Self-Promoted Electron Transfer from Cobalt Porphyrin to p-Fluoranil to Produce Dimer Radical Anion-Cobalt Porphyrin Complex

Abstract

Metal ions which act as Lewis acids can accelerate a number of electron transfer processes by complexation with radical anions, produced in the electron transfer. If substrate itself (S) can form a complex with the radical anion (S₂^-), the electron transfer reduction of the substrate (S) would be self-promoted, since the product (S₂^-) is thermodynamically more stabilized with increasing substrate concentration. We report herein the first example of self-promoted electron transfer from Co(II)OEP (2,3,7,8,12,13,17,18-octaethyl-21H,23H- porphine cobalt(II)) to p-fluoranil (F₄Q) due to the strong complex formation between the dimer radical anion [(F₄Q)₂^-] and Co(III)OEP⁺.