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Structural determinations and electrochemical properties in the series of multinuclear ferrocenyl-ethynyl complexes with formula [(£b5-C5(CH3)5)(P2)MII-C¡ÝC-(fc)n-C¡ÝC-MII(P2)(£b5-C5(CH3)5)] (fc = ferrocenyl; M = Fe(II), Ru(II), Os(II); R = H, CH3; P2 = Ph2PCH2CH2PPh2 (dppe)) are reported. Complexes with more electron-rich ligand environment, were prepared with regard to the understanding of electronic coupling mechanism. These complexes undergo sequential reversible oxidation events from -0.2 V to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH2Cl2 solution and the low-pontential waves have been assigned to the end-capped metallic centers. The magnitude of the electronic coupling between two terminal metallic centers in the series of complexes was estimated by electrochemical technique. Based on the correlation between the £GE1/2 values and the second redox potentials of the end-capping metallic centers in the series of complexes, a qualitative explanation for the different magnitude of the electronic coupling is given.

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Enzymes have found applications in a broad range of industrial production processes. While high catalytic activity, selectivity and mild reaction conditions are attractive advantages of the biocatalysts, particularly costs arising from required cofactors pose a sever limitation. While cofactor-recycling systems are available, their use implies constraints for process set-up and conditions, which are a particular problem e.g. for solid-gas-phase reactions. Several oxidoreductases are able to directly exchange electrons with electrodes. Hence, the co-immobilization of both, an electron-utilizing and an electron-generating oxidoreductase on conductive nanoparticles should facilitate the direct electron flow from an enzymatic oxidation to a reduction reaction circumventing redox-cofactors requirements. In such a set-up, hydrogenases could generate and provide electrons directly form gaseous hydrogen. This thesis describes the co-immobilization of the oxygen tolerant hydrogenases from C. eutropha or C. metallidurans and cytochrome P450BM3 as test system. Conductive material in the form of carbon nanotubes (CNT) serves as a suitable support. A combination of the hydrogenase and the catalytic domain of P450BM3 immobilized on carbon nanotubes were tested for the oxidation of lauric acid in the presence of hydrogen instead of an electron-transport cofactor. The GC-MS analysis reveals the conversion of 4% of lauric acid (LA) into three products, which correspond to the hydroxylated lauric acid in three different positions with a total turnover (TON) of 34. The product distribution is similar to that obtained when using the wildtype P450BM3 with the nicotinamide adenine dinucleotide phosphate (NADPH) cofactor. Such electronic coupling couldn’t be achieved for the conversion of other substrates such as propane and cyclohexane, probably due to the high uncoupling rate within the heme-domain of cytochrome P450BM3 when unnatural substrates are introduced.

Computational methods are a convenient resource to solve drawbacks of drug research such as high cost, time-consumption, and high risk of failure. In order to get an optimum search of new drugs we need to design a rational approach to analyze the molecular forces that govern the interactions between the drugs and their target molecules. The objective of this project is to get an understanding of the interactions between drugs and proteins at the molecular level. The interaction energy, when protein and drugs react, has two components: non-covalent and covalent. The former accounts for the ionic interactions, the later accounts for electron transfer between the reactants. We study each energy component using the most popular analysis tools in computational chemistry such as docking scoring, molecular dynamics fluctuations, electron density change, molecular electrostatic potential (MEP), density of states projections, and the transmission function. We propose the probability of transfer of electrons (transmission function) between reactants in protein-drug complexes as an alternative tool for molecular recognition and as a direct correlator to the binding affinity. The quadratic correlation that exists between the electron transfer rate and the electronic coupling strength of the reactants allow a clear distinguishability between ligands. Thus, in order to analyze the binding affinity between the reactants, a calculation of the electronic coupling between them is more suitable than an overall energetic analysis such as free reaction energy.

Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.

In this dissertation, we employ a number of computational methods, including Ab Initio, Density Functional Theory, and Molecular Dynamics simulations to investigate key microscopic parameters that govern charge-transport and charge-generation in single-component and bimolecular charge-transfer organic semiconductors. First, electronic (transfer integrals, bandwidths, effective masses) and electron-phonon couplings of single-component organic semiconductors are discussed. In particular, we evaluate microscopic charge-transport parameters in a series of nonlinear acenes with extended pi-conjugated cores. Our studies suggest that high charge-carrier mobilities are expected in these materials, since large electronic couplings are obtained and the formation of self-localized polarons due to local and nonlocal electron-phonon couplings is unlikely. Next, we evaluate charge detrapping due to interaction with intra-molecular crystal vibrations in order to explain changes in experimentally measured electric conductivity generated by pulse excitations in the IR region of a photoresistor based on pentacene/C60 thin film. Here, we directly relate the nonlocal electron-phonon coupling constants with variations in photoconductivity. In terms of charge-generation from an excited manifold, we evaluate the modulation of the state couplings between singlet and triplet excited states due to crystal vibrations, in order to understand the effect of lattice vibrations on singlet fission in tetracene crystal. We find that the state coupling between localized singlet and correlated triplet states is much more strongly affected by the dynamical disorder due to lattice vibrations than the coupling between the charge-transfer singlet and triplet states. Next, the impact of Hartree-Fock exchange in the description of transport properties in crystalline organic semiconductors is discussed. Depending on the nature of the electronic coupling, transfer integrals and bandwidths can show a significant increase as a function of the amount of the Hartree-Fock exchange included in the functional. Similar trend is observed for lattice relaxation energy. It is also shown that the ratio between electronic coupling and lattice relaxation energy is practically independent of the amount of the Hartree-Fock exchange, making this quantity a good candidate for incorporation into tight-binding transport models. We also demonstrate that it is possible to find an amount of the Hartree-Fock exchange that recovers (quasi-particle) band structure obtained from a highly accurate G0W0 approach. Finally, a microscopic understanding of a phase transition in charge-carrier mobility from temperature independent to thermally activated in stilbene-tetrafluoro-tetracyanoquinodimethane crystal is provided.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Este trabalho está focado no desenvolvimento de complexos de rutênio binucleares baseados no ligante ponte 2,6-bis(2-piridil)benzodiimidazol (dpimH2) com potencial aplicação como catalisadores para oxidação da água. O acoplamento eletrônico entre os centros metálicos bem como as propriedades eletrônicas e catalíticas podem ser controlados via reações ácido-base no ligante bis-bidentado. Dessa forma, neste trabalho descrevemos o preparo e a caracterização do respectivo composto mononuclear, bem como do complexo binuclear simétrico [{RuCl(phtpy)}2(dpimH2)](Otf) 2 (onde phtpy=4-fenil-2,2\':6\',\'\'-terpiridina), e do análogo assimétrico [{Ru(bpy)2}(dpimH2){Ru(phtpy)Cl}](ClO4)3 (onde bpy=2,2\'-bypiridina), que possui um centro catalítico e um grupo cromóforo na mesma molécula como esperado em um fotocatalisador, em que os dois centros catalíticos estão covalentemente conectados através do ligante ponte funcional. As caracterizações estrutural e eletrônica de ambos os complexos por 1H RMN, ESI-MS e espectroscopia de absorção UV-Vis indicaram a presença de isômeros geométricos com perfis eletrônicos similares. Por outro lado, a análise eletroquímica por voltametria cíclica demonstrou menores potenciais Ru(III/II) quando comparados a complexos polipiridínicos análogos. Este potencial redox pode ainda ser catodicamente deslocado através da remoção de prótons dos grupos imidazóis do ligante ponte, possibilitando, dessa forma, a modulação das propriedades eletrônicas e catalíticas destes complexos de rutênio através de reações de protonação/desprotonação dos grupos -NH. Além disso, neste trabalho é investigada a inesperada formação do complexo [Ru(phtpy)2] nas reações do complexo [RuCl3(phtpy)] puro com ligantes bidentados, utilizando-se espectroscopia UV-Vis e de 1H RMN. / This work is focused on the development of dinuclear ruthenium complexes with potential application as catalysts for oxidation of water, that are characterized by a benzobisimidazole 2,6-bis(2-pyridyl)benzodiimidazole (dpimH2) bridging ligand, whose interaction between the metal centers as well as the electronic and catalytic properties can be tuned by acid-base reactions in that moiety. Thus, the preparation and characterization of the respective mononuclear species are described. The dinuclear complex [2(dpimH2)](Otf)2(phtpy=4-phenyl-2,2\':6\',2\'\'-terpiridine), in which two catalytic centers are covalently linked through that bridging ligand, and of the [(dpimH2)](ClO4)3 complex (where bpy=2,2\'-bypiridine) integrating a chromophore and a catalytic center in the same molecule as expected for a photocatalyst. The structural and electronic characterization of both complexes by NMR, ESI-MS and UV-vis spectroscopy indicated the presence of geometric isomers with similar electronic profiles. On the other hand, the electrochemical analysis by cyclic voltammetry displayed redox potential values for the Ru3+/Ru2+ couples lower than the respective polypyridyl complex counterparts. This redox potential can be even more shifted to less positive potentials by removal of protons from the imidazole groups in the bridging ligand, opening the possibility of tuning the electronic and catalytic properties of those ruthenium complexes based on protonation/deprotonation of the -NH groups. Furthermore, in this work is analyzed the unexpected formation of the bisterpyridine [Ru(phpy)2] complex in reactions starting with pure [RuCl3(phtpy)] complex with bidentated ligands, as through UV-Vis spectroscopy and RMN.

Este trabalho está focado no desenvolvimento de complexos de rutênio binucleares baseados no ligante ponte 2,6-bis(2-piridil)benzodiimidazol (dpimH2) com potencial aplicação como catalisadores para oxidação da água. O acoplamento eletrônico entre os centros metálicos bem como as propriedades eletrônicas e catalíticas podem ser controlados via reações ácido-base no ligante bis-bidentado. Dessa forma, neste trabalho descrevemos o preparo e a caracterização do respectivo composto mononuclear, bem como do complexo binuclear simétrico [{RuCl(phtpy)}2(dpimH2)](Otf) 2 (onde phtpy=4-fenil-2,2\':6\',\'\'-terpiridina), e do análogo assimétrico [{Ru(bpy)2}(dpimH2){Ru(phtpy)Cl}](ClO4)3 (onde bpy=2,2\'-bypiridina), que possui um centro catalítico e um grupo cromóforo na mesma molécula como esperado em um fotocatalisador, em que os dois centros catalíticos estão covalentemente conectados através do ligante ponte funcional. As caracterizações estrutural e eletrônica de ambos os complexos por 1H RMN, ESI-MS e espectroscopia de absorção UV-Vis indicaram a presença de isômeros geométricos com perfis eletrônicos similares. Por outro lado, a análise eletroquímica por voltametria cíclica demonstrou menores potenciais Ru(III/II) quando comparados a complexos polipiridínicos análogos. Este potencial redox pode ainda ser catodicamente deslocado através da remoção de prótons dos grupos imidazóis do ligante ponte, possibilitando, dessa forma, a modulação das propriedades eletrônicas e catalíticas destes complexos de rutênio através de reações de protonação/desprotonação dos grupos -NH. Além disso, neste trabalho é investigada a inesperada formação do complexo [Ru(phtpy)2] nas reações do complexo [RuCl3(phtpy)] puro com ligantes bidentados, utilizando-se espectroscopia UV-Vis e de 1H RMN. / This work is focused on the development of dinuclear ruthenium complexes with potential application as catalysts for oxidation of water, that are characterized by a benzobisimidazole 2,6-bis(2-pyridyl)benzodiimidazole (dpimH2) bridging ligand, whose interaction between the metal centers as well as the electronic and catalytic properties can be tuned by acid-base reactions in that moiety. Thus, the preparation and characterization of the respective mononuclear species are described. The dinuclear complex [2(dpimH2)](Otf)2(phtpy=4-phenyl-2,2\':6\',2\'\'-terpiridine), in which two catalytic centers are covalently linked through that bridging ligand, and of the [(dpimH2)](ClO4)3 complex (where bpy=2,2\'-bypiridine) integrating a chromophore and a catalytic center in the same molecule as expected for a photocatalyst. The structural and electronic characterization of both complexes by NMR, ESI-MS and UV-vis spectroscopy indicated the presence of geometric isomers with similar electronic profiles. On the other hand, the electrochemical analysis by cyclic voltammetry displayed redox potential values for the Ru3+/Ru2+ couples lower than the respective polypyridyl complex counterparts. This redox potential can be even more shifted to less positive potentials by removal of protons from the imidazole groups in the bridging ligand, opening the possibility of tuning the electronic and catalytic properties of those ruthenium complexes based on protonation/deprotonation of the -NH groups. Furthermore, in this work is analyzed the unexpected formation of the bisterpyridine [Ru(phpy)2] complex in reactions starting with pure [RuCl3(phtpy)] complex with bidentated ligands, as through UV-Vis spectroscopy and RMN.