On the Catalase-Like Activity of α,β,γ,δ-Tetra(p-sulfonatophenyl)porphinato-Cobalt(III)

Abstract

The disproportionation of H₂O₂, catalyzed by the Co^III complex of tetraphenylporphine-tetra-p-sulfonate (TPPS), was investigated in the pH range 5 to 10 by measuring the initial rate, ν₀, of the increasing concentration of O₂ (25°, I = 0.1). In the pH range 5 to 7 ν₀ is proportional to [H⁺]^-1, in the pH range 7.5 to 9 ν₀ is independent of the pH, and in the whole pH range ν₀ is proportional to [Co^IIITPPS]. At pH 5.2 ν₀ is proportional to [H₂O₂]² and at pH 8.2 to [H₂O₂]. This is evidence that in the higher pH range the catalyst is present as a peroxo complex, Co^IIITPPS (OOH^-). A reaction scheme that is in accord with these results is suggested.