Synthesis, Structural Characterization and Biological Activity of Silver(I) Complexes with 1-Phenylimidazole

Silver(I) complexes have attracted considerable attention in coordination and medicinal chemistry due to their pronounced antibacterial and antifungal properties. In this study, two silver(I) complexes with 1-phenylimidazole (phim), [Ag(phim)₂]SbF₆ (Ag1) and [Ag(phim)₂]BF₄ (Ag2), were synthesized by reacting the corresponding AgX salts (X = SbF₆^– and BF₄^–) with the phim ligand in a 1 : 1 molar ratio in ethanol at room temperature in the absence of light. The synthesized silver(I) complexes were characterized by elemental analysis, molar conductivity measurement, ¹H NMR, IR, and UV-Vis spectroscopy, and cyclic voltammetry, while their crystal structures were determined by single crystal X-ray diffraction. In both complexes, two phim ligands are coordinated to the Ag(I) center in a monodentate fashion through the N3 atom of the imidazole ring, forming the cationic [Ag(phim)₂]⁺ species, which is charge-balanced by the corresponding counter-anion. The antimicrobial activity of complexes Ag1 and Ag2 was evaluated against a panel of bacterial and fungal strains, while their cytotoxicity was assessed using the normal human lung fibroblast cell line (MRC-5). In vitro biological assays demonstrated that both silver(I) complexes exhibit good to moderate antibacterial and antifungal activities. Notably, coordination of 1-phenylimidazole to Ag(I) enhanced its antimicrobial activity compared with the free ligand. These findings highlight the potential of silver(I) complexes containing N-heterocyclic ligands as promising candidates for the development of novel antimicrobial agents.