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A theoretical model describing photophysics of π-conjugated aggregates, such as molecular crystals and polymer thin films, is developed. A Holstein-like Hamiltonian expressed with a multi-particle basis set is used to evaluate absorption and photoluminescence (PL) spectra of neutral excitons as well as charge modulation spectra (CMS) and transient absorption spectra (TAS) of positively charges hole-type polarons. The results are used to develop a better theoretical understanding of the organic electronics being studied and their photophysics, and also to probe the morphology of poly(3-hexylthiophene) (P3HT) thin films, which are used in photovoltaic devices. / Chemistry

El objetivo principal de esta tesis es contrastar el papel de dichos compuestos 1,3-dicarbonilicos como agentes que dañan el ADN con respecto a su potencial fotoprotector. Primero, 5,6-dihidropirimidinas han sido derivatizadas utilizando el grupo fotolábil t-Bu cetona con el fin de estudiar la generación de radicales en C5 en un medio no acuoso. Después, el estudio por fotólisis de destello láser en ACN de los derivados 1,3-dicarbonilicos diseñados da lugar a la detección de los supuestos radicales 5,6-dihidropirimidin-5-ilo. Su caracterización muestra especies transitorias de vida larga y están centrados a 400-420 nm o 350-400 nm para los derivados 5,6-dihidrouridina o 5,6-dihidrotimidina, respectivamente. Además, la generación de radicales también se ha evidenciado mediante experimentos de fluorescencia en estado estacionario mediante el uso de una sonda profluorescente (AAA-TEMPO) que atrapa el radical. Por lo tanto, la irradiación de los derivados fotolábiles del ácido nucleico en presencia de AAA-TEMPO produce un aumento de la emisión, de acuerdo con la captura del radical C5 por la sonda paramagnética. La formación del aducto se ha confirmado mediante UPLC-HRMS. Los datos experimentales se han corroborado con cálculos teóricos ab initio CASPT2 // CASSCF. Segundo, otro derivado 1,3-dicarbonílico de la pirimidina se ha investigado. De hecho, el daño 5-formiluracilo (ForU) presenta características interesantes como potencial agente fotosensibilizador intrínseco del ADN. Por lo tanto, los estudios espectroscópicos revelan que ForU tiene una absorción en el rango UVA/UVB y también presenta un estado triplete excitado (3ForU *) con un tiempo de vida algunos micros y con una ET suficientemente alta como para fotosensibilizar la formación de los conocidos dímeros de pirimidina de tipo ciclobutano (CPDs) a través de una transferencia de energía triplete-triplete. Este proceso ha sido confirmado por medio de la síntesis de díadas modelo Thy-Thy y Cyt-Cyt, ya que su irradiación en presencia de ForU ha demostrado que producen CPDs. Asimismo, el estudio en ADN plasmídico permitió establecer la capacidad de ForU para inducir roturas de cadena simple y CPDs. A continuación, se ha desarrollo una nueva estrategia para la fotoprotección de moléculas bioactivas aprovechando la reactividad fotoquímica del tautómero 1,3-dicetona de la avobenzona (AB), un filtro del UVA. Los compuestos seleccionados son dos fármacos antiinflamatorios no esteroideos de uso tópico con propiedades fotosensibilizantes, (S)-ketoprofeno (KP) y diclofenaco (DF). El tautómero dicetona de la AB contiene dos restos fenacilo, que es un grupo protector fotolábil muy establecido. Por lo tanto, un diseño juicioso de una díada profármaco/profiltro permite la fotoliberación del fármaco y de su protector, la AB. La viabilidad de esta liberación controlada de los ingredientes se verificó en diferentes disolventes con carácter dador de H y viscosidad para simular la formulación tópica. Además, los estudios de fotólisis de destello láser en EtOH permiten la caracterización de una especie transitoria a 400-420 nm, la cual ha sido asignada al estado excitado triplete de AB-KP. Finalmente, se ha evaluado la fotoseguridad de la díada fotoactivable AB-KP. Los espectros de absorción transitoria de la díada AB-KP en ciclohexano muestra que la especie observada es el estado excitado triplete del KP y no el de la AB en su forma dicetona. El impacto de la díada sobre la membrana celular se ha abordado mediante irradiación UVA de soluciones de ácido linoleico en presencia de AB-KP y su potencial fototóxico se ha evidenciado mediante espectrofotometría UV-Vis revelando la formación de derivados hidroperóxidos diénicos conjugados del ácido linoleico. Sin embargo, la diada AB-KP no exhibe un potencial fotogenotóxico como lo demuestran los experimentos del ensayo comet, donde a diferencia del KP, la forma redonda no / The main objective of this thesis is to contrast the role of these 1,3-dicarbonyl compounds as DNA damaging agents to their photoprotective potential. Firstly, 5,6-dihydropyrimidines have been derivatized using a tert-butyl ketone photolabile group in order to study the generation of C5-centered radicals in non aqueous media. Then, laser flash photolysis study in acetonitrile of the designed 1,3-dicarbonyl derivatives yields the formation of the purported 5,6-dihydropyrimidin-5-yl radicals. Their characterization shows long lived transient species, which do not decay in the µs range and are centered at 400-420 nm or 350-400 nm for the 5,6-dihydrouridine or 5,6-dihydrothymidine derivatives, respectively. Moreover, radical generation has also been evidenced by steady state fluorescence experiments by using a profluorescent radical trap (AAA-TEMPO). Thus, irradiation of the photolabile nucleic acid derivatives in the presence of AAA-TEMPO results in an increased emission, in agreement with the trapping of C5 radical by the paramagnetic probe. Formation of the resulting adduct has been confirmed by UPLC-HRMS. Experimental data have been corroborated with ab initio CASPT2//CASSCF theoretical calculations. In a second chapter, another 1,3-dicarbonyl derivative of pyrimidine has been investigated. Indeed, 5-formyluracil (ForU) presents interesting features as a potential intrinsic DNA photosensitizing agent. Thus, spectroscopic studies reveal that ForU has not only an absorption in the UVA/UVB range, but also a triplet excited state (3ForU*) with a lifetime of some micros and with an energy high enough to photosensitize the well-known cyclobutane pyrimidine dimers (CPDs) through triplet-triplet energy transfer. This process has been confirmed by means of the synthesis of model Thy-Thy and Cyt-Cyt dyads, which after irradiation in the presence of ForU have been demonstrated to produce CPDs. Finally, the study extended to plasmid DNA allows establishing the ability of ForU to produce single strand breaks and CPDs. Next, the attention has been focused on the development of a new strategy for photoprotection of bioactive molecules taking advantage of the photochemical reactivity of the 1,3-diketo tautomer of the UVA filter avobenzone (AB). The selected bioactive compounds are two photosensitive topical non steroidal anti-inflammatory drugs, (S)-ketoprofen (KP) and diclofenac (DF). In this context, the diketo tautomer of avobenzone contains two phenacyl moieties, which are well-known photoremovable protecting groups. Thus, a judicious design of a pro-drug/pro-filter dyad allows the photorelease of the drug and its protecting shield, avobenzone. The viability of this controlled release of the active ingredients was checked in different solvents of different H donating properties and viscosity to simulate topical formulation.Plus, laser flash photolysis studies in ethanol allow characterization of a transient absorption band at 400-420 nm assigned to the triplet excited state of the dyad by comparison with that of the diketo form of AB. Finally, the photosafety of the photoactivatable AB-KP dyad has been assessed. The transient absorption spectra obtained for AB-KP dyad in cyclohexane showed the triplet excited state of KP and not that of the AB in its diketo form. The impact on the cellular membrane has been addressed by UVA irradiation of linoleic acid solutions in the presence of the dyad. Phototoxic potential of the dyad has been evidenced by UV-Vis spectrophotometry through the formation of the conjugated dienic hydroperoxides derived from linoleic acid. However, AB-KP does not exhibit a photogenotoxic potential as demonstrated by comet assay experiments, where by contrast with KP, the non damaged round shape of the cell is still observed after UVA irradiation. / L'objectiu principal d'aquesta tesi és contrastar el paper d'aquests compostos 1,3-dicarbonil com a agents que danyen l'ADN respecte al seu potencial fotoprotector. En primer lloc, 5,6-dihidropirimidines han sigut derivatitzades utilitzant el grup fotolàbil t-Bu cetona amb la finalitat d'estudiar la generació de radicals centrats en C5 en un mitjà no aquós. Després, l'estudi de fotòlisi de flaix làser en acetonitril dels derivats 1,3-dicarbonil dissenyats produeix la formació dels suposats radicals 5,6-dihidropirimidin-5-il. La seua caracterització mostra espècies transitòries de vida llarga i estan centrats a 400-420 nm o 350-400 nm per als derivats 5,6-dihidrouridina o 5,6-dihidrotimidina, respectivament. Per tant, la irradiació dels derivats fotolàbils d'àcid nucleic en presència de AAA-TEMPO dóna com resultat un augment de l'emissió, d'acord amb la captura del radical C5 per la sonda paramagnètica. La formació del adducte resultant s'ha confirmat mitjançant UPLC-HRMS. Així mateix, les dades experimentals s'han corroborat amb càlculs teòrics ab initio CASPT2 // CASSCF. En un segon capítol, un altre derivat 1,3-dicarbonil de la pirimidina ha sigut investigat. De fet, el dany 5-formiluracil (ForU), presenta característiques interessants com a potencial fotosensibilitzador intrínsec de l'ADN. Per tant, els estudis espectroscòpics revelen que ForU té una absorció en el rang UVA/UVB i també presenta un estat triplet excitat (3ForU*) amb un temps de vida d'alguns micros i amb una ET prou alta com per a fotosensibilitzar la formació dels coneguts dímers de pirimidina de tipus ciclobutà (CPDs) a través d'una transferència d'energia triplet-triplet. Aquest procés ha sigut confirmat per mitjà de la síntesi de diades model Thy-Thy i Cyt-Cyt, que després de la irradiació en presència de ForU s'ha demostrat que produeixen CPDs. Finalment, l'estudi en ADN plasmídic ha permès establir la capacitat de ForU per a produir trencaments de cadena simple i CPDs. A continuació, s'ha desenvolupat una nova estratègia per a la fotoprotecció de molècules bioactives aprofitant la reactivitat fotoquímica del tautòmer 1,3-dicetona del filtre de l'UVA Avobenzone (AB). Els compostos seleccionats són dos fàrmacs antiinflamatoris no esteroïdals d'ús tòpic amb propietats fotosensibilizants, (S)-ketoprofè (KP) i diclofenac (DF). En aquest context, el tautòmer dicetona de l'AB conté dues fraccions fenacil, que es un grup protector fotolàbil ben conegut. Per tant, un disseny judiciós d'una diada profàrmac / profiltre permet el fotoalliberament del fàrmac i del seu escut protector, l'AB. La viabilitat d'aquest alliberament controlat dels ingredients actius s'ha verificat en diferents dissolvents de diferent caràcter dador d'hidrogen i viscositat per a simular la formulació tòpica. A més, els estudis de fotòlisi de flaix làser en EtOH permeten la caracterització d'una banda d'absorció transitòria a 400-420 nm, la qual ha sigut assignada a l'estat excitat triplet de AB-KP. Finalment, s'ha avaluat la fotoseguretat de la diada fotoactivable AB-KP. Els espectres d'absorció transitòria de la diada AB-KP en ciclohexà mostres que l'espècie observada és l'estat excitat triplet del KP i no el de la AB en la seua forma dicetònica. L'impacte sobre la membrana cel·lular s'ha abordat mitjançant la irradiació UVA de solucions d'àcid linoleic en presència de AB-KP. El potencial fototòxic de la diada s'ha evidenciat mitjançant espectrofotometria UV-Vis revelant la formació de derivats hidroperòxids diènics conjugats de l'àcid linoleic. No obstant açò, la diada AB-KP no exhibeix un potencial fotogenotòxic com ho demostren els experiments de l'assaig comet, on a diferència del KP, la forma redona no danyada de la cèl·lula encara s'observa després de la irradiació UVA. / Aparici Espert, MI. (2018). Photochemistry of 1,3-Dicarbonyl Compounds: DNA Photodamage vs. Photoprotection [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/105782

The synthesis, characterization and photophysical properties of three Zr-based Metalorganic frameworks (MOFs) assembled from 2,6-anthracenedicarboxylic acid (2,6-ADCA, 2,6- MOF) and 1,4-anthracenedicarboxylic (1,4-ADCA, 1,4-MOF), and 9,10-anthracenedicarboxylic acid (9,10-ADCA, 9,10-MOF) are described. The crystal structure of the 9,10-MOF was elucidated by synchrotron powder X-ray diffraction (PXRD) analysis and is isostructural with the well-known UiO-66 framework. The 2,6-MOFs also form highly crystalline, octahedral-shaped structures and was characterized by PXRD. Le Bail refinement of the powder pattern revealed that the 2,6-MOF also has UiO-type crystal structure. Conversely, incorporation of the 1,4-ADCA ligand results in large rod-shaped crystals. The excited-state properties of the MOFs were examined using steadstate diffuse reflectance, steady-state emission spectroscopy and time-correlated single photon counting (TCSPC) spectroscopy and are compared to those of the corresponding ligand in solution. Both the unique fluorescent properties of the ligand as well as individual framework structure, result in distinctive luminescent behavior and dictate the extent of intermolecular interactions. Specifically, the 2,6-MOF displays monomeric emission with a fluorescence lifetime (t) of 16.6 ± 1.1 and fluorescence quantum yield (Ff). On the other hand, the 1,4-MOF displays both monomeric and excimeric emission, with corresponding lifetime values of 7.5 ± 0.01 and 19.9 ± 0.1, respectively and a quantum yield of 0.002 ± 0.0001. The propensity for photon upconversion through sensitized triplet-triplet annihilation (TTA-UC) was probed in the three anthracene-based MOFs. The MOFs were surface-modified with Pd(II) mesoporphyrin IX (PdMP) as the triplet sensitizer. Upconverted emission from the 9,10-MOF was observed, with a quantum efficiency (FUC) of 0.46 % and a threshold intensity (Ith) of 142 mW/cm2 . The variation of the spacing between the anthracene units in the MOFs was found to have significant impact on TTA-UC. As a result, upconverted emission is only displayed by the 9-10-MOF. The distance between anthracene linkers in the 2,6-MOF are too large for TTA to occur, while the short distances in the 1,4-MOF inhibit upconversion through competitive excimer formation. To further explore the effects of chromophore spacing on energy transfer processes, a series of zinc-based mixed-ligand MOF were constructed from Zn(II) tetrakis(4- carboxyphenyl)porphyrin (ZnTCPP) and pyrazine, 2,2′-bipyridine (pyz) or 4,4′-bipyridyl (bpy) or 1,4-di(4-pyridyl)benzense (dpbz), comprising ZnTCPP/Zn paddlewheel layers. Across this series, the porphyrin spacing was approximately 6 Å, 11 Å and 16 Å for pyz, bpy and dpbz, respectively. The photophysical properties of the MOFs were explored using stead-state diffuse reflectance spectroscopy and steady-state and time-resolved emission spectroscopies. Florescence quenching studies examined the correlation between porphyrin spacing and efficiency of energy transfer. / Ph. D. / Metal-organic frameworks (MOFs) are crystalline materials composed of metal clusters connected by organic molecules. Their modular nature and synthetic tunability allows for rational design of MOFs with different functionalities and has afforded their application in a variety of fields including gas storage and separation, catalysis, optoelectronics, energy conversion and storage, chemical sensing and biomedicine. MOFs provide an ideal platform for studying the structure-property relationships that govern energy-transfer processes. Furthermore, efficient and long-ranging, directional energy transfer has been demonstrated in MOFs. The work presented in this dissertation focuses on MOFs with applications in solar energy conversion schemes. The design and synthesis of photoactive MOFs is described and the effects of their structure on energy-transfer processes is explored. Photovoltaic cells (PVCs) absorb sunlight and convert it into electricity. However, only photons that are high enough in energy are absorbed by the PVC, while the lower energy photons are not absorbed and therefore do not contribute to power production, resulting in decreased efficiency of the solar cell. One approach to enhancing solar cell efficiencies is to collect the lower energy photons and convert them into higher energy photons through a process called sensitized photon upconversion (UC). This process involves a molecule (sensitizer chromophore) that absorbs lower-energy photons and then transfers the absorbed energy to a second molecule (acceptor chromophore), which emits higher-energy photons. In order to understand how to optimize the efficiency of the UC process, we integrated sensitizer and acceptor chromophores into MOFs various molecular arrangements and probed UC in these materials. Close proximity and he appropriate orientation between chromophores resulted in UC from the framework. Natural photosynthetic systems contain highly ordered arrays of chromophores that efficiently absorb sunlight and funnel the energy to a reaction center. Energy-harvesting materials that mimic natural photosynthetic processes also have potential applications in solar energy conversion. Porphyrins are often used in artificial photosynthetic systems because of their similarity to chlorophyll pigments found in nature. In order to design highly efficient artificial photosynthetic systems, we first need to understand how energy transfer processes are influenced by the structure of the system. Therefore, we synthesized a series of MOFs containing Zn=porphyrin layers at varied distances and examined the effects of distance between porphyrin layers on the energy-transfer processes within the MOFs. This work provides insight into the structure-property relationships in photoactive MOFs that can serve as a guide for the rational design of light-harvesting MOFs in future studies.

Sintetizou-se uma nova diimida naftálica difosfônica, a N, N-bis(2-fosfonetil)naftaleno diimida (DPN), pela reação do dianidrido 1,4,5,5-naftálico com o ácido 2-aminoetil-fosfônico. Essa molécula foi caracterizada por H-RMN, micro-análise, titulação potenciométrica e análise de fosfato. Através de estudos fotofísicos e fotoquímicos do DPN em solução verificou-se que essas moléculas encontravam-se na forma monomérica em água e na forma de agregados em solventes orgânicos. Verificou-se que o rendimento quântico de fluorescência Φf dessa molécula é dependente do pH do meio, uma vez que ocorre diminuição do Φf com aumento do pH. Por estudos com fotólise de relâmpago e por experimentos de lente térmica resolvida no tempo, verificou-se que a diminuição do Φf com aumento do pH. Por estudos com fotólise de relâmpago e por experimentos de lente térmica resolvida no tempo, verificou-se que a diminuição Φf é causada principalmente por um aumento no cruzamento intersistema, de singleto a tripleto. Multicamadas à base de zircônio (Mallouk et al. 1987) do DPN foram obtidas substratos como vidro, silício e ouro. O crescimento de filmes em vidro foi acompanhado por espectroscopia de absorção e em filmes sobre o silício por elipsometria. Sobre a superfície de ouro, foram estudadas as propriedades de oxido-redução do filme por voltametria cíclica. Por estudos fotofisicos desses filmes depositados em vidro, verificou-se que os mesmos eram fotoativos, formando produtos fotoquímicos por processos radicalares. Por outro lado, quando se preparou micro-cristais, pricipitando-se o radical do DPN com o zircônio em solução, observou-se por espectroscopia de ressonância de spin eletrônico (EPR) que estas estruturas micro-cristalinas estabilizavam o radical do DPN em presença de ar por vários dias. / The new diimide N, N\' -bis-(2-phosphoethyl)-1,4,5,8-naphtalenediimide (DPN) was synthesized by reaction of 2-aminoethylphosphonic acid with the compound 1,4,5,8-naphatalene tetracarboxylic dianhydride. This molecule was characterized by 1H-RMN, elemental analysis, potentiometric titration and phosphorus analysis. By photophysical and photochemical studies of DPN in solution, it was verified that DPN is in monomeric form in aqueous solution and DPN is in an aggregated state in organic solvents. When the fluorescence spectra in aqueous media show a sharp decrease in the fluorescence quantum yield (Φf) with the increase in pH. By laser flash photolysis and thermal lensing, it was verified that this reduction of Φf with the increase pH can be attributed to an increment in the intersystem crossing processes when the pH increased. The zirconium phosphonate thin films formed from 1,4,5,8-naphtalene diimides were assembled on quartz, borosilicate glass (BK7), silicon or gold. The film growth was followed by absorption spectroscopy on quartz and BK7 and by ellipsometry on silicon substrate. Toe oxidation and reduction properties of the films were studied by cyclic voltammetry of films deposited on gold. Photophysical and photochemical data revealed that the films were photosensitive, giving rise to products derived by radicalar reactions. On the other hand, when the DPN radical was precipitated with Zr4+ in solution, micro-crystals were obtained which stabilized the radical in the presence of air for several days.

Devido à sua intensa absorção de luz na região visível do espectro, as porfirinas e seus derivados (clorinas e bacterioclorinas) são de grande importância na terapia fotodinâmica (TFD) para o tratamento de doenças neoplásicas. Neste trabalho foram sintetizadas as novas vinil-porfirinas estrategicamente funcionalizadas (47 e 48), seguida de uma sistemática de reações de Diels-Alder com dieófilos ativados, com o propósito de obter clorinas e/ou bacterioclorinas para potenciais aplicações em TFD. / Due to their strong absorption in the visible region, porphyrins and related derivatives (chlorins and bacteriochlorins) are very important in photodynamic therapy (PDT) for the treatment of neoplasic diseases. In this work were synthesized the novel and strategically functionalizated vinyl-porphyrins 47 and 48, followed by systematic Diels-Alder reactions with activated dienophiles to obtain chlorins and/or bacteriochlorins, potentially useful on PDT.

O trabalho apresentado nesta Tese tem como objetivo a elaboração de estruturas polinucleares baseadas em clusters trinucleares de rutênio. Os oligômeros estudados são opções interessantes para o desenvolvimento futuro de dispositivos supramoleculares, em função de suas propriedades fotofísicas e eletroquímicas. Um trímero e uma série de dímeros mistos foram obtidos pela combinação do cluster [Ru3O(CH3COO)6(py)2(CH3OH)]+ com complexos [Ru(bpy)2(P)(L)]+ (P = ligante de ponte N-heterocíclico; L = P, Cl ou CN). A caracterização por RMN, voltametria cíclica e espectroeletroquímica dos dímeros onde L = Cl foi utilizada como base na interpretação dos resultados obtidos para os demais complexos; os dados refletem uma interação fraca entre os fragmentos, que depende das características eletrônicas da ponte P. Nos dímeros onde L = CN, ocorre a supressão da emissão do cromóforo [Ru(bpy)2] pelo cluster através de um mecanismo de transferência de elétrons fotoinduzida. Para o cluster na forma reduzida, sugere-se também a ocorrência de transferência de energia. Na segunda parte da Tese, são apresentados sistemas policlusters contendo seis e dez unidades ligadas em ponte. As novas supermoléculas apresentam uma série de processos redox multieletrônicos e, neste caso, a comunicação eletrônica entre os centros metálicos é mais pronunciada, sendo dependente do estado de oxidação dos clusters. / The aim of the work reported is to develop polynuclear structures based on trinuclear ruthenium clusters. All the oligomers are seen as interesting options to the future development of supramolecular devices, due to their photophysical and electrochemical properties. A series of mixed dimers and one trimer were obtained by the combination of the [Ru3O(CH3COO)6(py)2(CH3OH)]+ cluster with [Ru(bpy)2(P)(L)]+ complexes (P = N-heterocyclic bridging ligand; L = P, Cl or CN). The NMR, cyclic voltammetry and spectroelectrochemical characterization of the dimers where L = Cl were used as a base to interpret the results collected for the other complexes; the data reflect a weak interaction between the units, depending on the electronic characteristics of the bridging ligand P. In the dimers where L = CN, occurs the quenching of the [Ru(bpy)2] emission by the cluster through a photoinduced electron transfer mechanism. For the cluster in its reduced form, it is suggested that an energy transfer process also occurs. On the second part of the Thesis, polycluster systems containing six and ten bridged cluster units are reported. The novel supermolecules present a series of multielectronic redox processes and, in this case, electronic communication among the metallic centers is more pronounced, depending on the clusters oxidation state.

This thesis presents the synthesis of porphyrin arrays for light-harvesting applications using Wittig chemistry, which allows the construction of covalently bound systems that are conjugated, stable and easy to characterize. This was achieved using a dendrimer strategy utilizing tetraarylporphyrins as building blocks, monofunctionalized with either aldehyde or phosphonium salt groups at the β-pyrrolic position, and benzenes, polyfunctionalized with either aldehyde or phosphonium salt groups; stepwise control of the addition of each porphyrin moiety was thus obtained. In this way, different porphyrins in different metallated states were arranged in a determinate geometrical relationship, which is of great importance in the investigations on electron/energy transfers. Arrays containing up to five metalloporphyrin units (two kinds of porphyrins coordinating two different metals) were synthesized and characterized. The unexpected chromatography behaviour and 1H-NMR spectra of a Zn porphyrin functionalized with a 1,3-bis(methyl(diethylphosphonate) benzene were the reason for an investigation, which uncovered, mainly with the use of NMR spectrometry, the first case of intramolecular coordination between the Zn centre and a phosphonate group of the same porphyrin. The dynamic nature of this coordination was characterized and chemical-physical parameters for Zn porphyrin/phosphonate binding were determined. In order to establish the photophysical properties of our conjugated arrays, we synthesized a series of dyads containing Zn and free-base tetraphenylporphyrins (TPPs) connected through variable length phenylenevinylene-type bridges; along with this series, the preparation of the Zn and free-base homometallic homologue dyads and two series of monomers carrying the conjugated linker were realized. Collaboration with IFOS-CNR in Bologna, Italy was established in order to investigate the intramolecular photophysics of those systems, which involve efficient intramolecular energy transfer from the Zn to the free-base porphyrin. Finally, dyads composed of Fe(III) and Zn porphyrin were prepared as part of a project in collaboration with the University of Pennsylvania for the investigation of new artificial photosynthetic systems. Two series of dimers were prepared in order to obtain incorporation in both the classes of hydrophobic and hydrophilic proteins. TPPs were used for the making of the hydrophobic dyads while hydrophilicity was achieved by employing tetraester porphyrin derivatives, which can be quantitatively hydrolyzed to afford the correspondent water soluble acids. A new monosubstituted porphyrin was also synthesized and incorporated in the arrays to minimize steric hindrance inside the protein binding sites.

O trabalho apresenta a síntese e a caracterização de novos compostos heterocíclicos benzazólicos dos tipos 2-(4’-aminofenil)-6-nitrobenzazóis fluorescentes por apresentar provável transferência de carga intramolecular no estado excitado (ICT) e iminas aromáticas basedas nos compostos 2-(4’-amino-2’- hidroxifenil)-6-nitrobenzazóis fluorescentes devido a mecanismo de transferência protônica intramolecular no estado excitado (ESIPT). Estes compostos foram caracterizados por espectroscopia de absorção na região do Infravermelho, ressonância magnética nuclear de hidrogênio (1H-RMN). Foram realizados estudos fotofísicos através das espectroscopia de absorção na região do ultravioleta-visível e de emissão de fluorescência, determinando assim, os prováveis estados eletrônicos excitados em solventes polares e apolares. / This work presents the synthesis and characterization of new fluorescent heterocyclic derivatives based on 2-(4'-aminophenyl)-6-nitrobenzazoles, as well as aromatic imines based on 2-(4'-amino-2'-hydroxyphenyl)-6-nitrobenzazoles. These molecules are photoactive due to an intramolecular proton transfer in the excited state (ESIPT) or a intramolecular charge transfer (ICT) mechanism. These compounds were characterized by infrared spectroscopy and nuclear magnetic resonance 1H-NMR. Photophysical studies were performed using the absorption spectroscopy in the ultraviolet-visible and fluorescence emission, thereby determining the excited electronic states in polar and nonpolar solvents.

O trabalho apresenta a síntese e a caracterização de novos compostos heterocíclicos benzazólicos dos tipos 2-(4’-aminofenil)-6-nitrobenzazóis fluorescentes por apresentar provável transferência de carga intramolecular no estado excitado (ICT) e iminas aromáticas basedas nos compostos 2-(4’-amino-2’- hidroxifenil)-6-nitrobenzazóis fluorescentes devido a mecanismo de transferência protônica intramolecular no estado excitado (ESIPT). Estes compostos foram caracterizados por espectroscopia de absorção na região do Infravermelho, ressonância magnética nuclear de hidrogênio (1H-RMN). Foram realizados estudos fotofísicos através das espectroscopia de absorção na região do ultravioleta-visível e de emissão de fluorescência, determinando assim, os prováveis estados eletrônicos excitados em solventes polares e apolares. / This work presents the synthesis and characterization of new fluorescent heterocyclic derivatives based on 2-(4'-aminophenyl)-6-nitrobenzazoles, as well as aromatic imines based on 2-(4'-amino-2'-hydroxyphenyl)-6-nitrobenzazoles. These molecules are photoactive due to an intramolecular proton transfer in the excited state (ESIPT) or a intramolecular charge transfer (ICT) mechanism. These compounds were characterized by infrared spectroscopy and nuclear magnetic resonance 1H-NMR. Photophysical studies were performed using the absorption spectroscopy in the ultraviolet-visible and fluorescence emission, thereby determining the excited electronic states in polar and nonpolar solvents.