This project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is in the area of transition metal chemistry. The focus of the project is transition metal complexes of quinone ligands. Catecholate and o-semiquinone ligands have electronic levels which are close in energy to metal levels, but which remain discrete in the electronic structure of the complex. Quinone complexes often show intense, low-energy charge transfer transitions corresponding to transfer of electrons between ligand and metal orbitals. Effects which influence the relative energy of metal and quinone have been investigated in the interest of defining parameters which may be used to tune the energy separations, and it has been shown that the factors which determine the charge distribution between metal and quinone ligands include metal orbital energy, the identities of the other ligands and the overall charge of the complex. These studies will be extended to planar quinone complexes which show strong intermolecular interactions between metals and between quinone ligands. The photomechanical and conductive properties of these complexes will be investigated, with a focus on their application as discotic mesophase liquid crystals. Destabilization of oxo ligands of oxometal cathecholate complexes by irradiation of the cathecholate-to-metal CT band will be studied in systems which exhibit oxygen atom transfer reactions, olefin epoxidation and photochemical water oxidation. Learning how to tune the properties of metal atoms by changing the molecules to which they are bound is critical to controlling their function in catalysts and in coming to a better understanding of their function in biological systems.
