Biomimetic catalysis is an important research field, as a better understanding of nature´s powerful toolbox for the conversion of molecules can lead to technological progress. [FeFe]-hydrogenases are very efficient catalysts for hydrogen production. These enzymes play a crucial role in the metabolism of green algae and certain cyanobacteria. Their active site consists of a diiron complex that is embedded in an interactive protein matrix. In this thesis, two pathways for mimicking the outer coordination sphere effects resulting from the protein matrix are explored. The first is the construction of model complexes containing phosphine ligands that are coordinated to the iron center as well as covalently linked to the bridging ligand of the complex. The effect of such linkers is an increased energy barrier for the rotation of the Fe(CO2)(PL3)-subunit, which potentially could stabilize a terminal hydride that is an important intermediate in the proton reduction cycle. The second pathway follows the incorporation of [FeFe]-hydrogenase active site model complexes into metal-organic frameworks (MOFs). Resulting MOF-catalysts exhibit increased photocatalytic activity compared to homogenous references due to a stabilizing effect on catalytic intermediates by the surrounding framework. Catalyst accessibility within the MOF and the influence of the framework on chemical reactivity are examined in the work presented. Furthermore, an initial step towards application of MOF-catalysts in a device was made by interfacing them with electrodes. The work of this thesis highlights strategies for the improvement of biomimetic model catalysts and the knowledge gained can be transferred to other systems mimicking the function of enzymes.

Les hydrogénases [FeFe] sont des métalloenzymes capables de catalyser de façon réversible la production et l’oxydation du dihydrogène. Depuis que la structure du site actif des hydrogénases [FeFe] a été déterminée, de nombreux modèles bio-inspirés ont été élaborés et étudiés en vue de comprendre et de reproduire le fonctionnement de cette classe d’enzyme. Le site actif des hydrogénases [FeFe], le cluster-H, présente un état entatique caractérisé par une conformation particulière permettant d’activer efficacement la conversion H+/H2. Dans la littérature, très peu de modèles reproduisant une telle conformation dans l’état réduit Hred (FeIFeI) du site actif ont été décrits. Notre équipe a obtenu récemment un complexe FeIFeI de formule [Fe2(CO)4(ҡ 2-dmpe)(μ-adtBn)] (adtBn= {SCH2}2NCH2C6H5, dmpe = (CH3)2PCH2-CH2P(CH3)2), présentant une conformation ‘inversée’, à l’état solide, permettant de mimer la géométrie particulière du cluster-H. Cette conformation est stabilisée dans ce dérivé par la présence d’un pont dithiolate encombré, d’une liaison agostique et par la coordination dissymétrique d'un ligand bidentate bon σ-donneur. Les travaux de cette thèse ont été consacrés à l’étude du comportement électrochimique en oxydation de ce composé, [Fe2(CO)4(ҡ2-dmpe)(μ-adtBn)], dans différents solvants et en présence de substrats, comme CO, RNC et P(OMe)3, en vue de comprendre les mécanismes impliqués dans ces processus redox. Les oxydations chimiques du complexe [Fe2(CO)4(ҡ2-dmpe)(μ-adtBn)] ont permis de compléter l’identification des espèces formées qui ont été caractérisées par différentes méthodes spectroscopiques (IR, RMN) et par diffraction des rayons X. / [FeFe]-Hydrogenases are metalloenzymes having the capacity to catalyze efficiently both the production of H2 and its oxidation. Since the structure of the active site of [FeFe]-Hydrogenases has been determined, many bio-inspired models have been synthesized and studied to understand and to mimick the functioning of this class of enzyme. The active site of the [FeFe]-hydrogenases, the Hcluster, presents an entatic state characterized by a particular conformation that allows an efficient H+/H2 conversion. Very few models mimicking such a conformation in the reduced state, Hred (FeIFeI), of the active site have been described in the literature. Our group recently obtained a FeIFeI complex [Fe2(CO)4(k2-dmpe)(μ-adtBn)] (adtBn = {SCH2}2NCH2C6H5, dmpe = (CH3)2PCH2-CH2P(CH3)2), having an 'inverted' conformation, in the solid state, that mimicks the particular geometry of the H-cluster. This conformation is stabilized in this derivative by the presence of a crowded dithiolate bridge, an agostic interaction and the dissymmetrical coordination of a chelating good σ-donor ligand. The works in this thesis have been devoted to the study of the electrochemical properties in oxidation of the complex [Fe2(CO)4(k2-dmpe)(μ-adtBn)] in various solvents and in the presence of substrates, such as CO, RNC, P(OMe)3, in order to understand the mechanisms involved in these redox processes. The chemical oxidations of the complex [Fe2(CO)4(k2-dmpe)(μ-adtBn)] have been also performed in order to identify the species formed by oxidation. They were characterized using various spectroscopic methods (IR, NMR) and X-ray diffraction.