The Nature of the Bonding and Valency for Oxygen in Its Metal Compounds

The interactions of superoxide ion(O2-.) with metallo-porphyrins [(C1(8)TPP)M, M = Fe,Mn,Co Zn]; models for biological systems and superoxide dismutases

In dimethylformamide superoxide ion forms a 1:1 adduct with tetrakis (2,6-dichlorophenyl) porphinato-iron, (C1(8)TPP)FeOO-, as well as with its manganese analogue, (C1(8)TPP)MnOO-. On the basis of their electrochemical, spectroscopic, and magnetic properties these adducts have a metal-oxygen covalent bond (PorM-OO-), oxygen-centered redox chemistry, and reactivities that are similar to the hydroperoxide ion (HOO-). Addition of -OH to a solution of PorFe and O2 results in the formation of PorFe(OH)(OO-), which can be electrochemically oxidized to PorFeOH plus O2 (-0.2 V vs SCE). Addition of protons to the PorM-OO- adducts promotes their rapid decomposition to PorM, HOOH, and O2. This chemistry provides insight to the reactions of biological superoxide and superoxide dismutases.