One-Electron Oxidation of Metalloporphycenes As Studied by Radiolytic Methods

Abstract

One-electron and two-electron oxidations of 2,7,12,17-tetrapropylporphycene (H2TPrPc) and its Fe, Co, Ni, Cu, and Sn complexes in CH2Cl2, CCl4, and 2-PrOH solutions have been studied by radiolytic techniques. Formation and decay of intermediates formed upon one-electron oxidation have been followed by kinetic spectrophotometric pulse radiolysis, and the absorption spectra of stable oxidation products have been recorded following γ-radiolysis. H2TPrPc is oxidized to the π-radical cation and then to the dication, which is stable in aprotic solvents but is transformed to a different product in 2-PrOH. Similar oxidation to the π-radical cation and then to the dication was observed for the CuII, SnIV, CoIII, and FeIII porphycenes. CoII and NiII porphycenes underwent radiolytic oxidation to form stable CoIII and NiIII products. The stability of the latter is in contrast with previous electrochemical observations, and the difference is ascribed to the effect of the axial ligand.