ABSTRACT

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.
 

KEYWORDS

Antibacterial; Carbene ; Heterocyclic; Organometallic

REFERENCES

1) Gopalakrishnan, A.K., S.A. Angamaly, and M.P. Velayudhan, An Insight into the biological Congiu, C., M.T. Cocco, and V. Onnis, Design, synthesis, and in vitro antitumor activity of new 1, 4-diarylimidazole-2-ones and their 2-thione analogues. Bioorganic & medicinal chemistry letters, 2008. 18(3): p. 989-993.
2) Babizhayev, M.A., Biological activities of the natural imidazole-containing peptidomimetics n-acetylcarnosine, carcinine and L-carnosine in ophthalmic and skin care products. Life sciences, 2006. 78(20): p. 2343-2357.
3) Nakamura, T., et al., Imidazole derivatives as new potent and selective 20-HETE synthase inhibitors. Bioorganic & Medicinal Chemistry Letters, 2004. 14(2): p. 333-336.
4) Nantermet, P.G., et al., Imidazole acetic acid TAFIa inhibitors: SAR studies centered around the basic P1′ group. Bioorganic & medicinal chemistry letters, 2004. 14(9): p. 2141-2145.
5) Venkatesan, A.M., et al., 5, 5, 6-Fused tricycles bearing imidazole and pyrazole 6-methylidene penems as broad-spectrum inhibitors of β-lactamases. Bioorganic & medicinal chemistry, 2008. 16(4): p. 1890-1902.
6) Amouri, H., Luminescent Complexes of Platinum, Iridium, and Coinage Metals Containing N-Heterocyclic Carbene Ligands: Design, Structural Diversity, and Photophysical Properties. Chemical Reviews, 2022.
7) Gopalan, B., et al., Metal-free imidazolium salts inhibit the growth of hepatocellular carcinoma in a mouse model. Laboratory investigation, 2011. 91(5): p. 744-751.
8) Herrmann, W.A., et al., Heterocyclic carbenes: A high‐yielding synthesis of novel, functionalized N‐heterocyclic carbenes in liquid ammonia. Chemistry–A European Journal, 1996. 2(12): p. 1627-1636.
9) Kühl, O. and G. Palm, Imidazolium salts from amino acids—a new route to chiral zwitterionic carbene precursors? Tetrahedron: Asymmetry, 2010. 21(4): p. 393-397.
10) Shalini, K., P.K. Sharma, and N. Kumar, Imidazole and its biological activities: A review. Der Chemical Sonica, 2010. 1(3): p. 36-47.
11) Bowlas, C.J., D.W. Bruce, and K.R. Seddon, Liquid-crystalline ionic liquids. Chemical communications, 1996(14): p. 1625-1626.

Cite this article

Marhoon, H. M. (2026). Imidazolium Salt-Derived N-Heterocyclic Carbene Ligands for Silver(I) Complex Formation: Synthesis, Spectroscopic Investigation. INTERNATIONAL JOURNAL OF HEALTH & MEDICAL RESEARCH, 5(4), 299-309. https://doi.org/10.58806/ijhmr.2026.v5i4n03