2014年4月
Water Oxidation Chemistry of a Synthetic Dinuclear Ruthenium Complex Containing Redox-Active Quinone Ligands
INORGANIC CHEMISTRY
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- ,
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- 巻
- 53
- 号
- 8
- 開始ページ
- 3973
- 終了ページ
- 3984
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1021/ic402340d
- 出版者・発行元
- AMER CHEMICAL SOC
We investigated theoretically the catalytic mechanism of electrochemical water oxidation in aqueous solution by a dinuclear ruthenium complex containing redox-active quinone ligands, [Ru-2(X)(Y)(3,6-tBu(2)Q)(2)(btpyan)](m+) [X, Y = H2O, OH, O, O-2; 3,6-tBu(2)Q = 3,6-di-tert-butyl-1,2-benzoquinone; btpyan = 1,8-bis(2,2':6',2"-terpyrid-4'-yl)anthracene] (m = 2, 3, 4) (1). The reaction involves a series of electron and proton transfers to achieve redox leveling, with intervening chemical transformations in a mesh scheme, and the entire molecular structure and motion of the catalyst 1 work together to drive the catalytic cycle for water oxidation. Two substrate water molecules can bind to 1 with simultaneous loss of one or two proton(s), which allows pH-dependent variability in the proportion of substrate-bound structures and following pathways for oxidative activation of the aqua/hydroxo ligands at low thermodynamic and kinetic costs. The resulting bis-oxo intermediates then undergo endothermic O-O radical coupling between two Ru(III)-O-center dot units in an anti-coplanar conformation leading to bridged mu-peroxo or mu-superoxo intermediates. The mu-superoxo species can liberate oxygen with the necessity for the preceding binding of a water molecule, which is possible only after four-electron oxidation is completed. The magnitude of catalytic current would be limited by the inherent sluggishness of the hinge-like bending motion of the bridged mu-superoxo complex that opens up the compact, hydrophobic active site of the catalyst and thereby allows water entry under dynamic conditions. On the basis of a newly proposed mechanism, we rationalize the experimentally observed behavior of electrode kinetics with respect to potential and discuss what causes a high overpotential for water oxidation by 1.
- リンク情報
- ID情報
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- DOI : 10.1021/ic402340d
- ISSN : 0020-1669
- eISSN : 1520-510X
- PubMed ID : 24694023
- Web of Science ID : WOS:000334902400007