Toward Functional Ni-SOD Biomimetics: Achieving a Structural/Electronic Correlation with Redox Dynamics

We have prepared and characterized a Ni complex with an N(3)S(2) ligand set (1) that represents the first isolable synthetic model of the reduced form of the Ni-SOD (SOD = superoxide dismutase) active site featuring all relevant donor functionality in the proper spatial distribution. As revealed by X-ray crystallography, the axial py-N donor of 1 does not bind Ni(II) in the solid state or in solution like SOD. Oxidation of 1 provides a disulfide-linked dinuclear species, [{Ni(N(3)S(2))}(2)] (2), which we have isolated and characterized. Moreover, the 1 → 2 conversion is reversible, much like redox cycling in the enzyme.