A Novel Tetradentate Thiazole-Based Schiff Base Ligand and its Binuclear Co(II), Ni(II), Cu(II) and Zn(II) Complexes: Synthesis, Spectral, Structural and Electrochemical Investigation

Schiff base ligands, formed by the condensation of primary amines and aldehydes or ketones, are widely studied due to their strong coordination ability, structural versatility, and broad applications in catalysis, medicinal chemistry, and materials science. In the present study, a novel tetradentate N₂-N₂ thiazole-based Schiff base ligand was synthesized, and its coordination complexes with Co (II), Ni (II), Cu (II), and Zn (II) metal ions were prepared. The Schiff base ligand (LA), 1,4-phenylene-bis-N-(5-methylthiazol-2-yl) methanimine, was obtained by condensing terephthaldehyde and 5-methylthiazole-2-amine in a 1:2 molar ratio, and its metal complexes were synthesized by reacting the ligand with the corresponding metal salts. The ligand and its metal complexes were characterized using Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, nuclear magnetic resonance (¹H and ¹³C NMR), powder X-ray diffraction (PXRD), and elemental analysis. The analytical results confirmed that the Schiff base ligand coordinates to the metal ions through the azomethine nitrogen and thiazole nitrogen atoms. Thermal stability studies revealed that coordination with metal ions enhances the stability of the complexes.