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 scavengin g techniques, has been employed together with UV VIS spectroscopy to e stablish that iron(III) tetra(N-methylpyridyl)porphyrins ligated to ca rboxylate anions undergo ready photodissociation with light in the vis ible region of the spectrum. Studies conducted as a function of pH and for a variety of carboxylic acids provide evidence for initial photod ecomposition to give Fe(II) and acyloxyl radicals, for which recombina tion competes with decarboxylation to give alkyl radicals. The roles o f oxygen and the structure of the initial complex have been explored.