Effects of Br substituent on catalytic performance of Ru-bda (H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) catalysts for water oxidation

A series of new Ru-bda catalysts with Br modification on the equatorial ligand, [Ru(Ln)(picoline)2] (H2L1 = 4-Br-2,2'-bipyridine-6,6'-dicarboxylic acid (4-Br-bda), 2; H2L2 = 4,4'-diBr-bda, 3) and [Ru(L1)(isoquinoline)2] 5, were synthesized for catalytic water oxidation. Compared with the un-substituted catalysts, the catalysts modified with Br displayed a marked change in the catalytic activities and reaction orders. The results confirm that the electronic effect of Br has a large effect on the kinetics and leads to the change in reaction orders.

Graphical AbstractCompared with un-substituted catalysts, the Ru-bda water oxidation catalysts containing Br in the equatorial ligand display lower catalytic activities. The relative kinetic studies reveal the change in catalytic mechanism. All of these changes were caused by the electron withdrawing effect of Br.Figure optionsDownload as PowerPoint slide