Unraveling and optimizing oxygen-oxygen bond formation pathways promoted by highly preoganized binuclear transition metal complexes

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The main goal of the project is to obtain a deep understanding of the different factors that influence the O-O bond formation reactions promoted by transition metal complexes. This understanding should then lead to the design and preparation of rugged and efficient water oxidation catalysts.To achieve this main goal it is proposed to prepare a family of highly preorganized binucleating pyrazolate based ligands and their Ru complexes. All the complexes will be thoroughly characterized from structural and spectroscopic point of view. Especially their redox properties will be studied in detail, since the water oxidation reaction involves multiple electron transfer processes. Higher oxidation states will be generated either chemically or electrochemically and their spectroscopic properties studied. Stability and reactivity of the complexes will be analyzed with a special attention to their water exchange reactions. The particular ligand design will allow to prepare complexes where the electronic properties as well as through-space interactions between the active groups can be controlled. This will enable to study and control the different reaction mechanisms that can potentially take place in the O-O bond formation reactions promoted by binuclear Ru complexes. Strong efforts will thus be devoted to study and understand reaction mechanism through which the O-O bond formation occurs in these systems, which includes a thorough kinetic analysis together with 18O labelling experiments. Catalytic systems will then be established and optimized, and the best catalysts in homogeneous phase will be heterogenized in inorganic solid supports. For this purpose new complexes, with intrinsically the same coordination properties but modified with an anchoring group, will be prepared and attached to inorganic oxides such as TiO2. Further extension of water oxidation chemistry to Fe and Mn complexes is also envisaged, but only in a preliminary manner while the Ru chemistry will be extensively developed and understood.