The new compounds Pyridoxal N-allyl-S-methylthiosemicarbazone (L) and the dioxomolybdenum(VI) complex [MoO2(L)CH3OH] have been synthesized and characterized by elemental analysis, UV-Vis, FT-IR, Raman and H-1 NMR spectra, and also by the single crystal X-ray diffraction technique. Single crystals of the cis-dioxomolybdenum(VI) complex were obtained by evaporating its methanol solution. According to the single-crystal X-ray diffraction investigation, the molybdenum atom in the complex is in a distorted octahedral coordination. The sixth coordination site is occupied by the oxygen atom of a methanol solvent molecule. The methanol coordination between the oxygen and molybdenum atoms is the weakest bond, with a Mo-O bond length of 2.355 angstrom. The geometries and vibrational spectra of the pyridoxal thiosemicarbazone (L) and its complex are explained by quantum chemical calculations. (C) 2020 Elsevier Ltd. All rights reserved.