Photochemical reduction of cerium(IV) porphyrin sandwich complexes
Abstract
Irradiation of cerium(IV) complexes of 5,10,15,20-tetraphenyl- and 2,3,7,8,12,13,17,18-octaethyl-porphyrin (H2tpp and H2oep, respectively) with visible light, in the presence of triethylamine as an electron donor, leads to their photoreduction. The process was followed using electron absorption and ESR spectros-copies. Photoirradiation of [CeIV{tpp(–2)}2] resulted in the formation of [CeIII{tpp(–2)}{tpp(–2)}]–. The reverse oxidation of this compound with chloroform as an electron acceptor was also observed. The photoreduction of [CeIV{oep(–2)}{oep(–2)}] was more complicated, giving rise to the photoreduced neutral complex [CeIII{oep(-1)}{oep(–2)}] which exhibits an ESR spectrum typical of lanthanoid(III) bis(porphyrinates).