne cyclotrimerisation reactions.
Details of the mechanism, requirements for the ancillary ligands, and C-H bonding interactions with the metal centre will
be shown. One of the factors that drives the chemistry is the favourability of δ-symmetry bonding interactions with the πsystem. We will show new chemistry of a macrocyclic ligand (meso-octamethyl-trans-calix[2]benzene[2]pyrrolide) that
exploits this feature in the formation of new bis(arene)sandwich-like geometries, as well as forming complexes with close
metal-metal distances.
INOR 569
Covalency and the relative roles of 5f and 6d orbitals in actinide metal-ligand bonds
David L. Clark, [email protected]. Natl Security Education Center, Los Alamos National Laboratory, Los Alamos, New
Mexico, United States
The presence of covalency in complexes of the 4f and 5f elements has been a source of intense research and
controversy. Recent studies from our laboratories have focused on application of ligand K-edge XAS and electronic
structure calculations for evaluating the relative roles of valence 5f and 6d orbitals in chemical bonding for actinides.
Chlorine K-edge X-ray absorption spectroscopy on MCl62- (Ti, Zr, Hf) and AnCl62- (An = Th, U, Np, Pu) systems indicates
the presence of covalent interactions between both Cl 3p and An 5f and 6d orbitals, with the relative contributions
changing across the actinide series.
INOR 570
Enabling the exploration of metal-ligand bonding in light actinides: One of Jackie Kiplinger’s many synthetic
legacies
David E. Morris, [email protected]. Chemistry Division, Los Alamos National
Laboratory, Santa Fe, New Mexico, United States
Of Jackie Kiplinger’s many enduring contributions to synthetic inorganic chemistry, her efforts in developing an enormous
array of thorium and uranium organometallic complexes with diverse and electronically interesting ligand sets clearly
stands out. The variations in uranium metal oxidation state (trivalent through hexavalent) and metalligand bond orders
have provided an ideal test bed to explore manifestations of metal forbital involvement in covalent bonding and metalmetal interactions in multimetallic systems using conventional spectroscopic and electrochemical probes. Following a brief
retrospective of Jackie’s career leading up to this celebratory symposium, this presentation will highlight some of the novel
physical chemical data derived from our fifteen year collaboration demonstrating the surprising degree of metal-ligand
covalent bonding in the light actinides.
INOR 571
Selective heterogeneous electrocatalytic reduction of CO2 to CO or HCOO- using iron porphyrin complexes
Abhishek Dey, [email protected]. IACS, Kolkata, India
Iron porphyrin complexes having H-bonding distal pocket are used for heterogenous electrocatalytic reduction of CO2 to
CO. In particular, an iron porphyrin complex with a proton transfer motif in its distal side is found to reduce CO 2 to CO as
well as formic acid selectively under different experimental conditions. The selectivity is governed by relative binding
affinity of the reduced Fe center towards CO2 and H+ which in turn can be tuned by utilizing the distal functional groups.
Resonance Raman spectroscopy and electrochemical techniques are used to elucidate the reaction mechanism. In
particular, the role of different intermediates in governing the selectivity will be discussed.
INOR 572
Navigating structure-activity relationships in molecular electrocatalysts for CO 2 reduction
Robert J. Nielsen1, [email protected], Samantha I. Johnson 1, Yan-Choi Lam1,
William A. Goddard2. (1) Caltech, Pasadena, California, United States (2) Chemistry 139-74, Calif Inst of Technology,
Pasadena, California, United States
As a route to earth-abundant electrocatalysts for CO2 reduction, we have used quantum mechanical calculations including
solvation to uncover relationships between the composition of known catalysts and their attributes (i.e. rate, product
selectivity, onset potential.) Among these are Milstein’s (PNP)Fe(CO)H 2 and Meyer and Brookhart’s (PoCoP)Ir(MeCN)H2
(demonstrated to electrochemically reduce CO2 selectively to formate in water.)
Modeling (PNP)Fe(CO)H2 (a demonstrated CO2 hydrogenation catalyst) in an prospective electrochemical cycle
generating formate, we find that an impractical potential would be required for the two-electron reduction regenerating the
dihydride, and that both hydrides would be prone to hydrogen evolution during such a cycle. A space of earth-abundant
metal hydrides characterized by (L3)ML2H was explored for free energy surfaces supporting selective, low-overpotential
CO2 reduction. Replacing the PNP ligand with a redox-active pincer ligand effectively raises the computed potential
required to reduce Fe(II) by 2-electrons over a volt, into an attractive range. Replacing a hydride in the “H-Fe-H” core with
a lesser sigma donor erodes the driving force for hydride transfer, but this can be restored upon substitution of a more
nucleophilic metal. We will discuss the influence of compositional degrees of freedom on free energy surfaces and make
comparisons to the successful template provided by the iridium catalyst.
INOR 573
Ir–H species as key intermediates in CO2 hydrogenation, formic acid dehydrogenation and photochemical CO 2
reduction
Etsuko Fujita1, [email protected], James T. Muckerman1, Yuichiro Himeda2. (1) Chemistry
Department, Brookhaven National Laboratory, Upton, New York, United States (2)
National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
The interconversion between CO2 and formic acid has received renewed attention as a hydrogen storage system. We
have shown reversible H2 storage near room temperature and ambient pressure with pH as the ‘switch’ for controlling the
direction of the reaction using complex 3 as a catalyst.1 We have prepared several bio-inspired ‘proton-responsive’
mononuclear Ir(III) catalysts for CO2 hydrogenation under slightly basic conditions and formic acid decomposition under
slightly acidic conditions (2 and 4 in the figure are among those studied), and gained mechanistic insight through
investigation of the factors that control the effective generation of formate by experimental 2 and theoretical approaches.
Both results clearly demonstrate Ir–H species as key intermediates in the interconversion. We have now isolated Ir–H
species of complex 1 and other Ir–H species that are speculated to be intermediates for photochemical CO 2 reduction.
We will present the spectroscopic, photochemical, and electrochemical properties of these species.
The work carried out at BNL was supported by the U.S. Department of Energy, Office of
Science, Division of Chemical Sciences, Geosciences, & Biosciences, Office of Basic Energy Sciences under contract
DE-AC02-98CH10886. Y. H. thanks the Japan Science and Technology Agency, ACT-C for financial support.
1. J. F. Hull, et al. Nat. Chem. 2012, 4, 383.
2. W.-H. Wang, et al. ACS Catal., 2013, 3, 856
INOR 574
Reduction of CO2 to methanol by an organic hydride via hydride transfer/proton transfer steps
James T. Hynes3,2, [email protected], Charles Musgrave1, Chern-Hooi Lim1, Aaron Holder1. (1) Chemical and
Biological Engineering, University of Colorado at
Boulder, Boulder, Colorado, United States (2) Chemistry, Ecole Normale Superieure,
Paris, France (3) Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado, United States
Conversion of carbon dioxide to fuels enabling a closed-carbon cycle powered by recyclable energy has the potential to
dramatically impact the energy and environmental fields, and accordingly has received very considerable experimental
and theoretical attention. In this talk, we will describe quantum chemical calculations on the efficient catalytic reduction of
CO2 to CH3OH by pyridine. This pathway involves the production of the hydride donor 1,2-dihydropyridine PyH2, a 2H+/2etransfer product of pyridine (Py). Dihydropyridine then acts as a powerful recyclable organo-hydride that reduces CO2 to
CH3OH via three hydride and proton transfer (HTPT) steps. The coupled (or uncoupled) character of these three steps, as
well as the driving force for them, and the involvement of proton relay chains to lower their free energy barriers, will be
discussed, as will the connection to several experimental results.
INOR 575
Homogeneous reduction of CO2 by [Ni(cyclam)]+, poisoning by CO, detoxification by CO sponge, and useful
conversion of CO by tandem catalysis
Clifford P. Kubiak, [email protected], Jesse Froehlich, Jason Tillman. UNIVERSITY
OF CALIFORNIA, SAN DIEGO, La Jolla, California, United States
The homogeneous electrochemical reduction of CO2 by the molecular catalyst [Ni(cyclam)]2+ was studied by
electrochemistry and infrared spectroelectrochemistry.
The electrochemical kinetics were probed by varying CO 2 and proton concentrations. CO2 reduction intermediates are
observed in infrared spectra obtained from spectroelectrochemical experiments. The major species observed are
[Ni(cyclam)(CO)]+ and CO2 adducts of [Ni(cyclam)]+. The rate limiting step during electrocatalysis is determined to be
catalyst deactivation by the CO produced from CO 2 reduction. Another macrocyclic complex, [Ni(TMC)]+ (TMC = 1,4,8,11tetramethyl-1,4,8,11tetraazacyclotetradecane), is deployed as a CO scavenger in order to inhibit the deactivation of
[Ni(cyclam)]+ by CO. Addition of the CO scavenger is shown to dramatically increase the catalytic current for CO 2
reduction. Evidence for the
[Ni(TMC)]+ acting as a CO scavenger includes the observation of [Ni(TMC)(CO)] + by IR. Recent studies of the productive
scavenging of CO by uptake in tandem catalytic reactions will be reviewed. By adjustment of pH [Ni(cyclam)] 2+ can
catalytically cogenerate synthesis gas (CO + H2). Electrochemically produced synthesis gas was used to catalytically
hydroformylate styrene in a single reactor without poisoning of [Ni(cyclam)]2+.
INOR 576
What theory can reveal about carbon dioxide reduction and the role of molecular catalysts
Emily A. Carter, [email protected]. Department of Mechanical and Aerospace Engineering, Program in Applied and
Computational Mathematics and Andlinger Center for Energy and the Environment, Princeton University, Princeton, New
Jersey, United States
We have been using well-validated first principles quantum mechanics schemes combined with continuum solvation (and
sometimes microkinetics simulations) to explore mechanisms associated with carbon dioxide reduction by homogeneous
and heterogeneous (photo-)electrocatalysts. We will first review our work in this area to provide context for the
presentation of our latest findings on the roles played (or not) by aromatic amines and water during the
photoelectrochemical reduction of CO2 to methanol at a p-GaP electrode surface. We may also highlight key predictions
of the mechanisms for Mn- and Re-catalyzed reduction of CO2 to CO, although this latter topic is the subject of another
talk in the CATL division at this meeting and the interested attendee should go to that talk for an in-depth look at those
homogeneous electrocatalysts
INOR 577
Molecular catalysis of water oxidation and CO2 reduction in dye sensitized photoelectrosynthesis cells (DSPEC)
Thomas J. Meyer3, [email protected], Javier Concepcion4, Zuofeng Chen5, Michael Norris6, Mingtian Zhang7, Michael
Coggins3, Robert Binstead3, Na Song3, Dennis L.
Ashford3, Matthew Sheridan3, Peng Kang3, Sheng Zhang3, Neyde Y. Iha2, Maurice
Brookhart3, Joseph L. Templeton1. (1) UNC Chapel Hill, Chapel Hill, North Carolina, United States (2) Departamento de
Quimica Fundamental, Instituto de Quimica - Universidade de Sao Paulo, Sao Paulo, Brazil (3) University of North
Carolina, Chapel
Hill, North Carolina, United States (4) Brookhaven National Lab, Upton, New York,
United States (5) Tongji University, Shanghai, China (6) University of Washington, Seattle, Washington, United States (7)
Tsinghua University, Beijing, China
Integration of light absorption and catalysis with control of interfacial electron transfer dynamics are at the heart of devices
for using sunlight to make solar fuels. A Dye Sensitized Photoelectrosynthesis Cell (DSPEC) combines light absorption
and catalysis in a chromophore-catalyst assembly with stable, large band gap oxide semiconductors - TiO2, NiO, SnO2.
Excitation and injection by the chromophore leads to the buildup of multiple oxidative or reductive equivalents at molecular
catalysts for water oxidation to O2 or reduction of water/H+ to H2 or CO2 to a reduced carbon fuel. Significant progress
has been made in the evolution of molecular catalysts for use in DSPEC applications. Surface or assembly-bound Ru(II)
polypyridyl complexes HAVE been investigated mechanistically for water oxidation catalysis and incorporated into
DSPECs for solar water splitting. Extension to first row transition metal complexes has led to working catalysts based on
both Cu(II) and Fe(III). A Ru(II) polypyridyl complex has been utilized in water to reduce CO2 to controlled syngas
(H2:CO) mixtures both in solution and on electrode surfaces. Ir pincer complexes have been identified that undergo rapid,
robust reduction of CO2 to formate in aqueous solution and on the surfaces of high surface area carbon electrodes.
INOR 578
Single junction CZTSSe and tandem CZTSSe/hybrid perovskite solar cells from molecular-inks: Mapping the
effects of composition on material quality and device performance
Hugh W. Hillhouse, [email protected]. Molecular Engr and Sciences Rm 123, University of
Washington, Seattle, Washington, United States
Given the terawatt-scale of future energy needs, the most promising future photovoltaic materials should be Earth
abundant with their primary mineral resources distributed across many geographic regions. In addition, their supply chains
should be robust to reduce concerns of price volatility. The process of forming the solar cell should be scalable, low-cost,
and not utilize dangerous or toxic materials if possible. One candidate for single junction solar cells or the bottom junction
of tandem solar cells is kesterite structured Cu2ZnSn(S,Se)4 (CZTSSe) and similar alloy materials.
Conventionally, thin film chalcopyrite and kesterite solar cells have been synthesized by evaporating or sputtering metals
followed by sulfurization or selenization. Recently, a potentially low-cost high-throughput approach has been
demonstrated that forms the quaternary or pentenary chalcogenide directly from a solution-phase process utilizing
hydrazine as a solvent and complexing agent. Here, we report the development of a class of solution-phase routes to
CZTSSe that do not use hydrazine or nanocrystals. We have developed a DMSO/thiourea solvation/complexation
chemistry that yields 11.1% efficient CZTSSe solar cells (compared to12.6% for the hydrazine route). Further, we have
developed a combinatorial ultrasonic spray coater and highthroughput screening method to map the optoelectronic
properties of CZTSSe as a function of composition and dopants. The presentation will focus on the results of the
combinatorial experiments and show that CZTSSe is capable of exceeding 70% of the theoretically possible Voc.
We have also developed inks and processing strategies for hybrid perovskites (HPs) and novel tandem architectures for
combining low-bandgap kesterite CZTSSe or chalcopyrite CIGSe with a high-bandgap HPs. The presentation will also
highlight combinatorial experiments with HP inks that show the possibility of achieving 90% of the theoretical limit of Voc
for high-bandgap HPs suitable for tandems.
INOR 579
Solution-processed electrochromic and photovoltaic thin films from nanocrystal building blocks
Delia J. Milliron1, [email protected], Anna Llordes2,1, Ajay Singh2,1. (1)
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas,
United States (2) The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Electronic materials for energy technologies must not only meet demanding performance requirements, they also must be
processed by cost effective means and over large areas. Colloidal nanocrystals offer a promising route to address all of
these requirements since composition can be synthetically controlled and solvent dispersibility can facilitate low cost, high
throughput deposition of uniform thin films. I will highlight two examples, both requiring nanocrystals of complex
compositions, which can be prepared by carefully balancing reactivity of precursors for each component. First, doped
metal oxide nanocrystals are synthesized that exhibit tunable plasmonic resonance in the near infrared spectral region.
Together with soluble transition metal oxides, in the form of polyoxometalates, these are the building blocks for a new
breed of electrochromic devices. “Smart windows” based on this concept can dynamically control transmission of solar
heat and light into buildings. Second, multinary metal chalcogenide nanocrystals, such as CIS and CZTS, are synthesized
in the metastable wurtzite phase. Their metastability facilitates grain growth during rapid thermal annealing of solutiondeposited thin films, triggered by the phase transition to the typical tetragonal phases of these semiconductors. A battery
of in situ techniques is used to forge a mechanistic connection between crystal grain growth and phase transformation.
INOR 580
Synthesis of transition metal chalcogenide and pnictide nanoparticles for applications in photovoltaics
Amy L. Prieto3, [email protected], Dan Agocs1, Max B. Braun2, Sarah
Fredrick4, Lasantha Korala2, Rebecca C. Miller2. (1) Colorado State University, Fort
Collins, Colorado, United States (2) Chemistry, Colorado State University, Fort Collins,
Colorado, United States (3) Chemistry Department C210, Colorado State University, Fort Collins, Colorado, United States
There is a clear need for well-controlled synthetic methods for compositionally complex semiconductor nanoparticles with
interesting properties. However, subtle changes in reaction conditions can often result in the presence of off-stoichiometric
phases or even impurity phases that do not have the desired properties. This talk will focus on our efforts to develop
reactions for the phase-pure synthesis of a family of transition metal chalcogenides and pnictides composed of earth
abundant elements. In particular, we are interested in compounds with direct band gaps that could have applications in
photovoltaics.
INOR 581
Photophysics in metal enriched and stoichiometric quantum dots
Matthew Sfeir1, [email protected], Erik Busby1,2, Nicholas C. Anderson2, Jonathan S.
Owen2. (1) Ctr for Functional Nanomaterials, Bldg 735, Brookhaven National
Laboratory, Upton, New York, United States (2) Chemistry, Columbia University, New York, New York, United States
Many fundamental properties of colloidal semiconductors quantum dots, particularly the photoluminescence quantum yield
and related phenomena such as blinking, are highly sensitive to the surface structure. Previous studies of quantum dot
photophysics suggest a variety of surface traps with different chemical origins lead to distinct dynamic behavior, affecting
the excited state lifetime, blinking, or both. Moreover, fluorescence quantum yield is not always correlated to the
measured total lifetime, due to the presence of an “OFF” (or “dark”) state that is not reflected in the recombination
dynamics of the “ON” (or “bright”) state. The origins of nanocrystal blinking remain uncertain and, while the correct model
is still under debate, distinct types of trap states may warrant different models of blinking. Here, we examine a particular
type of surface trap by quantifying the effect of metal enrichment (relative fraction of surface Cd to surface Se) on the
trapping of excitons in CdSe quantum dots. Displacement of surface bound cadmium carboxylate exposes selenium
atoms and dramatically reduces the overall photoluminescence quantum yield of the quantum dot. Transient absorption
and time resolved photoluminescence decay kinetics demonstrate that the rate of hole trapping increases as surface
selenium atoms are exposed. A nonlinear relationship between the exciton decay rate and the fraction of surface
selenium atoms is observed that demonstrates a heterogenous dependence of the hole trapping kinetics on the ligand
coverage. The observed decrease in the PLQY cannot be accounted for by the change in photoluminescence decay
kinetics alone and indicates that the fraction of nanocrystals in the “OFF” state increases in the stoichiometric
nanocrystals.
INOR 582
New matrix engineering strategies for efficient charge transport in quantum dot solids
Matt Law, [email protected]. University of California, Irvine, Irvine, California, United
States
Colloidal semiconductor quantum dots (QDs) are attractive building blocks for solar photovoltaics (PV). In this talk, I will
provide an overview our ongoing efforts to design lead salt QD thin film absorbers for next-generation PV. Basic
requirements for QD absorber layers include efficient light absorption, charge separation, charge transport, and long-term
stability. I will first discuss several methods used to make conductive QD films by solution deposition and ligand
exchange. Studies of carrier mobility as a function of basic film parameters such as inter-QD spacing, QD size, and QD
size distribution have led to a better understanding of charge transport within highly disordered QD films. Efforts to
improve carrier mobility by enhancing inter-dot electronic coupling, passivating surface states, and implementing
rudimentary doping will be highlighted. Engineering the inter-QD matrix to produce QD/inorganic or QD/organic
nanocomposites is introduced as a promising way to optimize coupling, remove surface states, and achieve long-term
environmental stability for high-performance, robust QD films. To obtain large photocurrent from QD solar cells, it is critical
to increase the minority carrier diffusion length to rival the optical absorption length, possibly by harnessing band-like
transport through extended electronic states. The relative roles of superlattice order, energy disorder, and surface states
in this regard will be summarized. New results from in situ spectroscopic studies of QD field-effect transistors will be
discussed.
INOR 583
Designer semiconductor nanocrystal electronic and optoelectronic materials and devices
Cherie R. Kagan, [email protected], Soong Ju Oh, Ji-Hyuk Choi, Yuming Lai, David Kim, E D. Goodwin, Aaron T.
Fafarman, Benjamin Diroll, Christopher B.
Murray. University of Pennsylvania, Philadelphia, Pennsylvania, United States
Advances in synthetic methods allow a wide range of semiconductor nanocrystals
(NCs) to be tailored in size and shape and to be used as building blocks in the design of NC solids. However, the long,
insulating ligands commonly employed in the synthesis of colloidal NCs inhibit strong interparticle coupling and charge
transport once NCs are assembled into the solids state as NC arrays. We employ a range of short, compact ligand
chemistries to exchange the long, insulating ligands used in synthesis and to increase interparticle coupling. These ligand
exchange processes can have a dramatic influence on NC surface chemistry as well as NC organization in the solids,
showing examples of short-range order. Synergistically, we use 1) thermal evaporation and diffusion and 2) wet-chemical
methods to introduce extrinsic impurities and nonstoichiometry to passivate surface traps and dope NC solids. NC
coupling and doping provide control over the density of states, the carrier statistics and the Fermi energy. Examples of
strong coupling and doping in II-VI and IV-VI semiconductor NC solids will be given that yield high-mobility, highconductivity solution-deposited NC solids. Temperature--dependent transport measurements of these materials are
consistent with a transition from localized to extended-state charge transport. These high mobility n- and p-type materials
are used as the semiconductors to construct large-area, flexible, field-effect transistors and integrated circuits and for
solar photovoltaics.
INOR 584
Luminescent ruthenium probe for DNA mismatches
Adam N. Boynton2, [email protected], Anna J. McConnell1, Jacqueline K.
Barton2. (1) Department of Chemistry, University of Cambridge, Cambridge, United
Kingdom (2) Division of Chemistry and Chemical Engineering, California Institute of
Technology, Pasadena, California, United States
Our laboratory has focused on the design of metalloinsertors in an effort to prepare new chemotherapeutic agents
targeted towards mismatch repair (MMR)-deficient cells. Metalloinsertors bind selectively to DNA mismatches and show
preferential selectivity in MMR-deficient cells. We have also been interested in designing luminescent ruthenium
complexes that could function as diagnostic probes for DNA mismatches. It is known that the complex [Ru(bpy) 2(dppz)]2+,
while non-emissive in aqueous solution, exhibits a restored luminescence upon binding to duplex DNA. In this work, a
new sterically expansive ligand (BNIQ) was synthesized and coordinated to ruthenium to create a new luminescent
complex [Ru(bpy)2(BNIQ)]2+. The luminescent properties of this complex in the presence of well-matched and mismatched
DNA duplexes were examined using steady state and emission lifetime measurements. The complex exhibits an
enhanced luminescence in the presence of mismatched DNA relative to well-matched DNA, suggesting that this complex
may be utilized as a novel probe for DNA mismatches.
INOR 585
1
H- and 19F-NMR spectroscopic studies of 4-fluorophenylbiguanide with the interface of reverse micelles
Jarukorn Sripradite4, Nuttaporn Samart2, Anan Tongraar3, Debbie C. Crans1, [email protected]. (1) Colorado
State University, Fort Collins, Colorado, United States (4) Chemistry, Suranaree University of Technology, Nakhon
Ratchasima, Nakhon Ratchasima, Thailand
The 4-fluorophenylbiguanide (4-FPBG) is related to antimalarial drugs of which the drug penetration is an important
aspect of mode of action. Furthermore, it is related to 1- phenylbiguanide (PBG) interacts with membrane like interfaces
and was characterized using a reverse micelle (RM) model system in our laboratory1. In this work, we used not only 1HNMR to study the interaction of 4-FPBG with reverse micelles (RMs) but also used 19F-NMR. The spectral changes are a
sensitive probe of the properties of 4-FPBG and as the RMs are varied the interaction of the compound can change and
will be reflected in the chemical shifts of the compound. For example, the chemical shift both of all 4-FPBG that clearly
confirm the form of compound is that in the deprotonated and mono-protonated forms. The 1H NMR and 19F-NMR studies
demonstrated that the 4FPBG compound in an aqueous environment changed from the aqueous environment
to an interfacial environment when placed in the model membrane system. The signals for the deprotonated form are 0.05
to 0.20 ppm downfield from the mono-protonated form that exists in solutions at pH 2 through 9. In summary, we found
that 4-FPBG show similar changes as the PBG which were found to interact with different regions of the interface, with the
phenyl group penetrating the hydrophobic interface while the biguanide remains in the water pool.
INOR 586
N-hydroxysulfonamides RSO2NHOH as nitroxyl (HNO) donors: Improved preparation and kinetics of nitroxyl
generation
Sonya K. Adas1, [email protected], Nicola E. Brasch2, Paul Sampson3. (1) Chemistry and Biochemistry , Kent State
University, Kent, Ohio, United States (2) School of Applied Sciences, Auckland University of Technology , Auckland , New
Zealand
Nitroxyl (HNO) is an important biomolecule whose biological chemistry is challenging to study due to its rapid dimerization.
As a result, a variety of HNO donors have been developed as in situ sources of HNO, including several Nhydroxysulfonamides RSO2NHOH (e.g. Piloty’s acid (R=Ph), MSHA (R=Me)). As part of a program aimed at
understanding the fundamental bioinorganic chemistry of HNO, we needed to prepare these N-hydroxysulfonamides as
well as the new related HNO donor CF 3SO2NHOH. Surprisingly, we found that there is a dearth of reliable and efficient
approaches for the preparation of these targets. Herein, we will outline improved preparative approaches to these N-
hydroxysulfonamide HNO donors. In addition, we will present detailed decomposition kinetics for HNO generation from
these compounds, using aquacobalamin to quantify HNO generation.
INOR 587
Exploring the cellular activity of polyazine bridged Ru(II)-Rh(III) supramolecules in rat malignant glioma F98 cells
Jie Zhu2, [email protected], Karen S. Brewer1. (1) Virginia Polytech Inst, Blacksburg,
Virginia, United States (2) Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United
States
Mixed-metal Supramolecular complexes with photo-induced DNA modification can be used as potential PDT
(photodynamic therapy) agents.1 The Ru-Rh bimetallic complexes of the design [(TL)2Ru(BL)Rh(TL)X2]3+(TL = terminal
ligand; BL = bridging ligand; X= labile ligand) exhibit visible light induced DNA photobinding and oxygen independent
photocleavage.2 However, cellular uptake and photocytotoxicity of these bimetallic complexes remain unexplored.
Variation of the TL on the PS (photosensitizer) moiety provides insight into the relationship between structure and
biological activity. Uptake of Ru-Rh bimetallic complexes towards rat malignant glioma F98 cells was determined by ICPMS. The light-activated antiproliferative activity of supramolecular Ru-Rh complexes was directly tested against F98 MG
cell line. Low cytotoxicity was observed for the treatment of cells with metal complexes under dark conditions. Significant
photocytotoxicity and cell growth inhibition were established with the treatment of metal complex under photolysis.
Acknowledgement is made to VT ICTAS 119552 and the National Science Foundation 478898 for their generous funding.
1.
Wang, J.; Newman, J.; Higgins, S. L. H.; Brewer, K. M.; Winkel, B. S. J.; Brewer, K. J., Red-Light-Induced
Inhibition of DNA Replication and Amplification by PCR with an Os/Rh Supramolecule. Angew Chem Int Edit 2013, 52 (4),
1262-1265.
2.
Wang, J.; Zigler, D. F.; Hurst, N.; Othee, H.; Winkel, B. S. J.; Brewer, K. J., A new, bioactive structural motif:
Visible light induced DNA photobinding and oxygen independent photocleavage by Ru-II, Rh-III bimetallics. Journal of
Inorganic Biochemistry 2012, 116, 135-139.
INOR 588
Cytotoxic and DNA binding properties of Mn(I) and Re(I) carbonyl perrhenato complexes
Jalisa Taylor2, [email protected], Saroj K. Pramanik2, Jeanette A. Krause3,
Santosh K. Mandal1. (1) Inorganic Chemistry, Morgan State University, Parkville,
Maryland, United States (2) Biology Department, Morgan State University, Baltimore,
Maryland, United States (3) Chemistry, University of Cincinnati, Cincinnati, Ohio, United
States
We have synthesized a variety of tricarbonyl manganese(I) and rhenium(I) diphosphine perrhenato complexes of the type,
fac-(CO)3(P2)MOReO3 from the reactions of the corresponding hydrido complexes, fac-(CO)3(P2)MH with perrhenic acid,
where, P2 = chelated diphosphines and M = Mn or Re. Recently we solved the crystal structure of fac(CO)3(P2)MnOReO3, where P2 = 1,4-Bis(diphenylphosphino)butane. We have observed that the rhenium analogues are
highly cytotoxic against U-937 blood cancer cell lines. For example, the IC50 value of fac-(CO)3(P2)ReOReO3, where, P2 =
1,3Bis(diphenylphosphino)propane, is less than 1 µM. Additionally, we have determined from electronic spectroscopy that
the above rhenium perrhenato complex binds to DNA in an intercalative mode. We would like to present our results on the
cytotoxic behavior and DNA binding properties of both manganese and rhenium (diphosphine) perrhenato complexes.
INOR 589
Photosensitization of singlet oxygen by ruthenium(II) polypyridyl complexes for DNA photocleavage
Stephanie Yang1, [email protected], Kai Wang2,
[email protected], Benjamin R. Williams1, Sharon J. Nieter Burgmayer1. (1) Bryn Mawr College, Rockville, Maryland,
United States (2) Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania, United States
Ruthenium polypyridyl complexes can intercalate double stranded DNA, inhibiting DNA replication and cell proliferation.
These complexes can also photochemically induce DNA cleavage by damaging the genetic material of cells. These
abilities affirm their potential use as antitumor agents, especially in the field of photodynamic therapy. In this study we
report the photocleavage ability of a variety of ruthenium(II) pteridinyl complexes with varied substituents on the third
bidentate ligand. Only complexes with a cleaved terminal pteridine ring (ring-open), for example, [Ru(bpy)2L-aap]2+ exhibit
DNA photocleavage.
Compounds were incubated with plasmid DNA for 2 hours and photocleavage ability was assessed using gel
electrophoresis. The mechanism used to cleave DNA involves the photosensitization of singlet oxygen, as determined
from experiments with reactive oxygen species inhibitors. Singlet oxygen quantum yields were obtained through
spectroscopic studies conducted with the fluorescent probe 1,3-diphenylisobenzofuran.
Ru(bpy)2L-keto degrades into Ru(bpy)2L-aap over time in the presence of base.
INOR 590
Evaluation of heme peripheral groups interactions in low-dielectric constant media
Alaina Stockhausen1, [email protected], Jose Cerda2. (1) Chemistry, Saint Joseph's
University, Glenmoore, Pennsylvania, United States (2) Saint Josephs University, Philadelphia, Pennsylvania, United
States
In this study, we measured the contributions of the ionization of the heme propionates to the reduction potentials of heme
b and heme a (bis)N-methylimidazole complexes in various low-dielectric constant conditions. Additionally, we measured
the effects of Hbond to the heme a formyl group on the reduction potential of the heme. The performed electrochemical
measurements show that ionization of the heme propionates lead to the largest redox change in dichloromethane with no
electrolyte. The measured reduction potential changes for heme b and heme a were – 55 and -47 mV (±10 mV) per
ionized propionate, respectively. For heme a, the study demonstrates how the dielectric constant of the medium is
important in the magnification of the DpKa upon redox-linked ionization of the heme propionates and their roles in the
proton pump of cytochrome c oxidase. Additionally, we carried out a detailed study on the H-bonding properties of heme a
model compounds (copper mono- and di-acetyl porphyrins) and the effects of the dielectric constant of the solvent on the
measured dissociation constant (Kd) between various H-bond donors and the copper porphyrins. Our measurements
show that H-bonds between the copper porphyrins and TFA or phenol are significant in benzene and dichloromethane,
but extremely weak in the presence of acetonitrile. This study shows how the dielectric constant of the medium also plays
a role in modulating the properties of heme a through H-bonding of its formyl group.
INOR 591
Spectroscopic methods to characterize non-heme iron enzymes (monooxygenase and dioxygenase)
Bishnu Subedi1, [email protected], Brad S. Pierce2. (1) Department of
Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas,
United States (2) Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas, United
States
In contrast to heme enzymes where iron center is located in porphyrin ring with characteristic UV-Vis absorptions, nonheme iron enzymes lack this transition and require more advanced spectroscopic methods to study the enzyme active
site. Electron paramagnetic resonance (EPR) spectroscopic method is an useful technique to characterize
metalloenzymes containing paramagnetic active center. We used EPR spectroscopy to characterize an integer spin signal
(g ~ 16) associated to reduced diferrous center (S=4) in non-heme diiron enzyme and enzyme-nitrosyl complex {FeNO}7
(S=3/2) in mono iron enzyme.
INOR 592
Formation, characterization, and O-O bond activation of a bio-inspired peroxomanganese(III) complex
Hannah E. Colmer, [email protected], Timothy A. Jackson. University of Kansas, Lawrence, Kansas, United States
Peroxomanganese intermediates are proposed in many catalytic redox reactions governed by manganese enzymes, such
as manganese superoxide dismutase, manganese homoprotocatechuate 2,3-dioxygenase, and ribonucleotide
reductases. The geometric and electronic factors governing O-O bond activation of
peroxomanganese(III) species are poorly understood. We are investigating this area using a bio-inspired
peroxomanganese(III) complex supported by the neutral crossclamped cyclam ligand Me 2EBC. The geometric and
electronic structure of this peroxomanganese(III) adduct has been spectroscopically and computationally investigated and
the subsequent activation of the peroxo unit explored through mechanistic and reactivity studies. In particular, chemically
controlled cleavage of the OO bond of the peroxomanganese(III) adduct is examined to further the understanding of the
factors controlling O-O versus Mn-O bond cleavage for peroxomanganese(III) adducts.
O-O versus Mn-O bond cleavage in a peroxomanganese(III) complex
INOR 593
Binuclear complexes: Analogs for superoxide dismutase enzyme substrate binding studies
Joseph W. Kreft, [email protected], Ekkehard Sinn. Department of
Chemistry, Western Michigan University, Kalamazoo, Michigan, United States
Design and synthesis of ligands that can complex two different metals at two different sites has been achieved. Larger
ligand binding structures were attached to synthesized imidazoles. One imidazole nitrogen participated in the binding of
the larger ligand to a first metal and the second imidazolate anion post ionization can act as a bridge to bond to a second
different metal species. The first metal utilized in binding to the larger ligand structure was a copper metal. Different
transition metals namely iron or zinc may be used as the second metal. The resulting binuclear complex ultimately acts as
a biological mimic for the enzyme active site where the imidazole bridging action to metals is analogous to Cu-Zn bovine
erythrocyte superoxide dismutase enzyme substrate binding. Additional investigation is underway to bind, via a thiolated
carbon chain, the binuclear species to gold nanoparticles and substrates.
Binuclear complex with imidazole bridge to second metal species
INOR 594
Crystallization of protein models of non-coupled dinuclear copper proteins
Alexandra Sauer, [email protected], Melanie Ladd, Sarah Pedersen, Steven M.
Berry. Chemistry and Biochemistry, University of Minnesota-Duluth, Duluth, Minnesota,
United States
Using site-directed mutagenesis techniques, surface copper binding sites were added to the blue copper protein azurin
that mimic the Type 2, or catalytic copper centers of the non-coupled dinuclear copper protein family. These models
maintain copper binding at the electron transfer or Type 1 copper site in azurin, and support the additional surface copper
site. Three histidines were added to the azurin surface to model the Type 2 site of nitrite reductase (making NiR3His-Az)
and two histidines and one methionine were added to the surface to model peptidylglycine a-hydroxylating
monooxygenase (making PHM-Az). These two azurin variants were crystallized under various conditions in order to
determine their structures. Both were crystallized by the hanging drop method, with NiR3His-Az being grown in Imidazole
pH 8.0 buffer, while PHM-Az was crystallized in
Acetate pH 5.4, Tris pH 7.1 and Imidazole pH 8.0 buffers. Polyethylene glycol (2.3312.5%) was used as a precipitant and LiNO3 or CaCl2 (0-100 mM) as extra salts. Different strategies for cryoprotection
and dehydration of the crystals were examined in order to improve the order and thus diffraction quality of the protein
crystals. The proteins were dehydrated by transferring the crystals to droplets with approximately 1530% higher PEG. The
crystals were screened and full data sets were collected using a Rigaku Rapid II X-ray diffractometer at -150°C. The
proteins produced 1.3-1.75 Å structures with final R factors between 16.7-25.1% and R free values of 20.1-30.7%. The
final structures of these two proteins as well as an analysis for the copper binding site structure will be presented and
discussed.
INOR 595
Modeling oxidoreductase enzymes in the protein azurin
Tracy Roach1,2, [email protected], Garrett Stoddard1, Steven M. Berry1. (1) Chemistry and Biochemistry, University of
Minnesota Duluth, Duluth, Minnesota, United States (2) The College of St. Scholastica, Duluth, Minnesota, United States
Four variants of azurin were created that incorporate a type 2 (T2) copper site on the surface of azurin, in addition to its
naturally existing type 1 (T1) center, in order to model copper oxidoreductase enzymes. Additionally, more mutations have
been made on these variants that tune the reduction potential of the T1 copper center. Past studies have measured the
oxidoreductase activity of the T1 and T2 copper sites, or their ability to mimic other copper proteins. One assay under
investigation is the phenoxazinone synthase (PHS) activity assay, which catalyzes the oxidation of o-aminophenol to
aminophenoxazinone. Preliminary data on azurin variants with decreased T1 copper reduction potentials indicated
increased activity in the PHS assay. In order to validate this trend and give insight into the catalytic mechanism, a different
mutation, Met121Leu (M121L), was added to increase the reduction potential of the T1 copper center. We began by using
Quikchange mutagenesis to insert the M121L mutation into various azurin model proteins. All mutations were confirmed
through restriction digest analysis and DNA sequencing. The proteins were overexpressed in a recombinant E. coli
system and purified with good yields (17-48 mg per L cell culture). Spectroscopic
characterization and results of the activity of this new series of variants will be reported including the reduction rate of the
T1 Cu center in the models with the substrate, as well as the reoxidation rate with O 2 and peroxide oxidants.
INOR 596
Role of halogen substituents and substrate pKa in defining the substrate specificity of 2,6-dichlorohydroquinone
1,2-dioxygenase (PcpA)
Julia E. Burrows, [email protected], Monica Q. Paulson, Timothy E.
Machonkin. Whitman College, Walla Walla, Washington, United States
PcpA is a bacterial non-heme Fe(II) enzyme that oxidatively cleaves 2,6dichlorohydroquinone as a part of the pentachlorophenol (PCP) degradation pathway of Sphingobium chlorophenolicum. It
has been shown to be specific for orthodihalohydroquinones. Possible sources of this specificity include the substrate pK a,
and halogen bonding and/or metal-halogen secondary bonding, both of which depend upon halogen polarizability.
Substrate binding titrations showed a similar small shift in pKa values between the free substrate and the substrate bound
to the enzyme for all substrates. This suggests that PcpA may lack an active site base needed to deprotonate the
substrate, in contrast to the closely related catechol extradiol dioxygenase enzymes. Steady-state kinetic studies showed
that 2,6difluorohydroquinone is a poor substrate, similar to 2,6-methylhydroquinone, unlike 2,6dichloro- and 2,6dibromohydroquinone. The pH dependence of the kinetics of these substrates provides additional insights into the role of
substrate pKa. Together, these studies suggest that both a polarizable halogen substituent and the pK a of the substrate
play important roles in defining the substrate specificity of PcpA.
INOR 597
Nitrite reduction activity of azurin variants
Balabhadra Khatiwada, [email protected], Jacob Strange, Steven M.
Berry. Chemistry and Biochemistry, University of Minnesota, Duluth, Duluth, Minnesota, United States
Nitrite reductase (NiR) catalyzes the reduction of nitrite to nitric oxide in the denitrification stage of the nitrogen cycle. To
study the structure and function of this noncoupled dinuclear copper enzyme, models were designed by adding a second
copper binding site on the surface of the mononuclear copper protein azurin. The existing copper-binding site in azurin is
an electron transfer (T1) site and it is ligated by two histidines, a cysteine and a methionine residue similar to the T1 site
of NiR. This T1 copper site was maintained in azurin whereas an additional copper center, a catalytic type 2 (T2) copper
site similar to the T2 site of NiR was designed. The designed T2 copper site in azurin models the spectroscopic and
functional aspects of NiR. The reactivity, UV-Vis absorption and EPR spectra of the NiR-azurin models showed similarities
to that of native NiR but were less active. We have further examined the NiR activity of our models using the Griess
assay. Also, reduction and re-oxidation assays of the T1 center in the NiR-azurin models were determined and were
compared with variants with modified T1 copper center redox potentials. This yielded insights into the order of the reaction
between the reducing agent, protein, and the substrate in our models. Recent results will be discussed.
INOR 598
Synthetic models for nickel superoxide dismutase
Senaratnelage Nilmini K. senaratne1, [email protected], David M. Eichhorn 2. (1)
Chemistry, Wichita State University, Wichita, Kansas, United States (2) Wichita State Univ, Wichita, Kansas, United
States
Synthetic models for Nickel Superoxide Dismutase (NiSOD)
Ni-containing superoxide dismutase (NiSOD) is an important enzyme in detoxifying superoxide radical by catalyzing its
disproportionation to molecular oxygen and hydrogen peroxide through alternate oxidation and reduction of its catalytic Ni
center. The Ni center resides in an unusual N2S2 coordination geometry which consists of amide, amine and two thiolate
donors and this unique coordination sphere capable of stabilizing both Ni +2 and Ni+3 during enzyme catalysis.
In order to go for a better understanding about this stabilization we have been synthesizing model complexes for the
NiSOD active site with N2S2 coordination geometry. These complexes have amine/amide/bis(thiolate) and
amine/imine/bis(thiolate) coordination geometries. We have been able to synthesize a number of these complexes
containing a single tridentate NNS ligand and different types of thiolates.
All of the synthesized complexes have been characterized by single crystal x-ray crystallography, electronic spectroscopy
and cyclic voltammetry. The superoxide dismutase activity has been investigated by nitroblue tetrazolium assay. The
recent results will be reviewed and summarized
INOR 599
Job’s method and high resolution NMR studies of trinuclear bis(bis(O-ethyl-Lcysteinato)2Ni)2Ni2+
Ryan J. Dougherty, [email protected], Krish V. Krishnan, Melissa L. Golden. Chemistry, Fresno State,
Fresno, California, United States
Nickel containing metalloproteins have garnered much attention due to potential applications in the areas of drug
discovery1 and clean energy2. A number of N2S2Ni model complexes have been synthesized in order to gain a better
understanding of the active sites of some of these large proteins 3; however, a vast majority of these N2S2Ni model
complexes contain tetradentate ligand systems. Tetradentate ligand systems are often not as conformationally flexible as
ligands with a lower denticity, and they tend to stabilize only square planer geometries. Exploring the nickel coordination
of bidentate N,S ligands, such as l-cysteine ethylester (cysE), expands the data set of N2S2Ni coordination complexes and
the use of these N2S2Ni complexes as ligands.
Computational studies indicate that the trans-Ni(cysE)2 complex is slightly more stable than the cis-Ni(cysE)2 complex, but
in order to form the trinuclear [Ni(Ni(cysE)2)2]2+ complex, a Ni2+ ion must bridge 2 cis-Ni(cysE)2 complexes. In addition
N2S2Ni complexes using bidentate ligands are less stable than N2S2Ni with tetradentate ligands based on the chelate
effect. By using Job’s Method of Continuous Variation and high resolution NMR studies (HSQC,ROESY,
NOESY,TOCSY), the stability of the trinuclear [Ni(Ni(cysE) 2)2]2+ in solution is addressed. Job’s method confirms the
formation of the trinuclear nickel complex, and the high resolution NMR experiments provide evidence of additional
structural isomers in solution. The synthesis of the trinuclear complex was also confirmed by mass spectrometry, UV-Vis,
and elemental analysis.
1. Storr, T.; Thompson, K. H.; Orvig, C., Design of targeting ligands in medicinal inorganic chemistry. Chemical Society
Reviews 2006, 35 (6), 534-544.
2. Kim, D.-H.; Kim, M.-S., Hydrogenases for biological hydrogen production. Bioresource Technology 2011, 102 (18), 84238431.
3. (a) Osterloh, F.; Saak, W.; Pohl, S., Unidentate and Bidentate Binding of Nickel(II)
Complexes to an Fe4S4 Cluster via Bridging Thiolates: Synthesis, Crystal Structures, and Electrochemical Properties of
Model Compounds for the Active Sites of Nickel Containing CO Dehydrogenase/Acetyl-CoA Synthase. Journal of the
American Chemical Society 1997, 119 (24), 5648-5656; (b) Darensbourg, M. Y.; Lyon, E. J.; Smee, J. J., The bioorganometallic chemistry of active site iron in hydrogenases. Coordination Chemistry Reviews 2000, 206–207 (0), 533561.
INOR 600
Tuning mechanisms of action of Ru(II) polypyridyl complexes as anticancer targets by changing charge states
Yang Sun, [email protected], Mattew Dickerson, Brock Howerton, David Heidary,
Edith Glazer. Chemistry, University of Kentucky, Lexington, Kentucky, United States
Most current research on Ru(II) polypyridyl complexes as medicinal agents is focused on positively charged systems, in
part due to the availability of the cationic complexes via cellular uptake, and their binding affinities for specific targets. In a
recent study of Ru(II) polypyridyl complexes with positive and negative charges, we demonstrated that the negatively
charged complexes show both sufficient cellular uptake and biological activity as light-activated cytotoxic agents. While
positively charged complexes induce DNA damage and apoptosis in cancer cells, complexes with negative charges
induce apoptosis via mechanism(s) of action that do not include nucleic acids as the functional cellular targets. This study
reveals changing charge states leads to disparate biological activities and mechanisms of action in Ru(II) polypyridyl
complexes that are generally effective for light-mediated killing of cancer cells.
INOR 601
Selective recognition of G-quadruplex and thymine bulge DNA using bifunctional Zn(II) complexes
Kevin E. Siters1, [email protected], Stephanie A. Sander1, Jason Devlin2, Janet R.
Morrow1. (1) SUNY Buffalo, Buffalo, New York, United States (2) Lafayette College, Easton, Pennsylvania, United States
Recognition of DNA secondary structures, which contain non-canonical thymines, using coordination complexes will be
presented. A library of Zn(II) complexes that selectively bind to biologically relevant DNA secondary structures, including
G-quadruplexes and thymine bulges, was constructed. All of the complexes contain a cyclen
(1,4,7,10tetraazacyclododecane) macrocycle complexed with Zn(II) that forms a coordination bond with the deprotonated
imine nitrogen (N3) of thymine. The inclusion of an aromatic
pendent on the Zn(II)-cyclen complex improves binding through a π-π stacking interaction between the pendent and
thymine aromatic face. The aromatic pendents presented consist of either two- or three-fused aromatic rings that are
appended to the conserved Zn(II)-cyclen moiety. These pendents include: quinolinone (ZnMQC), quinoline (ZnCQC) and
anthraquinone (ZnATQ). This library of bifunctional complexes is used to investigate the contribution of the aromatic group
in binding to non-canonical thymines in different structural contexts, similar to those found in thymine-containing bulges
and G-quadruplex loops. Binding to duplex, bulged and G-quadruplex DNA was characterized using: surface plasmon
resonance (SPR; Fig.1A), isothermal calorimetery
(ITC; Fig.1B) and fluorescent spectroscopy. Favorable binding in the range of 14 μM to 22 μM to a thymine bulge was
observed for ZnATQ and ZnCQC. Selectivity for the thymine bulge was demonstrated with weak binding to a similar
cytosine bulge.
However, all complexes were shown to bind tightly (< 6.0 μM) to H-Telo using a 2:1 stoichiometry and a 3:1 stoichiometry
as shown for ZnATQ. The ZnMCC, ZnCQC and ZnATQ stabilize H-Telo by increasing the melting temperature by 9 ℃.
A) SPR sensorgram demonstrating binding of ZnMQC to a thymine bulge in 100 mM NaCl, 20 mM HEPES (pH 7.5) and 0.05%
Tween 20. B) ITC plot showing ZnCQC binding to H-Telo in 100 mM KCl, 20 mM HEPES (pH 7.5).
INOR 602
Evaluation of the binding of Zn(II) complexes to G-quadruplexes using a PCRstop assay
Melissa Shively1, [email protected], Mariya Shapovalova1,
[email protected], Matthew Fountain 1, Janet R. Morrow2, Kevin E. Siters3. (1) Chemistry and Biochemistry,
Fredonia State University of New York, Fredonia, New
York, United States (2) SUNY Buffalo, Buffalo, New York, United States (3) University at Buffalo, Buffalo, New York,
United States
G-quadruplexes play an important role in the regulation of gene transcription, DNA replication, and stabilization of
chromosome ends, making them potential therapeutic targets. To date, there have been a number of reported compounds
that bind Gquadruplexes, with the majority of these targeting the planar G-tetrads. The design of compounds that target
specific sequence and structural features of quadruplex loops could provide a means of selectively binding to different Gquadruplex structures. A series of bifunctional thymine recognition agents consisting of a Zn(II) cyclen macrocyclic motif
and an aromatic pendant group which selectively binds thymines in the lateral loops of G-quadruplexes were studied. A
PCR stop assay was used to determine the ability of these complexes to stabilize different G-quadruplexes and prevent
Taq polymerase from extending the DNA sequence beyond the quadruplex. Our results show that different aromatic
pendant groups exhibit a range of IC50 values for the H-Telo quadruplex. For example, Zn(II) cyclen with a dansyl pendent
group exhibited an IC50 of 3±1, while Zn(II) cyclen with an acridine pendant group exhibited an IC 50 > 20 uM. This study
shows that the aromatic ring attached to the Zn(II) cyclen can greatly influence its binding to thymine and the stabilization
of the G-quadruplex.
INOR 603
Determining titanium (IV) transport for its potential use by humans
Talia M. Planas-Fontanez, [email protected], Steven Conklin Lopez,
Aleannette Lopez-Cubero, Arthur D. Tinoco. Chemistry, University of Puerto Rico Rio Piedras, San Juan, Puerto Rico,
United States
Metals play an essential role in numerous biological functions and process. Commonly studied metal ions include iron,
copper, zinc and calcium which take part in enzymatic process, the nervous system and protein transport. Titanium, a
universal metal not know to be essential in humans, is a bioactive metal ion and an excellent promising anticancer drug
candidate. In humans, this metal is present in small but not insignificant concentrations, and can be transported from the
bloodstream into the cell by binding to a protein. This metal is found present in a wide variety of biomaterials, as dental
implants or artificial joints, and food. In this way titanium has access to our system, even though the method of entry into
cells is still uncertain as is the acquisition by cells. The favored hypothesis is that titanium(IV) has the ability to bind to
serum transferrin, which transports the metal ion to the cells. The binding of Ti(IV) by transferrin induces conformational
changes that may facilitate binding to the transferrin receptor for intracellular transport. To elucidate this mechanism and
determine the coordination of Ti(IV), we realized binding and computational studies to determine the protein residues that
were bound to the metal center of the active site. The Ti(IV) is found to coordinate to the tyrosine residues of the metal
binding site but not the histidine nor aspartate. We also performed competitive studies with albumin to determine the
selectivity of Ti(IV) binding to transferrin. In binding metals, small molecules help to maintain a homeostasis of soluble
metals, in addition to keeping them in a bioavailable form. The data suggests that citrate, a small molecule metabolically
important, bind Ti(IV) in the blood serum. Citrate plays an important role in the metal binding to the protein by serving as a
synergistic anion and helping to transport the metal ion into cells. These findings provide us with insight into alternative
ways in which metals can be bound and transported by transferrin.
INOR 604
Non-covalent interactions of a Ru-Rh supramolecular complex with DNA and their effect on covalent modification
of the biomolecule
Jose A. Rodriguez Corrales1, [email protected], Karen S. Brewer2. (1) Chemistry,
Virginia Tech, Blacksburg, Virginia, United States (2) Virginia Polytech Inst, Blacksburg, Virginia, United States
Deoxyribonucleic acid (DNA) lies in the core of cancer and is an attractive target for chemotherapy. Interaction of drugs
with DNA is widely used to screen for their biological activity. Ruthenium and rhodium octahedral complexes have shown
non-covalent and covalent modification of of DNA.1,2 In particular, Ru-Rh bimetallic architectures, with the general
structure [(TL)2Ru(BL)Rh(TL)Cl2]3+ (TL=terminal ligand, BL=bridging ligand), have shown oxygen-independent cleavage
and binding via visible light activation.3 Nevertheless, non-covalent interactions of these supramolecular complexes with
DNA remain unexplored. Binding affinity of a Ru-Rh bimetallic to DNA was studied under different ionic strengths and in
the presence of competitive binders, in order to understand the impact of non-covalent interactions on covalent
modification of this biomolecule. Electronic absorption and emission spectroscopy indicate contribution of different noncovalent binding modes. Moreover, non-covalent interactions stablished between the complex and DNA during photolysis
impact the extend of binding and cleavage, as evidenced through gel electrophoresis. Acknowledgement is made to VT
ICTAS 119552 and the National Science Foundation 478898 for their generous funding.
1. Pyle, A. M.; Rehmann, J. P.; Meshoyrer, R.; Kumar, C. V.; Turro, N. J.; Barton, J. K., Mixed-ligand complexes of
ruthenium(II): factors governing binding to DNA. Journal of the American Chemical Society 1989, 111 (8), 3051-3058.
2. Erkkila, K. E.; Odom, D. T.; Barton, J. K., Recognition and Reaction of
Metallointercalators with DNA. Chemical Reviews 1999, 99 (9), 2777-2796.
3. Wang, J.; Zigler, D. F.; Hurst, N.; Othee, H.; Winkel, B. S. J.; Brewer, K. J., A new, bioactive structural motif: Visible light
induced DNA photobinding and oxygen independent photocleavage by RuII, RhIII bimetallics. Journal of Inorganic
Biochemistry 2012, 116 (0), 135-139.
INOR 605
Light-activated drug release using heterobimetallic ruthenium and cobalt complexes
Rachel Whitman, [email protected], Claudia Turro. Chemistry and Biochemistry,
The Ohio State University, Columbus, Ohio, United States
Photochemotherapy (PCT) is an attractive potential cancer treatment that involves photoinduced ligand exchange of a
monodentate ligand(drug) bound to a transition metal. Known Heterobimetallic complexes consisting of a ruthenium(II)
polypyridyl light absorber bound through a bridging ligand to a cobalt(III) metal center have been shown to undergo ligand
exchange. Visible light absorption by the ruthenium center results in electron transfer, effectively reducing the cobalt
center to cobalt(II) . While the cobalt(III) center is inert, the ligands on the cobalt(II) center become labile, leading to
photoexchange. Discussed herein is the synthesis and characterization of a
Ru(II),Co(III) bimetallic complex [(bpy)2Ru(bpm)Co(tpy)L](PF6)5 (bpy = 2,2ʹ-bipyridine; bpm = 2,2ʹ-bipyrimidine; tpy =
2,2ʹ:2ʺ,6ʹ-terpyridine, L = pyridyl-, amine- or nitrilecontaining drug). Photochemical, photophysical, and electrochemical
studies are done to investigate the complex as a potential PCT agent.
INOR 606
Synthesis, characterization, and reactivity of pyridazine-oxime metal complexes
Siddieg O. Elsiddieg, [email protected], Frank R. Fronczek, Andrew W.
Maverick. Chemistry, Louisiana State University, Baton Rouge, Louisiana, United States
Pyridazine-oxime (pdzox)-based metal complexes were designed to coordinate in a trans-planar fashion around metal
ions, reinforced by hydrogen bonding, as shown in Figure 1. These two features are important for the production of more
predictable metallosupramolecular constructs that can be used for a variety of useful applications. Three new pyridazineoxime complexes with Co(III), Cu(II), and Ni(II) were successfully prepared. Single crystals of these complexes were
obtained, and their structures match well with the design. Substitution reactions of these metal complexes and their redox
chemistry were investigated.
Figure 1. Pdzox metal complexes: M= Co(III), Cu(II), Ni(II); L= weakly coordinated ligand
INOR 607
“Super Bulky” guanidinates for the support of low-coordinate metal complexes Leonel Griego,
[email protected], Arnab K. Maity, Skye Fortier, Alejandro J. Metta-Magana. Chemistry, University of Texas at El
Paso, El Paso, Texas, United
States
The high steric and electronic tunability of guanidinates provides for a highly versatile class of ligands, a characteristic we
have exploited in pursuit of novel ligand sets. We have recently reported the synthesis of the “super bulky” guanidinate
[RC(N*Ar)2]- (R = tBu2C=N, Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl) (1) (MM > 1100 g/mol), a highly encumbering
ligand with surprising flexibility. In order to better understand the coordination properties of 1, especially its ability to
stabilize metals in unusually low coordination environments, we have begun to explore its chemistry with electron-poor
metals such as titanium. Synthetic efforts towards metal complexes of 1 and their full structural analyses will be provided.
INOR 608
Synthesis and characterization of a new guanidinate-guanidinate ligand featuring an imidazolin-2-iminate
backbone
Brian Barraza, [email protected], Jeffrey Lu, Rolando Aguilar, Arnab Maity, Skye Fortier, Alejandro J. MettaMagana. Chemistry, UTEP, El Paso, Texas, United States
Imidazolin-2-iminates [ImRN]- are a new class of monoanionic imine ligands, built upon
an N-heterocyclic carbene core, which exhibit excellent σ and π-donor abilities. Our laboratory has been exploring the
electronic effects of imine substituents on guanidinate ligands, including those functionalized by ImRN groups. Addition of
[ImRN]- to bis(2,6diisopropylphenyl)carbodiimide cleanly affords [(ImRN)C(dipp)2]- (1) which can be formally considered
as a “guanidine-guanidinate.” We anticipate the nitrogen-rich framework of 1 will display exceptional electron donating
abilities when coordinated to a metal. Our studies to understand its structural and electronic properties, including its
coordination chemistry with 3d metals, will be presented.
INOR 609
Reactivity of group 11 formamidinate complexes
Andrew Lane3, [email protected], Justin R. Walensky2, William E.
Antholine1. (1) Med Colg of Wisconsin, Milwaukee, Wisconsin, United States (2)
Chemistry, University of Missouri, Columbia, Missouri, United States (3) University of
Missouri-Columbia, Chesterfield, Missouri, United States
Group 11 transition metals are important to society and are used by most on a daily basis. The three formamidinate
ligands being examined are 2,6-dimethylphenyl, 2,6diisopropylphenyl, and 2,4,6-trimethylphenyl. The synthesis of these
dinuclear Cu(I) complexes as well as their redox and insertion chemistry with I2 and CS2, respectively, to afford di-, tri-,
tetra-, and hexanuclear clusters will be presented. The cluster size is found to be dictated based on the ligand’s steric
properties. Using EPR spectroscopy and DFT calculations on the iodine oxidized products we show different electronic
structures based on the formamidinate but all contain mixed-valent, Cu(I,II) products.
INOR 610
Vanadium(V) catecholates: Correlating redox potential with
51
V NMR chemical shifts
Jordan Koehn1, [email protected], Pabitra Chatterjee1, Andrew
Waterhouse3, Taylor Lucia1, Tatyana E. Polenova2, Michael D. Johnson3, Debbie C.
Crans1. (1) Chemistry, Colorado State University, Fort Collins, Colorado, United States
(2) Dept of Chemistry Biochemistry, University of Delaware, Newark, Delaware, United
States (3) Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico, United States
In the following, we demonstrate the correlation of 51V NMR chemical shifts with redox potentials of a series of noninnocent vanadium(V) catechol complexes. Several of the complexes synthesized herein were characterized previously
by both solid state and solution 51V NMR spectroscopy. An observed linear correlation between solution and solid state
51V NMR chemical shifts is consistent with the solution structure being similar to that observed in the solid state. Due to
the fact that the solid state 51V NMR chemical shift describes the electronic structure of the vanadium complexes, the
potential exists for the use of the 51V NMR chemical shift to characterize the properties of these compounds. The
vanadium(V) catechol complexes described in this study are in fact redox active and the chemical shifts fall outside the
normal populated isotropic 51V NMR chemical shift range (-300 to -700 ppm) as anticipated for complexes with noninnocent ligands. These complexes are therefore well suited for examination of the hypothesis that the 51V NMR chemical
shifts of the vanadium(V) catechol complexes correlate with the redox potential of these complexes. Cyclic Voltammetry
studies were performed to
calculate the redox potential (E˳) of each complex in solution. The 51V NMR chemical shifts were then plotted as a function
of the redox potential. A linear correlation of 51V NMR isotropic chemical shift and redox potential is observed for the three
known and three novel VO(HSHED) compounds containing a non-innocent catechol ligand. These studies demonstrate
that substitution of the non-innocent catechol ligand with electrondonating groups results in a downfield shift in 51V NMR
spectra and a decrease in redox potential. In contrast, substitution of the catechol ligand with electron-withdrawing groups
results in an upfield shift in 51V NMR and an increase in redox potential. Combined, these studies demonstrate for the first
time that 51V NMR chemical shifts correlate with the redox potential of the vanadium(V) catecholates and could potentially
be a useful method for characterization of the redox properties of these compounds.
INOR 611
Octahedral to trigonal prismatic distortion in Ruthenium and Osmium bishomoleptic complexes of a noninnocent
ligand
Jacqueline Cipressi, [email protected], Seth N. Brown, [email protected]. Department of Chemistry and
Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States
Ruthenium and osmium bis-homoleptic complexes of two noninnocent ligands, ONO, N(3,5-di-tert-butyl-2-oxyphenyl)-3,5di-tert-butylquinoneimine, and DOPO, 2,4,6,8-tetratert-butyl-1-oxo-1H-phenoxazin-9-olate, were synthesized by reacting
di-μ-chlorobis[(pcymene)chloroM(II) (M = Os and Ru) with Pb(L Q)2 (ONO and DOPO). The ligands’ consecutive 5membered chelate rings with all ligand atoms sp2-hybridized encourage it to adopt a meridional geometry in an
octahedron. The complexes containing the DOPO ligand were found to be octahedral, whereas the complexes containing
the ONO ligand show distortions from the expected octahedral geometry. Ruthenium and osmium bis(ONO) distort
towards trigonal prismatic geometries in order to minimize aryloxide-tometal π* interactions due to donation from the
second-highest ligand orbital to the metal, an orbital that is often neglected in π-donor ligands. The degree of distortion
directly correlates with the degree of reduction of the redox active ligand. As the metalligand π bonding orbitals shift from
ligand-centered to metal-centered, and hence the ligand becomes more oxidized, these orbitals become more σantibonding in the trigonal prism and restore the geometric preference to octahedral.
INOR 612
Recent developments in cyano-substituted polypyrazolylborates chemistry
Lava Raj Kadel, [email protected], David M. Eichhorn. Department of Chemistry,
Wichita State University, Wichita, Kansas, United States
For several years, our research group has been developing cyano-substituted polypyrazolylborate ligands, also called
cyanoscorpionate ligands. In previous work, we have demonstrated that cyanoscorpionate ligands have the ability to
facilitate the synthesis of polymeric materials via coordination to both the cyano and the pyrazole N atoms. Due to the
electron-withdrawing nature of the cyano substituent, the cyanoscorpionate ligand also has the potential to alter the
electronic structure and properties of the coordinated metal. In this work we report our current progress in this area, which
includes new complexes with metal ions such as Co, Ni, Mn, Fe and Mo.
INOR 613
Synthesis, structural and spectroscopic studies of six-coordinate iron and cobalt phosphasalen complexes
Joseph M. Fritsch2, [email protected], Clare M. Bakewell1, Andrew J.
White1, Charlotte K. Williams1. (1) Imperial College London, London, United Kingdom
(2) Chemistry, Pepperdine University, Newbury Park, California, United States
The recently developed iminophosphorane ligand (phosphasalen) with an ethylene diamine bridge mimics the well-studied
salen ligand in coordination geometry around a metal center.1 Replacing the ethylene diamine linker with a diethylene
triamine bridge yielded a pentacoordinate ligand2 which when combined with potassium hexamethyl silyl amide and a
metal source yielded the corresponding metal complexes. An iron(III) chloride complex was synthesized and
characterized spectroscopically and crystallographically which showed an octahedral coordination geometry around the
iron center. An air sensitive cobalt(II) complex was prepared through reaction with cobalt(II) acetate and the deprotonated
phosphasalen ligand. The cobalt(II) complex was oxidized with iodine yielding a cobalt(III) iodide complex which was
characterized with 1H and 31P NMR and absorbance spectroscopy.
1
2
T.-P.-A. Cao, A. Buchard, X. F. Le Goff, A. Auffrant and C. K. Williams, Inorg. Chem., 2012, 51, 2157.
C. Bakewell, T.-P.-A. Cao, N. Long, X. F. Le Goff, A. Auffrant and C. K. Williams, J. Am. Chem. Soc., 2012, 134,
20577.
INOR 614
Electron transfer between metal and ligand in chromium complexes with tetrazine-containing pincer ligand
Alexander V. Polezhaev1, [email protected], Chun-Hsing Chen3, Nicholas A.
Maciulis1, Kenneth G. Caulton2. (1) Chemistry, Indiana University, Bloomington,
Bloomington, Indiana, United States (2) Indiana University, Bloomington, Indiana, United States
Polypyridyl ligands have been used since the 1950’s in coordination chemistry and catalysis, but only in the past 15 years
has their reduction chemistry been investigated. Now nitrogen containing heterocycles became the most common building
blocks for developing transition metal catalyst supported with redox-active ligands. It has been shown previously that 2,6bis(6-methyl-1,2,4,5-tetrazinyl)pyridine (btzp) is easier to reduce than 2,2′:6′,2′′-terpyridine by 1.3V, and the reducing
equivalents go exclusively into the tetrazine moieties that makes btzp most electron withdrawing tris-imine donor ligand
yet developed. Oxidation state of metal in the complex often plays critical role for activity in catalytic process that is why
we are interested in synthesis on whole line btzpM(X)n complexes, where M is metal in oxidation state from 0 to highest
possible. The synthesis of chromium complexes with different Cr oxidation states and analysis of ligand oxidation potency
will be presented. The reactivity toward electron transfer from btzpCr species to substrate, such as water will be
discussed.
INOR 615
Pyrazolate and polypyrazoleborate complexes of platinum and palladium
Alan Oberley1,3, [email protected], David M. Eichhorn2. (1) Chemistry, Newman University, Clearwater, Kansas,
United States (2) Wichita State Univ, Wichita, Kansas, United States (3) Chemistry, Wichita State University, Wichita,
Kansas, United States
Polypyrazolylborate ligands with cyano substituents have been developed and are being studied as precursors to
magnetic and conductive polymers. This research focuses specifically on the palladium and platinum complexes of the
cyano substituted pyrazole and polypyrazoleborate ligands. A new tripalladium complex with cyano substituted pyrazole is
studied, along with related compounds. Recent work will be included.
INOR 616
Chemistry of copper and nickel pyridyltriazole complexes
Takia M. Wheat, [email protected], Uttam R. Pokharel, Frank R. Fronczek, Andrew W.
Maverick. Chemistry, Louisiana State University, Baton Rouge, Louisiana, United States
We have designed metal-organic supramolecules of copper(II) and nickel(II) using complexation of “click” ligands, and
investigated their properties on capturing small molecular guests. A dimeric complex, [Cu 2(5-MeO-m-xpt)2(H2O)2]4+, forms
from tetradentate 5-methoxy-m-xylylenebis(pyridyltriazole), (5-MeO-m-xpt). This metallamacrocycle holds a benzene
molecule as a guest inside its cavity in the solid state. Reduction of the complex using sodium ascorbate gives a Cu(I)
dimer which, in turn, can reduce CO2 to oxalate giving an oxalate-bridged binuclear complex, [Cu2(5MeO-m-xpt)2(μC2O4)]2+. With nickel (II), complexation of benzylpryidyltriazole, (bpt) gives [Ni(bpt) 2(OH2)]2+ with the desired trans-planar
arrangement of two pyridyltriazole chelating units around the metal center. We are currently working on extending the
complexation to design binuclear complexes of Ni(II), such as [Ni2(5-MeO-mxpt)2(OH2)]4+. The structural analysis and
spectroscopic properties of the complexes will be discussed.
INOR 617
Synthesis and characterization of bis-bipyridyl ruthenium(II) complexes with high nitrogen content tetrazole
aromatic ligands
Ronald R. Ruminski, [email protected], Michael A. Hiskey, Ratna Malkan, Brandon Powell. Chem Dept, Univ of
Colorado, Colorado Springs, Colorado, United States
The synthesis of [(bpy)2Ru(bt)] and [(bpy)2Ru(bta)] where bt-2 = bi-tetrazole; bta-2 = bitetrazoleamine is described, and
structures are shown below. The molecules are largely insoluble in most solvents including acetonitrile, water and
alcohols. Both complexes are slightly soluble in DMF and DMSO, and the absorption, emission and NMR data in DMSO
will be presented.
INOR 618
Novel synthesis of a dinuclear ruthenium(II) polypyridyl complex based on a polymeric carbonyl complex
Latisha M. Puckett2, [email protected], Bill Durham1. (1) Univ of Arkansas,
Fayetteville, Arkansas, United States (2) University of Arkansas at Fayetteville, Winslow, Arkansas, United States
There are several methods for the synthesis of dinuclear ruthenium(II) polypyridyl complexes. However, most methods do
not provide pure dimeric complexes suitable for photochemical studies without chromatographic separations. Many of the
previously used syntheses are based on the coupling of two monomeric complexes to form the dimeric complex. This
results in a mixture of monomeric and dimeric complexes. The present work focuses on the development of a novel
synthetic method utilizing the polymeric carbonyl complex [Ru(CO) 2Cl2]n and 5,5’-Bi-1,10-phenanthroline to produce a
ruthenium dimeric complex. This approach provides good yields with a range of polypyridine ligands. Interestingly the
synthetic scheme works poorly with others types of ligands such as noncyclic amines and nitriles.
INOR 619
Synthesis and crystallographic study of zinc and mercury complexes with a three-N-donor asymmetric pyridine–
amine ligand 2,9-di(pyridin-2-yl)-1,3,6triazabicyclo[4.2.1]nonane
Mohammad Hakimi, [email protected]. Department of Chemistry, Payame Noor
University, Mashhad, Iran (the Islamic Republic of)
A series of an oily Multi-N-Donor ligands including 2-((2-((pyridin-2ylmethylene)amino)ethyl)amino)ethanol (PMAE), 2-(2-(pyridin-2-yl)oxazolidin-3-yl)-N(pyridin-2-ylmethylene)ethanamine
(POPME) and 2,9-di(pyridin-2-yl)-1,3,6triazabicyclo[4.2.1]nonane (PACN) was synthesized in one-pot asymmetric
reaction between 2-(2-amino-ethylamino)ethanol and pyridine-2-carbaldehyde in microwave. In this work, synthesis
[Zn(PACN)Br2] (1), and [Hg(PACN)Cl2] (2) complexes which are characterized by elemental analysis, FT-IR and Raman
spectroscopy and single-crystal X-ray diffraction. In the crystal structures of 1 and 2, the chiral PACN acts as N3-donor
ligand and forms distorted square pyramidal geometry around the central atoms assisted by coordination of two halide
ions. However the crystals contain a racemic mixture of R,R,S and S,S,R isomers in alternate layers. Addition to the
hydrogen bonds, the network is more stabilized by π···π stacking interactions between parallel aromatic rings.
Keywords: Synthesis; Nonane; Zinc bromide; Mercury chloride; X-Ray crystal structure INOR 620
Synthesis and characterization of [M(tacn)(dppz)(solvent)] n+ complexes of Ru, Rh, and Ir: New DNA
metallointercalators possessing modifiable groups
Haylie L. Hancock, Minh Pham, Gursu Culcu, Steven C. Haefner,
[email protected]. Chemical Sciences, Bridgewater State University, Bridgewater, Massachusetts, United States
Our group is interested in the development of new metal based complexes capable of binding DNA through intercalation.
These DNA metallointercalators have the potential to act as small molecule DNA probes, inhibit DNA binding proteins,
and photochemically cleave or excise DNA lesions. We are currently focusing on the use of 1,4,7triazacyclononane (tacn)
as a supporting ligand for metallointercalators possessing an octahedral coordination geometry. This capping tridentate
ligand combined with a bidentate intercalating ligand such as dppz (dppz = dipyrido[3,2-a:2',3'-c]phenazine) provides for
an open coordination site that can be modified to alter the DNA binding strength and specificity. To this end we have
synthesized triflate salts of
[Ru(tacn)(dppz)(dmso)]2+ and [M(tacn)(dppz)(H2O)]3+ (M = Rh, Ir). These complexes were prepared by reaction of the
hydrated metal trichlorides, MCl3 · xH2O (M = Ru, Rh, Ir), with tacn to form mixed tacn/chloride complexes. The chloride
ligands were then removed and replaced with dppz by treatment with silver triflate followed by reaction with dppz. Details
of the synthesis, spectroscopic characterization, and crystal structures of these new complexes will be presented.
INOR 621
Combined experimental and theoretical investigation of electronic structures and anion sensing aspects of
OsII(bpy)2(HL2-) AND [{OsII(bpy)2}2(μ-HL2-)]2+
Ankita Das, [email protected]. Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India
The application potential of mixed valent complexes in information transfer and optical devices has initiated the
development of newer molecular frameworks with well defined electrochemical and optical features. [1] In this context the
osmium chemistry of the structurally characterized[2] potential non-innocent ligand framework 5-(1Hbenzo[d]imidazol-2-yl)1H-imidazole-4-carboxylic acid (H3L) has been explored in combination with p-accepting bpy (=2,2/-bipyridine) as ancillary
ligands. (Scheme 1)
The electronic aspects of bridging and ancillary functionalities towards the bridge mediated intermetallic electronic
coupling process in [2](ClO4)2 has been investigated via experimental (spectroelectrochemistry, EPR) techniques in
combination with DFT/TD-DFT calculations. Further, the effectiveness of both the complexes to function as suitable
receptors for the selective recognition of anion(s) has been scrutinized.
REFERENCES
[1] (a) D’Alessandro, D. M.; Keene, F. R. Chem. Rev. 2006, 106, 2270; (b) Kaim, W.;
Lahiri, G. K. Angew. Chem. Int. Ed. 2007, 46, 1778; (c) LeClair, G.; Wang, Z. Y. J. Solid State Electrochem. 2009, 13, 365
[2] (a) Das, A; Agarwala, H; Ghosh, P; Mondal, S; Mobin, S. M.; Lahiri, G. K. Dalton
Trans. 2014, XX, 000; (b) Kundu, T; Chowdhury, A. D.; De, D.; Mobin, S. M.; Dutta, A; Lahiri, G. K. Dalton Trans. 2012,
41,4484; (c) Kundu, T; Mobin, S. M.; Lahiri, G. K. Dalton Trans. 2010, 39, 4232.
Scheme 1 . Representation of complexes
INOR 622
Dehydrohalogenation as an effective route to unsaturated bimetallic and monometallic systems featuring a
proton-responsive pincer ligand
Brian Cook1, [email protected], Chun-Hsing Chen4, Maren Pink5, Richard L. Lord2,
Kenneth G. Caulton3. (1) Chemistry, Indiana University, Bloomington, Indiana, United
States (2) Department of Chemistry, Grand Valley State University, Allendale, Michigan, United States (3) Indiana
University, Bloomington, Indiana, United States
Generating open coordination sites at metal centers is of vital importance for successful transition metal catalysts and
activation of small molecules. One method is dehydrohalogenation, implemented when a complex features acidic protons
and halide ligands. Most commonly, this methodology is implemented during metallation of PCP type pincer ligands with
IrCl3 to generate (PCP)IrCl2; the acidic proton on the aryl carbon and Cl are both removed. Recently, we have been
interested in
bispyrazolylpyridine-type pincer ligands that are proton-responsive and recently shown to be also redox active.
Specifically, bis(5-tertbutyl-2H-pyrazol-3-yl)pyridine (LH2) complexes of the general formula (LH2)MCl2 (M=Co, Fe) have
been synthesized and fully characterized. These complexes react with LiN(SiMe3)2 to generate “-ate” complexes of the
form LiM2L2Cl, resulting from one bridging Cl and pyrazolate ligand with crystallographic M..M distances of 3.45 and 3.72
Å for Co and Fe respectively. Excess diprotic acid and base lead to complex aggregates that will also be presented. If
NaH is employed, reduction of CoII to CoI occurs in addition to dehydrohalogenation resulting in a rare square planar Co I
featuring a pincer ligand. The “-ate” dimers can be dissociated with 2 equivalents of Lewis base, in particular PEt3 to
generate the S=1/2 square pyramidal (L)Co(PEt3)2. In contrast, the tolerance of Lewis bases for Fe is much more
stringent, needing a much stronger donor in the form of 4-dimethylaminopyridine (DMAP). The repercussions of
thermodynamically favored geometry, coordination number, and spin state will be discussed. The oxidation (Co) and
reduction (Fe and Co) chemistry of the resulting monometallic complexes will also be presented, with focus towards
activation of small molecules.
INOR 623
Low-valent organometallics incorporating the 2,2'-biazulenyl motif
Mason D. Hart, [email protected], David M. McGinnis, Brad M. Neal, Mikhail V.
Barybin. Chemistry, University of Kansas, Lawrence, Kansas, United States
In this presentation, efficient syntheses of the 2,2’-biazulenyl scaffold involving SuzukiMiyaura coupling of monoazulenic
precursors will be presented. These routes constitute convenient alternatives to the highly sensitive Ullmann coupling
procedure for the preparation of 2,2’-biazulenyl. The 2,2'-biazulenyl hydrocarbon undergoes completely regioselective
amination to afford 6-amino-2,2’-biazulenyl derivative, which was structurally characterized (see Figure below).
Formylation of this nonbenzenoid arylamine, followed by dehydration of the corresponding formamide, gives 6isocyano2,2’-biazulenyl ligand in an up to 70% overall yield. Electronic interactions of the 2,2’biazulenyl motif with lowvalent transition metal ions and metal surfaces mediated by the isocyano junction will be discussed.
INOR 624
Six-coordinate 16-electron complexes of tungsten (II): Synthesis, electrochemistry, and density functional theory
Angelique F. Greene3, [email protected], Samuel Dahlhauser4, Joel T. Mague1,
Jim P. Donahue2. (1) Tulane Univ, New Orleans, Louisiana, United States (2) Tulane
University, New Orleans, Louisiana, United States (3) Chemistry, Tulane University,
Metairie, Louisiana, United States (4) Chemistry, National Cancer Institute (NCI), Rockville, Maryland, United States
Six-coordinate 16-electron d4 complexes of group (VI), particularly tungsten, have been found to assume configurations
that span from the fully octahedral to the fully trigonal prismatic, with some exhibiting different degrees of distortion
between the two geometries. Six-coordinate d4 complexes of tungsten are quite rare in the literature and are also highly
reactive due to tungsten's propensity to form 7-coordinate complexes, which would allow for a more stable 18-electron
configuration. Here we report the synthesis of six-coordinate 16-electron d4 complexes of type [W(S-S)(CO)2(L)x] (S-S:
bdt2-=benzene-1,2-dithiolate; mnt2-= maleonitrile-2,3-ditholate, Lx=1: phen=1,10phenanthroline; bpm *=bis(3,5-dimethyl-1pyrazolyl)methane; enH2Et2=N,Ndiethylethylenediamine, Lx=2: py=pyridine). Also, we present a more accesible route to the
known complex [W(tdt-2)(CO)2(phen)] (tdt2-=toluene-3,4-dithiolate) and a reworking of the synthesis of 18-electron 7coordinate complexes of type [WI2(CO)3(L)x] (Lx=1=phen, bpm*,Lx=2=py). All complexes have been characterized
spectroscopically and electrochemically as well as having their geometries and electronic structures scrutinized by
employing Density Functional Theory (DFT).
INOR 625
Structural trends for triple-decker organometallic sandwiches formed by highly charged π-bowls with mixed
alkali metal cores: Li/K vs. Li/Rb
Sarah N. Spisak1, Alexander S. Filatov1, Alexander V. Zabula2, Andrey Y. Rogachev3, Marina A. Petrukhina1,
[email protected]. (1) Department of Chemistry,
University at Albany, SUNY, Albany, New York, United States (2) Department of
Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States (3)
Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, Illinois, United States
Self-assembly processes of highly reduced corannulene generated by the chemical reduction with a binary combination of
alkali metals, namely Li/K and Li/Rb, have been investigated by a synergistic use of NMR spectroscopy, X-ray
crystallography and DFT calculations. The formation of several unique mixed metal core sandwich-type products based
on tetrareduced corannulene, C20H104-, has been revealed. According to the Xray diffraction studies, these remarkable
triple-decker supramolecular aggregates illustrate a record ability of bowl-shaped and highly charged corannulene to
provide all its sites, five benzene rings fused to a central five-membered ring, for binding of six alkali metal ions. The
previously unseen engagement of the hub-site of C20H104− in lithium binding is accompanied by unprecedented shifts up to
–25 ppm in 7Li NMR spectra. The theoretical analysis of these unique systems now provides an explanation for such
record shifts for the centrally located lithium ion. Furthermore, the analysis of Xray diffraction data allows us to correlate
the NMR shifts with structures of the sandwich-type assemblies and to show that the 7Li NMR signal from the internal
lithium ion could be used for qualitative evaluation of the interaction strength between the charged bowls in organometallic
supramolecular aggregates.
INOR 626
Novel, multizonal, crystalline composite based upon self-assembled, helical coordination polymers and
exhibiting seven primary zones in the solid state
S. R. Seidel1, [email protected], Richard Wilkens2. (1) University of WisconsinWaukesha, Waukesha, Wisconsin,
United States (2) Dowling College , Oakdale, New York, United States
Presented herein is a novel, multi-zonal crystalline composite based upon coordination polymers. The zones that
comprise the resultant system are of self-assembled, essentially-isostructural helices, which, themselves, are made up of
4,4'-dithiodipyridine (aldrithiol-4) donor subunits linking M(II) hexafluoroacetylacetonate acceptor units. The constituent
polymers adopt a helical shape that derives from the 90° cis- nature of the ditopic acceptors and also the 90° C-S-S-C
dihedral angle of the ditopic donor. When copper is the metal ("M"), green results. When zinc is the metal ("M"), the result
is colorless. This work presents composites exhibiting seven apparent, primary zoning events. Included will be
microscopic photography of the crystals.
INOR 627
Synthesis of new dithiolene-type ligands
Elaine Haas3, [email protected], Jim P. Donahue2, Joel T. Mague1. (1) Tulane
Univ, New Orleans, Louisiana, United States (2) Tulane University, New Orleans,
Louisiana, United States (3) Chemistry, Tulane University, New Orleans, Louisiana, United States
In an effort to create new, more efficient and more general synthetic methods for dithiolene-type ligands, several new
variants of this ligand-type are being investigated. All are comprised of a 1,2-alkene-o-xylyldithiolate backbone and as
such exhibit steric hindrance that has yet to be explored in this context. While some dithiolene ligands can be synthesized
by reacting a metal sulfido compound with an alkyne or other hydrocarbon, the ligands investigated here belong to a
separate group which are produced free of a metal center. An alkenedithiolate dianion is used to subject a select
halogenated ethylene to nucleophilic attack, in this case producing the desired o-xylyl protected dithiolene. It is of
particular interest to investigate how these new ligand-types will behave when coordinated to representative metals.
Compounds of this type - including other dichalcogenolenes (dioxolenes and diselenolenes) - are of interest namely due
to their redox non-innocent behavior. This redox behavior is the crux of many potential applications, including use as
conducting materials, sensing devices, and catalysts for the generation of hydrogen gas. The first new compound of the
series to be prepared was (Z)-1,6-dihydrobenzo[f][1,4]dithiocine, which was characterized by 1H and 13C NMR, elemental
analysis, and identified via X-Ray structure determination.
INOR 628
Cd(II) complexation with 1,1-dithiolate and nitrogen donors: Synthesis, luminescence, crystal structure and
antifungal activity
Arijit Das, [email protected]. CHEMISTRY, RAMTHAKUR COLLEGE,
AGARTALA, WEST TRIPURA, TRIPURA, INDIA, Tripura, India
A new luminescent mixed ligand complex of Cd(II) with 1,1-dicyanoethylene- 2,2dithiolate [ i-MNT2- = {S2C:C(CN)2}2- ] as a
primary, 1,3-diaminopropane (tn) and 4methyl pyridine (γ-picoline) as secondary ligands has been synthesized and
characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single crystal X-ray diffraction
analysis reveals that the Cadmium (II) complex is five coordinated polymeric in nature. Biological screening effects in vitro
of the synthesized mixed ligand complex has been tested against five fungi Synchitrium endobioticum, Pyricularia oryzae,
Helminthosporium oryzae, Candida albicans (ATCC10231), Trichophyton mentagrophytes by the disc diffusion method. A
comparative study of inhibition zone values of the primary ligand K 2i-MNT.H2O and its synthesized complex 1 indicates
that the complex exhibits fungistatic antifungal activity whereas K 2i-MNT.H2O became silent on Synchitrium endobioticum,
Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), Trichophyton mentagrophytes. Keywords:
Mixed ligand complex, Cd(II), 1,1-dithiolate, Nitrogen donor, X-ray diffraction, luminescence and antifungal activity study.
INOR 629
Reversible addition of alcohols across C=N bonds of a N 4 Schiff base ligand coordinated to copper (II)
Wuyu Zhang2, [email protected], Hanlin Nie1, Mark S. Mashuta2, Craig A.
Grapperhaus1, Robert M. Buchanan2. (1) Univ of Louisville, Louisville, Kentucky, United States (2) Chemistry, University
of Louisville, Louisville, Kentucky, United States
Quadradentate Schiff base have played an important role in elucidating the coordination chemistry of many transition
metal ions. We have found that the copper (II) complex of N,N’ bis((1-methylimidazol-2yl) methylene) ethane-1,2-diamine
(bime) undergoes reversible addition of primary alcohols across one of the two C=N bonds. Various forms of the
[Cu(bime)]2+ complex have been studied by X-ray crystallography and EPR spectroscopy. The reversibility of the addition
reaction was followed by UV-vis spectroscopy. Detailed kinetic studies of both the addition and elimination reactions will
be presented along with a proposed mechanism.
INOR 630
Design and synthesis of lightweight MOFs for gas storage
Matthew Shimazu1, [email protected], Xianhui Bu1, Xiang Zhao2. (1) Chemistry, California State Long Beach,
Long Beach, California, United States (2) California State
Long Beach, Long Beach, California, United States
Decreasing the framework density by using lightweight elements can help increase gravimetric absorption properties. We
show some examples of lightweight MOFs made from lithium, the lightest metal. Using the phenol-containing ligands
proves to offer new opportunities over the traditional Li-MOFs made from carboxylate-containing ligands. With the above
strategy we are able to produce a number of interesting Li-MOFs with porosity.
INOR 631
First row transition metal complexes of tetrazine based ligands as a new class of energetic materials
Thomas W. Myers1, [email protected], Susan K. Hanson4, Jacqueline Veauthier2,
David E. Chavez3. (1) Los Alamos National Laboratory, Los Alamos, New Mexico,
United States (2) Los Alamos National Laboratory MS C920, Los Alamos, New Mexico, United States (3) C920, Los
Alamos National Laboratory, Los Alamos, New Mexico, United States
The high nitrogen content, high heat of formation and low lying π system of tetrazines make them ideal candidates for the
synthesis of energetic materials that are photochemically and electrochemically active. Tuning of these properties can be
accomplished through substitution on the tetrazines, or through binding of metal centers. Accordingly complexes of nonenergetic and energetic tetrazine ligands with first row transition metal salts have been synthesized and characterized.
INOR 632
Role of ligand modifications in structural outcomes of dinucleating, criss-crossed cobalt peroxo (μ-OH,μ-O2)
complexes
Yae In Cho, [email protected], Meredith Ward, Michael J. Rose. Dept of
Chemistry, University of Texas at Austin, Austin, Texas, United States
We have reported the synthesis and structural characterization of a dicobalt(III) complex with a μ-OH,μ-O2 core, namely μOH,μ-O2-[Co(enN4)]2(X)3 [1(ClO4)3 and 1(BF4)3]. The dinuclear core is crosslinked by two simple N4 Schiff base ligands
that span each cobalt center. The formally CoIII−CoIII dimer is formed spontaneously upon exposure of the mononuclear
Co(II) complex to air and exhibits a ν(O−O) value at 882 cm −1 that shifts to 833 cm−1 upon substitution with 18O2. The CV
of 1(BF4)3 exhibits a reversible {CoIII−CoIII}↔{CoIII−CoIV} redox process, and we have investigated the oxidized {Co III−CoIV}
species by EPR spectroscopy (g = 2.02, 2.06; S = 1/2 signal) and DFT calculations. Current studies are aimed at isolating
the oxidized {CoIII−CoIV} species, examples of which are quite unstable and scarce in the literature. Next, the ligand was
modified by i) extending the length of the diamine backbone (to investigate the effect of ligand flexibility) or ii) changing the
pyridine ortho substituent (R = -H, -OMe, or -p-PhCl; to examine any possible electronic or steric effects). The use of the
propylenediamine analogue (pnN4) afforded a distal dicobalt(II) species (Co- - -Co = 6.80 Å) with no bridging O2 or OH.
Conversely, the same ligand with R = -OMe produced a monomeric Co(II) species with two half-hydrolyzed ligands [that
is, {pn(OMe-py)}2 ligation]. Thus, it is evident that minor effects in the ligand framework effect large changes in the final
Xray structure, and the unique nature of the original complex 1 is highlighted. Lastly, we will report our progress regarding
ongoing studies into the isolation of the di-iron and dicopper peroxo analogues of 1.
INOR 633
Investigations of the reaction of PMe2Ph with a Pt-Ru heterometallic complex
Zackery J. Manning, [email protected], Nancy C. Dopke. Alma College, Alma, Michigan, United States
Over the last two decades there has been an interest in the use of platinum-ruthenium alloys as electrodes in direct
methanol fuel cells (DMFCs). In an attempt to mimic the solid-state chemistry at the electrode, a series of Pt-Ru
complexes are being synthesized. Removal of a sulfur atom from bridged complexes can provide structures with varying
metal-metal bond distances. Attempts to remove a sulfur atom from [(dppePt) 2(μ3-S)2RuCl(PPh3)2]Cl using PMe2Ph
results in exchange of the phosphines on the ruthenium center, indicated by MALDI mass spectrometry data. The NMR
data suggests a significantly greater change in the structure and indicates multiple products are formed during the
reaction. Varying reaction conditions and characterization techniques will be reported to establish the identity of products.
INOR 634
Chemo-induced spin-state switching using tunable iminopyridine ligands
Tarik Ozumerzifon1, [email protected], Jacek Kolanowski2, Matthew P.
Shores1. (1) Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States (2) University of
Sydney, Sydney, New South Wales, Australia
Spin crossover has been explored in Fe(II) systems in the context of secondary effects, such as anion binding or
hydrogen bonding, and has more recently expanded into reagent-induced triggering.1,2 Our current goal is to utilize known
synthetic organic transformations to induce an irreversible spin-state switching event, taking advantage of significant
changes in the Hammett parameters of substituent pairs to alter the Fe(II) ligand field. Specifically, the utilization of
fluoride as a desilylating agent is being investigated. To this end, the Fe(II) complex of tris[2-(5-tert-butyldimethylsiloxypyridin2-yl)ethylimino]amine [Fe(L5-OTBS)]2+ and related complexes have been synthesized and characterized. The effect of
varying the identity of R and position of the -OSiR3 moiety on the pyridine ring, and thus the Hammett parameter, is also
being assessed.
(1) Ni, Z.; McDaniel, A. M.; Shores, M. P. Chem. Sci., 2010, 1, 615–621.
(2) Hasserodt, J.; Kolanowski, J. L.; Touti, F. Angew. Chem. Int. Ed. 2014, 53, 60 – 73.
INOR 635
Iron(II) complexes of the dimethylated tris(pyrazolyl)ethane ligands
M S. Goodman2, [email protected], Margaret A. Goodman1, Alexander Y.
Nazarenko2. (1) Math and Natural Sciences, D'Youville College, Buffalo, New York,
United States (2) Chemistry, SUNY Buffalo State, Buffalo, New York, United States
The 2:1 Fe(II) complexes of three new tris(pyrazolyl)ethane (tpe) ligands, methylated at either the 3,4-, 4,5-, or 3,5positions of the pyrazoles, were prepared (Figure 1). Synthetic, structural, and spectroscopic studies of the three new
complexes will be presented. Crystal structures of the new tpe complexes indicate that the Fe—N bond lengths range
from 1.94 Å to 1.98 Å, suggestive of low-spin complexes in the solid state. However, 1H NMR results show that the Fe(II)
complexes of 1,1,1-tris(3,4dimethylpyrazolyl)ethane and 1,1,1-tris(3,5-dimethylpyrazolyl)ethane are exhibiting the onset of
spin crossover behavior near room temperature. The results allow clear differentiation of the effect of having methyls in
each position of the pyrazoles on the spin crossover behavior of Fe(II) complexes of tpe ligands, and by extension,
tris(pyrazolyl)methane ligands.
Figure 1. The dimethylated tris(pyrazolyl)ethane (tpe) ligands used in this study
INOR 636
Atropisomerism of iron 5,10,15,20-tetrakis(2-chloro-6-fluorophenyl)porphyrinates
Daniel J. Meininger1, [email protected], Nicanor Muzquiz1, Zachary J.
Tonzetich2. (1) Chemistry, University of Texas at San Antonio, San Antonio, Texas,
United States (2) Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas, United States
5,10,15,20-Tetrakis(2-chloro-6-fluorophenyl) porphyrin (H2ClFTPP) and its iron complexes were examined in order to
probe the effects of oxidation state, axial ligand coordination, and H-F hydrogen bonding on the distribution of
atropisomers. Towards this end, a series of new iron(III) and iron(II) complexes of the porphyrinate have been synthesized
and characterized in both the solid state and solution. The free ligand, H 2ClFTPP, along with 4-, 5-, and 6-coordinate
complexes of iron(III) appear to exist as one isomer on the NMR time scale. In contrast, iron(II) complexes of the
porphyrinate display at least 3 atropisomers at room temperature. The origins and stabilities of the observed atropisomers
is discussed.
INOR 637
Electrochemical analysis of iron nitrilotriacetate complexes
Peter A. Defnet, [email protected], Loren N. Ball, Ursula J. Williams. Chemistry, Juniata College, Huntingdon,
Pennsylvania, United States
We are currently exploring the electrochemical behavior of first row transition metal centers in tripodal ligand environments
in order to examine how the range of available oxidation states is influenced by the ligand structure. Novel mono- and bisnitrilotriacetate (NTA3-) iron complexes were synthesized to examine the range of stable oxidation states available to each
complex. A new synthetic route to iron NTA3- complexes was applied and will be discussed in further detail. IR and UVVIS spectroscopies and single crystal X-ray crystallography were used as methods for structure characterization. Cyclic
voltammetry was used to characterize the electrochemical activity of each complex.
INOR 638
Exploring the impact of ligand variation on arsenic-sulfur bonding using X-ray Absorption Spectroscopy (XAS)
Anastasia V. Blake, [email protected], Courtney M. Donahue, Scott R.
Daly. Chemistry, University of Iowa, Iowa City, Iowa, United States
It is known that poisoning by heavy metal ions occurs worldwide, and that sulfur has a high affinity for heavy metals and
metalloids (arsenic, lead, mercury). However, little is understood about how electronic and structural variations of sulfur
ligands affect the heavy metal-sulfur bond. Our work seeks to gain insight into arsenic-sulfur bonding in order to better
understand As toxicity, remediation, and pharmaceutical applications. We are using ligand K-edge X-ray absorption
spectroscopy to understand how varying the substituents and stereoelectronic properties of sulfur ligands impact arsenicsulfur covalency. In this presentation, we will describe our investigation into how electron withdrawing and donating
substituents affect sulfur bonding in trithioarsenites. In addition, current work focusing on the synthesis of a series of new
tri-cyclic cage complexes containing arsenic-sulfur bonds will be discussed.
INOR 639
Cytoselectivity of organotin and transition metal-substituted organotin compounds on cancer cells
Jose S. Enriquez1, [email protected], Jonathan A. Muniz1, Armando Varela3, Keith H. Pannell2, Renato
Aguilera3. (1) Chemistry, University of Texas at El
Paso, El Paso, Texas, United States (2) Univ of Texas, El Paso, Texas, United States
(3) Biology, University of Texas at El Paso, El Paso, Texas, United States
One of the first organometallic compounds that is still used against cancer is the square planar Cisplatin, (Cl 2(NH3)2Pt). In
our laboratory we have synthesized a series of tin compounds with a similar dichloro feature, e.g. R 2SnCl2. Normally such
systems would be tetrahedral at tin, but by incorporating R groups with pendant ligand atoms such as O, S etc. we can
transform them into potentially hexa-coordinated structures. Thus we have been synthesized and tested a series of simple
organotin and transition metal-substituted organotin complexes, R2SnCl2, on MDA- MB231 breast cancer cells (grown in
DMEM media) and MCF 10A non-tumorigenic cells (grown in DMEM-F12 media). The functionality R = CH2C6H4-o(EMe)
(E = O, S, CH2); (C5H5)Fe(CO)2 were examined. Using established protocols the IC50 for 24 hours was determined and
for the MDA-MB 231 cell line an IC50 of 26-nanomolar final concentration was observed, and for the MCF 10A cell line an
IC50 of 15-nanomolar final concentration was observed! Against all cell lines the compounds act in an apoptotic manner,
and surprisingly the compounds with the capacity to be octahedral were more active than those without such a capacity,
e.g. E = CH2 . All compounds exhibit apoptotic properties. Support of this research was provided by the NIH MARC (grant
#5T34GM008048) and RISE (grant #5R25GM069621-08) programs.
INOR 640
Synthesis of novel bismuth complexes for small molecule activation
Maximiliano Castillo, [email protected], Omar Barreda, Rolando Aguilar,
Skye Fortier, Alejandro J. Metta-Magana. Chemistry, University of Texas at El Paso, El Paso, Texas, United States
Bismuth has found use in a wide range of applications from pharmaceuticals to thermoelectric materials and is unique in
that it is a non-toxic heavy metal. Additionally, owing to bismuth’s high oxygen-ion conductivity, the bismuth chalcogenide
Bi2O3 is used industrially as a heterogeneous, selective oxidation catalyst. Consequently, the solid-state chemistry of
bismuth has been extensively studied. However, the chemistry of molecular bismuth chalcogenides remains ill defined
and poorly understood. To better elucidate the chemistry of bismuth chalcogenide materials, especially oxides, we are
currently exploring the synthesis of molecular compounds featuring terminal bismuth chalcogenide moieties. Synthetic
methodology, efforts, and characterization of these complexes will be presented.
INOR 641
Synthesis and reactivity of a novel doubly base stabilized five-coordinate “silene” derivative, [k3C(SiMe2benzimidi-Pr)2]SiMe2: Addition of a Zn–Me bond of Me2Zn to afford [k3-C(SiMe3)(SiMe2benzimidi-Pr)2]ZnMe
Serge Ruccolo, [email protected], Gerard F. Parkin. Columbia University, New
York, New York, United States
Silenes, compounds that feature R2C=SiR2 moieties are an important class of compound that have received considerable
attention. The three-coordinate silicon in such compounds is often Lewis acidic such that coordination by a Lewis base is
often encountered. Five-coordinate, doubly base stabilized silenes have not, however, been isolated and structurally
characterized by X-ray diffraction. It is, therefore, noteworthy that we have been able to isolate the intramolecularly base
stabilized “silene” derivative, [k 3-C(SiMe2benzimidi-Pr)2]SiMe2, via deprotonation of N–isopropylbenzimidazole followed by
reaction with HC(SiMe2Cl)3. X–ray diffraction studies demonstrate that the Si2C and SiMe2 groups of [k3-C(SiMe2benzimidiPr) ]SiMe are orthogonal to each other, such that a p-bond is precluded. As such, the compound is best represented as a
2
2
Si+–C– zwitterion. In terms of reactivity, [k 3-C(SiMe2benzimidi-Pr)2]SiMe2 reacts with Me2Zn to give [k3C(SiMe3)(SiMe2benzimidi-Pr)2]ZnMe. The formation of this product can be viewed as resulting from a formal addition of the
Zn–C bond in a direction that is consistent with the Si+–C– polarity, accompanied by migration of the nitrogen donors from
silicon to zinc.
INOR 642
Multistep synthesis of the biocompatible lactone 3,6-dihydro-2H-pyran-2-one
Brad S. Cundiff1,2, [email protected]. (1) Chemistry, Georgetown
College, Cox's Creek, Kentucky, United States (2) Chemistry, University of Louisville, Louisville, Kentucky, United States
Conventional bio-derived polymers such as polylactide (PLA) are desirable due to the fact that they are bio-renewable and
biodegradable. However, PLA does have a shortcoming: its functionality makes it hydrophobic and thus slow to
breakdown. This hinders its applications. As a result, it is necessary to create new ways to synthesize and produce
functionalized PLA materials that use biologically appropriate monomers. To address this problem, we are interested in
developing a method to synthesize a C5 functionalized lactone—3,6-dihydro-2H-pyran-2-one—from C5-rich hydrozylate.
The C5 cyclic ester is synthesized from L-arabinose and D-Xylose which are sugars that can be obtained from BrownForman’s dried distiller’s grain (DDG). The method for producing the lactone comes from a series of known reactions.
However, majority of the work done focuses on the optimization of step 3 (the glycal synthesis). Additionally, no work has
been done on the ring opening capacity of the cyclic ester. We believe that the unconjugated double bond in the lactone
will allow for this possibility and enable us to create new materials with different properties. This will be addressed after
successful completion and optimization of the overall synthesis.
INOR 643
Coupling of cyclohexadiene oxide and CO2 via metal catalysts
Christopher J. Arp, [email protected], Wan-Chun Chung, Fu-Te Tsai, Samuel J.
Kyran, Donald J. Darensbourg. Department of Chemistry, Texas A&M University, College Station, Texas, United States
Preparation of polycarbonates from CO2 and epoxide is a greener alternative to the conventional route involving phosgene
and diols and is a significant area of interest in literature.1 Of recent, poly(propylene carbonate) has been commercialized
for use in bottles and binding agents due to its good mechanical properties. 2 Another well-studied polymer is
poly(cyclohexene carbonate), but this has found limited applications due to its brittle nature. In this work, we look at
copolymerizing CO2 with 1,2-epoxy-4cyclohexene, a monomer which has some common features to cyclohexene oxide
but whose olefin backbone provides opportunities for post-polymerization modification.
This presentation will thus describe our results in making poly(cyclohexadiene carbonate) using various metal catalysts,
including the isolation and structural characterization of cyclic carbonate byproducts. Conversion of this hydrophobic
polymer to amphiphilic and water-soluble polycarbonates via thiol-ene click reactions will also be discussed.
INOR 644
Synthesis and characterization of aluminum β-diketiminate complexes and their application in ring opening
polymerization of lactides and synthesis of cyclic carbonates
shi bian, [email protected], Guodong Du. Chemistry, University of North Dakota, Grand Forks, North Dakota, United
States
Polylactide (PLA), a biodegradable and biocompatible polyester, can be derived from renewable resources via ring
opening polymerization of lactides. Current effort is devoted to the search for controlled methods and catalysts for its
production. In this work, a series of new aluminum complexes with chiral β-diketiminate type ligands have been
synthesized and characterized. The complexes provided decent reactivity and stereoselectivity in the polymerization of
lactide. In addition, these new aluminum complexes also have been applied to the synthesis of cyclic carbonates from
epoxides.
INOR 645
Synthesis, characterization, and polymerization of thienyl phosphine paladium(II) complexes
Jessica L. Shott, [email protected], Brian J. Reeves, Brycelyn M.
Boardman. Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia, United States
Palladium(II) complexes with functionalized thienyl phosphine ligands have been synthesized and polymerized. The
synthesis of brominated thiophene ligands was performed by allowing 2,5-dibromothiophene to react with n-butyllithium,
followed by the addition of chlorodiphenylphosphine or chlorodiethylphosphine to produce 2-bromo5diphenylphosphinothiophene (1) and 2-bromo-5-diethylphosphinothiophene (2) respectively. Compounds 1 and 2 were
allowed to react with dichloro(1,5cyclooctadiene)palladium (II) to form either bis(2-bromo-5diphenylphosphinothiophene)palladium(II)dichloride (3) or bis(2-bromo-5diethhylphosphinothiophene)palladium(II)dichloride (4) respectively. Polymerizations of 3 and 4 were performed using 3hexylthiophene and (2,5-bis-trimethylstannyl)thiophene as co-monomers. 1H, 13C, and 31P NMR, ultraviolet-visible
spectroscopy, and fluorescence spectroscopy were used to characterize the phosphine ligands and palladium complexes.
UV-visible spectroscopy and 1H NMR also confirm the incorporation of the palladium complexes into the polymer
backbone.
INOR 646
Extending π-conjugation for metallo-organic photon harvesting
Malcolm H. Chisholm1, Jacqueline Leizerman2, [email protected]. (1) Ohio State Univ, Columbus, Ohio,
United States (2) The Ohio State University, Columbus, Ohio, United States
Metallo-organic hybrid materials incorporating M2 quadruply bonded units have been prepared that have interesting
properties that make them attractive for optoelectronic applications. Ligands of the general formula [ -O2CThnCCX], where
Th= 2,5- thiophene, X = π-conjugated organic fragment, and n= 2 or 3, have been synthesized and used to prepare
complexes of the formula trans-Mo2(O2CL)2(O2CThnCCR)2, where L= 2,4,6triisopropylphenyl, and R= H, Ph. The Mo2
complexes are characterized by 1H-NMR and IR spectroscopy, and MALDI-TOF MS. These complexes exhibit a strong
metal to ligand charge transfer in the visible region, making them appealing for use in metalloorganic materials and
photovoltaics. The fundamental photophysical properties of the Mo 2 complexes have also been explored by UV-visible
electronic absorption and emission, near-IR emission, and time resolved spectroscopies. The electronic structures of
these complexes are being investigated by density functional theory (DFT) and timedependent DFT and have been used
to support the photophysical data. Electrochemical experiments were used to further characterize the complexes potential
use in optoelectronics.
INOR 647
Theoretical study of the sodium mediated coupling of organchlorosilanes: Stable α-chloro-ω-sodium cyclosilane
intermediates in the Wurtz synthesis of polysilanes?
Simon J. Holder, [email protected]. University of Kent, Canterbury, United Kingdom
The Wurtz-reductive coupling polymerization of dichlorodiorganosilanes with sodium metal is the standard method for the
synthesis of polysilanes. A theoretical study using density functional theory has been carried out giving valuable insights
into the mechanism that we compare with experimental results from our group and others. The initial single electron
transfer from sodium to dichlorodimethylsilane results in the formation of a sodium cation chlorosilane anion radical pair or
a chlorosilane radical; calculations at the B2GPLYP/6-311+G(3df,3p)//B3LYP/6-311+G(d,p) level of theory suggests that
the radical anion is the energetically and kinetically preferred intermediate. The subsequent sodium chorodimethylsilane
species formed by the subsequent single electron transfer reaction from sodium can generate 3 possible structures
namely a silylenoid, a silyl anion and an inverted structure. Again studies at the B2GPLYP/6-311+G(3df,3p)//B3LYP/6311+G(d,p) level indicate that the silylenoid species is the most thermodynamically stable form. The addition of further
dimethylsilane units leads to chains where the α-chloro-ω-sodium cyclosilane is thermodynamically stabilised in
preference to the all-trans sodium silyl anionic form. This species is characterised by - Si-Na-Cl-Si- bonding interactions
that 'close' the ring and stabilise the cyclic structure.This apparent preference for stable cyclic intermediates in the chain
growth of polysilanes by the Wurtz method suggests a ready explanation for cyclic silanes being the majority product in
most polysilane syntheses from dichlorosilanes utilising alkali metals.
Stable structures for sodium chloro silanes with 1, 2 and 3 silicons.
Example of a cyclic-trans equilibrium for a sodium chloro tetrasilane.
INOR 648
Synthesis of aluminum nanoparticles capped with o-carborane
Alexander Benziger2, [email protected], Paul A. Jelliss3, Steven W. Buckner1. (1)
Saint Louis University, Dept of Chem, Saint Louis, Missouri, United States (2)
Chemistry, Saint Louis University, St. Louis, Missouri, United States (3) St Louis Univ, Saint Louis, Missouri, United States
o-Carborane is explored as a capping and passivating agent for metallic aluminum (Al) nanoparticles. PXRD (Powder XRay Diffraction) was then used to confirm the synthesis of fcc aluminum nanoparticles. It was seen that the o-carborane
(Cb) also formed a crystalline structure while under an inert atmosphere. When exposed to air for 3 days, it was seen that
the o-carborane lost its crystalline structure, and instead adopted an amorphous form. Particle sizes on the order of 30 nm
were calculated through PXRD, and these sizes were confirmed through analysis of the nanoparticles via TEM
(Transmission Electron Microscopy). It has been observed that the passivation of the aluminum core with o-carborane has
left a very high active aluminum content after initial synthesis. This active aluminum content remains high for time periods
on the order of months when exposed to regular atmospheric conditions.
INOR 649
Stability of gold nanoparticle-based films deposited on plasma-etched borosilicate glass via a layer-by-layer
physisorption technique Rebecca L. Svatora, [email protected], Scott A. Darveau, Christopher L.
Exstrom. Department of Chemistry, University of Nebraska at Kearney, Kearney, Nebraska, United States
Solution casting of gold nanoparticle films for biosensor devices generates less waste than vacuum-based evaporation
and sputtering methods for gold film fabrication; however, film uniformity and proper adhesion can be more difficult to
achieve. Spherical gold nanoparticles of 30-50 nm diameter were prepared by the citrate reduction method and coated
onto plasma-etched borosilicate coverslip substrates that had been previously coated with poly(diallyldimethyl)ammonium
chloride. While visibly uniform films were produced, they were sensitive to mechanical wear and nanoparticle aggregation
was observed by UV-vis spectroscopy, as indicated by absorption at wavelengths longer than 700 nm, to occur during
deposition. Immersion of films in aqueous NaCl solutions induced further aggregation that could be arrested to some
extent with a post-deposition coating of the gold nanoparticles with polyethylene glycol. The effect of Protein A, which is
known to bind to gold and serve as a linker to biosensor molecules, on nanoparticle aggregation will also be discussed.
INOR 650
Stabilization of anisotropic gold nanoparticle shapes by Protein A
Bethany A. Lueck, [email protected], Scott A. Darveau, Christopher L.
Exstrom. Department of Chemistry, University of Nebraska at Kearney, Kearney, Nebraska, United States
Anisotropic gold nanoparticles exhibit red-shifted surface plasmon resonances that are potentially useful for biosensor
applications. While such nanoparticles can be prepared using surfactant-free one-pot methods, the particles are
thermodynamically driven toward spherical shapes in later growth stages. We report that Protein A (PrA), which is known
to coat gold nanoparticles and serve as a linker to antibodies and other species that can bind to biological analytes of
interest, can stabilize branched gold nanoparticles, prepared by the reduction of HAuCl 4 by triethylamine in ethylene
glycol solvent, at temperatures up to 90 oC as evidence by UV-vis spectroscopy and transmission electron microscopy.
Preliminary investigations of Au-PrA-biotinstreptavidin binding will also be discussed.
INOR 651
Heat-mediated drug release from inorganic nanoparticles
Nathan D. Klein, [email protected], Katie R. Hurley, Hattie L. Ring, Joseph T.
Buchman, Christy L. Haynes. Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
In recent years, iron oxide nanoparticles (IONPs) have been investigated for use as a theranostic device in cancer
treatment. Due to their magnetic characteristics, IONPs can provide image contrast through MRI and induce hyperthermia
in a tumor upon the application of an alternating magnetic field. Mesoporous silica has been synthesized around these
IONPs to create stable and biocompatible core-shell structured nanoparticles (msIONPs). The high surface area and pore
volume of these msIONPs provides cargo capacity that could be utilized to load anti-cancer drugs, such as doxorubicin, to
be released as a combination treatment with hyperthermia. While loading has been investigated in mesoporous silica
particles, there has been limited study of release under hyperthermia conditions. In this research, the effect of heat on the
release of doxorubicin from msIONPs has been studied. Drug loading and release methodologies have been developed
for this nanoparticle theranostic platform and used to obtain heat-mediated release profiles from msIONPs.
INOR 652
Soft inorganic oxide nanofibrous membranes and their applications
Xue Mao1, [email protected], Bin Ding2. (1) State Key Laboratory for
Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua
University, Shanghai, China (2) Key Laboratory of Textile Science & Technology, Ministry of Education, College of
Textiles, Donghua University, Shanghai, China
Over the past decade, inorganic oxide materials with different forms and compositions have drawn tremendous attentions
and array of intriguing applications, including the fabrication of electronic and photonic devices, sensors, electrodes,
catalyst supports, and drug delivery components. One dimensional (1D) inorganic oxide nanofibers, particular, are of
great interest owing to their large surface area, high porosity, and good chemical durability, which results in high efficiency
in the above mentioned applications. Up to now, many efforts have been given to fabricate inorganic oxide nanofibers,
including chemical vapor deposition, hydrothermal treatment, layer-by-layer, and electrospinning techniques. Among the
various approaches, electrospinning as a straightforward, versatile, and cost-effective top-down technique has been
widely employed to fabricate 1D nanofibers, including polymer nanofibers, oxide nanofibers, carbon nanofibers, composite
nanofibers, and so forth. By employed sol-gel, electrospinning, and subsequent calcination, varied oxide nanofibers
including SiO2, Al2O3, and ZrO2 have been prepared, however, there still remain a lot of limitations for practical
applications because of bad toughness, amphiphilic, and low stability. This report will focus on an overview progress of
soft inorganic oxide nanofibers including silica nanofibers and zirconia nanofibers, from the fabrication, modification to
applications. The soft oxide nanofibrous membranes with relative high tensile strength were fabricated for the highefficiency fine particulate filtration, waterproof and breathable films, and corrosive liquid filtration. Meanwhile, the soft
mechanism and phase transformation of zirconia nanofibers were carefully discussed in this report. Although to
exploration of soft inorganic oxide nanofibers from the theory to real applications as well as from laboratory to industrial
production still has some way to go, the unremitting efforts will push forward the rapid development of the inorganic oxide
nanofibrous materials will have a bright future for the industrial applications toward various environmental issues.
INOR 653
Design and synthesis of precursors for surface plasmon mediated chemical solution deposition of metal
nanoparticles
Nathaniel Richey, [email protected], Yung-Chien Wu, Jingjing Qiu, W. D. Wei,
Lisa McElwee-White. University of Florida, Gainesville, Florida, United States
We have previously demonstrated surface plasmon mediated chemical solution deposition (SPMCSD) of gold
nanoparticles on nanostructured silver substrates using MeAuPPh3 as a gold(I) precursor. The nanoparticles were free of
stabilizing ligands and ranged in size from 3 to 10 nm depending on the deposition time. Extension of these results to the
design and synthesis of suitable precursors for the SPMCSD of other noble metals will be discussed.
INOR 654
Role of oxygen vacancy in nanocrystalline perovskite oxides for electrochemical reactions
Jaemin Kim2, [email protected], Xi Yin2, Kai-Chieh Tsao2, Shaohua Fang2, Hong
Yang1. (1) Chem. Biomol. Engr., Box C-3, MC-712, University of Illinois, Urbana, Illinois,
United States (2) Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois,
United States
Various perovskites and their related structures have intensely studied for applications in solar cell, fuel cell, water splitting
device and metal air battery, in part because of their flexibility in the choice of compositions, including the earth-abundant
elements and nonnoble metals.1-4 The change in composition will result in different electronic structures of catalysts.
Various studies suggest the electron configuration of B-site metal ion is very important for electrocatalytic activity in
oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this presentation, we report a new class of high
performance ordered oxygen-deficient perovskite oxide (A2B2O5) electrocatalysts with nanocrystalline structure.5 We
hypothesize that oxygen vacancy should also play an important role and is a structural factor to facilitate the OER kinetics.
We show that oxygen deficient perovskite, Ca2Mn2O5, can catalyze the generation of oxygen gas at ~1.50 V versus (vs)
reversible hydrogen electrode (RHE) electrochemically in alkaline media, and reach an OER mass activity of 30.1 A/g at
1.70 V (vs RHE). Ca2Mn2O5 also shows higher OER activity than perovskite CaMnO3, suggesting that oxygen-deficient
perovskite A2B2O5 has the potential to become a new class of high performance electrocatalysts for rechargeable metalair battery as well as in water splitting.
(1) Takeguchi, T.; Yamanaka, T.; Takahashi, H.; Watanabe, H.; Kuroki, T.; Nakanishi, H.; Orikasa, Y.; Uchimoto, Y.; Takano,
H.; Ohguri, N.; Matsuda, M.; Murota, T.; Uosaki,
K.; Ueda, W. J. Am. Chem. Soc. 2013, 135, 11125.
(2) Savinell, R. F. Nat. Chem. 2011, 3, 501.
(3) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Science 2012, 338, 643.
(4) Vojvodic, A.; Norskov, J. K. Science 2011, 334, 1355.
(5) Kim, J.; Yin, X.; Tsao, K.-C.; Fang, S.; Yang, H. J. Am. Chem. Soc. 2014, published.
INOR 655
Direct assembly of zeolite beta into mesoporous nanoparticles
Tzu-Ying Chen2, [email protected], Yihsin Liu1, Chung-Yuan Mou2. (1)
Department of Chemistry , National Taiwan Normal University, Taipei, Taiwan (2) Department of Chemistry, National
Taiwan University, Taipei, Taiwan
Here we report a facile synthesis of mesoporous zeolites using inexpensive quaternary ammonia salt and anionic
surfactant in a single-pot condition. The discovery of such an innovative pathway is attributed to unconventional assembly
of zeolite beta seed in diluted systems of quaternary ammonia salts that initially form spherical micelles assembling with
inorganic precursors at 40-55 °C and later serve as bilayer templates for mesochannels. The formation of the
mesochannels can be directly monitored by time-dependent small-angle X-ray scatterings (SAXS) and N2 adsorptiondesorption isotherms, confirming presence of mesopore expansion and periodicity domains (6-10 nm) during the
assembly. In addition, unique IR vibration modes (500-600 cm-1) and polygon-pore morphology in SEM images rationally
support our hypothesis of fivemember rings as in the zeolites comprising of the nanoparticles. Other structural and
chemical analyses, such NH3-TDP and 27Al NMR, are currently under the way to explore the acidic natures of the zeolite
in these mesoporous nanoparticles.
INOR 656
Ligand-induced fate of embryonic seeds in the shape-controlled synthesis of rhodium nanoparticles
Adam J. Biacchi2,1, [email protected], Raymond E. Schaak1. (1) Department of Chemistry, The Pennsylvania State
University, University Park, Pennsylvania, United
States (2) Nanoelectronics Group, National Institute of Standards and Technology
(NIST), Gaithersburg, Maryland, United States
Noble metal nanoparticles have been widely studied due to their use in catalysis, photonics, electronics, sensing, and
biomedicine. While it is known that their properties and performance can be tuned through prudent control of morphology,
the differences and similarities in formation route for particles of disparate geometry and crystallinity are not well
understood. Here we report a comprehensive study of the process by which colloidal noble metal nanoparticles having
several distinct shapes nucleate and grow when employing the polyol synthesis. Through analysis of aliquots taken during
the reactions, we found that, for all morphologies, metal clusters with diameters <2 nm first nucleated as a stable
intermediate following precursor reduction and prior to the initiation of widespread growth. These nucleated clusters
served as embryonic seeds that grew to form monodisperse metal nanoparticles of varying shapes. Extensive
highresolution transmission electron microscopy revealed that the growth pathway – monomer addition, coalescence, or a
combination of the two – was different for each of three different morphologies, and was likely directed by the interactions
of each specific anionic ligand with the metal surfaces. Although we focus primarily on synthesis of Rh nanoparticles,
studies on Pt and Pd suggest this formation route is general for the synthesis of noble metal nanoparticles by the polyol
process.
INOR 657
Binding and static quenching behavior of iridium (I) dyes on monodispersed zinc oxide nanocrystals
Tyler J. Morin, [email protected], David A. Blank, Wayne L. Gladfelter, Kent R. Mann. Chemistry, University of
Minnesota, Minneapolis, Minnesota, United States
Dye sensitized solar cells most commonly consist of a nanocrystalline titanium dioxide film and a bipyridine based
inorganic dye. More recently however, zinc oxide nanocrystals have gained attention due to an increased electron mobility
as well as the ability to make monodispersed nanocrystal dispersions for solution based studies. Additionally, there has
been an increased focus on the development of new dyes. As such, iridium (I) pyrazolate dimers have been synthesized
with carboxylate groups for attachment to zinc oxide nanocrystals in a range of sizes (3.0 - 5.0 nm). These newly
synthesized complexes have been characterized using a variety of methods including absorption and emission
spectroscopy. Static quenching of the luminescence of the iridium (I) dimers is observed through Stern-Volmer quenching
experiments. Ultrafast transient absorption spectroscopy has been used to investigate the kinetics of electron injection
into the zinc oxide nanocrystal.
INOR 658
Digestive ripening of gold nanorods in aqueous solution: Effect of CTAB and Au concentration
Pablo Guimera Coll1, [email protected], Christopher M. Sorensen 2. (1) Physics,
Kansas State , Manhattan, Kansas, United States (2) Kansas State University, Manhattan, Kansas, United States
The response of gold nanorods to digestive ripening has been examined in an aqueous solution in the presence of
cetyltrimethylammonium bromide (CTAB). Digestive ripening has proved before to transform a highly size dispersed
nanoparticle solutions into a nearly monodisperse ones. Here we observed that nanorods tend to shrink in length and
completely transform into nanospheres or atomic Au after enough digestive ripening (DR) time. The concentration of
CTAB and gold strongly influence the result of the ripening.
UV-Vis Spectra of Au/CTAB sample with Digestive Ripening time
INOR 659
Design and controllable synthesis of Au@MOF Core@Shell Nanotructures
Chixia Tian, [email protected], Stephen G. Boyes, Alexis Worcester. Chemistry
Dept, Colorado School of Mines, Golden, Colorado, United States
Controllable integration of metal-organic framework (MOF) and noble metal nanoparticles is attractive for diverse
applications, including but not limited to catalysis, sensing, theragnostics and plasmonic devices. Extensive research
efforts have been implemented to prepare noble metal encapsulated into or deposited onto transition metal MOFs,
especially Zn-based MOFs. However, few or none research has been conducted to incorporate noble metal (e.g., gold)
nanoparticles with lanthanide-based MOFs. Gadolinium, lying in the middle of the lanthanide elements family, was herein
chosen as a model due to its known advantages for a variety of applications (e.g., contrast agents for magnetic resonance
imaging). In this work, the methods for synthesizing gold core-gadolinium MOF shell at both room temperature and
elevated temperature will be discussed. Understanding how gadolinium acts differently from transition metals during the
synthesis will also be addressed. Finally, it is anticipated that the controllable synthesis can provide high quality materials
for diverse applications.
INOR 660
Studies of CdSe and CdSe/CdS core-shell quantum belts
Yang Zhou1, [email protected], Fudong Wang4, Yuanyuan Wang5, Linjia Mu2, William E. Buhro3. (1)
Chemistry, Washington University in St.Louis, Saint
Louis, Missouri, United States (2) Department of Chemistry, Campus Box 1134,
Washington University in St. Louis, Saint Louis, Missouri, United States (3) Washington
Univ, Saint Louis, Missouri, United States (4) Washington University in St.Louis, Saint Louis, Missouri, United States
Quantum belts (QBs) are recently discovered nanocrystals having potential applications in several fields because of their
unique optical properties. The purity and crystalline quality of semiconductors can be measured by photoluminescence
quantum efficiencies (PLQE) and PLQE are unusually high for the nanocrystals with large and extended dimensions, like
CdSe QBs. Herein we report new and efficient methods for synthesis of CdSe/CdS QBs core/shell nanocrystals using a
“flash” synthesis at high temperature. The CdSe/CdS core/shell structure further improves the optical properties of coreonly structures by optimizing surface passivation and the PLQE can reach 39%. The robust optical properties of the
core/shell QBs may find some applications in the field of optoelectronics.
INOR 661
Synthesis of palladium diphosphine complexes for XAS analysis
Chelsie M. Forrest2, [email protected], Courtney M. Donahue1, Anastasia Blake1,
Scott R. Daly1, Brian J. Bellott2, [email protected]. (1) Chemistry, University of Iowa, Coralville, Iowa, United States
(2) Western Illinois University, Macomb, Illinois,
United States
As part of a larger effort to investigate metal-phosphorus bonding using ligand K-edge X-ray absorption spectroscopy
(XAS), we report an efficient method for the synthesis of eight palladium chloride complexes containing diphosphine
ligands. All of the complexes to be described were characterized by 1H NMR and 31P{1H} NMR spectroscopy, and
previously unreported single crystal X-ray structures will be discussed. Preliminary XAS results will also be presented.
INOR 662
Transition metal carbides as noble metal fuel cell support materials
James M. Thode, [email protected]. Chemistry, University of Wyoming, Laramie, Wyoming, United States
The role of transition metal carbides has become essential to the discussion on fuel cell catalysis. While carbides are well
known for a variety of hydrogen transfer reactions, they have received a great deal of attention recently due to their
efficiency in simple fuel cell/electrolysis reactions including: the hydrogen and oxygen evolution reactions(HER/OER), the
oxygen reduction reaction(ORR), and the oxidation of alcohols (i.e. methanol (MOR), ethanol (EOR), glycerol (GOR),
etc.). As a refractory material, carbides have demonstrated improved stability over carbon based supports in highly
oxidative and reductive environments in both acidic and basic media. This poster presents an overview of the synthetic
techniques for all group 4-6 transition metal carbides, a procedure for noble metal deposition, and the characterization of
novel fuel cell catalysts using a variety of investigative techniques that includes: powder X-ray diffraction (XRD), electron
microscopy techniques (both SEM &TEM), inductively coupled plasma optical emission spectroscopy(ICP-OES), and
electrochemistry.
INOR 663
Synthesis and analysis of heterobimetallic cobalt-zirconium complex for artificial photosynthesis
Scott Chapp, [email protected], Nicolette Celia, Adam Hill. Chemsitry, St.
Lawrence University, Des Plaines, Illinois, United States
With the growing need for renewable energy, catalysis research involving heterobimetallic compounds have seen a
significant influx for use in artificial photosynthesis. Through the proper selection of metals, CO2 can be effectively cleaved
into CO and O2. Studies suggest that cobalt-zirconium complexes show great promise in the catalytic reduction of CO 2. A
series of cobalt-zirconium materials supported on either MCM-41 mesoporous silica or phosphinoamide ligands has been
synthesized. The latter ligands could provide a direct metal-metal bond while increasing the overall stability. The current
heterobimetallic complex demonstrates a large absorbance of visible light to a productive charge transfer state, which
further supports the use of these metals for artificial photosynthesis.
INOR 664
Nonheme iron complex-catalyzed efficient alcohol oxidation by t-BuOOH with Nhydroxyphthalimide as a
cocatalyst
Sun Young Lee1, [email protected], Pan-Gi Kim2, Cheal Kim3. (1) Seoul National
University of Science & Technology, Seoul, Korea (the Republic of) (2) Kyungpook National University, Sangju, Korea (the
Republic of)
Two iron catalysts ([Fe(bpc)Cl2][Et3NH] (1a) and [Fe(Me2bpb)Cl2][Et3NH] (1b) show an efficient oxidation of various
alcohols to the corresponding carbonyl products using tBuOOH as an oxidant in the presence of NHPI under a mild
condition. 1a having electron-withdrawing group showed better catalytic activity for the alcohol oxidation than 1b with
electron-donating group. The mechanistic studies showed that the reactive intermediates responsible for the alcohol
oxidations have electrophilic character and the H-atom abstraction from C-H bonds is involved in the rate-determining
step under the catalytic systems.
INOR 665
Versatile syntheses of optically pure ECE' pincer complexes
Xiangyuan Yang, [email protected], Weeshan Tay, Yongxin Li, Pullarkat A.
Sumod, Pak-Hing Leung. Chemistry & Biological Chemistry, Nanyang Technological University, Singapore, Singapore
The pioneering work of Shaw,1 van Koten and Noltes2 on transition metal pincer complexes in the 1970s sparked an
explosive period of development and exploitation for this class of privileged ligand scaffolds. Recently, we have
successfully developed a methodology for the synthesis of chiral pincer complexes. Optically pure C-stereogenic PCPand PCN-ligands can be synthesized via a facile protocol from simple 6/7-carbon building blocks in high overall yields and
excellent stereoselectivity. This new protocol of preparing the ligand backbones allows easy modification of the parasubstituent, chiral functionalities, neutral electron donors and the transition metal center. The one-pot
hydrophosphination/metalation procedure was successful in preparing a series of optically pure palladium, platinum and
nickel pincer complexes in high isolated yields of 70-91%.
Reference
[1] Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1976, 1020.
[2] van Koten, G.; Timmer, K.; Noltes, J. G.; Spek, A. L. J. Chem. Soc., Chem Commun. 1978, 250.
INOR 666
Toward inner-sphere photoactivation of carbonyl and imine groups using Earthabundant Schiff-base
photocatalysts
David J. Boston2, [email protected], Francisco J. Sarabia5, Michael P. Nguyen4,
Collette Midkiff2, Eric M. Ferreira5, Anthony K. Rappe1, Matthew P. Shores3. (1)
Colorado State University, Fort Collins, Colorado, United States (2) Chemistry,
Colorado State University, Fort Collins, Colorado, United States (3) Department of
Chemistry, Colorado State University, Fort Collins, Colorado, United States (5)
Chemistry, University of Georgia, Anthens, Georgia, United States
Photocatalysts offer an effective way to initiate chemical reactions that are reductive or oxidative in nature. The use of
Earth-abundant first-row transition-metal ions such as V,
Cr, Ni, Cu to photochemically activate C=O and C=N π bonds is desirable, especially in the context of replacing expensive
1-electron reagents for organic synthesis, such as SmI2. Employing Schiff-base ligands with four nitrogen donor atoms,
we have made complexes that absorb strongly in the visible spectrum and have open metal coordination sites for binding
substrates. The complex Ni(thb) (thb = ((13E, 19E)5,6,7,8-tetrahydrotribenzo[b,f,l][1,4,8]tetraazacyclotetradecine) has
proven to be a strong absorber and capable of binding both benzaldehyde and acetylaldehyde. The synthesis,
characterization, and catalytic screening of [Ni(thb)] and other metal analogs will be discussed.
INOR 667
Synthesis, electrochemistry, and catalytic properties of hexacoordinate bisbipyridylsilicon(IV) complexes
Christina Maguylo2, [email protected], Sophia Garofalo2, Tram Le2, Thanh Huynh2,
Thomas A. Schmedake1. (1) UNC-Charlotte, Charlotte, North Carolina, United States
(2) University of North Carolina - Charlotte, Charlotte, North Carolina, United States
A series of novel hexacoordinate bis-bipyridylsilicon(IV) complexes have been synthesized by reacting [Si(bipy) 2I2]I2 with
the appropriate alcohol or diol. Characterization was done and crystal structures have been obtained for the complexes:
[Si(bpy)2(OMe)2]I2, [Si(bpy)2(-OCH2CH2O-)](I)(I3), [Si(bpy)2(OPh)2](I3)2, [Si(bpy)2(cat)](PF6)2, [Si(bpy)2(bph)](PF6)2, and
[Si(dmbpy)2(OH)2]I2 (bpy=
2,2'bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, bbbpy = 4,4′-di-tert-butyl-2,2′dipyridyl cat= 1,2-benzenediolato,
bph=2,2'-biphenolato ligand). Two of these new hexacoordinate silicon diol complexes has been synthesized and tested
for catalytic activity. Dihydroxy-bis-(4,4′-di-tert-butyl-2,2′-dipyridyl)silicon(IV) and dihydroxy-bis-(4,4'dimethyl-2,2'bipyridine)silicon(IV) were synthesized and found to be quite soluble in organic solvents due to the t-butyl or methyl
groups on the bipyridine. Catalytic studies, such as the addition of indole to trans-β-nitrostyrene, show that these
complexes can act similar to other silicon diol catalysts. They are effective as “designer Lewis acid” catalysts.
Experimental results show 76% reaction with only 2% mole equivalents of catalyst.
INOR 668
Investigation of substituted bidentate polypyridyl vanadium chromophores for photocatalysis
Michael P. Nguyen1, [email protected], Anthony K. Rappe2, Matthew P. Shores3. (1) Chemistry, Colorado State
University, Fort Collins, Colorado, United States
(2) Colorado State University, Fort Collins, Colorado, United States (3) Department of Chemistry, Colorado State
University, Fort Collins, Colorado, United States
Polypyridyl first-row transition-metal complexes are of interest for their potential to act as chromophores for novel C-C
bond forming schemes. Previously reported Cr(III) aromatic diimine complexes were demonstrated to show strongly
photooxidizing properties.1 The isoelectronic V(II) analogues of these Cr(III) species are targeted for red-shifting electronic
absorptions further into the visible spectrum. Comparison of redox potentials for V(II) bipyridine complexes points toward
the need for strongly electronwithdrawing moieties to shift redox potentials to more positive values to be comparable with
Cr(III) complexes.2 The coupling of a V(II) metal center to electron-withdrawing ligands should allow for a more effective
visible-light activation of the photooxidant when compared to similar Cr(III) complexes. The syntheses, crystal structures,
redox potentials, electronic transitions and photocatalytic screening of these complexes will be presented.
1) McDaniel, A. M.; Tseng, H. W.; Damrauer, N. H.; Shores, M. P. Inorg. Chem. 2010, 49, 7891-7991.
2) Bowman, A. C.; Sproules, S.; Wieghardt, K. Inorg. Chem. 2012, 51, 3707-3717.
INOR 669
Synthesis of dual gunction ansa-metallocene ligands via hydrocarbon radical anion coupling of 1,3-diphenyl-6(alkyl/aryl)fulvenes
Max M. Lai, Gary J. Balaich, [email protected], Scott T. Iacono. Department of Chemistry, United States Air Force
Academy, Colorado Springs, Colorado, United
States
The synthesis of a pool of 1,3-diphenyl-6-(R)pentafulvenes was carried out. Reaction with hydrocarbon radical anions
resulted in reductive coupling of the fulvenes to give bridged metallocene ligand precursors. In the case of R groups such
as 3-pyridyl, bipyridyl, 4-4-(pyridyl)phenyl, 2- and 3-furyl, the ligands contain ancillary coordinating functionality, important
for incorporation of the bridged metallocene unit into supramolecular frameworks. Characterization of the fulvenes and
bridged structures was carried out using 1H and 13C NMR, gc/ms, single crystal X-ray, and thermal analytical techniques
(TGA, TGA-DTA/DSC). The effect of the pentafulvene structure with differing R groups on the structure of the ansa-ligand
precursors as well as on the resulting metal containing compounds will be discussed.
INOR 670
Novel binuclear pincer ligands for applications in catalysis and energy
Chandra Mouli Palit1, [email protected], Oleg Ozerov2. (1) Chemistry,
Texas A&M University, College Station, Texas, United States (2) Chemistry, Texas AM University, College Station, Texas,
United States
Pincer ligands have been very instrumental and sometimes imperative for transition metal mediated catalysis. One of the
more recent point of focus in this domain have been binuclear pincer complexes and utilizing the availability of two
different metal sites to design and implement novel transformations. In this report, we describe the synthesis and
characterization of novel binulcear pincer ligands and their transition metal complexes. The proximity and relative
orientation of the two pincer sites with respect to each other has been varied by varying the nature of the linkers used to
connect them. Pendant amine linkers have also been incorporated to facilitate proton shuttles between metal centers and
the pendant amine. A set of ligands has been designed so that the two ligands share one aromatic π electron cloud to
facilitate redox interactions between the metals centers. Ligands based on known chromophores have also been
incorporated into our studies since a combination of transition metals and chromophoric ligands has recently proven
useful in applicaion such as photovoltaics, polymer LEDs etc.
INOR 671
Probing molecular and electronic structures of conjugated molecular linkers based on linear polyazulenic motifs
Nathan Erickson, [email protected], Andrew D. Spaeth, Mikhail V.
Barybin. Chemistry, University of Kansas, Lawrence, Kansas, United States
The azulenic scaffold, a polar 10 π-electron nonbenzenoid aromatic unit composed of fused 5-and 7-membered sp2carbon rings, is an attractive motif for designing new materials supporting charge delocalization and transport at the
nanoscale.1 In this work, molecular and electronic structures of a family of linear polyazulenic linkers were addressed by
Density Functional Theory and several theoretically favorable designs have already been realized experimentally. This
presentation will highlight
characteristics of azulenic molecular linkers as a function of junction groups (X), number of azulenic units (n), substituents
at 1,3-positions of the azulenic scaffolds (R), as well as the 2,2’-, 6,6’- and/or 2,6’-connectivities of the azulenic motifs, as
illustrated in the figure below.
INOR 672
1
Scheetz, K. J., Spaeth, A. D., Vorushilov, A. S., Powell, D. R., Day, V. W., Barybin, M. V.
Chem. Sci., 2013, 4, 4267-4272.
Efficient synthesis and heterobimetallic complexation of the first aromatic πlinker featuring mercapto and
isocyano junctions within the same molecule
Jason Applegate2, [email protected], Nikolay Gerasimchuk 1, Mikhail V. Barybin2. (1)
Missouri State Univ, Springfield, Missouri, United States (2) Chemistry, University of Kansas, Lawrence, Kansas, United
States
The azulenic motif constitutes a nonbenzenoid bicyclic aromatic framework composed of fused 5- and 7-mebered carbon
rings. Azulene derivatives are attractive building blocks in the design of functional materials for a variety of optical and
electronics applications, particularly because of their remarkably small and tunable HOMO-LUMO gaps and
complementary nature of the frontier molecular orbitals of the azulenic scaffold, which may be viewed as a molecular
diode. This presentation will highlight the efficient synthesis of a linear azulenic π-bridge terminated with one mercapto
and one isocyano termini. Heterobimetallic complexation of this linker with low-valent transition metal centers, as well as
molecular and electronic structures of the resulting organometallic platforms, will be discussed.
INOR 673
Synthesis of ambiphilic nickel-silyl complexes for cooperative small molecule activation
Christian A. Olivares, [email protected], Matthew T. Whited. Chemistry, Carleton College, Northfield, Minnesota,
United States
The synthesis of late-metal Silylene complexes is promising for cooperative small
molecule activation via frustrated intramolecular σ or π.bonds which lead to highly reactive lewis acidic and lewis basic
adjacent sites. We are studying nickel species which are stabilized by tridentate pincer ligands. Reactivity at the metal
center is expected to be nucleophilic in nature and can be tuned via different electron donating substituents on the
phosphine pincer ligands. Current results using NiBr2 DME adduct and bis(2-(dicyclohexylphosphino)phenyl)silane have
yielded a stable Ni(II) complex in which we lose HBr and DME. With the addition of heat or in the presence of base, we
see the loss of the silicon-hydride and believe to be making a bromo-silyl complex. Current experiments include
abstracting the halide from nickel as well as abstracting the hydride from the silicon center in order to reach the nickelsilylene.
INOR 674
E-H bond activation and hydrofunctionalization via bifunctional bis(pyridylimino)isoindolate complexes
Jacob B. Geri1, [email protected], Nathaniel K. Szymczak2. (1) Chemistry, University of Michigan, Deltona, Michigan,
United States (2) Chemistry, University of Michigan, Ypsilanti, Michigan, United States
A new bifunctional pincer ligand framework bearing pendent proton-responsive hydroxyl groups was prepared and
metalated. The complexes exhibited protonation-state dependent hydrofunctionalization of diverse polar bonds using
hydrogen and pinacolborane. Mechanistic experiments and theoretical calculations revealed a crucial role of the pendent
hydroxyl groups for catalytic activity.
INOR 675
Synthesis of ligand platforms for metalloenzyme mimics
Olivia M. Crandell, [email protected], Joel A. Dopke. Alma College, Alma, Michigan, United States
Hydrogenases are metalloenzymes known to catalyze the equilibrium between molecular hydrogen and H+, as well as the
reversible reduction of CO2 to CO. Our goal is to synthesize sulfur and nitrogen-rich ligand systems to allow access to
functional models of the hydrogenase active site. Thus, we sought to synthesize the heterocycle 2,3-benzo-1,7-dithia-4azacyclononane as well as acyclic, imine-based ligand platforms with the intention of complexing iron and nickel centers.
Ligands and ligand precursors were characterized by 1H and 13C NMR, and IR spectroscopy, and their preferences for
heterocycle formation and metal complexation were investigated.
INOR 676
Synthesis and characterization of novel complexes coordinated to bipyridine derivatives with acidic functional
groups
Sheri Lense, [email protected], Andrew Wildish. Chemistry, University of
Wisconsin Oshkosh, Oshkosh, Wisconsin, United States
The addition of acidic functional groups to 2,2’-bipyridine derivatives allows for the synthesis of coordination complexes
with multiple functionalities. If the acidic functional group is positioned near the metal center, the acidic functionality can
interact with a substrate bound to the metal center and potentially enhance the binding affinity of the metal center for the
substrate or facilitate further reactivity of the substrate. The position of the acidic functionality relative to the metal center
can be an important factor in determining whether and how the acidic functionality can interact with a substrate bound to
the metal center. For example, for an octahedral complex, in some cases it may be preferable for the acidic functionality
to be positioned near an equatorial position, and in other cases it may be preferable for the acidic functionality to be
positioned near an axial position. The position of the acidic functionality relative to the metal center can be controlled by
altering the design of the 2,2’-bipyridine ligand. We are exploring the coordination of both known and novel 2,2’- bipyridine
derivatives containing acidic functional groups to create novel multifunctional coordination complexes. Through X-ray
crystallography and spectroscopy, we are determining how the design of the 2,2’bipyridine ligand affects the position of
the acidic functional group relative to the metal center. Additionally, we are determining how the presence of the acidic
functional groups affects the reactivity of substrates bound to the metal center.
INOR 677
Organometallic complexes of 1,6-methano[10]annulene: DFT investigation of dtructure and dynamic behavior
Denis A. Kissounko1, [email protected], Yuri F. Oprunenko2, Igor P.
Gloriozov2. (1) Science, Arapahoe Community College, Littleton, Colorado, United States (2) Chemistry, Moscow State
University, Moscow, Russian Federation Although the organometallic π-complexes of annulenes have been known for
decades, there have been no conclusive studies on the potential degenerative η 6,η6- or η4,η4Inter-Ring Haptotropic
Rearrangement (IRHR) in such complexes. In this work we present the first detailed DFT-study for the η6,η6-IRHR of
several transition metal organometallic derivatives of 1,6-methano[10]annulene. The study shows the facile η 6,η6-IRHR
transition through the η3- transition stage. The geometries of molecules, transition states and intermediates were fully
optimized by means of density functional theory (DFT) calculations. The PBE functional and the scalar-relativistic theory
were used in the calculations. The full electron basis sets L1 were used, where L1 stands for double set size. Corrections
for zero-point energies were calculated in the harmonic approximation. Stationary points on the potential energy surface
(PES) were identified by analyzing Hessians. The thermodynamic functions (Gibbs activation energies, G) at 298 K were
calculated using the approximation of restricted rotator and harmonic oscillator. Reaction paths were found by the Intrinsic
Reaction Coordinate (IRC) method. Based on the DFT study, the close resemblance of 1,6-methano[10]annulene to
naphthalene ligand was demonstrated.
INOR 678
Room temperature carbon-sulfur bond activation by a reactive (dippe)Pd fragment
Lloyd Munjanja1, [email protected], William Brennessel1, William D. Jones1. (1) University of Rochester,
Rochester, New York, United States (1) Department of Chemistry, University of Rochester, Rochester, New York, United
States
Reactivity of [Pd(dippe)(μ-H)]2 and [(μ-dippe)Pd]2 dippe = 1,2bis(diisopropylphosphino)ethane) towards C-S bonds in thiophene derivatives and thioethers is investigated leading to CS bond activation products. The thiapalladacycles derived from thiophenic substrates were fully characterized by 1H, 31P,
13C NMR, elemental analysis and X-ray diffraction. The stability of the C-S insertion products was probed by performing
competition experiments which follow the thermodynamic stability order: (dippe)Pd(κ2-C,S-benzothiophene) >
(dippe)Pd(κ2-C,S-dibenzothiophene) > (dippe)Pd(κ2-C,S-thiophene). Reactivity of the thiapalladacycles with small
molecules such as H2, CO and alkynes was investigated.
INOR 679
Synthesis and characterization of ruthenium(II) complexes with hydrosilyl pincertype ligands
Binh D. Nguyen, [email protected], Matthew T. Whited. Department of
Chemistry, Carleton College, Northfield, Minnesota, United States
As part of our project to devise novel late-metal systems for cooperative small-molecule activation and catalysis, we have
prepared and characterized a series of ruthenium(II) complexes with tridentate bis(phosphine)/dihydrosilyl ligands.
Ligands and metal complexes were synthesized in an inert atmosphere and characterized by infrared and multinuclear
NMR spectroscopies as well as X-ray crystallography. Several ruthenium complexes were synthesized reproducibly and
preliminary reactivity was investigated, including several processes leading to modification of the silyl donor or ruthenium
center. Current efforts are directed at understanding these transformations and developing new reactivity with small
molecules such as H2 and CO2.
INOR 680
Scope, limitations, and mechanistic aspects of a regioselective acylation of cycloplatinated complexes
Jeffrey S. Carroll, [email protected], Hannah G. Woolard, [email protected], Rob Mroz,
Charles A. Nason, Shouquan Huo, [email protected]. Department of Chemistry, East Carolina University, Greenville, North
Carolina, United States
Recently we have discovered a regioselective acylation of cyclometalated platinum complexes in which the
cyclometalated platinum complex (2a, X = NH, R = H, Figure 1) was selectively acylated by reacting with acetic anhydride
in acetic acid. It was further discovered that the acylated complex (3a, X = NH, R = H) could also be directly prepared in a
cascade intramolecular cycloplatination-acylation reaction by reacting the organic ligand (1a, X = NH, R = H) with
potassium tetrachloroplatinate in a mixture of acetic acid and acetic anhydride. In this presentation, we will report the
scope and limitations of this newly discovered reaction. First, optimization of the reaction conditions indicated that a
number of other solvents such as acetonitrile, benzonitrile, 1,2dichloroethane, and chlorobenzene could be used in the
acylation reaction. The reaction showed great tolerance to various linker groups (X = O, S, CH 2, etc.), as well as many
electron donating/withdrawing groups (R). The full results of acylation experiments with a library of substrates will be
reported. The use of other electrophiles, such as benzoyl chloride, benzyl bromide, allyl bromide, methyl iodide, and
crotonyl chloride, will also be reported. Mechanistic implications will be discussed from these experimental results.
Figure 1. General scheme.
INOR 681
Organosilver scaffolds for small-molecule activation and catalysis
Brandon Tate1, [email protected], Chelsea M. Wyss1, Joseph P. Sadighi1,
Jenna T. Nguyen1,2, John Bacsa3, Leslie Gelbaum1. (1) School of Chemistry and
Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States (2)
Department of Chemistry, Washington and Jefferson College, Washington,
Pennsylvania, United States (3) X-Ray Crystallography Center, Emory University, Altanta, Georgia, United States
Sterically demanding, strongly σ-basic N-heterocyclic carbenes (NHCs) support silver complexes with unique structures
and reactivity, providing opportunities for organosilver-mediated activation of small molecules and catalysis relevant to
renewable energy and chemical synthesis. Hard-soft mismatched fluoride and alkoxide complexes of silver heterolytically
activate dihydrogen, forming hydride clusters which are remarkably robust yet sufficiently hydridic to reduce carbon
dioxide, opening the door for organosilver-catalyzed production of formic acid via hydrogenation of CO 2 under mild
conditions. Thermally stable NHC-supported alkyl, aryl, vinyl, alkynyl, and perfluoroalkyl complexes of silver exhibit
interesting structures and reactivity. Facile insertion of CO 2 into NHC-supported silver-carbon bonds offers the potential
for the utilization of CO2 as a chemical feedstock. 109Ag NMR spectroscopy reveals the magnitude of 109Ag–107Ag nuclear
spin coupling and provides insight into the extent of silver-silver bonding and the electronic structure of key oligonuclear
complexes. The isolation and characterization of catalytic intermediates by NMR and X-ray diffraction crystallography
provides insight for rational optimization of catalytic systems and the development of new systems for homogeneous silver
catalysis and silver-mediated transformations.
INOR 682
Synthesis, structure, and cross-coupling of 2,3,5-tris(4ferrocenylethynylphenyl)boroxine
Denis A. Kissounko3, [email protected], Victor P. Dyadchenko2, Vladimir N.
Okulov2, Marina A. Dyadchenko2, Andrei V. Churakov4, Li Wang1, Dmitri A.
Lemenovskii2. (1) Zhejiang University, Hangzhou, China (2) Chemistry, Moscow State
University, Moscow, Russian Federation (3) Science, Arapahoe Community College,
Littleton, Colorado, United States (4) Institute of Inorganic Chemistry, Moscow, Russian Federation
The direct 4-bromophenylethynylferrocene I was synthesized by direct alkynylation of ferrocene. Further reaction of I with
n-butyllithium and then with tri-n-buthylborate yielded 2,3,5-tris(4-ferrocenylethynylphenyl)boroxine derivative II. Boroxine
II crystallizes in chiral triclinic space group P1 with two independent molecules within the unit cell. The core B3O3
fragments represent almost regular hexagons with B-O-B and O-B-O angles varying from 118.6(8) to 122.5(7)°. The
central (-CºC-C6H4-B)3O3 units are planar within 0.237(7) Å. In both molecules, one of three unsubstituted C 5H5 ligands
are rotationally disordered over two positions with approximately equal occupancies. In the cell, the independent
molecules are related by pseudosymmetry centers. The closest molecules are linked in pairs by p-p stacking interactions
(Fig. 6). However these interactions do not affect dramatically acetylene triple bond because its stretching vibrations in II
are observed at 2206 cm -1, which is only slightly below two stretching bands 2220 and 2235 cm -1 found in I. Different rodlike ferrocenyl derivatives containing acetylene moiety were prepared by palladium catalyzed cross-coupling reactions of I
and aromatic iodides. The boroxine derivative II may serve as precursor for new rod-like ferrocenylmesogens.
INOR 683
Complexation studies of bipyridine aza-crown macrocycles
Benjamin Carpenter, [email protected], Marc Harris. Lebanon Valley
College, Annville, Pennsylvania, United States
Alkali metal ion complexation by classic crown ether and azacrown host molecules has been well documented in the
literature. These systems display excellent selectivity for various ions based on steric requirements and hard-soft
interactions. Recently, functionalized versions of these macrocycles have been reported that either display enhanced ionbinding, improved selectivity, or an external response to report successful binding. To this end, a series of bipyridine
containing azacrown-ether macrocycles were synthesized by reacting a dibromo-substitued bipyridine unit with a preorganized polyamine. These azacrown-bipyridine analogues are expected to display similar ion selectivity and binding
strength based on the size, number of donor atoms, and type of donor atoms created by the bipyridine host pockets. In
addition, by metallating the outwardly directed bipyridine units with photoactive transition metal centers these complexes
may function as chemosensory devices that visibly display the encapsulation of small cationic molecules and ions. This
paper reports the synthesis and complexation study of the azacrown-bipyridine macrocycles.
INOR 684
Synthesis of bis(diorganodithiocarbamato)iron(II) by the thermal decomposition of cisdicarbonylbis(diorganodithiocarbamato)iron(II)
James E. Coffield, [email protected], Norman V. Duffy. Wheeling Jesuit Univ, Wheeling, West Virginia, United States
Thermal decomposition of cis-dicarbonylbis(diorganodithiocarbamato)iron(II) often initiates with the loss of one or both
carbonyl ligands, depending on the nature of the dithiocarbamate ligand. Previous work at Wheeling Jesuit University
using thermal gravimetric analysis has indicated the presence of stable intermediates produced during the thermal
decomposition of cis-dicarbonylbis(diorganodithiocarbamato)iron(II) complexes. In particular, evidence suggests the
possible formation of monocarbonylbis(diorganodithiocarbamato)iron(II) and
bis(diorganodithiocarbamato)iron(II). Bis(diorganodithiocarbamato)iron(II) is not stable in air and its synthesis usually
requires multiple steps under an inert atmosphere. In contrast, the cis-dicarbonylbis(diorganodithiocarbamato)iron(II) is air
stable and can be synthesized from triiron dodecacarbonyl without the use of an inert atmosphere. Only the final thermal
decomposition step requires an inert atmosphere. The cisdicarbonylbis(diorganodithiocarbamato)iron(II) can be easily
stored in air until needed as a precursor for the synthesis of bis(diorganodithiocarbamato)iron(II). This study also
investigates the relationship between the nature of the dithiocarbamate ligand and the thermal decomposition process.
INOR 685
Computed structures of cyclic platinum-metal-directed self-assembled complexes
Eric A. Buchanan1, [email protected], Josef Michl1,2. (1) University of Colorado, Boulder, Colorado, United
States (2) Institute of Organic Chemistry and Biochemistry, Prague, Czech Republic
Ground state structures have been found using density functional theory method PBE0/Def2-TZVPP//PBE0/Def2-SVP for
the cis,trans isomers of platinum-metaldirected self-assemblies of four pyridine or acetylene terminated rods and four
Pt(PR3)2 centers. The favored geometries are determined by a competition between ring strain and electronic strain at the
Pt centers. The former generally grows and the latter decreases as the number of trans-Pt centers is augmented. For
cationic complexes containing two bipyridyl and two biphenyl rods, with a +1 charge on each Pt center, a puckered
structure with all four Pt centers cis is found to be 37.6 kcal/mol lower in energy than the isomer with all four Pt centers
trans. For neutral complexes with four biphenyl rods and neutral Pt centers, the highly ring-strained planar circular alltrans isomer lies 17.17 kcal/mol below the all-cis isomer.
INOR 686
Dual-metal NHC phenanthroline complexes
Amanda J. Landis, [email protected], John O. Hoberg. Department of Chemistry,
University of Wyoming, Laramie, Wyoming, United States
Organometallic complexes of the type shown in Figure 1 have been synthesized. The M 1 center is designed to be a lightharvesting component and exhibits strong absorbance in the visible spectrum. The M2 center, coordinated to the Nheterocyclic carbene moiety, functions in known catalytic processes. Metals include but are not restricted to (M 1=Ru) and
(M2=Pd, Ni). Synthesis of these complexes and preliminary data dealing with their chemistry will be presented.
Figure 1. Dual-metal NHC phenanthroline complex.
INOR 687
Fused siloles for electronic applications
David A. Lee, [email protected], Thomas A. Schmedake. UNC-Charlotte, Charlotte, North Carolina, United States
Novel fused siloles have been synthesized and characterized for electronic applications. Lithiation of 3,3’-dibromo-4,4’bipyridine and subsequent reaction with dichlorodimethylsilane leads to the corresponding dipyridosilole (eqn. 1). The
dipyridosilole can be converted to the methyl viologen analog by reacting it with methyl triflate. The silylene-bridged
methyl viologen is stable and can be isolated, but it hydrolyses upon exposure to air. Cyclic voltammetry and
spectroelectrochemical analysis of the silylene bridged methyl viologen species are underway.
Similar chemistry is being exploited to synthesize silicon analogs of spiro-OMeTAD. Tetrabrominated-spirosilabifluorenes
have been synthesized by lithiation of the corresponding dibromodiiodobiphenyl followed by reaction with SiCl4.
Subsequent amination of these species is currently being explored.
eqn. 1
INOR 688
Actinide high-nitrogen chemistry
Kevin P. Browne3, [email protected], David E. Morris2, Brian L. Scott5, David
E. Chavez1,7, Andrew T. Nelson6, Bryce C. Tappan7, Jaqueline L. Kiplinger8, Jacqueline Veauthier4,8. (1) C920, Los
Alamos National Laboratory, Los Alamos, New Mexico,
United States (2) Chemistry Division, Los Alamos National Laboratory, Santa Fe, New
Mexico, United States (3) Chemistry Division: Inorganic, Isotope, and Actinide
Chemistry Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United
States (4) Los Alamos National Laboratory MS C920, Los Alamos, New Mexico, United
States (5) Materials Physics and Applications Division, Los Alamos National Laboratory,
Los Alamos, New Mexico, United States (6) Materials Science and Technology Division,
Los Alamos National Laboratory, Los Alamos, New Mexico, United States (7) Weapons Experiments Division, Los Alamos
National Laboratory, Los Alamos, New Mexico, United States
We have been exploring the aqueous and non-aqueous coordination chemistry of thorium and uranium with nitrogen-rich
ligands. The reaction chemistry of these new complexes has been examined and their electronic structure investigated
using X-ray analysis, DSC, TGA, electronic absorption spectroscopy and electrochemistry. Recent developments in this
area of chemistry will be presented.
INOR 689
New synthetic pathways to (C5Me5)2ThS5
Jacquelyn M. Dorhout2,3, [email protected], Alejandro Lichtscheidl3, Nicholas
E. Travia3, Peter K. Dorhout1, Brian Scott3, Ken Czerwinski2, Jaqueline L. Kiplinger3. (1)
College of Arts Sciences, Kansas State University, Manhattan, Kansas, United States
(2) UNLV Dept of Chemistry, Las Vegas, Nevada, United States (3) Los Alamos National Laboratory, Los Alamos, New
Mexico, United States
Three new synthetic pathways involving either S 8 or K2S5 to form the organoactinide polysulfide
Cp*2ThS5 have been developed. Cp*2ThS5 has been characterized by 1H NMR spectroscopy and single
crystal x-ray crystallography and the parameters compare to literature values. The synthesis of a new
complex, Cp*2Th(SMe)2, is presented here for the first time, along with full characterization by 1H and
13C
NMR spectroscopy, elemental analysis, and x-ray crystallography. This complex is used as one of the
precursors to Cp*2ThS5.
INOR 690
Actinide metal fluorides: Synthesis, characterization, and chemistry
Alejandro G. Lichtscheidl1,2, [email protected], Marisa J. Monreal1, Kevin Browne2,
David E. Morris3, Brian Scott1, Andrew Nelson1, Jaqueline L. Kiplinger1. (1) Los Alamos National Laboratory, Los Alamos,
New Mexico, United States (2) Chemistry Division:
Inorganic, Isotope, and Actinide Chemistry Group, Los Alamos National Laboratory, Los
Alamos, New Mexico, United States (3) Chemistry Division, Los Alamos National
Laboratory, Santa Fe, New Mexico, United States
We have been developing new routes for preparing well defined uranium and thorium fluoride complexes. The reaction
chemistry of these new complexes has been examined and their electronic structure investigated using X‐ray analysis,
electronic absorption spectroscopy and electrochemistry. Recent developments in this area of chemistry will be
presented.
INOR 691
Molecular chemistry of thiophene with actinide complexes
Nicholas E. Travia1, [email protected], Aaron W. Pierpont6, Beau J. Barker1, Kevin
Browne3, Marisa J. Monreal1, Enrique R. Batista4, John M. Berg7, Richard L. Martin2,
Ryzard Michalczyk1, David E. Morris5, Brian Scott8, Marianne P. Wilkerson9, Jaqueline L. Kiplinger1. (1) Los Alamos
National Laboratory, Santa Fe, New Mexico, United States
(2) MS B214 Theoretical Div, Los Alamos Natl Lab, Los Alamos, New Mexico, United
States (3) Chemistry Division: Inorganic, Isotope, and Actinide Chemistry Group, Los
Alamos National Laboratory, Los Alamos, New Mexico, United States (4) Theoretical
Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States (5)
Chemistry Division, Los Alamos National Laboratory, Santa Fe, New Mexico, United
States (6) Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Reactions of thiophene with transition metal complexes have been studied for decades as models for hydrodesulfurization
(HDS). While actinide metals have been used in heterogeneous HDS catalysts, no studies with molecular actinide
complexes have been reported. In this talk, new chemistry between thiophene and molecular actinide complexes will be
presented.
INOR 692
Low-temperature solution processing of stibnite thin films
Carrie L. McCarthy, [email protected], Richard L. Brutchey. Department of Chemistry LJS 260, University of Southern
California, Los Angeles, California, United States
Sb2S3 and Sb2Se3 both have optimal band gaps (1.7 eV and 1.2 eV, respectively) and absorption coefficients to make
them efficient light absorbers for thin film solar devices. Low temperature solution processing of these earth abundant
materials is a cost effective technique for the fabrication of next generation solar cells. Furthermore, solid solutions
comprised of these two semiconductors have been shown to have band gaps that are more ideal for photovoltaic
applications than those of the individual semiconductors.
In the work that will be presented, a solvent mixture of mercaptoethanol and ethylenediamine is utilized to quickly dissolve
bulk Sb2S3 or bulk Sb2Se3 into a solution processable ink under ambient conditions. This ink is then spin-coated onto a
conducting substrate and subsequently thermalized to produce a thin film of the crystalline material, as verified by XRD
and XPS. The optical band gaps of the annealed films, measured by UV-Vis absorption, are in good agreement with the
literature values. TGA data shows complete loss of combustible organic components of the ink at annealing temperatures.
Solid solutions of Sb2SxSe3-x are synthesized by dissolving stoichiometric amounts of the individual semiconductors into
the same ink followed by heat treatment to obtain the crystalline solid solutions, which are verified by XRD.
INOR 693
Synthesis and characterization of metal chalcogenide nanomaterials for potential application in nanoelectronic
devices
Adam J. Biacchi, [email protected], Angela R. Hight Walker. Nanoelectronics
Group, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland,
United States
Solution-based methods of material synthesis have attracted much attention due to the ease of process scalability,
diversity of products accessible, and ability to tune their properties through prudent selection of reaction conditions. In
particular, the synthesis of semiconductor nanomaterials in solution has proven an effective means of tailoring their
characteristics, including shape, size, and composition. Here we report several new syntheses of nanoscale metal
chalcogenide (MX) and dichalcogenide (MX 2) semiconductors using solution routes. Further, we thoroughly interrogate
the crystallographic and optoelectronic properties of these materials to display that they are size-, shape-, and structuredependent. A detailed comparison of these nanomaterials to their bulk analogues, as well as each other, suggests they
collectively could find utility in the tunable design of next-generation nanoelectronic devices.
INOR 694
Colloidal cinnamic acid capped PbSe quantum dots: Solution phase ligand exchange, thin film formation, and
electrical conductivity for photovoltaic applications
Daniel M. Kroupa3,2, [email protected], Alan Sellinger1, Matthew C.
Beard3. (1) Dept Chemistry Geochemistry, Colorado School of Mines, Golden,
Colorado, United States (2) University of Colorado - Boulder, Boulder, Colorado, United States (3) National Renewable
Energy Lab, Golden, Colorado, United States
As synthesized PbSe quantum dots (QDs) are natively passivated with insulating oleate ligands that must be removed or
replaced to form charge conducting QD films for photovoltaic applications. Conventionally, this is accomplished in a layerby-layer fashion where thin films of oleate capped QDs are exchanged with short-chain thiols, such as ethanedithiol, to
build up a film of desired thickness. As an alternative, we developed ligand exchange strategies to terminate the PbSe
QDs with cinnamic acid and fluorinated cinnamic acid derivatives in solution. These small, conjugated ligands undergo
complete exchange with native oleate ligands and allow for one-step film formation from concentrated solutions using spin
coating or drop casting techniques. The different ligands are characterized by their degree of electron donating ability and
thereby impact the optical and electrical properties of the resulting QDs and QD films. We compare carrier mobilities for
oleate-capped, cinnamic acid capped, and ethanedithiol capped QD films and correlate results with film morphology and
other spectroscopic observations.
INOR 695
Probing structure-property relationships at the nanoscale: Combined X-ray and spectroscopic methods for the
study of colloidal cadmium selenide
Alexander Beecher, [email protected], Peter Chen, Zachariah Norman,
Jonathan S. Owen. Chemistry, Columbia University, New York, New York, United
States
Understanding the fundamental properties of a material requires a precise knowledge of structure; however, structural
determination of nanomaterials remains a major challenge due to the combination of heterogeneity and long-range
disorder in most samples. By measuring the diffuse scattering of powder samples and performing pair-distribution function
(PDF) analysis, we have gleaned key insights allowing us to correlate structural changes with changes in composition and
electronic properties of colloidal cadmium selenide (CdSe) nanocrystals. Drawing upon a combination of PDF and other
spectroscopic techniques, we have determined the formulas and structures of small CdSe clusters, investigated the
reconstruction of nanocrystal surfaces as a function of ligand coverage, and characterized the relationship between CdSe
grain growth and charge mobility, among other studies. These results represent a convincing demonstration of PDF’s
value and versatility for understanding structure-property relationships in nanocrystal materials.
INOR 696
Effect of precursor reactivity on nickel phosphide nanocrystal synthesis
Himashi Andaraarachchi1, [email protected], Javier Vela-Becerra2. (1) Chemistry, Iowa State University, Ames,
Iowa, United States (2) Dept of Chem, Iowa State University, Ames, Iowa, United States
In order to explore how precursor molecular structure and reactivity will affect the final outcome of the nickel phosphide
synthesis, we have used phosphites as phosphorous precursors instead of most commonly used trioctyl phosphine or
trioctylphosphine oxide. Triethyl phosphite, trimethyl phosphite, triisopropyl phosphite, tributyl phosphite and triphenyl
phosphite were used. We have synthesized nickel phosphide nanocrystals and monitored the reaction over time. We were
able to produce different phases of nickel phosphides (Ni2P and Ni12P5) within different time scales depending on the
reactivity of the phosphite. They were characterized by UV-Vis absorption, powder x-ray diffraction and transmission
electron microscopy. Understanding of how molecular structure affects the chemical reactivity of molecular precursor
enables highly predictable and reproducible synthesis of colloidal nanocrystals with specific compositions and properties
for precise applications.
INOR 697
Rational control over electron-transfer using inorganic cluster-anions directly coordinated to anatase-TiO2 cores
in water
Manoj Raula, [email protected], Ira Weinstock. Department of Chemistry , BenGurion University of Negev, Beer
Sheva, Israel
An unprecedented role for metal-oxide cluster-anions (polyoxometalates, or POMs) as covalently coordinated inorganic
ligands for individual anatase nanocrystals, giving isolable anionic clusters uniquely positioned between molecular
macroanions and traditional colloidal nanoparticles. Sodium salts of the water-soluble polyanionic structures are obtained
by reacting amorphous TiO2(s) with the 1-nm size mono-defect Keggin ion, Na(8-n)[α-Xn+W 11O39], Xn+ = P5+, at 170 °C, after
which, an average of 55 ± 10 α-PW 11O397- anions are found as pentadentate “capping” ligands for complexed
Ti(IV) ions still linked—via their sixth coordination site—to 6-nm single-crystal anataseTiO2 cores. Multiple lines of
evidence reveal that the POM-protecting ligands are covalently bound to the surface of anatase nanocrystals, giving clear
solutions over a wide range of pH values, and allowing for repeated precipitated and re-dissolution in water. EDS and
XPS data suggest that numerous POMs are associated with each 7-nm anatase nanocrystals, and high-resolution TEM,
cryogenic-TEM, and HAADF-STEM images clearly show POM-protecting ligands bound to anatase surfaces. Solid state
NMR, ESI-MS and MALDI-mass spectra unambiguously identify the covalently-bound POM-protecting ligands as
TiPW 11O405--derived clusters. The surface-bound clusteranions are reversible electron acceptors, whose reduction
potentials shift to more negative values by simply changing the central heteroatom, Xn+, from P5+ to Si4+. Hence, just as
POM cluster-anions control the reactivities of metal centers in molecular complexes, directly coordinated POM ligands
with tunable redox potentials could provide options for rationally controlling the reactions of TiO2 nanocrystals. This control
over charge separation and electron-transfer pathways within the composite materials has been utilized to control release
of H2 gas from water-splitting using methanol as sacrificial agents under UV conditions.
INOR 698
Electrocatalytic and photocatalytic hydrogen evolution using iron phosphide nanoparticles
Juan F. Callejas1, [email protected], Joshua M. McEnaney1, Carlos G. Read3, Raymond
E. Schaak2. (1) Chemistry, Penn State University, State College, Pennsylvania, United
States (2) Pennsylvania State University, University Park, Pennsylvania, United States
Platinum is the most widely used catalyst for the hydrogen evolution reaction (HER), however its high cost and scarcity
have motivated the search for alternative non-noble metal catalysts. Nanostructured transition-metal phosphides have
recently emerged as Earth-abundant alternatives to platinum, requiring low overpotentials to reach high current densities.
Iron phosphide (FeP) nanoparticles have been found to be highly active electrocatalysts for the HER. Titania-supported
FeP nanoparticles are able to facilitate the HER photocatalytically. The addition of FeP to the growing library of transitionmetal phosphides that have been identified as active HER catalysts continues to provide useful insights into the structural
and compositional factors that lead to high HER activity.
INOR 699
Amorphous MoP and WP nanoparticles as electrocatalysts for the hydrogen evolution reaction
Joshua McEnaney, [email protected], Raymond E. Schaak. Chemistry,
Pennsylvania State University, State College, PA, United States Minor Outlying Islands
Electrocatalytic water dissociation for the production of hydrogen provides an energy dense, clean burning fuel source.
The hydrogen evolution reaction (HER), however, is most effectively catalyzed by platinum, an expensive and rare metal.
This presentation will describe and evaluate amorphous MoP and WP nanoparticles as catalytically active alternatives to
platinum for the HER. These materials required overpotentials of only -90 and -120 mV respectively to produce an
operationally relevant current density of 10 mA cm -2 in 0.5 M H2SO4. This presentation will also briefly highly recent efforts
to investigate other materials for the HER, including Ni2Si and FeP. All of these HERactive materials were previously
identified to be active hydrodesulfurization (HDS) catalysts, and therefore were explicitly targeted as potential HER
catalysts, given the postulated correlation between the pathways by which HDS and HER catalysts function.
INOR 700
Fast kinetics of Ni-doped nanomagnesium for hydrogen storage and the difficulty of effectively comparing
material performance in literature
Daniel J. Shissler1, [email protected], Max B. Braun2, Sarah J. Fredrick1,
Amy L. Prieto3. (1) Chemistry Department, Colorado State University, Fort Collins,
Colorado, United States (2) Chemistry, Colorado State University, Fort Collins,
Colorado, United States (3) Chemistry Department C210, Colorado State University, Fort Collins, Colorado, United States
Storing hydrogen by means of forming a hydride material is a topic of great interest. Magnesium is one such material
because of its high gravimetric energy density of 7.6 wt% H 2. However, bulk magnesium exhibits slow rates of
hydrogenation and dehydrogenation. Primary methods of increasing the kinetic performance are reducing the size of the
Mg, thus reducing diffusion lengths, and adding catalysts to reduce the activation energy of hydrogenation and
dehydrogenation. For this purpose, we have prepared 32 nm Mg nanoparticles doped with 5% Ni as a catalyst. The
prepared particles reach 85% hydrogenation and dehydrogenation within 25 seconds and 60 seconds, respectively.
However, as impressive as these results are, they are meaningless without knowing the conditions at which the particles
were cycled. Hydrogenation and dehydrogenation rates are dependent upon the temperature and pressure at which the
material is cycled, so comparing values reported in literature on different materials is troublesome if the materials were
cycled under varying conditions. But if comparing the same material with differing catalysts, activation energies of the
hydrogenation and dehydrogenation may be calculated to determine which catalyst had more greatly reduced the
activation energy. The most widely used method of doing so is fitting the cycling data with the Johnson-Mehl-Avrami
(JMA) model of nucleation and growth. However, the use of the JMA equation is done without regard to the situation in
which the JMA equation is intended to model (the transition of a single solid phase into another) and the assumptions
made by the model (random nucleation and low surface to bulk material ratio). Because of this oversight, activation
energies reported may not indicate which material performs better. To this end, the conditions for hydrogenation and
dehydrogenation cycling should be standardized and an accurate model of phase transitions of nanoparticles needs to be
formulated.
INOR 701
Solution synthesized magnesium nanoparticles: The role of synthesis, particle size, structure, and dopant
incorporation on hydrogenation kinetics
Max B. Braun1, [email protected], Dan Shissler3, Amy L. Prieto2. (1)
Chemistry, Colorado State University, Fort Collins, Colorado, United States (2)
Chemistry Department C210, Colorado State University, Fort Collins, Colorado, United States (3) Prieto group, Fort
Collins, Colorado, United States
Solution based synthesis of magnesium nanoparticles for hydrogen storage allows for significant control over particle size
and catalyst incorporation. Differences in solution based synthetic procedures, as well as the dopant chosen, can lead to
significant changes in hydrogenation and dehydrogenation kinetic ability. By decoupling the role of nanoparticle size and
the role of the incorporated dopant through experimental control and kinetic modeling, we can further understand
mechanistic pathways in hydrogenation reactions. Low temperature solution synthesized magnesium nanoparticles doped
with 5% Ni (by weight) show a significant improvement in the dehydrogenation kinetics with respect to the undoped
particles. Additionally, by studying and comparing the local structure of the magnesium and nickel (or other dopants)
through EXAFS and pair distribution function analysis, a better experimental understanding of the catalysts role can be
established and compared with theoretical work within the literature.
INOR 702
Efficient method of cleaning hydrogen sulfide at ambient temperature and pressure for hydrogen storage
Xuemin Li2, [email protected], Rachel Morrish4, Colin A. Wolden1, Yongan Yang3, [email protected]. (2) Chemistry,
Colorado School of Mines, Golden, Colorado, United States (3) Dept Chem Geochem Coolbaugh Hall 120B, Colorado
School of
Mines, Golden, Colorado, United States (4) Colorado School of Mines, Golden, Colorado, United States
Hydrogen sulfide (H2S), a major pollutant released by both natural sources and industrial activities, is hazardous to human
health, corrosive to equipment, and poisonous to catalysts. Its cleaning has long been cost-ineffective, because the
prevailing abatement technologies (such as the Claus Process) convert H 2S to S and H2O, two low-value chemicals.
Driven by establishing an energy-and-environmental sustainable society, new technologies that can clean H 2S efficiently
and effectively are highly desirable. It has been widely recognized that one solution is to recover the hydrogen in H 2S to
produce H2 gas, an extremely valuable chemical for many industries. Motivated by this attractive blueprint, tremendous
efforts have been invested to develop a practical technology. However, although a variety of approaches have been
attempted, they all essentially operate a variant of equation H2S --> H2 + S(s), which is thermodynamically unfavorable and
significantly endothermic. This inevitable hurdle means that all such techniques will eventually face the same challenge
the current techniques are facing—the economic unviability, regardless what form of energy is used to execute this
reaction.
Thus, a promising strategy is to design an energy-favorable reaction by liberating the hydrogen in the gas form or storing it
in high-value chemicals while producing valuable S-containing products. Such a process must be scalable and ideally
capable of being executed at near ambient conditions without the need for significant energy input. Our presentation will
demonstrate such an approach that alters thermodynamics to work in our favor by reacting H 2S with a sodium
metalorganic complex. The H2S-cleaning process has been observed to be simple, spontaneous, complete, and
irreversible; the treatment can be conducted at ambient conditions and treat any concentration of H 2S; and high value H2
and Na2S (the cathode material for Na-S batteries) have been produced. The presentation will focus on the study of
reaction mechanism and kinetics.
INOR 703
Electrochemistry of neodymium in chloride-fluoride melts
Dmitriy A. Shuklin1, Ilya B. Polovov1, [email protected], Mikhail V. Chernyshov2, Vladimir A. Volkovich2, Oleg I.
Rebrin1. (1) Department of Physical and Chemical
Methods of Analysis, Ural Federal University, Ekaterinburg, Russian Federation (2) Rare Metals and Nanomaterials, Ural
Federal University, Ekaterinburg, Russian Federation
Development of innovation industrial technologies is inseparably connected with modernization of methods of
manufacturing high-technology products. One example of such products is metallic neodymium that is in a high demand in
the world market. Currently there are increasing demands for neodymium due to its enhanced consumption in production
of high-energy magnets, batteries and superalloys. Electrolysis of molten salts is one of the possible methods of
neodymium production. Mixed chloride-fluoride electrolytes are the most prospective media for neodymium production in
terms of their physico-chemical properties and organization of the process. Detailed information concerning the
mechanisms and kinetics of the electrode reactions in such media is required to enhance the technological parameters of
the process.
In the current work the electrochemical behavior of neodymium was studied in LiClNdF3 and CaCl2-NdF3 melts in a wide temperature range (from 750 to 1050 0С). Neodymium concentration was varied
from 4 to 20 wt. % NdF3. The investigation was carried out using stationary (chronopotentiometry) and non-stationary
(cyclic and square-wave voltammetry) techniques. The methods of galvanostatic and potentiostatic electrolysis were
applied in a special series of experiments.
It was found that electroreduction of neodymium in all studied melts proceeds in a single three-electron step.
Electrokinetic parameters of neodymium reduction at different temperatures and Nd(III) concentrations were estimated.
The limiting current densities were determined. They predictably increase with increasing temperature and concentration
of neodymium in the melt. It is shown that increase of polarizing current density above the limiting value leads to the
secondary reduction of neodymium by
alkali and alkaline-earth metals formed on the cathode. Increasing temperature results in increase of physical solubility of
neodymium in the studied electrolytes. High solubility of neodymium in the melt causes noticeable decrease of current
efficiently during electrolytic production of neodymium.
It was found that metallic neodymium is formed in the liquid state when the electrolytic reduction was performed at 1050
0C. Solubility of the liquid metal in the molten electrolytes was estimated under the experimental conditions. It was
confirmed that the electrolytic reduction of neodymium at high temperatures simplifies separation of the metal from
quenched electrolyte.
INOR 704
Functionalization of Si(111) photocathodes: Interplay between steric spacing of molecular linkers and ALDdeposited metal oxide films
Ryan Pekarek2, [email protected], Michael J. Rose1. (1) Dept of Chemistry,
University of Texas at Austin, Austin, Texas, United States (2) Department of
Chemistry, Austin, Texas, United States
The investigation of effective methods for semiconductor functionalization is necessary for the development of Solar Fuels
devices. An ideal semiconductor junction would incorporate both molecular components (chemical functionality,
attachment, and tuning) and materials components (protection, conduction, and enhanced light absorption) to maximize
the desired utility of the device. In this work, both aspects (and their interplay) have been investigated by the attachment
of small molecules to a surface, followed by
ALD methods to generate metal oxide ultra-thin films (5-100 Å). First, fluorine-capped
(organic) phenyl units with varying silyl-ether substituents (OSiR3; R = CH3, iPr, Ph, Hexyl) were attached to a Si(111)
surface. Their surface coverages were determined using X-ray photoelectron spectroscopy (using 'F' as a marker),
indicating an increasing extent of coverage from Ph < iPr < Hexyl < (no silyl ether). The surfaces coverages range from
5%-35%, which is attributable to the varying extents of steric repulsion between attached molecules. The surface quality
and stability of these samples is investigated by electrochemistry (CV) and surface recombination velocity (SRV). Ongoing
work is focused on developing conditions for deprotection of the surfaceattached silanes, which will be used as nucleation
sites for ALD-based (inorganic) protecting layers such as aluminum or titanium oxides (Al 2O3, TiO2). The possibility for a
specific, molecular interaction between these two components may allow for enhanced electronic effects (i.e. band-edge
tuning, electron transfer kinetics, or ET enhancement with metal nanoparticles). Overall, this investigation will a