2,4-Dihydroxybenzaldehyde S-allylisothiosemicarbazone hydrobromide, H2L, reacts with dioxomolybdenum acetylacetonate in methanol to form a stable complex of dioxomolybdenum(VI). The ligand and complex are characterized with analytical and spectroscopic techniques. Single-crystal X-ray crystallography has been also carried out for the complex, showing it has distorted octahedral geometry. H2L is a tridentate dianionic ligand bonded as an ONN donor to molybdenum. Thermogravimetric analysis of the complex shows MoO3 as the final product above 780 °C. The results obtained from density functional theory calculations for the optimization and frequency analysis are in agreement with the experimental data. Natural bond orbital calculations show that the majority of the electron density of the donors tends to the molybdenum, since the calculated Mulliken charge for the central ion is much lesser than the formal value.

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