Ligational behavior of bidentate nitrogen-oxygen donor 8-quinolinolazodye toward Ni2+ and Zn2+ ions: Preparation, spectral, thermal, experimental, theoretical, and docking studies

The 5-(4-aryl azo)-8-hydroxyquinolines (L1-L3) and their metal complexes with Ni2+ and Zn2+ have been produced. Various spectroscopic techniques have been employed to analyze the ligand and complexes. The structures of the prepared compounds have been confirmed by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (H-1 NMR), molar conductance, magnetic measurements, thermal gravimetric and differential thermal analyses (TG and DTA), and electronic transition. The FT-IR spectra showed that the ligands are coordinated to the metal ions in a bidentate manner with donor sites of the azomethine-N and phenolic-OH. The FT-IR and UV-Visible spectra were compared with the calculated results and showed a good agreement. The mass spectra concluded that the ligands' molecular weights and the calculated estimated m/z values match well. The complexes contain coordinated and hydrated water as confirmed by the TG results. The complexes are tetrahedral, trigonal bipyramid, and octahedral geometrical structures and act as non-electrolytes in dimethylformamide (DMF) solvent. Using density functional theory (DFT) at the B3LYP level of theory and the 6-311G** basis set for the C, H, N, Cl, and O atoms and the LANL2DZ basis set for the Ni and Zn atoms. Natural bond orbital (NBO) analysis was used to compute and describe the natural charge population and precise electronic configuration. The small energy gap between HOMO and LUMO energies suggests that charge transfer occurs within Ni2+ and Zn2+ complexes. The first-order hyperpolarizability (beta) of the complexes and the anisotropy of polarizability (alpha) values show promising optical properties. The electronic transitions of the prepared complexes were computed by time-dependent density functional theory (TD-DFT/PCM) with the B3LYP method using a 6-31G** basis set. The ethanol polarizable continuum model (PCM) was used to simulate the solvent effect. Utilizing a computer virtual screening technique through molecular docking, the anticipation of binding of 8-quinolinolazodye derivatives and their complexes with human CORONA virus protein (PDB ID: 5epw) was done.