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Three Schiff base ligands, L1H = (2-((benzo[d]thiazol-6-ylimino)methyl)-6-nitrophenol), L2H = (2-((benzo[d]thiazol-6-ylimino)methyl)-4,6-diiodophenol), L3H = (2-((benzo[d]thiazol-6-ylimino)methyl)-4-bromo-6-methoxyphenol) and their binary metal complexes, 1 [Cu(L1)2], 2 [Co(L1)2], 3 [Cu(L2)2], 4 [Co(L2)2], 5 [Cu(L3)2] and 6 [Co(L3)2], have been synthesized and characterized by elemental analysis, NMR, ESI mass, FT-IR, ESR, UV–Visible, magnetic susceptibility and TGA studies. The analytical and various spectral data suggested a square-planar geometry around the metal for all complexes with N2O2-donor atoms from the Schiff base ligands. Antimicrobial study was investigated against two Gram-positive, Bacillus amyloliquefaciens and Staphylococcus aureus, and one Gram-negative, Escherichia coli, bacteria as well as against two fungal species, Macrophomina phaseolina and Sclerotium rolfsii, by using Streptomycin and Mancozeb as standard drugs, respectively. The results revealed that metal complexes show more potent activity than free ligands and moderate compared to standard drugs. The free-radical scavenging ability of the complexes was evaluated by DPPH and ABTS assay methods using ascorbic acid as a standard antioxidant, complexes 1 and 2 showed good scavenging activity. DNA-binding titrations were also performed and indicated that all complexes bind to calf-thymus DNA via an intercalation mode. Additionally, the complexes exhibited good cleavage ability against the pBR322 DNA even at low concentrations in the presence of activators, H2O2 as well as UV light. [ABSTRACT FROM AUTHOR]

• Ligand and its Cu(II), Ni(II) and Co(II) metal complexes have been synthesized. • All the compounds were characterized by spectroscopic and analytical techniques. • The DNA binding and cleavage studies have been studied. • The compounds were screened for in-vitro antibacterial activity. • The in-vitro cytotoxicity of the compounds was also investigated by MTT assay. Novel Schiff base (L) derived from 6-aminobenzothiazole and 4-methoxy salicylaldehyde and its bivalent Cu(II) (1), Ni(II) (2) and Co(II) (3) metal complexes were synthesized and thoroughly characterized by various analytical and spectral techniques. From the data a square planar geometry is assigned for all complexes. The DNA interaction studies of complexes with CT-DNA were carried out by UV–Vis absorption, fluorescence and viscosity measurements. These studies revealed that the complexes bind to CT-DNA by intercalative mode. DNA cleavage capacity of all the metal complexes was studied by agarose gel electrophoresis method. Further, the antibacterial studies of metal complexes were evaluated and it is observed that all complexes showed grater activity than free ligand. In addition, in-vitro cytotoxicity of these complexes on tumor cell lines HeLa, A549 and MCF - 7 have been examined by MTT assay. The complexes showed greater cytotoxicity than the free Schiff base ligand. [ABSTRACT FROM AUTHOR]