Light-Driven Water Splitting by a Covalently Linked Ruthenium-Based Chromophore-Catalyst Assembly

The preparation and characterization of new Ru(II) polypyridyl-based chromophore-catalyst assemblies, [(4,4'-PO3H2-bpy)(2)Ru(4-Mebpy-4' -epic)Ru(bda)(pic)](2+) (1, bpy = 2,2'-bipyridine; 4-Mebpy-4'-epic = 4-(4-methylbipyr-idin-4'-yl-ethyl)-pyridine; bda = 2,2'-bipyridine-6,6' -dicarboxylate; pic = 4-pico-line), and [(bpy)(2)Ru(4-Mebpy-4' -epic)Ru(bda)(pic)(2+) (I') are described, as is the application of I in a dye-sensitized photoelectrosynthesis cell (DSPEC) for solar water splitting. On SnO2/TiO2 core-shell electrodes in a DSPEC configuration with a Pt cathode, the chromophore-catalyst assembly undergoes light-driven water oxidation at pH 5.7 in a 0.1 M acetate buffer, 0.5 M in NaClO4. With illumination by a 100 mW cm(-2) white light source, photocurrents of similar to 0.85 mA cm(-2) were observed after 30 s under a 0.1 V vs Ag/AgCl applied bias with a faradaic efficiency for O-2 production of 74% measured over a 5 min illumination period.