Die Verknüpfung einer exergonischen mit einer endergonischen Reaktion zur Ermöglichung der letzteren ist eine in biologischen Systemen weit verbreitete Strategie. Energetisch benachteiligte Elektronenübertragungsreaktionen im Rahmen der reduktiven Aktivierung von Nitrogenasen, Radikal-abhängigen β,α-Dehydratasen, der zu diesen verwandten Benzoyl-CoA-Reduktasen und diversen Cobalamin-abhängigen Methyltransferasen sind gekoppelt an die Hydrolyse von ATP. Der Methylgruppentransfer des reduktiven Acetyl-CoA-Weges von Carboxydothermus hydrogenoformans erfordert den Co(I)-Zustand des Corrinoid/Eisen-Schwefel Proteins (CoFeSP). Um diese superreduzierte Form nach einer oxidativen Inaktivierung zu regenerieren ist ein „Reparaturmechanismus“ erforderlich. Ein offenes Leseraster (orf7), welches möglicherweise für eine reduktive Aktivase von Corrinoid Enzymen (RACE) kodiert, wurde in dem Gencluster der am reduktiven Acetyl-CoA-Weg beteiligten Proteine entdeckt. Im Rahmen dieser Arbeit wurde dieses potenzielle RACE Protein biochemisch und strukturell charakterisiert und die ATP-abhängige reduktive Aktivierung von CoFeSP untersucht. Auf Grundlage der in dieser Arbeit gewonnenen Ergebnisse wurde ein Mechanismus für die ATP-abhängige Aktivierung entworfen. Dieser gibt Einblicke wie die durch ATP-Hydrolyse bereitgestellte Energie einen energetisch ungünstigen Elektronentransfer ermöglichen kann. Hierzu kombiniert RACo das Ausgleichen von Bindungsenergien mit Modulationen am Elektronenakzeptor. Eine vergleichbare Strategie wurde bisher in keinem anderen ATP-abhängigen Elektronenübertragungssystem wie dem von Nitrogenasen, Radikal-abhängigen β,α-Dehydratasen oder Benzoyl-CoA-Reduktasen beobachtet und könnte ein für RACE Proteine allgemein gültige Eigenschaft darstellen. / The principle of coupling an exergonic to an endergonic reaction to enable the latter is a widespread strategy in biological systems. Unfavoured electron transfer reactions in the reductive activation of nitrogenases, radical-dependent β,α-dehydratases and the related benzoyl- CoA reductases, as well as different cobalamin-dependent methyltransferases are coupled to the hydrolysis of ATP. The reductive acetyl-CoA pathway of Carboxydothermus hydrogenoformans relies on the superreduced Co(I)-state of the corrinoid/iron-sulfur protein (CoFeSP) that requires a “repair mechanism” in case of incidental oxidation. An open reading frame (orf7) coding for a putative reductive activase of corrinoid enzymes (RACE) was discovered in the gene cluster of proteins involved in the reductive acetyl-CoA pathway. In this work, this putative RACE protein was biochemically and structurally characterised and the ATP-dependent reductive activation of CoFeSP was investigated. Based on the results of this study, a mechanism for the ATP-dependent reactivation of CoFeSP was deduced providing insights into how the energy provided by ATP could trigger this unfavourable electron transfer. The reductive activator of CoFeSP combines balance of binding energies and modulations of the electron acceptor to promote the uphill electron transfer to CoFeSP. A comparable strategy has not been observed in other ATP-dependent electron transfer systems like nitrogenases, radical-dependent β,α-dehydratases and benzoyl- CoA reductases and could be a universal feature of RACE proteins.

Der Gegenstand der vorliegenden Arbeit ist die Untersuchung von photoinduzierten Energietransferprozessen (EET) und Elektronentransferprozessen (ET) in Modellsystemen, die als potentiell geeignet für eine Nutzung in der artifiziellen Photosynthese angesehen werden. Den beiden wesentlichen Zugängen zur Architektur artifizieller Photosynthese-Systeme entsprechend wurden vergleichend kovalente und sich selbst organisierende Systeme untersucht. In beiden Zugängen wurden ähnliche chemische Komponenten als optisch aktive Moleküle eingesetzt, insbesondere Phthalocyanine mit einem Silizium-Zentralatom (SiPc). Durch eine Kombination von stationären und zeitaufgelösten optisch-spektroskopischen Methoden konnten die lichtinduzierten ET- und EET-Prozesse identifiziert und quantifiziert werden. Im ersten Teil der Arbeit wurden mehrere kovalent gebundene Triaden und eine Pentade untersucht. In allen Systemen finden sehr effiziente ET und EET Prozesse statt. Es wurde gezeigt, dass das Lösungsmittel großen Einfluss auf die photophysikalischen Eigenschaften der Systeme ausübt. Die Lebensdauer des ladungsseparierten Zustandes variiert von 1,7 ns in Toluol bis 30 ps in DMF. Im zweiten Teil der Arbeit wurde erstmals gezeigt, dass sich in wässriger Lösung ein supramolekularer Komplex, bestehend aus einem Beta-Cyklodextrin (CD), einem konjugierten Subphthylocyanin (SubPc), einem Porphyrin (Por) und einem SiPc bilden kann. Letzteres wurde über unterschiedliche Ketten an zwei CDs kovalent gebunden. Die Selbstorganisation wird über hydrophobe Wechselwirkungen vermittelt und die Bildung der Komplexe ist sehr effizient. Nach selektiver Anregung von SubPc finden sequenzielle ET- und EET-Prozesse von SubPc zu SiPc statt. Das Por spielt die Rolle einer energetischen und elektronischen Brücke und ermöglicht die ET und EET-Prozesse von SubPc zu SiPc. Die Ladungsrekombination in den Grundzustand geschieht innerhalb von 1,7 ns. / The main objective of the present thesis was to conduct investigations of photo-induced electron transfer (ET) and excitation energy transfer (EET) processes in model compounds that are considered potentially appropriate for use in artificial photosynthesis. Two approaches have been used to construct the artificial photosynthetic systems, namely covalent and supramolecular approach. In both systems similar optically active molecules have been employed, particularly silicon-based phthalocyanines (SiPc). A comparative study between the covalently-linked and self-assembled systems had been conducted. For these purposes, thorough spectroscopic measurements in the UV/Vis range had been performed on these conjugates. A combination of steady-state and time-resolved experiments allowed an identification and quantification of the photo-induced ET and EET processes. In the first part of the work several covalently bound triads and a pentad bearing a central SiPc unit were studied. In all systems highly efficient ET and EET processes take place. It was found that the solvent exerts great influence on the photophysical properties of the systems. The lifetime of the charge-separated state varied from 1.7 ns (toluene) down to 30 ps (DMF). In the second part of the thesis, for the first time the formation of ternary supramolecular complexes consisting of a beta-cyclodextrin (CD), a conjugated subphthalocyanine (SubPc), a porphyrin (Por) and a series of SiPcs substituted axially with two CDs via different spacers was shown. These components are held in water by host-guest interactions and the formation of these host-guest complexes was found to be very efficient. Upon excitation of the SubPc-part of the complex sequential ET and EET processes from SubPc to SiPc take place. The Por dye acts as a transfer bridge enabling these processes. The probability of ET is controlled by the linker between CD and SiPc. Charge recombination to the ground state occurs within 1.7 ns.

Diese Arbeit wird einer Weiterentwicklung der Dichtematrixtheorie und ihrer Anwendung zum Studium ultraschneller laserpulsinduzierter Dynamik in Molekularsystemen in Wechselwirkung mit einem thermischen Bad gewidmet. Zwei grosse Themenkomplexe werden behandelt. Zuerst werden die sogenannten Gedächtniseffekte diskutiert. Diese folgen aus einer reduzierten Beschreibung des Molekularsystems, in der die Umgebungsfreiheitsgrade eliminiert werden. Im zweiten Teil wird die Laserpulssteuerung der dissipativen Molekulardynamik untersucht. Die theoretische Beschreibung von offenen Quantensystemen führt zu einer zeitlich nicht-lokalen Bewegungsgleichung: Die Zeitentwicklung des Molekularsystems hängt von seiner Vergangenheit ab. In dieser Arbeit wird eine numerische Methode zur Lösung der zeitlich nicht-lokalen Bewegungsgleichung entwickelt und mit einem minimalen Modell eines polyatomaren Moleküls unter dissipativem Einfluss der Umgebung getestet. Eine analytische Lösung der Bewegungsgleichung für den speziellen Fall einer sehr langen Gedächtniszeit wurde hergeleitet. Zur Identifizierung solcher Gedächtniseffekte vergleichen wir diese analytische Lösung mit numerischen Rechnungen inklusive Gedächtnis und mit approximativen Rechnungen, die die zeitliche Nicht-Lokalität vernachlässigen. Für eine Anregung mit einem Laserpuls, der kürzer als die Gedächtniszeit des Systems ist, zeigt das Molekularsystem eine erkennbar unterschiedliche Dynamik als ohne Gedächtniss. Die Gedächtniseffekte werden mit abfallender Laserpulslänge deutlich ausgeprägter. Der zweite Teil der Arbeit konzentriert sich auf die Anwendung der Theorie der Optimalen Kontrolle, um die molekulare Dynamik zu steuern. Aus der Theorie der Optimalen Kontrolle erhält man Laserpulse, die bestimmte Aufgaben erfüllen, z.B. die Besetzung gewünschter vibronischer Niveaus des Molekularsystems oder die Platzierung eines Wellenpakets auf einer vorgegebenen Position auf der molekularen Potentialfläche. Als erstes Beispiel haben wir die Kontrolle des dissipativen fotoinduzierten Elektronentransfers in einem Donator-Brückenmolekül-Akzeptor System betrachtet, wobei wir das Gedächtniss vernachlässigt haben. Die Steuerbarkeit des Elektronentransfers wird diskutiert und der Mechanismus, mit dem sie möglich wird, wird identifiziert. Wir haben festgestellt, dass die Steuerung der Elektronentransferreaktionen selbst unter dem Einfluss von Dissipation möglich ist, obwohl die Kontrollausbeute mit steigender Dissipation drastisch abfällt. In Anwesenheit von Dissipation verändert sich auch der Mechanismus der Steuerung. Die experimentelle Ausführbarkeit der Herstellung des aus der Theorie der Optimalen Kontrolle resultierenden Kontrollpulses wird diskutiert und Methoden werden präsentiert, die die Abschätzung der Effizienz ermöglichen, mit der ein Flussigkristall--Laserpulsformer, wie er heute in Experimenten verwendet wird, den gewünschten Puls erzeugen kann. Um zwischen verschiedenen Kontrollaufgaben zu unterscheiden, wird ein quantitatives Mass eingeführt, das die Komplexität der Kontrollaufgabe charakterisiert. Die Theorie der Optimalen Kontrolle wird auch für Molekularsysteme formuliert, die statische Unordnung zeigen, und wird auf ein Ensemble von Molekülen mit zufälligen Orientierungen angewendet. Zum Schluss wird die Bedeutung der Gedächtnisseffekte für die Steuerung der dissipativen Dynamik diskutiert und die Theorie der Optimalen Kontrolle neu formuliert um eine zeitliche Nicht-Lokalität in der Bewegungsgleichung des Molekularsystems zu berücksichtigen. / This work is dedicated to a further development of the density matrix theory and its application to the study of ultrafast laser pulse induced dynamics in molecular systems interacting with a thermal environment. Two topics are considered, first the so-called memory effects are analyzed which result from a reduced description of the molecular system excluding the environmental degrees of freedom. And secondly, the laser pulse control of dissipative molecular dynamics is examined. The theoretical description of open quantum systems results in a time non-local equation of motion so that the evolution of the molecular system depends on its past. In this work a numerical method to solve the time non-local equations of motion has been developed and tested for a minimal model of a polyatomic molecule subject to the dissipative influence of an environment. An analytical solution of the equation of motion for the special case of very long standing memory is also achieved. To identify signatures of such memory effects in general case we compare this analytical solution with numerical calculations involving memory and with approximative computations ignoring time non-locality. For the excitation by a laser pulse shorter than the duration of the memory the molecular systems exhibit noticeably different dynamics than for the absence of the memory. The effects become significantly more pronounced with decreasing laser pulse durations. The second part of the work concentrates on the application of the optimal control theory to guide molecular dynamics. Optimal control theory provides laser pulses which are designed in such a manner to fulfill certain control tasks, e.g. the population of a desired vibrational level of the molecular system or the placement of a wavepacket on a prescribed position on the molecular potential energy surface. As a first example the control of the dissipative photo-induced electron transfer in a donor--bridge--acceptor systems has been particularly considered ignoring the memory. The controllability of the electron transfer has been discussed and the mechanism by which it becomes possible has been identified. We have found the control of electron transfer reactions feasible even under the influence of dissipation although the yield of the control decreases drastically with increasing dissipation. In the presence of dissipation mechanism of the control has been found to change. The feasibility of the reproduction of the control pulses resulting for the optimal control theory in the experiment has been discussed and methods have been presented how to check the efficiency of the reproduction of optimal control pulses by liquid crystal pulse shapers, prevailingly used in modern control experiments. To distinguish different control tasks a quantitative measure has been introduced characterizing complexity of the control task. The optimal control theory has also been formulated for molecular systems showing static disorder and applied on an ensemble of molecules exhibiting random orientations. Finally, the importance of memory effects for the control of dissipative dynamics has been discussed and the optimal control theory has been formulated to account for a time non-locality in the equation of motion for molecular systems.

No description available.

No description available.

Cancer is a leading cause of death that affects millions of people across the globe each year. Photodynamic therapy (PDT) is a relatively new treatment approach for cancer in which anticancer drugs are activated by light at an appropriate wavelength to generate highly cytotoxic reactive oxygen species (ROS) and achieve tumor destruction. Compared with conventional chemo- and radiotherapy, PDT can be performed with minimal invasiveness, local targeting and reduced side effects. However, most of the currently available PDT drugs mainly absorb in the visible part of the spectrum, where light penetration depth into human tissues is very limited. Therefore, increasing the treatment depth of PDT has been considered to be an important approach to improve the effectiveness of PDT for treating larger and thicker tumor masses. In this thesis, we present our investigation into the potential of two-photon activated PDT (2-γ PDT), combination therapy of PDT and chemotherapy, and bioluminescence-activated PDT as a means to increase the treatment depth of this modality. In 2-γ PDT, the photosensitizing agents are activated through simultaneous absorption of two photons. This approach allows the use of near-infrared (NIR) light that can penetrate deeper into tissues and thus, has the potential of treating deep-seated tumors and reducing side effects, while the non-linear nature of two-photon excitation (TPE) may improve tumor targeting. We have evaluated the PDT efficacy of a second-generation photosensitizer derived from chlorophyll a, pyropheophorbide a methyl ester (MPPa), through both one- and two-photon activation. We observed that MPPa had high one-photon (1-γ PDT efficacy against both cisplatin-sensitive human cervical (HeLa) and cisplatin-resistant human lung (A549) and ovarian (NIH:OVCAR-3) cancer cells when activated by femtosecond (fs) laser pulses at 674 nm. At a low light dose of 0.06 J cm-2, the MPPa concentration required to produce a 50% cell killing effect (IC50) was determined to be 5.3 ± 0.3, 3.4 ± 0.3 and 3.6 ± 0.4 μM in HeLa, A549 and NIH:OVCAR-3 cells, respectively. More significantly, we also found that MPPa could be effectively activated at the optimal tissue-penetrating wavelength of 800 nm through TPE. At a light dose of 886 J cm-2, where no measurable photodamage was observed in the absence of MPPa, the IC50 values were measured to be 4.1 ± 0.3, 9.6 ± 1.0 and 1.6 ± 0.3 μM in HeLa, A549 and NIH:OVCAR-3 cells, respectively. We obtained corresponding LD50 (the light dose required to produce a 50% killing effect) values of 576 ± 13, 478 ± 18 and 360 ± 16 J cm-2 for 10 μM MPPa, which were approximately 3-5 times lower than the published 2-γ LD50 of Visudyne® and 20-30 times lower than that of Photofrin®. These results indicate that MPPa may serve as a photosensitizer for both 1- and 2-γ activated PDT treatment of difficult-to-treat tumors by conventional therapies. Indocyanine green (ICG), a dye having an absorption maximum near 800 nm, has been considered to be a potential NIR PDT agent. However, the PDT efficacy of ICG has been found to be very limited probably due to the low yield of cytotoxic ROS. In the present work, we have evaluated the combination effects of ICG-mediated PDT with conventional chemotherapy mediated by two types of chemotherapeutic drugs, namely the type II topoisomerase (TOPII) poisons etoposide (VP-16)/teniposide (VM-26) and the platinum-based drugs cisplatin (CDDP)/oxaliplatin (OXP). Synergistic enhancement of cytotoxicity and increased yields of DNA double strand breaks (DSBs) were observed in HeLa, A549 and NIH:OVCAR-3 cancer cells treated with the combination of ICG-PDT and VP-16. The presence of VP-16 during the laser irradiation process was found to be critical for producing a synergistic effect. An electron-transfer-based mechanism, in which ICG could increase the yield of highly cytotoxic VP-16 metabolites, was proposed for the observed synergistic effects, although direct spectroscopic detection of the reaction products was found to be very challenging. Moreover, we observed a much lower degree of synergy in the human normal fibroblast GM05757 cells than that in the three cancer cell lines investigated. Synergistic effects were also observed in A549 cells treated with the combination of ICG-PDT and VM-26 (i.e. an analog of VP-16). Furthermore, the combination of low-dose CDDP/OXP and ICG-PDT was demonstrated to produce an additive or synergistic effect in selected cancer cell lines. These preliminary results suggest that the combination of ICG-PDT with VP-16/VM-26 or CDDP/OXP chemotherapy may offer the advantages of enhancing the therapeutic effectiveness of ICG-PDT and lowering the side effects associated with the chemotherapeutic drugs. Bioluminescence, the generation of light in living organisms through chemical reactions, has been explored as an internal light source for PDT in recent years. This approach, in principle, does not suffer from the limited tissue penetration depth of light. In the present project, we have evaluated the effectiveness of luminol bioluminescence in activating the porphyrin photosensitizers meso-tetra(4-sulfonatophenyl)porphine dihydrochloride (TPPS4) and Fe(III) meso-tetra(4-sulfonatophenyl)porphine chloride (FeTPPS). The combination treatment induced significant killing of HeLa cells, while additive effects were observed in two normal human fibroblast cell lines (GM05757 and MRC-5). Our observations indicate that bioluminescence of luminol may generate sufficient light for intracellular activation of PDT sensitizers. Furthermore, the combination treatment may have intrinsic selectivity towards cancerous tissues. In summary, we have demonstrated effective killing of cancer cells by MPPa-mediated 1- and 2-γ PDT, combination of ICG-PDT and VP-16/VM-26 or CDDP/OXP chemotherapy, and bioluminescence of luminol activated PDT mediated by TPPS4/FeTPPS. These positive preliminary results indicate that all these three approaches have the potential of increasing the treatment depth of PDT and facilitating the development of more effective PDT treatment strategies.

Time resolved spectroscopy is one of the crucial methods used to study processes on molecular level in biological systems. It is useful especially for monitoring fast processes that take a place in photosynthetic apparatus of photosynthetic organisms, such as electron and energy transfer. The integral parts of photosynthetic apparatus are carotenoids, whose role in the photosynthetic apparatus is not as well explored as it is for chlorophylls. It was proved that carotenoids actively participate in energy transfer processes in photosynthetic antennas. They have a crucial role in protection against excess energy damage. They are also electron donors in both antennas and reaction centers. The fact that photo-physical properties of carotenoids are much different from properties of others organic pigments, complicates studies of their functions in photosynthesis as well as in other biological systems. This thesis employs advanced methods of femtosecond spectroscopy to obtain more information about carotenoid functions in some biological systems and in solution with special focus on carotenoids containing carbonyl group.

L’objectif de ce travail a été de mettre en place un système original capable de produire et stocker l’énergie à partir de la lumière dans un dispositif unique. Pour ce faire, nous avons choisi d’adapter l’électrode photo-sensible d’une DSSC sur un système d’accumulateur électrochimique. La première partie de ce travail a été de mettre en place la technique de spectroscopie EIS-λ, basée sur la spectroscopie d’impédance électrochimique couplée à un balayage en longueur d’onde de la lumière incidente. L’objectif de cette mesure est d’identifier et de quantifier les différents mécanismes de transfert électroniques, photo-dépendant ou non, ayant lieu à la surface de l’électrode photo-sensible, ainsi que les processus de désactivation des états excités des sensibilisateurs. Nous nous sommes ensuite penchés sur la recherche des conditions optimales d’utilisation de deux coadsorbants — l’acide bismethoxyphenyl phosphinique ou BMPP et l’acide chenodesoxycholique ou CDCA — avec le sensibilisateur de référence N719. Nous avons également quantifié leurs activités shield et anti-π-stacking grâce à la technique EIS-λ. Nous avons ainsi réalisé une DSSC présentant un rendement de photo-conversion de 8,3% en utilisant le co-adsorbant BMPP dans un ratio [co-ads]/[S] = 1, contre 7,2% dans les conditions de référence — avec le coadsorbant CDCA utilisé dans un ratio [co-ads]/[S] = 10. Par la suite, nous avons imaginé et synthétisé trois complexes de ruthénium hydrophiles originaux dont nous avons testé le pouvoir de photo-conversion dans des DSSC à électrolyte 100% aqueux, en présence des co-adsorbants sélectionnés. Ces systèmes ont permis de dépasser le pouvoir de photo-conversion du sensibilisateur N719, dans l’eau, avec un rendement maximal obtenu de 1,31%. Enfin, nous avons sélectionné la meilleure combinaison sensibilisateur / co-adsorbant afin de réaliser une électrode photo-sensible que nous avons implémentée dans un système original d’accumulateur électrochimique à base d’électrolytes aqueux. Le système ainsi mis en place constitue aujourd’hui le premier dispositif fonctionnel d’accumulateur 100% aqueux photo-rechargeable à partir d’une électrode mésoporeuse photo-sensibilisée / The aim of this work was to imagine and to develop a new system able to produce and store energy from sunlight in a single device. For this purpose, the photo-sensitive electrode of a DSSC has been adapted to an electrochemical accumulator. The first part of this work was to develop a new spectroscopic technique, called EIS-λ and based on electrochemical impedance spectroscopy combined to incident light wavelength sweep. This technique has proved its capacity to identify and quantify the different mechanisms of electron transfer over the surface of the semiconducting material and their dependency to incident wavelength, together with the various deactivation processes of the excited state of the sensitizer. Then, we investigated the best conditions to use two different co-adsorbents — namely bis-methoxyphenylphosphinic acid, or BMPP, and chenodesoxycholic acid, or CDCA — with the reference sensitizer N719. The shield and anti-π-stacking activities of the two coadsorbents has been characterized using EIS-λ technique. DSSC with a photo-conversion yield of 8,3% has been prepared in the lab using BMPP in a ratio [co-ads]/[S] = 1 while reference conditions – namely with CDCA in a ratio [co-ads]/[S] = 10 — only gave 7,2%. Besides, we have designed and synthesized three original hydrophilic ruthenium complexes, then tested their photo-conversion properties in DSSC with 100% aqueous electrolytes. Such systems, with the selected co-adsorbents, allowed 1,31% photo-conversion yield to be obtained, which is two times larger than the efficiency exhibited by N719 in the same electrolyte conditions. Finally the best combination sensitizer / co-adsorbent has been selected to achieve a photo-sensitive electrode which has been implemented in an original electrochemical accumulator with aqueous electrolytes. This system represents the first functional device of a 100% aqueous accumulator, which is photo-reloadable with a photosensitized mesoporous electrode

Les travaux réalisés au cours de cette thèse ont consisté en l’élaboration d’édifices multi-chromophoriques pour des applications en cellules solaires organiques. La conception de ces nouveaux matériaux a été guidée par trois paramètres : (i) l’augmentation de la planéité pour une meilleure organisation intermoléculaire ; (ii) la modulation de la fenêtre spectrale d’absorption pour capter un maximum de photons ; (iii) l’enrichissement électronique des matériaux pour faciliter la séparation des charges. Notre choix s’est porté sur les hydrocarbures aromatiques polycycliques, de part leurs propriétés structurantes bien connues. La synthèse du 2-bromodibenzo[g,p]chrysène a été réalisée par des réactions de type Scholl intramoléculaires, puis sa dérivatisation a permis de synthétiser des matériaux correspondants. La mono-fonctionnalisation d’un synthon benzo[1,2-b:3,4-b’:5,6-b’’]trithiophène a également été effectuée. Des BODIPYs dithiényles α-fusionnés ont ensuite été synthétisés selon une procédure originale de couplages oxydants intramoléculaires, permettant d’obtenir des composés plans, fonctionnalisés et fonctionnalisables, tout en contournant la chimie contraignante du pyrrole. L’obtention de dyades et triades à base de DPPs, de BODIPY et de triphénylamines ont permis d’obtenir des composés panchromatiques et d’étudier les phénomènes d’extinction de la fluorescence par spectroscopies statiques et ultrarapides. Un dernier projet a porté sur des édifices de type D-A-D à base de BODIPYs et amines aromatiques tertiaires. / The projects developed in this thesis consisted in the elaboration of multi-chromophoric scaffolds towards applications in bulk heterojunction organic solar cells. The design of the materials was guided by three main parameters: (i) the increase of the planarity to observe a better intermolecular organization; (ii) the broadening of the spectral absorption window in order to maximize the number of absorbed photons; (iii) the increase of the electronic density in order to facilitate the charge separation. First, the structural properties of mono-functionalized polycyclic aromatic hydrocarbons (PAH) were investigated with the synthesis of 2-bromodibenzo[g,p]chrysene by Scholl type reactions, followed by its functionalization and the development of related materials. Then we also focused on another PAH: benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene and its subsequent functionalization. α-Fused dithienyl BODIPYs were then built according to an original procedure based on intramolecular oxidative coupling reactions. Substituted and functionalizable planar compounds were obtained bypassing the instability of the pyrrole ring chemistry. Subsequently, the elaboration of dyads and triads based on DPPs, BODIPY and triphenylamines led to the examination of the fluorescence quenching process by static and ultrafast spectroscopies. A last project consisted in the study and applications of D-A-D edifices based on BODIPYs and ternary aromatic amines.

"Laser flash spectroscopy of photosystem II" Photosystem II (PS II) of plants and cyanobacteria oxidizes water in a light-powered reaction. Thereby, this protein is the ultimate source of the atmospheric oxygen. The capacity to oxidize water is owed to two properties of PS II: (i) The midpoint potential of the oxidizing chlorophyll moiety is increased by 0.6 V compared to photosystem I or photochemical reaction centers of anoxygenic bacteria, and (ii) the energy requirements of the four steps needed for the tetravalent oxidation of water are adapted to the energy of red light quanta. This thesis deals with two particular aspects, namely: 1. The coupling of the electron transfer from tyrosine Z (YZ) to the primary donor (P680+) to proton transfer, and an inquiry on the role of a positive charge on YZox (plus base cluster) in increasing the oxidizing potential at the catalytic site. 2. The localization of the electron hole, P680+, among the excitonically coupled four inner chlorophyll a molecules, and an estimation of the midpoint potential differences between them. Electron-proton-coupling by YZ This study was carried out with PS II core complexes from spinach or pea with a deactivated (removed) manganese cluster. The reduction of P680+ was investigated as a function of pH by detecting the laser flash induced absorption changes with nanosecond resolution. Two kinetic components were found with different pH-dependence and activation energies. The alteration of kinetic parameters by H/D isotope substitutions or by addition of divalent cations implied two different types of YZ-oxidation: At acidic pH the electron transfer was coupled with proton transfer, whereas in the alkaline region it was more rapid and no longer controlled by proton transfer. The conversion between both mechanisms occured at pH 7.4. This value corresponds either to the apparent pK of YZ itself (i.e. of the hydroxy group of the phenol ring) or to the pK of an acid-base-cluster, which includes YZ. Independent measurements of pH-transients by following the absorption changes of hydrophilic proton indicators corroborated this notion. The data were interpreted as indicating that the phenolic proton of YZ was released into the medium at acidic, but not at alkaline pH. The electron transfer and proton release characteristics of intact, oxygen-evolving PS II resembled those in deactivated samples kept at alkaline pH. We concluded that the electron transfer from YZ to P680+ in the native system was not coupled with proton transfer into the bulk. This has shed doubt on a popular hypothesis on the role of YZ as 'hydrogen abstractor' from bound water. On the other hand, the energetic constraints of water oxidation could be eased by the positive upcharging during oxidation of YZox plus its base cluster. On the localization of the electron hole of P680+ Photooxidation of PS II oxidizes the set of four innermost chlorophyll a molecules giving rise to the only spectroscopically defined species P680+. The deconvolution of difference spectra into bands of pigments is ambiguous. By using photoselective excitation of antennae, i.e. chl a molecules with site specific energies at the long wavelength border of the mean Qy-band, and by polarized detection, it was possible to tag P680+QA-/P680QA and 3P680/P680 difference spectra with a further parameter, the (wavelength-dependent) anisotropy r. Results obtained at liquid nitrogen temperature (77 K) can be clearly interpreted in terms of two chl a monomer bands. The two main components of the P680+QA-/P680QA difference spectrum were marked by two distinct values of the anisotropy and could be interpreted in a straightforward manner: the bleaching of a band at 675 nm belonging to the charged species (chl a+) and an electrochromic blue-shift of a nearby chl a from 684 to 682 nm. The main bleaching band of the 3P680/P680 spectrum (at 77 K) can be apparently attributed to a third (or several) chl a component(s). The analysis of the P680+QA-/P680QA spectrum at cryogenic temperature is compatible with monomeric chl a bands. On the other hand, one could assume a system of excitonically coupled core pigments, as it was recently introduced in the literature on the basis of energy transfer studies ('multimer model'). However, in view of the clear indications for an electrochromic band shift and the location of the bleaching band, which absorbs in a wavelength region of monomeric chl a, one assumption of the 'multimer model' should be questioned. Presumably, the excitonic couplings are rather weak, in particular between each of the two central chl a-molecules (PA/PB) and its respective accessory chl a (BA/BB), because of (i) the distances and (ii) different site energies of the monomeric chromophores. At room temperature, the absorption difference and anisotropy spectra of P680+QA-/P680QA were clearly altered. The anisotropy data indicated that the changes could no longer exclusively be ascribed to thermal broadening of individual bands. The localization of the positive charge on one pigment, analogous to the situation at 77 K, was now unlikely. Hence, the midpoint potential differences between the inner four chlorophyll a molecules were small and were estimated as approximately 15 meV.