title: Electronic structure of oxidized complexes derived from cis-[Ru(II)(bpy)2(H2O)2]2+ and its photoisomerization mechanism.
abstract: The geometry and electronic structure of cis-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) and its higher oxidation state species up formally to Ru(VI) have been studied by means of UV-vis, EPR, XAS, and DFT and CASSCF/CASPT2 calculations. DFT calculations of the molecular structures of these species show that, as the oxidation state increases, the Ru-O bond distance decreases, indicating increased degrees of Ru-O multiple bonding. In addition, the O-Ru-O valence bond angle increases as the oxidation state increases. EPR spectroscopy and quantum chemical calculations indicate that low-spin configurations are favored for all oxidation states. Thus, cis-[Ru(IV)(bpy)(2)(OH)(2)](2+) (d(4)) has a singlet ground state and is EPR-silent at low temperatures, while cis-[Ru(V)(bpy)(2)(O)(OH)](2+) (d(3)) has a doublet ground state. XAS spectroscopy of higher oxidation state species and DFT calculations further illuminate the electronic structures of these complexes, particularly with respect to the covalent character of the O-Ru-O fragment. In addition, the photochemical isomerization of cis-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) to its trans-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) isomer has been fully characterized through quantum chemical calculations. The excited-state process is predicted to involve decoordination of one aqua ligand, which leads to a coordinatively unsaturated complex that undergoes structural rearrangement followed by recoordination of water to yield the trans isomer.
authors: Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, E-43007 Tarragona, Spain.
authors: Nora
authors: N
authors: Planas
authors: Laura
authors: L
authors: Vigara
authors: Clyde
authors: C
authors: Cady
authors: Pere
authors: P
authors: Miró
authors: Ping
authors: P
authors: Huang
authors: Leif
authors: L
authors: Hammarström
authors: Stenbjörn
authors: S
authors: Styring
authors: Nils
authors: N
authors: Leidel
authors: Holger
authors: H
authors: Dau
authors: Michael
authors: M
authors: Haumann
authors: Laura
authors: L
authors: Gagliardi
authors: Christopher J
authors: CJ
authors: Cramer
authors: Antoni
authors: A
authors: Llobet
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D056831:Coordination Complexes / Q000032:analysis / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D007536:Isomerism; D008024:Ligands; D008027:Light; D008958:Models, Molecular; D010084:Oxidation-Reduction; D055668:Photochemical Processes / Q000528:radiation effects; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D014867:Water; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D006861:Hydrogen Peroxide