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 ( 1 H 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 α 2 and β 2 , 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.