Photochemical decomposition of EDTA coordinated to cobalt(III): products, thermal reactions, and evidence for outer sphere alcohol oxidation by the excited state

Abstract

The photolysis of Co(EDTA)− in the ultraviolet is unlike analogous reactions of Fe(III) complexes. The ratio of products Co(II) to CO2 is 1:1 but we find only [Formula: see text] as much CH2O. For Fe(EDTA)−, yields of photolysis products Fe(II):CO2:CH2O are 2:1:1. This is consistent only with a mechanism where primary photolysis yields Co(II), CO2, and a radical which attacks EDTA in preference to reduction of the slowly reducible metal oxidation state, Co(III). Use of 2-propanol as a scavenger diagnostic of primary radicals is questioned because it is shown that LMCT excited states of Co(III) complexes exhibit the same outer sphere oxidations of alcohols earlier recognized in the photochemistry of a variety of Fe(III) complexes.