Synthesis, characterization, crystal structure and DNA, HSA-binding studies of four Schiff base complexes derived from salicylaldehyde and isopropylamine

Abstract

Four new Schiff base complexes (NiL2, CoL2, CuL2 and ZnL2) (HL: ((E)-2-((isopropylamino) methyl) phenol) were synthesized and characterized by CHN elemental analysis, FT-IR and single crystal X-ray diffraction technique. The crystallographic data reveal that in all complexes the metal centers are four-coordinated by two phenolate oxygen and two imine nitrogen atoms of two moles of Schiff base ligand HL and geometry around the metal center in all of them is distorted tetrahedral. In addition, 1H and 13C NMR techniques were employed for characterization of diamagnetic ZnL2 complex. The binding affinity of complexes with DNA (fish sperm DNA, FS-DNA) and Human Serum Albumin (HSA) were investigated using fluorescence quenching, chemometrics, UV–Vis spectroscopy, viscosity measurements and molecular docking methods. The obtained results revealed that the DNA and HSA affinity for binding to complexes are in the following order: CuL2>ZnL2>CoL2>NiL2 and NiL2>ZnL2>CuL2>CoL2. The distance between complexes and HSA was obtained based on the Förster’s theory of non-radiative energy transfer. The computational molecular docking results showed that H-bond interactions, hydrophobic interactions, π-π stacking and π-cation interactions have dominant role in the stability of HSA-ML2 (M: Cu, Co, Ni and Zn). The computational docking and viscosity results suggest that all metal complexes interact with DNA presumably by the groove binding mechanism.