Synthesis and spectral characterization of Cu(II) complexes of some thio-Schiff bases of acyl pyrazolone analogues

Abstract

A series of tridentate pyrazolone-based thio-Schiff bases were synthesized by the interaction of 4-acyl/aroyl pyrazolones with thiosemicarbazide in an ethanolic medium. All of these ligands were characterized on the basis of elemental analysis, infrared (IR), ¹H- and ¹³C-NMR data. Nuclear magnetic resonance (NMR) suggests the amine-one form of ligand in solution at room temperature. Copper Schiff-base complexes, [Cu(L)(H₂O)], have been prepared by the interaction of the aqueous solution of copper sulfate pentahydrate with hot ethanolic solution of the appropriate ligand. The resulting complexes have been characterized by elemental analysis, metal content determination, molar conductance, fast atom bombardment mass spectra, magnetic measurements, thermogravimetric analysis (TGA), IR, and electronic spectral studies. Thermal stability, heat capacity, and activation energy of thermal degradation for these complexes were determined by TGA, differential thermal analysis, and differential scanning calorimetry. Suitable structures are proposed for these complexes.

Keywords:

• Acyl pyrazolone
• Copper complexes
• Thio-Schiff base
• Thiosemicarbazone

Acknowledgments

Financial assistance for carrying out this work was provided by University Grants Commission, New Delhi, in terms of minor research project to R.N. Jadeja is gratefully acknowledged. The authors are also thankful to Head of the Department of Geology for providing TG/DTA facility.