Functionalization of Dimetal Complexes by Ligand Design

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Diiron-dioxygen and dicopper-dioxygen complexes play an important role in the reversible binding and activation of 0ィイD22ィエD2 in biological and catalytic processes. We developed various diiron(II) and dicopper(I) complexes as functional models for 0ィイD22ィエD2 transport proteins such as Hemerythrin (FeィイD22ィエD2) and hemocyanin (CuィイD22ィエD2) and monooxygenase such as methane monooxygenases (FeィイD22ィエD2 or CuィイD2nィエD2).Diiron Complexes : We have tried to control the thermal stability of μ-peroxo diiron(III) complexes against the irreversible oxidation and the dioxygen affinity of diiron(II) complexes by a series of dinucleating ligands. It was found that thermal stability toward irreversible oxidation and dioxygen affinity of those complexes are highly dependent on the stereochemistry and the electron donor ability of dinucleating ligands and bridging carboxylate. Finally we have succeeded in preparation and structural characterization of a cis-μ-l,2-peroxo diiron complex that binds 0ィイD22ィエD2 reversibly at ambient temperature.Dicopper Complexes : A series of copper(I) complexes ([Cu(L)]ィイD1+ィエD1) having tripodal tetradentate ligands (L) was synthesized and reactivity of their complexes with 0ィイD22ィエD2 was investigated. It was found that the nature and stereochemistry of the tripod ligands influence the formation, structures, and reactivity of copper-dioxygen complexes. We have succeeded in preparation of superoxocopper(II), μ-peroxodicopper(II), and bis(μ-oxo)dicopper(III) complexes. The bis(μ-oxo)dicopper(III) complex showed a monooxygenase activity for the coordinated ligand and also showed the reversible conversion with a precursor copper (I) complex by bubbling NィイD22ィエD2 gas. This is the first example which exhibit reversible conversion between bis(μ-oxo)dicopper(III) and copper(I) complexes.