Imidazole-based chemosensor for the detection of Ag+ ions: Antimicrobial activity, DFT insight, and molecular docking modeling

With nitrogen atoms in its structure, imidazole can form stable complexes with metal ions, making it a highly suitable ligand for the design of selective chemosensors. In addition, imidazole sensors often exhibit high sensitivity and good selectivity toward target ions. In this paper, an imidazole-based chemosensor was prepared, and its photoluminescence activities were studied. For this aim, 2-methylimidazole was nitrated to produce 2-methyl-4(5)-nitroimidazole; its fluorescence activity was studied among various metal ions. It was found that it can detect Ag + with high selectivity. The LOD was obtained to be about 2.38 × 10 −7 M. Also, according to the obtained results from Job's plot test, the stoichiometric ratio between the ligand and the Ag + ion is 1:1. DFT calculations identified the N3 atom as the preferred binding site for Ag + ions, supported by MEP analysis and optimized geometries. FMO analysis indicated increased reactivity upon Ag + complexation. Furthermore, the synthesized compound demonstrated promising antimicrobial activity against both Gram-negative and Gram-positive bacterial strains, with enhanced efficacy observed against Gram-negative bacteria, particularly Escherichia coli (MIC <1 mg/mL). Cytotoxicity assays revealed minimal toxicity in normal HUVEC cells at concentrations below 256 μg/mL, indicating a favorable safety profile. Molecular docking studies versus E. coli protein revealed a strong binding affinity (−6.05 kcal/mol) of compound 2 , corroborating its antimicrobial potential. Collectively, these findings suggest compound 2 as a promising antimicrobial agent with potential for further development.