A new thiosemicarbazone, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one N (4)-phenyl thiosemicarbazone (HBATB4ph), has been synthesized and characterized experimentally and theoretically. The complexing ability of this thiosemicarbazone towards copper (II) salts have been explored. The reactions of the hot ethanolic solutions of copper(II) salts with HBATB4ph led to the formation of the novel complexes compositions [Cu(HL)X2 ] (X= Cl- or Br-), [Cu(HL)(H2O)2 ](ClO4 )2 and [Cu(L)H2O)X] (X=NO3 -, CH3COO- or SO4 -). The newly synthesized complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility, I.R., electronic and ESR spectral studies. Visible and ESR spectra indicate that the complexes are monomeric having square planar geometry. These complexes were screened for their antibacterial activities on different species of bacteria and their biopotency has been discussed.
