Copper(II) complexes with isoxazole Schiff bases: Synthesis, spectroscopic investigation, DNA binding and nuclease activities, antioxidant and antimicrobial studies.

Abstract Three novel Cu(II) complexes 1 [Cu(L1) 2 ], 2 [Cu(L2) 2 ] and 3 [Cu(L3) 2 ], where L1H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-6-tert-butylphenol, L2H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4,6-di-tert-butylphenol and L3H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4,6-dibromophenol were synthesized and characterized by elemental analysis, FT-IR, UV–Visible, 1H NMR, 13C NMR, ESI mass, EPR and magnetic susceptibility studies. Based on spectroscopic and analytical data, a square planar geometry is assigned for all complexes. DNA binding and cleavage studies against calf thymus DNA (CT-DNA) and supercoiled pBR322 DNA respectively revealed an intercalative mode of binding and also cleave pBR322 DNA in an efficient manner. The ligands and their complexes were examined for antimicrobial activity against bacterial species E. coli, B. subtilis and fungal species S. rolfsii and M. phaseolina and found that all the Cu(II) complexes show more activity than the free Schiff base ligands. The antioxidant activity of metal complexes have also been determined using DPPH assay and found that the complexes are found to be good free radical scavengers. Graphical abstract Image 1 Highlights • Isoxazole Schiff bases and their Cu(II) complexes are prepared and characterized. • All the complexes have adopted square planar geometry. • The complexes have shown better inhibitory potential towards tested microorganisms. • DPPH assay proved that complexes are good free radical scavengers. • Complexes act as good DNA intercalating agents and also cleave DNA efficiently. [ABSTRACT FROM AUTHOR]