Bipyrazole-based palladium(II) complexes as DNA intercalator and artificial metallonuclease

Abstract

Substituted 3′-methyl-1′,2-diphenyl-3,4-dihydro-1′H,2H-3,4′-bipyrazole and their square planar palladium(II) complexes of type [Pd(4n)Cl2], where 4n = bipyrazole-based ligands, have been synthesized. The compounds have been characterized by various techniques like elemental analysis, mass, absorption, IR, 1H NMR and 13C NMR spectroscopy. The complexes have been further analyzed by thermogravimetric analysis (TGA), conductance measurement and energy-dispersive X-ray spectroscopy (EDX). Interaction between compounds and herring sperm DNA has been studied by absorption titration, viscosity measurement, ethidium bromide displacement titration, and molecular docking study. The binding strength between compounds and DNA has been checked in terms of Kb, Ksv, and Kf values; while spontaneity of interaction has been checked by evaluating thermodynamic parameters like Gibb’s free energy, enthalpy change (∆H°) and entropy change (∆S°). The plasmid cleavage efficacy of complexes has been evaluated by gel electrophoresis technique. The minimum inhibitory concentration of compounds has been evaluated against pathogens such as Staphylococcus aureus, Escherichia coli, B. subtilis, S. marcescens and Pseudomonas aeruginosa. The in vivo and in vitro cytotoxic activity has been performed using cell viability assay and brine shrimp lethality bioassay.