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

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.