Synthesis, spectroscopic characterization, molecular studies, and biological evaluation of (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide and some of its transition metal complexes

Novel Ni(II), Cu(II), Zn(II), Cd(II), and Pd(II) complexes (1–6) with (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide ligand (HL) were prepared and characterized via different analytical and spectroscopic techniques. The spectral data showed that the ligand is bound with copper(II) chloride, zinc(II) chloride, cadmium(II) chloride, and potassium tetrachloropalladate(II) in its neutral thione form in complexes 2, 4, 5, and 6, respectively. Furthermore, the ligand was coordinated with nickel (II) chloride and copper(II) acetate in complexes 1 and 3 as a monobasic tridentate in its thiol form. Thermogravimetric studies were performed for the prepared compounds and the pyrolytic mechanism was proposed for some complexes. DFT, TD-DFT, and NBO calculations were achieved at the B3LYP/LanL2DZ level of theory. Computational studies showed that the investigated compounds have high hyperpolarizability values (β) suggesting their potential use in the creation of non-linear optical materials. Many bacterial and fungal strains were used to assess the ligand and its metal complexes' antibacterial activities. In general, metal complexes have been shown to possess a stronger antibacterial and antifungal effect than the free ligand. Complex 5 exhibited respectable antibacterial activity versus Gram-positive bacteria. Furthermore, Zn(II) and Cd(II), complexes 4 and 5 have shown excellent activity against Gram-negative bacteria. Complex 4 exhibited a superior antifungal activity against two types of tested fungi compared with other compounds and standard Ketoconazole. Molecular docking of the ligand and its complexes 1, 2, and 5 were performed against tyrosyl-tRNA synthetase. The more negative values of the binding energy indicate that complexes 1 and 5 have higher inhibition efficiency than the free ligand.