Synthesis and Characterization of Thiosemicarbazones and their Coordination Compounds

Thiosemicarbazones (TSC) appear as promising ligands in the synthesis of metal compounds with a possible activity against tumor cells [1]. Studies showed that thiosemicarbazones and their square planar complexes are important to interact with active site of the enzyme topoisomerase [2,3]. Therefore, in this work we synthesize some TSC ligands and their bis-chelated complexes of Ni(II) and Pd(II) once d8 metals are great choice to achieve this geometry. Synthesis of the thiosemicarbazone of interest consists in a condensation reaction between a ketone/aldehyde and a thiosemicarbazide in ethanolic medium catalyzed by acid. Synthesis of the Pd(II)/Ni(II) complexes is carried out by adding the ligand in proportions 2:1 (ligand:metal). Solutions were stirred at room temperature in acetonitrile over 24h. Figure 1 below represents the synthesis scheme of the compounds. All compounds obtained will be characterized by the following techniques: UV-Vis spectroscopy, infrared absorption spectroscopy, NMR and elemental analysis. Among the results, it was possible to observe the presence of the characteristic bands for thiosemicarbazone in the IR spectrumC=S (763cm-1);C-N (1261cm-1); C=N (1535cm-1);N-H (3319cm-1). No peaks were found in NMR spectra attributed to the olefin protons of the ketone. NMR techniques HSQC and COSY were crucial to confirm the break of double bond.