Collect. Czech. Chem. Commun. 1994, 59, 1059-1065

Interaction of Mn(III)Tetraphenylporphyrin with Superoxide; The Reaction Mechanism and Evidence for a Peroxo Complex

Kamil Lang, Jiří Vondrák and Dana M. Wagnerová

Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 160 00 Prague 6, Czech Republic


Cathodic one-electron reduction of Mn(III)TPP and O2 in an aprotic solvent yields Mn(II)TPP and the superoxide anion radical O2-. The Mn(II)TPP and O2- react in solution to the side-on peroxo complex Mn(III)TPP-O22-, which is oxidized at the electrode at a peak potential of Epa = 0.40 V vs NHE (k ≈ 104 dm3 mol-1 s-1). The rate-determining step of the overall two-electron oxidation is the transfer of the first electron coupled with a structure rearrangement of the peroxo complex to a superoxo complex.