Base-enhanced catalytic water oxidation by a carboxylate-bipyridine Ru(II) complex.

Song, Na; Concepcion, Javier J; Binstead, Robert A; Rudd, Jennifer A; Vannucci, Aaron K; Dares, Christopher J; Coggins, Michael K; Meyer, Thomas J · Proc Natl Acad Sci U S A · 2015

basic_science · Level V

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Abstract

In aqueous solution above pH 2.4 with 4% (vol/vol) CH3CN, the complex [Ru(II)(bda)(isoq)2] (bda is 2,2'-bipyridine-6,6'-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [Ru(II)(CO2-bpy-CO2(-))(isoq)2(NCCH3)], as shown by (1)H and (13)C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO4(3-), the calculated half-time for water oxidation is ∼7 μs. The key to the rate accelerations with added bases is direct involvement of the buffer base in either atom-proton transfer (APT) or concerted electron-proton transfer (EPT) pathways.