Synthesis, Spectroscopic, and Thermal Characterization of Thiazole Metal Complexes: Biological Activity Studies

Abstract

Metal complexes of the organic ligand with N azomethine and N thiazole donation sites, derived from 3-(2-(2-(2,6-dichlorobenzylidene)hydrazinyl)-4-oxo-4,5-dihydrothiazol-5-yl) acetic acid (H₂L), with some transition metal ions, namely Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II), are reported. They are characterized based on elemental analyses, IR, ¹H NMR, solid reflectance, magnetic moment, and molar conductance. The ionization constants are found to be 5.57 and 11.50, which can be attributed to loss of the hydrazo and the carboxylic acid protons, respectively. The stability constants of metal chelates, is calculated spectrophotometrically at 25°C, and the order of stability follows the Irving and Williams order. The chelates are found to have octahedral geometrical structures. The ligand (H₂L) and its binary chelates are subjected to thermal analyses, and the different activation thermodynamic parameters are calculated using Coats-Redfern equation. The ligand and its metal complexes show a remarkable biological activity against the desert locust Schistocerca gregaria (Forsk) (Orthoptera – Acrididae) and its adult longevities.

Keywords:

• biological activity
• thermal analyses
• thiazole ligand
• transition metal complexes
• spectroscopy