Dioxomolybdenum (VI) and oxomolybdenum (IV) complexes with N, O, and S bidentate ligands, syntheses, spectral characterization, and DFT studies

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Two dioxomolybdenum (VI) complexes with the chemical formula [MoO2(acac)(HPY)], [MoO2(DTO)(HPY)], and oxomolybdenum (IV) complexes [MoO(acac)(HPY)], [MoO(DTO)(HPY)] have been prepared and characterized by different spectral techniques such as (FTIR, UV-Vis., Mass, 1H NMR) spectra, magnetic susceptibility, and theoretical studies. The ligands used in this study were acetylacetone, 2-hydrazinopyridine, and dithiooximid. The spectroscopic data and the theoretical calculations suggested distorted octahedral structures for the dioxomolybdenum(VI) complexes. The dioxomolybdenum(VI) complexes were diamagnetic. The oxomolybdenum(IV) complexes are paramagnetic and have distorted square pyramidal structures. Theoretical calculations of the free ligands and the prepared complexes have been done by using DFT calculations using (G 09 W) software. The complexes were very stable and their energies ranged from (−708.85 to −921.99 a.u.) whereas the free (HPY) and (DTO) ligands were (−359.06 and −984.54 a.u.), respectively. The prepared complexes are polar (8.11–10.80 Debye) for Mo(VI), and (6.63–13.72 Debye) for Mo(IV). The HOMO orbital energies of the Mo(VI) complexes are (−0.229, and −0.377 a.u.), respectively whereas for the Mo(IV) complexes are (−0.192, −0.318 a.u.), respectively while for the (HPY) and (DTO) ligands are (−0.216, −0.262 a.u.). The LUMO orbitals energies of the Mo(VI) complexes are (−0.124, and −0.247 a.u.) and for the Mo(IV) are (−0.093, −0.208 a.u.), respectively.