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Keywords:

  • electrochemistry;
  • homogeneous catalysis;
  • photochemistry;
  • ruthenium;
  • water chemistry

Abstract

A series of mononuclear ruthenium polypyridyl complexes [Ru(Mebimpy)(pic)3](PF6)2 (2; Mebimpy=2,6-bis(1-methylbenzimidazol-2-yl)pyridine; pic=4-picoline), Ru(bimpy)(pic)3 (3; H2bimpy=2,6-bis(benzimidazol-2-yl)pyridine), trans-[Ru(terpy)(pic)2Cl](PF6) (4; terpy=2,2′;6′,2“-terpyridine), and trans-[Ru(terpy)(pic)2(OH2)](ClO4)2 (5) are synthesized and characterized as analogues of the known Ru complex, [Ru(terpy)(pic)3](PF6)2 (1). The effect of the ligands on electronic and catalytic properties is studied and discussed. The negatively charged ligand, bimpy2−, has a remarkable influence on the electrochemical events due to its strong electron-donating ability. The performance in light- and CeIV-driven (CeIV=Ce(NH4)2(NO3)6) water oxidation is successfully demonstrated. We propose that ligand exchange between pic and H2O occurs to form the real catalyst, a Ru–aqua complex. The synthesis and testing of trans-[Ru(terpy)(pic)2(OH2)](ClO4)2 (5) confirmed our proposal. In addition, complex 5 possesses the best catalytic activity among these five complexes.