Syntheses, characterization and antimicrobial screening of N-(benzothiazol-2-yl)-2,5-dichlorobenzenesulphonamide and its Cu(I), Ni(II), Mn(II), Co(III) and Zn(II) complexes

Abstract

N-(Benzothiazol-2-yl)-2,5-dichlorobenzenesulphonamide (DCBS2ABT) was synthesized by the condensation (by refluxing) of 2-aminobenzothiazole and 2,5-dichlorobenzenesulphonylchloride in acetone at 230 °C. The resulting crude precipitates were recrystallized in absolute ethanol. Five metal complexes of copper(I), nickel(II), manganese(II), cobalt(III) and zinc(II) of the ligand were synthesized. The compounds were characterized using magnetic susceptibility measurements, UV/visible spectrophotometry, elemental microanalysis, infrared, 1H and 13C NMR spectroscopies. The antimicrobial tests of the ligands and its metal complexes were carried out on both multiresistant bacterial strains isolated under clinical conditions and cultured species using agar-well diffusion method. The multi-resistant bacterial strains used were Escherichia coli, Proteus species, Pseudomonas aeroginosa and Staphylococcus aureus were isolated from dogs. The culture species were Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922) Staphylococcus aureus (ATCC 25923) and the fungi, Candida krusei (ATCC 6258) and Candida albicans (ATCC 90028). The tests were performed both in vitro and in vivo. Thus the inhibition zone diameter, the minimum inhibitory concentration and the lethal and effective concentrations (LC50 and EC50) were determined. The antimicrobial activities of the compounds were compared with those of ciprofloxacin and trimethoprimsulphamethoxazole as antibacterial agents and fluconazole as an antifungal drug. All the compounds showed varying activities against the cultured typed bacteria and fungi used. However, they were less active than the standard drugs used except fluconazole, which did not show any activity against Candida krusei (ATCC 6258) but the ligand, DCBS2ABT and all the metal complexes synthesized were very active against it. The lethal concentration (LC50) ranged from 81.00 ± 6.8-256.30 ± 36.7 ppm. These are within the permissible concentrations.