title: Catalytic water oxidation by ruthenium(II) quaterpyridine (qpy) complexes: evidence for ruthenium(III) qpy-N,N'''-dioxide as the real catalysts.
abstract: Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation-resistant and can stabilize high-oxidation-state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2 ](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze Ce(IV) -driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy-N,N'''-dioxide (ONNO) complexes [Ru(ONNO)(L)2 ](3+) which are the real catalysts for water oxidation.
authors.affiliation: Department of Biology and Chemistry; Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China).
authors.forename: Yingying
authors.initials: Y
authors.lastname: Liu
authors.forename: Siu-Mui
authors.initials: SM
authors.lastname: Ng
authors.forename: Shek-Man
authors.initials: SM
authors.lastname: Yiu
authors.forename: William W Y
authors.initials: WW
authors.lastname: Lam
authors.forename: Xi-Guang
authors.initials: XG
authors.lastname: Wei
authors.forename: Kai-Chung
authors.initials: KC
authors.lastname: Lau
authors.forename: Tai-Chu
authors.initials: TC
authors.lastname: Lau
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011725:Pyridines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D011725:Pyridines; D014867:Water; D012428:Ruthenium; C023666:pyridine
keywords: density functional calculations; homogeneous catalysis; polypyridyl ligands; ruthenium complexes; water oxidation