Gamma Radiolysis of Cu(II) Complex of Metronidazole

Aqueous solutions of Cu(II) Metronidazole (CuIIM) at neutral pH were irradiated with 60Co ?-rays under different conditions of radiolysis. The radiolytic formation of HNO2and CuIwas followed. The radiolytic yields of chromophore loss of CuIIM were also determined under different conditions. The OH radicals attack the metal complex to give the OH adducts of the ligand at C2, C4, and C5either directly or through the formation of Cu(III) species. The C5–OH adduct, however, undergoes oxidative denitration and as a result the metal complex is decomposed. The OH adducts also undergo electron transfer to CuIIion to give reduced complex. No denitration was observed due to the reaction of eeq-with the metal complex. On the other hand, the nitro group of the ligand in the complex undergoes successive 4-electron reduction to give hydroxylamino derivative. From the competition kinetics using t-butyl alcohol as the scavenger of OH in N2O saturated solution of the metal complex, the rate constant for the reaction of OH with complex was evaluated to be ca. 2.1×109dm3mol-1s-1which is of the same order as that observed in the case of free metronidazole.