title: Theoretical study of water oxidation by the ruthenium blue dimer. II. Proton relay chain mechanism for the step [bpy2(HOO)Ru(IV)ORu(IV)(OH)bpy2]4+ → [bpy2(O2(–))Ru(IV)ORu(III)(OH2)bpy2]4+.
abstract: The oxidation of water to O2 by the oxidized species [L2(O)Ru(V)ORu(V)(O)L2]4+ of the Ru blue dimer catalyst (L = bpy, bipyridine) is examined using density functional theory with model ligands and explicit solvent approaches. Following our earlier study of the initial O–O formation by addition of water (step I) ( J. Phys. Chem. A 2011, 115, 8003), we report calculations on the subsequent, penultimate step in the superoxide production (denoted step II), involving proton transfer from the reactant [L2(HOO)Ru(IV)ORu(IV)(OH)L2]4+ to form [L(O2(–))Ru(IV)ORu(III)(H2O)L2]4+. The reaction profile of step II commences with a rearrangement of the HOO and OH groups and associated solvent relaxation in the complex, accompanied by a barrier of ~9 kcal/mol and a free-energy change of +3 kcal/mol. Subsequently, a water molecule connecting these two groups mediates a double proton transfer in a proton relay chain that proceeds spontaneously with a free-energy decrease of 8 kcal/mol to form step II’s product. Comparison with other calculations is made, and the implications for the overall water oxidation to O2 are discussed.
authors: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
authors: Roberto
authors: R
authors: Bianco
authors: P Jeffrey
authors: PJ
authors: Hay
authors: James T
authors: JT
authors: Hynes
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D011522:Protons; D012428:Ruthenium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D011522:Protons; D012997:Solvents; D014867:Water; D013481:Superoxides; D012428:Ruthenium