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, -(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. 1. Introduction Salen metal complexes are the interest of many workers because of their applications in food industry, in the treatment of cancer [1], as antibactericide agents [2, 3], as antivirus agents [4], as fungicide agents [5], and for other biological properties [6]. The antitumor activity of salen complex arises due to its DNA binding properties. The salen complexes are conformationally flexible and adopt a variety of geometries. Also, salen metal complexes have a unique flat electron-rich aromatic surface that may facilitate their interactions with nucleic acids. Hydroxyl groups in the salen complexes act as a quinone system which would cooperate to facilitate the formation of free radicals responsible for DNA cleavage [7]. The biological properties of salen complexes are enhanced by functionalization with a variety of substituents [8–11]. When salen compounds are reduced at the imine function, the more flexible, reduced salen derivatives (salan) are obtained. Considerable attention has been devoted to the preparation and structural characterization of metal complexes containing salen-type ligands. However, little attention has been paid to systems in which functionalized salan is used as ligands. In the present investigation N-alkylated salan complexes are used for DNA binding and antimicrobial and antioxidant properties. In
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