A novel thiosemicarbazone ligands 2-hydroxybenzaldehyde-4-(3-chlorobenzothiophene-carbonyl)-3-thiosemicarbazone (SL1) /thiophen-2-aldehyde-4-(3-chlorobenzothiophenecarbonyl)-3-thiosemicarbazone(SL2) obtained by the condensation of 3-chlorobenzo[b]-thiophene-2-carbonylchloride with thiophene-2-ylmethylenethiosemicarbazide/2-hydroxyphenylmethylene-thiosemicarbazide and its newly synthesized Co(II), Ni(II), Cu(II) and Zn(II) complexes were characterized by elemental analysis, molar conductance, magnetic susceptibility measurements thermal analysis and various spectral studies like UV-Visible, FT-IR, 1H NMR, 13C NMR, mass and EPR. The ligands behaved as tetra dentate donor and forms the complexes of type [ML(Cl)2]. The molar conductance data reveal that the chelates were non-electrolytes. From the Ultraviolet/Visible spectra and magnetic moment data, the complexes were found to have octahedral geometrical structure. In vivo evaluation of the antimicrobial activities of the metal complexes and the ligands, complexes showed greater activity against some micro-organisms when compared to the parent compounds. The redox behavior of complexes was investigated by cyclic voltammetry.