New molybdenum(VI) and vanadium(IV) complexes with 3-aminopyridine and dithiooxamide ligands spectroscopic characterization, DFT calculations, and in vitro cytotoxic activity

Two molybdenum(VI) complexes C1, [MoO2(acac)(APY)] and C2, [MoO2(DTO)(APY)]·H2O, and two vanadium (IV) complexes C3, [VO(H2O)3(APY)]SO4·3/2H2O and C4, [VO(DTO)(H2O)(APY)]SO4, (where APY = 3-aminopyridine, acac = acetylacetone, and DTO = dithiooximide). The complexes were characterized by different spectral techniques such as FTIR, UV–Vis., 1H NMR, mass spectroscopy, and theoretical calculations. The FTIR spectra showed that the (APY) ligand was coordinated by the nitrogen atom of the amine group. The DTO ligand coordinated in different ways depending on the central metal by the two nitrogen atoms with vanadium V(IV), and by the two sulfur atoms with the molybdenum(VI). The mass spectra confirmed the mononuclear structure for all the prepared complexes. The Mo(VI) complexes were diamagnetic, whereas the V(IV) complexes were paramagnetic. The calculations revealed that the prepared complexes were more stable than the free ligands and their HOMOs were (−0.373 and −0.347 a.u.) for molybdenum(VI) complexes and (−0.502 and −0.496) for vanadyl complexes; respectively whereas the LUMOs values were (−0.282 and −0.289 a.u.) for molybdenum(VI) complexes and (−0.418 and −0.429 a.u.) for vanadium(IV) complexes. The complexes were more polarized and softer than the free ligands. The results confirmed that the transition of the electrons is easier in the complexes than the ligands which suggest using the prepared complexes in the photocell in future studies. Based on the obtained experimental and calculated data, distorted pyramidal structures for the V(IV) and Mo(VI) complexes were proposed. The prepared complexes were examined as anti-cancer complexes against different types of cell lines, the cytotoxic activity of the complexes data showed that the C2 complex is the best candidate to be used as an anti-cancer drug.