Cu(II), Ni(II), and Zn(II) Complexes of Salan-Type Ligand Containing Ester Groups: Synthesis, Characterization, Electrochemical Properties, and In Vitro Biological Activities

A salen ligand on reduction and N-alkylation affords a novel [N2O2] chelating ligand containing ester groups [L = diethyl-2,2'-(propane-1,3-diylbis((2-hydroxy-3-methoxy benzyl)azanediyl))diacetate]. The purity of the ligand was confirmed by NMR and HPLC chromatograms. Its Cu(II), Ni(II), and Zn(II) complexes were synthesized and characterized by a combination of elemental analysis, IR, NMR, UV-Vis, and mass spectral data, and thermogravimetric analysis (TG/DTA). The magnetic moments, UV-Vis, and EPR spectral studies support square planar geometry around the Cu(II) and Ni(II) ions. A tetrahedral geometry is observed in four-coordinate zinc with bulky N-alkylated salan ligand. The redox properties of the copper complex were examined in DMSO by cyclic voltammetry. The voltammograms show quasireversible process. The interaction of metal complexes with CT DNA was investigated by UV-Vis absorption titration, ethidium bromide displacement assay, cyclic voltammetry methods, and agarose gel electrophoresis. The apparent binding constant values suggest moderate intercalative binding modes between the complexes and DNA. The in vitro antioxidant and antimicrobial potentials of the synthesized compounds were also determined.