title: Artificial model of photosynthetic oxygen evolving complex: catalytic O2 production from water by di-mu-oxo manganese dimers supported by clay compounds.
abstract: Adsorption of [(OH(2))(terpy)Mn(mu-O)(2)Mn(terpy)(OH(2))](3+) (terpy=2,2':6',2"-terpyridine) (1) onto montmorillonite K10 (MK10) yielded catalytic dioxygen (O(2)) evolution from water using a Ce(IV) oxidant. The Mn K-edge X-ray absorption near edge structure (XANES) of the 1/MK10 hybrid suggested that the oxidation state of the di-mu-oxo Mn(2) core could be Mn(III)-Mn(IV). However the pre-edge peak in the XANES spectrum of 1 adsorbed on MK10 is different from the neat 1 powder. The kinetic analysis of O(2) evolution showed that the catalysis requires cooperation of two equivalents of 1 adsorbed on MK10. The reaction of the [(bpy)(2)Mn(mu-O)(2)Mn(bpy)(2)](3+) (bpy=2,2'-bipyridine) (2)/MK10 hybrid with a Ce(IV) oxidant evolved O(2). However, the turnover number value was less than unity for 2/MK10, showing that 2 adsorbed on MK10 does not work as a catalyst. The terminal water ligands could be an important for the catalysis by adsorbed 1. The mechanism of O(2) production by photosynthetic oxygen evolving complex is discussed based on catalytic O(2) evolution by 1 adsorbed on MK10.
authors.affiliation: Faculty of Education and Human Sciences, Niigata University, 8050 Ikarashi-2, Niigata 950-2181, Japan. yagi@ed.niigata-u.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yagi
authors.forename: Komei
authors.initials: K
authors.lastname: Narita
authors.forename: Syou
authors.initials: S
authors.lastname: Maruyama
authors.forename: Koji
authors.initials: K
authors.lastname: Sone
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kuwabara
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000493:pharmacokinetics*; D002384:Catalysis; D000077215:Clay; D019281:Dimerization; D007700:Kinetics; D008345:Manganese / Q000737:chemistry*; D008954:Models, Biological; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex; D014867:Water / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D009942:Organometallic Compounds; D045332:Photosystem II Protein Complex; D014867:Water; D001546:Bentonite; D008345:Manganese; D010100:Oxygen; D000077215:Clay