Investigation of C1 reduction via hydride transfer by Ru polypyridyl complexes (2015)

Undergraduate: Ian Mercer

Faculty Advisor: Cynthia Schauer
Department: Chemistry

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Crucial to optimizing the solar generation of fuels is a mechanistic understanding of catalytic reduction of simple, one-carbon (C1) molecules by ruthenium polypyridyl complexes, commonly employed catalysts for photoelectrochemical cells. A previous study was conducted on the hydride transfer ability of Ru(terpy)(bpy)H+ (terpy = 2,2¿¿¿,6¿¿¿,2¿¿¿¿¿¿-terpyridine; bpy = 2,2¿¿¿-bipyridine) to C1 species CO2, CO, and CH2O using water as a solvent. Results of this investigation warrant attention because, for one, the use of water as a solvent yields a four orders of magnitude increase in hydride transfer rate constant compared to acetonitrile. Secondly, the metal-coordinated products of hydride transfer are oxygen-bonded, an unexpected outcome when considering the nucleophilicity of the hydride. For my thesis, I wish to reproduce the experiments from the previously mentioned research to confirm its results. Then, I will study the kinetics and synthetic products of these C1 reductions with analogous complexes namely Ru(bpy¿¿¿)2(CO)H+ (bpy¿¿¿ = 5,5¿¿¿:2,2¿¿¿-dimethylbipyridine) of which I have already isolated and characterized by 1H NMR. Additionally, I will be preforming DFT calculations to compare the free energies of the O-bonded and C-bonded hydride adduct isomers. Through this research I hope to gain a better understanding of the pathway by which this class of hydride transfers occurs as well as the factors affecting the reactivity of metal hydride complexes.