Synthesis, characterization of 2-amino thiazol schiff base and its metal (II) complexes

Metal(II) complexes of a Schiff base derived from 2-hydroxy-1-naphthaldehyde and 2-aminothiazole were synthesized through reactions with acetate salts of Zn(II), Co(II), and Ni(II). The resulting metal complexes were characterized using various analytical methods, including elemental analysis, molar magnetic susceptibility, and spectral techniques. Fourier-transform infrared (FTIR) spectroscopy of the free Schiff base (HL) revealed a characteristic band at 1620 cm⁻¹, attributed to the azomethine (C=N) functional group. In the metal complexes, this band shifted to the range of 1640–1642 cm⁻¹, indicating coordination through the azomethine nitrogen atom. UV-Visible (electronic) spectral analysis suggested that the complexes exhibit either octahedral or tetrahedral geometries, based on their electronic transition patterns. The ligand and its metal(II) complexes displayed solubility in common organic solvents such as ethanol, methanol, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF), but showed limited solubility in chloroform and were insoluble in water. The synthesized complexes also exhibited high thermal stability, with melting points ranging from 225°C to 300°C. Visually, the metal complexes appeared in various shades of black, while the free Schiff base ligand was yellow in color. The values obtained for the Co(II), Ni(II), and Zn(II) complexes for molar conductance studies were 18.8, 11.9, and 29.6 Ω⁻¹·cm²·mol⁻¹, respectively are markedly lower, indicating non-electrolytic behavior in solution. Magnetic susceptibility data supported the proposed geometries and electronic configurations, confirming high-spin octahedral and tetrahedral arrangements for Co(II) and Ni(II), respectively, and diamagnetism for the Zn(II) complex.