Synthesis, characterization, biological determination and catalytic evaluation of ruthenium(ii) complexes bearing benzimidazole-based NHC ligands in transfer hydrogenation catalysis

A new series of ruthenium(ii) N-heterocyclic carbene complexes has been synthesized via transmetalation. These complexes are easily handled in very good yields via synthesis of silver-NHC complexes and subsequent reaction with [RuCl2(p-cymene)](2) in dichloromethane (DCM) under argon atmosphere. The new ruthenium(ii)-NHC complexes were applied to transfer hydrogenation of ketone derivatives using 2-propanol as a hydrogen source and KOH as a co-catalyst. The results show that the corresponding alcohols could be obtained in good yield with high catalyst activity (up to 76%) under mild conditions. All new compounds were characterized by spectroscopic and analytical methods. The antibacterial activities of the corresponding ruthenium(ii)-NHC complexes 4a-i were tested against positive and negative bacteria using the agar dilution procedure and their IC50 values have been determined. A cytotoxicity study of the ruthenium(ii)-NHC complexes 4 was performed against the two human cancer cell lines MDA-MB-231 and MCF-7. In addition, the scavenging activity of the synthesized complexes for the DPPH radical was also determined.