Cu(II) complexes with 4-amino-3,5-dimethyl isoxazole and substituted aromatic aldehyde Schiff bases: synthesis, crystal structure, antimicrobial activity, DNA binding and cleavage studies

AbstractThree isoxazole Schiff bases 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-methoxyphenol (L1), 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-4,6-diiodophenol (L2), 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-bromo-4-chlorophenol (L3), and their Cu(II) complexes [Cu(L1)2] (1), [Cu(L2)2] (2) and [Cu(L3)2] (3) were synthesized. All the complexes have been characterized by elemental analysis, FT-IR, ESI mass, UV-Visible, ESR, TGA, magnetic moments, and single-crystal X-ray diffraction analysis. Based on analytical data, a square planar geometry is assigned to the Cu(II) complexes with N2O2 donors from the Schiff base ligands. The single-crystal X-ray diffraction measurements of 1 and 2 confirmed the square planar geometry. DNA binding studies from electronic absorption titrations, viscosity measurements, and fluorescence quenching studies indicated an intercalation mode of binding of Cu(II) complexes with CT-DNA. DNA cleavage experiments of Cu(II) complexes with supercoiled plasmid pBR322 DNA...