Novel Polypyridine Bridging Ligands and Their Ruthenium Complexes for Water Oxidation
Nair, Neelima V. 1985-
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Part I: A novel series of bridging ligands and their RuII photosensitizer-catalyst dyads have been prepared and characterized by NMR and electronic absorption spectroscopy as well as cyclic voltammetry. The presence of asymmetry in the ligands facilitated selective metal coordination, which greatly enhanced the ease of the preparation of the dyads. The photophysical properties of the photosensitizers and the photosensitizer-catalyst dyads were also studied. All the photosensitizers were found to be strong fluorescent emitters while the extremely weak emission of the dyads suggested quenching by either energy or electron transfer. The water oxidation activities of the dyads have been evaluated under both light and CeIV activated conditions. The dyads were found to be active under CeIV activated conditions. Electrochemical studies also suggest that these systems may be used as catalysts for photoelectrochemical water oxidation. Part II: A novel dinuclear RuII water oxidation catalyst has been prepared. Its properties and catalytic activity have been evaluated and compared with an analogous system previously reported by our group. These catalysts are active under both light and CeIV activated conditions. A mononuclear analog of the new dinuclear catalyst has also been prepared and evaluated for its activity in order to examine the role of the RuII centers in the dinuclear catalyst. Incorporation of the second RuII center was found to greatly enhance the catalytic activity with respect to the mononuclear system.