In nature, transition metal containing enzymes display many biologically important, attractive and efficient catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in nature, namely, the cytochrome P450 enzymes. Ruthenium porphyrin complexes have been the center of this research and have successfully been utilized, as catalysts, in major oxidation reactions, such as the hydroxylation of alkanes. The present work focuses on photocatalytic studies of aerobic oxidation reactions with well characterized ruthenium porphyrin complexes. The photocatalytic studies of aerobic oxidation reactions of hydrocarbons The photocatalytic studies of aerobic oxidation reactions of hydrocarbons catalyzed by a bis-porphyrin-ruthenium(IV) μ-oxo dimer using atmospheric oxygen as the oxygen source in the absence of co-reductants were investigated. The ruthenium(IV) μ-oxo bisporphyrin (3a-d) was found to catalyze aerobic oxidation of a variety of organic substrates efficiently. By comparison, 3d was found to be a more efficient photocatalyst than the well-known 3a under identical conditions. A KIE at 298K was found to be larger than those observed in autoxidation processes, suggesting a nonradical mechanism that involved the intermediacy of ruthenium(V)-oxo species as postulated. The reactivity order in the series of ruthenium(IV) μ-oxo bisporphyrin complexes follows TPFPP>4- CF3TPP>TPP, and is consistent with expectations based on the electrophilic nature of the ruthenium(IV) μ-oxo bisporphyrin species. The trans-dioxoruthenium(VI) porphyrins have been among the best characterized metal-oxo intermediates and their involvement as the active oxidant in the hydrocarbon oxidation have been extensively studied. In addition to the well-known chemical methods, we developed a novel approach for generation of trans-dioxoruthenium( VI) porphyrins with visible light by extension of the known photoinduced ligand cleavage reactions. A series of trans-dioxoruthenium(VI) porphyrin complexes (6a-d) were photochemically synthesized and spectroscopically characterized by UV-vis, and 1H-NMR.

Highly reactive iron-oxo intermediates play important roles as active oxidants in enzymatic and synthetic catalytic oxidation. Many transition metal catalysts are designed for biomimetic studies of the predominant oxidation catalysts in Nature, namely cytochrome P450 enzymes. In this work, a series of iron(IV)-oxo porphyrins [FeIV(Por)O] and manganese(IV)-oxo porphyrins [MnIV(Por)O] have been successfully produced in two electron-deficient ligands by photochemical and chemical methods, and spectroscopically characterized by UV-vis, and 1H-NMR. With iodobenzene diacetate [PhI(OAc)2] as the oxygen source, iron(III) porphyrin and manganese(III) porphyrin complexes converted to the corresponding metal(IV)-oxo species as oxygen atom transfer (OAT) agents. In addition, a new photochemical method was developed to generate the same species by visible light irradiation of highly photo-labile porphyrin-iron(III) bromate or porphyrin-manganese(III) chlorate precursors. Furthermore, the kinetics of oxygen transfer atom reactions with alkene, active hydrocarbons and aryl sulfides by photo-generated and chemical-generated [FeIV(Por)O]were studied in CH3CN solutions. Apparent second-order rate constants determined under pseudo-first-order conditions for sulfide oxidation reactions are (9.8 ± 0.1) × 102 − (3.7 ± 0.3) × 101 M-1s-1, which are 3 to 4 orders of magnitude greater in comparison with those of alkene epoxidations and activated C-H bond oxidations by the same oxo species.

L’oxydation catalytique des liaisons C-H, en condition aérobie est l’une des réactions « phare » de la chimie, aussi bien d’un point de vue fondamental qu’industriel. Le principal défi consiste en l’utilisation de l’oxygène moléculaire comme oxydant « vert » pour l’activation de ces liaisons C-H. De nombreuses métalloprotéines, telles que les mono-oxygénases (Fe, Cu), sont capables de réaliser ces réactions dans des conditions douces. Une stratégie actuelle consiste à développer des systèmes synthétiques capables de reproduire de manière efficace les propriétés catalytiques de ces enzymes. L’objectif principal de nos travaux a été de synthétiser et de caractériser des modèles de mono-oxygénases solubles (sMMO) et membranaires (pMMO). Deux approches ont été développées. La première a consisté à élaborer des ligands ditopiques dissymétriques, dont les deux sites de coordination tris-(2-pyridymethyl)amine “TPA” et pyridinedicarboxamide “PydCA”, sont enclavés dans un seul macrocycle afin de favoriser une distance intermétallique optimale. La seconde stratégie est basée sur la synthèse de ligands ditopiques où les motifs coordinants, tetraazacyclotetradecane “cyclam” et dipicolylamine “DPA”, sont séparés par un espaceur de type phényle. Ces deux approches ont conduit à l’obtention et à la caractérisation, à l’état solide (structure aux rayons X) et en solution (spectroscopie, électrochimie), de nombreux complexes mono et dinucléaires du fer, du cuivre et du cobalt. L’étude de la réactivité de certains complexes mononucléaires vis-à-vis des oxydants tels que O2 et H2O2, en l’absence de substrats organiques, a permis d’identifier des espèces métal-oxygène. L’oxydation catalytique de substrats organiques a également été réalisée. / Catalytic oxydation of C-H bonds using molecular oxygen as ‘green’ oxidant remains a great challenge from both fundamental and industrial point of views. Many metalloproteins, such as copper end iron-based mono-oxygenases are able to perform these reactions under mild conditions. A current strategy is to develop synthetic complexes which can reproduce the efficiency of such enzymes. The main objective of our work has been to synthesize and characterize new models of soluble (sMMO) and particulate (pMMO) mono-oxygenases. Two approaches have been developed. The first strategy was to synthesize unsymmetrical dinucleating ligands bearing two coordination sites, tris-(2-pyridylmethyl)amine “TPA” and pyridinedicarboxamide “PydCA”, which are embedded in a single macrocycle to favor intermetallic interaction. The second strategy is based on the synthesis of dinucleating ligands where coordinating patterns, tetraazacyclotetradecane “cyclam” and dipicolylamine “DPA”, are separated by a phenyl type spacer. These two approaches have led to the formation and characterization in the solid state (X-ray structure) and in solution (spectroscopy, electrochemistry) of many mononuclear and dinuclear iron, copper and cobalt complexes. The study of the reactivity of some mononuclear complexes towards oxidants such as O2 and H2O2, in absence of organic substrates, has led to the identification of metal-oxygen species. Catalytic oxidation of organic substrates was also conducted.

Les processus d’oxydation et d’amination sont très importants dans le monde de l’industrie mais les procédés actuels sont polluants. Afin de réaliser ces transformations de manière catalytique et propre, les réactions bioinspirées par transfert d’atome d’oxygène (TAO) et d’azote (TAN) ont été étudiées. La formation de l’espèce active à haut degré d’oxydation étant bien connue dans le cas des TAO, l’enjeu se situe dans le design des ligands. Dans le cas des TAN, cette étape est moins bien étudiée, limitant le développement de nouveaux catalyseurs. Enfin, l’utilisation d’une source d’énergie lumineuse, et non plus chimique, est recherchée afin de diminuer les déchets produits lors de ces réactions.Deux stratégies ont été mises en œuvre au cours de ce projet. Pour l’étude des réactions par TAO, deux nouveaux jeux de ligands, similaires aux porphyrines et aux BODIPY, ont été synthétisés. L’obtention et la caractérisation des complexes de ruthénium ainsi que leur réactivité par oxydation chimique ou électrochimique ont été réalisées. Pour les réactions de TAN, le mécanisme du dimère connu Rh2(esp)2 de type PCET (transfert couplé de proton et d’électron), semblable à celui des réactions par TAO, a été étudié en identifiant les différents intermédiaires formés grâce à une étude spectro-électrochimique. Ces différentes étapes ont ensuite été réalisées par voie photochimique développant ainsi l’utilisation de l’énergie lumineuse pour réaliser des réactions de TAO et TAN de manière éco-compatible. / Processes of oxidation and amination hold an important place on an industrial level but the current available methods are polluting and non-sustainable. To perform these transformations in the contour of green catalysis, bio-inspired oxygen atom transfer (OAT) and nitrogen atom transfer (NAT) reactions were addressed. In the case of OAT, the mechanism for the formation of the active species, the highly oxidized metal-oxo, is rather well described, and the challenge relies in the design of ligands to stabilize such species. For NAT, this step is less studied which limits the development of new catalysts. An even more challenging task resides in the use of light energy to generate these active species in the perspective to replace the classic oxidants. During this thesis, two projects have been undertaken. Firstly, the synthesis of dipyrrin based ligands and the corresponding ruthenium complex was evaluated for their ability to perform OAT reactions using conventional oxidants or the electrochemical way. Regarding the NAT reactions, we have investigated on the electrochemical, chemical and photochemical activation of the known catalyst Rh2(esp)2. Our strategy consisted in the activation of the nitrogen atom donor substrate, the sulfonamidate, in the coordination sphere of the catalyst. We disclose the spectroscopic signatures for the stepwise activation of the catalyst-substrate form. This work has as objective to set us on the path to develop a sustainable way to perform these reactions.