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

Abstract

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.