Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized by the Schiff bases derived from 3-formyl-2-mercaptoquinoline with 4-nitro-ortho-phenylinediamine. The synthesized Schiff bases and chelates were characterized by elemental analysis, molar conductance, magnetic susceptibilities, UV-Fluorescence, IR, 1H-NMR, Fabmass, ESR and thermal studies. The results indicate that, the ligand acts as a octahedral geometry. The ligands and their metal complexes have been screened in vitro for antibacterial and antifungal studies. The results showed that the biological activity of the ligands get increased on complexation. The Cu(II) and Ni(II) complexes are found to be potent in DNA cleavage studies.