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

A novel series of transition metal complexes of Cu(II) and Zn(II), including: [Cu(L-1)(2)]: Cl, [Cu(L-2)(2)]: C2, [Cu(L-3)(2)]: C3, [Cu(L-4)(2)]: C4, [Zn(L-1)(2)]: Z1, [Zn (L-2)(2)]: Z2, [Zn (L-3)(2)]: Z3, and [Zn (L-4)(2)]: Z4, with four halogenated bis-N,O-bidentate Schiff base ligands (HL1: 2-ethoxy-6-[(4-fluorophenyl)iminomethyl]phenol; HL2: 2-ethoxy-6-[(4-chlorophenylimino)methyl]phenol; HL3: 2-ethoxy-6-[(4-bromophenyl)iminomethyl]phenol; HL4: 2-ethoxy-6-[(4-iodophenylimino)methyl]phenol have been synthesized and characterized by elemental analyses, FT-IR, UV-Vis and H-1 NMR spectroscopic techniques. Furthermore, the crystal structures of HL2, HL4, Z1 and Z2 were determined by single crystal X-ray analysis. These bidentate ligands coordinated to the metal(II) ions through the deprotonated phenolic oxygens and the azomethine nitrogens. The X-ray diffraction analysis revealed that Z1 and Z2 adapted distorted tetrahedral geometries. Theoretical calculation of the synthesized compounds, carried out by DFT as well as TD-DFT using B3LYP method with employing the Def2-TZVP basis set, indicated that the calculated results are in accordance with the experimental findings. NBO analysis has been used to elucidate charge transfer information of the HL2, HL4, Z1 and Z2. Moreover, binding ability of the Schiff base ligands and their metal complexes with FS-DNA was studied by spectroscopic and computational methods. The results of both methods showed that the ligands bound in minor grooves of DNA. The oxygen of the ethoxy group has played an important role in DNA binding investigations. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A novel series of transition metal complexes of Cu(II) and Zn(II) with halogenated bis-N,O-bidentate Schiff base ligands have been synthesized and characterized. The crystal structures of some compounds were determined by X-ray analysis, and theoretical calculations using DFT methods confirmed the experimental findings. The binding ability of the ligands and metal complexes with DNA was studied through spectroscopic and computational methods, showing binding in DNA's minor grooves.