FE XAS L2,3 EDGE STUDIES OF NON HEME IRON ENZYMES

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We propose to study the geometric and electronic structure of non-heme mononuclear and dinuclear iron enzymes using Fe L-edge X-ray absorption spectroscopy. Current studies at the Fe K-edge are limited by certain characteristics of the experiment. The 1s.3d transition is electric dipole forbidden and the energy resolution at the Fe K-edge is of the same order of magnitude as splittings of the d-orbitals by a ligand field. In contrast, at the metal L2,3-edges 2p.3d transitions are electric dipole allowed, providing a direct probe of the energy levels and populations of the d-orbitals. A systematic study of Fe L-edge spectra of model compounds with varying ligation, geometries and oxidation states will be used to develop a basis of understanding which will be applied to the active sites in mononuclear and dinuclear non-heme iron enzymes.