Synthesis, Characterization and Biological Studies of Some Transition Metal Complexes with 5-(4-bromophenyl)-3-(thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-carbothioamide Ligand

Abstract

A 2-pyrazoline based bi dentate ligand 3-(2-thiophen-2-yl)-5-(4-bromophenyl)-1-carbothiomyl-2-pyrazoline has been synthesized by Claisen-Schmidt condensation of 2-acetylthiophene with 4-bromo benzaldehyde followed by cyclization of the resulting chalcone with thiosemicarbazide. The chromium(III), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of the new pyrazoline based-ligand were prepared by the direct reaction of their hydrated metal chlorides with the free ligand and separated in solid state. The metal complexes were characterized by (C.H.N.S) elemental analysis, FT-IR, UV-Vis, 1H, 13C NMR and mass spectra. As well as the molar conductance measurements in DMSO solutions suggested non-electrolytic nature of all complexes except chromium(III) complexes which was electrolyte in 1:1 ratio supporting the proposed formula of the complexes [ML2Cl2] M= Mn, Co, Ni, Cu, Zn(II) and [CrL2Cl2]Cl. The solution of ligand and it’s metal complexes were investigated for their ability to kill Esherichia coli and Staphylococcus aureas bacteria, Candida albicans and Burkholderia cepacia via diffusion method. It is found from biological results that the copper(II) and zinc(II) complexes showed high inhibition for bacteria growth with compared to the antibiotic drug. However, the free ligand in DMSO exhibited highest inhibition in 12 mm zone compared with its complexes. The resulted obtained showed that the Mn(II), Co(II), Cu(II) and Ni(II) complexes showed medium activity whereas the chromium(III) complex showed inhibition zone toward in the range (18-22) against Esherichia coli and Burkholderia cepacia.