DNA interaction, antimicrobial studies of newly synthesized copper (II) complexes with 2-amino-6-(trifluoromethoxy)benzothiazole Schiff base ligands

•Four novel Cu(II) complexes have been synthesized and characterized.•The complexes adopted a square planar geometry.•The complexes bound calf thymus DNA through an intercalation mode.•The complexes cleaved pBR322 DNA effectively.•Complexes showed better antimicrobial activity than corresponding ligands.

Four novel Schiff base ligands, L1 (1-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)naphthalen-2-ol, C19H11F3N2O2S), L2 (3-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)benzene-1,2-diol, C15H9F3N2O3S), L3 (2-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)-5-methoxyphenol, C16H11F3N2O3S) and L4 (2-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)-4-bromophenol, C15H8BrF3N2O2S) and their binary copper(II) complexes 1 [Cu(L1)2], 2 [Cu(L2)2], 3 [Cu(L3)2] and 4 [Cu(L4)2] have been synthesized and characterized by elemental analysis, 1H NMR, 13C NMR, ESI mass, FT-IR, ESR, UV-Visible, magnetic susceptibility, TGA, SEM and powder XRD studies. Based on spectral and analytical data, a square planar geometry is assigned for all Cu(II) complexes. The ligands and their Cu(II) complexes have been screened for antimicrobial activity against bacterial species E. coli, P. aeruginosa, B. amyloliquefaciens and S. aureus and fungal species S. rolfsii and M. phaseolina and it is observed that all Cu(II) complexes are more potent than corresponding ligands. DNA binding (UV absorption, fluorescence and viscosity titrations) and cleavage (oxidative and photo cleavage) studies of Cu(II) complexes have also been investigated against calf thymus DNA (CT-DNA) and supercoiled pBR322 DNA respectively. From the experimental results, it is found that the complexes bound effectively to CT-DNA through an intercalative mode and also cleaved pBR322 DNA in an efficient manner. The DNA binding and cleavage affinities of newly synthesized Cu(II) complexes are in the order of 2 > 1 > 3 > 4.

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