Excited-State Deactivation of Ruthenium(II) Polypyridyl Chromophores Bound to Nanocrystalline TiO₂ Mesoporous Thin Films

Abstract

Excitation of Ru(deeb)(bpy)2 2+, bis(2,2‘-bipyridine)(2,2‘-bipyridine-4,4‘-diethylester)ruthenium(II) hexafluorophosphate, bound to nanocrystalline TiO2 thin films and immersed in an acetonitrile bath at 25 °C under an argon atmosphere, results in the formation of a species, the transient spectral characteristics for which are, consistent with a metal-to-ligand charge transfer, MLCT, excited state. The spectrum decays by kinetics that are inconsistent with a simple first-order process. Modeling of the data as a function of irradiance has been accomplished assuming parallel unimolecular and bimolecular excited-state deactivation processes. The quantum yield for excited-state formation depends on the excitation irradiance, consistent with triplet−triplet annihilation processes that occur with k ≥ 1 × 108 s-1.

Photophysics of a Ruthenium 4H‐Imidazole Panchromatic Dye in Interaction with Titanium Dioxide

“…This process can lead to rapid decay of excited-state absorption signals and provides a deactivation path that is absent when the dyes are studied in solution. [46] However, the annihilation process should also lead to simultaneous decay of GSB and ESA, and hence the occurrence of such a process can be excluded for Ru1-sensitized TiO 2 . Thus, the sub-2 ps decay of the ESA signal is attributed to electron injection from the photoexcited dye into the conduction band of the semiconductor nanoparticles.…”

Solar Photochemistry with Transition Metal Compounds Anchored to Semiconductor Surfaces

“…In many important aspects, the room-temperature photophysical properties of Ru(dcb)(bpy) 2 anchored to TiO 2 are remarkably similar to those observed in fluid solution particularly when one takes into account the protonation state of the carboxylic acid groups. 51 The most significant difference was that excited-state relaxation on TiO 2 (and ZrO 2 ) occurred by a parallel first-and second-order kinetic model where excited-state relaxation in solution is first order. The second-order component was attributed to triplet-triplet annihilation reactions that occur in parallel with radiative and nonradiative decay.…”

Ruthenium and rhodium complexes anchored to europium oxide nanoparticles

“…Inorganic metal complexes can be attached on the surface of lanthanide oxides in a similar manner to the metal oxides commonly used in dye-sensitized solar cells. These materials can be used to study interesting properties for potential use in light-to-energy conversion or sensing, where metal oxide-metal complex interactions are prevalent.Covalent attachment of transition metal polypyridyl complexes onto metal oxides has been demonstrated for ligands with carboxylic acid [6,23-27], carboxylate ester [5,9,[26][27][28][29][30], and phosphonate-based [24,31] groups of the metal complex ligands. In our work we use the deeb ligand because metal-deeb complexes can be prepared easily and they have strong surface adsorption to the metal-oxide…”

“…Covalent attachment of transition metal polypyridyl complexes onto metal oxides has been demonstrated for ligands with carboxylic acid [6,[23][24][25][26][27], carboxylate ester [5,9,[26][27][28][29][30], and phosphonate-based [24,31] groups of the metal complex ligands. In our work we use the deeb ligand because metal-deeb complexes can be prepared easily and they have strong surface adsorption to the metal-oxide surface [30].…”

“…In our work we use the deeb ligand because metal-deeb complexes can be prepared easily and they have strong surface adsorption to the metal-oxide surface [30]. Although the bulk of oxides that have been used with this ligand are semiconductor oxides such as TiO 2 , lanthanide oxides contain surface hydroxyl groups suitable for attaching the deeb ligand via hydrolysis of the ester moieties [5,30].…”