Imidazolium Salt-Derived N-Heterocyclic Carbene Ligands for Silver(I) Complex Formation: Synthesis, Spectroscopic Investigation

New imidazolium salts have been prepared from methyl imidazole via nucleophilic substitution reactions using diverse alkyl and functional halides. These salts were subsequently used as precursor compounds for the preparation of nitrogen-cyclic heterogeneous carbene complexes with silver (Ag–NHC) by reaction with silver oxide in methanol. The synthesized ligands and their corresponding metal complexes were characterized using several spectroscopic techniques, including Fourier transform infrared spectroscopy, UV–visible spectroscopy, proton nuclear magnetic resonance (1H NMR), and nuclear magnetic resonance-13 (¹³C NMR), high-resolution mass spectrometry, and elemental analysis (CHN). The spectral data confirmed the successful formation of bonds and the coordination of silver ions across the carbene carbon atom, as evidenced by the characteristic spectral changes and the disappearance of the C2–H proton signal of imidazolium upon complex formation. The antibacterial activity of the synthesized compounds was evaluated and compared. The results showed that silver(I) compounds with heterocyclic carbene (NHC) possessed remarkably enhanced antibacterial activity compared to their initial imidazolium salts counterparts. This remarkable improvement is attributed to the synergistic effect of silver coherence and stability provided by the heterocyclic carbeny bond framework. These results indicate that Ag–NHC compounds derived from imidazolium salts are a promising candidate for the development of novel antimicrobial agents.