Photoredox processes in coordination compounds

Transition metal complexes display a number of charge-transfer bands in the absorption spectra. Optical excitation of the metal complexes produces a variety of products depending upon the nature of the excited state. Cobalt (III) ammine complexes on excitation in the CTTM bands produce cobalt(II) and oxidised ligand. Ruthenium(II) complexes on excitation in the cm. band leads to the oxidation of the metal centre. In certain reactions participation of the solvent in the primary photoredox reactions has also been reported. In recent years extensive investigations have been undertaken to utilize the photoredox systems of coordination compounds to convert solar energy to electricity or hydrogen