Palladium(II) complexes with salicylaldehyde ligands: Synthesis, characterization, structure, in vitro and in silico study of the interaction with calf-thymus DNA and albumins

Abstract

The synthesis and characterization of four palladium(II) complexes with substituted salicylaldehydes (X-saloH) having the general formula [Pd(X-salo)2] was undertaken. The complexes are formulated as [Pd(3-OCH3-salo)2] 1, [Pd(5-NO2-salo)2] 2, [Pd(5-Cl-salo)2] 3, and [Pd(5-Br-salo)2] 4. The structure of complex 1 was verified by single-crystal X-ray crystallography. Spectroscopic (UV–vis), and physicochemical (viscosity measurements) techniques were employed in order to study the binding of the complexes with calf-thymus (CT) DNA, while ethidium bromide (EB) displacement studies, performed by fluorescence emission spectroscopy, revealed the ability of the complexes to displace the DNA-bound EB. Intercalation is the most possible mode of interaction of the complexes with CT DNA. The interaction of the complexes with bovine (BSA) and human (HSA) serum albumin proteins was studied by fluorescence emission spectroscopy and the relatively high binding constants revealed the reversible binding of the complexes to the albumins. Molecular docking simulations on the crystal structure of HSA, BSA and CT DNA were employed in order to study in silico the ability of the studied complexes 1–4 to bind to these target macromolecules.