title: Structural study on highly oxidized states of a water oxidation complex [RuIII(bpy)2(H2O)]2(mu-O)4+ by ruthenium K-edge X-ray absorption fine structure spectroscopy.
abstract: The oxidation-induced structural change of a water-oxidizing diruthenium complex, [(bpy)(2)(H(2)O)Ru(III)(micro-O)Ru(III)(OH(2))(bpy)(2)](4+) (bpy = 2,2'-bipyridine), was investigated by means of X-ray absorption spectroscopy. Ru K-edge XANES (X-ray absorption near-edge structure) spectra from the acidic solution and solid precipitates obtained by oxidation showed that the absorption edge shifts toward higher energy with a preedge feature slightly more enhanced than those of the lower oxidation states. This indicates that the higher oxidation state has a lower symmetry due to shortening of the Ru-O bonds that originated from the water ligands. The EXAFS (extended X-ray absorption fine structure) spectra were similar to those of the lower oxidation states, whose analysis revealed the existence of short Ru-O double bonds and an almost linear Ru-O-Ru angle (169 +/- 2 degrees ). Ab initio EXAFS simulations for several possible structural models suggest that the dimeric structure is maintained during the water oxidation reaction.
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Okamoto
authors.forename: Jun
authors.initials: J
authors.lastname: Miyawaki
authors.forename: Kensuke
authors.initials: K
authors.lastname: Nagai
authors.forename: Daiju
authors.initials: D
authors.lastname: Matsumura
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nojima
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kondoh
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ohta
mesh_terms: D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D009942:Organometallic Compounds; C107993:diaquabis(2,2'-bipyridine-N,N'')ruthenium(II); D014867:Water; D012428:Ruthenium