R. J. Watts

Bio: R. J. Watts is an academic researcher. The author has contributed to research in topics: Iridium & Ruthenium. The author has an hindex of 4, co-authored 5 publications receiving 998 citations.

Temperature dependence of the photophysical and photochemical properties of the tris(2,2'-bipyridyl)ruthenium(II) ion in aqueous solution

Abstract: Luminescence lifetimes and quantum yields of Ru(bipy)32+ in aqueous solution between 0 and 100 "C are reported. The study includes both the perprotio and perdeuterio complex in H 2 0 and D20. Although the luminescence lifetimes and quantum yields are found to be solvent and temperature dependent, the radiative lifetime is insensitive to these parameters. The temperature dependence of the lifetime and quantum yield data is correlated with a model which assumes a lower set of luminescent levels which undergo weak-coupled radiationless deactivation and a higher set of nonluminescent levels which undergo strong-coupled radiationless deactivation. Although the complex ion is essentially photoinert at 25 "C in 0.1 M HC1, photolysis at 95 OC with 436-nm irradiation results in labilization of 2,2'-bipyridine. Photophysical and photochemical data suggest that the lower set of levels in our model are charge-transfer-to-ligand states, which are modified by mixing with charge-transfer-to-solvent configurations. These levels are photoinert, whereas the upper set of levels, which are -3600 cm-I above the lower set, give rise to ligand substitution photochemistry. The upper set of levels is assigned to d-d orbital parentage.

Chemical approaches to artificial photosynthesis

Abstract: The goal of artificial photosynthesis is to use the energy of the sun to make high-energy chemicals for energy production. One approach, described here, is to use light absorption and excited-state electron transfer to create oxidative and reductive equivalents for driving relevant fuel-forming half-reactions such as the oxidation of water to O2 and its reduction to H2. In this “integrated modular assembly” approach, separate components for light absorption, energy transfer, and long-range electron transfer by use of free-energy gradients are integrated with oxidative and reductive catalysts into single molecular assemblies or on separate electrodes in photelectrochemical cells. Derivatized porphyrins and metalloporphyrins and metal polypyridyl complexes have been most commonly used in these assemblies, with the latter the focus of the current account. The underlying physical principleslight absorption, energy transfer, radiative and nonradiative excited-state decay, electron transfer, proton-coupled elec...

Photodriven heterogeneous charge transfer with transition-metal compounds anchored to TiO2 semiconductor surfaces

Abstract: A critical review of light-driven interfacial charge-transfer reactions of transition-metal compounds anchored to mesoporous, nanocrystalline TiO2 (anatase) thin films is described. The review highlights molecular insights into metal-to-ligand charge transfer (MLCT) excited states, mechanisms of interfacial charge separation, inter- and intra-molecular electron transfer, and interfacial charge-recombination processes that have been garnered through various spectroscopic and electrochemical techniques. The relevance of these processes to optimization of solar-energy-conversion efficiencies is discussed (483 references).