Metal complexes of benzimidazole derived sulfonamide: Synthesis, molecular structures and antimicrobial activity

Abstract

Benzimidazole and sulfonamide moieties are found in a number of pharmaceutically active molecules. By incorporating the sulfonamide pharmacophore into the benzimidazole scaffold, we prepared 2-(o-sulfamoylphenyl)benzimidazole 1 from saccharin as a precursor. Ligand 1 was coordinated to the divalent transition metals Mn(II) 2, Co(II) 3, Ni(II) 4, Cu(II) 5 and Zn(II) 6 to yield complexes of the general formula [ML2(H2O)n] (n=2 for 2 and n=0 for 3–6). All the compounds were characterized by elemental analysis, conductivity measurements, magnetic susceptibility, FT-IR and NMR spectroscopy. The molecular structures of 1, 3 and 6 were determined by X-ray diffraction analysis. In all metal complexes, 1 behaved as a bidentate chelating ligand through the sulfonamidate nitrogen and the endocyclic nitrogen of benzimidazole. The molecular structures of 3 and 6 showed tetrahedral geometry around the Co(II) and Zn(II) centers, respectively. The molar conductivity data revealed the metal complexes to be non-electrolytes. The benzenesulfonamide derivative and its metal complexes were evaluated for their potential antimicrobial activity against a range of bacterial and fungal strains. [Co(2-(o-sulfamoylphenyl)benzimidazolate)2] 3 was identified as the most active antibacterial compound, while none of the compounds exhibited antifungal activity.