Mechanistic Studies on the Role of [CuII(CO3)n]2−2n as a Water Oxidation Catalyst: Carbonate as a Non-Innocent Ligand

Amir Mizrahi, Eric Maimon, Haim Cohen, Haya Kornweitz, Israel Zilbermann, Dan Meyerstein

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Recently it was reported that copper bicarbonate/carbonate complexes are good electro-catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n 3−2n complexes are the active intermediates in the electrolysis of CuII(CO3)n 2−2n solution. The results enable the evaluation of E°[(CuIII/II(CO3)n)aq]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single-electron transfer from CuIII(CO3)n 3−2n to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to CuIII results in the formation of C2O6 2− by means of a second-order reaction of CuIII(CO3)n 3−2n. The results point out that carbonate stabilizes transition-metal cations at high oxidation states, not only as a good sigma donor, but also as a non-innocent ligand.

Original languageEnglish
Pages (from-to)1088-1096
Number of pages9
JournalChemistry - A European Journal
Issue number5
StatePublished - 24 Jan 2018


  • carbonate
  • copper
  • non-innocent ligands
  • pulse radiolysis
  • water oxidation


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