Oxidation of copper(II) bis(glycinate) by methyl free radicals in aqueous solutions. A pulse-radiolysis study

The reaction of -CH3 free radicals with Cun(NH₂CH₂CO₂)₂ in aqueous solutions was studied. The formation of the unstable intermediate (NH₂CH₂CO₂)₂Culn-CH₃(aq) in this reaction was observed. This intermediate decomposes into Cu111-(NH₂CH₂CO₂)²⁺(aq) + CH₄. The formation of Cum(NH₂CH₂COf)²⁺(aq) is not observed, as this complex is short-lived under these conditions and decomposes via ligand oxidation. The *CH₃ free radicals react with the transient complex (NH₂CH₂CO₂)₂Cum-CH₃(aq) to form ethane and CuM(NH₂CH₂COf)₂; the specific rate of this reaction approaches the diffusion-controlled limit. The results thus point out that aliphatic free radicals can oxidize copper(Il) complexes to copper(HI) complexes. The results suggest that the reactions of aliphatic free radicals with copper complexes might cause the reported radiosensitization by copper compounds.