Photoredox processes in the 254-nm photochemistry of chromium(III) ammine complexes

The photochemical reactions of a series of chromium(III) ammine complexes have been studied following excitation at 254 nm in three different supporting electrolytes and in oxygenated and deoxygenated solutions. In addition to ligand substitution reactions, redox processes are observed when O 2 is present or, in NO 3 - media, when O 2 is absent. An ion-pair model is proposed to explain the dependence of the yield for the redox process on ion charge, supporting electrolyte, and nature of the coordinated ligands. At least two excited states are involved in the observed photochemistry