Two novel complexes of Ni(II) and Pd(II) with Schiff base ligand derived from 5-chloro isatin with 4-phenyl-3-thiosemicarbazid have been synthesized in absolute EtOH. The structures of the isolated solid compounds have been characterized by elemental analyses and spectral (FT-IR and UV-vis.) measurements. The Schiff base ligand was further characterized by mass spectra. All the synthesized compounds were tested against supercoiled pBR322 DNA. It has been found that, the Schiff base ligand behaves as trientate ligand forming chelates with 1:2 (metal:ligand) in case of Ni-complex and 1:1 (metal:ligand) in case of Pd-complex. Octahedral geometry was suggested for the Ni(II) chelate while square-planar geometry was suggested for the Pd(II) chelate. These compounds have been found to promote the cleavage of plasmid DNA pBR322 in the presence of H2O2.Keywords: 5-chloro isatin; 4-phenyl-3-thiosemicarbazid; trientate ligand; supercoiled pBR322.