Binuclear copper and zinc complexes possessing bio-potential ligands: synthesis, characterization, antimicrobial, SOD mimetic, DNA binding, and cleavage studies

Schiff bases (L) viz, N,N′,N′′,N′′′-tetra-3,4-dimethoxybenzalidene-3,3′-diaminobenzidine (TDBD), N,N′,N′′,N′′′-tetra-4-hydroxy-3-methoxybenzalidene-3,3′-diaminobenzidine (THMBD), and N,N′,N′′,N′′′-tetra-3-hydroxy-4-nitrobenzalidene-3,3′-diaminobenzidine (THNBD) afford binuclear [M2LCl4] complexes where M = Cu(II) or Zn(II). These Schiff bases and their binuclear complexes have been characterized by analytical and spectral data showing square-planar geometry on metalation with Cu2+. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder distamycin suggest that these synthesized complexes bind to the major groove. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), they show chemical nuclease activity. They also show an efficient photo-induced DNA cleavage on irrad...