Three new Schiff base ligands derived from piperonal and diamine compounds(ethane-1,2-diamine, propane-1,3- diamine, butane-1,4-diamine) have been synthesized. These ligands were treated with Co(II) chloride with a metal : ligand ratio of 1:1 to afford the three new complexes [CoL1(H2O)2]Cl2, [CoL2(H2O)2]Cl2 and [CoL3(H2O)2]Cl2. These ligands and complexes have been characterized by techniques like IR, NMR, UV visible absorption, atomic absorption, molar conductance, molecular weight determination and magnetic measurements. The data shows that the ligands are bidentate and the linked sites are two azomethine nitrogen. The complexes are suggested as electrolytes paramagnetic, compounds and they have coordination number equal four. The ligands and metal complexes were screened for their antimicrobial activities against gram positive bacteria and gram negative bacteria. They were found to biologically active.