Studies on the Interactions of Biological Metal Ions with some Sulphonamide Drugs. Part-I Equilibrium Study on the Complex Formation of Cobalt(II), Nickel(II), Copper(II) and Zinc(II) with Sulphapyridine, Sulphadiazine and Sulphathiazole

Department of Chemistry, University College of Science, 92 Acharya Prafulla Chandra Road, Calcutta-700 009 Manuscript received 30 August 1993 Combined pH-metric and spectrophotometric studies on the complex formation of M2+ ions (M =Co, Ni, Cu and Zn) with sulphapyridine, sulphadiazine and sulphathiazole (LH) provided evidence of formation of binary complexes ML+ and ML2, together with ternary hydroxo complexes of the types, ML(OH), ML2(OH)- and ML2(OH)-. Formation constants of the complexes were determined at 30 ± 0.1° in 50%(v/v) aqueous ethanol medium at a constant ionic strength, 1= 0.1 M (NaNO3). Stability of the complexes were found to be in the order : CoII ZnII for all the three ligands, and in the order: sulphapyridine > sulphathiazole > sulphadiazine with CoII, NiII and ZnII , whereas in the order : sulphadiazine > sulphapyridine > sulphathiazole with CuII. Stability of the complexes were correlated with the modes of bonding of the ligands