Heterodinuclear Cu–Gd (3d-4f) complex with di-compartmental Schiff base ligand in biological activity: Synthesis, crystal structure, catecholase activity and DNA & BSA-binding studies

Abstract

A dinuclear CuII-GdIII Schiff base complex (a di-compartmental Schiff base ligand derived from o-vanillin) nominated as: 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol) (H2valpn) was synthesized in two steps. To characterize the compounds, single-crystal X-ray crystallography, UV–Vis spectroscopy, IR spectroscopy, and elemental analyses were used. The crystalline sample of the heterodinuclear complex revealed the structure of general formula [(valpn) (H2O) CuII GdIII (NO3)3], with the copper ion located in a square pyramidal section (with an axial aqua ligand) and the gadolinium (III) ion located in the open compartment, in which 10 oxygen atoms from three chelating nitrate ions and a Schiff base ligand surrounded it. To study the applications of the complex, the binding affinity of the complex with FS-DNA was studied by UV–Vis spectroscopy, fluorescence spectroscopy, viscosity measurements, cyclic voltammetry (CV) and circular dichroism (CD). From all of these methods, intercalation was suggested as the main mode of binding. The complex was also checked in interaction with Bovine serum albumin (BSA) by using UV–Vis and fluorescence spectroscopy. Cytotoxicity was tested by MTT assay toward HeLa, LNCaP, and MCF-7 cancer cell lines. Moreover, the docking calculation was performed and these results confirmed the experimental results. The mechanism and kinetics of the catalytic activity of the complex in the oxidation reaction of 3,5-di-tert-butylcatechol, was studied at 298 K.