Complex inorganic active sites perform challenging catalytic transformations in biological systems, such as water oxidation by Photosystem II and nitrogen reduction in Nitrogenase. The effect of cluster structure on the physical and chemical properties of these active sites is not well understood. We have developed methodologies for the rational synthesis of tetranuclear homo- and hetero-metallic cluster models of protein active sites, which allow for systematic structure-property studies. Distal redox changes have been demonstrated to have a substantial effect on the reactivity and binding of ligands relevant to small molecule conversions. Upon incorporation of second coordination sphere hydrogen bonding interactions, water oxidation catalysis was observed. Spectroscopic studies of models with structures or redox states relevant to the protein active site provide benchmarking for the biological system. Implications for function and spectroscopy will be discussed.








Theo Agapie (Caltech)