Tailored design of ruthenium molecular catalysts with 2,2′-bypyridine-6,6′-dicarboxylate and pyrazole based ligands for water oxidation

Abstract

With the incorporation of pyrazole and DMSO as axial ligands, a series of tailor-designed Ru water oxidation catalysts [Ru(bda)(DMSO)(L)] (H₂bda = 2,2′-bypyridine-6,6′-dicarboxylic acid; DMSO = dimethyl sulfoxide; L = pyrazole, A-1; 4-Br-3-methyl pyrazole, B-1) and [Ru(bda)(L)₂] (L = pyrazole, A-2; 4-Br-3-methyl pyrazole, B-2) have been generated in situ from their corresponding precursors [Ru(κ₃^O,N,N-bda)(DMSO)_x(L)_3−x] which are in a zwitterionic form with an extra pyrazole based ligand in the equatorial position. Formation of the active catalyst has been investigated under pH 1.0 conditions. Electrochemistry and water oxidation activity of these catalysts were investigated. By fine tuning of the catalyst structure, the turnover frequency was increased up to 500 s⁻¹ and the stability over 6000 turnovers.