Syntheses, characterization and antimicrobial activity of silver(I) complexes containing 2-hydroxymethyl-N-alkylimidazole ligands

Silver(I) complexes [Ag2(L)4](NO3)2 were synthesized by the reaction of AgNO3 with 2-hydroxymethyl-N-alkylimidazoles (L) (alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl) in ethanol at room temperature. The X-ray crystal structures of [Ag2(2-hydroxymethyl-N-ethylimidazole)4](NO3)2 (C2) showed a dimeric [Ag(L)4](NO3)2 and a monomeric [Ag(L)2]NO3 complex (L = 2-hydroxymethyl-N-ethylimidazole) in its unit cell, while [Ag2(2-hydroxymethyl-N-benzylimidazole)4](NO3)2 (C8) showed only a dimeric complex [Ag2(L)4](NO3)2 (L = 2-hydroxymethyl-N-benzylimidazole). Both complexes displayed a slightly distorted linear N–Ag–N arrangement and the presence of Ag–Ag interactions in the dimeric complexes was due to the π stacking of the imidazole moieties. The antimicrobial properties of the Ag(I) complexes were investigated against Escherichia coli, Staphylococcus aureus, Bacillus spizizenii and Candida albicans by the disk diffusion and the broth microdilution methods. The Ag(I) complexes containing 2-hydromethyl-N-alkylimidazole ligands with shorter alkyl chain length were predominantly active against E. coli. The complexes containing ligands with longer alkyl chain length displayed predominant activity against B. spizizenii. The broad spectrum antimicrobial activity displayed by these silver(I) complexes makes them potential alternatives to the commercially available antimicrobial agents.

Silver(I) complexes [Ag2(L)4](NO3)2 were synthesized by the reaction of AgNO3 with 2-hydroxymethyl-N-alkylimidazoles (L) (alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl) in ethanol at room temperature. The X-ray crystal structures of [Ag2(2-hydroxymethyl-N-ethylimidazole)4](NO3)2 (C2) showed a dimeric [Ag(L)4](NO3)2 and a monomeric [Ag(L)2]NO3 complex (L = 2-hydroxymethyl-N-ethylimidazole) in its unit cell, while [Ag2(2-hydroxymethyl-N-benzylimidazole)4](NO3)2 (C8) showed only a dimeric complex [Ag2(L)4](NO3)2 (L = 2-hydroxymethyl-N-benzylimidazole). Both complexes displayed a slightly distorted linear N-Ag-N arrangement and the presence of Ag–Ag interactions in the dimeric complexes was due to the π stacking of the imidazole moieties. The antimicrobial properties of the Ag(I) complexes were investigated against Escherichia coli, Staphylococcus aureus, Bacillus spizizenii and Candida albicans by the disk diffusion and the broth microdilution methods. The Ag(I) complexes containing 2-hydromethyl-N-alkylimidazole ligands with shorter alkyl chain length were predominantly active against E. coli. The complexes containing ligands with longer alkyl chain length displayed predominant activity against B. spizizenii. The broad spectrum antimicrobial activity displayed by these silver(I) complexes makes them potential alternatives to the commercially available antimicrobial agents.Figure optionsDownload as PowerPoint slideHighlights
► We synthesized Ag(I) complexes containing 2-hydroxymethyl-N-alkylimidazoles.
► We obtained X-rays crystal structures for the complexes C2 and C8.
► We observed that the crystal structure of C2 reveals a dimeric and monomeric complex in its unit cell.
► We investigated the antimicrobial activity of the complexes.
► We observed that the antimicrobial activity increases as the length of the alkyl chain increases.