The MAO-B catalyzed metabolic bioactivation of the parkinsonian inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to generate the neurotoxic 1-methyl-4-phenylpyridinium species (MPP+) is well documented. The N-cyclopropyl analog (CPTP) of MPTP is a mechanism based inactivator of MAO-B which presumably is processed by a single electron transfer (SET) pathway to generate a bioalkylating species. These results have prompted us to study how the cytochromes P450, the major liver drug metabolizing oxidases, interact with N-cyclopropyl analogs of MPTP. HPLC with diode array detection and LC-electrosprary ionization mass spectrometry (LC-ESI/MS) based methods have been developed for metabolite detection and characterization. From the UV spectral data and pseudomolecular ion species observed by LC-ESI/MS, we have identified N-oxide, C-hydroxylated, and pyridinium metabolites. For the trans-1-(2-phenylcyclopropyl) analog, cinnamaldehyde and p-hydroxycinnamaldehyde also were characterized. Incubation of CPTP and its derivatives with cDNA expressed human hepatic cytochrome P450 has shown that CYP2D6 catalyzes the formation of cinnamaldehyde, the N-descyclopropyl, pyridinium and hydroxylated products. CYP3A4 is responsible for the formation of the N-descyclopropyl and pyridinium species and cinnamaldehyde but it does not mediate any hydroxylation reactions. Since both the a-carbon oxidation and N-descyclopropylation transformations are mediated by a single enzyme (either CYP2D6 or CYP3A4), we propose a common intermediate for both pathways, namely the cyclopropylaminyl radical cation generated by the SET pathway. This intermediate partitions between the a-carbon oxidation pathway leading to the dihydropyridinium and pyridinium species and the ring opening pathway leading to the N-descyclopropyl metabolite and aldehyde species. The phenyl substituent on the cyclopropyl ring stabilizes the ring opened distonic radical cation and favors the ring opening pathway and results in the formation of less of the pyridinium species. The proton and methyl substituents on the cyclopropyl ring favor the a-carbon oxidation pathway and increased amounts of the pyridinium species are formed. / Master of Science

The surface and interface of the metal nanoclusters and semiconducting nanomaterials play a key role in determining the electronic structure and overall photophysical properties. A single strand DNA stabilizes the metal nanoclusters, but it also influences the structural change, solvation free energy, and photophysical properties. On the other hand, surface and interface states in Pb and Cd chalcogenide nanomaterials affect the phonon mediated hot carrier relaxation. We applied DFT and DFT based non-adiabatic dynamics methods to study the surface and interface?s effects on the photoexcited processes. In the first part, we have studied the Ag nanoclusters' photophysical properties that are affected by the structural isomers, redox potential, nucleobase passivation, and cluster size. Ag nanoclusters are shown alternative reduction potential, which makes nanoclusters of singlet spin multiplicity thermodynamically favorable. Besides, the optically bright transition in the range of 2.5-3.5 eV is shown metal to ligand charge transfer. It is modulated by the s+p+d orbital mixing in the hole and electron states. We also simulate the charge transfer from the photoexcited PbS QD to organic dye (PDI) attached to the QD surface. Depending on the linker group and the dipole moment of neighboring passivating ligands, the PDI-QD conformations are varies. In response to structural change, the total dipole moment is modulated, changing its electronic structure and hence the photoexcited electron transfer rate from the PbS QD to PDI. We also investigate the inorganic-inorganic interactions in the PbCl2 bridged PbSe NPL and PbSe|CdSe Janus heterostructure. The energy dissipation rate of hot electrons is slower in NPL than the hot hole, while hot e-h relaxed to the band-edge by ?1.0ps in the QD. The slower relaxation rate is rationalized by a large average intraband energy difference and smaller coupling term. Besides, the hot carriers in the NPL are spatially separated by ?1.00 ps, which is a favorable condition for the carrier multiplication process. In Janus QD, (100) interfacial layer creates a structural mismatch in the CdSe part. Besides, the energy offset between the valance localized on PbSe and CdSe part is minimum in the PbSe Janus QD of an interface of (111) facet.

La demande énergétique de l’humanité augmente rapidement et ne montre aucun signe de ralentissement. Parallèlement à cette problématique, l'utilisation abusive de combustibles fossiles est l'une des principales causes d'augmentation de la concentration de CO₂ dans l'atmosphère. Ces problèmes doivent être résolus en termes de limitation des émissions de CO₂ et de recherche de sources d'énergie renouvelables pour remplacer les combustibles fossiles. De nos jours, l’énergie solaire est l’une des sources d’énergie renouvelables les plus efficaces. La conversion de l'énergie de la lumière solaire en électricité dans le photovoltaïque ou en énergie chimique par le biais de processus photocatalytiques implique invariablement un transfert d'énergie photo-induit et un transfert d'électrons. Dans ce contexte, l'objectif de la thèse est d'étudier les processus photo-induits dans les photosystèmes moléculaires utilisant la photolyse par flash laser. Le premier thème de cette thèse porte sur l’étude du transfert monoélectronique dans des systèmes de dyades donneur-accepteur en vue d’optimiser l’efficacité de la séparation des charges et de son application dans la cellule solaire organique photovoltaïque. Le deuxième thème de cette thèse porte sur l’étude de deux systèmes modèles de photosynthèse artificielle étudiés pour la possibilité d’une accumulation de charge par étapes. Ensuite, différents systèmes photocatalytiques, développés pour la photoréduction du CO₂, ont été étudiés. La compréhension des processus photo-induits devraient permettre l’amélioration de l'efficacité de la réduction du CO₂ dans les systèmes photocatalytiques pratiques. / The energy demand of humanity is increasing rapidly, and shows no signs of slowing. Alongside this issue, abuse using fossil fuels is one of the main reasons which leads to an increase in atmospheric CO₂ concentration. These problems have to be solved in terms of both limiting CO₂ emission and finding renewable energy sources to replace fossil fuels. Nowadays, solar energy appears as one of the most effective renewable energy sources. Conversion of solar light energy to electricity in photovoltaics or to chemical energy through photocatalytic processes invariably involves photoinduced energy transfer and electron transfer. In this context, the aim of the thesis focuses on studying photoinduced processes in molecular photosystems using laser flash photolysis. The first theme of this thesis focus on studying single electron transfer in Donor-Acceptor Dyad systems towards optimization efficiency of charge separation and application in the photovoltaic organic solar cell. In the second theme of this thesis, two model systems of artificial photosynthesis were investigated to assess the possibility of stepwise charge accumulation on model molecules. A fairly good global yield of approximately 9% for the two charge accumulation on MV²⁺ molecule was achieved. Then, different photocatalytic systems, which have developed for CO₂ reduction, were studied. Understanding of the photoinduced processes is an important step toward improving the efficiency of reduction of CO₂ in practical photocatalytic systems.

abstract: This study aims to address the deficiencies of the Marcus model of electron transfer (ET) and then provide modifications to the model. A confirmation of the inverted energy gap law, which is the cleanest verification so far, is presented for donor-acceptor complexes. In addition to the macroscopic properties of the solvent, the physical properties of the solvent are incorporated in the model via the microscopic solvation model. For the molecules studied in this dissertation, the rate constant first increases with cooling, in contrast to the prediction of the Arrhenius law, and then decreases at lower temperatures. Additionally, the polarizability of solute, which was not considered in the original Marcus theory, is included by the Q-model of ET. Through accounting for the polarizability of the reactants, the Q-model offers an important design principle for achieving high performance solar energy conversion materials. By means of the analytical Q-model of ET, it is shown that including molecular polarizability of C60 affects the reorganization energy and the activation barrier of ET reaction. The theory and Electrochemistry of Ferredoxin and Cytochrome c are also investigated. By providing a new formulation for reaction reorganization energy, a long-standing disconnect between the results of atomistic simulations and cyclic voltametery experiments is resolved. The significant role of polarizability of enzymes in reducing the activation energy of ET is discussed. The binding/unbinding of waters to the active site of Ferredoxin leads to non-Gaussian statistics of energy gap and result in a smaller activation energy of ET. Furthermore, the dielectric constant of water at the interface of neutral and charged C60 is studied. The dielectric constant is found to be in the range of 10 to 22 which is remarkably smaller compared to bulk water( 80). Moreover, the interfacial structural crossover and hydration thermodynamic of charged C60 in water is studied. Increasing the charge of the C60 molecule result in a dramatic structural transition in the hydration shell, which lead to increase in the population of dangling O-H bonds at the interface. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

abstract: Redox enzymes represent a big group of proteins and they serve as catalysts for biological processes that involve electron transfer. These proteins contain a redox center that determines their functional properties, and hence, altering this center or incorporating non-biological redox cofactor to proteins has been used as a means to generate redox proteins with desirable activities for biological and chemical applications. Porphyrins and Fe-S clusters are among the most common cofactors that biology employs for electron transfer processes and there have been many studies on potential activities that they offer in redox reactions. In this dissertation, redox activity of Fe-S clusters and catalytic activity of porphyrins have been explored with regard to protein scaffolds. In the first part, modular property of repeat proteins along with previously established protein design principles have been used to incorporate multiple Fe-S clusters within the repeat protein scaffold. This study is the first example of exploiting a single scaffold to assemble a determined number of clusters. In exploring the catalytic activity of transmetallated porphyrins, a cobalt-porphyrin binding protein known as cytochrome c was employed in a water oxidation photoelectrochemical cell. This system can be further coupled to a hydrogen production electrode to achieve a full water splitting tandem cell. Finally, a cobalt-porphyrin binding protein known as cytochrome b562 was employed to design a whole cell catalysis system, and the activity of the surface-displayed protein for hydrogen production was explored photochemically. This system can further be expanded for directed evolution studies and high-throughput screening. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

Artificial photosynthesis is the process, which mimics the natural photosynthesis process in order to convert solar energy to chemical energy. This process can be separated into four parts, which are antenna system, reaction center, water oxidation center, and proton reduction center. If we only focus on the ‘antenna system and reaction center' modules, expanding the absorption band in antenna system and generating long-lived charge separated state in reaction center are two fantastic strategies to design the molecules in order to improve the efficiency of the artificial photosynthesis process. In the first work of this dissertation, mono-18-crown-6 and mono-ammonium binding strategy was used to connect BODIPY- C60 supramolecular based donor–acceptor conjugates. The meso- position of BODIPY was modified by benzo-18-crown-6, and the 3, 5 methyl positions were replaced by two styryl groups, which covered additional donor (triphenylamine or 10-methylphenothiazine). The acceptor is a fulleropyrrolidine derivative, which included an ethyl ammonium cation. The absorbance wavelengths of the donor covered 300-850 nm, which is the visible/near IR region (wide band capturing). The ultrafast charge separation and relatively slow charge recombination was found from femtosecond transient absorption study. Next, a ‘two point' bis-18-crown-6 and bis-ammonium binding strategy was utilized to link BODIPY- C60 supramolecular based donor–acceptor conjugates. In this case, the meso- position of the BODIPY was modified by a secondary donor (triphenylamine, phenothiazine, or ferrocene). And the 3, 5 methyl positions were replaced by two styryl groups, which included benzo-18-crown-6. The acceptor (fulleropyrrolidine) was functionalized by bis-alky ammonium cations. The absorbance/ fluorescence emission titration and computational studies supported that the ‘two-point' strategy has stronger binding than ‘one-point' strategy. The relatively slow charge separation was found in these donor-acceptor conjugates. To extend the second work, a pristine BODIPY was linked to the meso- position of the BODIPY-bis-benzo-18-crown-6. When the acceptor (C60-bis- ammonium) was added to the system, a sequential energy transfer (EnT) followed by electron transfer (ET) process was performed. The energy transfer was found from absorbance/ fluorescence emission studies, and the photoinduced electron transfer was observed from femtosecond and nanosecond transient absorption study. This is a great mode to mimic the ‘antenna-reaction center' events of natural photosynthesis. In the last work of this dissertation, triplet sensitizers (I2BODIPY and I2azaBODIPY) covalently linked with a C60 to form the donor-acceptor system. In this work, triplet charge separated state (long-lived charge separated state) was expected. According to the femtosecond transient absorption studies, we observed the singlet charge separation was faster than the intersystem crossing process, that was the reason that only singlet charge separated state was found for I2BODIPY-C60, and no electron transfer was found for I2 azaBODIPY-C60.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18807号 / 理博第4065号 / 新制||理||1585(附属図書館) / 31758 / 京都大学大学院理学研究科化学専攻 / (主査)教授 杉山 弘, 教授 三木 邦夫, 教授 秋山 芳展 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19898号 / 工博第4214号 / 新制||工||1651(附属図書館) / 32975 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 木村 俊作, 教授 瀧川 敏算, 教授 今堀 博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20425号 / 農博第2210号 / 新制||農||1047(附属図書館) / 学位論文||H29||N5046(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 加納 健司, 教授 宮川 恒, 教授 三芳 秀人 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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