Manganese (III) oxide inserted into silica reveals to be a catalyst

Two new structural and functional models of the Mn-catalase, were synthesized and characterized by X-ray diffraction. The magnetic properties of these compounds reveal a weak antiferromagnetic behavior. This fact, together with the nearly orthogonal orientation of the Jahn–Teller axes of the Mn^III ions explain the unusual shape of χ_MT versus T plot at low temperature.

One of these compound presents a better catalase activity than the other because of an interaction of the nitrate counter anion and the solvent. These compounds were successfully inserted inside two-dimensional hexagonal mesoporous silica leading to the same hybrid material ([Mn₂O]@SiO₂).

The manganese complex occupies approximately half of the available pore volume, keeping the silica’s hexagonal array intact. Magnetic measurements of [Mn₂O]@SiO₂ suggest that most of the dinuclear unit is preserved, as a non-negligible interaction between Mn ions is still observed. The X-ray photoelectron spectroscopy analysis confirms that Mn remains as Mn^III inside the silica. The catalase activity study of material [Mn₂O]@SiO₂ reveals that the complex is more active inside the porous silica, probably due to the surface silanolate groups of the pore wall. Moreover, the new material shows catalase activity in water media, while the coordination compounds are not active.