title: Water oxidation catalyzed by mononuclear ruthenium complexes with a 2,2'-bipyridine-6,6'-dicarboxylate (bda) ligand: how ligand environment influences the catalytic behavior.
abstract: A new water oxidation catalyst [Ru(III)(bda)(mmi)(OH2)](CF3SO3) (2, H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; mmi = 1,3-dimethylimidazolium-2-ylidene) containing an axial N-heterocyclic carbene ligand and one aqua ligand was synthesized and fully characterized. The kinetics of catalytic water oxidation by 2 were measured using stopped-flow technique, and key intermediates in the catalytic cycle were probed by density functional theory calculations. While analogous Ru-bda water oxidation catalysts [Ru(bda)L2] (L = pyridyl ligands) are supposed to catalyze water oxidation through a bimolecular coupling pathway, our study points out that 2, surprisingly, undergoes a single-site water nucleophilic attack (acid-base) pathway. The diversion of catalytic mechanisms is mainly ascribed to the different ligand environments, from nonaqua ligands to an aqua ligand. Findings in this work provide some critical proof for our previous hypothesis about how alternation of ancillary ligands of water oxidation catalysts influences their catalytic efficiency.
authors.affiliation: Department of Chemistry and Pharmacy, Friedrich-Alexander University of Erlangen-Nuremberg , Schlossplatz 4, 91054 Erlangen, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Staehle
authors.forename: Lianpeng
authors.initials: L
authors.lastname: Tong
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Lele
authors.initials: L
authors.lastname: Duan
authors.forename: Andreas
authors.initials: A
authors.lastname: Fischer
authors.forename: Mårten S G
authors.initials: MS
authors.lastname: Ahlquist
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
authors.forename: Sven
authors.initials: S
authors.lastname: Rau
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: C516814:1,3-dimethylimidazolium; D002264:Carboxylic Acids; D056831:Coordination Complexes; D007093:Imidazoles; D008024:Ligands; D014867:Water; D015082:2,2'-Dipyridyl; D012428:Ruthenium