PHOTOCATALYTIC REACTIONS OF PORPHYRIN-BASED MULTIELECTRON TRANSFER SENSITIZERS

Individual metal centers assisted by redox-active ligands can serve as active sites for photocatalytic multielectron transfer (MET) substrat e transformations. In porphyrin-based mononuclear systems, the primary steps of excitation and charge stabilization are mediated by the tetr apyrrole ligand acting both as photosensitizer and intermediate charge reservoir. Accumulation and transfer of multiple redox equivalents re quires a binding site that provides at least two stable oxidation stat es separated by more than one unit. The reversible photoconversion bet ween low- and high-valent antimony porphyrins is described as an examp le of MET sensitization. (C) 1998 Elsevier Science S.A.