Spectroscopic, thermal analysis and antimicrobial activities of supramolecular Cu(II) complexes

A series of Cu(II) complexes of azo dye ligands 4-(4-hydroxy-5-(aryldiazenyl)-2-thioxothiazol-3(2H)-yl)benzenesulfonamide (HLn) were synthesized by the coupling of 3-sulfamoylphenylrhodanine with aniline and its p-derivatives. These ligands and their [Cu(Ln)(CH3COO)(OH2)]H2O complexes were characterized by elemental analyses, IR, 1H NMR, UV–Visible and magnetic measurements as well as thermal analysis and X-ray diffraction. The molar conductance measurements proved that all the complexes are non-electrolytes. IR spectra showed that the ligands (HLn) acts as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (–N N–) and oxygen atom of the deprotonated –OH group moiety, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. Spectral studies revealed that the ligand exist in an internally hydrogen bonded azo-enol form rather than the keto-hydrazone form a coordinated to the metal ion in a bidentate fashion. Analytical data revealed that all the complexes exhibited 1:1 metal-ligand ratio. Based on the ESR and electronic spectral data, the bonding parameters of these complexes have been calculated. The thermodynamic parameters of the ligands (HLn) and their Cu(II) complexes are calculated using Coats–Redfern and Horowitz-Metzger methods. The antimicrobial activities of ligands were tested against gram negative bacteria (Escherichia coli), gram positive bacteria (Staphylococcus aureus) and fungal (Candida albicans). The cytotoxic activity of ligands (HLn) was tested against two human cancer HePG-2 (Hepatocellular carcinoma) and MCF-7 (breast cancer). The antioxidant activities of ligands (HLn) were performed by ABTS method.