Electron Spin Resonance Spectral Characterization and DNA Binding Studies of Metal Complexes with Heterocyclic Ligands Derived from 4 -Aminoantipyrine and 5-Chlorosalicylaldehyde / 3-Ethoxysalicylaldehyde

Abstract

Transition metal complexes of Cu(II), Ni(II)and Co(II) have been synthesized involving the heterocyclic Schiff bases, 2,3-dimethyl-1-phenyl-4-(5-chloro-2-hydroxybenzylideneamino)-pyrazol-5-one (5-ClSALAAP), L 1 and 2,3-dimethyl-1-phenyl-4-(3-ethoxy-2-hydroxy benzylideneamino)-pyrazol-5-one (3-OEtSALAAP), L 2 derived from 4-aminoantipyrine and 5-chlorosalicylaldehyde/ 3-ethoxysalicylaldehyde respectively. These Schiff bases act as tridentate ligands which coordinate through the azomethine nitrogen, phenolic oxygen and carbonyl of antipyrine ring. The ESR Spectra of Cu(II) complexes were recorded at room temperature in the polycrystalline state. These complexes exhibited well resolved anisotropic signals in the parallel and perpendicular regions. The trend, g Π > g ┴ >2.0023 observed for the complexes indicate that unpaired electron is localised in d x 2 -y 2 orbital of the Cu(II) ion. Hence a distorted octahedral geometry is proposed for the complexes. The value of exchange interaction was estimated from the equation, G =(g Π -2) /(g ┴ -2). The complexes showed G values < 4 indicating the exchange interaction in complexes. Binding of these complexes with calf thymus DNA(CT DNA) was studied by spectroscopic methods and their binding constants were evaluated.