Synthesis, characterization, non-linear optical and DNA binding properties of a Schiff base ligand and its Cu(II) and Zn(II) complexes

Abstract

In this work, a new Schiff base ligand (HL) derived from p-isopropylaniline and 2,3,4-trihydroxybenzaldeyhde and its Cu(II) and Zn(II) complexes [ML2] were synthesized. The structures of the synthesized compounds were characterized by elemental analysis, FT-IR, 1H/13C NMR (for ligand and Zn(II) complex) spectroscopies. The crystal structure of the ligand was determined by single crystal XRD study. The XRD data showed that the ligand favours the keto-amine tautomeric form in the crystalline state. The ligand molecules are linked by OH····O hydrogen bonds forming hydrogen bonded chains. The compounds were screed for their DNA binding properties using UV–Vis spectroscopic measurements. The ligand and its Cu(II) and Zn(II) complexes showed considerable binding affinities to DNA with comparable binding constants to the ethidium bromide. Furthermore, ethidium bromide replacement properties of the compounds were investigated by photoluminescence studies. The type of interactions, binding modes and binding energies of the compounds with fish-sperm DNA were investigated by Docking studies. Moreover, computational studies were performed to examine the enol and keto tautomerism of the ligand HL using B3LYP/6–31G(d) level. Nonlinear optic properties of the compounds were investigated by computational studies.