Novel copper(II) and zinc(II) complexes of halogenated bidentate N,O-donor Schiff base ligands: Synthesis, characterization, crystal structures, DNA binding, molecular docking, DFT and TD-DFT computational studies

Abstract

Eight novel complexes, including: [Cu(L1)2]: C1, [Cu(L2)2]: C2, [Cu(L3)2]: C3, [Cu(L4)2]: C4, [Zn(L1)2]: Z1, [Zn (L2)2]: Z2, [Zn (L3)2]: Z3, and [Zn (L4)2]: Z4, with four bidentate N,O-donor halogenated bis-Schiff base ligands (HL1: 4-Bromo-2-[(4-fluorophenylimino) methyl]phenol; HL2: 4-Bromo-2-[(4-chlorophenylimino)methyl]phenol; HL3: 4-Bromo-2-[(4-bromophenylimino) methyl]phenol; HL4: 4-Bromo-2-[(4- iodophenylimino)methyl]phenol) were synthesized and their structures were proved by SC-XRD, FT-IR, UV-Vis, and 1H NMR spectroscopic techniques. The single crystal X-ray diffraction analysis reveals that a distorted tetrahedral geometry is formed in zinc complex whereas a slightly distorted square planar geometry is formed in both copper(II) complexes of C3 and C4. Theoretical calculations of the complexes were carried out via DFT as well as TD-DFT using B3LYP method employing the Def2-TZVP basis set, where the calculation results are in accordance with the experimental results. NBO analysis has been used to elucidate charge transfer information of the Z1, C3 and C4 complexes. Moreover, interaction of ligands and complexes with FS-DNA was assessed using UV-Vis spectroscopy as well as molecular docking. The experimental and theoretical results reveal that the DNA-binding affinity of as-prepared complexes increases with decreasing in electronegativity of substituted halogen atom.