title: Photoinduced electron transfer in a chromophore-catalyst assembly anchored to TiO2.
abstract: Photoinduced formation, separation, and buildup of multiple redox equivalents are an integral part of cycles for producing solar fuels in dye-sensitized photoelectrosynthesis cells (DSPECs). Excitation wavelength-dependent electron injection, intra-assembly electron transfer, and pH-dependent back electron transfer on TiO(2) were investigated for the molecular assembly [((PO(3)H(2)-CH(2))-bpy)(2)Ru(a)(bpy-NH-CO-trpy)Ru(b)(bpy)(OH(2))](4+) ([TiO(2)-Ru(a)(II)-Ru(b)(II)-OH(2)](4+); ((PO(3)H(2)-CH(2))(2)-bpy = ([2,2'-bipyridine]-4,4'-diylbis(methylene))diphosphonic acid); bpy-ph-NH-CO-trpy = 4-([2,2':6',2″-terpyridin]-4'-yl)-N-((4'-methyl-[2,2'-bipyridin]-4-yl)methyl) benzamide); bpy = 2,2'-bipyridine). This assembly combines a light-harvesting chromophore and a water oxidation catalyst linked by a synthetically flexible saturated bridge designed to enable long-lived charge-separated states. Following excitation of the chromophore, rapid electron injection into TiO(2) and intra-assembly electron transfer occur on the subnanosecond time scale followed by microsecond-millisecond back electron transfer from the semiconductor to the oxidized catalyst, [TiO(2)(e(-))-Ru(a)(II)-Ru(b)(III)-OH(2)](4+)→[TiO(2)-Ru(a)(II)-Ru(b)(II)-OH(2)](4+).
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, CB 3290, Chapel Hill, North Carolina 27599-3290, USA.
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Ashford
authors.forename: Wenjing
authors.initials: W
authors.lastname: Song
authors.forename: Javier J
authors.initials: JJ
authors.lastname: Concepcion
authors.forename: Christopher R K
authors.initials: CR
authors.lastname: Glasson
authors.forename: M Kyle
authors.initials: MK
authors.lastname: Brennaman
authors.forename: Michael R
authors.initials: MR
authors.lastname: Norris
authors.forename: Zhen
authors.initials: Z
authors.lastname: Fang
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Templeton
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meyer
mesh_terms: D002384:Catalysis; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D055668:Photochemical Processes; D021241:Spectrometry, Mass, Electrospray Ionization; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium