BOOK OF ABSTRACTS - Grupo especializado de Fotoquímica

Transcription

IX Congreso de Fotoquímica
Leioa (Vizcaya) 21-23 Septiembre, 2009
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Leioa (Vizcaya) 21-23 Septiembre, 2009
Grupo Especializado de Fotoquímica de la Real Sociedad Española de Química
Organizing Committee
Pedro Campos; A. Ulises Acuña; Roberto Sastre; Miguel A. Miranda; José Luis Bourdelande:
Rafael Suau; Beatriz Cabañas; José Albaladejo; Diego Armesto; Abderrazzak Douhal;
Fernando López Arbeloa y Fernando Castaño
Local Organizing Committee
Fernando Castaño; Fernando López Arbeloa; Roberto Martínez; Francisco Basterretxea;
María Nieves Sánchez Rayo; Carolina Redondo; Alberto Lesarri; José A. Fernández; Asier
Longarte
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SPONSORS AND SUPPORTING ORGANIZATIONS
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INDEX
1.- Conference program.......................................................
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2.- Workshop on Single Molecule Fluorescence Imaging... 17
3.- Plenary lectures.............................................................. 21
4.- Invited lectures................................................................ 29
5.- Oral presentations.......................................................... 41
6.- Posters............................................................................ 81
7.- List of participants......................................................... 147
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CONFERENCE PROGRAM
MONDAY, 21 SEPTEMBER
08:45-09:00
Opening Ceremony
Chairman: Prof. Pedro J. Campos
09:00-10:00
Plenary Lecture: Prof. Johan Hofkens
Probing dynamics of (bio)molecules with single molecule spectroscopy
10:00-10:40
Invited Speaker: Dr. Luis Serrano-Andrés
Photochemistry and Quantum Chemistry: The New Frontiers
10:40-10:45
Announcements
10:45-11:15
COFFEE
Chairman: Prof. Guillermo Orellana
11:15-12:35
Oral Presentations
11:15-11:35
Molecular injection of fluorescent drugs in Leishmania parasites
V. Hornillos, J.R. Luque, B. García de la Torre, D. Andreu, L. Rivas, F. Amat, A.U. Acuña
11:35-11:55
A possible mechanism for photostability in polyglycine: description of photoinduced proton
transfer reaction paths at the CASSCF//CASPT2 level of theory
M. Marazzi, U. Sancho, O. Castaño, W. Domcke, L.M. Frutos
11:55-12:15
Excited state dynamics in aromatic molecules and clusters
A. Longarte, R. Montero, A. Peralta, F. Castaño
12:15-12:35
Second and third harmonic generation from powder quinoxalinoporphyrine derivatives
J.L. Bourdelande, J. Hernando, T. Khoury, R.G. Clady, T. Schmidt, M.J. Crossley
12:45-14:00
LUNCH
14:00-15:30
POSTER SESSION + COFFEE
Chairman: Prof. Silvia E. Braslavsky
15:30-16:10
Invited Speaker: Prof. Hermenegildo García
Fotoquímica en espacios confinados. Desde estudios básicos hacia las aplicaciones
16:10-18:30
Oral Presentations
16:10-16:30
Fluorescence correlation spectroscopy as a tool to study the interaction dye-surfactant during
the micellization process
J. Bordello, D. Granadero, M. Novo, W. Al-Soufi
16:30-16:50
Fotoquímica de agregados de plata en cucurbit[n]uriles
M. De Miguel, M. Álvaro, H. García
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16:50-17:10
Layered double hydroxides as photocatalysts for visible light oxygen generation from water
C. Gomes Silva, Y. Bouizi, V. Fornés, H. García
17:10-17:30
COFFEE
Chairman: Prof. Santi Nonell
17:30-17:50
Estudio fluorescente de la complejación del dapoxyl por ciclodextrinas: efecto del tamaño de la
cavidad en el tipo y fortaleza de los compejos
D. Granadero, J. Bordello, M. Novo, W. Al-Soufi
17:50-18:10
Transient absorption spectroscopy of drugs derivatives within protein microenvironment
M. C. Jiménez, C. J. Bueno, I. Vayá, M. A. Miranda
18:10-18:30
Femtosecond Studies of a Confined Porphyrin Derivative by Human Serum Albumin Protein
A.Synak, M.Gil, J.A. Organero and A. Douhal
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TUESDAY, 22 SEPTEMBER
Chairman: Prof. Miguel Angel Miranda
09:00-10:00
Plenary Lecture: Prof. Norman A. García
Photodegradation of phenolic water-contaminants under environmental conditions
10:00-10:40
Invited Speaker: Prof. Guillermo Orellana
Polímeros de impronta molecular y fluorescencia para el control de calidad del agua y de los
alimentos mediante reconocimiento molecular
10:40-10:45
Announcements
10:45-11:15
COFFEE
Chairman: Dr. Inmaculada García-Moreno
11:15-12:35
Oral Presentations
11:15-11:35
Aplicaciones derivadas de la fotoquímica de O-aciloximas
A. Caballero, R. Alonso, M. A Rodríguez, P. J. Campos.
11:35-11:55
mPTA-based photoactive ruthenium derivatives
(mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane)
M. Chaara, R. Girotti, S. Mañas, V. Passarelli, R. Perutz, A. Romerosa, M. Serrano
11:55-12:15
Controlling laser emission by size of particles in gain media
V. Martín, R. Sastre, A. Costela, I. García-Moreno
12:15-12:35
Síntesis y estudio fotofísico de nuevos cromóforos con estructura de aza-BODIPY para
aplicaciones en medios fisiológicos
R. Suau, E. Pérez-Inestrosa, D. Collado
12:45-14:00
14:00-14:15
LUNCH
COFFEE
Chairman: Dr. Ezequiel Pérez-Inestrosa
14:15-14:55
Invited Speaker: Dr. Diego Sampedro
Interruptores y motores moleculares biomiméticos
14:55-15:55
Oral Presentations
14:55-15:15
Determinants of singlet oxygen formation and decay in biological systems
S. Nonell, X. Ragàs and M. Agut
15:15-15:35
Interactions of a cyanine homodimeric dye with single-stranded and double-stranded DNA
M. J. Ruedas-Rama, A. Orte, J. M. Paredes, L. Crovetto, E. M. Talavera, J. M. Alvarez-Pez
15:35-15:55
Energy and Charge Transfer Processes in BDP Dyes to Develop Novel Fluorescence Probes
and Sensors
J. Bañuelos, F. López Arbeloa and I. López Arbeloa
16:00
EXCURSION + DINNER
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WEDNESDAY, 23 SEPTEMBER
Chairman: Prof. José Luis Bourdelande
09:00-10:00
Plenary lecture: Prof. Silvia E. Braslavsky
Role of carotenoids in photosystem II (PSII) reaction centers
10:00-10:40
Invited Speaker: Prof. José M. Alvarez-Pez
Buffer-Mediated ground- and excited-state proton exchange reactions at the single molecule
and ensemble level (TPSPC)
10:40-10:45
Announcements
10:45-11:15
COFFEE
Chairman: Dr. A. Ulises Acuña
11:15-12:35
Oral Presentations
11:15-11:35
Una Nueva Generación de Cromóforos Ditópicos VSD (Voltage-Sensitive Dyes) para
Aplicaciones Biomédicas
J.M. Montenegro, J. Casado, J.T. López Navarrete, R. Suau, E. Pérez-Inestrosa
11:35-11:55
New integrated oxygen sensors based on GaN emitters covalently functionalized with
luminescent Ru(II) complexes
J. López-Gejo, A. Arranz, C. Palacio, A. Navarro, E. Muñoz, G. Orellana
11:55-12:15
New Hybrid Dyes for Biomedical and Photonic Applications
M.E. Pérez-Ojeda, B. Trastoy, J.L. Chiara, R. Sastre
12:15-12:35
Doble transferencia de hidrógeno fotoinducida por transferencia de carga en compuestos
azaaromáticos bifuncionales isómericos: derivados pirido-indólicos y pirrolo-quinolínicos
D. Reyman, C. Díaz-Oliva
12:45-14:00
LUNCH
14:00-15:30
POSTER SESSION + COFFEE
Chairman: Prof. Wajih Al-Soufi
15:30-16:50
Oral Presentations
15:30-15:50
Molecular Logic with Photonic Devices – Quo Vadis?
U. Pischel
15:50-16:10
On board chemical monitoring of the aircraft hydraulic fluid using Ru(II) luminescent
complexes and frequency-domain lifetime measurements
M. Veiga, J. L. Urraca, C. Cano, M. C. Moreno-Bondi, G. Orellana
16:10-16:30
New Bodipy Dyes with Wavelength-Finely Tunable Laser Action in the Red-Near Infrared
Spectral Region
A.R. Agarrabeitia, J. Bañuelos, A. Costela, G. Durán-Sampedro, I. García-Moreno, F. López
Arbeloa, I. López Arbeloa, M.J. Ortiz
16:30-16:50
Matlalina, el fluoróforo del Lignum nephriticum de N. Monardes
A.U. Acuña, F. Amat, P. Morcillo, M. Liras, B. Rodríguez
16:50-17:00
End of Conference
17:00
GRUFO BOARD MEETING
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LIST OF POSTERS
P01
Photoinduced oxidation of pyrene on the CdSe quantum dot surface
Jordi Aguilera Sigalat, Raquel E. Galian, Julia Pérez Prieto
P02
Efficient and stable amplified spontaneous emission (ASE) from dye-doped polymeric planar
waveguides
L. Cerdán, A. Costela, I. García-Moreno, O. García, R. Sastre, M. Calle, D. Muñoz, and J. de Abajo
P03
New Laser Dyes Based on Boron Complexes with Tunable Emission on the Whole Visible Region: A
Theoretical Approach
J. Bañuelos Prieto, F. López Arbeloa, M. Liras and I. López Arbeloa
P04
Single Molecule Studies of Catalytic Reactions of Haloperoxidase Enzymes by Confocal Fluorescence
Microscopy
V. Martínez Martínez, G. De Cremer, Maarten, B.J. Roeffaers, Johan Hofkens and F. López Arbeloa
P05
Use of Polarized Spectroscopy to Prove the Presence of Rhodamine Aggregates Formed in
Surfactant/Clay Hosts
S. Salleres, T. Arbeloa , C. Corcostegui, I. López Arbeloa and F. López Arbeloa
P06
Syntesis and photophysical properties of asymmetric BODIPYs dyes PM567 analogues
A.R. Agarrabeitia, J. Bañuelos, F- López Arbeloz, I. López Arbeloa, M. Martínez-Ripoll, M.J. Ortiz, M.
Palacios, M.E. Pérez-Ojeda
P07
Organized media effect on the photochemical deoxygenation of rezorufin in the presence of amines
G.V. Porcal, M.S. Altamirano, C.M. Previtali, S.G. Bertolotti
P08
Excited state interactions in biphenyl-tryptophan dyads
Paula Bonancía, Ignacio Vayá, M. Consuelo Jiménez, Miguel A. Miranda
P09
Specific and selective generation of guanine neutral radical from photolabile nucleoside derivatives.
S. Encinas, C. Paris, M. A. Miranda, P. Kaloudis, D. Vrantza, R. Pérez-Ruiz, T. Gimisis
P10
Compuestos pseudopeptídicos sintéticos como modelos supramoleculares para el estudio de fármacos
fotoactivos
Francisco Galindo, M. Angeles Izquierdo, M. Isabel Burguete, Santiago V. Luis, Xavier J. Salom-Roig,
Jean Martínez, María C. Morant-Miñana, Miguel A. Miranda, Julia Pérez -Prieto
P11
Photophysical study of a rosuvastatin photoproduct
Giacomo Nardi, Sara Montanaro, Virginie Lhiaubet-Vallet, Miguel Angel Miranda
P12
Photophysical and Photochemical study of Cinacalcet
E. Nuin, M. C. Jiménez, I. Andreu, M. A. Miranda
P13
Laser Flash Photolysis Studies of Ketoprofen Conjugates of α-Amino-Cholesterol
F. Palumbo, I. Andreu, M.S. Sinicropi, M. A. Miranda
P14
Fluorescent Cholic Acid derivates as probes for the photophysical characterization of bile acid
aggregates
Miguel Gómez, M. Luisa Marin, Miguel A. Miranda
P15
Síntesis y caracterización fotofísica de porficenos con diferentes sustituyentes arilo
M. Camarasa, I. Burgués, D. Sánchez-García, S. Nonell
P16
Solvent effects on the photophysics of Naphthoxazole derivatives
Antonio L. Zanocco, Manuel Curitol, Xavier Ragàs, Santi Nonell
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P17
Síntesis y caracterización fotofísica de porficenos catiónicos
R. Ruiz, D. Sánchez-García, S. Nonell
P18
Liposomas marcados con folato como sistemas de vehiculización para terapia fotodinámica dirigida
M. García-Díaz, S. Nonell, A. Casadó, M. Mora, M. L. Sagristá
P19
Excimeros y transferencia de energía intramolecular en disoluciones de copolímeros de N-vinil
carbazole/vinil tert-butil benzoato de distinta composición molar
Thais Carmona, Natali Fernández-Peña, M. Pilar Tarazona, Enrique Saiz and Francisco Mendicuti
P20
Ground and excited state properties of levosimendan in solution and in chemical and biological
nanocavities
Boiko Cohen, Juan Angel Organero, Luis Rodrigues Padial, Lucía Santos Peinado, Ruxandra Gref,
Abderrazzak Douhal
P21
Photodynamics of 4′-dimethylaminoflavonol interacting with Nax zeolites, MCM-41 mesoporous
material and Silica nanoparticles.
C. Martín, J.A. Organero, A. Roshal and A. Douhal
P22
Photophysical study of a xanthene derivate in a medium mimicking celular environment
L. Crovetto, J.M. Paredes, A. Orte, M.J. Ruedas-Rama, R. Rios, J.M. Alvarez-Pez, E.M. Talavera
P23
Femtosecond pulsed laser deposition of CdS nanostructures
M. Sanz, J. G. Izquierdo, L. Bañares , M. Castillejo
P24
Characterization of holographic gratings implemented in a photopolymerizable glass with femtosecond
laser pulses
J. G. Izquierdo, M. P. Hernández-Garay, O. Martínez-Matos, J.A. Rodrigo, R. Weigand, M.L. Calvo, L.
Bañares and P. Cheben
P25
Polymeric matrices containing self-assembled fibrillar networks and quantum dots
M. A. Izquierdo, F. Galindo, P. Wadhavane, M. I. Burguete, S. V. Luis
P26
Reactividad del Oxígeno molecular singulete O2 1∆g, frente a flavonoides en vesículas de
dipalmitoilfosfatidilcolina
Else Lemp M., Antonio L. Zanocco, Javier Morales-Valenzuela
P27
Time-resolved optical emission spectroscopic studies of ambient air induced by a high-power TEA-CO2
pulsed laser
J.J. Camacho, L. Díaz, M. Santos, L. Juan, E. Martín, J.M.L. Poyato
P28
Photophysic Properties of 3- and 4-amine 1,8-Naphthalimide N-substituted
E. Martin, J.L. Gu. Coronado, J. J. Camacho and J. M. L. Poyato
P29
Papel de las fuerzas electrostáticas e hidrofóbicas en las interacciones entre Rodamina 123 y diferentes
tipos de tensoactivos.
M. Novo, S. Freire, D. Granadero, J. Bordello, W. Al-Soufi
P30
Photosensitized materials doped with LDS 698: photophysical and lasing properties
M. Pintado-Sierra, V. Martín, R. Sastre, A. Costela, I. García-Moreno
P31
Studies of chiral recognition in the encapsulation of naproxen into a hyperbranched macromolecules
with a photoactive core
Salvador Pocoví-Martínez, Lourdes Pastor-Pérez, M.C. Cuquerella, Salah-Eddine Stiriba, Julia PérezPrieto
P32
Estudio fotoquímico de interruptores moleculares biomiméticos.
Pedro J. Campos, Diego Sampedro, Laura Rivado-Casas
P33
Luminescent indicator dyes for heavy metals determination
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André Santos, Kássio M.G. Lima, Guillermo Orellana
P34
A combined spectroscopic and theoretical study of propofol and its hydrated clusters.
Iker León, Emilio Cocinero, Judith Millán, Alberto Lesarri, Fernando Castaño, José Andrés Fernández
P35
Laser ablation of metallic targets
Jon I. Apiñaniz, Roberto Martinez, Fernanio. Castaño
P36
Study of the interaction of high intensity laser radiation with metals
P. Ecija, R. Martínez, F.J. Basterretxea, M.N. Sánchez Rayo, F. Castaño
P37
Photophysics and Photodissociation Dynamics of 1-Iodonaphthalene
R. Montero,A. Peralta Conde, M. E. Corrales, L. Bañares, F. Castaño, A. Longarte
P38
Laser Interference Lithography for the creation of regular nanoarrays and structures
C. Redondo, B. Sierra, D. Navas, F. Castaño
P39
Structures of Tropinone in Gas Phase
Emilio J. Cocinero, Patricia Ecija, José A. Fernández, Jens-Uwe Grabow, Fernando Castaño, Alberto
Lesarri
P40
New Organic-Inorganic Host for the Sensitized Luminescence of Lanthanides and Layered γ-Zirconium
Phosphate
E. Brunet, O. Juanes, L. Jiménez, J.C. Rodríguez-Ubis
P41
Photochemically Initiated Reaction of CF3CH2CHO with OH Radicals between 263 and 358 K
M. Antiñolo, E. Jiménez, J. Albadalejo
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16
WORKSHOP ON SINGLE MOLECULE
FLUORESCENCE IMAGING
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Bilbao (Leioa) 24th September, 2009
La espectroscopia de fluorescencia de moléculas individuales es un nuevo campo fascinante
con extraordinarias posibilidades para el estudio de una gran variedad de sistemas como
vesículas, proteínas, ácidos nucléicos, membranas biológicas y células , polímeros, superficies
de sólidos, disoluciones de tensioactivos, sistemas supramoleculares, etc. Las técnicas de
espectroscopia de fluorescencia de moléculas individuales (SMF) son altamente específicas y
existe una gran variedad de modalidades, apareciendo nuevas variantes con velocidad
vertiginosa. Por tanto, la cooperación entre un grupo especialista en SMF y otros grupos
expertos en los sistemas a estudiar es especialmente fructífera.
El objetivo de este taller es reunir los grupos españoles de SMF con otros grupos interesados
en cooperar con éstos. Debe servir para establecer contactos personales, intercambiar
experiencia y promover el uso de técnicas de SMF en España. Por tanto, invitamos a
participar a todos los investigadores interesados en SMF y animamos especialmente a jóvenes
investigadores que quieran comenzar en este campo emocionante.
Fluorescence spectroscopy with single molecule resolution is a fascinating new field with
unique possibilities for the study of a big variety of systems, such as vesicles, proteins,
nucleic acids, biological membranes and cells, polymers, solid surfaces, surfactant solutions,
supramolecular systems etc. Single molecule fluorescence (SMF) detection techniques are
highly specialized and new variants add with vertiginous speed. It is therefore a technique
most efficiently used in cooperation between groups experts in SMF and others specialized in
the systems to study.
It is the aim of this workshop to bring together Spanish SMF groups with other groups either
starting in this field or interested to cooperate. It should serve to establish personal contacts,
exchange experience and promote the use of SMF techniques in Spain. We therefore invite all
those investigators interested in SMF and we especially encourage young investigators who
wish to start in this exciting field.
Organizing Committee:
Wajih Al-Soufi, Francisco J. Basterretxea, Fernando Castaño, Fernando López Arbeloa,
Roberto Martínez, María Nieves Sánchez Rayo.
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Programa/Program
09:00-09:45
Johan Hofkens, K.U. Leuven, Belgium: Single molecule detection: state of the art and
outlook.
9:50-10:35
Jordi Hernando, UAB, Barcelona: Single molecule spectroscopy of multichromophoric
systems: from photonic wires to molecular switches.
10:35-11:00
COFFEE
11:00-11:45
Boiko Cohen, UCLM, Toledo: Single molecule spectroscopy of immobilized dyes in
mesoporous silica nanomaterials.
11:50-12:15
Virginia Martínez, UPV-EHU, Bilbao: Haloperoxidase reaction events, bio- and
chemocatalysis, monitorized at single molecule level by confocal fluorescence microscopy.
12:20-13:00
Peter Kapusta, Picoquant, Berlin: Concepts and Components for Time-Resolved Single
Molecule Microsocpy.
13:00-14:30
LUNCH + COFFEE
14:30-15:15
Ángel Orte Gutierrez, UGR, Granada: Biomolecular Interactions at the Single Molecule
Level. Multi-Laser Excitation Techniques.
15:20-16:05
Maria García-Parajo, IBEC, Barcelona: Single Molecule BioNanophotonics: from imaging to
diffusing molecules on the cell membrane.
16:10-16:55
Wajih Al-Soufi, USC, Santiago de Compostela: Supramolecular dynamics studied by
fluorescence correlation spectroscopy.
16:55-17:10 Concluding remarks
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PLENARY LECTURES
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Probing dynamics of (bio)molecules by single molecule spectroscopy
Johan Hofkens
Katholieke Universiteit Leuven, Department of Chemistry, Lab. of Photochemistry and Spectroscopy,
Celestijnenlaan 200 F, B-3001 Leuven, Belgium, [email protected]
Keywords: single molecule spectroscopy, polymers, enzyme, catalysis
Over the last 15 years, single molecule spectroscopy (SMS) has been established as a new
tool in the ever expanding range of spectroscopic methods. SMS is especially useful to study
inhomogeneous systems. Biological systems are by their nature highly heterogeneous and as
such perfect targets for SMS. From this it is clear that, next to biological samples, polymers
form a study object of SMS as polymers are very often heterogeneous in their behavior. Many
theories that describe polymer properties are based on a microscopic picture that now can be
evaluated experimentally by applying single molecule techniques. Furthermore, single
molecule techniques are very useful for the study of dynamic processes since no
synchronization is needed when dynamic events are studied. In this contribution, we will
show how different single molecule techniques can be used in the study of dynamic processes
at the molecular level. The following topics will be dicussed:
1) Defocused wide-field imaging of moleular rotation in [1-4].
2) Study of the glass transition by confocal microscopy [5].
3) Study of diffusion of individual polymers with wide-field microscopy [6]
4) Single molecule enzymatics [7,8]
5) Single molecule catalysis [9]
References
[1] D. Patra , I. Gregor and J. Enderlein, J. Phys. Chem. A 2004, 108, 6836-6841.
[2] M. Böhmer and J. Enderlein, J. Opt. Soc. Am. B 2003, 20, 554-559.
[3] W. Schroeyers, R. Vallée, D. Parta, J. Hofkens, S. Habuchi, T. Vosch, M. Cotlet, K.
Müllen, J. Enderlein, F. C. De Schryver, J. Am. Chem. Soc. 2004, 126, 14310-14311.
[4] H. Uji-i, S.M. Melnikov, A. Deres, G. Bergamini, F. De Schryver, A. Herrmann, K.
Mullen, J. Enderlein, J. Hofkens Polymer 2006, 47, 2511-2518
[5] R. Vallee et al. J. Am. Chem. Soc. 2005, 127 (34), 12011-12020
[6] P.G. de Gennes, Scaling concepts in polymer physics, 1971
[7] K. Velonia, et al Angew. Chem., Int. Ed. 2005, 44 (4), 560-564
[8] O. flomenbom et al, Proc. Nat. Acad. Sci. USA 2005, 102 (7) 2368-2372
[9] M. Roeffaers et al, Nature 2006, 439, 572-575
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Photodegradation of phenolic water-contaminants under
environmental conditions
Norman. A. García
Departamento de Química. Universidad Nacional de Río Cuarto. 5800 Río Cuarto, Argentina, y
Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET) Argentina
The degradation of hydroxyaromatic compounds (ArOH) under environmental and
artificial conditions has received great attention in the last decades [1,2,3,4]. These
compounds are generally toxic to living organisms, even at extremely low concentrations.
Different ArOH are being continuously incorporated into natural waters from different
sources and by a variety of routes. A few examples may illustrate on the magnitude of the
problem:
- Many profusely used agricultural pesticides have phenol groups in their molecular
structures [5]. Significant amounts of these compounds are incorporated to surface waters and
soils, possibly constituting the main channel of natural-water contamination by ArOH.
- Bisphenols comprise a family of extremely dangerous endocrine disruptors, profusely used
in the industry for the production of epoxy resins and polycarbonate plastics, and included as
flame retardants in a variety of polymers [6]. These ArOH contaminate surface waters by
leaching or dissolution of disposable products, such as domestic packages.
- The presence of phenolic estrogens in surface waters has been a subject of great concern
during the last years. Some of these compounds, such as 17β-estradiol and its derivatives
−major constituents of contraceptives− are endocrine disrupting chemicals, highly harmful for
the aquatic fauna, and arrive to waste waters through human excretion [7,8].
This preoccupant situation has triggered the study of the induced and natural degradation
−including the photochemical decomposition− of these contaminants in different types of
waters [¡Error! Marcador no definido.,9]. The photochemical fading can become an
important natural degradation pathway, in special in sunny countries and under favorable
environmental conditions.
When the contaminant absorbs the irradiating light, the photodegradation can occur from
its electronically excited states through different processes: breakage of molecular bonds,
direct reaction with ground-state dissolved oxygen, and reaction with reactive oxygen species
(ROS), such as singlet molecular oxygen O2(1∆g), superoxide anion (O2•−), hydrogen peroxide
(H2O2), only to mention some of them, generated by energy- or electron-transfer processes
from the electronically excited contaminant to ground state oxygen. Nevertheless, most
ArOH, in their molecular form, are transparent to natural daylight. On these grounds, an
alternative to the direct photodegradation corresponds to the so-called photosensitized
process. In this mechanism, a colored agent, named photosensitizer, absorbs environmental
light and generates its electronic excited states. From these states, under aerobic or anaerobic
conditions, a complex scheme of reactive pathways operates, potentially affecting the ArOH
pollutants and, in some cases, the very sensitizer.
In this presentation, we compile and discuss the results published by our group and others
related with the study of the kinetic behavior and the mechanism of the dye-promoted
photooxygenation of several representative ArOH, some of them with the basic molecular
structures of known commercial products. We examine the experimental conditions that
maximize the photodegradation efficiencies of all these ArOH compounds, under dyesensitized photooxidation conditions similar to those frequently found in nature, with a
natural dye sensitizer such as Riboflavin (Rf) (vitamin B2) and related compounds [¡Error!
Marcador no definido.,10]. These pigments are normally present in natural waters of lakes,
24
rivers and seas in sensitizing concentrations [11]. The usual mechanism of action of these
dyes is rather complex, in many cases with the concurrent involvement of ROS. This
information can make possible the evaluation and partially modeling of the fate of a particular
ArOH contaminant in the environment, as well as the prediction of the prevalence of a given
photoreaction mechanism as a function of the particular ArOH involved, relative
concentrations of sensitizer and substrate, local oxygen availability, pH of the medium, and
extent and quality of the irradiation doses, among others. Finally, and as a remarkable point,
we consider that the adequate managing of these variables, especially for phenolic pesticides,
could allow the design of “degradable contaminants” with a tunable residence time in nature
under defined environmental conditions. In this case, a sort of interdisciplinary research
should be necessary in order to fit the designed chemical structure to the practical
effectiveness of the proposed ArOH derivative.
Acknowledgements
Thanks are given to Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET),
Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT), Secretaría de Ciencia y
Técnica de la Universidad Nacional de Río Cuarto (SECyT UNRC), all from Argentine, and
Consejo Superior de Investigaciones Científicas (CSIC) from Spain, for financial support. We
deeply acknowledge to colleges and coworkers that have collaborated in the pieces of
research work herein included.
References
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H. D. Burrows, L. M. Canle, J. A. Santaballa, S. Steenken, J. Photochem. Photobiol. B: Biol. 67 (2002) 71.
B. Bayarri, E. Carbonell, J. Gimenez, S. Esplugas, H. García, Chemosphere 72 (2008) 67.
M. P. Montaña, W. A. Massad , F. Amat-Guerri, N. A. García. J. Photochem. Photobiol. A: Chem. 193
(2008) 103.
[5] C. Tomlin, The Pesticide Manual. Edited by British Crop Protection Council and The Royal Society of
Chemistry, London, UK 1994.
[6] Y. Barbieri, W. A. Massad, D. J. Díaz, J. Sanz, F. Amat-Guerri, N. A. García, Chemosphere 73 (2008) 564.
[7] Y. Zuo, K. Zhang, Y. Deng, Chemosphere 63 (2006) 1583.
[8] M. Díaz, M. Luiz, P. Alegretti, J. Furlong, F. Amat-Guerri, W. Massad, S. Criado, N. A. García, J.
Photochem. Photobiol. A: Chem. 202 (2009) 221.
[9] Y. Zhang, J. L. Zhou, B. Ning, Water Res. 41 (2007) 19.
[10] M. Sikorski, E. Sikorska, A. Koziolowa, R. Gonzalez Moreno, J. L. Bourdelande, R. P. Steer, F. Wilkinson
J. Photochem. Photobiol. B: Biol. 60 (2001) 114.
[11] A. Momzikoff, R. Santus, M. Giraud, 1983. Mar. Chem. 12 (1983) 1.
25
Role of Carotenoids in Photosystem II (PSII) Reaction Centers
S. E. Braslavsky, A. R. Holzwarth
Max-Planck Institute for Bioinorganic Chemistry, Mülheim a.d. Ruhr, Germany
Carotenes play an important role as photoprotectors in photosynthesis, quenching both triplet
states and singlet oxygen. The published 3 Å resolution structure of photosystem (PS) II
resolved two β-carotenes in the reaction centre (RC). The β-carotene in the D1-branch is 20 Å
away from the D1-chlorophyll (ChlD1) whereas the D2-carotene is only 13.2 Å away from
ChlD2 [1].
Scheme 1: Cofactor arrangement in closed PS II RC, showing the distances from the
accessory chlorophylls to the respective carotene. Note the negative charge on the accepting
quinone QA for the closed RC. Modified from [1].
The general protection mechanism of carotenoids is the quenching of triplet (bacterio)-Chls
(3BChl), both in photosynthetic antennae, and in RCs. In bacterial RCs a carotenoid located in
the B-branch quenches the RC triplet BChl (3BChl) by a Dexter mechanism, producing triplet
carotene (3Car). Carotenoids act also as electron relay in conditions of over-reduction of the
acceptor side in the PS II RCs, delivering electrons to the P680•+ radical from cytochrome b599
or/and accessory chlorophyll (ChlZ) in D2. Furthermore, the two β-carotenes also scavenge
singlet oxygen before it damages the PS II RC.
In isolated RCs of PS II, i.e., the D1-D2-cyt b559 complex, which lacks QA, the forward
electron transport can not proceed beyond the first two radical pairs (RPs) and the chargeseparated singlet state P680+-Pheo− forms a triplet RP (3RP±) via the RP dephasing mechanism
in high yield. The 3RP± then recombines to the RC 3Chl state. The yield of 3Car in isolated
D1-D2-cyt b559 RCs has been reported as very low (< 3 %), whereas the triplet yield of the
primary electron donor Chl has been found to be high (ranging from 30 % to 50 % [2]).
Laser-induced optoacoustic studies (LIOAS) with D1-D2-cyt b559 complexes with variable
carotene content [on average from < 0.5 to 2 per reaction center (RC)] showed that the
structural volume change, ∆V1, corresponding to the formation of P680+ Pheo−, strongly
depends on the Car content; it is ca. − 2.5 Å3 molecule−1 for samples with < 0.5 Car on
average, decreases (in absolute value) to −0.5 ± 0.2 Å3 for samples with an average of 1 Car,
and remains the same for samples with two Cars per RC. This suggests that the Car molecules
induce changes in the ground-state RC conformation, an idea which was confirmed by
preferential excitation of Car with blue light, which produced different carotene triplet
lifetimes in samples with 2 Car compared to those containing less carotene. We concluded
that the two β-carotenes are not structurally equivalent [3].
26
We decided to search for the possible production of 3Car in closed RCs (See Fig. 1), in
particular to analyze the 3Chl decay in intact PS II cores and compare it with the behaviour in
open RCs. Nanosecond transient absorption spectroscopy was used to study RC chlorophyll
triplet quenching by carotenoid in intact PS II cores from T. elongatus with closed RCs. We
found a triplet β-carotene (3Car) signal (absorption difference maximum at 530 nm) that is
sensitized by the RC 3Chl with a formation time of ca. 190 ns, has a decay time of 7 µs and is
formed with a quantum yield between 10 and 20 %. The 3Car signal is assigned to the βcarotene on the D2 branch of the RC [4].
Figure 1: Lifetime-associated difference spectra
(LADS) upon excitation of the closed PS II RC in PS II
cores showing the formation in 190 ns and the decay in
7 µs of 3Car [4].
We thus propose a new photoprotection mechanism
operative in closed RCs where – as a consequence of
the negative charge on the quinone QA – the triplet 3Chl
is formed by the RP mechanism on the normally
inactive D2 branch where it can be subsequently
quenched by the D2 β-carotene (Scheme 2). We suggest
that the D2 branch becomes active when the RCs are closed under high fluence conditions.
Under these conditions the D2 branch plays a photoprotective role. This interpretation allows
combining many seemingly inconsistent observations in the literature and reveals the so far
missing RC triplet quenching mechanism in PS II. The newly proposed mechanism also
explains the reason why this RC triplet quenching is not observed in isolated D1-D2-cyt b559
RCs. If QA is either not present at all (as in the isolated RC) or is not charged (as in open RCs
or with doubly reduced QA) then the RC 3Chl is formed on the D1 branch. The D1 branch 3Chl
can not be quenched due to the large distance to the β-carotene. This interpretation is in line
with the well-known 3RC quenching mechanism in bacterial RCs, where also the carotenoid
in the B-branch (analogous to the D2 branch) of the RC becomes the quencher.
Scheme 2: Cartoon depicting the proposed
participation of the D2 branch through the
quenching by CarD2 of the 3ChlD2 formed due to
closing (QA reduction) of the RC by excess
fluence.
References
[1] B. Loll, J. Kern, W. Saenger, A. Zouni, J. Biesiadka, Nature, 438 (2005) 1040.
[2] I. Yruela, M.S. Churio, T. Gensch, S.E. Braslavsky, A.R. Holzwarth, J. Phys. Chem., 98 (1994) 12789.
[3] A. Losi, I. Yruela, M. Reus, A.R. Holzwarth, S.E. Braslavsky, Photochem. Photobiol. Sc. 3 (2003) 722.
[4] V. Martínez-Junza, M. Szczepaniak, S. E. Braslavsky, J. Sander, M. Nowaczyk, M. Rögner,
A. R. Holzwarth Photochem. Photobiol. Sc. 7 (2008) 1337.
27
28
INVITED LECTURES
29
30
Photochemistry and Quantum Chemistry: the New Frontiers
L. Serrano-Andrés, M. Merchán, V. Sauri, A.Giussani
Instituto de Ciencia Molecular, Universitat de València, Ap. 22085, ES-46071 Valencia, Spain
[email protected]
The proper description of the chemistry of the excited state requires theoretical treatments
much more complex than those employed to model ground-state phenomena. High-level ab
initio quantum chemical methods for excited states, general enough to deal with a plethora of
electronic structure problems, are scarce and only those based on multiconfigurational wave
functions have the accuracy needed to determine conclusively photochemical processes at a
molecular level, which strongly rely on the adequate representation of degenerate structures
such as conical intersections between interacting electronic states. In this lecture we will first
revise the status of the quantum chemical methods and the computational strategies employed
to solve the time-independent Schrödinger equation for excited states and determine potential
energy hypersurfaces (PEHs) and interaction couplings, with emphasis in the most employed
approaches like CASPT2, coupled-cluster (CC) and TDDFT. Recent developments such as
the integral Choleski or RI transformations or the RASPT2 method will be shown to cross
new frontiers to extend the applicability of the ab initio approaches to larger and more
complex systems and problems [1-4].
Once the static, time-independent description of the PEHs, has been performed on accurate
quantum chemical grounds, and only then, the theoretical model can be extended toward more
realistic frameworks. Hybrid quantum mechanics − molecular mechanics (QM/MM) can be
applied to simulate the effects of the environment and the extension of the system to large
macromolecular sizes [4-9]. The advantages and drawbacks of these techniques applied to
excited state quantum chemistry will be addressed. Finally, and in order to predict
photochemical reaction rates, states lifetimes, and quantum yields, the statistical and
dynamical aspects of the photochemical problem have to be considered by solving the timedependent Schrödinger equation on quantum chemical grounds in small systems or by
restricting the degrees of freedom or using semiclassical treatments [10,11].
The lecture will not focus on the mathematical or methodological aspects of the problems but
on their practical side, illustrating the strengths and flaws of the different approaches and
trying to analyze the expected level of predictability to deal with the photochemical problems,
depending on the size of the problem, its complexity, etc. Examples such as the photophysics
and photochemistry of DNA components, biological switches, phototherapeutic compounds
or molecular devices with prospective nanotechnological uses will be used to illustrate the
capability of present quantum chemistry to deal with photochemical problems [12-16].
References
[1] M. Merchán, L. Serrano-Andrés, "Ab Initio Methods for Excited States". In: "Computational
Photochemistry".
Ed. M. Olivucci, Elsevier, Amsterdam (2005).
[2] L. Serrano-Andrés, M. Merchán, J. Mol. Struct., Theochem, 729 (2005) 99.
[3] L. Serrano-Andrés, M. Merchán, R. Lindh, J. Chem. Phys., 122, (2005) 104107.
[4] F. Aquilante, L. De Vico, N. Ferré, G. Ghigo, P-.A. Malmqvist, T. Pedersen, M. Pitonak, M. Reiher, B. O.
Roos, L. Serrano-Andrés, M. Urban, V. Veryazov, R. Lindh,, J. Comp. Chem.. (2009) In press.
[5] D. Roca-Sanjuán, G. Olaso-González, M. Rubio, P. B. Coto, M. Merchán, N. Ferré, V. Ludwig, L. SerranoAndrés, Pure & App. Chem., 81 (2009) 743.
[6] N. Ferré, J. G. Ángyán, Chem. Phys. Lett. 356 (2002) 331.
[7] H. M. Senn, W. Thiel, Angew. Chem. Int. Ed., 48 (2009) 1198.
31
[8] V. Ludwig, M. S. Amaral, Z. M. Costa, A. C. Borin, S. Canuto, L. Serrano-Andrés, Chem. Phys. Lett.. 463
(2008) 201.
[9] L. Serrano-Andrés, M. P. Fülscher, G. Karlström, Int. J. Quantum Chem., 65 (1997) 167.
[10] X. Yang, K. Liu, Eds., Modern Trends in Chemical Reaction Dynamics, World Scientific, Singapore, 2004.
[11] L. Serrano-Andrés, M. Merchán, and A. C. Borin, J. Am. Chem. Soc. 130 (2008) 2473.
[12] L. Serrano-Andrés, M. Merchán: "Photostability and Photoreactivity in Biomolecules: Quantum Chemistry
of Nucleic Acid Base Monomers and Dimers". In: "Radiation Induced Molecular Phenomena in Nucleic Acid: A
Comprehensive Theoretical and Experimental Analysis". Eds. M. K. Shukla and J. Leszczynski, Springer, The
Netherlands, Chapter 16, pp 435-472 (2008)
[13] L. Serrano-Andrés, M. Merchán, J. Photochem. Photobiol. C: Photochem. Rev., 10 (2009) 21.
[14] G. Olaso-González, M. Merchán, L. Serrano-Andrés, J. Am. Chem. Soc., 131 (2009) 4368.
[15] L. Serrano-Andrés, M. Merchán, A. C. Borin. Proc. Natl. Acad. Sci. USA, 103 (2006) 8691.
[16] J. J. Serrano-Pérez, G. Olaso-González, M. Merchán, L. Serrano-Andrés, Chem. Phys. In press (2009)
[17] L. Serrano-Andrés, D. Klein, P. v. R. Schleyer, J. M. Oliva, J. Chem. Theor. Comp.. 4 (2008) 1338.
[18] See also publication list in: http://www.uv.es/qcexval.
IC ππ∗/nπ∗/gs
IC ππ∗/nπ∗/gs
ππ∗
ππ∗
IC ππ∗/gs
A
CI
Absorption
gs
Emission
ππ∗min
F
gs
Figure 1. Interplay between experiment and theory is required to progress in the field of molecular
photochemistry. Modern trends and frontiers in the quantum chemistry of the excxited state will be reviewed.
32
Fotoquímica en espacios confinados. Desde estudios básicos hacia
aplicaciones
Hermenegildo García
Instituto Universitario de Tecnología Química CSIC-UPV, Universidad Politécnica de Valencia, 46022
Valencia, Spain. E-mail: [email protected]
La fotoquímica molecular pretende determinar el comportamiento de los estados
electrónicos excitados en disolución y en medios tan isotrópicos y homogéneos como sea
posible. De esta manera llega a determinarse el comportamiento intrínseco de una molécula y
cuales son los mecanismos de reacción disponibles para los estados excitados. Estos estudios
de fotoquímica molecular establecen que en un gran número de casos existen distintos
caminos de reacción que compiten y pueden ocurrir simultáneamente. Ello determina que
numerosos procesos fotoquímicos en disolución ocurran con una selectividad baja.
Inspirados en sistemas biológicos y al objeto de conseguir ganar control sobre los
procesos fotoquímicos se ha venidos desarrollando desde los años 80 una fotoquímica
supramolecular donde el comportamiento de un cromóforo en disolución se modifica y se
controla mediante la formación de un complejo que limita los procesos disponibles, llegando
a favorecer alguno de ellos.
En este contexto en la presentación se van a describir los trabajos del grupo en el campo
de la fotoquímica supramolecular empleando bien cápsulas orgánicas solubles en medios
acuosos y que forman complejos supramoleculares una elevada constante de formación hasta
materiales inorgánicos microporosos que permiten la inclusión del cromóforo en el interior de
los espacios vacíos de la estructura.
Entre los sistemas cuya fotoquímica se comentará se encuentran aquellos donde un
cromóforo orgánico se encuentra alojado en el interior de cucurbituriles. Los cucurbituriles
son oligómeros cíclicos de cinco a ocho unidades de glicoluriles enlazados por puentes
metileno. La molécula posee una forma de calabaza hueca en cuyo interior es posible
incorporar colorantes orgánicos. La Figura 1 muestra el modelo molecular de uno de estos
complejos supramoleculares huésped-hospedador cuya fotoquímica es diferente a la que se
observa cuando el huésped se encuentra en disolución. Una de las aplicaciones de estos
sistemas es como lenguas y narices químicas para la detección y cuantificación de
compuestos químicos.
33
Figura 1. Modelos moleculares del catión 2,4,6-trifenilpirilio en el interior del cucubituril 7
(izquierda) y 8 (derecha) formando un complejo 1:1 (CB[7]) y 2:1 (CB[8]) y los perfiles temporales
del estado excitado triplete en disolución y en dichos complejos.
Por otra parte, las zeolitas son sólidos microporosos cuya estructura cristalina define canales y
cavidades en los cuales es posible incluir cromóforos. En este caso las propiedades fotofísicas y el
comportamiento fotoquímico del huésped incluido pueden sufrir modificación por su encapsulación
en el interior de los vacíos de la estructura cristalina del material. Entre los efectos más generales de
la incorporación en una matriz rígida uno de los más generales es el aumento de la estabilidad del
huésped ocluido y un aumento de los tiempos de vida de los estados excitados como consecuencia
de que los procesos de relajación vibracionales no radiativos se encuentran desfavorecidos con
respecto a disolución. Otros silicatos, fosfatos y óxidos poseyendo espacios intracristalinos
accesibles también se comportan de manera similar (Figura 2).
Figura 2. Modelo molecular de un complejo de rutenio tris bipiridilo y un derivado de fullereno
anclados covalente en el interior de las láminas de un fosfato de zirconio laminar.
En la presentación se comentarán algunas aplicaciones de estos sistemas como sensores
fluorimétricos, como fotocatalizadores capaces de descomponer compuestos empleados en la guerra
química y para la ruptura del agua con luz visible.
34
Molecularly imprinted polymers and fluorescence for water and food quality
control by molecular recognition
Guillermo Orellana1, María Cruz Moreno-Bondi2
Elena Benito-Peña,1,2 Mónica Álvarez-Pérez,1 Jolanta Zdunek2
Optical Chemosensors & Applied Photochemistry Group, Dpmt. of Organic Chemistry (1) and Dpmt. of Analytical
Chemistry (2), Faculty of Chemistry, Universidad Complutense de Madrid, E-28040 Madrid (Spain);
[email protected]; www.ucm.es/info/gsolfa
Molecular imprinting is a versatile technique that allows the design and preparation of tailormade recognition materials that try to mimic antibodies. These organic polymers contain specific
sites (for binding or catalysis) with a shape and geometry of functional groups complementary to
those present in a template molecule (target analyte). During polymer preparation, the selected
template molecule is allowed to bind, covalent or non-covalently, with functionalized monomers
that are being polymerized in the presence of a cross-linker to form a 3-D structure [1,2]. After
template removal the polymer will bear specific recognition sites with complementary size,
geometry and arrangement of functional groups to the target analyte (Figure 1). The recognition
process will be determined by the amount of functional groups that participate in the interaction, the
shape of the cavity and the type of interaction between template and polymer during
macromolecular synthesis.
MONOMERS
CROSS-LINKER
EXTRACTION
REBINDING
POLYMERIZATION
TEMPLATE
Figure 1. Scheme of the synthesis of a molecularly imprinted polymer to mimic the antibody features.
Molecularly imprinted polymers (MIPs) show physical robustness and are resistant to harsh
conditions (high temperatures, solvents, etc.). Moreover, the cost of MIPs is lower and their
preparation is easier than that of antibodies. However, non-covalent MIPs are usually synthesised in
organic solvents and template recognition relies on ionic or hydrogen bonds that are less effective in
water; additionally, the polymer synthesis usually involves a lengthy trial and error procedure more
than a rational design. The lack of labelled derivatives and recognition monomers for signalling the
binding event in the analysis of optically silent species is still a limitation for the development of
optical sensors.
Anyhow, MIPs are finding many applications in current Analytical Chemistry. They have
been used as recognition elements for an analyte or a group of determinands in affinity
chromatography, solid phase extraction (SPE), immuno-type binding assays and for sensor
development. In this presentation we will show several approaches that have been applied to
overcome some of the above mentioned limitations for the development of MIPs in fluorescence
biomimetic assays or optical sensing. Optimisation of the polymer composition upon application of
a experimental design to identify the factors that have a larger influence on the MIP selective
35
binding, the design and synthesis of novel fluorescent analogues of the print molecule [3],
characterization of the materials [4], synthesis of nano-MIPs (beads, hairs) and the application of
tailored MIPs and fluorescence techniques to the analysis of antibiotics in water [5,6] or mycotoxins
[7,8] in food samples will be presented in the lecture.
Acknowledgements. This work is being funded by the Madrid Community Government (grant S505/AMB-00364, "FUTURSEN"), the Spanish Ministry of Science and Innovation (ref. CTQ200615610-C02_BQU), the EU Marie-Curie RTN Programme (MRTN-CT-2006-033873), the European
Social Fund, the European Funds for Regional Development and by the UCM-B. Santander (GR5808-910072).
[1] M.C. Moreno-Bondi, M. E. Benito Peña, J.L. Urraca, G. Orellana, Topics Curr. Chem. 2009 (in the press).
[2] M.C. Moreno-Bondi, F. Navarro-Villoslada, E. Benito-Peña, J. L. Urraca, Curr. Anal. Chem. 2008, 4, 316-340.
[3] E. Benito-Peña, M.C. Moreno-Bondi, S. Aparicio, G. Orellana, J. Cederfur, M. Kempe, Anal. Chem. 2006, 78,
2019-2027.
[4] J.L. Urraca, M.C. Carbajo, M.J. Torralvo, J. González-Vázquez, G. Orellana, M.C. Moreno-Bondi, Biosens.
Bioelectron. 2008, 24, 155-161.
[5] J.L. Urraca, M.C. Moreno-Bondi, G. Orellana, B. Sellergren, A. J. Hall, Anal. Chem. 2007, 79, 4915-4923.
[6] E. Benito-Peña, S. Martins, G. Orellana, M.C. Moreno-Bondi, Anal. Bioanal. Chem. 2009, 393, 235-245.
[7] J.L. Urraca, M.D. Marazuela, E.R. Merino, G. Orellana, M.C. Moreno-Bondi, J. Chromatography A 2006, 1116,
127-134.
[8] F. Navarro-Villoslada, J.L. Urraca, M.C. Moreno-Bondi, G. Orellana, Sensors Actuators B: Chem. 2007, 121, 67-73.
36
Interruptores y motores moleculares biomiméticos
D. Sampedro1
1
Departamento de Química, Universidad de La Rioja
Grupo de Síntesis Química de La Rioja, Unidad Asociada al C.S.I.C.
El progreso de la humanidad siempre ha estado unido a la construcción de nuevas máquinas. En los
últimos 50 años, además de producirse un incremento en su complejidad, la progresiva
miniaturización de sus componentes ha provocado increíbles avances técnicos. El próximo avance
en miniaturización no sólo disminuirá el tamaño e incrementará la potencia de los ordenadores o los
teléfonos móviles, sino que también abrirá el camino para nuevas técnicas en el campo de la
medicina, el medio ambiente, la energía y los materiales.
Hasta ahora, la miniaturización se ha conseguido principalmente por métodos “descendentes” que
están alcanzando sus límites físicos (cientos de nanómetros). Sin embargo, la miniaturización puede
llevarse más allá por métodos “ascendentes”. Comenzando por moléculas, las más pequeñas
entidades de materia con distintas formas y propiedades, los químicos han construido máquinas
moleculares del tamaño de nanómetros. Inspirados por el descubrimiento de un creciente número de
fascinantes motores biomoleculares cruciales en el funcionamiento de células vivas, el estudio de
motores sintéticos a escala molecular es una de las áreas más apasionantes de la ciencia en la
intersección de la química, la física y la biología molecular [1].
La solución de la Naturaleza al control de la organización, lanzamiento de señales y movimiento
lineal o rotatorio no sólo son muy elegantes sino particularmente fascinantes si se considera el
diseño y la síntesis de sistemas moleculares artificiales con las mismas funciones. Entre los más
maravillosos ejemplos en la Naturaleza está el sistema de replicación de ADN/ARN, el complejo
recolector de luz de las porfirinas y la isomerización cis-trans del retinal en los procesos de la
visión.
Las máquinas a nivel molecular operan a través de movimientos nucleares de gran amplitud,
originados por reacciones químicas que conducen a verdaderos desplazamientos de alguno de los
componentes de la máquina. Además, para que una máquina molecular funcione, se le debe
suministrar energía a su motor. La energía lumínica puede originar la fotoisomerización de una
molécula con enlaces dobles –C=C– o –C=N– que lleve asociado un cambio geométrico. El uso de
luz para estas aplicaciones ofrece una serie de ventajas: no genera productos de desecho, la luz
puede encenderse y apagarse fácil y rápidamente, y un láser se puede emplear en espacios pequeños
y tiempos cortos.
A partir de estos modelos naturales, nos centraremos en el diseño y caracterización fotoquímica de
motores e interruptores moleculares. El desarrollo de estos sistemas se inspira en el proceso de la
visión, en el que el paso químico básico es una isomerización cis-trans fotoinducida. El cromóforo
de las rodopsinas, una base de Schiff protonada [2], constituye un ejemplo de un interruptor
modelado por la evolución biológica. Por ejemplo, en la rodopsina bovina, la fotoisomerización
selectiva del cromóforo 11-cis se produce a través de una transición de tipo π → π* a un estado
excitado (S1) donde se mantiene sólo 150 fs y produce el isómero todo-trans en estado fundamental
con un 67% de rendimiento cuántico [3]. Aunque este compuesto supone un excelente modelo para
el diseño de interruptores moleculares, su utilización en disolución conlleva una serie de
isomerizaciones no selectivas y un tiempo de vida en el estado excitado en el rango de
picosegundos. Por tanto, tomando como punto de partida la estructura química del cromóforo del
37
retinal, trataremos de diseñar nuevos sistemas que puedan actuar como interruptores moleculares
biomiméticos eficientes.
En esta comunicación se presentarán algunos de los resultados obtenidos en el diseño, síntesis y
caracterización fotoquímica de interruptores y motores moleculares basados en la estructura del
cromóforo del retinal (Figura1). Basándonos en cálculos teóricos [4] podemos diseñar la estructura
química que potencialmente pueda mostrar mejores propiedades fotoquímicas. Además, se
presentarán ejemplos de compuestos que permiten el aprovechamiento de la luz solar para llevar a
cabo la fotoisomerización [5], lo que supone una gran ventaja para las aplicaciones prácticas de
estos compuestos.
R2
R4
R5 O
N R
2
R1
N
R1
R3
Figura 1. Estructura básica de algunos de los interruptores moleculares estudiados.
Referencias
[1] V. Balzani, A. Credi, M. Venturi, Molecular Devices and Machines. A journey into the nanoworld, Wiley-VCH:
Weinheim, 2003.
[2] D. C., Teller, T. Okada, C. A. Behnke, K. Palczewski, R. E. Stenkamp Biochemistry 2001, 40, 7761.
[3] R. A. Mathies, J. Lugtenburg, Handbook of Biological Physics, edited by D. G. Stavenga, W. J. de Grip, E. N. Pugh,
Elsevier: Amsterdam, 2000; Vol. 3, p 56-90.
[4] D. Sampedro, A. Migani, A. Pepi, E. Busi, R. Basosi, L. Latterini, R. Elisei, S. Fusi, F. Ponticelli, V. Zanirato, M.
Olivucci J. Am. Chem. Soc., 2004, 126, 9349.
[5] L. Rivado-Casas, D. Sampedro, P. J. Campos, S. Fusi, V. Zanirato, M. Olivucci J. Org. Chem., en prensa.
38
Buffer-Mediated Ground- and Excited-State Proton Exchange Reactions at the
Single Molecule (FCS) and Ensemble Level (TCSPC).
Eva M. Talavera, Luis Crovetto, Angel Orte, Maria J. Ruedas-Rama, Jose M. Paredes, Patricia Lozano-Vélez and José
M. Álvarez-Pez,
1
Department of Physical Chemistry, University of Granada, Campus of Cartuja, 18071 Granada, Spain.
Fluorescein displays four prototropic forms in aqueous solution. At near physiological pH only the
monoanion/dianion equilibrium is relevant. The dianion shows absorption coefficient and
fluorescence quantum yield larger than monoanion, and these differences are the basis of the
fluorescein applications at near neutral pH. Nevertheless, we showed that fluorescein displays an
excited-state proton transfer, ESPT, reaction which interconvert the mono- and dianion forms in the
presence of a suitable proton donor-acceptor. This ESPT reaction strongly alter the steady state
fluorescent signal [1]. Our research in the last few years involved the kinetic characterization of
such reactions and their effect on fluorophores’ properties, as well as the development of
fluorescein derivatives that may be suitable as sensors making use of tunable fluorescence features
promoted by the ESPT reactions.
Since fluorescein is a frequently used fluorescent label in biological systems such as proteins, it was
of interest to know whether amino acids with acidic side chains are able to induce ESPT reactions
in fluorescein. We selected (±)-N-acetyl aspartic acid, N-AcAsp, as a model of donor-acceptor
which mimics the interaction of the aspartic acid residues with the fluorescent label in native
proteins. We determined the relevant rate constants of the ESPT reaction and the spectral
parameters related to absorption and emission, kinetic equations and expressions for the
fluorescence decay surface. For this, we made use of a new global compartmental analysis
approach, GCA [2], that allows to determine all rate constants and spectral parameters once the
necessary and sufficient experimental conditions are established [3]. The GCA approach turned out
to be a valuable tool to broaden our studies to other fluorescein derivatives, such as Oregon Green
488 (OG488), one of the most popular fluorescein derivatives because of its resistance to
photodegradation and unchanging absorption and fluorescence properties in the physiological pH
range. Depending on the experimental conditions OG488 presented ESPT reactions following a
two-state [4] and three-state excited-state kinetic scheme, based on the coexistence of three
prototropic forms. The later was solved by using a novel three-compartments GCA [5]. The relevant
parameters from GCA have high predictive power, allowing to foresee time-resolved fluorescence
emission data, and its correlation with steady-state fluorescence spectra [6].
On a parallel research line, we explore other fluorescein derivatives. Fluorescein consists in two
orthogonal moieties, the benzoic acid and the 6-hydroxy-3H-xanthen-3-one. When the carboxylic
group of fluorescein is replaced with another functional group (-CH3 or -OCH3), the fluorescence of
the neutral forms may be near to zero, whereas the quantum yield of the anion form is close to 1.
We investigated the photophysics at the ensemble level of the fluorescein derivative; 9-[1-(2Methoxy-5-methylphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-I) [7]. This compound shows the
characteristic fluoresceins’ ESPT reaction promoted by the presence of phosphate buffer. In
addition, it displays a single lifetime at particular experimental conditions. Unfortunately, its
fluorescence quantum yield is low and it has little use in analytical or biophysical applications.
Therefore we direct our efforts to study the photophysics of 9-[1-(2-Methyl-4-methoxyphenyl)]-6hydroxy-3H-xanthen-3-one (TG-II), since it is highly fluorescent when the xanthene moiety is in
the anion form, but its quantum yield is near zero when it is protonated, characterizing a
39
photoswitchable “on/off” behaviour. The high quantum yield of TG-II along with the possibility of
sensing phosphate concentration makes interesting its study at both ensemble and single molecule
(SMF) level [8]. The increase in phosphate concentration from 0 to 0.3 M decreases the lifetime
from 3.7 ns to 3.0 ns at pH 7.0. Interestingly, this sensitivity towards phosphate buffer
concentration is consistent in both the ensemble level and for decay traces collected at the singlemolecule regime. The environmental sensitivity of the lifetime makes TG-II a promising dye for
screening the chemical concentration of phosphate in single molecule experiments at near
physiological pH values.
Additionally, we have shown how the presence of buffer-mediated proton transfer reactions also
affects the ground state protonation state. This has important implications when these fluorophores
are employed in fluorescence correlation spectroscopy (FCS). Thus, buffer-mediated proton transfer
reactions make the fluorescence autocorrelation function from the dyes highly sensitive to
phosphate buffer concentration at near physiological pH [9]. The analysis of FCS curves provided
the kinetic parameters of buffer-mediated proton transfer reactions in the ground state for TG-II.
Interestingly, these are the same than those for the reaction in excited state, confirming the equal
nature of the process either in the ground- or excited-state. This implicates that the ESPT reaction is
promoted when a sufficiently high concentration of buffer makes the reaction fast enough to
compete with fluorescence emission.
In summary, here we have shown recent developments in understanding the phenomenology of the
proton transfer reaction, and our efforts to take advantage of this to explore the feasibility of sensors
and “on/off” probes capable of investigating the environmental phosphate concentration in a small
volume at near physiological pH.
References
[1] J. M. Alvarez-Pez, L. Ballesteros, E. M. Talavera, J. Yguerabide. J. Phys. Chem. A 2001, 105, 6320-6332.
[2] L. Crovetto, A. Orte, E. M. Talavera, J. M. Alvarez-Pez, M. Cotlet, J. Thielemans, F. C. De Schryver, N. Boens. J.
Phys. Chem. B 2004, 108, 6082-6092.
[3] N. Boens, N. Basaric´, E. Novikov, L. Crovetto, A. Orte, E. M. Talavera, J. M. Alvarez-Pez. J. Phys. Chem. A 2004,
108, 8180-8189.
[4] A. Orte, L. Crovetto, E. M. Talavera, N. Boens, J. M. Alvarez-Pez. J. Phys. Chem. A 2005, 109, 734-747.
[5] A. Orte, E. M. Talavera, A. L. Maçanita, J. C. Orte, J. M. Alvarez-Pez. J. Phys. Chem. A 2005, 109, 8705-8718.
[6] A. Orte, R. Bermejo, E. M. Talavera, L. Crovetto, J. M. Alvarez-Pez. J. Phys. Chem. A 2005, 109, 2840-2846.
[7] L. Crovetto, J. M. Paredes, R. Rios, E. M. Talavera, J. M. Alvarez-Pez. J. Phys. Chem. A 2007, 111, 13311-13320.
[8] J. M. Paredes, L. Crovetto, R. Rios, A. Orte, J. M. Alvarez-Pez, E. M. Talavera. Phys. Chem. Chem. Phys., 2009, 11,
5400-5407.
[9] J. M. Paredes, A. Orte, L. Crovetto, J. M. Alvarez-Pez, R. Rios, M. J. Ruedas−Rama, E. M. Talavera. (2009
submitted).
40
ORAL PRESENTATIONS
41
42
Molecular injection of fluorescent drugs in Leishmania parasites
V. Hornillos1,2, J. R. Luque3, B. G. de la Torre4 , D. Andreu4, L. Rivas3, F. Amat-Guerri2, A. U. Acuña1
1
Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid
Instituto de Química Orgánica, CSIC, Juan de la Cierva 3, 28006 Madrid
3
Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid
4
Dpt. Ciéncies Exp. Salut, Univ. Pompeu Fabra, Dr. Aiguader 80, 08003 Barcelona
2
Miltefosine (n-hexadecylphosphocholine, MT, Fig. 1) is a synthetic phospholipid that recently
became the first effective oral drug for the treatment of a group of diseases caused by the infection
with Leishmania parasites [1]. In spite of the successful clinical application of the drug, the
molecular mechanism of the strong parasiticidal effects of MT, as well as its metabolism and
subcellular interactions, remain to be determined. Many important details of these processes can be
obtained by means of modern techniques of fluorescence high-resolution microscopy and similar
fluorescence-based experimental methods, provided that fully functional emitting analogues of the
drug are available. We recently developed several fluorescent analogues of MT that show high
leishmanicidal activity, not very different from that of the parent drug (Fig. 1). These compounds
proved to be of great help in unveiling important aspects of the antiparasitic effect of the drug at the
molecular level [2].
Figure 1. Fluorescent bioactive analogues of miltefosine.
Thus, it was possible to confirm in this way the presence of an efficient internalization mechanism
of the drug located within the parasite plasma membrane, that controls the intracellular MT
concentration. Parasites lacking the transport mechanism became resistant to miltefosine [3]. To
understand the leishmanicidal effects of the internalized drug, it is necessary to bypass this transport
chain and inject miltefosine directly within the cell protoplasm, a very difficult operation in the
specific case of Leishmania parasites.
An alternative way of introducing the drug within the parasite was developed as follows. We
synthesized first a thiolated fluorescent analogue of MT (MT-8C-BDP-3C-SH) as summarized in
Scheme 1. Independent experiments have shown that the leishmanicidal activity of this analogue is
similar to that of the parent drug. In addition, the analogue 1 presents very convenient absorbing
and emitting properties, as well as a high photostability (Fig. 2).
Scheme 1. Synthesis of MT-8C-BDP-3C-SH (1)
43
relative intensity (u.a.)
1.0
Φf= 0.7
0.8
-1
ε529 = 82000 M cm
-1
0.6
0.4
0.2
0.0
300
350
400
450
500
550
600
650
λ/nm
Figure 2. Absorption (black), corrected fluorescence (red) spectra and quantum yield of the miltefosine analogue MT8C-BDP-3CSH in ethanol solution, 10-6 M; T = 22 ºC.
In a next step, the “molecular injection” construct shown below was obtained (Fig. 3).
Figure 3. Structure of the molecular carrier of the fluorescent miltefosine analogue MT-8C-BDP-3C-SH.
It consists in a membrane-penetrant peptide (TAT) covalently bonded trough a disulphide bond to
analogue 1. In the presence of the parasite, this construct quickly transverses its complex
membrane. Once within the parasite cytoplasm, the spontaneous reduction of the disulphide bond
liberates the fluorescent drug 1. Preliminary experiments have shown the utility of this technique of
drug internalization in the study of MT leishmanicidal effects.
Acknowledgments
Work supported by Projects CSIC 200680F0171/2 and Min. San. Cons. (Spain) FIS PI061125.
References
[1] (a) S. L. Croft, et al. Clin. Microbiol. Rev. 19 (2006) 111-126. (b) S. L. Croft, K. Seifert, M. Duchêne Mol. Biochem
Parasit. 126 (2003) 165-172.
[2] (a) J. M. Saugar, J. Delgado, V. Hornillos, J. R. Luque-Ortega, F. Amat-Guerri, A. U. Acuña, L. Rivas. J. Med.
Chem. 50 (2007) 5994-6003. (b) V. Hornillos, E. Carrillo, L. Rivas, F. Amat-Guerri, A. U. Acuña. Biorg. Med. Chem.
Lett. 18 (2008) 6336-6339.
[3] J. M. Perez-Victoria, F. J. Perez-Victoria, A. Parodi-Talice, I. A. Jimenez, A. G. Ravelo, S. Castanys, F. Gamarro
Antimicrob. Agents Chemother. 45 (2001) 2468-2474.
44
A possible mechanism for photostability in polyglycine:
description of photoinduced proton transfer reaction paths
at the CASSCF//CASPT2 level of theory
M. Marazzi1, U. Sancho1, O. Castaño1, W. Domcke2, L. M. Frutos1
1
2
Department of Physical Chemistry, Pharmacy Faculty, University of Alcalá, Madrid, Spain
Department of Theoretical Chemistry, Technical University of Munich, Garching, Germany
A possible mechanism which permits biological macromolecules (DNA, proteins, etc.) to be
photostable was proposed to be photoinduced proton transfer. This mechanism consists in
converting the absorbed energy of the photon into vibrational energy which can be dissipated by the
environment.[1-4] Especially, the importance of hydrogen bonds in determining the secondary
structure of proteins (α-helix, β-sheet, etc.) is well known, and preliminary attempts to localize
theoretically the hydrogen transfer in such systems show an increasing interest in this topic.[5]
Within this research area, we focused the attention on the excited state evolution of a polyglycine
model (see Figure 1) after photon absorption, by ab initio calculations (CASSCF//CASPT2
methodology): a peptide bond is electronically excited, converting the excitation energy into
vibrational energy by a forward-backward proton transfer process, involving the hydrogen bond
between two peptides. This mechanism allows the system to recover its initial ground state
structure.
Figure 1. Investigated model: after excitation, the NH hydrogen of a peptide can be transferred to the carbonyl CO
group of the hydrogen bonded peptide. The ground state structure is recovered via a backward proton transfer process.
The two peptides are properly constrained to mimic a polyglycine environment.
This process implies the crossing between seven different electronic states, of which two charge
transfer states, four locally excited states and the ground state, providing to the system the property
of photostability (see Figure 2). We discuss the viability of this mechanism by studying the reaction
path of the process at the CASSCF//CASPT2 level of theory.
45
CT2
CT1
∗
πΑ−> πΑ
240
∗
πΒ−> πΒ
∗
nΑ−> πΑ
∗
nΒ−> πΒ
160
-1
∆E ( kcal mol )
200
S0
120
80
40
0
Reaction Coordinate
Figure 2. CASSCF energy levels scheme of the electronic states involved in the reaction path. Two charge transfer
states are found: CT1 (
) and CT2 (
), where A and B are the two peptides explicitly modeled. The
energy levels displayed in the legend are ordered as in the Franck Condon region.
References
[1] S. Perun, A.L. Sobolewski, W. Domcke J. Phys. Chem. A 110 (2006) 9031.
[2] A.L. Sobolewski, W. Domcke ChemPhysChem 7 (2006) 561.
[3] L.M. Frutos, A. Markmann, A.L. Sobolewski, W. Domcke J. Phys. Chem. B 111 (2007) 6110.
[4] Z. Lan, L.M. Frutos, A.L. Sobolewski, W. Domcke Proc. Nat. Acad. Sci. USA 105 (2008) 12707.
[5] D. Shemesh, .L. Sobolewski, W. Domcke J. Am. Chem. Soc. 131 (2009) 1374.
46
Excited state dynamics in aromatic molecules and clusters
Asier Longarte, Raúl Montero, Álvaro Peralta, Fernando Castaño
Dept. Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apt. 644, 48080 Bilbao Spain
Naphthalene (NPH) is a common cromophore present in many larger size molecules. The electronic
coupling between its two lowest electronic excited states, S1 (Lb) and S2 (La), represents a well
known case of non-adiabatic behaviour that has been used for years as a benchmark to test
theoretical models.[1] In general, the relative energy of the La and Lb states and the extent of their
coupling, determines the electronic spectroscopy and the photophysic properties of naphthalene
derivatives.
With the aim of gaining a better understanding of this coupling nature, in the present study, the
relaxation dynamics of isolated NPH and 1-aminonaphthalene (AMN) seeded in a supersonic
expansion was tracked following excitation to the lower S1-S3 (30000-41500 cm-1) excited states, at
the ultrafast time scale. The experiments were carried out in a time of flight mass spectrometer,
using a well known pump-probe ionization scheme (1+n’) that involves the probe of the molecule
by single or multiphoton ionization. Measurements were also carried out for water clusters of AMN
-AMN(H2O)n- containing from 1 to 3 water molecules, which permit to address the roll of the
solvent in the dynamics of the molecule in solution.
In the case of NPH the photophysics of the system is dominated by the ultrafast internal conversion
(IC) (τ =30 fs) from the La(S2) to the Lb(S1) state, when the former state is excited at 267 nm. The
IC is mediated by a conical intersection placed nearby the La surface minimum. [2] For AMN, the
substitution by the amino group stabilizes considerably the La(S2) and though ab initio
CASPT2//CASSCF calculations foresee a surface crossing between 1La and the lower 1Lb states, no
dynamical signature of it is observed in the time-dependent measurements. Two additional
relaxation channels, IC to the ground state and intersystem crossing, have been found for the La
state. [3] The solvation by water molecules induces dramatic changes in the relaxation of the AMN
molecule. The inclusion of a single water molecule deactivates the IC channel to the ground state,
while for the clusters containing two or three water molecules, ultrafast IC between the La to Lb and
excited states is observable in the transients. The results will be interpreted on the base of the
clusters geometry.
1
a)
Ion current (a.u.)
1
3 11 n m
30 8 n m
3 04 n m
2 98 n m
0
0
-200
0
200
400
600
Time (fs)
800
1000 1200
+
Fig.1 Short scale transient of NPH (red) and
NPH+-1 (blue) ions with excitation at 267 nm.
2 86 nm
28 0 nm
267 n m
235 n m 24 5 n m
0
2 00
400
600
Time (ps)
29 4 n m
800
1 0 00
1 2 00
+
Fig.2 Long scale transients of AMN collected at
different excitation energies.
[1] M. Stockburger, H. Gattermann, W. Klusmann, J. Chem. Phys. 63 (1975) 4519.
[2] Montero, R.; Longarte, A.; Martínez, R.; Sánchez Rayo, M. N.; Castaño, F. Chem. Phys. Lett. 468 (2009) 134.
[3] R. Montero, A. Longarte, Á. Peralta Conde, C. Redondo, Fernando Castaño, I. González-Ramírez, A. Giussani, L.
Serrano-Andrés, M. Merchán. In Press.
47
SECOND AND THIRD HARMONIC GENERATION FROM POWDER
QUINOXALINOPORPHYRINE DERIVATIVES
J.L. Bourdelande1, J. Hernando1, T. Khoury2, R.G. Clady2, T. Schmidt2, M.J. Crossley2
1
Department de Química, Universitat Autònoma de Barcelona, Bellaterra, Barcelona,
08193 Spain. E-mail: [email protected]
2
School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
Porphyrin-based chromophores have been recently reported to display Second Harmonic
Generation (SHG) and Third Harmonic Generation (THG) [1], two phenomena that are among the
most studied Non-Linear Optical (NLO) processes. Porphyrins are constituted by a tetrapyrrole
macrocycle with an extended delocalized π–system, which can be polarized by the effect of
electron donor or electron withdrawing groups attached to it. To date the effect on porphyrin NLO
performance of the electron donor and/or electron acceptor groups in positions 5,10,15,20 or in
pyrrolic positions of the macrocycle has been exhaustively studied [2]. However, so far such
investigations have only been performed in solution and films, and there is a lack of information
about the NLO properties of porphyrin derivatives in the solid state as powder. Recently, we have
proven that the NLO properties of this type of solid materials can be measured and compared with
the behavior of crystalline solid samples [3]. In this way some hidden and unexpected optical
properties could be reported for hybrid organic-inorganic materials [3b]. In addition, direct
measurement of NLO properties on powder samples removes the requirement for tedious
preparation of large monocrystals of the active optical material.
We have prepared several porphyrin derivatives which extensively delocalized π–system is
polarized by the addition of quinoxalino units [4]. In most of the cases, such units have been
attached to the tetrapyrrole macrocycle as to yield noncentrosymmetrical molecules, a requirement
for SHG activity. The NLO properties of the resulting molecular systems have been studied in the
solid state as powder. Some of these derivates show both efficient SHG and THG (see Figures 1 and
2 for the trisquinoxalinoporphyrin, 1) while the urea reference is only efficient as second harmonic
generator. We will discus the effect of the electron donating quinoxalino group, the electron
withdrawing nitro group and the coordination metal.
References
[1] a) M.O. Senge, M. Fazekas, E.G.A. Notaras, W.J. Blau, M. Zawadzka, O.B. Locos, E.M.N. Mhuircheartaigh,
Advanced Materials, 19 (2007) 2737. b) N.N. Kruk, Journal of Applied Spectroscopy, 75 (2008) 461.
[2] a) E. Annoni, M. Pizzotti, R. Ugo, S. Quici, T. Morotti, M. Bruschi, P. Mussini, Eur. J. Inorg. Chem. (2005) 3857 b)
Y. Zhang, X.-Z. You, J. Chem Res. (1999) 156.
[3] a) J.R. Herance, D. Das , J. Marquet, J.L. Bourdelande, H. Garcia, Chemical Physics Letters, 395 (2004), 186. b)
J.R. Herance, E. Peris, J. Vidal, J.L. Bourdelande, J. Marquet, H. García, Chemistry of Materials, 17(2005) 4097. c) M.
Alvaro, C. Aprile, M. Benitez, J.L. Bourdelande, H. Garcia, J.R. Herance, Chemical Physics Letters, 2005, 414, 66-70.
d) X. Vidal, J.R. Herance, J. Marquet, J.L. Bourdelande, J. Martorell, Applied Physics Letters, 91 (2007) 081116/1.
[4] M. J. Crossley, C. S. Sheehan, T. Khoury, J. R. Reimers, P. J. Sintic, New Journal of Chemistry, 32 (2008) 340.
48
Ar
Ar
N
N
N
H
N
N
1
H
N
N
N
Ar
Ar
N
N
Signal (arb. u.)
20000
532 nm (input 1064 nm)
10000
0
450
500
550
600
650
output wavelength (nm)
Figure 1: Intensity of the output signal when the powder trisquinoxalinoporphyrin, 1, is illuminated with an input
pulse of wavelength λ = 1064 nm.
5000
4800
4600
4400
4200
4000
3800
3600
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800,0
600,0
400,0
200,0
0
output spectrum (nm)
1000
scattered 780 nm fundamental
800
600
SHG signal
THG signal
400
200
1100
1200
1300
1400
1500
input wavelength (nm)
Figure 2: Output spectrum recorded when the powder trisquinoxalinoporphyrin, 1, is illuminated with an input
light of wavelength comprised in the interval 1100-1500 nm. The intensity of the output light is expressed in
arbitrary units with different colors.
49
Fluorescence Correlation Spectroscopy as a tool to Study
the Interaction Dye-Surfactant during the Micellization Process
J. Bordello, D. Granadero, M. Novo, W. Al-Soufi
Departamento de Química Física, Universidade de Santiago de Compostela
Self-aggregation of surfactants in aqueous solution has been extensively studied, primarily on
account of their wide range of technological applications.
Fluorescence spectroscopy can be used to study the micellization process by looking at the change
in the fluorescence intensity of the fluorophore, which changes its photophysical behaviour
depending on the change in the environment [1,2]. Recently, Zettl et al. have studied micelle
formation using fluorescence correlation spectroscopy (FCS) [3], which is of single-molecular
precision and can look at the heterogeneous behaviour of the aggregation process.
During the years, there have been several indications that the micelle formation is a multistep and
gradual process [4]. The formation of micelles at the cmc is preceded by the creation of smaller
assemblies, known as premicellar aggregates. The use of noncovalently bound dyes as labels to
follow this premicellization process is critical. Whether the premicelles can always be observed this
way, or to what extent the dye can induce their formation will depend on the affinity between dye
and aggregates.
In this work, we study the influence of hydrophobic fluorescent probes on the premicellization
process. Some preliminary investigations of this effect for probes with different hydrophobicity and
different surfactants are reported. Using FCS, we determine the variation of the translational
diffusion coefficient of the probe due to the increase in the diffusion times when it associates to the
surfactant aggregates [5,6,7].
References
[1] Barnadas-Rodriguez R., Estelrich J. J Phys Chem B 113.7 (2009) 1972
[2] Jaffer S, Sowmiya M, Saha S, Purkayastha P. J Colloid Interface Sci 325.1 (2008) 236
[3] Zettl H, Portnoy Y, Gottlieb M, Krausch G. J Phys Chem B 109 (2005) 13397
[4] Cui X, Mao S, Liu M, Yuan H, Du Y. Langmuir 24.19 (2008) 10771
[5] Al-Soufi W, Reija B, Novo M, Felekyan S, Kuhnemuth R, Seidel C. J. Am. Chem. Soc. 127 (2005) 8775
[6] Novo M, Felekyan S, Seidel C, Al-Soufi W. J Phys Chem B 111 (2007) 3614
[7] Al-Soufi W, Reija B, Felekyan S, Seidel C, Novo M. ChemPhysChem 9 (2008) 1819
50
Fotoquímica de agregados de plata en cucurbit[n]uriles
M. De Miguel1, M. Álvaro1, H. García 2
1
Departamento de Química, Universidad Politécnica de Valencia
2
Instituto de Tecnología Quıímica CSIC-UPV
Los cucurbit[n]uriles son una familia de compuestos orgánicos cuya estructura está formada
por la unión de unidades de glicoluril formando un ciclo dependiendo del número de unidades varía
el tamaño del portal y de la cavidad interior de estas cápsulas. La figura 1 muestra la estructura de
estos compuestos.
CB[5]
CB[6]
CB[7]
CB[8]
Figura 1. Estructura de los diferentes cucurbituriles.
Debido a la forma de los mismos es posible incorporar en el espacio interior moléculas y
agregados huéspedes que permanezcan incluidas en su interior. Particularmente fuertes son los
complejos huésped hospedador que se forman cuando iones positivos se incluyen en el interior de la
cavidad. El motivo de estas altas constantes de formación reside en la interacción electrostática que
se establecen entre los grupos carbonilo de densidad electrónica negativa y la especie positiva
ocluida en su interior.
En trabajos anteriores hemos demostrado que es posible incluir en cucurbit[7]uril agregados
subnanométricos de oro. Continuando en esta línea de trabajo, en la presentación mostraremos la
preparación de agregados manométricos plata en el interior de cucurbit[7]uril y las propiedades
fotofísicas. En contraste a las partículas de oro las de plata son más difíciles de formar con tamaños
inferiores o entorno al manómetro. La reducción de sales de plata fotoquímica en presencia de
cucurbit[7]uril se pueden formar agregados nanometritos de baja densidad. La figura 2 presenta la
imagen de microscopía de transmisión electrónica (TEM) mostrando las partículas de plata en
CB[6], CB[7], CB[8].
Figura 2. Imágenes de microscopía de transmisión electrónica de a) CB[6]; b) CB[7]; c) CB[8].
51
Estas imágenes demuestran la cualidad única de CB[7] para controlar el tamaño de
nanoparticulas de plata. Por otra parte, se ha observado que cuando se generan estas nanoparticulas
de plata dentro de cucurbit[n]uriles se forman agregados altamente fluorescentes cuando son
excitados a longitud de 450nm. La figura 3 se muestra el espectro de fluorescencia para una muestra
de plata en el interior de cucurbit[7]uril.
1,0
Counts (a. u.)
0,8
0,6
0,4
0,2
0,0
300
350
400
450
500
550
600
650
700
750
800
wavelength (nm)
Figura 2. Espectro de fluorescencia excitación (roja), emisión (negra) normalizado de la muestra de plata en el interior
de cucurbit[7]uril.
Considerando los procedentes descritos en la literatura, parece ser que agregados de un
número de plata menor de 10 átomos serían los responsables de esta emisión.
Por otra parte, el estudio mediante la técnica laser flash photolysis permite detectar las
especies transitorias generadas por absorción de luz en esta muestra.
Referencias
[1] A. Corma, H. García, P. Montes-Navajas, A. Primo, J.J. Calvino, S. Trosobares, Chem. Eur. J. 13 (2007) 6359.
[2] ML. Marin, KL. McGilvray, JC. Scaiano. J. Am. Chem. Soc. 49 (2008) 16572
52
Layered double hydroxides as photocatalysts for visible light oxygen generation
from water
Cláudia G. Silva, Younès Bouizi, V. Fornés, Hermenegildo García
Instituto de Tecnología Química, UPV-CSIC, Universidad Politécnica de Valencia
Avda. De los Naranjos s/n 46022 Valencia, Spain
Visible light photocatalytic water splitting is a topic of much interest since development of efficient
hydrogen generation with solar light can be considered a renewable energy resource [1]. One
general strategy to develop visible light photocatalysts for water splitting that has been widely
applied for titanium based semiconductors consists in metal doping in order to introduce energy
levels in the bandgap. Contradictory results on the photocatalytic activity of metal-doped
semiconductors have indicate that for similar doping levels different activities can be obtained
depending on the experimental protocol used for the preparation of the photocatalyst. Addressing
the issue of reliable preparation of doped semiconductors, in the present manuscript we report the
visible light photocatalytic activity of layered double hydroxides (LDHs) commonly known as
hydrotalcites-like compounds (Figure 1).
b
a
MII
MII
MIII
A-
MIII
A-
MII
Figure 1. a) LDH structure with stacking of brucite-like layers, MII and MIII represent the divalent and trivalent element
and A- the anion in the intergallery space compensating the charge induce by the MIII; b) SEM image of (Zn/Cr)LDH.
In the present work, we have developed this novel concept of doped semiconductor based on LDHs
by preparing a series of hydrotalcite zinc oxides and studying their activity for visible light
photocatalytic oxygen generation. The overall water splitting is constituted by two independent
semi-reactions, one of which being the formation of H2 is significantly more feasible and occurring
generally with high efficiencies compared to the O2 evolution [2]. For this reason and in order to
test the use of LDHs as visible light photocatalysts, we have selected O2 evolution as a challenging
process to determine the relative efficiency of our materials.
Two methods were used for the material preparation, the co-precipitation of metal salt from
homogeneous solution with NaOH solution for the incorporation trivalent element (Cr3+, Al3+) and
with an urea solution for the incorporation of tetravalent elements (Ti4+, Ce4+). Materials were
labled as (Zn/M)LDH, with M being Cr, Ti or Ce. Photocatalytic oxygen generation experiments
were carried in the presence of LDH powders (45 mg) dispersed in a 0.01M AgNO3 solution in a
pyrex reactor. The suspensions were irradiated for three hours using a 200W xenon doped mercury
lamp (Hamamatsu Lightningcure LC8). A cutoff filter was employed for visible light irradiation
53
(λ>400 nm). The formation of oxygen was confirmed by injecting a sample of the reactor
headspace gas in a gas chromatograph equipped with a thermal conductivity detector. Photon flux
was determined at 410 and 570 nm using a monochromator (half with 12 nm) by potassium
ferrioxalate actinometry.
Figure 2a shows the diffuse reflectance UV-Vis spectra of the three types of LDHs used in this
study. As it can be seen there, (Zn/Ce)LDH shows a peak at about 280 nm with a tail expanding
into the visible region. (Zn/Ti)LDH has the most intense band occurring at 304 nm. In sharp
contrast, (Zn/Cr)LDH exhibits two maxima in the visible region at 410 and 570 nm, respectively.
The materials were tested for the photocatalytic oxygen generation. Results show that the zinc LDH
containing chromium was the most active material (Figure 2b). These results can be easily
interpreted based on the optical spectra of the three types of LDHs. Actually, (Zn/Cr)LDH is the
material with stronger visible absorption, where irradiation is carried out. In contrast, (Zn/Ti)LDH
is the material with lesser visible absorption and accordingly is the solid showing the lowest
photocatalytic activity for O2 generation with white visible light.
a
b
Figure 2. a) Diffuse reflectance UV-Vis spectra of LHs; b) Temporal profile of the volume of oxygen evolved during
the irradiation of aqueous suspensions of (Zn/Cr)LDH (--), (Zn/Ce)LDH (--) and (Zn/Ti)LDH (--).
Quantum yields of oxygen generation is the most appropriate parameter to establish the
photocatalytic efficiency, considerably more valid than just the volume of oxygen evolved for a
certain period of time under certain conditions. Using iron oxalate as chemical actinometer we have
determined that the quantum yield for O2 generation was of 12.2% and 60.9% at wavelengths of
570 and 410 nm, respectively. The high quantum yields, particularly at 410 nm, for O2 generation
are quite remarkable and ranges (Zn/Cr)LDH at the top of the list of the most efficient
photocatalysts for visible light water splitting [3].
Acknowledgements: Financial support by the Spanish Ministry of Science and Innovation (CTQ 2006-6758) is
gratefully acknowledged. C.G. Silva thanks Fundação para a Ciência e a Tecnologia (Portugal) for the post-doctoral
fellowship (SFRH/BPD/48777/2008).
References
[1] M. Matsuoka, M. Kitano, M. Takeuchi, K. Tsujinaru, M. Anpo, J.M. Thomas, Cat. Today. 122 (2007) 51.
[2] M.W. Kanan, Y. Surendranath, D.G. Nocera, Chem. Soc. Rev., 38 (2009) 109.
[3] H.G. Kim, D.W. Hwang, J.S. Lee, J.Am. Chem Soc.,126 (2004) 8912.
54
Estudio fluorescente de la complejación del dapoxyl por ciclodextrinas:
efecto del tamaño de la cavidad en el tipo y fortaleza de los complejos
D. Granadero, J. Bordello, M. Novo, W. Al-Soufi
1
Departmento de Química Física, Universidad de Santiago de Compostela, 27002 Lugo
Las ciclodextrinas (CDs) son oligómeros cíclicos naturales que presentan una cavidad hidrofóbica
que les permite formar complejos de inclusión en agua con una gran variedad de moléculas
orgánicas. Estos complejos son generalmente estabilizados por fuerzas de van der Waals e
interacciones hidrofóbicas, aunque también pueden jugar un papel importante ciertas interacciones
específicas hospedador-huésped [1]. Asimismo, se ha observado que ciertos requerimientos
geométricos y de orientación del huésped y del hospedador controlan el proceso de asociación,
mientras que la velocidad de disociación viene determinada por la fuerza de las interacciones [2].
Por lo tanto, un cambio en las dimensiones de la cavidad o en la rigidez del hospedador tiene
efectos drásticos en las constantes de velocidad de asociación y disociación y, en consecuencia, en
la estabilidad de los complejos [3]. Por otra parte, para un determinado huésped, la estequiometría y
geometría de los complejos supramoleculares formados depende en gran medida de las dimensiones
de la cavidad del hospedador [4].
En este trabajo estudiamos el efecto del tamaño de la cavidad en la estabilidad y la estructura de los
complejos formados entre la sonda fluorescente dapoxyl sulfonato sódico y CDs de creciente
tamaño de cavidad (α-CD, β−CD y γ-CD). La estructura de esta molécula sonda con dos grupos
aromáticos susceptibles de alojarse en la cavidad de la CD junto con su alta sensibilidad al entorno
la convierten en una molécula modelo muy útil para estudiar los efectos en la complejación debidos
al cambio en las dimensiones de la cavidad del hospedador.
O
N
S
1,37 nm
0,57 nm
1,53 nm
0,78 nm
1,69 nm
0,95 nm
α-CD
β-CD
γ-CD
ONa
O
O
N
Dapoxyl sulfonato sódico
Se llevaron a cabo titraciones para el dapoxyl con las tres CDs empleando técnicas de fluorescencia
en estado estacionario y de resolución temporal. Mediante análisis de los datos experimentales se
dedujo la estequiometría de los complejos formados con cada CD y se obtuvieron las
correspondientes constantes de estabilidad y sus propiedades fluorescentes. La interacción más
fuerte fue observada para el dapoxyl con β-CD, donde se forman complejos de asociación 1:1 y 1:2.
Sin embargo, la complejación del dapoxyl con γ-CD provoca el mayor cambio en las propiedades
de fluorescencia del dapoxyl, con un acusado desplazamiento hacia el azul del espectro de emisión
y un aumento de más de diez veces en el rendimiento cuántico de fluorescencia. Estos resultados se
interpretan en función del grupo del dapoxyl complejado según el tamaño de la cavidad de la CD.
Referencias
[1] B. Reija, W. Al-Soufi, M. Novo, J. Vázquez Tato J. Phys. Chem. 109 (2005) 1364.
[2] W. Al-Soufi, B. Reija, M. Novo, S. Felekyan, R. Kühnemuth, C.A.M. Seidel J. Am. Chem. Soc. 127 (2005) 8775.
[3] W. Al-Soufi, B. Reija, S. Felekyan, C.A.M. Seidel, M. Novo ChemPhysChem 9 (2008) 1819.
[4] J. Bordello, B. Reija, W. Al-Soufi, M. Novo ChemPhysChem 10 (2009) 931.
55
Transient absorption spectroscopy of drugs derivatives within protein
microenvironment
M. Consuelo Jiménez1, C. J. Bueno1, I. Vayá1,2, M. A. Miranda1
1
2
Departamento de Química/Instituto de Tecnología Química UPV-CSIC, Camino de Vera s/n, 46071 Valencia, Spain
Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPA - CNRS URA 2453, CEA/Saclay, 91191 Gif-sur-Yvette, France
Laser flash photolysis (LFP) can be a useful tool to obtain relevant information on the interactions
between drugs (or derivatives) and proteins. In this context, we present here a new methodology,
which makes use of the different triplet lifetimes of ligands within protein microenvironments and
allows to deal with different issues such as i) the determination of enantiomeric compositions, ii)
the in situ monitoring of glucuronidase activity of human serum albumin, iii) the distribution of a
ligand between two different proteins present simultaneously. For these studies, we have employed
as probe flurbiprofen (FBP), a non steroidal anti inflammatory drug of the family of 2-arylpropionic
acids, its methyl ester (FBPMe, a FBP prodrug), and its glucuronide (FBPGluc, a phase II
metabolite).
Some examples of these studies follow:
i) For the determination of enantiomeric composition of mixtures of (S)- and (R)-FBP, the
decay traces obtained in the presence of HSA (Figure 1A) were fitted using equation (I), which
allows to determine the preexponential factors Ai and thus the percentage of enantiomers.
Correlation between the LFP-determined values and the real ones was satisfactory (Figure 1B)
ii) A similar methodology was employed to evaluate the enzyme-like activity of HSA. Thus,
in a previous experiment, the binding of (S)- and (R)- FBPGluc to HSA was determined (Figure
2A). It was found that FBPGluc only binds to site II in HSA (equation II). For the glucuronidase
activity of HSA, FBPGluc was incubated at 37 ºC in the presence of HSA at different times and the
solutions submitted to LFP. To fit the decays (Figure 2B), equation III was employed. The amount
of FBP formed was calculated from the preexponential factors Ai of equation III.
iii) Finally, the distribution of (S)- or (R)- FBP between HSA and α-acid glycoprotein
(AAG) present simultaneously was established from the triplet decays of FBP/HSA/AAG mixtures.
First, the percentage of FBP free and bound to HSA and AAG separately was determined, fitting the
corresponding decays and using equations IV and V. Then, a similar treatment of the decay in
FBP/HSA/AAG mixtures and equation VI led to the occupation degree of each protein by the drug
(Figure 3).
S
S
R
R
∆OD=∆OD 0 +A SI e(-t/τ I ) +A SIIe (-t/τ II ) +A RI e(-t/τ I ) +A RII e(-t/τ II ) (I)
FBPGluc
∆OD=∆OD0 +A FBPGluc
e(-t/τF
F
FBP
∆OD=∆OD0 +A IFBPe(-t/τI
)
)
FBPGluc
+A FBPGluc
e(-t/τB (II))
B
FBP
FBPGluc
+A IIFBPe(-t/τII ) + A FFBPGluce(-t/τ F
S
S
∆OD=∆OD 0 +A (S)-FBP
e(-t/τI ) +A (S)-FBP
e(-t/τ II )
I
II
FBP
FBPGluc
+A FBPGluc
e(-t/τ B
B
FBP
)
(III)
FBP
(V)
S
S
∆OD=∆OD0 +A (S)-FBP
e(-t/τF ) +A (S)-FBP
e(-t/τB ) +A (S)-FBP
e(-t/τI ) +A (S)-FBP
e(-t/τII )
F
B
I
II
56
)
(IV)
∆OD=∆OD0 +A (S)-FBP
e(-t/τF ) +A (S)-FBP
e(-t/τB
F
B
FBP
)
(VI)
1.00
LFP determined % (S)
∆OD/ a.u.
A
0.75
0.50
0.25
100
B
80
60
40
20
0.00
0
0
50
100
150
0
200 250
t/µs
20
40
60
80
100
Real %(S)
1.0
A
0.8
AFFBPGluc= 0.01361 ± 0.00040
ABFBPGluc= 0.00815 ± 0.00011
R= 0.985
A
B
100%
0.6
50%
0.4
0.2
Normalized ∆OD
Normalized ∆OD
Figure 1. A. Laser flash photolysis (λexc = 266 nm) of several (S)-FBPMe/(R)-FBPMe/HSA mixtures. Decays (λ =
360 nm) for mixtures 1/0/1 (black), 0.7/0.3/1 (red), 0.3/0.7/1 (blue) and 0/1/1 (green). B. LFP-determined against
known real values, together with the linear fit of the experimental points.
1.0
B
0.8
0.6
AFFBPGluc= 0.00036 ± 0.00047
ABFBPGluc= 0.00034 ± 0.00045
AIFBP= 0.00349 ± 0.00020
AIIFBP= 0.00581 ± 0.00046
R= 0.979
0.4
0.2
0%
0.0
0.0
0
25
50
75
100
t ( µ s)
125
0
25
50
75
100
125
t ( µ s)
Normalized ∆OD
Figure 2. Left (A): Laser flash photolysis (λexc = 266 nm) of (S)-FBPGluc/HSA at 1:3.33 molar ratio (decay at λ =
360 nm) together with the corresponding fit (red line) and the parameters obtained from the fitting and eq. II. The bars
indicate the percentage of free and bound FBPGluc. Right (B): Laser flash photolysis (λexc = 266 nm) of (S)FBPGluc/HSA at 1:3.33 molar ratio (decays at λ = 360 nm) after 6.5 h at 37 ºC, together with the corresponding fit and
the parameters corresponding to the fitting and eq. III. The bars indicate the percentage of free FBPGluc (orange), HSAbound FBPGluc (blue), FBP in site I (yellow) and FBP in site II (green).
1,0
(S)-FBP/HSA
(S)-FBP/HSA/AAG
0,8
0,6
(S)-FBP/AAG
0,4
0,2
33% Free FBP
15% FBP in AAG
21% FBP in site I of HSA
31% FBP in site II of HSA
0,0
0
25
50
75
100
125 150
t (µs)
Figure 3. Laser flash photolysis (λexc = 266 nm) of (S)-FBP/HSA (green), (S)-FBP/AAG (black) and (S)-
FBP/HSA/AAG (red) (decays at λ = 360 nm). The fitting and the parameters obtained using eq. VI allowed to obtain
the distribution of FBP between the two proteins and free in solution.
References
[1] T. Peters, All about albumins Biochemistry Genetics and Medical Applications, Academic Press, San Diego, 1995.
[2] I. Vayá, C. J. Bueno, M. C, Jiménez, M. A. Miranda, Chem. Eur. J., 2008, 14, 11248.
[3] C. J. Bueno, M. C. Jiménez, M. A. Miranda, J. Phys. Chem. B, 2009, 113, 6861.
57
Femtosecond Studies of a Confined Porphyrin Derivative by Human Serum
Albumin Protein
A. Synak, M. Gil, J.A. Organero and A. Douhal*
Department of Physical Chemistry, Facultad del Medio Ambiente, University of Castilla-La Mancha,
Toledo, Spain 45071
[email protected], Corresponding author: * [email protected]
Porphyrin derivatives are widely studied because of they can be used in photodynamic
therapy and photonics [1,2]. Several groups have studied their ultrafast dynamics in solution to
distinguish between the monomer and aggregates dynamics [3-5]. In this contribution, we will show
the results of femtosecond fluorescence dynamics studies of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin (p-THPP) in tetrahydrofuran (THF) and encapsulated within the Human Serum Albumin
(HSA) protein in neutral water solution. In both solutions, after excitation at 416 nm we observed
short times from 50 fs to 5 ps in addition to nanosecond fluorescence lifetimes (figure 1). While in
THF, we observed fluorescence rise time of about 100 fs at the red part of the emission spectrum, in
the protein solution we could not observe any rise within the time resolution of the apparatus (50
fs). We will discus the results in terms of monomer and aggregates dynamics, and confinement
effect of the biological host in the guest photodynamics. We believe that the observed results are
important to understand the photodynamics of porphyrins when used in photodynamic therapy or in
photonics science.
OH
A
B
HO
N
N
H
HN
OH
p-THPP
OH
normalized intensity
N
700 nm
680 nm
660 nm
640 nm
IRF
2
4
6
8
10
12
14
16
Time/ps
HSA
Figure 1: A. Structures of p-THPP and HSA protein. B. Magic-angle fs-emission transients of p-THPP in
HSA/aqueous buffer solution (pH = 7) at different wavelengths of observation after excitation at 416 nm.
58
References
[1] R. Bonnett, Chem. Soc. Rev. 24 (1995) 19-33.
[2] D.Kim, A. Osuka, J. Phys. Chem. A 107 (2003) 8791-8816.
[3] J. S. Baskin, H.Z. Yu, A.H. Zewail, J. Phys. Chem. A 106 (2002) 9837-9844.
[4] A. Miura Y. Shibata, H. Chosrowjan, N. Mataga, N. Tamai, J. Photochem. Photobiol. A 178 (2006) 192-200.
[5] H. Kano, T. Kobayashi, J. Chem. Phys. 116 (2002) 184-195.
Acknowledgements: This work was supported by the JCCM and MICINN through projects PCI08-5868 and
MAT2008-01609. A.S. thanks the Marie Curie Actions for the Intra European Fellowship through project PIEF-GA2008-219856 (FENASY).
59
Aplicaciones derivadas de la fotoquímica de O-aciloximas
Alegría Caballero, Rafael Alonso, Miguel A. Rodríguez y Pedro J. Campos.
Departamento de Química
Universidad de La Rioja
Grupo de Síntesis Química de La Rioja U.A.-CSIC
Madre de Dios, 51; 26004 Logroño, La Rioja
Desde principios de los años noventa, nuestro grupo de investigación se ha interesado en el
comportamiento fotoquímico de iminas, compuestos nitrogenados y sistemas relacionados. En el
transcurso de nuestra investigación, nos pareció interesante el estudio de la irradiación de Oaciloximas o ésteres de oxima, ya que sus aplicaciones sintéticas habían sido muy poco
desarrolladas. La irradiación de este tipo de sistemas genera radicales iminilo, especies muy
reactivas que son capaces de adicionarse a dobles y triples enlaces1.
Esta metodología puede resultar interesante para sintetizar distintos tipos de heterociclos
nitrogenados de gran importancia e interés desde el punto de vista biológico como pueden ser los
alcaloides.
Actualmente y mediante esta estrategia, hemos sintetizado alcaloides de núcleo fenantridina como
son la trisphaeridina o la vasconina (figura 1). La investigación sigue su curso y pretendemos, en un
futuro, sintetizar compuestos de interés derivados de otro tipo de heterociclos nitrogenados como
quinazolinas, quinolinas e isoquinolinas.
MeO
MeO
OH
N
OAc
hν
ν
MeO
MeO
OH
N
PBr3
MeO
MeO
N
BrVASCONINA
[1] a) Alonso, R.; Campos, P. J.; García, B.; Rodríguez, M. A.Org. Lett. 2006, 8, 3521.b) Alonso, R.; Campos, P. J.;
Rodríguez, M. A.; Sampedro, D. J. Org. Chem. 2008, 73, 2234.
60
mPTA-based photoactive ruthenium derivatives
(mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane)
M. Chaara,1 R. Girotti,1 S. Mañas,1 V. Passarelli,1 R. Perutz,2 A. Romerosa,1 M. Serrano1
1
Area de Química Inorgánica, Facultad de Ciencias, Universidad de Almería, Almería, Spain; Organometallic and
Photochemistry Laboratory for Sustainable Chemistry, CIESOL, Almería, Spain.
2
Department of Chemistry, University of York, York YO10 5DD, UK.
The exploitation of solar energy as a viable alternative to the fossil one is being addressed as one of
the most promising strategy in order to design ecobenign synthetic procedures. Nevertheless the
only use of solar energy source is not enough to accomplish totally eco-compatible processes, since
also selectivity, yield, and reaction conditions such as the used solvent are crucial factors to be
taken into account. Water is cheap and no contaminant and therefore its use should be strongly
desirable in order to carry out syntheses potentially respectful with the environment. Thus,
emerging research lines in coordination chemistry are targeted to obtain photoactive water-soluble
metallic compounds able to promote catalytic transformations.
Recently we have presented the catalytic properties of water-soluble ruthenium complexes
containing
1,3,5-triaza-7-phosphaadamantane[1]
(PTA)
and
[2]
3-(diphenylphosphino)benzenesulfonate, and additionally the photochemical transformation of
trans-[RuCl2(PTA)4] into cis-[RuCl2(PTA)4] by visible light.[1] In order to obtain new water soluble
ruthenium complexes potentially useful as catalysts, we decided to undertake the synthesis of novel
derivatives containing the N-methyl-1,3,5-triaza-7-phosphaadamantane ligand (mPTA) (Figure 1A)
which are expected to be more soluble in water than the PTA ruthenium complexes. The reaction of
[RuCl2(PPh3)3] with mPTA led to [RuCl2(mPTA)4]4+ (1) (Figure 1B) which dissociates one mPTA
molecule in aqueous medium under visible light affording the cation trans-mer[RuCl2(H2O)(mPTA)3]3+ (2) (Figure 1C) which on its turn photo-isomerises to the fac complex 3
(Figure 1A). Finally, complex 1 reacts photo-chemically with terminal alkynes affording new
ruthenium complexes.
[RuCl2(PPh3)3]
P=
P
N
N
N
+3 P
+ H 2O
-3 PPh3
3+
P
Cl
P
Ru
Cl
OH2
P
( 2)
P
P
Cl
Ru
P
Cl
P
+ P exc.
-3 PPh3
4+
( 1)
hν
hν
H2 O
-P
H 2O
P
P
Cl
Ru
P
Cl
OH2
3+
( 3)
(A)
(B)
(C)
Figure 1. Reactions' scheme (A); molecular structure of [RuCl2(mPTA)4]4+ (1) (B) and [RuCl2(H2O)(mPTA)3]3+ (2) (C).
References
[1] R. Girotti, A. Romerosa, S. Mañas, M. Serrano-Ruiz, R. N. Perutz, Inorg. Chem., 48 (2009) 3692.
[2] T. Campos-Malpartida, M. Fekete, F. Joó, Á. Kathó, A. Romerosa, M. Saoud, W. Wojtków, J. Organomet. Chem.,
693 (2008) 468.
Acknowledgements
Funding is provided by Junta de Andalucía through PAI (research teams FQM-317) and Excellence Projects FQM03092, the MCYT (Spain) projects CTQ2006-06552/BQU. M. Chaara thanks to MAE for a grant.
61
Controlling laser emission by size of particles in gain media
V. Martín1, R. Sastre2, A. Costela1, I. García-Moreno1
1
2
Departamento de Química Láser, Instituto de Química-Física “Rocasolano”, CSIC
Departamento de Fotoquímica de Polímeros, Instituto de Ciencia y Tecnología de Polímeros, CSIC
Optical properties of new materials based on nanometer silica particles have been of increasing
interest for both fundamental and practical reasons, largely because of their novel applications in
photonic and electronic devices.[1] The presence of silicon, in any form, enhances significantly the
thermal, mechanical and physical properties of the final materials, opening the challenge to
synthesize new luminescent hybrid matrices.[2]
A laser is usually built from two basic elements: a material that provides optical gain through
stimulated emission and an optical cavity that partially traps the light. When the total gain in the
cavity is larger than the losses, the system reaches a threshold and lases. It is the cavity that
determines the modes of a laser; that is, it determines the directionality of the output and its
frequency. Random lasers work on the same principles, but the modes are determined by multiple
scattering and not by a laser cavity.
The influence of the size of the inorganic particles on the laser action of dye-doped hybrid solutions
can be well established by the addition of two types of silica (Polysilsesquioxanes® and Aerosils®)
to the media.
Polysilsesquioxanes (POSS) have a compact hybrid structure with an inorganic core made up of
silicon and oxygen (SiO1.5)n externally surrounded by nonreactive or reactive polymerizable organic
ligands. The type and number of substituents control the interactions with the media defining the
compatibility, and thus the final properties of the systems where POSS is incorporated. POSS
nanoparticles can be dispersed at molecular level (1-3 nm) and, because of their synthetically wellcontrolled functionalization, can be incorporated into polymers by different polymerization
techniques with minimal processing disruption. Their excellent dispersion at molecular scale
prevents phase separation assuring the macroscopical homogeneity of the materials.[3]
On the other hand, Aerosil is fully amorphous fumed silica with a large specific surface area (S =
50-600 m2/g) reciprocally dependent on the average size (d = 5-50 nm) of primary particles. These
primary particles form stable aggregates of 100-500 nm through hydrogen and electrostatic bonding
and/or via –Si–O–Si– bridges formed due to primary particle sticking and fusing at relatively high
temperatures during synthesis.[4]
We propose and demonstrate, the behaviour of POSS doped systems as random lasing materials, a
possibility never before considered. The dispersion of POSS nanoparticles at molecular level
defines highly homogeneous materials, independently of its concentration (1-50 wt%). When these
materials are doped with lasing dyes, coherent laser emission is allowed but, in addition and in spite
of their nanometer size, the POSS particles sustain an incoherent feedback into the coherent
emission by multiple scattering. Multiple scattering is a well-known phenomenon that occurs in
nearly all optical materials that appear opaque, being considered as detrimental to laser action
because it represents a source of losses. Thus, it is difficult to realize a priori that such a
homogeneous material with nanoparticles whose size is below 10 nanometers could sustain
scattering phenomenon, as well as high efficient laser emission. We found that the nanosized POSS
particulates allow a weak optical scattering that enhanced significantly the laser action by
62
elongating the light path inside the gain media, providing an extra feedback, a phenomenum central
to the process called “incoherent random laser” or “Lasing with Intensity Feedback”.[5]
Similar behavior has been observed in hybrid systems based on Aerosils added in a very low
concentration (<0.25 wt%). Higher concentrations of the inorganic component increased the
scattering to a level detrimental to the coherent laser emission.
5.7
4.8
3.4
2.3
1.2
540 550 560 570 580
0.9
Wavelength (nm)
Figure 1. Front-face emission spectra as a function of the pumping energy at 532 nm from a high homogeneous
cop(MMA-8MMAPOSS 87:13) matrices doped with PM567 dye.
In conclusion, the scattering action can be modulated by controlling the particles size in the media
and/or their concentration. In this way, by careful control of particle size and concentration it is
possible to develop transparent materials that can support highly efficient and photostable laser
action or opaque materials working as purely random lasers.
References
[1]
[2]
[3]
[4]
K. Pielichowski, J. Njuguna, B. Janowski, J. Pielichowski, Adv. Poly. Sci. 201 (2006) 225.
E. Markovic, S. Clarke, J. Matisons, G. P. Simon, Macromolecules 41 (2008) 1685.
S. Bizet, J. Galy, J. F. Gerard, Polymer 47 (2006) 8219.
H. Barthel, L. Rosch, J. Weis, Organosilicon Chemistry II, in From Molecules to Materials, edited by N. Auner, J.
Weis, VCH, Weinheim 1996.
[5] S. Takeda, M. Obara, Appl. Phys. B 94 (2009) 443.
63
Síntesis y estudio fotofísico de nuevos cromóforos con estructura de
aza-BODIPY para aplicaciones en medios fisiológicos
R. Suau1, E. Pérez-Inestrosa1, D. Collado1
1
Departamento de Química Orgánica, Universidad de Málaga
Los difluoroboradiaza-s-indacenos, más conocidos como BODIPY, presentan emisión de
fluorescencia con alto rendimiento cuántico, así como otras interesantes propiedades (estabilidad,
baja influencia del disolvente y pH) por lo que han sido usados extensamente como sensores en
sistemas biológicos.1
La modificación del cromóforo BODIPY permite obtener sistemas con emisiones por encima 600
nm pero esta estrategia presenta limitaciones. La búsqueda de nuevos cromóforos capaces de
absorber y emitir en la zona NIR, ha permitido la síntesis de estructuras derivadas de BODIPY con
la sustitución del átomo de carbono por nitrógeno en la posición C8. Estos cromóforos son
comúnmente llamados aza-BODIPY. Esta modificación permite una marcado desplazamiento al
rojo con emisiones en la región 695-705 nm manteniendo una relativa alta emisión de fluorescencia.
N
N
B
N
F F
BODIPY
N
B
N
F F
aza-BODIPY
Se han establecido varias rutas sintéticas,2,3 en general se requiere de la obtención del pirrol
sustituido seguida de la formación del nitroso derivados que condensan in situ para formar los
precursores azadipirrometenos. Tras posterior tratamiento con BF3·OEt2 generan los
correspondientes aza-BODIPY. En esta comunicación se presenta la síntesis de diferentes tipos de
aza-BODIPY así como el estudio fotofísico de los nuevos cromóforos en distintos disolventes y
medio fisiológico. La estructura química estos sistemas que permite la introducción de diferentes
tipos de sustituyentes con un núcleo fluorescente los hace interesantes en su eventual utilización en
sistemas biológicos. Una primera aproximación nos permite obtener receptores multitópicos para
procesos de reconocimiento molecular.
Referencias
[1] A. Loudet, K. Burgess, Chem Rev, 107 (2007), 4891.
[2] A. Loudet, R. Bandichhor, L. Wu, K. Burgess, Tetrahedron, 64 (2008), 3642
[3] W. Zhao, E. M. Carreira, Chem, Eur. J., 12 (2006), 7254
64
Determinants of singlet oxygen formation and decay in biological systems
S. Nonell, X. Ragàs, M. Agut
Grup d’Enginyeria Molecular, Institut Químic de Sarrià, Universitat Ramon Llull, Vía Augusta 390, 08017-Barcelona,
España
[email protected]
Oxidative damage to biological structures, either accidental or intended, is a major cause of cell
death. In biological systems, pathways signalling necrotic or apoptotic responses can be induced by
the combined use of a photoactivatable drug and UV or visible light. The process involves the
generation of reactive oxygen species, particularly singlet molecular oxygen O2(a1∆g), capable to
inflict damage to susceptible cell components. This concept underpins the development of
photodynamic therapies for the treatment of solid tumours and localised microbial infections [1]. A
recent elaboration is the development of genetically-targeted chromophore-assisted light
inactivation using Green Fluorescence Protein (GFP) mutants for the study of protein structure and
function [2].
The prospect of using genetically-encoded photosensitizers for mechanistic and eventually
therapeutic purposes has leaded us to study the ability of GFP mutants to photosensitize the
production of singlet oxygen. The results of these studies reveal the role of the protein’s beta can in
the photosensitization process. Specifically, tightly-packed proteins are very efficient barriers
precluding oxygen from quenching the protein’s internal chromophore. This results in long triplet
lifetimes and low singlet oxygen production quantum yields [3]. On the contrary, those proteins
where the beta can is more loosely packed allow for more efficient oxygen diffusion into the protein
- and more efficient singlet oxygen production.
The complex interactions of oxygen with proteins and other biopolymers translate in sensitive
differences in the kinetics of singlet oxygen formation, diffusion, and decay in cells depending on
the compartment where it is produced. Contrary to common belief, O2(a1∆g) is able to cross cell
membranes with relative ease and diffuse over distances much longer than generally accepted [4].
Using a number of photosensitisers with different structure and electrical charge we have also
assessed the fate of singlet oxygen in Escherichia coli bacteria depending on the site of primary
localisation of the photosensitiser. The results of these studies provide insights for the design of
efficient antimicrobial photodynamic therapy agents.
References
[1] D. E. J. G. Dolmans, D. Fukumura, R. K. Jain, Nat. Rev. Cancer 3 (2003), 380-387.
[2] M. E. Bulina, D. M. Chudakov, O. V. Britanova, Y. G. Yanushevich, D. B. Staroverov, T. V. Chepurnykh, E. M.
Merzlyak, M. A. Shkrob, S. Lukyanov, and K. A. Lukyanov, Nat. Biotechnol. 24 (2006), 95-99.
[3] A. Jiménez-Banzo, S. Nonell, J. Hofkens, C. Flors, Biophys. J. 94 (2008), 168-172.
[4] A. Jiménez-Banzo, M. L. Sagristà, M. Mora, S. Nonell, Free Rad. Biol. Med. 44 (2008), 1926-1934.
65
Interactions of a cyanine homodimeric dye with single-stranded and doublestranded DNA
Maria J. Ruedas-Rama, Angel Orte, Jose M. Paredes, Luis Crovetto, Eva M. Talavera and Jose M. Alvarez-Pez
Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Granada, Spain 18071
Intercalating dyes are in general aromatic cations with planar structure that insert between stacked
base pairs on the DNA duplex. This intercalation provides an environmentally dependent
fluorescent enhancement for the dye molecules and creates a large increase of the fluorescent signal
relative to the free dye in solution. Cyanine homodimeric dyes have been widely used as
intercalating staining dyes of biological samples, such as duplex DNA [1]. BOBO-3 is one of these
dyes showing excellent characteristic of non-covalent binding to DNA and a high affinity constant,
and a large increase in the fluorescence quantum yield upon intercalation.
In this work we focused on the characterization of the interaction of BOBO-3 with single-stranded
and double-stranded DNA of different nature: homo-oligonucleotides A-T and C-G of several
lengths; homo-biopolymers such as poly-A / poly-T and poly-C / poly-I; and specific DNA
fragments. In order to investigate potential differences and preference of intercalation into GC-rich
or AT-rich regions we employed several spectroscopic methods such as spectrophotometry, steady
state and time resolved fluorescence techniques, and fluorescence correlation spectroscopy [2].
In the course of our investigation we detected additional direct interactions between BOBO-3 and
DNA bases, not involving an intercalation mechanism. We then studied these non-intercalating
direct using homo-oligonucleotides of different sizes. Interestingly, we observed the formation of a
charge transfer complex between BOBO-3 and long chain homo-nucleotides of cytosine residues
and polyribocytidylic acid (poly-C). This non-fluorescent complex gives rise to a new absorption
band at 456 nm (see Figure). Moreover, the formation of such complex in single strands avoided
complete hybridization with the complementary strand, which can be a drawback in the
development of hybridization probes for specific DNA sequences with high content in C-G pair.
Finally, the stoichiometry and the mechanism of the complex formation are discussed.
Absorbance (a. u.)
0.05
0.04
0.03
0.02
0.01
0.00
400
450
500
550
600
650
Wavelength (nm)
Figure. Absorption spectrum of 5 10-7M BOBO-3 in solution (black) and BOBO-3 after addition
of Poly-C: 5 10-7M (red); 10-6 M (green); 1.5 10-6 M (blue); and 2 10-6 M (cyan).
References
[1] T. L. Netzel, K. Nafisi, M. Zhao, J. R. Lenhard, I. Johnson, J. Phys. Chem. 99 (1995) 17936.
[2] E. M. Talavera, P. Guerrero, F. Ocana, J. M. Alvarez-Pez, Appl. Spectr. 56 (2002) 362.
66
Energy and Charge Transfer Processes in BDP Dyes to Develop Novel
Fluorescence Probes and Sensors
J. Bañuelos, F. López Arbeloa and I. López Arbeloa
Departamento de Química Física, Universidad del País Vasco (UPV/EHU), Apartado 644, 48080-Bilbao
Boron-dipyrromethene complexes (BDP) are a family of laser dyes, which have been successfully
applied as active media of tunable dye lasers in the green-yellow region, yielding high lasing
efficiencies and photostabilities, included in the solid state [1]. BDP dyes have a good chemical
stability, and present unique photophysical properties, mainly characterized by very high
fluorescence capacities. Besides, their photophysics can be modulated by the substitution pattern of
the chromophore. This is why, in the last years, several reports have claimed the use of BDP dyes in
different photoelectronic devices [2,3], apart from its inherent lasing application. For example, their
emission region has been shifted to the red part of the visible by means of the extension of their πsystem through delocalized substituents. BDP dyes have been also incorporated in antenna systems
to develop photovoltaic devices as energy acceptors or injectors, and have been used as
fluorescence probes or molecular sensor in biological systems to get a deeper knowledge of the
environment surrounding the dye
Trying to span the technological applicability of these dyes, we proceeded to investigate the
photophysics of new BDP derivatives with different functional groups (cyano, amine and
polyphenyl groups, Figure 1). The aim of this work, is to develop fluorescence probes or sensor
based on these dyes in which the photophysical properties of the resulting BDP is sensitive to the
physicochemical characteristics of the environment of the presence of certain molecules in the
surrounding media.
Charge Transfer
(ICT)
N
N
N
N
N
B
B
F
F
PM650
F NH2
F
Amino-BDP
Energy Transfer
(Intra-ET)
F
F
OAc
Photoinduced Electron Transfer
(PET)
B
N
N
OH
X
N
N
B
F
F
PXArAc
(X = 1,2,3)
2
3
N
N
N
B
F
F
P3ArP
N
B
F
F
P2ArOH
Figure 1. Molecular structure of the studied BDP dyes.
67
Indeed, the inclusion of electron donating (amine) or accepting (cyano) groups, not only affects the
emission region, but also induces the appearance of a fluorescence quenching via the formation of
an intramolecular charge transfer state (ICT). The charged state is favoured in polar media. In this
way, these systems can be used as molecular probes to monitor the environmental polarity. Besides,
the inclusion of a phenylphenol group, which can be ionized in basic media, leads to a reversible
fluorescence on/off switch for the acidicty/basicity of the surrounding media, via the
deactivation/activation of a fluorescence quenching by means of a photoinduced electron transfer
process (PET). On the other hand, the introduction of chromophores to the BDP core, leads to
multichromophoric systems (BDP-polyphenyl cassettes), where intramolecular energy transfer
processes (intra-ET) are very important. In these systems, the UV excitation of the polyphenyl
group can lead to the Vis emission of the BODIPY core. In this way, the detection region can be
well-separated from the pumping region, avoiding interferences phenomena in the fluorescent
signal. This is very important in monitoring processes in biological systems, where BDP dyes can
be used a fluorescence probes in labelled biomolecules.
All these results suggest the versatility of BDP dyes, which can be successfully applied in different
technological fields, just modifying the basic molecular structure with adequate functional groups.
References
[1] O. García, R. Sastre, D. Del Agua, A. Costela, I. García-Moreno, F. López Arbeloa, J. Bañuelos, I. López Arbeloa,
J. Phys. Chem. C 111 (2007) 1508.
[2] A. Loudet, K. Burgess, Chem. Rev. 107 (2007) 4891.
[3] G. Ulrich, R. Zyessel, A. Harriman , Angew. Chem. Int. Ed. 47 (2008) 1184.
68
Una Nueva Generación de Cromóforos Ditópicos VSD (Voltage-Sensitive Dyes)
para Aplicaciones Biomédicas
J. M. Montenegro1, J. Casado2, J. T. Lopez Navarrete2, R. Suau1, E. Perez-Inestrosa1
1
Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Málaga
2
Departamento de Química Física, Facultad de Ciencias, Universidad de Málaga
Moléculas que presentan la capacidad de cambiar sus propiedades ópticas en absorbancia,
fluorescencia o birrefringencia cuando se produce un cambio en el potencial de membranas a las
que se encuentran unidas se denominan con el acrónimo VSD (Voltage-Sensitive Dyes).
Normalmente son moléculas orgánicas que pueden residir en la membrana celular y cambian sus
propiedades ópticas en respuesta a cambios en el potencial de membrana. Estas moléculas se están
empleando ampliamente para monitorizar procesos de neuronas individuales y de grupos de
múltiples células en determinadas regiones localizadas del cerebro. En procesos más generales,
estas moléculas se han usado para seguir los cambios de población en el potencial de membrana en
regiones extensas del cerebro y el corazón [1].
Debido a la habilidad de seguir los cambios de potencial en la escala de milisegundos, los
colorantes tipo “estilbeno” son el modelo más ampliamente utilizado como moléculas fluorescentes
VSD. Generalmente, la estructura consiste en un componente rico en electrones tipo amino-fenilo
unido a un heterociclo nitrogenado cuaternizado a través de un doble enlace que conjuga ambas
unidades [2].
En esta comunicación presentamos la síntesis de una nueva serie de moléculas basadas en la
conjugación de un componente bitiofénico, diferentemente sustituido al final del bitiofeno, unido
por un doble enlace al N-óxido de Quinolina. Se discutirán sus propiedades luminiscentes en
función del disolvente y como estas propiedades varían en función de la posibilidad de coordinar el
átomo de oxígeno de la función N-óxido con diferentes especias químicas, de forma reversible
(protón, cationes metálicos) o irreversible (alquilación).
N+
O-
S
S
H, -OCH3, -N(CH3)2
En muchos casos, estos estudios se complementan con el conocimiento sobre la variación de la
concentración del ión calcio y por esta razón se han desarrollado sistemas que puedan responder a
ambos parámetros. Sin embargo, recientemente, se ha demostrado que el ión zinc desempeña un
importante papel regulador en los mecanismos de comunicación neuronal [3] y se carece
actualmente de métodos que permitan abordar estos estudios de forma simultánea. De esta forma,
hemos extendido los estudios a la variación de las propiedades luminiscentes de estos sistemas en
función de la coordinación del átomo de oxígeno de la función N-óxido por el cation zinc.
Previamente nuestro grupo de investigación ha demostrado que los N-óxido de (iso)Quinolinas
pueden coordinarse al cation zinc y que esto implica importantes variaciones en las propiedades
luminiscentes de estos cromóforos [4].
Referencias
[1] W.-L. Zhou, P. Ying, J. P. Wuskell, L. M. Loew, S. D. Antic, J. Neurosci. Methods. 164 (2007) 225.
[2] P. Yan, A. Xie, M. Wei, L. M. Loew, J. Org. Chem. 73 (2008) 6587.
[3] K. Hirzel, U. Müller, A. T. Latal, S. Hülsmann, J. Grudzinska, M. W. Seeliger, H. Betz, B. Laube, Neuron 52 (2006)
679.
[4] J. M. Montenegro, E. Perez-Inestrosa, D. Collado, Y. Vida, R. Suau, Org. Lett. 6 (2004) 2353.
69
New integrated oxygen sensors bases on GaN surfaces covalent functionalization
with luminescence Ru(II) complex.
J. López-Gejo1, A. Arranz2, C. Palacio2, A. Navarro3, E. Muñoz3, G. Orellana1
1
Departmeno de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040,
Madrid, Spain.
2
Departamento de Física Aplicada, Facultad de Ciencias, C-XII, Universidad Autónoma de Madrid,
Cantoblanco, 28049-Madrid, Spain,
3
ISOM and Departamento de Ingeniería Electrónica, ETSI Telecomunicación, Universidad Politécnica de Madrid,
28040 Madrid, Spain
Development of new integrated devices for the detection and/or monitoring of an analyte is a
priority goal of very different areas such as microfluidic, environmental monitoring and
microelectronics where size of the device is a mayor issue. For oxygen sensing, adsorption of
polyazaheterocyclic complexes of Ru(II) into a polymer matrix is the most common and useful way
to build a sensor. In this work, functionalization of Gallium nitride (GaN) surfaces is presented as a
key step on the development of an innovative sensing device. Thus, the substrate (semiconductor)
plays the role of support as well as the excitation source leading to a compact design of an
integrated detector/sensor. GaN is the chosen semiconductor since its band gap, and therefore
emission band, fits very precisely with the MLCT absorption band of the Ru(II) complex.
A functionalization sequence based on oxidation, silanization with 3-aminopropyltriethoxysilane
(APTES) and finally reaction of the corresponding ruthenium complex sulphonyl chloride with the
amine group of the silane, leads to the formation of a sulfonamide and the desired covalent union of
the dye to GaN surfaces. Lifetime luminescence decays were recorded to confirm the presence of
the dye into the surfaces after functionalization process (Figure 1). X-ray photoelectron
spectroscopy (XPS) surfaces analysis and, more precisely the detailed analysis of the S 2p core
level (Figure 2), evidences the covalent union between the dye and the substrate. In addition,
fluorescence microscopy images were obtained with distribution of the luminescence dye along the
surfaces.
A Stern-Volmer plot is presented, showing the oxygen sensing capabilities of the functionalized
surfaces. Such successful functionalization and characterization is the first step on the design and
construction of a miniaturized sensor to be installed in an integrated circuit or a microfluidic
reactor.
100000
GaN-Ru(s2d)
GaN
counts
10000
Exc: 470 nm
1000
100
10
0
2
4
6
8
10
time(µs)
Figure 1. Luminescence decay of pure GaN surfaces
and functionalized GaN with Ru(s2d). 470 nm
excitation
wavelength
and
detection
wavelength above 590 nm.
70
Figure 2. S 2p core level XPS spectra for (a)
adsorbed and (b) covalently bonded Ru
compound on untreated and silanized
GaN substrates, respectively.
New Hybrid Dyes for Biomedical and Photonic Applications.
1
M.E. Pérez-Ojeda1, B.Trastoy2, J.L Chiara2, R. Sastre1.
Fotoquímica de Polímeros, Instituto de Ciencia y Tecnología de Polímeros. CSIC.
2
Química Orgánica Biológica, Instituto de Química Orgánica General. CSIC.
The synthesis of new hybrid organic-inorganic dyes intends to obtain systems exhibiting
a highly efficient, stable, and tunable laser emission improving their thermal properties by
chemical bonding to an inorganic compound [1], in order to strengthen their biomedical and
photonic applications.
We have designed and synthesized new hybrid dyes based on functionalized trigonal silica
as inorganic part and a dipyrromethene·BF2 chromophore, analogue to pyrromethene 567, as
organic component. This chromophore was selected by its interesting laser and photophysical
properties, both in liquid phase and incorporated into solid matrices, which makes the resultant
hybrid systems very appropriate for a wide variety of applications such as optoelectronic systems,
optical filters, and tags in biomedical reactions.
As inorganic component, we have utilized polyhedral cubic silsesquioxanes (POSS, T8).
POSS are nanometric trigonal silica structures functionalized with organic substituents, whose
number and nature control their interactions with the medium, which is fundamental for their
application as fluorescent labelling reagents in studies of interaction with different biological
receptors. In addition, these compounds exhibit a high symmetry and are chemically easy to
functionalize and modify.
The chemical attachment of dye to POSS has been carried out through Cu(I)-catalyzed
azide-alkyne 1,3-dipolar cycloaddition reactions [2] (Figure 1). In a first step, we proceeded to the
synthesis of a hybrid dye by reaction of octafunctionalized POSS with eight dye molecules,
saturating the substitution. The objective was to maintain the laser properties of PM567, while
shifting its emission to the red with respect to that of the non-anchored dye by extension of the
conjugation due to the spatial disposition of the chromophore´s molecules. However, the high
density of dye molecules per volume unit led to a decrease in the fluorescence quantum yield and to
the disappearance of the laser emission, in spite of the absorption molar coefficient being one order
of magnitude higher than that of PM567, which nonetheless makes this material very adequate for
applications in optical filters.
With the aim of studying the effect that both the linkage of the chromophore to the inorganic
nucleus and the degree of functionalization have on the photophysical and laser properties, we
proceeded to the synthesis of two model dyes (Figure 2) as well as a monosubstituted POSS
derivative with only one dye molecule (Figure 1).
X
N
N3
N3
N3
N3
N3
N3
N3
N
R
1)
O
Si
Si
O
O
O
O
Si
O
Si
Si
O Si
O
O
O
O
Si
Si
O
R
NN
2)
X
R
N
N N
cat Cu(I)
N
N
N3
R
R = connector
N
R
O
Si
Si
O
O
O
O
Si
O
Si
Si O Si
O
O
O
O
Si
Si
O
N
N N
R
N
N
N
N
N
N N
R
N
N
N
N
R
X = fluorescent or laser probe
Figure 1
N
N
F
B
N
N
F
F
B
N
N
N
F
Figure 2
71
The control of the degree of substitution of POSS systems is a very complex task, since in this type
of coupling reactions a triazole group is generated, which has autocatalytic activity acting as Cu(I)
activating ligand, thus rendering polysubstituted compounds preferentially. Recently, our group has
found new reaction conditions that solve this problem and permit an efficient access to
monosubstituted POSS systems. This will allow us to address the study of the modulation of the
emission wavelength by varying the degree of substitution, and thus obtaining a system tunable in a
wide interval of wavelengths. In addition, this hybrid dye derived from POSS with one fluorescent
chromophore and seven additional reactive groups available for further functionalizations is a very
interesting precursor for a wide variety of POSS derivatives with potential applications in materials
science and biomedicine.
The substituents incorporated at the meso position of PM567 for the synthesis of the model
dyes, as well as their mono-anchoring to POSS do not lead to a significant modification of the
photophysical properties of the dye of reference [3].
The laser properties of these new dyes have been studied in liquid phase by transversal
pumping with a Nd:YAG laser (532 nm), at 5.5 mJ/pulse and 10 Hz repetition rate. The chemical
modifications incorporated into the dyes improve significantly the lasing efficiency and
photostability with respect to those of PM567. Only in the case of the monosubstituted hybrid dye
was a slight decrease in its lasing efficiency observed, albeit not in its photostability since it
maintains a 97% of its initial laser emission after being pumped with 100000 pulses. This increase
in the photostability of the chromophore through its attachment to the inorganic component
confirms the initial hypothesis that the incorporation of silicon into the system improves its thermal
properties.
The results obtained with the newly synthesized dyes open great expectations for the
development of new biomedical and photonic systems based on them.
The authors thank MICINN for financial support (Project: MAT2007-65778-C02-01 and
CTQ2006-15515-C02-02). We also thank Dr. A. Costela and Dr. I. García-Moreno of Instituto de
Química Física “Rocasolano” of CSIC for their collaboration in the laser characterization of the
new dyes.
References
[1] O. García, R. Sastre, I. García-Moreno, V. Martín, A. Costela. J. of Physical Chem. 112 (38) (2008) 14710. [2] G.
Barré; D. Taton; D. Lastécouères; JM. Vincent. J. Am. Chem. Soc. 126 (2004) 7764- 7764.
[3] F.López Arbeloa; T.López Arbeloa; I.López Arbeloa; I.García Moreno, A.Costela; R.Sastre, F.AmatGuerri. Chem. Phys. Lett. 299 (1999) 315-321.
72
Excited state double hydrogen-bonding induced by charge transfer in isomeric
bifunctional azaaromatic compounds: pyrido-indole and pyrrolo-quinoline
derivatives.
Dolores Reyman, Cristina Díaz-Oliva
Departamento de Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain.
In this review, we analyze ground and excited state effects induced by hydrogen bonding solvent in
two series of isomeric bifunctional azaaromatic chromophores based on pyrido-indole [α, β, γ, or δcarboline and methylene-bridged 2-(2’-pyridyl)indoles] and pyrrolo-quinoline derivatives. These
families possess both a hydrogen bond donor (N-H pyrrolic group) and a hydrogen bond acceptor
(pyridine-type nitrogen atom). In addition, these compounds present photo-induced changes in the
electronic distribution, which alter the acid/basic properties in both groups in the excited state. This
charge transfer originates a variation of its reactivity. These groups can originate an intermolecular
double hydrogen bond altering completely the excited-state behavior of the chromophore,
provoking phototautomerization phenomena. Depending on the spatial separation between the
functional groups, this phototautomerization can occur directly by formation of dimeric species or
by an appropriate protic partner acting simultaneously as a proton donor and an acceptor. Hence,
the photophysic of these compounds show a high sensitivity to solvent and environment.
Structures and Acronyms of the Compounds
N
N
N
N
N
N
N
H
H
H
N
H
PQ
H
[α, β, γ, or δ-carbolines]
H
N
N
N
N
N
N
N
H
DPC
TPC
(CH2)n
N
N
H
PC
N
N
H
PyIn-n
73
Molecular Logic with Photonic Devices – Quo Vadis?
U. Pischel
Departamento de Ingeniería Química, Química Física y Química Orgánica, Facultad de Ciencias Experimentales,
Universidad de Huelva, Campus de El Carmen s/n, 21071 Huelva
The first molecular logic gate was realized by de Silva et al. some 15 years ago by implementing
AND logic with a fluorophore-receptor1-receptor2 architecture, involving photoinduced electron
transfer (PET) processes tuned by ions as chemical inputs.[1] Since then diverse research efforts
have been undertaken in this direction,[2,3] almost always proclaiming the molecular computer as
main objective. Very often the question is asked: How far are we from this aim? In this contribution
I will draw a few essential lines along what could be options for the further advance in molecular
logic. Related to examples from our own research activities in this field, the discussion will focus
on the molecular illustration of concepts like multi-valued logic and reversible logic.[4,5] In all
cases we have used fluorophores as signalling units, either implemented in a molecular conjugate
together with appropriate receptors for chemical inputs or in a simple intermolecular mixture (socalled cocktail approach). Logic switching of optical output signals, which will be discussed for the
concrete systems, was enabled by controlling photoinduced electron transfer (PET), internal charge
transfer (ICT), and electronic energy transfer (EET).
Multi-valued Logic. In contrast to conventional binary logic, multi-valued logic leads to increased
information density, because each signal (input or output) might exist in more than two possible
states (i.e., 0 and 1 for binary logic). In a very recent example we have realized the first fully
assigned ternary logic gate, where each input and output can be expressed by three possible values:
0, 1, and 2. For this purpose we designed a tri-stable fluorescent molecular switch, which upon
application of degenerate inputs in form of fluoride anions shows three clearly distinguished and
discrete fluorescence output signals.[4] The inherent switching principle relies on a fine-tuned
competition between PET and EET, as well as switching of ICT properties. The achieve such
intricate photophysical scenario a fluorophore1-receptor-fluorophore2 conjugate based on 1,8naphthalimide, a tertiary amine as proton receptor, and the ICT fluorophore 4-amino-1,8naphthalimide was realized (compound 1, cf. Scheme 1).
EET
O
O
ICT
N
N
N
O
O
PET
NH2
1
H
O
N
O
N
PET
ICT
NH2
2
3
Scheme 1. Structures of 1, 2, and 3, which were used for the realization of multi-valued logic and reversible logic.
Reversible Logic. Another concept, which has attracted recently elevated interest in computational
engineering as well as in quantum computing is reversible logic. Most logic gates are characterized
by the loss of information while converting input strings into outputs. For example, the exclusive
74
OR gate (XOR gate) produces identical output vectors for 0,0 and 1,1 input strings (output = 0) as
well as for 0,1 and 1,0 inputs (output = 1). Inspired by this problem, which leads to loss of
information and ultimately the release of heat, we have developed a rather straightforward approach
toward the first example of reversible molecular logic.[5] It is based on two independently acting
and readily available fluorescent molecular switches (a 4-amino-1,8-naphthalimide, 2 and an
anthracene derivative, 3, cf. Scheme 1), that can be addressed by the same set of chemical inputs
(protons and basic anions) and lead to the parallel implementation of XOR and YES gates by
compounds 2 and 3, respectively. The underlying photophysical processes relate to PET and ICT
mechanisms. The thus achieved combination of YES and XOR outputs yields one-to-one mapping of
input to output and vice versa, i.e., reversible logic.
References
[1] A. P. de Silva, H. Q. N. Gunratne, C. P. McCoy, Nature 364 (1993) 42.
[2] U. Pischel, Angew. Chem. Int. Ed. 46 (2007) 4026.
[3] K. Szaciłowski, Chem. Rev. 108 (2008) 3481.
[4] R. Ferreira, P. Remón, U. Pischel, J. Phys. Chem. C 113 (2009) 5805.
[5] P. Remón, R. Ferreira, J.-M. Montenegro, R. Suau, E. Pérez-Inestrosa, U. Pischel, ChemPhysChem in press.
75
On board chemical monitoring of the aircraft hydraulic fluid using Ru(II)
luminescent complexes and frequency-domain lifetime measurements
Manoel Veiga1, Javier L. Urraca2, Clara Cano1, María C. Moreno-Bondi2 and Guillermo Orellana*1
Chemical Optosensors and Applied Photochemistry Group,
Dpmt. of Organic Chemistry and 2Dpmt. of Analytical Chemistry,
Faculty of Chemistry, Universidad Complutense de Madrid, 28040 Madrid, Spain;
Phone: +34-913944220; fax: +34-913944103; www.ucm.es/info/gsolfa
1
Current hydraulic fluids used for passenger aircrafts are based in phosphate esters due to their
resistance to fire and physical properties. Nevertheless, phosphate esters are highly hygroscopic.
Dissolved water causes hydrolysis, increasing the acidity of the medium and putting at risk the
hydraulic system due to corrosion. Other species such as molecular oxygen, may also contribute to
accelerate corrosion due to oxidation processes [1]. Therefore, the aircraft hydraulic fluid should be
checked regularly for those chemical “markers” (moisture, acidity and oxygen). At present,
assessing the condition of hydraulic fluid in an aircraft is laborious, time-consuming and expensive.
Therefore, the fluid is typically tested less than once a year, with the risk of unscheduled
maintenance if the fluid has exceeded its limits of usage. Consequential interruption of the service
bears a significant economic cost to airlines.
The “SuperSkySense” project (Figure 1, www.superskysense.eu) aims to develop an autonomous
on board system capable of monitoring the fluid condition, to provide an early warning in case the
hydraulic fluid begins to degrade. At UCM we are developing three specific luminescent Ru(II)
polypyridyl complexes as indicator dyes [2] sensitive to moisture, dissolved oxygen and acidity, as
well as their corresponding sensing layers. The Ru(II) complex is embedded within a polymer
matrix [3], which is in contact with the hydraulic fluid. In the presence of the specific contaminant
species, the luminescence lifetime of the Ru(II) complex is dynamically quenched. The dedicated
monitoring unit is based on frequency-domain lifetime measurements.
Figure 1. The SuperSkySense consortium “sensory” partners.
Acknowledgements: This project is being funded by the EU (Aeronautics and Space Programme AST5-CT-2006030863), the Spanish Ministry of Science and Innovation (CTQ2006-28331-E/BQU and TRA2007-30965-E) and the
UCM-B. Santander (GR58-08-910072).
References
[1] M.E. Okazaki, S. M. Abernathy, J. W. Laurent, J. Synth. Lubr. 10 (2) (1993) 107.
[2] G. Orellana, D. García-Fresnadillo, Optical Sensors: Industrial, Environmental and Diagnostic Applications, Springer
Ser. Chem. Sens. Biosens. Vol. 1, edited by R. Narayanaswamy and O.S. Wolfbeis, Springer, 2004.
[3] G. Orellana, M.C. Moreno-Bondi, D. García-Fresnadillo, M.D. Marazuela, Frontiers in Chemical Sensors: Novel
Principles and Techniques, Springer Ser. Chem. Sens. Biosens. Vol. 3, edited by G. Orellana and M.C. Moreno-Bondi,
Springer, 2005.
76
New Bodipy Dyes with Wavelength-Finely Tunable
Laser Action in the Red-Near Infrared Spectral Region
A. R. Agarrabeitia1, J. Bañuelos 2, A. Costela 3, G. Durán-Sampedro1, I. García-Moreno3, F. López Arbeloa2, I.
López Arbeloa2, M. J. Ortiz1
1
Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid
2
Departamento de Química Física. Facultad de Ciencia y Tecnología, Universidad del Pais Vasco
3
Instituto de Química Física “Rocasolano”, CSIC. Madrid
The development of new fluorescent BODIPY (BDP) dyes has become a booming area of
research due to the potential applications of these dyes, as sensors in biology and in clinical
diagnosis, as photosensitizers for photodynamic therapy, in laser generators, waveguides,
manufacture of light emitting diodes (OLED), photovoltaic cells and electroluminescent devices
including [1]. All these and other emerging applications are conditioned by the emission
wavelength of the dye and by its emission quantum yield and stability under the working conditions
of each specific application.
One of the most important characteristics of the BDP chromophore is that it is possible to
vary its spectroscopic properties relatively easily by changing the substituents. Thus, an increase in
the conjugation allows obtaining new BDP dyes with emission in the red spectral region. The
development of red emitting dyes is very interesting from a technological and commercial point of
view. In fact, such dyes are demanded in telecommunications, photovoltaic devices, and in
biomedicine for non-invasive diagnosis techniques. The aim of this contribution is the preparation
of new red-shifted dyes based on BDP core.
8
1
7
2
6
3
N
N
B
F
5
F
BODIPY chromophore
In this work, we have carried out the synthesis, photophysical and lasing characterization of
new BODIPY dyes with absorption and emission spectra shifted towards longer wavelengths by
extending the conjugation of the BDP core at the 3,5-positions. The BODIPY fluorophores can be
easily functionalized at these positions with two 4-formylphenyl groups by palladium-catalyzed
coupling reaction of the 3,5-dichloro-4,4-difluoro-8-(4-tolyl)-4-bora-3a,4a-diaza-s-indacene[2]
using the Suzuki reaction [3]. In these conditions, BODIPY derivative 1 was obtained. Compound 1
was transformed in the dicyanovinyl and diethoxycarbonylvinyl-substitued fluorophores 2 and 3,
respectively, by Knoevenagel condensation.
77
Ar
N
N
B
F
OHC
Ar
N
B
F
CHO
1
2
Ar
N
N
N
B
F
F
NC
NC
F
CN
MeO2C
CN
MeO2C
F
CO2Me
3
CO2Me
These new BODIPY derivatives present an extended aromatic framework through the
substituents incorporated in 3- and 5-positions. This leads to an important bathochromic shift of
absorption and fluorescence spectral bands, which place in the red part of the visible (emission at
600-620 nm). Moreover, it is expected that the extension of the π-system will result in dyes with
high absorption and fluorescence emission probability. It is known that one of the mayor drawbacks
of the red emitting dyes is their low fluorescence efficiency, due to the low energy gap between the
ground and excited state favouring the probability of non-radiative processes. In the present case,
the fluorescence quantum yields (0.5-0.7) and lifetimes (3.5-5.0 ns) of these new BODIPYs are
relatively high, suggesting the possibility of using these dyes as active media of efficient tunable red
dye lasers.
The laser action of these dyes strongly depends on the substituent and the nature of the
solvent. Thus, under transverse pumping to 532 nm, compound 1 in ethyl acetate provides laser
emission centered at 615 nm with a conversion efficiency of 14%. The extent of conjugation in
positions 3 and 5, although it does take a reduction in the efficiency laser emission, is significantly
shifted toward the red. The laser emission bands of compounds 2 and 3 are centered at 648 and 632
nm, respectively. These three dyes have a high photostability, maintaining 90% of its initial
emission after 100,000 pulses at 10 Hz in static displays, superior to that of commercial dyes with
laser emission in the same spectral region as summarized here, such as Perylene Red and
Rhodamine 640. Replacing controlled of these derivatives BDP allows to obtain tunable laser
emission with a bandwidth of 0.15 cm-1 and tuning range of up to 50 nm. So with these three dyes it
is possible to cover the spectral range 590-680 nm in a continuous way and with stable and small
line width.
Bibliografía
[1] a) Loudet, A.; Burgess, K. Chem. Rev. 2007, 107, 4891-4932. b) Wood, T. E.; Thompson, A. Chem. Rev. 2007, 107,
1831-1861. c) Ulrich, G.; Ziessel, R.; Harriman, A. Angew. Chem., Int. Ed. 2008, 47, 1184-1201.
[2] Qin, W.; Rohand, T.; Baruah, M.; Stefan, A.; Van der Auweraer, M.; Dehaen, W.; Boens, N. Chem. Phys. Lett.
2006, 420, 562-568.
[3] Rohand, T.; Qin, W.; Boens, N.; Dehaen, W. Eur. J. Org. Chem. 2006, 4658-4663.
78
Matlalina, el fluoróforo del Lignum nephriticum de N. Monardes.
A. U. Acuña1, F. Amat-Guerri2, P. Morcillo2, M. Liras2, B. Rodríguez2
1
2
Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid
Instituto de Química Orgánica General, CSIC, Juan de la Cierva 3, 28006 Madrid
La primera referencia a la emisión de fluorescencia en disolución se debe al médico sevillano N.
Monardes [1], el cual describió en el siglo XVI el sorprendente “color” azul de la infusión de una
madera de Nueva España (Méjico) utilizada en el tratamiento de enfermedades renales. La extraña
propiedad (fluorescencia) del Lignum nephriticum, como se denominó más tarde la madera, atrajo
la atención de Boyle, Newton, Goethe, Herschel y una larga serie de ilustrados e investigadores a lo
largo de cuatro siglos [2]. Sin embargo, en el siglo XIX ya no se podían obtener muestras de la
madera en Europa y su origen botánico se ignoraba. A principios del siglo pasado, y gracias a los
esfuerzos de una serie de botánicos, se propusieron los géneros Eisenhardtia y Pterocarpus como
posibles fuentes del L. nephriticum. Más recientemente, nosotros encontramos [2] en textos de Fray
Bernardino de Sahagún (ca. 1500-1590) que los médicos aztecas precolombinos ya utilizaban dicha
madera y, además, conocían el “color” azul de su infusión. La madera se obtenía del coatli,
(Eysenhardtia polystachya (Ort.) Sarg.), una leguminosa endémica de Mesoamérica. Aunque esto
resolvía el enigma del origen botánico del L. nephriticum, planteaba un nuevo problema, ya que,
sorprendentemente, no se había encontrado ningún compuesto intensamente fluorescente y
fácilmente soluble en agua entre los componentes ya estudiados de E. polystachya [3].
Nosotros aislamos de E. polystachya un raro flavonoide, no fluorescente y muy soluble en agua, que
se encuentra en grandes cantidades (1-2 % p. seco) en la madera del árbol, y que ya había sido
caracterizado previamente [3]: (αR)-3'-C-β-glucosil-3,4,2',4',α-pentahidroxydihidrochalcona
(coatlina B). Curiosamente, este flavonoide en disolución acuosa ligeramente alcalina y en
presencia de oxígeno atmosférico se transforma en una nueva estructura tetracíclica intensamente
fluorescente (matlalina, Φf = 1.0 ± 0.1, λf = 460 nm):
HO
OH
3
OH O2, H2O, rt
4'
(R)
R
3'
2'
O
4
coatlina B (1)
O
R
OH
OH O
HO
OH
R = HO
HO
O
OH
OH
O
CO2H
matlalina (2)
La reacción transcurre rápidamente con una eficiencia del 100 % a temperatura ambiente. El
mecanismo de reacción más probable consiste en una cascada de procesos, dos de ellos oxidativos,
que se originan a partir del monoanión de coatlina B y que no tienen paralelo en la química de
compuestos naturales.
Agradecimientos
Agradecemos la constante guía del Dr. S. Castroviejo (Real Jardín Botánico, CSIC, Madrid) a lo
largo de este trabajo y la valiosa ayuda del Dr. V. Hornillos (IQFR-IQOG, CSIC, Madrid).
Referencias
[1] Monardes, N. Dos Libros/El vno trata de todas las cosas que traen de nuestras Indias occidentales que sirven al
uso de Medicina…, en casa de Sebastian Trugillo, Sevilla, 1565.
[2] a) Acuña, A. U. J. Chem. Edu. 84 (2007) 231. b) Acuña, A. U., Amat-Guerri, F. Springer Ser. Fluoresc. 4 (2008) 3.
[3] a) Beltrami, E., De Bernardi, M., Fronza, G., Mellerio, G., Vidari, G., Vita-Finzi, P. Phytochemistry 21 (1982)
2931. b) Álvarez, L., Delgado, G. Phytochemistry 50 (1999) 681.
79
80
POSTERS
81
82
Photoinduced oxidation of pyrene on the CdSe quantum dot surface
Jordi Aguilera-Sigalat,1 Raquel E. Galian,2 and Julia Pérez-Prieto1
1
2
Institute of Molecular Sciences, Valencia, Spain 46980
Department of Analytical Chemistry (ICMOL), University of Valencia, Spain 48100
E-mail: [email protected]
Quantum dots (QDs) offer great promise as nano-materials with a potential application in optics,
electronics, and catalysis. There are very few reports on photoinduced transformations of organic
compounds on QD surfaces. One example is the reduction of aromatic azides to aromatic amines
using sodium formate as a sacrificial electron donor [1].
The aim of this work is to study the transformation of pyrene derivatives by the combined use of
light and CdSe nanoparticles. Quantum dot QD-I was synthesized using the procedure described by
Peng and Peng [2]. Its size is close to 2.60 nm, according to the maximum of the first exciton (at
523 nm) and in agreement with High Resolution Transmission Electron Microscopy (HRTEM)
analysis.
It is well known thiol groups bind well to QD surfaces. Therefore, to improve the interaction of the
pyrene chromophore with the nanoparticle, pyrene-thiol 1 was synthesized following the Yamamoto
procedure [3] and a standard ligand exchange methodology was used to obtain pyrene derivatized
nanoparticle QD-II (scheme 1). This material was characterized by proton nuclear magnetic
resonance (1H-NMR), UV-visible absorption, fluorescence, and IR (FTIR) spectroscopies. The
NMR spectrum showed a broadening of the pyrene signals. Moreover, the multiplicity of the CH2–
S signal changed to a triplet, which is indicative of the binding of the ligand to the QD surface via
the SH group. In addition, the UV-visible spectrum indicates an important degree of ligand
exchange.
Irradiation (laser Nd-YAG) of aerated and deaerated THF solutions of QD-II at 355 nm for 90
minutes showed disappearance of the typical bands of pyrene, between 300 and 350 nm (figure 1a
and 1b). A new band with a maximum around 350 nm was observed in the aerated sample, while a
featureless broad absorption band (300-550 nm) was obtained when the irradiation was performed
under an inert atmosphere. UV-Vis and FTIR spectra suggest that a pyrene-quinone and a pyrenehydroxiquinone are generated upon irradiation under oxygen and nitrogen, respectively. HRTEM
images give more information about these new structures and indicate the presence of QDnanoparticles.
In addition, the intermolecular version, i.e. excitation of QD-I in the presence of 1, gave rise to
similar changes, but longer irradiation times were needed to reach the same transformation. By
contrast, when the intermolecular irradiation was performed using pyrene instead of 1, the former
remained unchanged. Finally, to ensure that the nanoparticles were required for the transformation
83
of the pyrene-thiol 1, this was irradiated in the absence of the QD, but no significant changes were
observed. The mechanism for the photoinduced oxidation of pyrene will be discussed.
AIR
3
N2
3
2
(III) before irradiation
(III) after irradiation
2
Abs
Abs
(III) before irradiation
(III) after irradiation
1
1
0
0
300
350
400
450
λ, nm
500
550
600
650
300
350
400
450
500
550
600
650
λ, nm
Figure 1: UV-visible spectra of QD-II in THF under (a) deaerated or (b) aerated THF before and after 90 minutes
irradiation.
Acknowledgements: Our thanks to the Ministerio de Educación y Ciencia (CTQ2008-6777-C0201), Ramón y Cajal contract for R.E.G. and Generalitat Valenciana (GVPRE/2008/096) for
financial support.
References
[1]. Manoj Warrier, Michael K. F. Lo, Harold Monbouquette and Miguel A. Garcia-Garibay,
Photochemical Photob. Sci., 2004, 3, 859.
[2]. Z. Adam Peng and Xiaogang Peng, J. Am. Chem. Soc. 2001, 123, 183.
[3]. Kazuaki Ishihara, Masaya Nakayama, Suguru Ohara, Hisashi Yamamoto, Synlett. 2001, 7,
1117.
84
Efficient and stable amplified spontaneous emission (ASE) from dye-doped
polymeric planar waveguides
L. Cerdán1, A. Costela1, I. García-Moreno1, O. García2, R. Sastre2, M. Calle2, D. Muñoz2, and J. de Abajo2
1
2
Instituto de Química Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain
Instituto de Ciencia y Tecnología de Polímeros, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
The use of dye-doped materials in the form of thin films incorporated into waveguiding structures
has attracted much attention over the last decade for their applications in integrated photonics.
These materials combine the processing flexibility of polymers with the tunability and high
efficiency of lasing dyes, and their waveguiding structure allows for easily achieving high power
density ASE emission.
Although in bulk, polymer-based dye-doped materials have demonstrated excellent photostability
[1,2], a major drawback in the thin film devices is their limited operational lifetime due to dye
degradation, and any realistic application passes for extending it. It is well known that improvement
in the polymer thermal conductivity reduces dye degradation, and thus assures an increase in the
device’s lifetime [2,3]. Here we have proceeded to study and systematically characterize the
properties of the ASE emission from thin films of two different laser dyes, Pyrromethene 597
(PM597) and Perylene Orange (Per240N), incorporated into polymers with different thermal
conductivities: poly(methyl methacrylate) (PMMA), two newly synthesized fluorinated polyimides
(FPI) named 6F-6F and 6F-IMMDA, and polycarbonate (PC1023), whose repeating units are
shown in Fig. 1.
CH3
PMMA
H2C
C
O
n
C
CF3
F 3C
C
O
C
CH3
O
C
CF3
F3C
C
O
N
N
n
m
6F-6F
O
O
C
CF3
O
O
CH3
O
CF3
N
N
O
CH3
O
O
O
CH2
n
6F-IMMDA
PC1023
Figure 1. Polymers repeating unit
Asymmetric planar waveguides consisting of the dye-doped polymeric thin films deposited onto
glass substrates were prepared using the extender roller technique [4]. Pump thresholds for the onset
of ASE emission, collapse of the full width at half maximum (FWHM) in the emission spectrum,
saturation intensity, and efficiency curves were determined for thin films of different thicknesses
and different dye concentrations. Optimum film thickness was found to be about 9 µm in all cases.
Optimum dye concentration was found to be 2.5 × 10-2 M for dye PM597 and 1 × 10-2 M for dye
Per240N.
ASE gain measurements were carried out in PMMA- and FPI-based waveguides using the variable
stripe length method (see details in [5]). Net gain coefficients of up to 84 and 93 cm-1 were obtained
for PM597 incorporated into PMMA and FPI thin films, respectively. When the dye was Per240N
the gains were 71 cm-1 in PMMA film and 61 cm-1 in the FPI film.
85
Dye degradation rate was assessed in PMMA, FPI and PC1203 films by pumping the samples in the
same position with an intensity of 220 kW/cm2 at 5 Hz repetition rate. The actual evolution of the
ASE emission as a function of the number of pump pulses for dyes PM597 and Per240N in the
different polymeric media is presented in Fig. 2 (a) and (b), respectively. For PM597 (Fig. 2(a)) the
best result was obtained in the 6F-6F films, where 40000 pump pulses were necessary for the ASE
emission dropping to 50% of its initial value. For Per240N (Fig. 2(b)) the long term behaviour is
similar in all the polymer media studied, although it is in PMMA were a higher number of pump
pulses (68700) is necessary for the ASE emission dropping by 50%.
Figure 2.Percentage of the initial emission output as a function of the number of pump pulses for (a) PM597 and (b)
Per240N in the different polymeric thin films.
In the films doped with PM597 the differences in photostability can be related to the differences in
the thermal properties of the polymer families. The thermal stability of the FPIs at least doubles that
of PMMA, whereas the thermal stability of PC1023 is intermediate between those of PMMA and
FPIs. Thus, the heat transferred from the dye molecule to the matrix is more rapidly dissipated in
the FPI films, avoiding thermal degradation of the dye. In the films doped with dye Per240N, the
photostability seems to be independent of the thermal properties of the films. This could be
attributed to the degradation of the perylene dye being more chemical than thermal, whereas the
pyrromethene dyes are more stable chemically.
References
[1] A. Costela , I. García-Moreno, R. Sastre, Handbook of Advanced Electronic and Photonic Materials and Devices.
Vol. 7, edited by H.S. Nalwa, Academic Press 2001.
[2] A. Costela, I. García-Moreno, R. Sastre, Phys. Chem. Chem. Phys. 5 (2003) 4745.
[3] R. Duchowicz, L.B. Scaffardi, A. Costela, I. García-Moreno, R. Sastre, A.U. Acuña, Appl.Opt. 42 (2003) 1029.
[4] A. Costela, O. García, L. Cerdán, I. García-Moreno, R. Sastre, Opt. Express 16 (2008) 7023
[5] L. Cerdán, A. Costela, I. García-Moreno, O. García, R. Sastre, Appl. Phys. B DOI: 10.1007/s00340-009-3518-8
(2009).
86
New Laser Dyes Based on Boron Complexes with Tunable Emission on the
Whole Visible Region: A Theoretical Approach
J. Bañuelos Prieto, F. López Arbeloa, M. Liras and I. López Arbeloa
Departamento de Química Física,, Universidad del País Vasco (EHU-UPV), Apartado 644, 48080-Bilbao
Boron-dipyrromethene complexes are one of the most used laser dyes family as active media of
tunable dye lasers in the green-yellow visible region of the electromagnetic spectrum, displacing
rhodamine dyes, considered as the benchmark. The laser emission of BDP dyes is highly efficient
and photostable, owing to their chemical robustness and their unique photophysical properties. In
fact, BDP dyes have been successfully applied in several scientific and technological fields, not
only in photonic as active media of syntonizable lasers, but also as molecular probes or sensors in
biological systems and in photoelectronic devices (antenna and holographic systems).
The emission region of BDP dyes can be tuned by changing their molecular structure in a controlled
way. Indeed, several examples can be found in the literature, where the BDP emission has been
shifted to the red part of the visible and even the near infrared, by means of the extension of the
chromophoric π-system of the BDP core through fused aryl groups, delocalized substituents or
inserting heteroatoms at different positions of the chromophore (aza-BDPs). However, in our
knowledge, just few BDP structures with blue emission have been published until now. Only Boyer
and coworkers at beginning of the nineties briefly reported the photophysical and lasing properties
of a series of molecular structures based on different boron complexes, where the pyrrol groups of
BDP were replaced by imidazol or benzene rings, developing in this way new chromophores [1]. In
the last years, we have extensively studied the photophysical properties of several derivatives of
BDP in different media [2].
Taking into account the Boyer idea, and in order to covert the whole Vis spectral region with dyes
based on an common BDP chromophoric skeleton, we have realized quantum mechanical
calculations to predict the absorption and emission properties of new BDP molecular structures,
including the incorporation of several heteroatoms (Figure 1).
N
N
N
B
blue shifted
N
N
N
F F
2,6-IM
N N B N N
F
F
TM
N
B
N
F F
SM
O
O
N
B
N
F
F
OM
N
B
N
F
F
1 ,7 -IM
N
F
F
BDP
spectral transition probability
N
B
N
N
red shifted
N
Py-IN
IN
2,6-IM
N
i-IN
B
N
F
F
8 -IM
8-IM
TM
BDP
1,7-IM
N
N
B
N
N
F F
Py-IN
OM
N
OM
SM
B
N
F
F
IN
N
400
450
wavelength (nm)
500
550
B
N
F F
i-IN
Figure 1. Theoretically predicted absorption and fluorescence band positions and probabilities of red and blue-shifted
BDP derivatives
In order to corroborate the validity of the quantum mechanical calculations, we have proceeded to
the synthesis and spectroscopic characterization of one of the proposed structures, concretely the
boron aza-anthacene derivative. As illustrated in Figure 2, this derivative present absorption and
87
fluorescence emission in the blue part of the visible region, with a nice vibrational structure. The
fluorescent decay curve is analyzed as an one-exponential decay with lifetime around 2 ns. Present
results suggest that the experimental data are in adequate concordance with theoretical results.
3
B
N
F F
BTAA
2
1
0
300
1000
Counts
4
intensidad fluorescente (u.a.)
N
-1
-1
absorcion molar (10 M cm )
N
4
100
10
1
350
400
450
longitud de onda (nm)
500
0
5
10
15
20
Time (ns)
Figure 2. Absorption and fluorescence spectra (left) and fluorescence decay curve (right) of BTAA dye in liquid
Consequently, quantum mechanical calculations have revealed as a powerful tool to help in the
interpretation of experimental results and to orient the synthesis of new structures or derivatives
with specific physicochemical properties. From present results, it can be concluded that appropriate
modifications of the basic structure of BDPs can shift the emission both, to the red or to the blue
region. Therefore, it seems that the whole visible can be covered just with one laser dye family
choosing the adequate substituent. Actually, we are analyzing the synthesis viability of these
theoretically proposed structures based on the BDP chromophoric core.
References
[1] G. Sathyamoorthi, M-L. Soong, T. W. Ross, J. H. Boyer Heteroat. Chem. 4 (1993) 603; T. W. Ross, G.
Sathyamoorthi, J. H. Boyer Heteroat. Chem. 4 (1993) 609.
[2] F. López Arbeloa, J. Bañuelos, V. Martínez, T. Arbeloa, I. López Arbeloa Int. Rev. Phys. Chem. 24 (2005) 339.
88
Single Molecule Sudies of Catalytic Reactions of Haloperoxidase Enzymes by
Confocal Fluorescence Microscopy
V. Martínez Martínez1, G. De Cremer2, Maarten B.J. Roeffaers2, Johan Hofkens3, F. López Arbeloa1
1
2
Departamento de Química Física / Universidad del País Vasco-EHU (Spain)
Department of Microbial and Molecular Systems/ Katholieke Universiteit Leuven (Belgium)
3
Department of Chemistry / KatholiekeUniversiteit Leuven (Belgium)
Single Molecule Fluorescence Spectroscopy technique (SMFS) offers excellent (spatio/temporal)
resolution and sensitivity that can provide information not possible by conventional techniques in
macroscopic systems [1]. In this communication, confocal microscopy is applied to the study in situ
the dynamic aspects of an enzymatic reaction.
Concretely, we study the catalytic action of the haloperoxidase biocatalyst Curvularia verruculosa, a
type of vanadium-haloperoxidase enzyme, which catalyze the oxidation of halides (X-) by hydrogen
peroxide (reaction 1). This reaction is of interest for the synthesis of halogenated organic
compounds (reaction 2) important applications in the production of antimicrobial agents, cosmetics,
etc [2]. There is a controversy about the activation site for the secondary reaction because of the
discrepancy of the regio/estereo-selectivity in the reaction products. Some authors claim that the
formed “X+” species is released to the solution but others authors have claimed certain selectivity in
the reaction, suggesting that it occurs at the pocket of the active side of the enzyme [2,3]
Primary reaction:
H2O2 + X-
Secondary reaction:
HOX + H2O
HA + HOX
AX + H2O
The catalytic activity of this reaction was tracked in situ by confocal fluorescence microscopy
(CFM). The successfully application of this technique depends, mainly, on choice of the adequate
substrate for the catalytic reaction under study. In that sense, fluorigenic probes (non fluorescent
substrate that becomes fluorescence after catalytic action, i.e. cleavage) are desirable since they
allow the collection of data for extended period of times (no photobleaching).
In this study, a non fluorescent fluorescein derivative, aminophenyl fluorescein (APF), is chosen.
This derivative specifically reacts with hypohalites to form the highly emissive fluorescein
compound (Figure 1)
NH2
O
O
O
O
O
O-
O
NH
COOCOO-
HBrO
Figure 1. Structure of the fluorogenic probe to monitor the reaction.
The technique consists in focus the laser beam in the inmobilized enzyme (in this case in agarose
gel), adding the reactants in solution (after adjusting pH, concentration ...) and monitoring the
fluorescence intensity fluctuations occurring per catalytic cycle (Figure 2)[4].
89
Figure 2. Short time period for the fluorescent intensity time fluctuation traces of curvularia verruculosa enzyme.
The second part of this contribution is focus to elucidate the mechanism of the secondary reaction
by means of the recording of the FRET (“Fluorescence Resonance Energy Transfer”) signal (Figure
3) with two-color detection set up (green and red channels). The enzyme is label (close to its active
site) with a dye emitting in the red region which is not directly populated in the excitation process
but rather by the energy transfer from a green-fluorescent donor component (fluorescein channel).
NO FRET signal
fluorescent
product in bulk
fluorescent product
inside enzyme
FRET signal
enzyme label
Figure 3. Scheme of FRET experiments in halopeoxidase enzymes.
By this experimental procedure, the correlated signal in the red channel (positive FRET) respect to
the green one (fluorescein channel) monitores the secondary reaction taking place in/near the active
center of the enzyme (< 10 nm distance). In the case of negative FRET (no signal registered in red
the channel) the reaction takes place in the bulk solution.
References
[1] P. V. Cornish, T. Ha, ACS Chem. Biol. 2 (2007) 53.
[2] A. Butler, J.V. Walker, Chem. Rev. 93 (1993) 1937
[3] A. Messerschmidt, R. Wever, Proc. Natl. Acad. Sci. U. S. A. 93 (1996) 392
[4] V. Martínez, G. De Cremer, M.B.J. Roeffaers, M. Sliwa, M. Baruah, D.E. De Vos, J. Hofkens , B.F. Sels, JACS 130
(2008) 13192.
90
Use of Polarized Spectroscopy to Prove the Presence of Rhodamine Aggregates
Formed in Surfactant/Clay Hosts.
S. Salleres, T. Arbeloa , C. Corcóstegui.and F. López Arbeloa
Departamento de Química Física, Universidad del Pais Vasco (UPV-EHU), Apartado 644, 48080-Bilbao
Recent technological applications of fluorescent dyes require the incorporation of the dye molecules
into solid host materials. It is generally assumed that the adsorption of dyes in solid surfaces leads
to the dye aggregation, reducing the fluorescence ability of the dye. This is the case for Rhodamine
6G (R6G) laser dye adsorbed in solid thin films of Laponite (Lap) clay, in which the fluorescence
ability of the dye is reduced in three orders of magnitude when the dye loading is increased from
0.1 to 60% CEC, due to the formation of non-fluorescent H-type aggregates [1]. The aggregation of
rhodamine dyes in liquid solution is drastically decreased in an organic environment such as ethanol
with respect to in water. Consequently, a hydrophobic ambience in the interlayer space of clays
could reduce the dye aggregation.
The aim of the present work is to alter the hydrophilic character of the pure laponite clay by an
organophilic environment to improve the fluorescence abaility of dye/clay systems. Organophilic
clay system can be elaborated by the inclusion of surfactant molecules (namely dodecyl-trimethyl
ammonium ions, C12TMA) at the interlayer space of clays. For this purpose we have synthesized
five different organoclays by the adsorption of different amounts of C12TMA molecules in the
interlayer space of previously manufactured ordered Lap films. The surfactant content was ranging
from 30 to 170% of the total cation exchange capacity of the clay. The posterior inclusion of R6G
molecules at low loadings (~0.1% CEC) seemed to indicate the adsorption of dye as individual
monomers regardless the shape of the absorption and emission spectra [2] (Figure 1).
B: fluorescence intensity (u.a.)
A: absorbance (a.u.)
OL1
450
500
OL1
OL5
550
wavelength (nm)
600
500
550
OL5
600
650
wavelenght (nm)
Figure 1. Height normalized absorption (A) and fluorescence (B) spectra of R6G in organophilic C12TMA/Lap films as
a function of the surfactant content, from 30 (OL1) to 170 % CEC.
However, the subsequent use of absorption and fluorescence spectroscopies with linearly polarized
light to analyze the orientation of R6G molecules showed that there were different anisotropic
responses for each sample. These results prove the presence of different R6G species adsorbed in
organoLap films which were not adequately detected by conventional unpolarized absorption and
fluorescence spectroscopies. The presence of different adsorbed species of R6G depends on the
surfactant content.
Absorption (A) and fluorescence (I) spectra were recorded for two orthogonal horizontal H and
vertical V polarization, from which the corresponding absorption (DHV(abs) = AH/AV) and emission
91
(DHV(flu) = IH/IV) dichroic ratios were determined. These dichroic ratios linearly correlate with the
twisting angle δ of the sample around its vertical axis means of [1]
DHV (ab) ≡
D HV (fl) ≡
AH
2 − 3sin2ψ
= 1+
sin2δ
2
AV
sin ψ
IH
= 2cot 2 ψ + (1 − 2 cot 2 ψ )cos 2 (22.5 + δ )
IV
from which the corresponding slopes, the preferential orientation of the absorption and emission
transition moments of R6G with respect to the film normal (the ψ angle) can be evaluated.
For organophilic Lap films (with C12TMA content < 50% CEC), absorption dichroic ratio is nearly
independent of the absorption wavelength (Figure 2, left), suggesting the adsorption of R6G
molecules as monomers. This is not the case for organoLap films with moderate-high C12TMA
content (> 70% CEC), for which the absorption dichroic ratio showed a complex dependence on the
absorption wavelength (Figure 2, right). These results indicate the presence of different absorbing
species of R6G, probably aggregates, with absorption maxima at both side of the monomer
absorption band (H- and J-bands).
2,0
120% CEC
30% CEC
J-band
Monomer
H-band
Y Axis Title
DHV(abs)
1,5
1,0
Monomer
0,5
0,0
460
485
510
535
wavelenght (nm)
560
460
485
510
535
560
wavelenght (nm)
Figure 2. Absorption dichroic ratios of 30% C12TMA/Lap film (left) and 120% C12TMA/Lap film (right) with a very
low dye content, as a function of the twisting δ angle.
Fluorescence polarization confirms the presence of new emitting species for organoLap films with
high C12TMA contents, with emission maxima at longer wavelengths than the monomer
fluorescence band.
These results are interpreted on the basis of the adsorption of R6G at the external surface in those
organoLap films with high surfactant content. Probably, an excess of C12TMA reduces the
accessibility of the interlayer space of the clay, leading to dye aggregation at the external surface.
Furthermore,these results show the potential application of the polarized spectroscopy, not only for
the evaluation of the preferential orientations of the photoactive molecules in ordered host systems,
but also for the identification of new species.
[1] F. López Arbeloa, V. Martínez Martínez, T. Arbeloa, I. López Arbeloa. J. Photochem. Photobiol. C: Photochem.
Reviews.8 (2007) 85-108.
[2] S. Salleres, F. López Arbeloa, V. Martínez, T. Arbeloa and I. López Arbeloa. J. Phys.Chem. C.113 (2009) 965-970.
92
Synthesis and Photophysical Properties of Asymmetric BODIPYs Dyes
PM567 Analogues
A. R. Agarrabeitia1, J. Bañuelos 2, F. López Arbeloa2, I. López Arbeloa2, M. Martínez-Ripoll3, M. J. Ortiz1,
M. Palacios1, M. E. Pérez-Ojeda4
1
Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid
2
Departamento de Química Física. Facultad de Ciencia y Tecnología, Universidad del Pais Vasco
3
Instituto de Química Física “Rocasolano”, CSIC. Madrid
4
Instituto de Ciencia y Tecnología de Polímeros, CSIC. Madrid
Among several fluorescent organic compounds, the family of difluoro-boradiaza-indacenes
or dipyrromethene.BF2 complex, known by the trade name of BODIPY, has received much
attention in the last two decades, being considered at present as one of the most useful and versatile
fluorophores [1]. The current applications of these compounds (biotechnology, electronics, etc..)
require the design and synthesis of new fluorophores with predetermined properties such as high
fluorescence quantum yields, high photostability, low rates of intersystem crossing, large Stokes`
shifts and absorption profiles optimized to achieve success in these applications.
It should be noted that most BODIPYs studied are symmetrical in nature, hence the
importance of innovation in the design of new asymmetric compounds. The work carried out covers
these aspects, and describes the synthesis of four new asymmetric complexes dipyrromethene.BF2
PM567 analogues and the evaluation of their photophysical properties and laser behavior in
solution.
N
B
F
N
N
F
F
1
N
B
F
N
B
F
2
N
F
PM567
N
B
F
3
N
N
F
F
B
N
F
4
Asymmetric BODIPYs 1-4 are obtained by condensation of 2-acetyl-4-ethyl-3,5dimethylpyrrole with a pyrrole molecule conveniently substituted at the 2-position.
The bichomophoric fluorine-BODIPY laser dyes 3 and 4 emit in the red and green part of
the visible, respectively, independently of the used excitation wavelength in both the Vis (direct
excitation of the BODIPY core) and UV (excitation of the substituent fluorene systems) regions
(Figure 1). Therefore, an efficient intramolecular energy transfer process takes place from the
fluorene (donor) to the BODIPY chromophore (acceptor), with emission in the visible. depending
93
5
Vis emission
fluorescence intensity (a.u.)
4
UV exc
4
-1
-1
molar absorption (10 M cm )
on the number of fluorenes and the type of linking to the BODIPY chromophore the Vis emission
can be tunable. As result, the emission of the fluorene is quenched and the obtained bichromophoric
dyes can be used as active media of sintonizable dye lasers, in which the pumping process can be,
performed both, in the UV or in the Vis region, getting always the bright Vis emission of BODIPY.
Moreover, the high “virtual” Stokes shift, that characterizes these bichromophoric dyes, makes
easier the application of BODIPYs in biological systems, since the emission region is far away from
the excitation region, avoiding background interferences in the detection of the fluorescence signal.
Vis exc
3
2
1
0
300
400
500
600
wavelength (nm)
Figure 1. UV-Vis absorption and fluorescence spectra (both under UV and Vis excitation) of dye 4 in c-hexane.
Bibliografía
[1] a) Loudet, A.; Burgess, K. Chem. Rev. 2007, 107, 4891-4932. b) Wood, T. E.; Thompson, A. Chem. Rev. 2007, 107,
1831-1861. c) Ulrich, G.; Ziessel, R.; Harriman, A. Angew. Chem., Int. Ed. 2008, 47, 1184-1201.
94
Organized media effect on the photochemical deoxygenation of rezorufin in the
presence of amines
G. V. Porcal, M. S. Altamirano; C. M. Previtali; S. G. Bertolotti
Departamento de Química. Universidad Nacional de Río Cuarto. Agencia Postal Nro 3 Río Cuarto, X5804ALH.
Argentina [email protected]
Resazurin (RZ) is a phenoxazin-3-one dye widely used for testing various biological materials.
The reduction of RZ to resorufin (RF) is the main reaction on which these tests are based. This
reaction takes place efficiently when RZ is irradiated in its visible band in the presence of amines
and it is highly dependent on the amine structure. The reaction is only effective in the presence of
tertiary amines, irradiation of RZ in the presence or primary or secondary aliphatic amines or for
aromatic amines does not lead to RF.
O
.
N
N
-
-
O
O
O
O
O
Na
Na+
O
+
Resorufin (RF)
Resazurin (RZ)
Scheme 1
The effect of different organized media on the photoreaction was investigated. In all cases the same
photoreaction was observed with the presence of a neat isosbestic point in the spectrum, indicating
that the reaction is unaltered by the presence of the organization. (Figure 1). The reaction was
carried out in water at pH 10, in direct micelles of cetyltrimethylammonium chloride (CTAC), in
reverse micelles of benzylhexadecyldimethylammonium chloride (BHDC) and lecithin
microemulsions (LEC).
Absorbance
1,5
Figure 1: Photolysis
of RZ in CTAC direct
micelles.
CTAC = 0.025 M,
Triethanolamine
(TEOHA) = 5.5x10-4 M,
irradiation at 620 nm.
irradiation
time (s)
0
60
120
300
600
1,0
0,5
0,0
450
600
750
The photoreaction was followed by
the decrease of RZ absorbance in the maximum, around 600λ /nm
620 nm in all systems. The singlet oxygen mediated photooxidation of dimethyl anthracene (DMA),
sensitized by methylene blue was used as actinometer.
95
Photoreaction quantum yields as a function of TEOHA concentration are shown in Figure 2. Since
the excited singlet lifetime is too short at TEOHA concentration used practically there is not
interaction of the amine with the dye in its excited singlet. Therefore, the most likely mechanism for
the photodeoxygenation is through the triplet state
The mechanism can be written as
RZ
0,125
ΦR
LEC
BHDC
0,050
S
RZ*
S
RZ*
T
S
RZ*
RZ
T
RZ*
0,100
0,075
hν
kd
T
RZ* + TEOHA
RZ*
RZ
(RZ= + TEOHA+.)
kT
0,025
0,000
0,000
0,002
0,004
0,006
(RZ= + TEOHA+.)
kb
(RZ= + TEOHA+.)
kR
RZ + TEOHA
0,008
[TEOHA] /M
Figure 2: reaction quantum yield as a function of [TEOHA]
RF + TEOHA
Φ R = ΦT
kT [TEOHA]
η
kT [TEOHA] + k d
concentration
Table 1. Photophysical and photochemical parameters for RZ
Medium
ΦT
τT /µs
kT
/107 M-1s-1
Φ∞R
η
H2O pH 9
0.08
40
6.2
0.036
0.45
SDS 0.02 M
0.08
40
2.0
0.036
CTAC 0.025 M
0.12
±0.01
70
0.5
0.19
1
BHDC 0.1 M
80
2.2
0.13
1
w =20
0.11
±0.02
LEC 0.05 M
0.22
5
18
0.04
0.19
w = 30
The results are shown in Table 1 and they are discussed in terms of the localization of the dye and
the TEOHA partition in the different systems studied.
96
Excited state interactions in biphenyl-tryptophan dyads
P. Bonancía,1 I. Vayá1,2, M. C. Jiménez, M. A. Miranda1
1
2
Departamento de Química/Instituto de Tecnología Química UPV-CSIC, Camino de Vera s/n, 46071 Valencia, Spain
Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPA - CNRS URA 2453, CEA/Saclay, 91191 Gif-sur-Yvette, France
Fluorescence and laser flash photolysis (LFP) measurements have been performed on two
pairs of diastereomeric dyads containing a biphenyl chromophore (FBP or FBPOH) and the methyl
ester of tryptophan (Trp), (Chart 1).
Chart 1
The fluorescence spectra were obtained upon excitation at 266 nm. Under these conditions,
the amount of light absorbed by each chromophore is shown in Table I. The most remarkable
difference between the two pairs of dyads is the nature of the emitting chromophore. Thus, for
FBPTrp, emission takes place from 1Trp (λem = 340 nm, Figure 1), while in the case of FBPOHTrp
deactivation occurs form a biphenyl singlet (λem = 334 nm, Figure 2). The main feature for all dyads
was a dramatic fluorescence quenching, which resulted to be stereoselective. Indeed, in the case of
FBPTrp, an exciplex emission was observed as a broad band between 380-500 nm, specially in the
case of the (R,S)- diastereomer. As shown in table II, the fluorescence lifetimes (τF) were clearly
shorter in the dyads than in the model compounds.
Table I. Percentage of light absorbed by each chromophore in the dyads at 266 nm.
FBPTrp
FBPOHTrp
Biphenyl
60
46
tryptophan
40
54
Table II. Maximum emission wavelength, singlet energy, fluorescence quantum yield and lifetime (measured at the
maxima) for the isolated chromophores and for the four dyads in MeCN at λexc = 266 nm.
(S)-FBP
(S)-FBPOH
(S)-TrpMe
(S,S)-FBPTrp
(R,S)-FBPTrp
(S,S)-FBPOHTrp
(S,R)-FBPOHTrp
λmax em (nm)
Es (Kcalmol-1)
φF
τF (ns)
310
334
337
340
340
334
334
99.0
91.5
94.0
94.0
94.0
92.0
92.0
0.21
0.21
0.30
0.04
0.02
0.11
0.05
1.7
2.0
6.3
0.9
0.9
1.2
0.5
97
Figure 1. Fluorescence spectra of (S)-FBP (
),
(S)-TrpMe (
), (S,S)-FBPTrp (
) and
(R,S)-FBPTrp (
). Conditions: deaerated
MeCN, λexc = 266 nm. The absorbance of the
samples was kept at 0.2 at the excitation
wavelength
Figure 2. Fluorescence spectra of (S)-FBPOH (
), (R)-TrpMe (
), (S,S)-FBPOHTrp (
) and
(S,R)-FBPOHTrp (
). Conditions: deaerated
MeCN, λexc = 266 nm. The absorbance of the
samples was kept at 0.2 at the excitation
wavelength,
0,08
∆OD/a.u.
∆A/a.u.
Upon LFP, FBPTrp exhibited the typical FBP triplet-triplet transient absorption spectrum, although
the signals were less intense than when FBP was directly excited under the same conditions (decays
monitored at 360 in Figure 3). A similar trend was observed for FBPOHTrp, but with the maximum
at 380 nm (Figure 4).
0,06
0,025
0,020
0,015
0,04
0,010
0,02
0,005
0,000
0,00
0
100
200
300
t/µs
Figure 3. Laser flash photolysis (λexc = 266
nm, λmon = 360 nm, deaerated MeCN) of (S)FBP(
), (S,S)-FBPTrp (
) and (R,S)FBPTrp (
).
0
10
20
Figure 4. Laser flash photolysis (λexc = 266 nm,
λmon = 380 nm, deaerated MeCN) of (S)FBPOH (
), (S,S)-FBPOHTrp (
) and
(S,R)-FBPOHTrp (
).
References:
[1] M. C. Jiménez, M. A Miranda, R. Tormos, I. Vayá Photochem. Photobiol. Sci., 2004, 3, 1038
[2] I. Vayá, M. C, Jiménez, M. A. Miranda, J. Phys. Chem. B, 2008, 111, 9363.
98
30
t (µs)
Specific and Selective Generation of Guanine Neutral Radical from Photolabile
Nucleoside Derivatives
S. Encinas1, C. Paris1, M. A. Miranda1, P. Kaloudis2, D. Vrantza2, R. Pérez-Ruiz2, T. Gimisis2
1
Departamento de Química/Instituto de Tecnología Química, Universidad Politécnica de Valencia
2
Organic Chemistry Laboratory, Department of Chemistry, University of Athens
Extensive research over the past years on oxidatively produced DNA damage has uncovered a
wealth of chemistry involving the sugar and base components of nucleosides, nucleotides, synthetic
oligonucleotides and natural DNA. [1] Of the four DNA bases, guanine (G) is the most easily
oxidized, its reduction potential being the lowest among the nucleobases. One electron oxidation of
the G moiety results in the formation of a wide variety of oxidatively generated damage (Scheme
1). [2] In this context, a variety of methods have been utilized for the abstraction of a single electron
from the guanine moiety. [3]
O
N
8
7
5
9
4
6
N
1 NH
N
N
-H
HOO
N
O2 , H+
2
3
N
O
O
N
N
N H2
R
N
N
NH2
N
NH 2
N
NH
N
R
R
O
N
NH 2
R
H 2O
-e
O
N
N
NH
N
HO
NH2
H
R
HOO
H
N
O
N
N
NH
NH 2
R
H 2N
H 2N
O
N
NH
R
H
N
HN
O
H 2O
O
NH
O
N
NH
R
H 2N
N
H
N
H
N
OH
C O2
R
H CONH 2
Scheme 1. Oxidatively generated damage in DNA through one-electron oxidized guanine.
The present study describes an alternative approach for the site specific and independent generation
of the guanine radical. We proposed the use of either N-hydroxypyrid-2(1H)-one or Nhydroxypyridine-2(1H)-thione as photolabile modifiers at the 6-position of 2’-deoxyguanosine or
guanosine (Scheme 2). Photolysis of the derivatized guanine moiety was expected to homolytically
cleave the N-O bond and afford the neutral guanine radical. Novel photolabile 6-[(1-oxido-2pyridinyl)oxo]- and 6-[1-oxidopyridin-2-yl]sulfanyl-6-deoxy- and 2’,6-dideoxy-guanosine
derivatives were synthesized and characterized.
Significant differences were found for the pyrid-2-one and pyridine-2-thione nucleoside derivatives.
99
hν
O
N
N
N
HO
N
N
O
X
X
N
N
NH2
N
HO
O
N
N
NH2
O
OH
OH
G(-H)
Scheme 2. Proposed photoinduced generation of G(-H)•.
We have recently evaluated the use of the N-hydroxypyridine-2(1H)-thione as a photolabile
modifier and we did observe products arised from G(-H)• formation. A rapid equilibrium of the
derivatives with the corresponding 6-[(1-oxidopyridin-2-yl)sulfanyl] analogues was assumed in
order to explain the photoproducts. The prevalent pyridine-N-oxide isomer could give
photosensitization of reactive oxygen species through triplet excited state generation. [4]
∆A, a.u.
∆ A, a.u.
0,10
0,05
0,00
0,05
0,00
300
0,10
0
400
500
200
600
λ, nm
t, µs
400
700
Figure 1. Transient absorption spectrum of G(-H)•. Inset: Decay trace of the signal.
On the other hand, it has been reported that the photochemistry of the pyrid-2-one moiety is much
simpler compared to its sulphur analogue. In fact, the generation of G(-H)• proceeds through
homolysis of the N-O bond. Formation of the neutral guanine radical was confirmed for the pyrid-2one derivatives through continuous photolysis product analysis, trapping studies, as well as by laser
flash photolysis experiments (Figure 1).
References
[1] C. J. Burrows, J. G. Muller Chem. Rev. 98 (1998) 1109; W. K. Pogozelski, T. D. Tullius Chem. Rev. 98 (1998)
1089.
[2] J. Cadet, T. Carell, L. Cellai, C. Chatgilialoglu, T. Gimisis, M. Miranda, P. O’Neill, J. L. Ravanat, M. Robert
Chimia 62 (2008) 742; J. Cadet, T. Douki, J. L. Ravanat Acc. Chem. Res. 41 (2008) 1075.
[3] J. Cadet, M. Berger, G. W. Buchko, P. C. Joshi, S. Raoul, J. L. Ravanat J. Am. Chem. Soc. 116 (1994) 7403; K.
Kino, I. Saito, H. Sugiyama J. Am. Chem. Soc. 120 (1998) 7373.
[4] D. Vrantza, P. Kaloudis, L. Leondiadis, T. Gimisis, G. C. Vougioukalakis, M. Orfanopoulos, D. Gasparutto, J.
Cadet, S. Encinas, C. Paris, M. A. Miranda Helv. Chim. Acta 89 (2006) 2371.
100
Compuestos Pseudopeptídicos Sintéticos como Modelos Supramoleculares
para el Estudio de Fármacos Fotoactivos
Francisco Galindo,1 M. Angeles Izquierdo,1 M. Isabel Burguete,1 Santiago V. Luis,1 Xavier J. Salom-Roig,2 Jean
Martínez,2 María C. Morant-Miñana,3 Miguel A. Miranda,4 Julia Pérez-Prieto3
1 Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Castellón; [email protected]
2 Inst. Biomolécules Max Mousseron (IBMM), UMR 5247, Synthèses Stéréosélectives, U. Montpellier II (Francia)
3
Departamento de Química Orgánica / ICMOL, Universidad de Valencia.
4
Departamento de Química / Instituto de Tecnología Química (UPV-CSIC), Universidad Politécnica de Valencia.
Existe un gran interés en la actualidad por el desarrollo de modelos sintéticos que imiten el
comportamiento de moléculas naturales de mayor complejidad (proteínas, ácidos nucleicos, etc) [1].
En este sentido, se han descrito numerosos compuestos con los requisitos estructurales mínimos
para el estudio de determinadas propiedades biológicas [2]. Por ejemplo, se han desarrollado
compuestos peptidomiméticos de bajo peso molecular capaces de autoasociarse de manera análoga
a como lo hacen grandes biomoléculas como los péptidos β-amiloides, lo cual ha permitido
profundizar en el conocimiento de la enfermedad de Alzheimer [3].
Otro grupo interesante de proteínas a estudiar con modelos sintéticos sencillos son las
proteínas de transporte, como la albúmina sérica humana. Dicha macromolécula es capaz de
asociarse con ligandos orgánicos, tales como fármacos, y transportarlos por el torrente sanguíneo
[4]. Se han descrito abundantes ejemplos de toxicidad causada por la combinación de luz y
fármacos antiinflamatorios no esteroides (AINEs), y a fecha de hoy existen numerosas evidencias
de la implicación de aminoácidos específicos dentro de dichas proteínas de transporte (Trp y Tyr
principalmente) [5]. Para el entendimiento de dichas reacciones fototóxicas, se ha hecho extensivo
uso de modelos sintéticos consistentes en conjugados de fármaco-aminoácido, utilizando la técnica
de fotólisis de destello láser (LFP) como principal herramienta analítica [6]. Las interacciones
estudiadas poseen, por tanto, un marcado carácter intramolecular.
En el presente trabajo se ha realizado una aproximación intermolecular a dicho estudio: por
un lado mediante la síntesis pseudopéptidos modelo (1-6, figura 1), capaces de interaccionar con
diversos AINEs (naproxeno y ácido tiaprófénico) y por otro lado mediante el estudio de las
interacciones supramoleculares gracias a espectroscopía de fluorescencia (estacionaria y resuelta en
el tiempo) y a LFP [7,8]. Se discutirá el efecto de la estructura de 1-6 sobre la desactivación de los
estados excitados (singlete y triplete) de los mencionados fármacos antiinflamatorios.
Figura 1. Modelos pseudopeptídicos sintéticos utilizados para el estudio de fármacos fotoactivos.
101
Por otro lado, se describirán los estudios recientemente llevados a cabo con moléculas
pseudopeptídicas de tipo macrocíclico, como la estructura 7 mostrada en la figura 2, capaces de
auto-organizarse para dar asociaciones fibrilares (y en última instancia organogeles) [9].
Figura 2. Macrociclo con propiedades autoasociativas, cuya interacción con naproxeno ha sido estudiada.
Se ha utilizado la fluorescencia de naproxeno como herramienta espectroscópica para
evaluar las interacciones entre dicho fármaco y las fibras formadas por 7 mediante autoensamblaje.
Se discutirá la posible relevancia de los agregados de pseudopéptidos macrocíclicos como modelos
de biomoléculas de mayor complejidad estructural [10].
References
[1] J. Eichler, Curr. Opin. Chem. Biol. 12 (2008) 707.
[2] J. A. Robinson, Acc. Chem. Res. 41 (2008) 41, 1278.
[3] T. J. Smith, C. I. Stains, S. C. Meyer, I. Gosh, J. Am. Chem. Soc. 128 (2006) 14456.
[4] J. Ghuman, P.A. Zunszain, I. Petitpas, A. A. Bhattacharya, M. Otagiri, S. Curry, J. Mol. Biol. 353 (2005) 38.
[5] (a) M. A. Miranda, Pure Appl. Chem. 73 (2001) 481; (b) M. C. Jiménez, M. A. Miranda, I. Vayá, J. Amer. Chem.
Soc. 127 (2005) 10134.
[6] (a) M. A. Miranda, A. Lahoz, R. Martínez-Máñez, F. Boscá, J. V. Castell, J. Pérez-Prieto, J. Am. Chem. Soc. 121
(1999) 11569; (b) M.C. Jimenez, U. Pischel, M.A. Miranda, J. Photochem. Photobiol. C: Photochem. Rev. 8 (2007)
128.
[7] X. J. Salom-Roig, J. Martínez, M. I. Burguete, F. Galindo, S. V. Luis, M. A. Miranda, M. C. Morant-Miñana, J.
Pérez-Prieto, Tetrahedron Lett. 00 (2009) 0000.
[8] M. I. Burguete, G. Fawaz, F. Galindo, M. A. Izquierdo, S. V. Luis, J. Martínez, X. J. Salom-Roig, Tetrahedron
(enviado).
[9] (a) B. Escuder, J. Becerril, M.I. Burguete, F. Galindo, R. Gavara, J. F. Miravet, S. V. Luis, G. Peris, Chem. Eur. J.
10 (2004) 3879; (b) M. I. Burguete, F. Galindo, R. Gavara, M. A. Izquierdo, J. C. Lima, S. V. Luis, A. J. Parola, F.
Pina, Langmuir 24 (2008) 9795.
[10] M. I. Burguete, M. A. Izquierdo, F. Galindo, S.V. Luis, Chem. Phys. Lett. 460 (2008) 503.
102
Photophysical study of a rosuvastatin photoproduct
Giacomo Nardi, Sara Montanaro, Virginie Lhiaubet-Vallet, Miguel Angel Miranda
Instituto de Tecnologia Quimica, UPV-CSIC, Universidad Politecnica de Valencia, Avenida de Los Naranjos, s/n,
46022, Valencia, Spain
Rosuvastatin calcium, a statin drug of second generation, is one of the most frequently prescribed
drugs worldwide [1,2]. This synthetic lipid-lowering agent inhibits 3-hydroxy-3-methylglutarylcoenzyme A (HMG-CoA) reductase, which is involved in cholesterol biosynthesis. Among the
adverse effects, clinical cases of cutaneous reactions have been reported for some statins and
associated with photosensitivity disorder.
Scheme 1: Structures and degradation condition of Rosuvastatin and its photoproduct.
It has previously been established that the knowledge of photophysical properties of drugs is
essential for a better understanding of the molecular mechanism responsible for their
photosensitizing side effects [3]. Photochemistry of rosuvastatin has been previously reported in the
literature [4]. As regards the photolability of the drug, the photoproducts might be envisaged as
potential photosensitizing agents. In this work, we present the photophysical studies of one
photodegradation products of rosuvastatin (Scheme 1).
Singlet state properties were determined by steady state fluorescence. In phosphate buffer solution,
an emission centered at 376 nm and with a quantum yield of 0,014 was obtained. A singlet state
energy of 85 kcal/mol was determined from the 0-0 transition.
Laser flash photolysis showed a T-T transition at 400 nm (Figure 1), that was efficiently quenched
by O2 and β-carotene. Interaction with biological building blocks has also been considered. Ability
of rosuvastatin photoproduct to generate singlet oxygen was assessed by EPR using TEMP as spin
trap (conversion of TEMP to the stable free radical TEMPO).
103
Figure 1: Transient absorption spectrum of rosuvastatin photoproduct after laser excitation at 308 nm. Insert: Decay
monitored at 400 nm
In summary, the photoproduct arising from rosuvastatin is in turn photoactive. It generates the
excited triplet state, whose quenching by oxygen leads to singlet oxygen. This is relevant in
connection with the photobiological properties of the parent drug.
References
[1] E.S.Istvan, J.Deisenhofer, Science, 292 (2001) 1160-1164
[2] http://www.rxlist.com
[3] S. Montanaro, V. Lhiaubet-Vallet, M.R. Iesce, L. Previtera, M.A. Miranda, Chem. Res. Toxicol. 22 (2009) 173-178.
[4] A.Astarita, M.DellaGreca, M.R.Iesce, S.Montanaro, L.Previtera, F.Temussi, J.Photochem.Photobiol. A, 187, (2007)
263-268.
104
Photophysical and Photochemical Study of Cinacalcet
E. Nuin, M.C. Jiménez, I. Andreu, M.A. Miranda
Departamento de Química-Instituto de Tecnología Química UPV-CSIC. Universidad Politécnica de Valencia,
Avenida de los Naranjos s/n, 46022, Valencia (Spain)
Cinacalcet (CIN, Fig. 1), is a drug used for the treatment of hyperparathyroidism in patients with
chronic renal failure in dialysis. This drug acts as a calcimimetic by allosteric activation of the
calcium-sensing receptor on the surface of the parathyroid cell [1, 2].
H
N
F
F
F
Figure 1. Structure of Cinacalcet
Cinacalcet contains two chromophores, a naphthalene moiety and a trifluoromethyl aromatic unit.
Hence, this drug could in principle exhibit the photophysical and photochemical properties of both
components. In this connection, the main goal of the present study has been to perform a systematic
characterization of the excited state behaviour of CIN.
As the majority of drugs, CIN interacts with proteins such as human serum albumin (HSA), wich is
the most abundant plasma protein. Therefore, in the present work an attempt has been made to obtain
relevant information about binding of cinacalcet to HSA using fluorescence and laser flash
photolysis. Furthermore, as CIN contains a chiral center, it exists in the two enantiomeric forms; the
pharmacological activity is attributed to the (R)- isomer. Thus, in the presence of proteins it would
be feasible to observe some stereodifferentiation in the photobehaviour of CIN.
The absorption spectrum of this drug reflects the contribution of the absorption spectra of its two
chromophoric units. The band that appears at longer wavelength belongs to the naphthalene moiety
that reaches up to 300 nm. This band corresponds to the S0-S1 transition. The fluorescence spectrum
(λexc= 290 nm) of CIN showed an emission band with maximum at ca. 320 nm.
Laser flash photolysis experiments (λexc= 308 nm) revealed formation of the naphthalene-like triplet
excited state with a maximum at 415 nm. This transient was quenched by oxygen, which leads to the
formation of singlet oxygen.
In summary, Cinacalcet is a photoactive compound, whose behaviour is mainly associated with the
naphthalene excited states. The obtained results are discussed in connection with possible
phototoxicity of this drug.
References
[1] W. L. St. Peter, L. Qi, L. Jiannong, M. Persky, K. Nieman, Ch. Arko, G. A. Block. Clinical Journal of the American
Society of Nephrology. 2009, 4, 354-360.
[2] M. Meola, I. Petrucci, G. Barsotti. Nephrology, Dialysis, Transplantation. 2009, 24, 982-989.
105
Laser Flash Photolysis Studies on Ketoprofen Conjugates of
α-Amino-Cholesterol
F. Palumbo1,2, I.Andreu1, M.S.Sinicropi2, ,M.A. Miranda1
Instituto de Tecnologia Quimica UPV-CSIC, Universidad Politecnica de Valencia, Avenidade los Naranjos s/n,
Apdo 22012, 46071, Valencia, Spain
2
Facoltà di Farmacia e Scienze della Nutrizione e della Salute,Università della Calabria, edificio Polifunzionale,
Arcavacata di Rende 87032 (Cs), Italy
1
Cell membrane lipids are important targets of photodynamic attack. Cholesterol (Ch) is one
of the most important lipid components in eukaryotic cells and is a major target for oxidative
degradation, a process which can result in potentially pathologic consequences. This oxidative
damage can occur by two mechanisms: Type I (via free radicals) and Type II (mediated by 1O2).
This process can be promoted by UVA-irradiation in combination with photosensitizing agents [1].
Ketoprofen (Kp) is among the substances that show photosensitizing potential; it is a
benzophenone(Bz)-derived non-steroidal anti-inflammatory drug [2]. In this context, we have
recently found that the nature of the involved excited triplet states has a strong influence on the
photobehavior of cholesterol-diaryl ketone dyads. Thus Kp-α-Ch dyads are appropriate model
systems to generate biradicals by intramolecular hydrogen abstraction from the 7-allyl Ch position;
the first step in Type I Ch oxidation [3]. By contrast, dyads containing tiaprofenic acid and Ch are
unreactive via hydrogen abstraction but, on the other hand, they are suitable models for
investigation of the purely Type II process [4].
In the present work, ketoprofen conjugates of α-amino-cholesterol (α-NH-Ch-(S)-Kp and αNH-Ch-(S)-Kp) have been synthesized from β-Ch and (R) or (S) Kp (via amide bond), as more rigid
models to study the mechanism of Ch oxidation photosensitized by drugs. Actually, we have found
that these models may be involved in both mechanisms, Type I and Type II.
Figure 1. Structure of dyads
Laser flash photolysis experiments were done for all dyads ( exc = 355 nm) using NHcyclohexyl- (S)-Kp as reference. The transient absorption spectra obtained upon 355 nm excitation
of α-NH-Ch-(S)-Kp and α-NH-Ch-(S)-Kp 20 ns after the laser pulse corresponded to the
combination of two species: an earlier intermediate assigned to the triplet-triplet absorption with a
maximum ca. 525 nm, and a biradical showing typical bands at ca. 545 nm. Dyad α-NH-
106
cholesterol-(S)-ketoprofen showed a much more significant contribution of the biradical.
B)
A)
α-NH-Ch-(R)-Kp
α-NH-Ch-(S)-Kp
15000
1,0
α-NH-Ch-(R)-Kp
α-NH-Ch-(S)-Kp
0,8
0,6
∆A
∆A
10000
0,4
5000
0,2
0,0
0
350
400
450
500
λ (nm)
550
600
650
700
0
2
4
6
8
time (µs)
Figure 2. A) Transient absorption spectra obtained ca. 0.2 µs after laser pulse (355 nm) for α-NH-Ch-(R)-Kp and α-NHCh-(S)-Kp. B) Decays of the transients generated from α-NH-Ch-(R)-Kp and α-NH-Ch-(S)-Kp, monitored at 525 nm.
Kinetic analysis of the triplet decays, using a biexponential function, led to determination of
the triplet and biradical lifetimes. The triplet lifetimes were very short (30 ns and 0.5 µs for α-NHCh-(S)-Kp and α-NH-Ch-(R)-Kp, respectively). The generated biradicals were much longer-lived
(0.5 µs for α-NH-Ch-(S)-Kp and 1.6 µs for α-NH-Ch-(R)-Kp). The rate constants for intramolecular
H-abstraction from the C-7 allylic position were 3.3 × 107 s-1 for dyad containing (S)-Kp versus 1.4
× 106 s-1 for dyad containing (R)-Kp.
The obtained results clearly show that these dyads exhibit an important stereodifferentiation
in the intramolecular hydrogen abstraction process.
References
[1] A.W.Girotti, Antioxid. Redox Signal., 2004, 6, 301-310.
[2] F.Bosca and M.A.Miranda, J.Photochem. Photobiol., B: Biol, 1998, 43, 1-26.
[3] I.Andreu, F.Boscà, L.Sanchez, I.M.Morera, P.Camps and M.A.Miranda Organic Letters, 2006, 8, 4597-4600.
[4] I.Andreu, F.Bosca, L.Sanchez, I.M.Morera, P.Camps and M.A.Miranda, Org. Biomol. Chem., 2008, 6, 860-867.
107
FLUORESCENT CHOLIC ACID DERIVATIVES AS PROBES FOR THE
PHOTOPHYSICAL CHARACTERIZATION OF BILE ACID AGGREGATES
Miguel Gómez, M. Luisa Marin, Miguel A. Miranda
Instituto de Tecnología Química-Departamento de Química (CSIC-UPV), Avda de los Naranjos s/n, E-46022, Valencia,
Spain.
Bile acids are steroids with a cis fusion between rings A and B. This fact, together with the
hydroxyl groups in the α face and the acid moiety in the lateral chain, makes these molecules
amphiphilic (see Figure 1 for the chemical structure of cholic acid, a representative member of the
bile acids family) [1].
β face
OH
OH
O
OH
OH
α face
Figure 1
It means that the α face (concave side) is hydrophilic whereas the β face (convex) is hydrophobic
[2]. For this reason they form aggregates in solution and behave as micelles (Figure 2) [1]. In fact,
natural bile acids are responsible for biological functions such as enterohepatic circulation.
Figure 2. Representation of bile acids micelles.
It is assumed that bile salt aggregates are consistent with the primary/secondary aggregate model
[3],[4].
108
Cholic acid concentration ( mM)
0-5
5-20
20-50
Aggregate state
Solution
Primary aggregate
Secondary aggregate
Table 1. Relationship between cholic acid concentration and state of aggregation.
We have synthesized 3α-dansyl cholic acid derivative (3α-Dns-ChA) to characterize the cholic acid
aggregates on the basis of fluorescence changes employing an intramolecular approach.
OH
HN
COOH
OH
SO2
(H3C)2N
Figure 3. Chemical structure of 3α-dansyl cholic acid derivative
The fluorescence spectra of 3α-dansyl cholic acid in water (λexc = 327 nm) shows a broad maximum
at 553 nm. Changes in the fluorescence intensity have been registered upon increasing amounts of
non-fluorescent cholic acid (Figure 4). This graph shows three different regions corresponding to
the concentrations of solution, primary aggregate and secondary aggregate. As a control, the same
experiment has been performed on the increasing fluorescence emission intensity of dansylglycine
upon addition of cholic acid.
Figure 4. Relationship between emission intensity (at 553 nm) and concentration of cholic acid for 3α- Dansyl-cholic
acid derivative (circles) and Dansylglycine (squares).
References
[1] M. Pattabiraman, L. S. Kaanumalle, and V. Ramamurthy, Langmuir 2006, 22, 2185-2192.
[2] V.H. Soto Tellini, A. Jover, L. Galantini, N.V. Pavel, F. Mejide, and J. Vazquez Tato, J. Phys. Chem. B 2006, 110,
13679-13681.
[3] C. Bohne, Langmuir 2006, 22, 9100-9111.
[4] O. Rinco, M.-C. Nolet, R. Ovans and C. Bohne, Photochem. Photobiol. Sci., 2003, 2, 1140-1151.
109
Síntesis y caracterización fotofísica de porficenos con diferentes sustituyentes
arilo
M. Camarasa, I. Burgués, D. Sánchez-García, S. Nonell
Grup d’Enginyeria Molecular, Institut Químic de Sarrià, Universitat Ramon Llull,
Vía Augusta 390, 08017-Barcelona, España
[email protected]
La terapia fotodinámica del cáncer es una modalidad terapéutica que consiste en la aplicación de
compuestos fotosensibilizadores que se acumulan preferentemente en los tejidos neoplásicos. La
subsiguiente irradiación del área tumoral con luz visible genera especies reactivas de oxigeno
(ROS), cuya elevada citotoxicidad produce selectivamente la muerte celular de las células malignas.
El desarrollo de fotosensibilizadores para la localización de tumores y su tratamiento es un campo
de investigación muy activo en la actualidad [1].
La primera generación de fotosensibilizadores la constituyeron porfirinas de origen natural. Tres de
los cinco fármacos actualmente aprobados para su uso en terapia fotodinámica pertenecen a esta
familia: el porfímero sódico, el ácido aminolevúlinico – en realidad un profármaco del agente
fotoactivo protoporfirina IX, y su éster metílico. La necesidad de mejorar las propiedades
fotoquímicas y farmacológicas de estos fármacos ha generado los llamados fotosensibilizadores de
segunda generación, entre los cuales se encuentran los porficenos en los que trabaja nuestro grupo
de investigación. Los porficenos son isómeros de las porfirinas que presentan un elevado potencial
para terapia fotodinámica del cáncer debido a sus mejores propiedades ópticas y fotofísicas, así
como su elevada actividad fotodinámica [2].
Otra familia de fotosensibilizadores de segunda generación la constituyen las clorinas o
dihidroporfirinas. La reducción parcial del anillo de porfirina conlleva un aumento significativo del
coeficiente de absorción en el rojo debido a su menor simetría, lo que permite reducir la dosis de
fármaco para obtener el mismo efecto terapéutico. En el año 2001 la Unión Europea aprobó el uso
de la temoporfina, 5,10,15,20-tetrakis(m-hidroxifenil)clorina (Foscan ®), para el tratamiento
paliativo del cáncer de cuello y de cabeza.
La similitud entre la estructura de la temoporfina y la del tetrafenilporficeno estudiado ampliamente
por nuestro grupo nos hizo plantear la obtención del 2,7,12,17-tetrakis(m-hidroxifenil)porficeno y
sus alcoxiderivados. Para ello se ha desarrollado una ruta sintética basada en nuestro reciente
descubrimiento de una síntesis one-pot de 4,4’-diaril-2,2’-bipirroles [3]. Las propiedades fotofísicas
de estos nuevos compuestos son adecuadas para su uso en terapia fotodinámica.
References
[1] R Bonnet, Chemical Aspects of Photodynamic Therapy. (2000), Gordon and Breach Science Publishers.
[2] J.C. Stockert, M. Cañete, A. Juarranz, A. Villanueva, R.W. Horobin, J.I. Borrell, J. Teixidó, S. Nonell. Curr. Med.
Chem. 14 (2007) 997-1026.
[3] D. Sánchez, José I. Borrell, S. Nonell, B. Org. Lett. 11 (2009) 77-79.
110
Solvent Effects on the Photophysics of Naphthoxazole Derivatives
Antonio L. Zanocco1, Manuel Curitol1, Xavier Ragàs2 and Santi Nonell2,
1
Universidad de Chile, Facultad de Ciencias Químicas y Farmacéuticas, Departamento de Química Orgánica y
Fisicoquímica, Casilla 233, Santiago - 1, Santiago, Chile.
2
Grup d’Enginyeria Molecular, Institut Químic de Sarrià, Universitat Ramon Llull, Via Augusta 390, E-08017,
Barcelona, España
The photophysical properties of benzoxazole derivatives have received considerable attention from
a basic perspective and for the development of molecules with suitable properties for specific
applications. The highly favourable photophysical properties of this type of heterocyclic
compounds, such as high fluorescence quantum yield, photostability, as well as the easy tuning of
their photophysical properties by changing a substituent at position 2 in the benzoxazole ring,
endow these compounds with high potential as new fluorophores. Benzoxazole derivatives have
been used as organic plastic scintillators [1] and optical fibre sensors [2]. Moreover, some
derivatives are biologically active, showing cytotoxic [3], antimicrobial [4] and genotoxic [5]
activity, inhibiting both eukaryotic DNA topoisomerase I and II. They have also been used as
fluorescent probes to determine glutathione and cysteine [6] in biological samples as well as metal
cations [7]. Benzoxazol-5-yl-alanine derivatives containing an aromatic hydrocarbon substituent in
position 2 have been used as fluorescence markers in biological systems even in the presence of
tryptophan [8]. Benzoxazole derivatives are also efficient probes for monitoring and exploring the
properties of micelles and the hydrophobic interactions in human serum albumin, as well as
photoactive agents in polymeric nonlinear optical materials with large hyperpolarizability values
[9], and in a promising and convenient fluorescent molecular sensing strategy based on a dual
“lock–key” mechanism [10]. Furthermore, polybenzoxazole derivatives have been proposed as
positive photosensitive precursors for microelectronic applications, for application in
electroluminescent devices, and as very promising luminophores for the generation of linearly
polarized light by using the auto-organization capability of liquid-crystalline media [11]. In spite of
the wide range of basic and innovative research, to the best of our knowledge no reports exist on the
photophysics and/or the photochemistry of compounds with the oxazole heterocycle condensed to
extended aromatic systems. Building on the fact that the benzoxazole excited states have substantial
charge-transfer character, we hypothesized that naphtho- for benzo-ring substitution could
substantially affect the photophysical properties of the aryloxazoles. In this work we study the
solvent effect on absorptive and emissive characteristics of a series of naphthoxazole derivatives
(Figure 1).
H3C
N
CH3
N
O
N
N
O
MNOX
O
N
O
PHNOX
DMAPHNOX
LPHNOX
Figure 1. Molecular structures of studied compounds
111
The UV-Vis spectra of the naphthoxazole derivatives were measured at room temperature in
a large set of solvents of different polarity and proton donating ability. The absorption spectra show
an intense and broad low-energy band in the range 310 – 390 nm. The absorption maxima are
almost insensitive to solvent polarity. Spectra calculations employing DFT formalism (B3LYP6311g+ for structure optimization and ZINDO-S, CIS and TD-SCF for vertical Franck-Condon
transitions) performed best at the TD-SCF (DFT 6311+g) level of theory, yielding vertical
transitions in good agreement with the experimental values. In addition, irrespective of the method
employed for calculations, analysis of the molecular orbitals indicated a π-π* transition in all cases.
On the contrary, the position of the fluorescence maximum was red-shifted being upon increasing
the solvent polarity behaviour, indicating that the fluorescent state is highly polar with an important
charge transfer character. A deeper rationalization of this effect was obtained from the analysis of
the fluorescence maximum dependence on microscopic solvent parameters by employing LSER
and/or TLSER equations. Thus, the energy of the fluorescent state decreased in solvents capable of
stabilizing charges and dipoles, as well as in strong HBD solvents, indicating that an important
charge separation occurs in the excited state. The dipole moment change between excited and
ground states, calculated from the Lippert–Mataga relationship, ranged from 6 to 11 Debyes,
consistent with a charge-transfer nature of the first excited singlet state. Fluorescence quantum
yields of studied compounds, measured by the comparative method described by Eaton and Demas
[12] using quinine sulphate in 0.1N sulfuric acid (ΦF = 0.55) as reference, were close to 1, except
for PHNOX for with the observed values were ca. 0.5. For all naphthoxazole derivatives, ΦF was
nearly independent of the solvent polarity. The fluorescence lifetime for these compounds were in
the range 1-3 ns in the solvent set employed, increasing slightly with solvent polarity. On the other
hand the photo-stability of naphthoxazole derivatives was evaluated by observing its consumption
in long-term photolysis experiments using gas-liquid chromatography. The data obtained, in the
presence and the absence of oxygen, shows that the napthoxazoles studied in this work are
photostable under the experimental conditions employed.
In summary, the properties evaluated for naphthoxazoles, suggest that these compounds are
valuable candidates for technological applications as dyes, quantum counters, or fluorescent probes
Acknowledgements
Financial support from FONDECYT (grants 1050796, 1080410 and 7060251) is gratefully acknowledged.
References
[1] A. Pladalmau, Journal of Organic Chemistry 60 (1995) 5468-73.
[2] Y. Wang, W.H. Liu, K.M. Wang, G.L. Shen, R.Q. Yu, Fresenius J. Anal. Chem. 361 (1998) 827-27.
[3] C.M. Lozano, O. Cox, M.M. Muir, J.D. Morales, J.L. Rodriguez-Caban, P.E. Vivas-Mejia, F.A. Gonzalez, Inorg.
Chim. Acta 271 (1998) 137-44.
[4] E.A. Sener, O.T. Arpaci, I. Yalcin, N. Altanlar, Il Farmaco 55 (2000) 397-405.
[5] E. Oksuzoglu, O. Temiz-Arpaci, B. Tekiner-Gulbas, H. Eroglu, G. Sen, S. Alper, I. Yildiz, N. Diril, E. Aki-Sener,
I. Yalcin, Med. Chem. Res. 16 (2007) 1-14.
[6] S.C. Liang, H. Wang, Z.M. Zhang, H.S. Zhang, Anal. Bioanal. Chem. 381 (2005) 1095-100
[7] M. Milewska, A. Skwierawska, K. Guzow, D. Smigiel, W. Wiczk, Inorg. Chem. Commun. 8 (2005) 947-50.
[8] K. Guzow, M. Szabelski, J. Malicka, J. Karolczak, W. Wiczk, Tetrahedron 58 (2002) 2201-09.
[9] K.H. Park, J.T. Lim, S. Song, Y.S. Lee, C.J. Lee, N. Kim, Reactive & Functional Polymers 40 (1999) 177-84.
[10] J.B. Wang, X.H. Qian, J.H. Qian, Y.F. Xu, Chemistry-a European Journal 13 (2007) 7543-52.
[11] R. Gimenez, L. Oriol, M. Pinol, J.L. Serrano, A.I. Vinuales, T. Fisher, J. Stumpe, Helvetica Chimica Acta 89
(2006) 304-19.
[12] D.F. Eaton, Pure and Applied Chemistry 60 (1988) 1107-14.
112
Síntesis y caracterización fotofísica de porficenos catiónicos.
R. Ruiz, D.Sánchez-García, S. Nonell
España
La terapia fotodinámica (PDT) es uno de los diversos tratamientos en medicina que utiliza la luz
con fines curativos. Esta terapia requiere la presencia de un fotosensibilizador que, en presencia de
oxígeno y luz, es capaz de producir especies de oxígeno altamente reactivas (ROS) que inducen la
muerte celular. La modificación de las propiedades fisicoquímicas de los fotosensibilizadores
representa una aproximación importante hacia la mejora de su selectividad. Los porficenos,
isómeros estructurales de las porfirinas con mejores propiedades ópticas, tienen elevada actividad
como agentes fotodinámicos. En este trabajo se ha sintetizado y caracterizado las propiedades
fotofísicas de porficenos catiónicos solubles en agua ideales para la administración por vía
parenteral. Son varias las posibles aplicaciones de dichos compuestos: por un lado, es conocida la
concentración de cationes lipofílicos en las mitocondrias celulares en respuesta a los potenciales
transmembrana negativos de éstas, lo cual convierte a los compuestos de estudio en potenciales hits
para targetting subcelular en PDT antitumoral [1-2]; por otro lado, se trata de un nuevo
fotosensibilizador para tratamiento de infecciones bacterianas por efecto de la inactivación
fotodinámica.
La síntesis del porficeno sigue el procedimiento descrito en [3] según el cual el bipirrol intermedio
se consigue en una reacción one-pot seguida del acoplamiento de McMurry. El porficeno así
obtenido es bromado y posteriormente convertido en la sal catiónica correspondiente.
References
[1] R. Hudson, R.W. Boyle. J. Porphyrins Phthalocyanines 8 (2004) 954-975
[2] R. Hilf. J. Bioenerg Biomembr 39 (2007) 85-89
[3] D.Sánchez-García, J.I. Borrell, S. Nonell. Org.Lett. 11 (2009) 77-79
113
Liposomas marcados con folato como sistemas de vehiculización para terapia
fotodinámica dirigida
M. García-Díaz1, S. Nonell1, A. Casadó2, M. Mora2, M. L. Sagristá2
1
España
2
Departament de Bioquímica i Biología Molecular, Facultat de Biología, Universitat de Barcelona, Avinguda Diagonal
645, 08028-Barcelona, España.
[email protected]
Uno de los requisitos de la terapia fotodinámica del cáncer es la internalización del
fotosensibilizador en las células tumorales, que junto a la irradiación a una determinada longitud de
onda produce especies reactivas de oxígeno que causan la muerte celular. Actualmente, una de las
principales líneas de investigación en terapia fotodinámica es el desarrollo de sistemas de
vehiculización que dirijan los fotosensibilizadores hacia aquellas células tumorales y por tanto, que
minimicen el riesgo y amplificación de los efectos secundarios provocados por el daño causado al
tejido sano [1]. Los liposomas, como vehículos de fármacos, poseen importantes características
como la capacidad de encapsular moléculas tanto hidrofóbicas como hidrofílicas sin pérdida o
alteración de su actividad, una acumulación preferencial en tumores sólidos, un sistema de
liberación controlada y la facilidad de derivatización con moléculas reconocidas específicamente
por componentes de la superficie celular [2,3]. Las células epiteliales de algunos tipos de tumores
expresan elevados niveles de receptores folato, por lo que la conjugación de los liposomas con
ácido fólico permite un nuevo enfoque para la internalización selectiva de los fotosensibilizadores
[4]. Así, se utilizó tetrafenilporfirina de zinc (ZnTPP) como fotosensibilizador modelo para su
encapsulación en liposomas sin marcar de POPC/OOPS (9:1) y liposomas conjugados con folato en
cuya superficie se incorporó un 0.1% molar de folato-PEG-DSPE. La estabilidad de la formulación
y las propiedades fotofísicas del fotosensibilizador permanecieron inalteradas ante la presencia del
conjugado de folato en la superficie liposomal. Las células HeLa (células tumorales que
sobreexpresan el receptor folato) tratadas con ambos tipos de liposomas mostraron una
internalización preferencial de los liposomas marcados con folato. Dicha selectividad fue totalmente
inhibida en presencia de un exceso de ácido fólico libre en el medio de cultivo.
References
[1] .D. K. Chatterjee, L. S. Fong, Y. Zhang, Adv. Drug. Deliv. 60 (2008), 1627-1637.
[2] A. Derycke, P. de Witte, Adv. Drug. Deliv. (2004) 56, 17-30.
[3] T. L. Andresen, S. S. Jensen, K. Jørgensen, Progr. Lipid Res. 44 (2005), 68-97.
[4] A. R. Hilgenbrink, P. S. Low, J. Pharm. Sci. 94 (2005), 2135-2146.
114
Excimeros y transferencia de energía intramolecular en disoluciones de
copolímeros de N-vinil carbazole/vinil tert-butil benzoato de distinta
composición molar
Thais Carmona, Natali Fernández-Peña, M. Pilar Tarazona, Enrique Saiz and Francisco Mendicuti
Departamento de Química Física, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
El poli(N-vinil carbazol) (PVCz), en uno de los polímeros de tipo vinílico mas interesantes y
fotofisicamente más estudiados debido fundamentalmente a su capacidad fotoconductora [1-4]. La
razón hay que buscarla en que procesos fotofísicos como la formación de excímeros y la
transferencia de energía de excitación a lo largo de la cadena influyen de manera notoria en esa
capacidad fotoconductora. La transferencia de energía (ET) a lo largo de la cadena del polímero
favorece la fotoconducción, simultáneamente esa transferencia de energía es una forma de poblar
los excímeros. De manera que estos normalmente pueden actúan como “trampas” en el proceso de
transferencia. Cualquier parámetro que influya en la cuantía de ambos procesos lo hará en su
capacidad fotoconductora. Uno de esos parámetros es la concentración local de cromóforos que se
puede variar de forma sencilla.
En este trabajo se ha estudiado la formación de excímeros y la transferencia de energía
intramolecular en los homopolímeros PVCz y poli(vinil tert-butil benzoato) (PVtBBz), así como
copolímeros de N-vinil carbazol y vinil tert-butil benzoato de diferente composición molar en
disolución diluida de varios disolventes fluidos y en una matriz sólida de PMMA. Para ello se
utilizaron técnicas de fluorescencia en estado estacionario y de resolución temporal. Se obtuvieron
diferentes parámetros relacionados con la cuantía de ambos procesos mediante simulaciones de
dinámica molecular en oligómeros iso- y sindiotácticos de PVCz de 48 unidades de carbazol, CH3(ACH2)48-H, y en fragmentos de copolímeros del tipo CH3-(ACH2)6 –(BCH2)n-(ACH2)6-H donde A=
-CHCz-, B = -CHtBBz-CH2- y n = 1-5.
El análisis elemental de los copolímeros permitió obtener razones de reactividad de 1.5 y 0.7 para
los mónomeros VCz y VtBBz respectivamente. La excitación del grupo Cz (294 nm) en los
diferentes disolventes fluidos revelan una banda monomérica centrada a unos 350 nm un
ensanchamiento hacia el rojo debido a la emisión de distintos excímeros intramoleculares.
3.0
Fluorescence Intensity (a.u.)
2.5
ID/IM 2.0
1.5
1.0
C7
C6
0.5
0.0
0
C5
10 20 30 40 88 90
<n1>
C4
C3
C2
EtCz
340 360 380 400 420 440 460 480 500
λ (nm.)
Figura 1. Espectros de emisión del PVCz y de diferentes copolímeros (C#) excitando a 294 nm en tolueno a 25ºC.
Variación de la relación IM/IE con la longitud de secuencia promedio de unidades Cz (<n1>).
115
La cantidad de excímeros depende de la naturaleza del disolvente y de la composición del
copolímero. Independientemente del disolvente usado la cantidad de excímeros aumenta de manera
monótona con la longitud de secuencia promedio de grupos Cz, <n1>, para los copolímeros con
fracción molar de Cz, F1 ≤ 0.9, para luego mantenerse constante para valores mayores (Fig. 1).
Espectros de los copolímeros en la matriz sólida de PMMA indican menor presencia de excímeros
intramoleculares como consecuencia de la restricción en la dinámica de la cadena. Los resultados
teóricos hacen como principales responsables de la formación de excímeros a las interacciones entre
cromóforos de Cz corroborando los resultados experimentales. Los espectros de emisión excitando
al grupo tBBz demuestran que una directa excitación de Bz es seguida de una transferencia de
energía altamente eficiente hacia los grupos Cz.
10
5
8
L s, nm
2
10 Λs , cm s
-1
4
6
5
3
4
2
1
λ ex c=294 n m; λem=35 0 nm
2
λ exc =2 94 nm; λ em =35 0 n m
λ ex c=294 n m; λem=37 5 nm
0
λ exc =2 94 nm; λ em =37 5 n m
0
0
20
40
60
<n 1 >>
<n
1
80
996
0
200
400
600
800
9960
<n 1 >
<n
1>
Figura 2. Variación en la velocidad del proceso de transferencia de energía entre grupos Cz, Λm (cms-1) (izquierda) y
longitud promedio de transferencia, Ls (nm) (derecha) con la longitud de secuencia promedio de grupos Cz, <n1>
obtenidas por medidas de “quenching” de fluorescencia bajo excitación de 294 nm seleccionando la emisión a 350 nm
() y 375 nm ().
El estudio de la transferencia de energía de excitación se realizó mediante experimentos de
despolarización de fluorescencia de los copolímeros y compuestos modelo en un matriz sólida de
PMMA, así como de apagamiento de fluorescencia (quenching) en disoluciones diluidas de THF a
25ºC utilizando CCl4 como desactivador. Se obtuvieron parámetros relacionado con la transferencia
de energía como, la anisotropía y el ángulo de desplazamiento de los momentos de la transición de
absorción y emisión relativo al del compuesto modelo ECz, la velocidad del proceso de
transferencia de energía entre grupos Cz, Λm, y longitud promedio de esa transferencia, Ls. Los
resultados indican un aumento acentuado en la eficiencia con <n1> hasta un determinado valor para
luego estabilizarse. Teóricamente se obtuvieron parámetros relacionados con la eficiencia en
transferencia Cz-Cz como, la probabilidad P(R) de encontrar el centro de masas de dos Cz
adyacentes dentro de una esfera de radio igual R0 (radio de Förster), así como el producto κ2 P(R).
Agradecimientos. Los autores agradecen la financiación al MEC (proyecto CTQ2008-03149) y a la
CAM (proyecto S-055/MAT/0227). Natalí Fernández-Peña agradece una beca del MAEC-AECID.
Referencias
[1] P. Strohriegl, J.V. Grazulevicius, en Handbook of Organic Conductive Molecules and Polymers, editado por H.S.
Nalwa, Wiley: Chichester, Cap.11, 1997.
[2] K.Y. Law, Chem. Rev. 93 (1993) 449.
[3] J. Guillet, Polymer Photophysics and Photochemistry: An Introduction to the study of Photoprocesses in
Macromolecules, Cambridge University Press, Cambridge, New York, Cap. 13 1985.
[4] R. Solaro, G. Galli, A. Ledwith, E. Chiellini, en Polymer Photophysics: Luminescence, Energy Migration and
Molecular Motion in Synthetic Polymers; editado por D. Phillips, D., Chapman and Hall, New York, cap 8, 1985
116
GROUND AND EXCITED STATE PROPERTIES OF LEVOSIMENDAN IN
SOLUTION AND IN CHEMICAL AND BIOLOGICAL NANOCAVITIES
Boiko Cohen,1 Juan Angel Organero,1 Luis Rodrigues Padial 2, Lucia Santos Peinado1, Ruxandra Gref 3 and
Abderrazzak Douhal1*
1
Departamento de Química Física, Sección de Químicas, Facultad del Medio Ambiente, UCLM, 45071 Toledo, Spain
Servicios de Cardiologia, Hosp. Virgen de la Salud, Avenida Barber 30, 45004, Toledo, Spain
3
Université de Paris-Sud, 5, rue Jean-Baptiste Clément, 92296 Chatenay-Malabry, France
E-mail: [email protected]; [email protected]
2
These report accounts for the effect of the environment (pH, nanocaging, viscosity and
polarity) on the ground and excited state properties of the cardio-vascular drug Levosimendan
Figure 1. Time-resolved femtosecond transient absorption spectra of Levosimendan in pH7 aqueous solution
(LSM). We have studied the femtosecond transient absorption (TA) of LSM in buffered aqueous
solutions at pH 3, 7 and 11. Recently, we have reported on the ultrafast dynamics of other drugs in
water solution and in caging media [1-5]. Figure 1 shows a 3-D evolution of the excited LSM in pH
7 buffer. We find two bands corresponding to two excited state species. The band at 530 nm has a
Figure 2. Time-resolved femtosecond transient absorption spectra of Levosimendan in pH7 aqueous solution of HSA
117
lifetime of 350 fs and the second one has a lifetime of 1.9 ps. At pH 11 we find a similar behavior,
which indicates that excitation at 400 nm of the LSM at pH 7 and pH 11 produces the same excited
sates. At pH 3 we also find two bands. The red side band has longer lifetime (460 fs) and the blue
side one has similar lifetime as the one observed at pH 7 and 11. Therefore, based on these
observations, we propose that the excited state decay pathway goes through the same intermediate
state following an ultrafast conversion from the initial excited species. We also investigated the
caging effect of chemical and biological nanocavities of β-CD and human serum albumin (HSA).
The caging effect is strongest for the HAS (Figure 2), which yields lifetimes of 510 fs and 3.3 ps for
the red and blue side of the transient absorption spectra, respectively. For comparison we also
studied the excited state dynamics of LSM in solvents with different polarity and viscosity. We find
that the polarity plays significant role, yielding longer lifetimes for the two transient species, which
indicates the participation of nπ∗. The viscosity effect suggests importance of the molecule
twisting. The above mentioned effects indicate that the deactivation mechanism of the excited LSM
involves intramolecular charge transfer coupled with a twisting motion.
Acknowledgment. This work is supported by JCCM and MICINN, projects PCI08-00375868, CTQ-2005-00114/BQU, UNCM05-23-034. BC thanks MICINN for the Ramon y Cajal
Fellowship.
References
[1] M. El-Kemary et al J. Med. Chem. 2006, 49, 3086
[2] M. El-Kemary et al, J. Phys. Chem. B 2006, 110, 14128
[3] M. El-Kemary et al J. Med. Chem. 2007, 50, 2896
[4] M. Gil, A Douhal Chem. Phys. Lett. 2006, 432, 106
[5] M. Gil, A. Douhal Chem. Phys. Lett. 2006, 428, 174
118
PHOTODYNAMICS OF 4′-DIMETHYLAMINOFLAVONOL INTERACTING
WITH NaX ZEOLITES, MCM-41 MESOPOROUS MATERIAL AND SILICA
NANOPARTICLES
C. Martín, J.A. Organero, A. Roshal and A. Douhal
Department of Physical Chemistry, Facultad del Medio Ambiente, INAMOL, University of Castilla-La Mancha, Toledo,
Spain 45071
Recently, we have shown how the confinement of zeolites and mesoporous silica materials
affects the photodynamics of the encapsulated guest [1,2].
In this work, we report on time-correlated single-photon counting (TCSPC) picosecond
emission dynamics of 4′-dimethylaminoflavonol (DMAF) interacting with NaX, MCM-41 and
silica nanomaterials in suspension using different solvents (Fig. 1).
The emission decays of DMAF interacting with NaX in THF show four components. The
short ones (20 ps and 300 ps) are assigned to free dye molecules in solution, while the other two
longer components (1 and 2.7 ns) arise from molecules interacting with the nanohost framework.
The results for MCM-41 also show 4 components but the observed lifetimes assigned to the
complexes (1.7 ns and 3.4 ns) are longer than those found for NaX. For DMAF interacting with
silica material, the complex gives only one lifetime (3.4 ns) assigned to structures adsorbed on the
particle surface.
We discuss the obtained results in terms of confinement effect of the nanosupport on the
fluorescence relaxation dynamics of DMAF and molecular interactions with the surface of the
mesoporous silica material.
Figure 1. A and B: Schematic representation of DMAF included within NaX and MCM-41 nanocages, respectively. C:
Emission decays of DMAF in (1) THF, and suspension of (2) NaX / THF and (3, 4) MCM-41 and Silice / THF.
Excitation wavelength: 433 nm, emission wavelength: 550 nm (0) is the instrumental response function of the TCSPC
system (80 ps).
References
[1]. M. Gil, J.A. Organero, E. Peris, H. García, A. Douhal, CPL. (2009) 474, 325.
[2]. M. Gil, S. Wang, J.A. Organero, L. Teruel, H. García, A. Douhal, J. Phys. Chem. C. (2009) (in press).
Acknowledgements: This work was supported by the JCCM and MICINN through projects PCI08-5868 and
MAT2008-01609, respectively.
119
Photophysical study of a xanthene derivate in a medium mimicking celular
environment
L.Crovetto, J.M. Paredes, A. Orte, M.J. Ruedas-Rama, R. Rios, J.M. Alvarez-Pez, and E.M. Talavera
Department of Physical Chemistry. University of Granada.18071 Granada. Spain
In recent papers we investigated the photophysics of a new fluorescein derivative, 9-[1-(2Methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II) [1], a compound useful as
“on/off” pH probe, from the so-called Tokyo Green (TG) family. This compound also shows the
characteristic fluoresceins’ ESPT reaction promoted by the presence of phosphate buffer, and
therefore, it can display a single lifetime which can be tuned by the phosphate buffer
concentration, at near-neutral pH [2]. The high quantum yield of TG-II along with its utility in
both sensing phosphate concentration and as “on/off” pH probe, make very interesting the study
of its photophysics in media mimicking cellular environment like ficoll, since physicochemical
properties of aqueous media in biological liquids are known to depend particularly on the
macromolecular composition of the liquids.
In this study, the ground-state equilibrium between the neutral and anionic forms of TG-II in
ficoll 400 and the influence of the addition of buffer on the apparent acidity constant measured
through absorption and fluorimetric titrations was explored and compared with the previous
results obtained in water. Next, the phosphate buffer-mediated Excited State Photon Transfer
(ESPT) reaction and the relevant kinetic model and dynamics were studied in detail by means of
steady-state and time-resolved fluorescence measurements. The underlying kinetic rate
constants, which describe the dynamic behaviour of the system, were determined using global
compartmental analysis (GCA) of the multi-dimensional fluorescence decay surface collected as
a function of emission wavelength (λ em), pH, and buffer concentration (CB). Acidity constant,
obtained by absorption and steady state fluorescent, without buffer, decreased with addition of
ficoll 400, from pKa= 6.1 to pKa= 5.2. However,
the addition of enough phosphate buffer causes an increase in the pKa value, getting closer to
the values obtained in water, due to more accessible hydrogen bonding. The presence of
phosphate buffer at high concentrations (>100 mM) also gives rise to ESPT reactions. The
comparison of the absorption (Figure 1A) and fluorescence emission spectra (Figure 1B) at high
pH show a shift in the wavelength maximum when using ficoll-water mixture, supporting the
idea that effects of ficoll in the acid-base equilibria are related with the change in hydrogen
bonding environment [3].
References
[1] L. Crovetto, J.M. Paredes, R. Rios, E.M. Talavera, J.M. Alvarez-Pez, J. M. J. Phys. Chem. A 2007, 111, 1331113320.
[2] J. M. Paredes, L. Crovetto, R. Rios, A. Orte, J. M. Alvarez-Pez, E. M. Talavera, Phys. Chem. Chem. Phys., 2009, 11,
5400-5407.
[3] N. Klonis, A.H.A. Clayton, E.W. Voss, W.H. Sawyer. Photochem. Photobiol., 1998, 67, 500-510.
120
A
B
0,3
Water
Water-ficoll
water-ficoll buffer
Fluorescence 440
Absorbance
14
0,2
0,1
+
% water-ficoll
12
-
10
8
0,0
480
490
500
λ / nm
510
6
520
560
600
640
λ/ nm
Figure 1. (A) Absorption spectra shift of TG-II in basic media (pH=8): in water, water-ficoll (20%) media, and waterficoll (20%) with addition of increasing buffer concentrations. (B) Fluorescence shift of TG-II in basic media (pH=8) in
water and different water-ficoll (%) media.
121
FEMTOSECOND PULSED LASER DEPOSITION OF CdS
NANOSTRUCTURES
M. Sanza, J. G. Izquierdob, L. Bañaresb , M. Castillejoa
a
Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
b
Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad
Complutense de Madrid, 28040 Madrid, Spain.
Femtosecond Pulsed Laser Deposition (fs-PLD) is an advantageous and efficient technique for
synthesis of metal and semiconductor nanoparticles (NPs). While most of the studies have
employed pulses centred at 800 nm (around the peak wavelength of Ti:Sapphire laser), recent work
has demonstrated the dependence in fs-PLD between wavelength, the control of the nanoparticle
size and the reduction of micro-particulates [1]. Analysis over a broader range of wavelengths can
provide important clues about NPs formation and serve as experimental tests for advanced
theoretical models.
Cadmium sulfide (CdS), one of the most important II–VI group semiconductors, has vital
applications in different fields such as optoelectronic, integrated optics and photovoltaic devices [2].
The performance of these applications can be improved when using nanostructured material.
Studies of CdS films grown by fs-PLD at 800 nm have shown that the deposits strongly depend on
the growth conditions, namely the nature and temperature of the substrate and the laser fluence [3].
In this work we concentrate in the fabrication and characterization of the nanostructured deposits
grown on Si (100) substrate produced by laser ablation of CdS sintered target in vacuum using a
Ti:Sapphire laser delivering 60 fs pulses. The effect of the laser irradiation wavelength and fluence
on the obtained nanostructures has been investigated using 800, 400 and 266 nm, in a range of
substrate temperatures that are suitable for obtaining nanostructured deposits. Results are discussed
in reference to the crystalline quality and composition of the deposits, characterized using X-ray
diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and to the surface morphology,
observed by Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy
(AFM).
References
[1] Sanz, M.; Walczak, M.; De Nalda, R.; Oujja, M.; Marco, J.F.; Rodríguez, J.; Izquierdo, J.G.; Bañares, L.; Castillejo,
M., Appl. Surf. Sci., 2009, 255, 5206.
[2] Hullavarad, N.V.; Hullavarad, S.S.; Karulkar, P.C., J. Nanoscie. Nanotech., 2008, 8, 3272.
[3] Tong, X.L.; Jiang, D.S.; Liu, L.; Liu, Z.M.; Luo, M.Z., Opt. Comm., 2007, 270, 356.
122
CHARACTERIZATION OF HOLOGRAPHIC GRATINGS
IMPLEMENTED IN A PHOTOPOLYMERIZABLE GLASS WITH
FEMTOSECOND LASER PULSES
J. G. Izquierdoa, M. P. Hernández-Garayb, O. Martínez-Matosb, J.A. Rodrigoc, R. Weigandb, M.L. Calvob,
L. Bañaresa and P. Chebend
a
Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad
b
Departamento de Óptica, Facultad de Ciencias Físicas, Universidad
c
Departamento de Imágenes y Visión, Instituto de Óptica Daza de Váldes,
CSIC, 28006 Madrid, Spain.
d
Institute for Microstructural Sciences, National Research Council of Canada,
OntarioK1AOR6, Canada.
Recently a sol-gel volume holographic glass has been developed [1,2] which is suitable for
recording volume transmission holographic gratings with high performance. This new material [1]
is a modified composition of a highly efficient photopolymerizable sol-gel glass synthesized by
Cheben et al. [3], incorporating Zr-based high refractive index species (HRIS) at molecular level.
The physical mechanism of grating formation involves a co-directional diffusion of monomer and
HRIS species upon inhomogeneous illumination [4] which makes possible a self-developed
hologram with a permanent phase grating with an improved dynamic range, low coherent and
incoherent scattering noise, high optical quality, high diffraction efficiency and insignificant
shrinkage [1]. Gratings of 500 and 2000 lines/mm have been recorded by the interference of two
collimated s-polarized beams coming from a Nd:YAG continuous and monochromatic laser
(532 nm).
We have recently extended our studies to ultrashort pulse lasers in femtosecond regime. In
this work we present the characterization of the transmitted and diffracted light by the holographic
gratings when it is illuminated with a femtosecond pulse laser centred at 800 nm, with an energy of
1 mJ/pulse, a frequency of 1 KHz and a temporal length of 60 fs. Spectral profiles have been
studied demonstrating the convenience of the holographic glass to manipulate the complex field and
the spectral components of the femtosecond pulse laser [Fig. 1.a, 1.b], according to the specific
application. Moreover intensity profiles [Fig.2] for transmitted (T) and diffracted (D) beams have
been analyzed showing that grating diffraction smoothes the intensity distribution performing as
one axis high spatial frequency filter.
Figure 1 a. Incident (Black curve), transmitted (red curve) and diffracted (green curve) spectral profile
when a 500 lines/mm grating is illuminated with a femtosecond pulse laser. Grating parameters: width 65 µm and
refractive index modulation of 3.2 10-3
123
Figure 1. b. Incident (Black curve) and diffracted spectral profile when a 2000 lines/mm grating is illuminated with a
femtosecond pulse laser. Coloured curves represent the spectral selectivity for different incident angles. Grating
parameters: width 110 mm and refractive index modulation 3.0 10-3
Figure 2. Intensity profile for transmitted (T) and diffracted (D) beams
References
[1] Del Monte, F.; Martínez-Matos, O.; Rodrigo, J. A.; Calvo, M. L. and Cheben, P., Adv. Mater., 2006, 18, 2014.
[2] Martínez-Matos, O.; Rodrigo, J. A.; Calvo, M. L. and Cheben, P, Opt.. Lett. 2008, 34, 485.
[3] Cheben P. and Calvo M. L. , Appl. Phys. Lett. 2001, 78, 1490.
[4] Martínez-Matos, O.; Calvo M. L.; Rodrigo, J. A.; Cheben, P. and Del Monte, F, Appl. Phys. Lett. 2007, 91, 1.
124
Polymeric matrices containing self-assembled fibrillar networks and quantum
dots
M. A. Izquierdo, F. Galindo, P. Wadhavane, M. I. Burguete, S. V. Luis
Departamento Química Inorgánica y Orgánica, Universidad Jaume I Castellon
Self-assembly of small molecules into hierarchically ordered superstructures is a subject of major
interest in chemistry, biology and materials science. One interesting application of the formed selfassembled fibrillar networks is their use as templates for the synthesis of structured materials [1].
Recently, we have used this approach to prepare different polymeric materials from the organogels
formed by macrocyclic pseudopeptides in a polymerizable methacrylic mixture [2]. For this
purpose, a mixture of polymer precursors was used as a solvent for the formation of the gel and the
reactive medium was then polymerized, trapping the fibrillar networks.
Here we present a similar strategy to prepare polymeric matrices containing self-assembled fibrillar
networks and semiconductor quantum dots (QD). Compared to organic molecules, these inorganic
nanoparticles posses exceptionally different fluorescent features including narrow emission spectra
broad excitation band, reduced tendency to photobleach and higher photoluminescence efficiency
[3]. Preparation of QDs-dipeptide nanocomposite gels has been recently described and the
capability of the QD-doped gels for chemical sensing has been demonstrated [4]. Therefore, they
appear as interesting candidates to prepare organogel imprinted polymers containing quantum dots.
Cyclophane 1 and 2 are capable of self-association to form fibrils leading to thermoreversible
organogels in a variety of solvents [5] and were the substrates of choice in this study. First,
comparative experiments of commercial CdSe/ZnS quantum dots in toluene and organogels formed
by 1 and 2 were conducted. Steady state and time resolved results were analyzed to determine the
photophysical properties of the studied QDs in both organogels. Then, polymeric imprinted films
derived from organogelators 1 and 2 and QDs were prepared and characterized by optical and
fluorescence microscopy, steady-state fluorescence and time- resolved fluorescence. Results
obtained for 1 and 2 both in the organogel and in the imprinted polymers will be discussed in terms
of the photophysical properties of the quantum dots in the new polymeric films.
·
O
NH
NH
n HN
O
·
HN
1n=1
2n=3
References
[1] F. X. Simon, N. S. Khelfallah, M. Schmutz, N. Diaz, N.P. Mesini, J. Am. Chem. Soc. 129 (2007) 3788; U. Beginn,
Adv. Mater. 10 (1998) 1391.
[2] M. I. Burguete, F. Galindo, R. Gavara, M. I. Izquierdo, J. C. Lima, S. V. Luis, A. J. Parola, F. Pina, Langmuir 24
(2008) 9795.
[3] R. C. Somers, M. G. Bawendi, D. G. Nocera, Chem. Soc. Rev. 36 (2007) 579.
125
[4] D. Bardelang, Md. B. Zaman, I. L. Maoudrakovski, S. Pawsey, J. C. Margeson, D. Wang, X. Wu, J. A. Primeester,
C. I. Ratcliffe, K. Yu, Adv. Mater. 20 (2008) 4517; X. Yan, Y. Cui, Q. He, K. Wang, J. Li, Chem. Mater. 20 (2008)
1522.
[5] J. Becerril, M. I. Burguete, B. Escuder, F. Galindo, R. Gavara, J. F. Miravet, S. Luis, G. Peris, Chem. Eur. J. 10
(2004) 3879; F. Galindo, M. I. Burguete, R. Gavara, S. Luis, J. Photochem. Photobiol. A: Chem. 178 (2006) 57; M. I.
Burguete, M. A. Izquierdo, F. Galindo, S. Luis, Chem. Phys. Lett. 460 (2008) 503.
126
Reactividad del Oxígeno Molecular Singulete, O21∆g, frente a Flavonoides en
Vesículas de Dipalmitoilfosfatidilcolina
Else Lemp M.1, Antonio L. Zanocco1 y Javier Morales-Valenzuela.2
1
1
Universidad de Chile, Facultad de Ciencias Químicas y Farmacéuticas, Departamento de Química Orgánica y
Fisicoquímica, Casilla 233, Santiago - 1, Santiago, Chile.
Universidad de Chile, Facultad de Ciencias Químicas y Farmacéuticas, Departamento de Ciencias y Tecnología
Farmacéutica, Casilla 233, Santiago - 1, Santiago, Chile.
El oxígeno molecular es una de las moléculas fundamentales para la existencia de los seres
vivos. Cerca del 95% del O2 que consumen organismos del tipo aeróbico es reducido
completamente a H2O durante los procesos de respiración mitocondrial, y tan sólo una fracción del
pequeño porcentaje restante es convertido en distintos procesos a especies semirreducidas,
conocidas como Especies Reactivas del Oxígeno (ROS) [1]. Estas últimas moléculas, cumplen
importantes funciones en la fisiología de los organismos vivos, al participar en mecanismos de
transducción de señales, eliminación de agentes invasores externos, entre otras funciones. Sin
embargo, en estados patológicos se produce un desbalance entre la producción de ROS y los
mecanismos naturales de defensa antioxidante que poseen los organismos, lo que genera un estado
conocido como estrés oxidativo [2-6]. En este estado, las especies reactivas del oxígeno, entre las
que se incluye la especie excitada de menor energía, el oxígeno molecular singulete, O2(1∆g),
originan múltiples daños en las estructuras celulares llegando a ocasionar graves alteraciones en
procesos fisiológicos normales. Dentro de los daños se encuentran modificaciones químicas de
macromoléculas de relevancia biológica como el ADN, proteínas, lípidos y carbohidratos (7,8). Las
alteraciones producidas en estas biomoléculas se han identificado como factores directos en la
iniciación y desarrollo de procesos de envejecimiento y en enfermedades de notable morbilidad y
mortalidad, entre ellas aterosclerosis, cáncer, enfermedades degenerativas del sistema nervioso
central, daño isquémico, enfermedades autoinmunes, diabetes, SIDA, etcétera.
Los flavonoides son compuestos polifenólicos ampliamente distribuidos en el reino vegetal.
En los últimos años se han estudiado recurrentemente debido a sus múltiples propiedades
beneficiosas para la salud, destacando el rol que cumplen por ejemplo, en la prevención de
enfermedades cardíacas y cáncer. Muchas de las propiedades farmacológicas de los flavonoides se
originan en la capacidad antioxidante, que protege de los efectos nocivos que producen los radicales
libres y otras especies reactivas del oxígeno en células y tejidos de sistemas de interés biológico.
Sin embargo, son limitados los estudios relativos a la desactivación del oxígeno molecular
singulete por flavonoides. La mayoría de estos estudios se relacionan a su desactivación en medio
homogéneo, en un conjunto limitado de solventes [7-11]. Más escasa aún es la información sobre el
efecto antioxidante de flavonoides frente al daño oxidativo producido por el ataque del oxígeno
molecular singulete en membranas lipídicas.
En el presente trabajo, se informa acerca de la reactividad del O2(1∆g) frente a una serie de
flavonoides (quercetina, canferol, rutina, miricetina, quercitrina, morina, catequina y epicatequina)
en soluciones de liposomas unilamelares de dipalmitoilfosfatidilcolina (DPPC), modelo que
mimetiza la membrana fosfolipídica.
Los estudios de incorporación de flavonoides a soluciones de liposomas de
dipalmitoilfosfatidilcolina, DPPC, indican que los liposomas solubilizan a los flavonoides mediante
127
dos mecanismos: de disolución del sustrato en la bicapa lipídica y de adsorción del flavonoide en la
interfase del liposoma. El reparto de flavonoides en el sistema bifásico octanol/tampón pH 7,4
depende del número de grupos hidroxilos en la estructura básica y de la naturaleza del enlace 2,3 en
el anillo C del flavonoide.
La sal de amonio cuaternario de un derivado de alquilfurano HFDA, (bromuro de 2-(12(N,N,N-trimetil)-dodecil)-5-hexilfurano), puede ser usada exitosamente como actinómetro para
medir la concentración estacionaria de O2(1∆g), en bicapas lipídicas de liposomas de DPPC, cuando
su consumo se mide utilizando un método de cromatografía líquida de alta eficiencia. Usando el
modelo de dos pseudofases para describir la cinética de reacciones en las que un flavonoide y un
derivado del alquilfurano HFDA, compiten por el oxígeno molecular singulete, O2(1∆g), se
encuentra que la reactividad de los flavonoides frente al oxígeno excitado en bicapas lipídicas de
liposomas de dipalmitoilfosfatidilcolina, es mayor en un orden de magnitud que la observada en
fase homogénea y que la reactividad es independiente de la desactivación del O2(1∆g) por la fase
externa de la solución de liposomas. Los resultados del tratamiento cinético permite estimar la
velocidad con la cual los flavonoides estudiados desactivan al O2(1∆g) en la bicapa lipídica,
encontrándose que los flavonoides protegen la membrana lipidica frente al ataque del oxígeno
excitado, en el orden: miricetina > morina > rutina > quercetina > quercitrina > canferol >
epicatequina > catequina. Por otra parte, los valores de las constantes de velocidad de la reacción
química entre los flavonoides y O2(1∆g) en fase homogénea muestran una relación directa con la
activación del doble enlace de la posición 2,3 del anillo C de la estructura básica de estos
compuestos, resultado indicativo de que este sitio corresponde al centro reactivo. La morina, es el
flavonoide que presenta el mayor valor en la constante de velocidad de reacción química,
probablemente como consecuencia del número y posición de los grupos hidroxilos en el anillo B de
su estructura, los cuales aumentan la densidad electrónica sobre el doble enlace del anillo C.
El modelo desarrollado en este trabajo para determinar de constantes de velocidad de
desactivación del oxígeno molecular singulete por sustratos incorporados en la membrana lipídica
de liposomas, puede ser fácilmente extendido para describir el comportamiento del O2(1∆g) en
sistemas biológicos más complejos.
Agradecimientos
Los autores agradecen el financiamiento de FONDECYT (proyecto Nº 1090267).
Referencias
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
128
B. Halliwell, J.Gutteridge, Free Radicals in Biology and Medicine, 2 Ed, Oxford UK, Clarendon Press, 1989.
K. Apel, H. Hirt, Annu. Rev. Plant Biol. 55 (2004) 373-399.
U. Bandyopadhyay, D. Das, R. Banerjee, Current Science, 77 (1999) 658-666.
J. Imlay, Annu. Rev. Microbiol. 57 (2003) 395-418.
J. López-Barneo, R. Ricardo-Pardal, P. Ortega-Sáenz, Annu. Rev. Physiol. 63 (2001) 259 -287.
M. Valko, D. Leibfritz, J. Moncol, M. Cronin, M. Mazur, J. Telser, Intern. J. Biochem. & Cell Biol.. 39 (2007) 4484.
T. Matsuura, H. Sakamoto, J Am. Chem. Soc. 89 (1967) 6370-6376.
T. Matsuura, R. Nakashima, Tetrahedron 26 (1970) 435-438.
P.T. Chou, M. Kasha, J. Phys Chem. 88 (1984) 4596-4601.
C. Turnaire, S. Croux, M. Maurette, I. Beck, M. Hocquaux, A. Braun, E. Oliveros, J. Photochem. Photobiol. B:
Biol. 19 (1993) 205-215.
C. Borsarelli, M. Montenegro, M. Nazareno J. Photochem. Photobiol. A: Chem. 186 (2007) 47-56.
Time-resolved optical emission spectroscopic study of ambient air induced by a
high-power TEA-CO2 pulsed laser
J. J. Camacho1, L. Díaz2, M. Santos2, L. Juan1, E. Martin1 and J.M.L. Poyato1
1
Departamento de Química-Física Aplicada. Facultad de Ciencias. Universidad Autónoma de Madrid.
Cantoblanco. 28049-Madrid. Spain.
2
Instituto de Estructura de la Materia, CFMAC, CSIC, Serrano 121. 28006-Madrid, Spain
A transverse excitation atmospheric (TEA) CO2 pulsed laser (λ=10.591 µm, 64 ns (FWHM),
47-347 J/cm2) was focused onto a metal mesh target under air as host gas at atmospheric pressure. It
is found that the CO2 laser is favourable for generating strong, large volume air breakdown plasma,
in which the air plasma was then produced overwhelmingly. While the metal mesh target itself was
practically never ablated, the air breakdown is mainly due to electronic relaxation of excited N, O,
C, H, Ar and ionic fragments N+, O+, N2+, O2+, C+ and molecular band systems of N2+(B2Σu+X2Σg+), N2(C3Πu-B3Πg), N2+(D2Πg-A2Πu) and OH(A2Σ+-X2Π) [1,2]. Plasma characteristics were
examined in detail on the emission lines of N+, O+, and C by means of time-resolved opticalemission spectroscopy (TROES) technique. The results show a faster decay of continuum and ionic
spectral species than in the case of neutral atomic lines and molecular bands. The velocity and
kinetic energy distributions for different species were obtained from time-of-flight measurements.
Excitation temperature and electron density in the laser-induced plasma were estimated from the
analysis of spectral data at various times from the laser pulse incidence. Possible mechanisms for
the production of these distributions are discussed. A schematic diagram of the experimental setup
of the time gated ICCD for pulsed laser air breakdown diagnostics is shown in Fig. 1. Photographs
of the TEA-CO2 laser plasmas (70.5 J/cm2) in open-air (top-left) and inside a cell (bottom-right) and
shock wave images obtained in open-air are also shown in this figure. As example, Fig. 2 displays
TROES from laser-induced (106 J/cm2) air plasma observed in the region 2423-2573 Å monitored
at 2, 3, 4, and 5 µs gate delays for a fixed gate width time of 0.5 µs and z=2.5 mm.
+
+
N
O
+
O
+
N
+
2+
O
N
2+
O
+
O
C
Relative Intensity / a. u.
20000
td=2 µs; tw=0.5 µs
15000
10000
5000
0
2425
2450
2475
2500
2525
Wavelength / Å
2550
ACKNOWLEDGMENTS
This work was partially supported by the MEC Projects: CTQ2007-60177/BQU and CTQ200805393/BQU.
[1] J.J. Camacho, M. Santos, L. Diaz and J.M.L. Poyato, J. Phys. D: Appl. Phys. 41 (2008) 215206.
[2] J.J. Camacho, J.M.L. Poyato, L. Diaz and M. Santos, J. Phys. B: Opt. Phys. 40 (2007) 4573.
129
PHOTOPHYSICS PROPERTIES OF 3- AND 4- AMINE 1,8NAPHTHALIMIDE N-SUBSTITUTED
E. Martin1, J.L.Gu. Coronado, J.J. Camacho and J.M.L. Poyato
Departamento de Quimica Fisica Aplicada, Mod.C- XIV- Facultad de Ciencias,
Universidad Autonoma de Madrid, Cantoblanco 28049 Madrid, SPAIN
1
[email protected]
3-Amino 1,8-napthalimide derivatives N- Substituted have anti-tumoral activity [1] and a
photoinduced charge transfer effect (CT) in polar solvent as acetonitrile. The spectroscopic
properties in the UV-Visible zone change with the polarity and proticitity of the solvents. The
isomer 4-amine doesn’t have anti-tumor activity and the spectroscopic properties are very different.
In this communication we study four derivatives, Fig. 1, in two neutral solvents water and
dichloromethane (DCM), and acidified with acetic acid, to analyze the influence in the electronic
transition. The twisted intramolecular CT (TICT) is a plausible model to explain this behaviour.
The semi-rreduction potentials obtained in acetonitrile by cyclic voltammetry [2,3] have showed
that the 4- position have more negative value than the 3- position, which indicate that 4-amine
derivatives have the higher tendency as electronic donating to naphthalene ring in the planar form.
The acidified solutions change the environment and may produce the rotation of the R2 group.
By the complementary way, we have implemented semiempirical calculations with PM3 method
[3]. It shows that the quinoidic form can contribute at the electronic transition on 4-amine
derivatives in R2.
The four compound studied have lower solubility, extinction coefficient and fluorescence quantum
yields in water than in DCM. The addition of the proton modified slightly this behaviour.
R1
O
N
O
1
2
3
4
R1
-Et
-(CH2)2-N(CH2)4
-(CH2)2-N(CH2)4
-(CH2)2-NMe2
R2
-NH2 (3)
-NH2 (3)
-NH2 (4)
-NH-Bu (4)
3
4
R2
Figure 1. Molecular structure of the compounds studied.
References
[1] M.F. Braña, A.M. Sanz, J.M. Castellano, C.R. Roldán and C. Roldán, Eu.J.Med.Chim.Ther. 16 (1981) 207.
[2] E. Martín and R. Weigand; Chem. Phys. Lett. 288(1) (1998) 52.
[3] E. Martín, J.L.Gu. Coronado, J.J. Camacho and A. Pardo; J. Photochem.Photobiol,A:Chem. 175(1) (2005) 1.
130
Papel de las fuerzas electrostáticas e hidrofóbicas en las interacciones entre
Rodamina 123 y diferentes tipos de tensioactivos
M. Novo, S. Freire, D. Granadero, J. Bordello, W. Al-Soufi
1
Departmento de Química Física, Universidad de Santiago de Compostela, 27002 Lugo
En este trabajo se estudian las interacciones de un fluoróforo catiónico con tensioactivos de
diferentes tipos atendiendo a la carga del grupo cabeza. Para ello se analizan las variaciones de los
espectros de absorción Vis-UV y de emisión de fluorescencia y del tiempo de vida de fluorescencia
del fluoróforo en función de la concentración de tensioactivo, identificando las especies presentes y
los procesos fisicoquímicos y fotofísicos responsables del comportamiento observado. Junto con las
fuerzas hidrofóbicas responsables de la entrada del fluoróforo en las micelas de los diferentes
tensioactivos, las interacciones electrostáticas entre el fluoróforo y los tensioactivos cargados
juegan un papel fundamental en los cambios observados.
El fluoróforo elegido es la Rodamina 123 (R123), un marcador típico de las membranas
mitocondriales de células vivas que se encuentra como catión en un amplio intervalo de pH,
presenta un rendimiento cuántico muy alto y tiene una gran fotoestabilidad. En cuanto a las
sustancias tensioactivas, se estudiaron moléculas no iónicas, catiónicas y aniónicas, utilizando tanto
tensioactivos modelo ampliamente descritos en la bibliografía como otros de aplicación en la
industria de detergentes. Estos últimos presentan generalmente una elevada polidispersidad que
también puede tener implicaciones en el comportamiento observado para la sonda fluorescente.
La interacción de la R123 con tensioactivos no iónicos se produce a concentraciones superiores a la
Concentración Micelar Crítica (CMC) del tensioactivo y consiste en un equilibrio de reparto de la
sonda entre la disolución acuosa y la pseudo-fase micelar [1]. Las constantes de equilibrio son
elevadas y están relacionadas con la hidrofobicidad del medio micelar. Para los tensioactivos
catiónicos el comportamiento observado es similar, aunque se produce una desactivación de la
fluorescencia de la R123 debida a los contraiones haluro libres en el medio acuoso. Además, las
constantes de equilibrio de reparto de la sonda con las micelas catiónicas son muy inferiores a las
determinadas con micelas no iónicas, lo que se atribuye a las repulsiones electrostáticas entre la
sonda y la superficie micelar. Finalmente, en el caso de tensioactivos aniónicos, las interacciones
entre la sonda y el tensioactivo están dominadas por las fuerzas de atracción electrostática a
concentraciones bajas de tensioactivo, observándose la formación de pares iónicos con propiedades
fotofísicas bien diferenciadas, y por las interacciones hidrofóbicas a concentraciones de tensioactivo
cercanas a la CMC. Para estos sistemas los cambios espectrales se producen a concentraciones
inferiores a la CMC y no se observan variaciones a concentraciones mayores, lo que indica una
fuerte interacción de la sonda con las micelas que lleva a una completa asociación.
Todos los sistemas en estudio fueron analizados cuantitativamente sobre la base de mecanismos
adecuados y utilizando los métodos de Análisis de Componentes Principales y Análisis Global
(PCGA) [2]. Como resultado de dichos análisis se obtuvieron los parámetros fisicoquímicos
implicados en los modelos propuestos y los espectros y propiedades fotofísicas de la sonda asociada
a cada tipo de micela. La comparación de estos resultados permite discutir el papel de las fuerzas
electrostáticas e hidrofóbicas en la interacción de esta sonda con los medios micelares.
Referencias
[1] M. Novo, S. Felekyan, C.A.M. Seidel, W. Al-Soufi J. Phys. Chem. B 111 (2007) 3614.
[2] W. Al-Soufi, M. Novo, M. Mosquera, Appl. Spectrosc. 55 (2001) 630.
131
Photosensitized materials doped with LDS 698: photophysical and lasing
properties
M. Pintado-Sierra1, V. Martín1, R. Sastre2, A. Costela1, I. García-Moreno1
1
2
Departamento de Química Láser, Instituto de Química-Física “Rocasolano”, CSIC
Departamento de Fotoquímica, Instituto de Ciencia y Tecnología de Polímeros, CSIC
Up to date, most of the promising results in solid-state dye lasers have been obtained in the yellow
region (550-600 nm) based on pyrromethene-doped matrices.[1] On the other hand, few results
have been published on dye-doped solid-state lasers emitting in the red part of the visible spectrum,
in the range 610-650 nm. Potential advantages of emissions in this spectral region are nearness to
the second low-loss window of typical polymer optical fibers that lies at 650 nm,[2] deep
penetration of the light in biological systems, significant reduction of the background signal because
of the lowest autoabsorption and autofluorescence of biomolecules and low light scattering.[3]
In the search to extend the tuning range of SSDL to the red spectral region, we have designed and
synthesized new photosensitized materials based on the hemicyanine dye LDS 698 incorporated
into different linear, sililated and fluorinated polymeric matrices.
There are no systematic studies on the photophysical properties of this chromophore; for this
reason, and previous to its inclusion into solid matrices, we carried out an analysis of its
photophysical and laser behaviour in liquid phase as a guide to develop polymeric materials which
could enhance their laser action in solid-state.
The absorption and emission spectra were recorded in acetone and polar protic solvents, because
this dye is not soluble in apolar and low-polar ones. In all cases, it shows low absorption
coefficients and fluorescence quantum yields, and short lifetimes. These results together with very
large Stokes shifts and a solvatochomic dependence of the fluorescence, suggest that the emission
takes place via an intramolecular charge transfer process (ICT) from the aniline group (electron
donor) to the piridinium group (electron acceptor).
Under transversal pumping at 532 nm, 5.5 mJ/pulse and 10 Hz, the laser action of LDS698 was
studied as a function of its concentration and the nature of the solvent. In spite of its low
fluorescence, this dye exhibits efficient laser emission reaching an efficiency of up to 46% in a
4×10-4 M ethanolic solution. The non-radiative relaxation processes have to be significantly reduced
due to the very short lifetime of the excited state and the large Stokes shifts.
Finally, the influence of composition and structure of the solid matrix on the laser action of LDS
698 was analyzed, in a systematic way, for the dye dissolved at a common 4×10-4 M concentration
in a number of copolymeric formulations with different compositions based on HEMA, since this is
the monomer which mimics the ethanol solvent.
Broad-line-width laser emission in a simple plane-plane non-tunable resonator with a single peak
wavelength centred at ≈660 nm with beam divergence of ≈3 mrad and pulse duration of ≈5 ns
FWHM was obtained from the materials under study. Lasing efficiencies of up to 22% for laser
operation in non-optimized cavities were obtained although the best efficiency/stability compromise
for this dye was reached with the homopolymer pHEMA: a 14% of efficiency with a good
photostability, since the laser output remained at 55% of its initial value after 100,000 pump pulses
132
Laser emission (a.u.)
in the same position of the sample at 10 Hz repetition rate. The tuning capability of the dye-doped
solid matrices, one of the most important features of dye lasers, was determined placing the samples
in a grazing-incidence grating cavity in Shoshan configuration. Tunable laser emission, with
linewidth of the order of 0.15 cm-1 was obtained, and tuning range of up to 60 nm was thus
recorded, so that the spectral region 630-700 nm can be continuously covered with narrow-linewidth and stable laser radiation.
630 640 650 660 670 680 690 700
Wavelength (nm)
Figure 1. Photosensitized materials based on LDS 698 with tunable laser emission in the red spectral region.
Consequences of this exhaustive study are the first results on the laser action of LDS698 doped
solid-state matrices. These new laser materials show the potential to be used as active media in
highly compact, reproducible, versatile, and easy to handle solid-state dye lasers as attractive
alternative to the commercially available dye lasers in liquid phase impelling the applications of this
new technology into biophotonic and optoelectronic fields.
References
[1] Tunable Laser Applications. Edited by F. J. Duarte, CRC Press 2008.
[2] M. C. Ramon, M. Ariu, R. Xia, D. D. C. Bradley, M. A. Reilly, C. Marinelli, C. N. Morgan, R. V. Penty, I. H.
White, J. Appl. Phys. 97 (2005) 073517.
[3] K. Umezawa, Y. Nakamura, H. Makino, D. Citterio, K. Suzuki, J. Am. Chem. Soc. 130 (2008) 1550.
133
STUDIES OF CHIRAL RECOGNITION IN THE ENCAPSULATION OF
NAPROXEN INTO HYPERBRANCHED MACROMOLECULES WITH A
PHOTOACTIVE CORE
Salvador Pocoví-Martínez1, Lourdes Pastor-Pérez, M.C. Cuquerella,
Salah-Eddine Stiriba and Julia Pérez-Prieto
1
Instituto de Ciencia Molecular / Icmol, Universidad de Valencia Polígono la Coma s/n, 46980, Valencia, Spain
Enzymes are remarkably specific both in the selection of their guest and in the reactions they
catalyze. The high degree of catalytic selectivity of enzymes results from the very specific structural
demands of binding of a guest to an “active site” of the protein framework of the enzyme. A key
feature of enzymes is their capacity for “molecular recognition” and binding with the active site by
a particular guest in an extremely selective manner. In the attempt to mimic the function of
enzymes, macromolecules with dendritic patterns represent a unique class of artificial building
blocks due to their globular structure, structural uniformity, multivalency and variation of chemical
composition. While the concept of utilizing perfect dendritic structures, i.e dendrimers, as sensors in
chiral recognition processes has been under considerable focus, the utilization of their imperfect
analogues, known as hyperbranched polymers, has not been addressed until now. Although these
polymers are easily accessible via one-pot procedures, their preparation in a chiral fashion and the
encapsulation of a single functional active site within the macromolecular backbone has not been
practical so far with a one-pot approach.[1]
Very recently, we achieved the covalent incorporation of a single photoactive entity within
hyperbranched polyether polyols known as hyperbranched polyglycerols (PG). These
macromolecules are easily accessible via one-pot polymerization of racemic glycidol in the
presence of 2,2’,4,4’-tetrahydroxybenzophenone as the core-initiator. The resulting monodisperse
photoactive macromolecules exhibit unusual photoactive and photocatalytic properties, with a
remarkable branching effect on the photoactive benzophenone core properties.[2]
The modularity of our synthetic route to encapsulate 2,2’,4,4’-tetrahydroxybenzophenone
core within chiral hyperbranched polyglycerols permits the formation of a chiral benzophenone core
[(P) or (M)] configuration] surrounded by a chiral environment. Therefore, this system could be
used as a chiral sensor.
Spectroscopic techniques, such as absorption and dichroism spectroscopy, were used to
evaluate the degree of recognition in the encapsulation of chiral carboxylic acids. The results
obtained when using naproxen, a non-steroidal anti-inflammatory drug, will be discussed.
134
(R)- or (S)-CHIRAL GUEST
O
OH
O
HO
HO
O
O
HO
HO
HO
HO
O
HO O
O
HO
HO
HO
O
O
HO
HO
O
O
O
HO
OH
O
O
O
O
OH OH
HO
OH
HO
HO
HO
OH
HO
O
O
O
O
O
O
OH
O
O
O
OH
OH
OH
OH OH
O
OH
O
O
O
O
O
OH
O
O
O
OH
O
O
O
O
OH
O
HO OH
OH
HO
OH
O O
HO
HO
O
HO
HO
O
HO
OH
CHIRAL SENSOR= TOBP-(S-rac)-PG
References
[1] Newkome, G. R.; Morefield, C. N.; Vögtle, F. Dendritic Molecules: Concepts, Synthesis, Perspectives; VCH:
Weinheim, 1996,
[2] (a) L. Pastor-Pérez, E. Barriau, E. Berger-Nicoletti, A. F. M. Kilbinger, J. Pérez-Prieto, H. Frey, S.-E. Stiriba,
Macromolecules 2008, 41, 1189-1195. (b) L. Pastor-Pérez, E. Barriau, H. Frey, J. Pérez-Prieto, S.-E. Stiriba, J.
Org. Chem. 2008, 73, 4680-4683.
135
Estudio fotoquímico de interruptores moleculares biomiméticos
Pedro J. Campos, Diego Sampedro, Laura Rivado-Casas
Departamento de Química
Universidad de la Rioja, Unidad asociada al C.S.I.C.
C/ Madre de Dios, 51, Logroño, La Rioja
www.unirioja.es, [email protected]
Hace medio siglo, Richard Feymann con su profética conferencia “Plenty of Room at the
Bottom” marcó los comienzos de la nanociencia asegurando que prácticamente la totalidad de la
máquinas podían ser construidas a escala molecular.1,2 Dentro de la nanociencia, se engloba la
nanotecnología como un nuevo campo hacia el desarrollo de nuevos materiales, los cuáles a escala
molecular permitirán grandes avances en campos como la medicina, nanomateriales, o el
almacenamiento de energía.
En los últimos 50 años, los químicos han sintetizado dispositivos moleculares capaces de
generar un movimiento o transformar un tipo de energía en trabajo. Son las pequeñas piezas que
uniéndolas selectivamente en los puntos específicos adecuados,1 configurarán las máquinas
moleculares en un futuro.
Estas máquinas operan a través de movimientos a escala molecular, como ocurre en la
isomerización cis-trans del cromóforo del retinal en el proceso de la visión. Esta fotoisomerización
ha servido como ejemplo para la síntesis de multitud de dispositivos. Los interruptores que
presentamos (Figura 1), gracias a la luz, se isomerizan provocando un cambio, lo cuál puede
generar otro cambio más allá dependiendo de la macroestructura dónde se encuentren situados.
Además de su síntesis, se expone en la presente comunicación un estudio de sus propiedades
fotoquímicas tales como cinéticas de isomerización y rendimientos cuánticos.
CO2CH3
Ph
Ph
N
350 nm
OCH2CH3
N
OCH2CH3
CO2CH3
Figura 1. Ejemplos de interruptores moleculares sintetizados en la Universidad de la Rioja
References
[1] (a) Feynman, R. P. The Pleasure of Finding Things Out. Ed. Perseus Books, Massachusetts, 1999. (b) There is
plenty of Room at the Bottom www.its.altech.edu/~feynman (Página web visitada el 4 de Junio de 2009).
[2] (a) Lehn, J.-M. Supramolecular Chemistry: Concepts and Perspecives. Ed. VCH, Weinheim, 1995. (b) Lehn, J.-M.
Science, 1993, 260, 1762.
136
Luminescent indicator dyes for heavy metals determination
André Santos1, Kássio M. G. Lima2, Guillermo Orellana1*
1
Dpmt. of Organic Chemistry, Faculty of Chemistry, Universidad Complutense de Madrid, 28040 Madrid (Spain)
2
Institute of Chemistry, UNICAMP, p.o box 6154, 13083-862, Campinas, Brazil; [email protected]
Luminescent ruthenium(II) complexes with polyazaheterocyclic ligands present high emission
lifetimes at ambient temperature (0.1–5 µs), photochemical and thermal stability, high absorption
coefficient in the visible region and a large Stokes shift [1]. These properties can be finely tuned by
modifying the ligand structure, a feature of great interest for optical sensing [2]. The work presented
here had the objective of synthesizing and studying spectroscopically two luminescent
ruthenium(II) complexes with an additional chelating ligand of the imidazole family (Figure 1), and
to study its potential use for (reversible) metal ion luminescent sensing.
1
2
Figure 1. Structures of the two synthesized ruthenium(II) complexes
Complexes 1 and 2 were prepared by a known procedure [3]. Uv-vis absorption, steady-state and
time-resolved emission of these complexes were investigated in PBS aqueous solutions. The
binding constants of indicator dye (1) to copper(II) or mercury(II) were found to be on the order of
105 M–1 by absorption and emission measurements (Figure 2). The supramolecular LmMn complex
stoichiometry was calculated to be 1:1 for Hg(II) and 2:1 for Cu(II) from the fitting of equations I
and II to both the absorption and emission spectra in the presence of each metal ion at controlled pH
[4].
1
350
0.8
0.035
[Cu(II)]
0.03
0.7
0.9
0.8
300
I/Io
0.025
0.5
0.015
0.4
A
0.01
0.4
0.005
0.3
200
0.3
0.00E+00
2.00E-06
Experimental
Fit
4.00E-06 6.00E-06
[Cu(II)] (M)
8.00E-06
1.00E-05
150
0
0.0E+00
5.0E-06
Experimental
0.2
0.1
0
200
0.6
250
0.02
I (a.u.)
0.5
∆ A 325
0.7
0.6
Fit
1.0E-05 1.5E-05
[Cu(II)] (M)
2.0E-05
2.5E-05
100
50
[Cu(II)]
0
300
400
500
wavelength (nm)
600
700
500
550
600
650
700
750
800
wavelength (nm)
Figure 2. Absorption and emission spectra of 1 upon addition of copper(II) inn PBS. Inset: Binding constants
determination using equations I and II for absorbance and emission data, respectively.
137
Equations I and II were derived for a 2:1 supramolecular LmMn ligand-to-metal stoichiometry of the
complex from the absorption and emission data, respectively, and provided the binding constants
with a good fitting of the experimental data.
[
]
[
]
∆A
∆ε K Cu 2 + + ∆ε12 β12 Cu 2 + [Ru ( phen) 2 (iip )]
= 11 1
b[ Ru ( phen) 2 (iip )]t
1 + K1 Cu 2 + + 2β12 Cu 2 + [Ru ( phen) 2 (iip )]
[
[
]
]
[
]
[ ]
[ ]
F 1 + αK1 Cu 2 + + γβ12 Cu 2 + [Ru ( phen) 2 (iip )]
=
F0
1 + K1 Cu 2 + + 2 β12 Cu 2 + [Ru ( phen) 2 (iip )]
[
]
(I)
(II)
To evaluate whether the observed quenching mechanism is dynamic or static, the lifetimes of the
ruthenium complex 1 in phosphate pH = 7,5 buffered solution were measured by SPT, in the
presence of increasing amounts of copper(II). Figure 3 shows that a static quenching occurs, since
the lifetime of the luminophore 1 remains virtually the same (0,58 µs) even in the presence of 3
equivalents of analyte.
4
3.5
τ0/τ or I0/I
3
2.5
2
1.5
1
0.5
0
5
10
15
20
-6
25
30
-1
[Cu (II)] (x 10 mol.L )
Figure 3. Plot of the normalized values obtained for lifetimes ( ) and emission ( ) (λem = 605 nm) of a phosphate
buffered solution (pH = 7.5) of the ruthenium complex 1 (concentration of 1 x 10-5 mol L–1) with increasing copper(II)
concentrations.
Acknowledgements. This project is being funded by the Madrid Community (IV PRICYT CM-S-505/AMB/0374), the
Eur. Regional Development Fund, the Eur. Social Fund, the Spanish Ministry of Science and Innovation (CTQ200628331-E/BQU and TRA2007-30965-E) and the UCM-B. Santander (GR58-08-910072). G.O. gratefully acknowledges
reception of a I3 Intensification of Research grant from the Madrid Community.
References
[1]
[2]
[3]
[4]
138
G. Orellana, D. Garcia-Fresnadillo, Springer Ser. Chem. Sens. Biosens. 2004, 1, 309.
G. Orellana, D. Haigh, Curr. Anal. Chem. 2008, 4, 273.
H. Szmacinski, E. Terpetschnig, J. R. Lakowicz, Biophys. Chem. 1996, 62, 109.
K. A. Connors, Binding Constants: The Measurements of Molecular Complex Stability, 1987.
A Combined Spectroscopic and Theoretical Study of Propofol and its Hydrated
Clusters
I. León1, E. J. Cocinero1, J. Millán2, A. Lesarri3, F. Castaño1 and J. A. Fernández1
1
Dpto. Química Física, Fac. Ciencia y Tecnología, Universidad del País Vasco, Bº Sarriena, s/n, 48940, Bilbao, Spain.
Dpto. Química, Fac. de Ciencias, Estudios Agroalimentarios e Informática, Universidad de La Rioja, Madre de Dios
51, 26006, Logroño, La Rioja, Spain.
3
Departamento de Química Física y Química Inorgánica,Facultad de Ciencias, Universidad de Valladolid, E-47005
Valladolid, Spain.
2
Nowadays it is commonly admitted that anaesthetic action proceeds by directly binding to protein
targets, but the identity of the protein receptors and binding sites is still uncertain in most cases. The
existence of key amino acids suggests that the anaesthetic-receptor interaction can be modelled by
studying separately the interactions that take place in the active site between specific residues of
amino acids and the anesthetic.
The inherent conformations and 3D structures of propofol, and their interactions with bound water
molecules and of the homodimer are being characterised through resonant two photon ionization
(R2PI) spectroscopy coupled with ultraviolet (UV-UV) and infrared ion dip spectroscopy (IRID)
conducted in an adiabatic expansion in the gas phase and DFT/ab initio computation. Analysis of
their preferred structures has revealed the delicately balanced contributions of intramolecular
interactions which control their conformational choice and selectivity..
139
Laser ablation of metallic targets
J. I. Apiñániz, R. Martínez1, F. Castaño
Departamento de Química Física, Facultad de Ciencia y Tecnología and 1Facultad de Farmacia.
Universidad del País Vasco
Most part of technological applications derived from laser ablation is related with kinetic energy
acquired by neutral and ionized species. High values of that energy permit implantation/deposition
on a substrate which can acquire different physical and/or chemical properties [1].
It has been stated that electrons are responsible for ion production through electron-impact
ionization and electron-ion recombination [2], but ion-ion reactions have been also observed (fig.
1).
Al /AlTotal (%)
100
+
Z+
Al
2+
Al
3+
Al
50
0
0
500
1000
Kinetic energy (eV)
Figure 1. Relative populations of AlZ+ in a plume produced by ablation of metallic Al at 5.0 J/cm2.
All these processes are faster than pulse laser duration and a clear interaction between ejected and
generated species in the plume with the tail of the laser is produced. As result, total energy of the
ablated material increases.
This work focuses on how total energy for ions produced in ablation laser can be measured, and its
dependence with temperature, expansion factors and repulsive forces produced by intense fields in
the plume of ablation. Moreover ions are subjected to a sequential ionization process where
electrons are active species. Taking Cu as an example:
Cu 0 ↔ Cu + + e −
Cu + ↔ Cu 2+ + e −
..........
Population of neutrals, ions and electrons are dependent of equilibrium and rate constants (direct
and reverse) modifying Saha´s equation:
140
n e .n
3 / 2 Q + (T )
 χ 
Cu + = 2(2πmkT )
. Cu
exp −

3
n 0
Q
(
T
)
 kT 
h
Cu
Cu 0
(I)
where Qi and χ are partition functions and ionization potential.
We have measured total kinetic energy of ions produced by laser ablation of metallic targets: Al, Cu
and Co. Kinetic energy distributions are compared with that model of sequential ionization with
electrons, where reaction times are in picoseconds range, and consequently are fasters that the pulse
laser [3].
References
[1] C.R. Phipps, Laser Ablation and its Applications. Springer 2007.
[2] J.I. Apiñániz, B. Sierra, R. Martínez, A. Longarte, C. Redondo, F. Castaño, J. Phys. Chem. C 112 (2008) 16556.
[3] S. Amoroso, R. Brúcese, X. Wang, N.N. Nedialkov, P.A. Atanasov, J. Phys. D: Appl. Phys. 40 (2007) 331.
141
Study of the interaction of high intensity laser radiation with metals
P. Écija, R. Martínez, F.J. Basterretxea, M.N. Sánchez Rayo, and F. Castaño
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48940
Leioa, Spain.
In this work, we present the experimental results of the study of the interaction of nanosecond and
femtosecond laser pulses with metals by means of ion Kinetic Energy Distribution (KED)
technique.
In simple words, the process can be understood as follows. The electric field of the laser produces
the electron extraction and the charge division into the sample. At the same time, the magnetic field
produces the spinning of the supplied electrons provided by the earth connection around the ions.
Once the electric field reaches the threshold value, the ions leave the sample as a whole, i.e., a
Coulomb explosion is produced.
The KED technique shows the existence of the resident time of the ions before ejection. The
presence of sidebands in the experimental energy distributions, indicates that ion/atom electron
collisions causing ionization and/or recombination close to the metal surface take place.
The results supply the description of the laser radiation-metal interaction dynamics, and suggest a
new method to calculate the relative rates constants of the recombination and ionization processes.
electrons
(a)
Atom/ion ν
Laser,
ns
E14
E12
E13
E-10
EEE8
9
7
Logarithmic Time Scale (s)
E11
(b)
E6
electrons
Laser, fs
E14
Atom/ion ν
E13
E12
E11
E-10
EEE8
9 Time Scale
Logarithmic
(s) 7
E6
Time dynamics of the laser-metal interaction with (a) nanosecond and (b) femtosecond pulses.
142
Photophysics and Photodissociation Dynamics of 1-Iodonaphthalene
Raúl Montero1, Alvaro Peralta Conde1, Maria E. Corrales2, Luis Bañares2, Fernando Castaño1 and Asier Longarte1
1
Departamento de Química-Física, Facultad de Ciencia y Tecnología,
Universidad del País Vasco, Apartado 644, ES-48080 Bilbao, Spain
2
Departamento de Química-Física, Facultad de Química,
Universidad Complutense de Madrid, 28040 Madrid, Spain
The photophysics and C-I bond dissociation dynamics of jet cooled 1-Iodonaphthalene (NpI) has
been investigated by means of mass resolved transient ionization, after excitation to the first two
ππ* absorption bands at 317 and 267 nm respectively. Signals were collected from the parent NpI+
and from the isobaric naphthil (Np) and iodine fragment cations.
NpI+ decays exhibit a complicated multiexponential character with five lifetimes in the picofemtosecond scale. The analysis of the data provided by this study together with previous reported
observations, allow us to identify for the 267 nm excitation a direct dissociation channel with a
lifetime of 300 fs along the repulsive singlet nσ* state. Simultaneous excitation at this wavelength
of the 1La ππ* lead to a parallel ultrafast conical intersection mediated relaxation process (25 fs) to
the lower 1Lb ππ*, and later to the nearby triplet ππ* states (2 and 20 ps).
NpI+
1
λpump =267 nm
Ion signal (a.u.)
λprobe =800 nm
0
-400
-200
0
200
400
600
800
1000
Time (fs)
Figure 1. Short time scale transient of NpI+ recorded after pumping at 267 nm and probing with 800 nm (dots), and
1+4’ non-resonant ionization transient of ethylene (open circles). Solid lines represent the components of the rate
equations model used to fit the transient (see text).
143
Laser Interference Lithography for the creation of regular nanoarrays
C. Redondo, B. Sierra, D. Navas, F. Castaño
Dpto. Química Física, Fac. Ciencia y Tecnología, Universidad del País Vasco, Bº Sarriena, s/n, 48940, Bilbao, Spain.
During the last two decades, the development of new techniques has opened the possibility to
prepare devices with low dimensionality (1D and 2D). These systems have allowed the observation
of new chemistry and physics properties which could be used in Nanotechnology applications.
Lithography processes, such as nanoimprint lithography, X-ray lithography, extreme ultraviolet
lithography, e-beam lithography, magnetolithography and scanning probe lithography, have been
shown as the widely used techniques for nanostructures preparation [1, 2]. Some of these emerging
techniques have been successfully used in small-scale commercial and important research
applications.
The primary focus of this work is the design and implementation of an interference lithographic
system (IL) which produces periodic patterns (Figure 1). Several steps such as spin-coating of an
anti-reflecting and photoresist layers, exposure the bi-layer stack to radiation and the developing of
the photoresist have been optimized. Finally, these patterns have been used as masks to grow
nanoline, dot or antidot arrays of ferromagnetic materials such as permalloy by Ion Beam
Sputtering. In these samples, both the nano-element sizes and inter-element distances are well
defined. Magnetic behaviours are controlled by the competition between anisotropy energies such
as magnetocrystalline, shape, magnetoelastic and inter-element interactions. The understanding of
these properties would allow the fabrication of devices with well controlled and known properties
for different applications such as magnetic media.
λ= 325 nm
PR (200 nm)
ARC (80 nm)
SiO2 (35 nm)
Si
Figure 1.-Schematic process of the preparation of a
nanoline array with a λ=325nm laser
References
[1] K.K. Berggren, A. Bard, J. L. Wilbur, A. G. Helg, J. D. Gillaspy, J. J. McClelland, S.L. Rolston, W. D. Phillips, M.
Prentiss, G. M. Whitesides, “Microlithography by using neutral metastable atoms and self-assembledmonolayers”,
Science 269, p.1255 (1995).
[2] J. Ferrera, "Nanometer-Scale Placement in Electron-Beam Lithography". Ph.D. Thesis, Massachusetts Institute of
Technology, (2000)
144
Structures of Tropinone in Gas Phase
Emilio J. Cocinero1, Patricia Écija1, José A. Fernández1, Jens-Uwe. Grabow2, Fernando Castaño1 and Alberto Lesarri3
1
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco, 644, 48080 Bilbao,
Spain.
2
Institut für Physikalische Chemie, Lehrgebiet A, Universitä t Hannover, Callinstraße. 3-3A, D-30167 Hannover,
Germany.
3
Departamento de Química-Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo del
Prado de la Magdalena s/n 47005 Spain.
The tropane bicycle is the common structural motif of a series of relevant alkaloids used as
antocholinergics and neurostimulants, including both natural compounds (i.e., atropine,
scopolamine and cocaine) and synthetic analogues used in medicinal Chemistry. Structure-activityrelationship (SAR) studies have revealed correlations between biological properties and several
aspects of ligand conformation, including not only the nature, position and orientation of the aryl
substituents of tropane but also different connections between stereochemistry and bioactivity.
Tropinone (8-methyl-8-azabicyclo(3.2.1)octan-3-one) was chosen for the first study since it
is the pivotal compound for the synthesis of larger alkaloids. The Tropinone was vaporized heating
at 95º C and was diluted into an expanding stream of Ne forming a supersonic jet, where the
vaporized products were probed by time-domain rotational Spectroscopy. Two conformers of
Tropinone (axial and equatorial) were identified in the rotational spectrum. All 13C-monosubstituted
isotopomers were detected in natural abundance (1,1%) for both conformers. Furthermore,
isotopomers containing 15N (0.4%) and 18O (0.2%) were also observed for the equatorial species in
natural abundance. The effective and substitution structures were determined for both conformers of
Tropinone.
Conformers observed of Tropinone in gas phase
145
New Organic-Inorganic Host for the Sensitized Luminescence of Lanthanides
and Layered γ-Zirconium Phosphate
Ernesto Brunet, Olga Juanes, Laura Jiménez, and Juan Carlos Rodríguez-Ubis
Departamento de Química Orgánica, Facultad de Ciencias. Universidad Autónoma de Madrid,
28049-Madrid (Spain)
The preparation of phosphors or luminescent powders is an active research field because the
resulting products may find immediate applications in many technological areas
(telecommunications, solar energy, artificial photosynthesis, lighting, displays, photo-signalled
molecular recognition, biotechnology, medical diagnostics, bio-imaging, etc) related to the broad
concept of photonics, the science and technology for mastering the interaction of light with
matter.[1] To this effect, the sharp and intense luminescence of lanthanides due to their ff electronic
transitions has lots of basic and applied research implications;[2] yet direct lanthanide excitation
produces weak emission owing to metal’s low molar absorptivity. Significantly enhanced emission
can in turn result when the lanthanides form complexes with organic ligands where the latter
assume the role of efficiently absorbing light and transferring the energy to the metal.
Our group has developed a large body of organic molecules based on different chromophores which
efficiently exerted the so-called antenna effect.[3] Another activity deals with the building of
organic-inorganic scaffolds based in zirconium phosphate in its γ form (γ-ZrP; Figure 1) which
reveals as a very versatile carving board where organic phosphonates and other phosphorous
functions are covalently attached by topotactic exchange. One of the strongest points of layered γZrP is its use as 2D template to build 3D materials with aprioristic knowledge of its structure. In
short, laminar γ-ZrP contains two different kinds of phosphates, one internal which sustains the
integrity of the layers, and another in the lamellae surface pointing to the interlayer region, which
can be exchanged by mild hydrothermal processes with other phosphorous functions topotactically,
i.e. maintaining intact the layered structure.[4] Previous work published by us evidences that
pillared γ-ZrP with suitable chromophores and polyoxygenated chains may constitute a good
accommodation for the sensitized emission of lanthanides [5].
Figure 1. Idealized model for γ-ZrP-BTP
In this communication we describe the incorporation into γ-ZrP by topotactic exchange, of a new
chromophore, {2,2´-[4,4´-(pyridine-2,6-diyl)bis(1H-1,2,3-triazol-1,4-diyl)bis(ethane-1,2-diyl) bisphosphonic acid; BTP} synthesized by “click-chemistry” procedures from dithynylpyridine
(Scheme 1). The resulting material has been tested as a solid host to efficiently sensitize the
emission of Europium (III) and Terbium (III) ions, introduced into the host by intercalation process.
146
Scheme 1. Synthetic route for BTP ligand (2,2´-[4,4´-(pyridine-2,6-diyl)bis(1H-1,2,3-triazol-1,4-diyl)bis(ethane-1,2diyl)]bisphosphonic acid)
The luminescence measurements of these materials in the solid state (Figure 2) did show the typical
structured emission of Ln3+, and the excitation spectrum displayed bands at 300-310 nm close to
that belonging to the free organic ligand, strongly suggesting that the bis-triazolylpyridine
chromophore performs the pursued antenna effect when covalently bonded to the galleries of γ-ZrP.
1.2
1
Arbitrary intensity
Tb emission
Tb excitation
0.8
Eu emission
Eu excitation
0.6
Ligand absorption
0.4
0.2
0
200
300
400
500
600
700
800
Wavelength (nm)
Figure 2. Emission and excitation spectrum of the solid γ-ZrP-BTP containing ca. 20 ions of Tb3+ (green) and Eu3+
(red) per 100 Zr atoms. λexc=300 nm.
References
[1] Escribano, P.; Julian-Lopez, B.; Planelles-Arago, J.; Cordoncillo, E.; Viana, B.; Sanchez, C. J. Mater. Chem. 2008,
18, 23-40.
[2] Brunet, E.; Rodriguez-Ubis, J.C.; Juanes, O., Curr. Chem. Biol. 2007, 1, 11-39.
[3] (a) Rodríguez-Ubis, J. C.; Sedano, R.; Barroso, G.; Juanes, O.; Brunet, E. Helv. Chim. Acta 1997, 80, 372-387; (b)
Takalo, H.; Mukkala, V. M.; Merio, L.; Rodríguez-Ubis, J. C.; Sedano, R.; Juanes, O.; Brunet, E. Helv. Chim. Acta
1997, 80, 372-387; (c) Azèma, J.; Galaup, C.; Picard, C.; Tisnès, P.; Ramos, P.; Juanes, O.; Rodríguez-Ubis, J. C.;
Brunet, E. Tetrahedron 2000, 56, 2673; (d) Brunet, E.; Juanes, O.; Sedano, R.; Rodríguez-Ubis, J. C. Org. Lett, 2002, 4,
213-216; (e) Brunet, E.; Juanes, O.; Rodríguez-Blasco, M. A.; Garayalde, D.; Rodríguez-Ubis, J. C. Tetrahedron Lett.
2005, 46, 7801-7805; (f) Brunet, E.; Juanes, O.; Sedano, R.; Rodriguez-Ubis, J. C. Tetrahedron Lett. 2007, 48, 10911094; (g) Brunet, E.; Juanes, O.; Rodriguez-Blasco, M. A.; Pereira, S.; Rodriguez-Ubis, J. C. Tetrahedron Lett. 2007,
48, 1353-1355.
[4] Alberti, G., in Comprehensive Supramolecular Chemistry, Alberti, G. and Bein, T. eds., Pergamon, New York,
1996, vol. 7, p. 151; Clearfield A. and Costantino, U. ibid, p. 107.
[5] Brunet, E.; Mata, M. J.; Juanes, O.; Rodríguez-Ubis, J.C. Chem. Mater. 2004, 16, 1517-1522.
147
Photochemically Initiated Reaction of CF3CH2CHO with OH Radicals between
263 and 358 K
M. Antiñolo, E. Jiménez, J. Albaladejo
Departamento de Química Física. Universidad de Castilla-La Mancha. 13071 Ciudad Real, Spain
The great impact of the chlorofluorocarbons (CFCs) on the ozone (O3) layer was discovered at the
end of last Century. After the Montreal Protocol in 1987 hydrochlorofluorocarbons and
hydrofluorocarbons (HCFCs and HFCs) were presented as good substitutes of CFCs because of
their shorter tropospheric lifetimes, mainly due to the reactivity towards hydroxyl (OH) radicals.
Therefore, these halogenated compounds neither reach stratosphere nor destroy O3 layer. However,
a negative consequence of the use of HCFCs and HFCs is their significant contribution to the
Global Warming [1]. For that reason, other compounds with lower global warming potentials
(GWPs), such as fluorinated alcohols (FAs), have recently been proposed as CFCs substitutes.
These FAs are mainly removed in the troposphere by OH radicals and chlorine atoms [2-5].
Recently, product studies on the reaction of OH and Cl with CF3(CH2)x=0,1CH2OH have confirmed
that the corresponding fluorinated aldehydes, CF3CHO and CF3CH2CHO, are major products both
in the presence and the absence of NOx [2-5]. In general, aldehydes constitute an important source
of free radicals in the troposphere, and can also be precursors of secondary organic aerosol and
ozone. Therefore, the knowledge of the atmospheric fate of fluorinated aldehydes is needed in order
to evaluate if fluorinated alcohols are good substitutes of HFCs and HCFCs. In this work, the
kinetics of the photooxidation of CF3CH2CHO initiated by OH radicals has been performed as a
function the temperature by using the Laser Pulsed Photolysis (PLP) and the Laser Induced
Fluorescence (LIF) techniques.
CF3CH2CHO + OH Products
kOH(T=263-358 K)
(1)
Rate coefficients kOH for CF3CH2CHO have only been reported at room temperature and mainly by
relative techniques (RR) as shown in Table 1. As the temperature decreases with altitude in the
troposphere, the knowledge of kOH at temperatures below 298 K are essential to better evaluate the
atmospheric fate of these species.
Table 1. Previous kinetic data on the reaction of OH radicals and CF3CH2CHO
pT/ Torr
100
700
760 ± 7
kOH(298 K)/ 10-12 cm3 molecule-1 s-1
2,96 ± 0,04
2,57 ± 0,44
3,60 ± 0,30
Technique
PLP-LIF
RR/ FTIR
RR/GC-FID/ FTIR
Reference
3
4
6
References
[1] S. A. Montzka and P. J. Fraser (Lead Authors), Chapter 1 in “Scientific Assessment of Ozone Depletion: 2002”,
2003. Report No. 47, WMO, Geneva.
[2] V. C. Papadimitriou, A. V. Prosmitis, Y. G. Lazarou, P. Papagiannakopoulos, J. Phys. Chem. A, 107 (2003) 3733.
[3] T. Kelly, V. Bossoutrot, I. Magneron, K. Wirtz, J. Treacy, A. Mellouki, H. Sidebottom, G. Le Bras, J. Phys. Chem.
A, 109 (2005) 347.
[4] M. D. Hurley, J. A. Misner, J. C. Ball, T. J. Wallington, D. A. Ellis, J. W. Martin, S. A. Mabury, M. P. Sulbaek
Andersen, J. Phys. Chem. A, 109 (2005) 9816.
[5] V. C. Papadimitriou, D. K. Papanastasiou, V. G. Stefanopoulos, A. M. Zaras, Y. G. Lazarou, P.
Papagiannakopoulos, J. Phys. Chem. A, 111 (2007) 11608.
[6] S. R. Sellevåg, T. Kelly, H. Sidebottom, C. J. Nielsen, Phys. Chem. Chem. Phys. 6 (2004) 1243.
148
LIST OF PARTICIPANTS
149
150
Acuña , A. Ulises
Instituto de Química Física
RocasolanoC.S.I.C.
Bonancía, Paula
Universidad Politécnica de Valencia
[email protected]
[email protected]
Aguado Caballero, Edurne
Bordello Malde, Jorge
Universidade de Santiago de Compostela
[email protected]
[email protected]
Aguilera Sigalat, Jordi
Instituto de Ciencia Molecular (ICMol)
Bourdelande, José Luis
Universidad Autónoma de Barcelona
[email protected]
[email protected]
Al-Soufi, Wajih
Braslavsky, Silvia E.
Max Planck Institut fuer Bioanorganische
Chemie (Germany)
[email protected]
[email protected]
Alvarez Pez, José María
Universidad de Granada
Brunet Romero, Ernesto
Universidad Autónoma de Madrid
[email protected]
[email protected]
Albadalejo Pérez, José
Universidad de Castilla-La Mancha
Caballero Millán, Alegría
[email protected]
[email protected]
Amat Guerra, Francisco
Instituto de Química Orgánica General, CSIC
Calvo Prieto, Silvia
[email protected]
[email protected]
Apiñániz Aginako, Jon Imanol
Camarasa, Marta
Universitat Ramon Llull
[email protected]
[email protected]
Arbeloa, Teresa
Campos García, Pedro José
[email protected]
[email protected]
Bañuelos Prieto, Jorge
Carmona Pérez, Thais
Universidad de Alcalá
[email protected]
[email protected]
Basterretxea, Francisco José
Castaño, Fernando
[email protected]
[email protected]
Bertolotti, Sonia
Universidad Nacional de Río Cuarto
(Argentina)
Cerdán Luis
Instituto de Química Física Rocasolano
[email protected]
[email protected]
Cohen, Boiko
Universidad de Castilla-La Mancha
[email protected]
151
Collado Martín, Daniel
Universidad de Málaga
García-Díaz, María
[email protected]
[email protected]
Corcóstegui, Cecilia
García-Moreno, Inmaculada
Instituto de Química Física, Rocasolano
[email protected]
[email protected]
Costela, Angel
Instituto de Química Física, Rocasolano
Gomes Silva, Cláudia
Instituto de Tecnología Química
UPV-CSIC
[email protected]
[email protected]
Crovetto González, Luis
University of Granada
[email protected]
Gómez Mendoza, Miguel
Instituto Universitario Mixto de Tecnología
Química (CSIC-UPV)
De Miguel, Maykel
[email protected]
[email protected]
González Izquierdo, Jesús
Universidad Complutense de Madrid
Durán-Sampedro, Gonzalo
[email protected]
[email protected]
Granadero Rey, Daniel
Universidad de Santiago de Compostela
Ecija, Patricia
[email protected]
[email protected]
Hernando Campos, Jordi
Universitat Autònoma de Barcelona
Encinas, Susana
[email protected],
[email protected]
Hofkens, Johan
Katholieke Universiteit Leuven (Belgium)
Fernández, José Andrés
[email protected]
[email protected]
Izquierdo Arcusa, María Angeles
Universidad Jaume I
Galindo, Francisco
Universidad Jaume I
[email protected]
[email protected]
Jiménez Molero, María Consuelo
Gallardo, Adaya
[email protected]
[email protected]
Juanes Recio, Olga
García, Hermenegildo
[email protected]
[email protected]
Lemp, Else
Universidad de Chile (Chile)
García Norman A.
Universidad Nacional de Río Cuarto
(Argentina)
[email protected]
[email protected]
León, Iker
[email protected]
152
Longarte, Asier
Montero, Raúl
[email protected]
[email protected]
López Arbeloa, Fernando
Nardi, Giacomo
[email protected]
[email protected]
López Arbeloa, Iñigo
Universidad del País Vasco UPV/EHU
Navas, David
[email protected]
[email protected]
López Gejo, Juan
Nonell, Santi
[email protected]
[email protected]
López Poyato, José Manuel
Novo Rodríguez, Mercedes
[email protected]
[email protected]
Marazzi, Marco
University of Alcalá
Nuin, Edurne
[email protected]
[email protected]
Martín Alvarez, Cristina
Universidad de Castilla La Mancha
Orellana, Guillermo
[email protected]
[email protected]
Martín García, Esperanza
Orte Gutierrez, Angel
[email protected]
[email protected]
Martín Torres, Virginia
Instituto de Química-Física
“Rocasolano” (CSIC)
Ortiz García, Mª José
[email protected]
[email protected]
Martínez Martínez, Virginia
Palacios Cuesta, Marta
[email protected]
[email protected]
Martínez Pérez de Mendiola, Roberto
Palumbo, Fabricio
[email protected]
[email protected]
Miñambres Durán, Lorena
Passarelli, Vincenzo
Universidad de Almería
[email protected]
[email protected]
Miranda Alonso, Miguel Angel
Peralta Conde, Alvaro
[email protected]
[email protected]
153
Pérez-Inestrosa, Ezequiel
[email protected]
Salleres Alonso, Sandra
[email protected]
Pérez-Ojeda, Mª Eugenia
Instituto de Ciencia y Tecnología de
Polímeros (CSIC)
Sampedro, Diego
[email protected]
[email protected]
Pintado Sierra, Mª Mercedes
Instituto Quimica Fisica Rocasolano (CSIC)
Sánchez Rayo, Mª Nieves
[email protected]
[email protected]
Pischel Uwe
Universidad de Huelva
Santos, André
[email protected]
[email protected]
Pocoví Martínez, Salvador
Instituto de Ciencia Molecular (ICMOL)
Serrano-Andrés, Luis
Universitat de Valencia
[email protected]
[email protected]
Redondo, Carolina
Universidad del País Vasco (UPV)
Sierra, Borja
[email protected]
[email protected]
Reyman, Dolores
Soldevilla, Sonia
[email protected],
[email protected]
Rivado , Laura
Suau, Rafael
[email protected]
[email protected]
Rodríguez Agarrabeitia, Antonia
Synak, Anna
Universidad de Castilla La Mancha
[email protected]
[email protected]
Rodríguez Barranco, Miguel Angel
Talavera, Eva
[email protected]
[email protected]
Rodríguez-Ubis, Juan Carlos
Veiga Gutierrez, Manoel
[email protected]
[email protected]
Ruedas Rama, María José
University of Granada
Veloso Fernández, Antonio
Universidad del País Vasco (UPV)
[email protected]
[email protected]
Ruiz, Rubén
Zanocco, Antonio
Universidad de Chile (Chile)
[email protected]
[email protected]
154
155

BOOK OF ABSTRACTS - Grupo especializado de Fotoquímica

Transcription

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