Photolytic cleavage of the iron–carboxyalkyl ligand bond in some iron(III) tetra(N-methylpyridyl)porphyrins: evidence for reversible photodecomposition and fragmentation from EPR and UV spectroscopy

Abstract

EPR spectroscopy, in conjunction with spin-trapping and spin-scavenging techniques, has been employed together with UV–VIS spectroscopy to establish that iron(III) tetra(N-methylpyridyl)porphyrins ligated to carboxylate anions undergo ready photodissociation with light in the visible region of the spectrum. Studies conducted as a function of pH and for a variety of carboxylic acids provide evidence for initial photodecomposition to give Fe^II and acyloxyl radicals, for which recombination competes with decarboxylation to give alkyl radicals. The roles of oxygen and the structure of the initial complex have been explored.