The photochemical reaction of tris(ethylenediamine)cobalt(III) ion with ferrocyanide

Abstract

The photochemical formation of [Cl(en)2Co—N≡C—Fe(CN)5]2− from Co(en)33+ and Fe(CN)64− is explored. Earlier evidence established that the reaction proceeds via electron transfer. Ligand field Co(III) excited states are clearly indicated to be effective. There is evidence that free Fe(CN)64− can scavenge these excited states or their successors arising in ion pairs with Fe(CN)64−. This suggests that the reactive excited state lifetime is at least comparable to the rate of diffusional encounters. However, racemization does not accompany reaction if (+)589Co(en)33+ is the reactant. Wavelength studies indicate approximate wavelength independence as far as 647.1 nm. These results are in contrast with the behaviour of photosubstitution yields for Co(III) amines.