Biological Activities and Chelating Properties of New Benzoyl Derivatives of 2-Substituted Benzimidazoles

Background and Objective: Increasing prevalence of bacterial infections as well as the resistance of some existing drugs necessitates the need for further research for compounds with more effective activities. Thus, this study synthesized benzoyl derivatives of 2-2-substituted benzimidazoles, evaluated their chelating properties and investigated the biological activities of the derivatives and their metal complexes. Materials and Methods: The derivatives (L1, L2) and their metal (II) complexes were synthesized and characterized using UV-Vis, IR and NMR spectroscopies, metal analysis and magnetic susceptibility and conductance measurements and screened for antibacterial activity against six bacterial isolates: Bacillus cereus NCIB 6349, Bacillus subtilis NCIB 3610, Bacillus stearothermophilus NCIB 8222. Serratia marcescens NCIB 1377, Klebsiella pneumoniae NCIB 418, Escherichia coli (E. coli) NCIB 86. Results: As ¹HNMR, ¹³C-NMR and IR spectra confirmed the expected structures of the ligands. Spectral analyses of the ligands and the metal complexes showed the coordination of the ligands to the metal ions via the nitrogen and oxygen atoms in the benzoyl derivatives resulting in octahedral and tetrahedral geometries for L1 and L2, respectively. Some of the metal (II) complexes showed greater inhibitory effects against E. coli and Bacillus stearothermophilusthan the reference streptomycin and ampicillin at 50 mg mL^-1. Conclusion: The study established L1 as a bidentate and L2 as a monodentate ligand. The metal complexes especially of L1 showed higher antibacterial activities against the tested micro-organisms than their corresponding ligands.