Copper(II) complexes of substituted salicylaldimines with benzimidazole nucleus: synthesis, characterization and antimicrobial activity

Abstract

The aim of this study was to synthesize and evaluate the antimicrobial activity of Cu(II) complexes of some substituted salicylaldimines with benzimidazole nucleus. The salicylaldimine ligands were prepared by condensing 2-aminobenzimidazole with salicylaldehyde, o-vanillin and p-vanillin. All the compounds and the Cu(II) complexes were characterized by elemental , electronic, infrared and molar conductivity data. In addition, the structures of the ligands were confirmed with 1H-NMR and 13C-NMR spectral data. Both the ligands and the Cu(II) complexes have been screened for their in vitro antimicrobial activity against Staphylococcus aureus subsp. aureus ATCC® 6538™, Bacillus substillis subsp. spizizenii ATCC® 6633™*, Escherichia coli ATCC® 8739™* and Candida albicans ATCC® 2091™* using agar diffusion and broth dilution techniques. The ligands coordinated to the Cu(II) ion in a 1:2 (M:L) ratio as tridentate monobasic species via the imine-N, the imidazole-N and the phenolic–O to give six-coordinated Cu(II) complexes. The free ligands exhibited varying antimicrobial activity on the tested organisms from low activity to significant potency. Candida albicans was specifically susceptible to the o-vanillin Schiff base ligand. The presence of Cu(II) ion, however, did not have a regular effect on the activity of the compounds.