Othman I. AlajrawyAyad A. Almhmdi2025-02-162022ALAJRAWY, Othman I.; ALMHMDI, Ayad A. Dioxomolybdenum (VI) and oxomolybdenum (IV) complexes with N, O, and S bidentate ligands, syntheses, spectral characterization, and DFT studies. Journal of Molecular Structure, 2022, 1260: 132813.‏https://doi.org/10.1016/j.molstruc.2022.132813https://ds.uofallujah.edu.iq/handle/123456789/432Dioxomolybdenum (VI) and oxomolybdenum (IV) complexes with N, O, and S bidentate ligands are coordination compounds where molybdenum is coordinated to bidentate ligands that include donor atoms like nitrogen, oxygen, and sulfur. These complexes are synthesized by reacting molybdenum precursors with the corresponding ligands under controlled conditions. Their structures and bonding are characterized using spectral techniques like UV-Vis, IR, NMR, and X-ray crystallography. Density Functional Theory (DFT) studies are employed to analyze electronic properties, optimize structures, and predict reactivity and stability of these complexes.Two dioxomolybdenum (VI) complexes with the chemical formula [MoO 2 (acac)(HPY)], [MoO 2 (DTO)(HPY)], and oxomolybdenum (IV) complexes [MoO(acac)(HPY)], [MoO(DTO)(HPY)] have been prepared and char- acterized by different spectral techniques such as (FTIR, UV-Vis., Mass, 1 H NMR) spectra, magnetic suscep- tibility, 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 diamag- netic. The oxomolybdenum(IV) complexes are paramagnetic and have distorted square pyramidal struc- tures. 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.enMolybdenum(IV) complexes Molybdenum(VI) complexes 2- hydrazinopyridine Dithiooxamide Spectroscopic Theoretical calculationsArticle