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).