Photolysis of <i>cis</i>(benzimidazole)(chloro)- bis(ethylenediamine)cobalt(III) in aqueous solution-Part 3^†

Abstract

The photolysis of <i>cis</i>(benzimidazole)(chloro)bis- (ethylenediamine)cobalt(llI) at 254 nm yields Co(II) and Cl^- as the major products. The quantum yield (φ)for Cl^- and Co(II) are <i>p</i>H dependent and a small period of irradiation dependence is observed. The zero time (extrapolated) values of φ₀ (Co^{2 +}) and φ₀ (Cl^- )are maximized at <i>p</i>H= 0.8 and 1 respectively. φ₀ (Cl^-) exceeds φ₀(Co²⁺) at <i>p</i>H<i>> </i> 0.5 indicating prevalence of photoaquation and photoreduction. At <i>p</i>H≤0.5, φ₀(Cl^-) is less than φ₀ (Co²⁺) which is presumed to be due to the solvent caged radical pair [Co(en)₂(bzmH) ....Cl]²⁺ undergoing CI substitution in the benzimidazole nucleus with cobalt(II) production.