Research Article

Novel Silver(I) Bis-Benzimidazole Complexes: Design, Synthesis, and In Vitro Antibacterial Evaluation

Abstract

A series of novel (Ag(I)–NHC) complexes, Cn1–Cn4, was synthesized from bisbenzimidazolium ligands Ln1–Ln4 bearing benzyl, propargyl, cyanomethyl, and tert-butyl ester substituents, and then assessed for antibacterial activity. The ligands were prepared through N-alkylation of the corresponding bis-benzimidazole precursor in refluxing 1,4-dioxane. Treatment with Ag2O in acetonitrile at room temperature produced the Ag(I)–NHC complexes. FTIR and 1H, 13C NMR spectroscopy confirmed ligand formation and coordination to Ag(I); notably, the benzimidazolium C2–H resonance disappeared, while Ag–C(NHC) signals appeared at δ 182.35 184.45 ppm. Antibacterial activity was tested against four types of selected microorganism, using the (MIC) assay. Each complex showed measurable activity. Cn4 was the most potent overall, with MIC values of 6.25, 3.12, 6.25, and 12.5 μmol/L against the four strains, respectively. Antibacterial activity ranked Cn4 > Cn1 ≈ Cn3 > Cn2, pointing to a clear effect of the N-substituent on biological performance. Against the tested Gram-positive strains, Cn4 was more active than amoxicillin; amoxicillin, however, showed greater activity against both Gram-negative strains. These results point to bis-benzimidazole-derived Ag(I)–NHC complexes especially Cn4 as promising antibacterial candidates, while also showing how substituent modification can tune their biological activity.

Author Affiliation:

Ghanem Shaker Aljebouri: Department of Chemistry, College of Science, University of Baghdad, Baghdad, 10071, Iraq.

How To Cite: G.S. Aljebouri. Novel Silver(I) Bis-Benzimidazole Complexes: Design, Synthesis, and In Vitro Antibacterial Evaluation. Interdisciplinary Studies on Applied Science, 3(2):1–6, 2026. https://doi.org/10.58613/isas321