An Insulating AlO Overlayer Prevents Lateral Hole Hopping Across Dye-Sensitized TiO Surfaces.

Three chromophores of the general form [Ru(bpy')(4,4'-(POH)-2,2'-bipyridine)], where bpy' is 4,4'-(C(CH))-2,2'-bipyridine (Ru(dtb)P); 4,4'-(CHO)-2,2'-bipyridine (Ru(OMe)P), and 2,2'-bipyridine (RuP) were anchored to mesoporous thin films of TiO nanocrystallites at saturation surface coverages to investigate lateral self-exchange Ru intermolecular hole hopping in 0.1 M LiClO/CHCN electrolytes. Hole hopping was initiated by a potential step 500 mV positive of the (Ru) potential or by pulsed laser (532 nm, 8 ns fwhm) excitation and monitored by visible absorption chronoabsorptometry and time-resolved absorption anisotropy measurements, respectively.

Optimization of Photocatalyst Excited- and Ground-State Reduction Potentials for Dye-Sensitized HBr Splitting.

Dye-sensitized bromide oxidation was investigated using a series of four ruthenium polypyridyl photocatalysts anchored to SnO/TiO core/shell mesoporous thin films through 2,2'-bipyridine-4,4'-diphosphonic acid anchoring groups. The ground- and excited-state reduction potentials were tuned over 500 mV by the introduction of electron withdrawing groups in the 4 and 4' positions of the ancillary bipyridine ligands. Upon light excitation of the surface-bound photocatalysts, excited-state electron injection yielded an oxidized photocatalyst that was regenerated through bromide oxidation.

Excited-State Decay Pathways of Tris(bidentate) Cyclometalated Ruthenium(II) Compounds.

The synthesis, electrochemistry, and photophysical characterization are reported for 11 tris(bidentate) cyclometalated ruthenium(II) compounds, [Ru(N^N)(C^N)]. The electrochemical and photophysical properties were varied by the addition of substituents on the 2,2'-bipyridine, N^N, and 2-phenylpyridine, C^N, ligands with different electron-donating and -withdrawing groups. The systematic tuning of these properties offered a tremendous opportunity to investigate the origin of the rapid excited-state decay for these cyclometalated compounds and to probe the accessibility of the dissociative, ligand-field (LF) states from the metal-to-ligand charge-transfer (MLCT) excited state.