52781-49-4Relevant academic research and scientific papers
Transition-metal Complexes of Pyrrole Pigments. XXI. One-electron Oxidation of Water Mediated by a Cobalt(III)-Tetradehydrocorrin Complex
Murakami, Yukito,Aoyama, Yasuhiro,Tada, Toshito
, p. 2302 - 2308 (1981)
The cobalt(III) complex of tetradehydrocorrin (TDHC), having pKa1 6.15 and pKa2 11.50 for successive acid-dissociation of axial aqua ligands, undergoes auto-reduction to the cobalt(II) complex in aqueous carbonate solutions.Kinetic analysis of the reaction indicates the following mechanism: a one-electron transfer from the axial hydroxo ligand to the metal site, subsequent homolytic cleavage of the Co-OH bond, and finally scavenging of the resulting hydroxyl radical with the carbonate ion.At relatively low concentrations of the carbonate ion, the scavenging step is rate-determining; while at 2->1.0 * 10-2 mol dm-3 for III(TDHC)> of 7.62 * 10-5 -1.27*10-5 mol dm-3, the initial bond homolysis becomes rate-determining.Analysis of the kinetic data in reference to relevant electrode potentials indicates that the powerful oxidation ability of CoIII(TDHC) is responsible for one-electron oxidation of the hydroxo ligand.Reduction of CoIII(TDHC) also takes place in the absence of the carbonate ion, the apparent rate increasing with rise of pH in the range 11-12; deprotonation of the hydroxyl radical, which may prevent the hydroxyl radical and the cobalt(II) species from backward recombination, takes place.The one-electron oxidation of the hydroxo ligand was also significantly accelerated by addition of acetonitrile or t-butyl alcohol.
