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

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-04, Vol.52 (14), p.4442-4455
• Main Authors: Faustino, Leandro A, Machado, Antonio E H, Maia, Pedro I S, Concepcion, Javier J, Patrocinio, Antonio Otavio T
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/D3DT00121K

The electrocatalytic properties of Ru complexes are of great technological interest given their potential application in reactions such water splitting and CO 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 Fc/Fc , attributed to consecutive 1 e reduction. Under CO atmosphere, a catalytic wave is observed ( = 2.1 V Fc/Fc ), with CO as the main reduction product. Bulk electrolysis reveals a turnover number (TON) of 12 ( = 1.5 s ). In the presence of 1% water, an improvement in the catalytic activity is observed (TON = 21 and = 2.0 s ) and, additionally, formate was also detected (TON = 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.