Palladium(II) complexes with thioether containing azophenol ligands: Synthesis, characterization, X-ray structure and DNA binding study

Abstract The new palladium(II) complexes [Pd(L 1 /L 2 )Cl] ( 1 / 2 ), with ONS donor azo-thioether ligands (HL 1 /HL 2 ), have been successfully synthesized. The complexes were thoroughly characterized by several spectroscopic techniques. The distorted square planar geometries of the complexes were confirmed by single crystal X-ray analysis. The electronic structures, redox and spectral properties are interpreted by DFT and TDDFT calculations. The interaction of the complexes with CT DNA was investigated by the UV–Vis method and the binding constant was found to be 3.56 × 10 4  M −1 for 1 and 5.72 × 10 4  M −1 for 2 . A competitive binding titration with ethidium bromide (EB) by the fluorescence titration method revealed that the complexes efficiently displace EB from the EB–DNA system and the Stern–Volmer dynamic quenching constant, K sv , was found to be 1.28 × 10 4  M −1 and 2.04 × 10 4  M −1 for 1 and 2 respectively.