Electrocatalytic properties of a novel ruthenium(II) terpyridine-based complex towards CO 2 reduction.

The electrocatalytic properties of Ru complexes are of great technological interest given their potential application in reactions such water splitting and CO 2 reduction. In this work, a novel terpyridine-based Ru(II) complex, [RuCl(trpy)(acpy)], trpy = 2,2':6',2''-terpyridine, acpy - = 2-pyridylacetate was synthesized and its spectroscopic, electrochemical and catalytic properties were explored in detail. In dry acetonitrile, the complex exhibits two reduction peaks at -1.95 V and -2.20 V vs. Fc/Fc + , attributed to consecutive 1 e - reduction. Under CO 2 atmosphere, a catalytic wave is observed ( E onset = 2.1 V vs. Fc/Fc + ), with CO as the main reduction product. Bulk electrolysis reveals a turnover number (TON) of 12 ( k obs = 1.5 s -1 ). In the presence of 1% water, an improvement in the catalytic activity is observed (TON CO = 21 and k obs = 2.0 s -1 ) and, additionally, formate was also detected (TON HCOO = 7). Spectroelectrochemical experiments allowed the identification of a metallocarboxylate (Ru-COO - ) intermediate under anhydrous conditions, while in water, the partial labilization of the acpy - ligand was observed in the course of the catalytic cycle. The experimental data was combined with DFT calculations, allowing the proposal of a catalytic cycle. The results establish important relationships between selectivity, ligand structure and reaction conditions.