effects on solvent-free epoxidation catalyzed by dioxomolybdenum(VI) complexes supported by ONO Schiff base ligands, Inorganica Chimica Acta (2015), doi: http://dx. AbstractMolybdenum complexes of type [MoO 2 L] n (L= tridentate ONO Schiff base ligands based on the salicylidene-2-aminophenolato structure) have been synthesized and used as catalysts for the solvent-free epoxidation of olefins. The effect of donor (diethylamino) and/or acceptor (nitro) substituents has been studied. 2 Graphical abstract Highlights • Synthesis and characterization of substituted tridentate Schiff-base dioxomolybdenum complexes • These [MoO 2 L] 2 complexes are active epoxidation catalysts • Analysis of the molecular structures • Electronic effect of donor and acceptor substituents on the catalytic activity Keywords molybdenum / tridentate Schiff-base ligands / epoxidation / organic solvent-free / catalysis 3