It is an ever-growing concern to find renewable sources of energy as we try to slow down global warming. Research for renewable sources continues to grow and a popular focus is water oxidation based on the natural process of photosynthesis. Two ruthenium polypyridyl water oxidation catalysts were synthesized in a three-step procedure. The first catalyst, [Ru(tpy)(bpy)(H2O)][OTf]2 (tpy = 2,2':6',2''-terpyridine, bpy = 2,2'-bipyridine) is a known catalyst that we used to develop a methodology and use as a control for water oxidation studies. The second catalyst, [Ru(tpyOH)(bpy)(H2O)][OTf]2 (tpyOH = 4'-hydroxy-2,2':6',2''-terpyridine) contains a deprotonatable ligand, tpyOH, that influences the electronics of the complex. For synthesis, RuCl3●3H2O was reacted with 2,6-bis(2-pyridyl)-4(1H)-pyridone in ethanol at reflux to obtain Ru(tpyOH)Cl3. One equivalent of bipyridine, 10 equivalents of LiCl, and N-ethylmorpholine were added and refluxed in 5:1 methanol and water to form [Ru(tpyOH)(bpy)Cl][Cl] and purified by column chromatography. Two equivalents of AgOTf was added to a solution of 6:1 acentone:water to obtain the desired catalyst, [Ru(tpyOH)(bpy)(H2O)][OTf]2. The tpyOH complexes were characterized by infrared spectroscopy, 1H NMR spectroscopy and UV-visible spectroscopy. In addition single crystal x-ray diffraction and cyclic voltammetry were obtained for the catalyst. Cyclic voltammograms were taken at various pH values to form a Pourbaix diagram. Catalytic oxygen evolution was measured using ammonium cerium(IV) nitrate as the oxidant.

Synthesis and characterization of [Ru(tpyOH)(bpy)(H2O)][OTf]2(tpyOH = 4'-hydroxy-2,2':6',2''-terpyridine, bpy = 2,2'-bipyridine) for water oxidation catalysis

2019 Spring National Meeting

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