Dismutation of superoxide ion in an aprotic solvent by 5,10,15,20-tetra-p-tolylporphyrinatocobalt(II)

Abstract

The reactions of superoxide ion, O2–, with 5,10,15,20-tetra-p-tolylporphyrinatocobalt(II), [Co(tptp)], were investigated by spectroscopic methods (u.v.–visible and e.s.r.). The visible spectrum of [Co(tptp)] in dimethyl sulphoxide (dmso) was red shifted upon successive addition of O2– solutions. The initial reaction product is the superoxo-complex [Co(tptp)(O2)]–, the formation of which was confirmed by e.s.r. measurements. The superoxo-complex subsequently reacts via intramolecular electron transfer to give [Co(tptp)]+ and HO2–. In turn, [Co(tptp)]+ oxidizes superoxide ion, present in the medium, to yield O2. These results reveal that this cobalt porphyrin complex, in dmso, may function as an efficient catalyst for dismutation of superoxide (2O2– [graphic omitted] O2+ HO2–:HX = proton source).