Affecting the Catalytic Activity of the Known [Ru(tpy)(bpy)(OH2)](2+) Complex in Water Oxidation by Utilization of a Hangman Ligand

摘要

[Ru(tpy)(bpy)(OH2)](2+) (bpy = 2,2-bipyridine, tpy = 2,2;6,2-terpyridine) is the archetype of many known single-site ruthenium complexes used for catalytic water oxidation. Its efficiency is likely influenced by installing a proton-donor/acceptor functionality in proximity to the catalytic site because the reaction mechanism is believed to occur by nucleophilic attack of a water molecule on a high-valent metal-oxo species assisted by hydrogen-bonding interactions. We present herein the results of a study of a new metal complex based on the hangman motif that possesses a carboxylic functional group close to the ruhenium center. This catalyst was synthesized in very good yield and fully characterized. We discovered that its catalytic activity was in fact hampered by the presence of the functional group. Further investigations revealed a strong dependence of the catalytic performance not only on the solvent, but also on the counter ion and other additives used.