Three Schiff base ligands derived from three different 1,3-diones and diethylenetriamine have been synthesized and subsequently grafted on a silica surface via covalent bonds. The organic ligands as well as the heterogenised ligands reacted with manganese(II) ions leading to the formation of the corresponding metal complexes. Supported and non-supported manganese complexes have been evaluated as catalysts for alkene epoxidation with hydrogen peroxide in the presence of ammonium acetate as an additive. Both homogeneous and heterogeneous systems are able to activate hydrogen peroxide towards epoxide formation presenting remarkable catalytic properties. This catalytic ability of the immobilised manganese complexes is further highlighted, since they present efficient systems overcoming competitive H2O2 dismutation, in conjunction with advantages of the heterogeneous catalysts. In this context, they gave high yields for limonene epoxidation, significantly higher than the corresponding homogeneous catalysts. (c) 2006 Elsevier B.V. All rights reserved.