Cu(II), Ni(II), and Co(II) Complexes of a Novel Quinolinyl Hydrazone Ligand: Synthesis, Characterization, DFT, Antitumor, and Molecular Docking Studies

Abstract

A novel quinolinyl hydrazone ligand (NaphHQino) has been synthesized by condensation of 2-hydrazinyl-4,7-dimethylquinoline with 2-hydroxy-1-naphthaldehyde. Reactions of NaphHQino with copper(II), nickel(II), and cobalt(II)-chlorides yielded a series of novel complexes. Structures of the NaphHQino ligand, Cu-NaphHQino, Ni-NaphHQino, and Co-NaphHQino complexes have been inspected with the help of elemental and thermal analyses, magnetic susceptibility and molar conductivity measurements, infrared, electron spin resonance (ESR), proton nuclear magnetic resonance (¹H NMR), mass, and electronic spectra. The studied NaphHQino ligand acts either as a neutral NN-donor or as a dibasic tridentate NNO-donor, forming square-planar complexes. Molar conductivity measurements demonstrate a neutral character of the NaphHQino complexes. The ESR spectrum of the Cu-NaphHQino complex confirmed the proposed square-planar geometry with values of α² and β², demonstrating that the in-plane π-bonding character is less prominent than the covalent in-plane σ-bonding character. Implementing density functional theory at the B3LYP/6-311G(d,p) and LanL2dz levels, the molecular fundamental properties of NaphHQino and NaphHQino-complexes were assessed. NaphHQino ligand exhibited antineoplastic activity towards Ehrlich ascites carcinoma, and metal-NaphHQino complexes showed higher activity than NaphHQino. Molecular docking simulations were carried out, which supported the obtained results for antineoplastic activity.