Synthesis, Crystal Structure, Characterization and DNA Binding Studies of Novel Copper (II) Complex Based on Amino Acid Schiff Base

Abstract

A novel Schiff base ligand (H2L) from the reaction of 1-phenyl-3-methyl-4-(2-furoyl)-5-pyrazolone with β-alanine and its copper (II) complex [CuLCH3OH]n (1) was synthesized and characterized by elemental analysis, UV, IR, 1H NMR, 13C NMR, MS, EPR, X-ray single crystal diffraction, variable temperature susceptibility measurement and thermogravimetric analysis. The crystal of the complex is a orthorhombic system with crystal parameters: P212121, a= 7.5169(6) Å, b= 13.2788(10) Å, c= 18.5631 (14) Å, α=90.00º, β= 90.00º, γ= 90.00º, V= 1852.9(2) Å3, Z= 4. It was found that the copper (II) complex had a distorted square pyramid coordination environment with two O, one N atoms of H2L ligand and one O atom at carboxyl group of another molecular in the square plane, and with CH3OH at the apex of polyhedron. The complex molecular is a coordination polymer. DNA-Binding properties of the Cu(II) complex and Schiff base ligand have been carried out by UV-vis, fluorescence spectra, circular dichroism spectra and in cleavage of plasmid pGreen DNA. The experimental results indicated that complex 1 and H2L both bind through electrostatic interaction to DNA. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of complex 1 and the ligand, indicating that they displace EB from its binding site in DNA. Further, Circular dichroism (CD) spectra of DNA with the addition of the H2L and [CuLCH3OH]n exhibit a decrease in both the positive and negative peaks. Agarose gel electrophoresis shows that they can cleave plasmid pGreen DNA. Keywords: Acylpyrazolone, Amino acid schiff base, Coordination polymer, DNA binding activity, Hyperchromism, DNA cleavage.