Electrooxidation of porphyrin free bases: fate of the π-cation radical

Abstract

In contrast to metalloporphyrins with non-electroactive metal centres, the π-cation radicals of porphyrin free bases (H₂OEP, H₂TPP, H₂CdiE) electrogenerated in strictly anhydrous solvents are not stable and give rise to a quantitative chemical reaction. Conjunction of electrochemical and spectroscopic data (UV/VIS, EPR and NMR) demonstrates unambiguously that the porphyrin skeleton is not modified during the chemical reaction. The reaction product is the protonated free base, and thus the free base can be regenerated by reduction of the protons.