Biophysical studies on the interaction of a novel oxime based palladium(II) complex with DNA and RNA

A novel oxime based palladium(II) complex (1) has been synthesized out of the reaction of a Schiff base ligand, 1-phenyl-1-(pyridin-2-yl-hydrazono)-propan-2-one oxime (LH₂) with Na₂[PdCl₄] in THF. Red and diamagnetic 1 has thoroughly been characterized by several analytical and spectroscopic means like CHN, ESI-MS, FAB-MS, FT-IR, ¹H NMR, ¹³C NMR, UV-Vis and molar electrical conductivity measurements. Geometry optimizations at the level of DFT reveals that the Pd(II) centre in 1 is nested in a square-planar 'N₃Cl' coordination environment. Semi-empirical BVS mode of analysis was also undertaken to reproduce the oxidation state of the palladium centre. 1 shows quasi-reversible Pd(II)/Pd(III) and Pd(III)/Pd(IV) redox couples in its CV in acetonitrile. The photophysical studies reveal that 1 is two-fold less emissive than its tethering ligand. Several biophysical studies have been undertaken to demonstrate the binding aspects of DNA and RNA with 1. Ethidium bromide displacement study concludes that 1 is partially intercalated to the CT DNA. Thermodynamic parameters of binding have also been determined from temperature dependent fluorescence spectroscopy employing the van't Hoff plot. The binding constants as determined from McGhee-von Hippel equation (Scatchard plot) indicate that 1 is a good binder of both DNA and RNA. However, the magnitude of the binding constant as determined for RNA interaction with 1 is found to be higher than that for DNA interaction.