ChemInform Abstract: Photoinitiated Two-Electron Oxidation of Tris(1,10-phenanthroline)vanadium(II).

ChemInform Abstract

The photooxidation of the title complex (I) results in formation of the V(III) dimer (II) which is stable in acidic solution. This is the first system in which the undesirable electron-back-transfer reaction, which ordinarily follows the primary photoredox process, is inhibited by the formation of a stable dimeric species. The mechanism of this irreversible photooxidation is studied by electrochemical methods. In basic solutions the dimer (II) is capable of carrying out a second thermal electron transfer. The combination of these processes shows that visible irradiation of (I) and the electron acceptor methylviologen MV²⁺ at pH 8 leads to rapid formation of MV+ and VO²⁺ (identified by ESR). Thus the photooxidation of (I) by one electron is followed by a spontaneous second electron transfer. These results represent the first example of photoinitiated two-electron oxidation at a single metal center.