Synthesis,characterization, thermal decomposition studies and dyeing properties of some novel transition metal complexes of an azo derivative formed from 2-aminothiophene

An azo derivative was synthesized by coupling diazotized 2-amino-3-carbethoxy-4,5-dimethylthiophene with 2-naphthol and this new ligand formed a series of metal complexes with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) salts. These complexes were characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, UV-Visible, IR and ¹H NMR spectral data. Analytical data revealed that all the complexes exhibited 1: 1 metal-ligand ratio. Spectral studies showed that the ligand existed in an internally hydrogen bonded azo-enol form rather than the keto-hydrazone form and coordinated to the metal ion in a tridentate fashion. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry was proposed for each complex. The ligand and its cobalt(II) complex were subjected to X-ray diffraction study. The thermal behaviour of the ligand and its copper(II) complex was examined by thermogravimetry. The ligand and its copper(II) and nickel(II) complexes were applied to silk fabric and their fastness properties were evaluated.