Novel N-Heterocyclic Carbene Silver(I) Complexes: Synthesis, Structural Characterization, Antimicrobial and Cytotoxicity Potential Studies

In this study, a series of unsymmetrical N,N-disubstituted benzimidazolium salts were synthesized as N-heterocyclic carbene (NHC) (2a-2j) and their Ag-I complexes. Their structures were characterized by elemental analyses, H-1 and C-13 nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy techniques. Further, both the salts and their silver(I)-NHC complexes have been evaluated for their potential antibacterial properties against a panel of bacterial strains namely, Micrococcus luteus, Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus and Pseudomonas aeruginosa. The results show that silver complexes are effective against Salmonella Typhimurium, Listeria monocytogenes, and Micrococcus luteus with moderate to high activity, and their minimum inhibitory concentrations ranging from 0.0034 to 1.26 mg mL(-1). In addition, the benzimidazoles salts 2a-2j and silver-NHC complexes 3a-3j were screened for their antitumor activity. Complex 3e exhibited the highest antitumor effect with half-maximal inhibitory concentration (IC50) value of 4.2 mu g mL(-1) against MCF-7.