Reactions of cobalt(III) compounds with some free radicals derived from uracil

Abstract

Reactions of Co^III complexes with the transient adducts of uracil (U), viz. U^–, UH and UOH, have been studied by means of γ-radiolysis of uracil in the presence of Co^IIIEDTA and Co^IIINTA (where EDTA is ethylenediamine tetra-acetate and NTA is nitrilotriacetate). The U^– and UH radicals formed by the reactions of e^–_aq and H with uracil reduce Co^III to Co^II complexes. The UOH radicals, however, do not reduce the Co^III complexes although such reductions have been observed with Cu^II and Fe^III analogues as reported earlier. The absence of such electron transfer from UOH to Co^III could not be explained on the basis of the redox potential of the Co^IIIEDTA/Co^IIEDTA couple, which was 0.38 V. However, this apparent anomaly has been explained on the basis of the individual structures of the respective complexes.