Synthesis, Characterization and Antimicrobial Properties of New Thiosemicarbazones and their Metal Complexes

Abstract

The study of thiosemicarbazones has been the focus of numerous investigations for a variety of reasons which range from their promising biological and pharmacological applications as anti-tumor, anti-bacterial, anti-fungal and anti-viral agents to the chemical and analytical applications as potential chelating agents and ion sensing materials. In view of this, two new heterocyclic thiosemicarbazones containing 2-phenylindole and 3-acetylcoumarine nuclei have been synthesized by reacting 2-phenylindole-3-carboxaldehyde and 3-acetylcoumarine with thiosemicarbazide in ethanolic medium. These compounds have been used as ligands for the synthesis of metal complexes. The complexes were prepared by reacting equimolar amounts of ligands with the metal ions Cu(II), Ni(II), Co(II), Zn(II), Cd(II) and Hg(II) in ethanolic medium. Both the ligands as well as metal complexes have been characterized by various physico-chemical techniques such as elemental analysis, UV-Vis, magnetic susceptibility, conductance measurements, IR, NMR, mass, FAB mass, and ESR data. Further, thiosemicarbazones are known for their interesting mesomeric behaviour attributed to the restricted rotation C-N bond and hence the terminal –NH₂ protons are non-equivalent and give two sets of signals. This property of both the ligands has been studied by 1D and 2D NMR analysis using ¹H-¹H DQF-COSY and TOCSY experiments. The ligands as well as their complexes have been tested for their antibacterial and antifungal properties. Both the ligands and their complexes have shown good antifungal and moderate/less antibacterial properties. The results will be discussed.