Metal complexes of a novel Schiff base derived from sulphametrole and varelaldehyde. Synthesis, spectral, thermal characterization and biological activity

Metal complexes of a novel Schiff base (HL = 3-(4′-ethylazomethinobenzene sulphonamide)-4-methoxy-1,2,5-thiadiazole) derived from condensation of sulphametrole and varelaldehyde are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, and thermal analysis (TG). From the elemental analyses data, 1:1 metal complexes are formed having the general formulae [MCl3(HL)(H2O)]·3H2O (M = Cr(III), Fe(III)) and [MCl2(HL)(H2O)2]·yH2O (where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II), y = 0–3). The important infrared (IR) spectral bands corresponding to the active groups in the ligand and the solid complexes under investigation were studied. IR spectra show that HL is coordinated to the metal ions in a neutral bidentate manner with ON donor sites of the enolic sulphonamide-OH and thiodiaza-N. The solid complexes have been synthesized and studied by thermogravimetric analysis. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats–Redfern equation. All the metal chelates are found to be non-electrolytes. From the magnetic and solid reflectance spectra, the complexes have octahedral structures. The antibacterial and antifungal activities of the synthesized ligand and its metal complexes were screened against bacterial species (Escherichia coli and Staphylococcus aureus) and fungi (Candida and Aspergillus flavus). The activity data show that the metal complexes have a promising biological activity comparable with the parent Schiff base ligand against bacterial and fungal species.