FUNCTIONAL MODELS FOR MMOH--REACTIVITY AND MECHANISM

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The correlation between the structural features and the function of methane monooxygenase (MMO) remains to be elucidated. Most of model studies of MMO hydroxylase (MMOH) have focused primarily on structure and physical properties, with less emphasis on dioxygen reactivity, and few system was reported on the substrate oxidation reactions. The research proposal is directed toward the development of new diiron(II) complex system as functional models for MMOH, based on a unifying hydroxylation mechanism proposed. The approach begins with the construction of a dinuclear coordination ligand system with a porphyrin unit that is expected to serve as not only a spacer for the completion of the desired reaction by virtue of the redox properties of metalloporphyrins. The two iron(II) centers in a single molecule separated with certain distance and possessing coordination sites will be used for reactivity studies including dioxygen reaction and subsequent substrate oxidation, especially methane conversion. A Si-supported diiron complex system will be constructed to mimic the biological system in which the protein framework protects reactive intermediates formed in the metal active sites, preventing their decomposition by bimolecular pathways involving other metal complexes. The long-term objective of this proposal is to identify an efficient, catalytic system for the conversion of methane to methanol using dioxygen as an oxidant under mild conditions through detailed thermodynamic and kinetic-mechanistic studies of MMO system. It is hoped that the outcome of this study will be promising in a world where environmental pollution is a major concern.