Synthesis, Characterization, Antimicrobial, DNA Binding and Cleavage Studies of Mixed Ligand Cu(II), Co(II) Complexes

The mixed ligand complexes MLA of Cu(II) and Co(II) with Schiff base derived from 4-amino antipyrine and 5-NO2 salicylaldehyde (2,3 –dimethyl-1-phenyl-4-(2-hydroxy-5-nitro benzylideneamino)-pyrazol-5-one) as ONO donor (L) and A = 2,2 bipyridine (bpy),1,10 phenonthroline (1,10 phen) as N, N donor ligands have been prepared, owing to their biological and other applications. The structural features have arrived from their elemental analyses, magnetic susceptibility, molar conductance, Mass, IR, UV–VIS, powdered XRD and ESR spectral studies, that established MLA type of composition for the metal complexes. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion. The interaction of the complexes with Calf Thymus (CT) DNA has been studied using absorption spectra, viscosity measurements and fluorescence spectra. The binding constants (Kb) of the complexes were determined as 2.1 × 106 M−1 for complex 1, 2.5x106M−1 for complex 2, 1.16 × 106 M−1 for complex 3,1.25x106M−1 for complex 4, DNA cleavage experiments performed on pBR-322 plasmids using metal complexes in the presence of H2O2 showed that all the complexes afford a pronounced DNA cleavage. Molecular modelling studies were also performed to confirm the geometries of the complexes. The ligand and their metal complexes were screened for their antimicrobial activity against bacteria. The results showed that the metal complexes are biologically active.