3-methoxysalicylidene N-alkyl-thiosemicarbazones (L) (where alkyl is propyl, butyl, pentyl or hexyl) were synthesized. The reaction of the ONS donor ligands with [MoO2(acac)(2)] in methanol yielded the mixed ligand complexes bearing a solvent molecule as co-ligand, [MoO2(L)MeOH)]. The ligands and complexes were characterized by using analytical and spectroscopic methods. As a representative sample, the dioxomolybdenum(VI) complex of the N-4-butyl-substituted thiosemicarbazone was crystallographically examined to ensure the expected structures. X-ray data showed a distorted octahedral environment of molybdenum center. Tyrosinase, collagenase inhibition and antioxidant properties of the compounds were investigated using spectroscopic methods. The ligand and complexes exhibited the different inhibitory activities depending on N-alkyl substituents. Similarly, also the antioxidant capacity of the compounds changed in relation to the substituents. (C) 2019 Elsevier B.V. All rights reserved.