Single Crystal to Single Crystal Polymerization of a Self

Article
pubs.acs.org/crystal
Single Crystal to Single Crystal Polymerization of a Self-Assembled
Diacetylene Macrocycle Affords Columnar Polydiacetylenes
Weiwei L. Xu,† Mark D. Smith,† Jeanette A. Krause,§ Andrew B. Greytak,† Shuguo Ma,‡ Cory M. Read,†
and Linda S. Shimizu*,†
†
Department of Chemistry and Biochemistry and ‡College of Engineering and Computing, University of South Carolina, Columbia,
South Carolina 29208, United States
§
The Richard C. Elder X-ray Crystallographic Facility, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221,
United States
S Supporting Information
*
ABSTRACT: This manuscript describes a single-crystal-tosingle-crystal polymerization of the dihydrate of diacetylene 1
(1·2H2O) to give an unusual polydiacetylene (PDA) structure
that consists of aligned nanotubes, with each covalently
bonded nanotube having two parallel PDA chains that run
parallel down opposite sides of a channel defined by the
macrocycle. Each PDA nanotube is connected with four other
columns via amide hydrogen bonds with an N-(H)···O
distance of 2.888(4) Å. Such well-ordered polymers should
display quasi-one-dimensional electronic structures and may be of interest for the formation of highly conductive organic
materials. We obtained the 1·2H2O form in bulk, which was polymerized by heating. Powder X-ray diffraction suggests that bulk
PDA powder is single phase and displays a similar structure as the PDA single crystals. Furthermore, we showed that PDA
crystals absorbed I2 vapor. We believe that this unique PDA structure, which is amenable to property control via adsorbed guests,
will be an attractive one for investigating charge-transfer doping in PDA-based organic electronic materials. We also observed two
additional crystal forms, including 1·MeOH, which also shows a columnar assembly, and a tetrahydrate 1·4H2O that shows water
tetramers that link four cycles into a 2D sheet structure.
■
separated by a fixed distance. The crystal consists of bundles of
many highly oriented PDA nanotubes, which are connected
through amide N-(H)···O hydrogen bonds to four neighboring
nanotubes (Figure 1d). Such well-ordered polymers with quasione-dimensional electronic structures may be of interest for the
formation of highly conductive materials due to the high
density of states at the band edge and minimal disorder, as has
been seen in the case of doped semiconducting carbon
nanotubes.20,21
PDAs are of interest due to their robust nature and
potentially tunable structures. They consist of a chain of
alternating ene−ynes that show sensitivity to environmental
conditions including temperature, pH, host−guest interactions,
and solvent. PDAs display a relatively low band gap (∼ 2.0
eV).22−24 Bulk PDA films display fast photoconduction
properties and large nonlinear responses and are amenable to
doping, which dramatically increases their conductivity.22−32
Because of their remarkable environmental sensitivity, PDAs
have been incorporated into peptide nanostructures,33−45
helical polymers,40−42 liquid crystals,46,47 thin films,48−50 and
sensors.51−57
INTRODUCTION
Carbon nanotubes1−3 and carbon nanofibers are widely studied
because of their attractive electrical,4−7 mechanical,8,9 and
thermal properties.10 Carbon rich tubular and fibrous structures
have also been made via self-assembly or by polymerization of a
variety of synthetic monomers.11−13 Polyacetylene14,15 and
polydiacetylene (PDA) are of particular interest given their
conductivity and optical properties. PDAs have potential
applications in organic solar cells and as sensors.16−18
Diacetylene monomers are readily synthesized with a wide
variety of functional groups. They can be assembled into
columns or fibers and polymerized to give PDAs. Our group
previously reported the synthesis of a diacetylene macrocycle
that crystallizes as a dihydrate (1·2H2O) and undergoes
polymerization upon heating to likely afford oligo- or
polydiacetylenes as indicated by Raman spectroscopy and
solid-state nuclear magnetic resonance (NMR).19 In this
manuscript, we report that the dihydrate can be polymerized
to a PDA through a single crystal to single crystal (SCSC)
process. This process proceeds readily in smaller crystals and
shows that significant atomic movement occurred within the
crystal during the polymerization process. The resulting
covalent column contains two PDA chains that are aligned
and run parallel down the sides of the nanotube column
(Figure 1b). The two polymers of a single tube are rigid and
© 2014 American Chemical Society
Received: September 16, 2013
Revised: January 22, 2014
Published: January 23, 2014
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Figure 1. Diacetylene macrocycle 1 assembles from solution. (A) Molecular structure of 1. (B) The dihydrate 1·2H2O can be polymerized in a
SCSC process to give a PDA crystal. (C) PDA microcrystal generated by spin-coating a 1.0 mg/mL macrocycle 1 solution on the Si wafer followed
by thermal treatment (190 °C for 3 h) to induce the polymerization. (D) Individual PDA nanotubes are connected through amide bonds to four
neighboring nanotubes.
structure as the PDA single crystals. PDA crystals were doped
with I2 vapor to afford a ratio of 1:14 iodine (calculated as I2) to
PDA monomer. Comparison of X-ray photoelectron spectroscopy (XPS) survey scans of the PDA and PDA·I2 complexes
showed new peaks after iodine exposure, which were attributed
to triiodide I3− and pentaiodide I5−.
Finally, we report the formation of microcrystals by spincoating a solution of 1 (1.0 mg/mL) on silicon wafers, glass,
and quartz slides, and then thermally treating the assemblies at
190 °C for 3 h to facilitate polymerization. In general, the SEM
imaging of the microcrystals on silicon substrates after
polymerization gave good contrast (Figure 1c). The initial
concentration of the spin-coated solution appears to influence
the average length of the needles. Such microcrystalline PDAs
may have advantages over larger crystals and could show faster
equilibration with guests, be amenable for transport measurements, and may be more suitable for integration into thin film
organic electronic devices.68
PDAs are typically synthesized from diacetylenes by UV
irradiation or thermal polymerization, which can occur in either
solution or in the solid state. However, following polymerization, the PDA polymers are often insoluble, making full
structural characterization challenging. Wegner first reported
that precise preorganization of diacetylene units within crystals
facilitated a topochemical polymerization.58,59 When neighboring diacetylene units are prealigned with a repeat distance (d1)
of 4.9 Å, a C1−C4 contact distance (d2) of 3.5 Å, and a tilt
angle of 45°, the polymerization may be initiated by thermal or
photochemical treatment. Supramolecular interactions have
been used to assemble diacetylene monomers into structures
that are prone to subsequent topochemical polymerization.60−65 For example, Goroff and Lauher utilized halogen
bonding to preorganize diacetylenes within a cocrystal.
Subsequent polymerization gave poly(diiododiacetylene).66 A
recent report by Fowler and Lauher utilized a polyether
diacetylene macrocycle, which assembled into several polymorphic crystals. One polymorph stacked into columnar
structures with a repeat distance of 4.84 Å. Slow annealing
over 35 days gave a SCSC transformation to the PDA.67 Our
group has been investigating the use of diacetylene-containing
macrocycles that self-assemble to give tubular supramolecular
polymers and can subsequently be polymerized to give covalent
tubular polymers.19 Herein, we report three crystal forms of
macrocycle 1. We observed the SCSC polymerization of 1·
2H2O to afford the PDA, when annealed at 190 °C under inert
atmosphere (N2 gas) for 12 h. We also observed a methanol
solvate 1·MeOH with a distinctive blue color and a tetrahydrate
(1·4H2O). Neither of these crystalline forms underwent the
SCSC polymerization.
This manuscript also investigates the properties of the
crystalline PDA and examines the absorption of iodine by the
PDA crystals and powder. We readily obtained the bulk crystals
of 1·2H2O and polymerized them by heating. Powder X-ray
diffraction of the PDA samples prepared in bulk suggests that
bulk PDA powder is single phase and displays a similar
■
EXPERIMENTAL METHODS
All chemicals were purchased from Sigma-Aldrich or VWR and used
without further purification. 1H and 13C NMR were recorded on
Varian Mercury/VX 300 and 400 NMR spectrometers. Both the solidstate 13C CP-MAS and FSLG-HETCOR experiments were run on a
Bruker AVANCE III-HD 500 MHz spectrometer equipped with a
Doty Scientific 4 mm MAS probe. The CP-MAS was run with a 2 ms
contact time with linear ramping on the 1H channel. The FSLGHETCOR experiment had the contact time set at 200 μs. Sample
rotation was 8.2 kHz, and data acquisition was performed with 1H
decoupling using 100 kHz field and SPINAL64 modulation. Raman
spectra were recorded with a J Y Horiba LabRam system using a 632
nm excitation laser. The solid-state UV−visible spectroscopic data
were collected by using a Perkin-Elmer Lambda 35 UV−visible
scanning spectrophotometer equipped with an integrating sphere. The
DSC data of 1·2H2O was collected on a TA Q2000 differential
scanning calorimeter.
Synthesis. Macrocycle 1 was synthesized as reported.19 Characterization data: 1H NMR (400 MHz, DMSO-d6): δ 9.14 (t, J = 4.8 Hz, 4
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Table 1. Crystal and Refinement Data for Macrocycle 1 (1·2H2O, 1·MeOH, and 1·4H2O) and for the PDA Crystals
empirical formula
formula weight
T (K)
crystal system
space group
a (Å)
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
Dc (mg mm−3)
μ (mm−1)
F(000)
reflections collected, unique
Rint
GOF on F2
R1 [I > 2σ (I)]
wR2 (all data)
Δρmin,max (e Å−3)
C28H20N4O4·2H2O
C28H20N4O4·CH3OH
C28H20N4O4·4H2O
PDA crystal
C28H24N4O6
512.51
150(2)
monoclinic
P21/c
4.9860(2)
14.6944(7)
16.8680(8)
90
96.905(1)
90
1226.89(10)
2
1.387
0.099
536
17823, 2522
0.0343
1.035
0.0418
0.1102
0.30/−0.20
C29H24N4O5
508.52
150(2)
triclinic
P1̅
4.5301(10)
11.579(3)
12.321(3)
111.787(3)
99.823(3)
97.184(3)
578.7(2)
1
1.459
0.102
266.0
7750, 2841
0.0357
1.088
0.0989
0.2975
0.87/−0.56
C28H28N4O8
548.54
295(2)
triclinic
P1̅
8.9148(5)
9.4752(5)
9.8948(5)
110.584(1)
108.502(1)
104.815(1)
675.53(6)
1
1.348
0.100
288.0
7430, 2200
0.0443
0.893
0.0406
0.0920
0.17/−0.16
C28H20N4O4
476.48
100(2)
monoclinic
P21/c
4.895(3)
14.586(8)
16.285(9)
90.00
104.125(11)
90.00
1127.7(11)
2
1.403
0.096
496.0
12582, 1821
0.1021
1.072
0.0599
0.1460
0.35/−0.22
190 °C induced the polymerization process and afforded PDA
microcrystals.
Scanning Electron Microscopy. PDA microcrystals prepared by
spin-coating 1.0 and 1.5 mg/mL macrocycle 1 solution on Si wafers,
glass, and quartz slides followed by thermal treatment were next
examined by SEM. SEM images of PDA microcrystals were taken by
using a TESCAN Vega-3 SBU pressure scanning electron microscope.
PXRD Studies. The powder X-ray diffraction experiments were
performed on a Rigaku D/Max 2100 Powder X-ray Diffractometer
(Cu Kα radiation), and the experiments were run using a zero
background slide on which the sample was gently pressed. The data
were collected at increments of 0.04 degrees, and an exposure time of
5 s/step in the angular range of 5−60 degree 2-theta at ambient
temperature.
Iodine Doping. An iodine loading chamber (Figure S15 of the
Supporting Information) was used to expose the sample to iodine
vapor while deterring I2 crystallization. In the chamber, the iodine
partial pressure PI2 was controlled to be half of PI2*, which represents
the vapor pressure of iodine at ambient temperature. The sample of
PDA crystals (5 mg) was exposed to iodine vapor in the chamber at 27
°C for 0−96 h to afford a doped sample PDA·I2. The iodine doping
reached saturation at ∼48 h. The degree of doping was measured using
a TA SDT Q600 thermogravimetric analysis (TGA).
X-ray Photoelectron Spectroscopy (XPS). XPS was conducted
using a Kratos AXIS Ultra DLD XPS system, which was equipped with
a monochromatic Al Kα source. The monochromatic Al Kα source
was operated at 15 keV and 120 W, and the pass energy was fixed at 40
eV for the detailed scans. The binding energy was calibrated using an
Ag foil with Ag3d5/2 set at 368.21 ± 0.025 eV for the monochromatic
Al X-ray source.
H), 8.31 (s, 2 H), 7.92 (d, J = 7.6 Hz, 4 H), 7.56 (t, J = 7.6 Hz, 2 H),
4.16 (d, J = 4.8 Hz, 8 H) ppm.13C NMR (75 MHz, DMSO-d6): δ
165.8, 134.0, 130.3, 128.7, 126.3, 76.2, 66.2, 29.4 ppm.
Crystallization Conditions. The X-ray quality crystals of 1·2H2O
were obtained readily by a slow evaporation of solvents. The
diacetylene macrocycle (10 mg) was first dissolved in 5 mL MeOH/
CH2Cl2/H2O 45:55:5 (v:v:v), and then the macrocycle solution was
filtered through a syringe filter. Slow evaporation in the dark afforded
colorless needlelike crystals; however, the crystals turned reddish in
color over several days when exposed to light. Rare bluish crystals of
the methanol solvate 1·MeOH (<1%) were found approximately in
every fifth crystallization attempt from the solution that produced 1·
2H2O. These crystals darkened in color after exposure to light and
were physically separated. Clear short rodlike crystals of the
tetrahydrate 1·4H2O were formed by slow evaporation of a solution
of 1 (10 mg) in 10 mL of 50:50:15 (v:v:v) MeOH/CH2Cl2/H2O. The
color of the tetrahydrate did not change, even after exposure to light
for months.
X-ray Diffraction. The crystallographic data of 1·2H2O, 1·4H2O,
and the PDA crystals were collected on a Bruker SMART APEX
diffractometer with Mo Kα radiation. The intensity data for 1·MeOH
were collected at 150 K on a D8 goniostat equipped with a Bruker
APEXII CCD detector at Beamline 11.3.1 at the Advanced Light
Source (Lawrence Berkeley National Laboratory) using synchrotron
radiation tuned to λ = 0.7749 Å. The data for all crystals are
summarized in Table 1.
Polymerization. Polymerizations were carried out by heating
monomer crystals under an inert atmosphere (N2 gas) at 190 °C for
12 h. The crystals of 1·2H2O showed a SCSC transformation. The
SCSC nature of the transformation was verified by performing the Xray intensity data collections before and after the thermal polymerization process using the same crystal. The bulk PDA crystals displayed
a dark purple/brown color. By examining the bulk PDA crystals with
solid-state 1H−13C COSY (HETCOR) NMR (Figure S6 of the
Supporting Information), no monomer was detected. We subjected
the other crystal forms to the same polymerization conditions.
Preparation of Microcrystals. Microsize crystals were prepared
by spin-coating 1.0 and 1.5 mg/mL macrocycle solutions at a rate of
1000 rpm for 90 s on Si wafers, glass, and quartz slides using a SCS
6800 Spin Coater. Further thermal treatment of the microcrystals at
■
RESULTS AND DISCUSSION
Previous work demonstrated that macrocycle 1 assembled into
columnar structures and underwent a thermal reaction to give
oligo- or polydiacetylenes.19 Although the crystals examined
cracked lengthwise during this process, both the assembled
macrocycle 1 and its subsequent PDA remained highly
crystalline. Both assembled 1 and the polymerized PDA
showed 1·2H2O gas adsorption isotherms indicative of
microporous systems. We set out to investigate if the
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polymerization could be carried out in a SCSC process. Our
first objective was to scale both the synthesis and crystallization
of macrocycle 1. The key step was an Eglinton acetylene−
acetylene coupling reaction that could be carried out on a 0.5−
1 g scale; however, optimal purification of the product required
column chromatography, which proved to be the limiting step.
With gram quantities of the material in hand, we studied
crystallization conditions for 1. The 1·2H2O crystal form was
readily and reproducibly obtained by slow evaporation of 1 (2
mg/mL in 45:55:5 MeOH/CH2Cl2/H2O) and exhibited a
structure identical to that previously reported structure.19
Crystals of 1·2H2O were initially colorless but gradually turned
reddish after prolonged exposure to ambient light. A minor
crystalline form 1·MeOH was occasionally observed in small
quantities (<1%) under the same crystallization conditions and
was blue in color. The tetrahydrate crystals 1·4H2O were from
a solution of 1 (1 mg/mL) in MeOH/CH2Cl2/H2O 50:50:15
(v:v:v). We will examine each of these structures in more detail
below.
The X-ray analysis of the abundant dihydrate crystal (1·
2H2O) was described in our previous report.19 We present the
structure again as this manuscript reports its subsequent SCSC
polymerization. The 1·2H2O crystal is monoclinic with a P21/c
space group with unit cell dimensions of a = 4.99 Å, b = 14.69
Å, c = 16.87 Å, β = 96.90°, and a unit cell volume of 1226.89 Å3
(Table 1). Macrocycle 1 lies on a crystallographic inversion
center. It is relatively planar and stacks into columns with a
repeat distance (d1) of 4.99 Å and a tilt angle of 41.6°; the
orientation angle of two adjacent cycles is 63.9° (Figure 2a).
for polydiacetylene (Figure S5 of the Supporting Information).68,69 The observation of these Raman PDA bands, while
the majority of the crystal is monomer by X-ray diffraction,
illustrates that Raman is not necessarily a good method for
assessing conversion.
A small needlelike single crystal (0.52 × 0.05 × 0.04 mm3)
was subjected to X-ray analysis, and its structure was confirmed
as the dihydrate 1·2H2O. The crystal was then heated at 190 °C
under an inert atmosphere (N2) for 12 h, which induces a loss
of interstitial water molecules and facilitates the polymerization
to afford the PDA. Aside from a slight darkening in color, the
small crystal appeared identical to the unheated crystal (Figure
3, inset). A second X-ray data collection was performed on the
Figure 3. Single-crystal-to-single-crystal (SCSC) transformation of
dihydrate 1·2H2O to a PDA. (A) The initial dihydrate 1·2H2O
structure highlights the observed repeat distance d1 = 4.99 Å, the
contact distance d2 = 3.58 Å, the tilt angle θ = 41.6° and the
orientation angle Φ = 63.9°. (B) Upon heating at 190 °C for 12 h, the
diacetylene macrocycles undergo a SCSC polymerization process to
afford a PDA.
heated crystal, and the polymeric structure C28H20N4O4 (repeat
unit) was confirmed (Figure 3b). Although significant atomic
movement occurred within the crystal, the single-crystal-tosingle-crystal transformation took place without a change in
space group (P21/c for both forms). The unit cell dimensions
changed slightly to a = 4.90 Å, b = 14.59 Å, c = 16.29 Å, β =
104.12° (Table 1). The unit cell volume correspondingly
decreased from 1226.89 to 1127.70 Å3, which is primarily due
to loss of the interstitial water molecule guests and the creation
of hydrogen bonds between polymeric columns. The
asymmetric unit consists of half of one polymeric formula
unit, which is situated about a crystallographic inversion center.
Comparison of the two structures shows that upon reaction, the
relatively planar macrocycle 1 becomes a more folded repeat
unit in the PDA and displays a smaller interior cavity. Figure 4a
highlights the reacted monomer unit within the columnar PDA.
Figure 4b shows a top view of a single monomer unit
imbedded in a polymer, which runs the length of a single
column. The PDA carbonyl oxygens O(1) and O(1)ii point into
the center of the cycle and display intrapolymeric hydrogen
bonds with amides from adjacent monomeric units within the
same column (Figure 4c). The intramolecular hydrogen bond
distance N(2)−H(2)···O(1) distance is 2.860(3) Å. Since the
monomer in the PDA no longer has a planar structure, it is
easier to describe the PDA using a new cyclic repeat unit
defined in Figure 4c. The column is built by the repeat of a new
cycle. Each cycle (plane α) is linked by two poly(ene−yne)
triple bonds on each side. The new cycle in PDA consists of
phenyl rings, amides, and methylene groups of the original
macrocycle connected through two carbon double bonds. The
cavity size of PDA was estimated as 4.9 × 2.3 Å (accounting for
van der Waals radii) by measuring the distance between two
Figure 2. Dihydrate 1·2H2O crystals obtained by slow evaporation of
1 from 45:55:5 MeOH/CH2Cl2/H2O. (A) Columnar assembly of 1
displays neighboring macrocycles that self-assemble into a columnar
structure through amide−amide hydrogen bonding with an N−(H)···
O distance of 2.81 Å. (B) Solid-state UV−vis absorption spectrum of
crystal I shows two bands with λmax = 288 and 571 nm.
The macrocycle self-assembles into a columnar structure
through amide−amide hydrogen bonding with an N-(H)···O
distance of 2.81 Å. Two sets of diacetylene units are aligned
along each side of the column. The diacetylene moieties in
adjacent macrocycles have a contact distance (d2) of 3.58 Å
and display a supramolecular organization that is close to the
ideal topochemical polymerization requirements for polymerization.58,59 Although both colorless and reddish crystals were
examined, no differences were detected by X-ray diffraction.
However, the reddish 1·2H2O crystals do show a new broad
UV−vis absorption band with λmax = 571 nm (Figure 2b),
which may indicate the presence of a small percentage of oligo
or polydiacetylene on the surface of the crystal. This is further
supported by the Raman spectrum of the crystals, which shows
two characteristic resonance bands at ∼1506 and ∼2107 cm−1
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the starting material was measured as 177.1° and 173.6°,
respectively. Upon polymerization, the corresponding bond
angles of polymer were shifted to 118.1° and 116.4°.
Our previous work on the heat-treated 1·2H2O crystals
demonstrated that the oligo or polydiacetylene show gas
adsorption isotherms indicative of a microporous material;19
analysis of the X-ray structure of the PDA suggests that the
interior channel of the columns has a very small diameter. The
column size of PDA was estimated to be 4.9 × 2.3 Å
(accounting for van der Waals radii). Figure 5b displays a spacefilling model of PDA crystals, which indicates that individual
columns are tightly packed with no obvious room left for guest
molecules; however, close-packed systems may expand to
absorb guests.70−74 For example, self-assembled materials may
modulate weak noncovalent interactions in order to absorb
guests.75−82 Prior work on our pyridyl bis-urea columns with
unsatisfied exterior acceptors demonstrated that the columns
may expand like clay to absorb guests in between the strong
columnar assembly.83,84 Thus, we are currently investigating the
uptake of guests by these PDA materials to determine if the
guests are indeed absorbed in the channels or are alternatively
taken up in between neighboring PDA columns.
New Crystal Forms of 1. While most of our work was
carried out on the dihydrate 1·2H2O crystal form of 1, we
observed two additional forms: a methanol solvate 1·MeOH
and a tetrahydrate 1·4H2O. Distinctive, pale blue block crystals
of 1·MeOH were obtained under the same crystallization
conditions from a solution of 1 (2 mg/mL) in 45:55:5 MeOH/
CH2Cl2/H2O; however, these crystals were unusual and only
observed in small quantities (<1%). This crystal form displays a
smaller, triclinic unit cell with a volume of 578.7 Å3, which is
approximately half the volume observed for monoclinic 1·
2H2O. The asymmetric unit consists of half of one disordered
C28H20N4O4 cycle situated about a crystallographic inversion
center (Figure 6a) and a fractionally populated, disordered
solvent region, which was modeled as methanol. The disorder
of the cycle is caused by the presence of two opposite
conformations of the −C(O)NH− group (C8, O2, and N2)
and also affects the phenyl ring atoms C2−C7 and atoms C12−
C14 of the attached −CH2CC− grouping. The macrocycles are
not planar but bent, with the two aryl units pointing on
opposite sides of a plane formed from the diacetylenes (Figure
6b).
Figure 4. Views from the PDA single crystal: (A) A side view of the
PDA column highlights one monomeric unit. (B) Top view of the
monomer unit. (C) Intrapolymeric N(2)−H(2)···O(1) hydrogen
bonds shown as red dashed lines. Bonds connected to not shown
neighboring monomeric units in the polymeric column were labeled as
yellow dots. (D) Packing diagram of polymeric columns looking down
from the a axis. The columns are joined via N(1)−H(1)···O(2)
hydrogen bonds.
phenyl hydrogens that point into the center of the cycle and the
distance between double bonds on either side. Each column
consists of two polydiacetylene chains. These individual
columnar polymers are organized in three dimensions by a
series of hydrogen bonds. Each polymeric column is
surrounded by six columns and interacts with four other
columns via N(1)−H(1)···O(2) intermolecular hydrogen
bonds of 2.888(4) Å (Figure 4d).
To highlight the movement that occurs over the course of
the polymerization, we juxtaposed the two crystal structures in
Figure 5a. The PDA is depicted on top and the dihydrate
monomer is the partially transparent structure. The major
motion of the monomer during polymerization appears to be
the folding of the macrocycle plane as the methylene carbons
pivot. The C9−C10−C11 and C12−C13−C14 bond angle of
Figure 5. (A) The background drawing shows the crystal structure of the diacetylene monomer in the dihydrate 1·2H2O crystals. The foreground
drawing shows the structure of the PDA. All the molecules were cut in half for clarity. The macrocycle rotates by a pivot of methylene carbons. The
C9−C10−C11 bond angle changed from 177.1° to 118.1°, and the C12−C13−C14 bond angle changed from 173.6° to 116.4°. The repeat distance
d1 of the adjacent cycle is essentially unchanged (4.986 Å in 1·2H2O to 4.985 Å in the PDA). (B) Packing diagram of the polymeric columns of the
PDA looking down the a axis. The center column is shown as a spacefilling model to emphasize the small channel, which is approximately 2.3 × 4.9
Å in diameter.
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Figure 7. Views from the structure of 1·4H2O. (A) Monomer
structure. (B) Five diacetylene macrocycles; the water tetramers link
four other cycles into a 2D sheet structure. (C) Side view of a column
formed in the 1·4H2O. The columns have a large offset with respect to
the column axis. The tilt angle θ is 69.0°, and the shortest distance
between acetylene carbons on adjacent cycles is 6.34 Å. (D) Two
adjacent diacetylene macrocycles with the shortest intercolumnar
contact distance of 3.78 Å.
Figure 6. Views from the X-ray structure of 1·MeOH. (A) Detail of
the disorder of the cycle, each disorder component has a population of
50%, only O1, N1, C1, and C9−C11 are not disordered. (B) Single
diacetylene macrocycle 1. (C) Columnar assembly of macrocycle 1.
The N−(H)···O hydrogen bonding distance is 2.710(3) Å. (D) Solidstate UV−vis absorption spectrum of 1·MeOH shows two bands λmax
= 286 and 630 nm. Disordered MeOH incorporated in the macrocycle
was removed for clarity.
The macrocycles do not form direct hydrogen bonds
between neighboring macrocycles. Instead, macrocycles
assemble through hydrogen bonds to intervening water
molecules (Figure 7b). The water tetramers link the cycles
into a 2D sheet in which the cycles pack parallel to each other.
Macrocycle 1 further stacks to form columns. However, the
columns in the tetrahydrate crystals have a large offset with a
steep tilt angle θ of 69.0° with respect to the column axis
(Figure 7c). The shortest distance of acetylene carbons on
adjacent cycles is 6.34 Å, a distance large and unfavorable for
diacetylene polymerization. The shortest intercolumnar distance between acetylene units is ∼3.78 Å (Figure 7d).
We used differential scanning calorimetry (DSC) to
investigate the thermal transitions of the 1·4H2O crystals.
(Figure S11 of the Supporting Information). The tetrahydrate
crystals showed two irreversible endothermic transitions at
∼100 °C and ∼118 °C, respectively. The first transition likely
corresponds to the loss of water as observed by TGA (Figure
S12 of the Supporting Information). A single exothermic peak
was seen at 270 °C. The integration of the peak gave an
enthalpy of 275 kJ/mol. We are currently investigating the
crystal transition that occurs at 118 °C and the possible
polymerization. In comparison, the dihydrate 1·2H2O bulk
crystals displayed an endothermic transition at 90 °C, which
corresponded to a loss of water and multiple irreversible
exothermic reactions between 180−260 °C.19 Integration of
these peaks gave a polymerization enthalpy of 250 kJ/mol,
approximately twice the value measured for polymerizations of
crystalline diacetylenes (150−165 kJ/mol).85
Properties of the PDAs. We observed the SCSC
polymerization of the dihydrate 1·2H2O form to give the
PDA crystal. To investigate the purity and homogeneity of the
PDAs formed by heating of bulk crystals, we used powder X-ray
diffraction (PXRD). After annealing, the bulk crystals turned a
dark purple/brown color. The PDA crystals were ground into
powder form and examined by PXRD. The observed PXRD
The individual macrocycles stack into columns through the
formation of hydrogen bonds [N(H)···O; D−A = 2.710(3) Å,
DHA angle = of 138.4°] between the nondisordered amides
(Figure 6c) of neighboring macrocycles. The repeat distance
(d1) is 4.53 Å in 1·MeOH, and the contact distance (d2) of the
reacting carbon atoms is ∼3.70 Å.
Given that the diacetylene units in the 1·MeOH crystals are
organized close to ideal topochemical polymerization requirements,58,59 we subjected the crystal to the same annealing
conditions. The crystal was heated at 190 °C under an inert
atmosphere (N2) for 12 h and turned dark purple/brown. We
observed a Raman spectrum typical for an oligo- or
polydiacetylene,68,69 with characteristic resonance bands at
∼1500 and ∼2100 cm−1 for polydiacetylene (Figure S8 of the
Supporting Information); however, as observed earlier, these
bands are not indicative of the yield. However, the sample also
showed a broad absorption band between 200 and 700 nm,
which also suggests the formation of some oligodiacetylenes or
PDA (Figure S9 of the Supporting Information).
Slow evaporation of 1 from a different solvent mixture (1
mg/mL in 50:50:15 MeOH/CH2Cl2/H2O) afforded colorless
short rodlike crystals of the tetrahydrate 1·4H2O with the
formula C28H20N4O4·4H2O. The data crystal was a twocomponent nonmerohedral twin. The compound crystallizes in
the triclinic system. The space group P1̅ (no. 2) was confirmed
by the successful solution and refinement of the structure. The
asymmetric unit consists of half of one C28H20N4O4 cycle that
is situated about a crystallographic inversion center and two
independent water molecules (Figure 7a). The molecular
structure showed that there are four water molecules
incorporated within each cycle, two trapped in the cavity of
the macrocycle and another two positioned above and below
the macrocycle plane.
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pattern (Figure 8a, red line) closely matched with the pattern
simulated from coordinates of the PDA single crystal (Figure
Figure 9. Comparison of XPS survey scans: (A) PDA crystals;
expansion ∼400 eV area is shown in the inset. (B) Iodine-treated PDA
crystals; expansion between 600 and 650 eV is shown in inset.
Figure 8. (A) Observed powder X-ray diffraction (PXRD) pattern of
bulk PDA crystals (red) and simulated PXRD pattern calculated from
PDA single crystal (blue). (B) UV−vis absorption spectrum of PDA
suspension in MeCN.
deconvoluted into two peaks at 618.3 and 620.4 eV. This
indicated the existence of two structures of iodine in the PDA·I2
complex, and these two peaks are attributed to triiodide I3− and
pentaiodide I5−, respectively.89−92 In addition, amide carbonyl
and methylene C1s peaks shifted to 287.6 and 285.5 eV after
iodine incorporated into PDA, and a new O1s peak was also
found at 531.1 eV. The chemical shift of CO C1s and O1s
photoemission to the lower binding energy area suggests that
the carbonyl in PDA might associate with the polyiodide
anions.
In order to investigate the interaction of the polyiodide
anions with the PDA, we compared the FT-IR, solid-state 13C,
and Raman spectra of the PDA and PDA·I2 complexes (see
Figures S17 and S18 of the Supporting Information). Only
Raman spectroscopy displayed differences between the PDA
and the PDA·I2 complex (Figure 10). The Raman spectrum of
8a, blue line) with no discernible additional peaks, suggesting
that the polymerization proceeds cleanly in the bulk material.
We note that several peaks from the simulated pattern were
observed with decreased intensity in the experimental pattern.
These intensity differences are due to severe preferred
orientation of the sample and are not uncommon for
polycrystalline polymer samples.86 These observations suggest
that the bulk PDA powder is a single phase and displays a
similar structure as the PDA single crystals.
UV−vis absorption and Raman spectra provided further
evidence that the bulk crystals also form the PDA upon heating.
Figure 8b shows the UV−vis absorption spectrum of heated
bulk 1·2H2O measured as a suspension in MeCN. Two broad
absorption bands overlapped in the visible light range, λmax =
571 and 620 nm, were attributed to the presence of different
lengths of PDA in our sample.87,88 The Raman spectrum of the
bulk PDAs (Figure S14 of the Supporting Information) showed
two intense resonance bands belonging to the ene in the
poly(ene−yne) of the polymer at ∼1506 and ∼2107 cm−1.68,69
Iodine Doping. Iodine doping has been used to modulate
the properties of PDAs and increase conductivity.24,32 We
investigated the doping of our PDAs with iodine using an
apparatus to control the partial pressure of iodine to discourage
the growth of iodine crystals. The iodine partial pressure PI2 in
the loading chamber was controlled to 0.5 PI2*, where PI2* was
the vapor pressure of iodine at room temperature (27 °C). A
sample of PDA crystals (5 mg) was exposed to iodine vapor in
the chamber for 0−96 h to afford a doped sample PDA·I2. The
degree of doping was measured by TGA (Figure S16 of the
Supporting Information) and showed saturation after ∼48h. A
one step desorption with a ∼3.5% weight loss was observed.
Assuming this weight loss corresponded to I2, we calculated a
1:14 iodine to PDA monomer unit ratio.
X-ray photoelectron spectroscopy (XPS) was used to
investigate the nature of the iodine species absorbed by PDA
crystals. The XPS survey scan spectrum of the PDA crystal
(Figure 9a) composed of three peaks were assigned to C1s
(∼285 eV), N1s (∼400 eV), and O1s (∼532 eV). In
comparison, two new peaks were observed in the spectrum of
iodine-saturated PDA crystals, which were located at ∼620 eV
and assigned to iodine 3d5/2 and 3d3/2 photoemissions (Figure
9b). Deconvolution results of C1s, N1s, O1s, and I3d5/2 XPS
spectra of both PDA crystal and PDA·I2 complex are reported
in Table S2 of the Supporting Information. After doping with
iodine, I3d5/2 and I3d3/2 peaks appeared in the XPS spectra.
The I3d5/2 peak was chosen to do further analysis and could be
Figure 10. Comparison of Raman spectra of PDA crystals before (blue
line) and after (red line) saturated with iodine.
PDA consists of four main peaks. Peaks located at ∼1506 and
∼2107 cm−1 corresponded to the typical stretch of PDAs. The
peak at ∼941 cm−1 is likely due to the −CH deformation of the
aromatic ring, while the origin of the peak at ∼1200 cm−1 may
be due to the C−N stretch of the amide groups. After
treatment with iodine, both the −CH deformation and C−N
stretch peaks shifted to high energy; the detail of the shift is
shown in the inset diagram of Figure 10, which indicates that
there may be interactions between the polyiodide anions and
the amide carbonyl.
Formation of Microcrystals. We have established that the
dihydrate 1·2H2O can be obtained in bulk and polymerized to
give PDAs. Next, we investigated if this process could be carried
out in smaller microcrystals deposited on different surfaces.
Microcrystalline PDAs may show faster equilibration with
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Raman spectroscopy was again used to monitor the
transformation of monomer to polydiacetylene in the microcrystals. Microcrystals generated by spin-coating a 1.0 mg/mL
macrocycle solution at a spin rate of 1000 rpm for 90 s on a
silica wafer were subjected to Raman spectroscopy before and
after thermal treatment (Figure S20 of the Supporting
Information). After heating, the alkyne absorption of macrocycle 1, microcrystals at ∼2266 cm−1 disappeared. Two new
bands were observed at ∼1506 and ∼2107 cm−1, which
correspond to the characteristic carbon double and triple bond
absorption of polydiacetylene. This suggests that the
diacetylene monomer was converted into polydiacetylene
during the heating process; however, we are currently
investigating methods to probe the efficiency and yield of this
process.
guests, be amenable for transport measurements, and more
suitable for integration into thin film organic electronic
devices.20 First, a solution of 1 in 50:50 MeOH/CH2Cl2 (1.0
mg/mL and 1.5 mg/mL) was deposited on different substrates
(Si wafers, glass, or quartz slides) by spin-coating at a rate of
1000 rpm. The substrates were examined before and after
thermal treatment, which was used to induce polymerization to
afford PDAs. In general, the SEM imaging of the microcrystals
on silicon substrates before heating were subject to poor
contrast and focus. A relatively brighter secondary electron
signal versus background is observed in the polymerized
samples (Figures 1c and 11). This could be indicative of
■
CONCLUSION
In summary, we observed that the dihydrate 1·2H2O form of
the diacetylene macrocycle underwent a SCSC transformation
upon heating in an inert atmosphere to give a polydiacetylene.
Significant atomic movement occurred within the crystal during
the polymerization process. The resulting PDA is a columnar
covalent nanotube containing two PDA chains that are parallel
and aligned along the nanotube. The two polymers within a
single tube are rigid and separated by a fixed distance. These
individual columnar PDA polymers are organized in three
dimensions by a series of hydrogen bonds that link each
nanotube with four neighboring nanotubes. We showed that
this unique PDA structure was able to absorb iodine and is
likely amenable to property control via adsorbed guests.
Comparison of X-ray photoelectron spectroscopy (XPS) survey
scans of the PDA and PDA·I2 complexes showed new peaks
after iodine exposure, which were attributed to triiodide, I3−,
and pentaiodide, I5−, respectively. We found that these
materials can also be assembled by spin-coating onto different
substrates and polymerized by heating. While it is known that
PDA crystallinity, morphology, and alignment affect its optical
and electronic properties, it is challenging to design model
systems with controlled structures that can test the structure−
property relationship.94,95 Our future work is focused on
examining the effects of crystal size and doping levels on their
electronic and optical properties.
Figure 11. (A) SEM image of PDA microcrystals generated by spincoating a 1.0 mg/mL macrocycle 1 solution on Si wafer at a spin rate
of 1000 rpm for 90 s; the spin-coated sample was heated at 190 °C for
3 h to induce polymerization. (B) Size distribution calculated based on
microcrystals in (A). (C) SEM image of PDA microcrystals obtained
under the same conditions as (A) but with 1.5 mg/mL macrocycle 1
concentration. (D) Size distribution calculated based on microcrystals
in (C).
reduced charging under the electron beam due to higher
conductivity,93 as would be expected in the polymerized fibers.
Such conductivity changes must ultimately be confirmed by
transport measurements. Therefore, we focused on these
samples. We investigated different spin-coating factors, such
as concentration of macrocycle solution, spin rate, and time to
find the optimal condition to obtain well-distributed microcrystals. We generated PDA microcrystals by spin-coating a
solution of 1 (1.0 mg/mL) at a rate of 1000 rpm for 90 s on
silicon wafers, and then heating the spin-coated samples at 190
°C for 3 h. Figure 11a shows the SEM image of these
microcrystals, which have a 1-D needlelike structure that were
randomly distributed over the surface. A normal distribution fit
gave an average microcrystal length of ∼3 μm (Figure 11b).
Microcrystals generated at higher solution concentration (1.5
mg/mL) are shown in Figure 11c and have a similar 1-D
structure but display a larger average length of ∼5 μm (Figure
11d). These experiments suggest that the size of microcrystals
can be controlled by the concentration of 1 in the initial
solution. SEM images of microcrystals generated on silicon,
glass, and quartz (see Figure S19 of the Supporting
Information) revealed no obvious differences in morphology.
■
ASSOCIATED CONTENT
S Supporting Information
*
CIF files of crystallographic data, 1H NMR, 13C NMR, PXRD,
DSC, TGA, IR, XPS, Raman, and absorption spectra. This
material is available free of charge via the Internet at http://
pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: [email protected].
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
The authors declare no competing financial interest.
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Article
(26) Hagler, T. W.; Pakbaz, K.; Voss, K. F.; Heeger, A. J. Phys. Rev. B
1991, 44, 8652.
(27) Hagler, T. W.; Pakbaz, K.; Heeger, A. J. Phys. Rev. B 1995, 51,
14199.
(28) Carter, G. M.; Thakur, M. K.; Chen, Y. J.; Hryniewicz, J. V. Appl.
Phys. Lett. 1985, 47, 457.
(29) Abe, S.; Schreiber, M.; Su, W. P.; Yu, J. Phys. Rev. B 1992, 45,
9432.
(30) Guo, D.; Mazumdar, S.; Dixit, S. N.; Kajzar, F.; Jarka, F.;
Kawabe, Y.; Peyghambarian, N. Phys. Rev. B 1993, 48, 1433.
(31) Nisoli, M.; Pruneri, V.; Desilvestri, S.; Dellepiane, G.;
Comoretto, D.; Cuniberti, C.; Lemoigne, J. Appl. Phys. Lett. 1994,
65, 590.
(32) Tabata, H.; Tokoyama, H.; Yamakado, H.; Okuno, T. J. Mater.
Chem. 2012, 22, 115.
(33) Stone, D. A.; Hsu, L.; Wheeler, N. R.; Wilusz, E.; Zukas, W.;
Wnek, G. E.; Korley, L. T. J. Soft Matter 2011, 7, 2449.
(34) Diegelmann, S. R.; Hartman, N.; Markovic, N.; Tovar, J. D. J.
Am. Chem. Soc. 2012, 134, 2028.
(35) Diegelmann, S. R.; Gorham, J. M.; Tovar, J. D. J. Am. Chem. Soc.
2008, 130, 13840.
(36) Jahnke, E.; Weiss, J.; Neuhaus, S.; Hoheisel, T. N.; Frauenrath,
H. Chem.Eur. J. 2009, 15, 388.
(37) Hsu, L.; Cvetanovich, G. L.; Stupp, S. I. J. Am. Chem. Soc. 2008,
130, 3892.
(38) Lowik, D. W. P. M.; Shklyarevskiy, I. O.; Ruizendaal, L.;
Christianen, P. C. M.; Maan, J. C.; van Hest, J. C. M. Adv. Mater. 2007,
19, 1191.
(39) Jahnke, E.; Lieberwirth, I.; Severin, N.; Rabe, J. P.; Frauenrath,
H. Angew. Chem., Int. Ed. 2006, 45, 5383.
(40) Dei, S.; Matsumoto, A. Macromol. Chem. Phys. 2009, 210, 11.
(41) Weiss, J.; Jahnke, E.; Frauenrath, H. Macromol. Rapid Commun.
2008, 29, 330.
(42) Deb, P.; Yuan, Z. Z.; Ramsey, L.; Hanks, T. W. Macromolecules
2007, 40, 3533.
(43) Banerjee, S.; Konig, B. J. Am. Chem. Soc. 2013, 135, 2967.
(44) Ramakers, B. E. I.; van den Heuvel, M.; Spithas, N. T. I.;
Brinkhuis, R. P.; van Hest, J. C. M.; Lowik, D. W. P. M. Langmuir
2012, 28, 2049.
(45) Seo, S.; Lee, J.; Choi, E. J.; Kim, E. J.; Song, J. Y.; Kim, J.
Macromol. Rapid Commun. 2013, 34, 743.
(46) Warman, J. M.; de Haas, M. P.; Dicker, G.; Grozema, F. C.;
Piris, J.; Debije, M. G. Chem. Mater. 2004, 16, 4600.
(47) Schen, M. A.; Kotowski, K.; Cline, J. Polymer 1991, 32, 1843.
(48) Chen, X.; Kang, S.; Kim, M. J.; Kim, J.; Kim, Y. S.; Kim, H.; Chi,
B.; Kim, S. J.; Lee, J. Y.; Yoon, J. Angew. Chem., Int. Ed. 2010, 49, 1422.
(49) Lee, J.; Yarimaga, O.; Lee, C. H.; Choi, Y. K.; Kim, J. M. Adv.
Funct. Mater. 2011, 21, 1032.
(50) Tseng, C. W.; Tao, Y. T. ACS Appl. Mater. Interfaces 2010, 2,
3231.
(51) Yoon, B.; Lee, S.; Kim, J. M. Chem. Soc. Rev. 2009, 38, 1958.
(52) Chae, S. K.; Park, H.; Yoon, J.; Lee, C. H.; Ahn, D. J.; Kim, J. M.
Adv. Mater. 2007, 19, 521.
(53) Rangin, M.; Basu, A. J. Am. Chem. Soc. 2004, 126, 5038.
(54) Gill, I.; Ballesteros, A. Angew. Chem., Int. Ed. 2003, 42, 3264.
(55) Yoon, B.; Shin, H.; Kang, E. M.; Cho, D. W.; Shin, K.; Chung,
H.; Lee, C. W.; Kim, J. M. ACS Appl. Mater. Interfaces 2013, 5, 4527.
(56) Yoon, B.; Park, I. S.; Shin, H.; Park, H. J.; Lee, C. W.; Kim, J. M.
Macromol. Rapid Commun. 2013, 34, 731.
(57) Yoon, B.; Ham, D. Y.; Yarimaga, O.; An, H.; Lee, C. W.; Kim, J.
M. Adv. Mater. 2011, 23, 5492.
(58) Wegner, G. A. Z. Naturforsch., B: Chem. Sci. 1969, 24, 824−832.
(59) Wegner, G. Pure Appl. Chem. 1977, 49, 443.
(60) Kane, J. J.; Liao, R. F.; Lauher, J. W.; Fowler, F. W. J. Am. Chem.
Soc. 1995, 117, 12003.
(61) Fowler, F. W.; Lauher, J. W. J. Phys. Org. Chem. 2000, 13, 850.
(62) Lauher, J. W.; Fowler, F. W.; Goroff, N. S. Acc. Chem. Res. 2008,
41, 1215.
ACKNOWLEDGMENTS
The authors gratefully acknowledge partial support for this
work from the NSF Grants CHE-1012298 and CHE-1305136.
Synchrotron data were collected through the SCrALS (Service
Crystallography at Advance Light Source) program at Beamline
11.3.1, Advanced Light Source (ALS), Lawrence Berkeley
National Lab. The ALS is supported by the U.S. Department of
Energy, Office of Energy Sciences, Materials Sciences Division
under contract DE-AC02−05CH11231. The authors acknowledge the University of South Carolina Electron Microscopy
Center for instrument use and scientific and technical
assistance.
■
ABBREVIATIONS
■
REFERENCES
PDA, polydiacetylene; SCSC, single-crystal-to-single-crystal;
PXRD, powder X-ray diffraction experiments; SEM, scanning
electron microscope; XPS, X-ray photoelectron spectroscopy;
DSC, differential scanning calorimetry; TGA, thermogravimetric analysis; TLC, thin layer chromatography
(1) Iijima, S. Nature 1991, 354, 56.
(2) Ajayan, P. M. Chem. Rev. 1999, 99, 1787.
(3) Niyogi, S.; Hamon, M. A.; Hu, H.; Zhao, B.; Bhowmik, P.; Sen,
R.; Itkis, M. E.; Haddon, R. C. Acc. Chem. Res. 2002, 35, 1105.
(4) Hu, P. A.; Zhang, J.; Li, L.; Wang, Z. L.; O’Neill, W.; Estrela, P.
Sensors-Basel 2010, 10, 5133.
(5) Cao, Q.; Rogers, J. A. Adv. Mater. 2009, 21, 29.
(6) Feldman, A. K.; Steigerwald, M. L.; Guo, X. F.; Nuckolls, C. Acc.
Chem. Res. 2008, 41, 1731.
(7) Avouris, P.; Chen, Z. H.; Perebeinos, V. Nat. Nanotechnol. 2007,
2, 605.
(8) Diao, P.; Liu, Z. F. Adv. Mater. 2010, 22, 1430.
(9) Coleman, J. N.; Khan, U.; Blau, W. J.; Gun’ko, Y. K. Carbon 2006,
44, 1624.
(10) Cahill, D. G.; Ford, W. K.; Goodson, K. E.; Mahan, G. D.;
Majumdar, A.; Maris, H. J.; Merlin, R.; Sr, P. J. Appl. Phys. 2003, 93,
793.
(11) Chapman, R.; Danial, M.; Koh, M. L.; Jolliffe, K. A.; Perrier, S.
Chem. Soc. Rev. 2012, 41, 6023.
(12) Yoo, B.; Shin, S. B. Y.; Huang, M. L.; Kirshenbaum, K. Chem.
Eur. J. 2010, 16, 5528.
(13) Bong, D. T.; Clark, T. D.; Granja, J. R.; Ghadiri, M. R. Angew.
Chem., Int. Ed. 2001, 40, 988.
(14) Martin, C. R. Acc. Chem. Res. 1995, 28, 61.
(15) Liu, J. Z.; Lam, J. W. Y.; Tang, B. Z. Chem. Rev. 2009, 109, 5799.
(16) Chen, X.; Kang, S.; Kim, M. J.; Kim, J.; Kim, Y. S.; Kim, H.; Chi,
B.; Kim, S. J.; Lee, J. Y.; Yoon, J. Angew. Chem., Int. Ed. 2010, 49, 1422.
(17) Hoppe, H.; Egbe, D. A. M.; Muhlbacher, D.; Sariciftci, N. S. J.
Mater. Chem. 2004, 14, 3462.
(18) Zhang, W.; Xu, H. B.; Chen, Y.; Cheng, S.; Fan, L. J. ACS Appl.
Mater. Interfaces 2013, 5, 4603.
(19) Xu, Y. W.; Smith, M. D.; Geer, M. F.; Pellechia, P. J.; Brown, J.
C.; Wibowo, A. C.; Shimizu, L. S. J. Am. Chem. Soc. 2010, 132, 5334.
(20) Mahato, R. N.; Lulf, H.; Siekman, M. H.; Kersten, S. P.;
Bobbert, P. A.; de Jong, M. P.; De Cola, L.; van der Wiel, W. G. Science
2013, 341, 257.
(21) Rinzler, A. G.; Donoghue, E. P. ACS Nano 2011, 5, 3425.
(22) Day, D. R.; Lando, J. B. J. Appl. Polym. Sci. 1981, 26, 1605.
(23) Sakamoto, M.; Wasserman, B.; Dresselhaus, M. S.; Wnek, G. E.;
Elman, B. S.; Sandman, D. J. J. Appl. Phys. 1986, 60, 2788.
(24) Takami, K.; Kuwahara, Y.; Ishii, T.; Akai-Kasaya, M.; Saito, A.;
Aono, M. Surf. Sci. 2005, 591, L273.
(25) Hagler, T. W.; Pakbaz, K.; Moulton, J.; Wudl, F.; Smith, P.;
Heeger, A. J. Polym. Commun. 1991, 32, 339.
1001
dx.doi.org/10.1021/cg401380a | Cryst. Growth Des. 2014, 14, 993−1002
Crystal Growth & Design
Article
(63) Li, Z.; Fowler, F. W.; Lauher, J. W. J. Am. Chem. Soc. 2009, 131,
634.
(64) Gravel, E.; Ogier, J.; Arnauld, T.; Mackiewicz, N.; Duconge, F.;
Doris, E. Chem.Eur. J. 2012, 18, 400.
(65) Rondeau-Gagné, S.; Neabo, J. R.; Desroches, M.; Larouche, J.;
Brisson, J.; Morin, J.-F. J. Am. Chem. Soc. 2013, 135, 110.
(66) Sun, A. W.; Lauher, J. W.; Goroff, N. S. Science 2006, 312, 1030.
(67) Hsu, T. J.; Fowler, F. W.; Lauher, J. W. J. Am. Chem. Soc. 2012,
134, 142.
(68) Exarhos, G. J.; Risen, W. M.; Baughman, R. H. J. Am. Chem. Soc.
1976, 98, 481.
(69) Curtis, S. M.; Le, N.; Fowler, F. W.; Lauher, J. W. Cryst. Growth.
Des. 2005, 5, 2313.
(70) Dybtsev, D. N.; Chun, H.; Kim, K. Angew. Chem., Int. Ed. 2004,
43, 5033.
(71) Yanai, N.; Uemura, T.; Inoue, M.; Matsuda, R.; Fukushima, T.;
Tsujimoto, M.; Isoda, S.; Kitagawa, S. J. Am. Chem. Soc. 2012, 134,
4501.
(72) Gedrich, K.; Senkovska, I.; Klein, N.; Stoeck, U.; Henschel, A.;
Lohe, M. R.; Baburin, I. A.; Mueller, U.; Kaskel, S. Angew. Chem., Int.
Ed. 2010, 49, 8489.
(73) Uemura, K.; Yamasaki, Y.; Komagawa, Y.; Tanaka, K.; Kita, H.
Angew. Chem., Int. Ed. 2007, 46, 6662.
(74) Ferey, G.; Serre, C. Chem. Soc. Rev. 2009, 38, 1380.
(75) Reger, D. L.; Horger, J. J.; Smith, M. D. Chem. Commun. 2011,
47, 2805.
(76) Reger, D. L.; Horger, J. J.; Smith, M. D.; Long, G. J.; Grandjean,
F. Inorg. Chem. 2011, 50, 686.
(77) McKeown, N. B. J. Mater. Chem. 2010, 20, 10588.
(78) Holst, J. R.; Trewin, A.; Cooper, A. I. Nat. Chem. 2010, 2, 915.
(79) Pivovar, A. M.; Holman, K. T.; Ward, M. D. Chem. Mater. 2001,
13, 3018.
(80) Holman, K. T.; Pivovar, A. M.; Ward, M. D. Science 2001, 294,
1907.
(81) Swift, J. A.; Ward, M. D. Chem. Mater. 2000, 12, 1501.
(82) Langley, P. J.; Hulliger, J. Chem. Soc. Rev. 1999, 28, 279.
(83) Roy, K.; Wang, C.; Smith, M. D.; Dewal, M. B.; Wibowo, A. C.;
Brown, J. C.; Ma, S. G.; Shimizu, L. S. Chem. Commun. 2011, 47, 277.
(84) Roy, K.; Wibowo, A. C.; Pellechia, P. J.; Ma, S. G.; Geer, M. F.;
Shimizu, L. S. Chem. Mater. 2012, 24, 4773.
(85) Zhou, Q.; Carroll, P. J.; Swager, T. M. J. Org. Chem. 1994, 59,
1294.
(86) Lopez-Mejias, V.; Knight, J. L.; Brooks, C. L.; Matzger, A. J.
Langmuir 2011, 27, 7575.
(87) Coakley, K. M.; McGehee, M. D. Chem. Mater. 2004, 16, 4533−
4542.
(88) Nantalaksakul, A.; Krishnamoorthy, K.; Thayumanavan, S.
Macromolecules 2010, 43, 37−43.
(89) Aldissi, M.; Armes, S. P. Macromolecules 1992, 25, 2963.
(90) Zeng, X. R.; Ko, T. M. J. Polym. Sci., Part B: Polym. Phys. 1997,
35, 1993.
(91) Hsu, S. L.; Signorelli, A. J.; Pez, G. P.; Baughman, R. H. J. Chem.
Phys. 1978, 69, 106.
(92) Grigorian, L.; Williams, K. A.; Fang, S.; Sumanasekera, G. U.;
Loper, A. L.; Dickey, E. C.; Pennycook, S. J.; Eklund, P. C. Phys. Rev.
Lett. 1998, 80, 5560.
(93) Kim, K. Y.; Akase, Z.; Suzuki, T.; Shindo, D. Mater. Trans. 2010,
51, 1080.
(94) Kim, J.; Swager, T. M. Nature 2001, 411, 1030.
(95) Kim, F. S.; Ren, G.; Jenekhe, S. A. Chem. Mater. 2011, 23, 682.
1002
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