New dicarboxylic acid bipyridine ligand for ruthenium polypyridyl sensitization of TiO2.

摘要: An ambidentate dicarboxylic acid bipyridine ligand, (4,5-diazafluoren-9-ylidene) malonic (dfm), was synthesized for coordination to Ru(II) and mesoporous nanocrystalline (anatase) TiO2 thin films. The dim ligand provides a conjugated pathway from the pyridyl rings carbonyl carbons of carboxylic groups. X-ray crystal structures [Ru(bpy)(2)(dfm)]Cl-2 corresponding diethyl ester compound, [Ru(bpy)(2)(defm)](PF6)(2), were obtained. compounds displayed intense metal-to-ligand charge transfer (MLCT) absorption bands in visible region (epsilon > 11,000 M-1 cm(-1) [Ru(bpy)(2)(dfm)](PF6)(2) acetonitrile). Significant room temperature photo-luminescence, PL, absent CH3CN but observed at 77 K 4:1 EtOH:MeOH (v:v) glass. Cyclic voltammetry measurements revealed quasi-reversible Ru-III/(II) electrochemistry. Ligand reductions compound [Ru(bpy)(2)(defm)](2+), irreversible [Ru(bpy)(2)(dfm)](2+). Both anchored films by overnight reactions yield saturation surface coverages 3 X 10(-8) mol/cm(2). Attenuated total reflection infrared that [Ru(bpy)(2)(dfm)](2+) present deprotonated carboxylate form when surface. MLCT excited states both injected electrons into with quantum yields 0.70 0.1 M LiClO4 CH3CN. Micro- milli- second recombination yielded ground state products. In regenerative solar cells 0.5 LiI/0.05 I-2 CH3CN, Ru(bpy)(2)(dfm)/TiO2 incident photon-to-current efficiencies 0.7 maximum. Under same conditions, diethylester found rapidly desorb