Immobilisation of single molecule magnets in mesoporous silica hosts

Abstract

Molecular clusters [Mn₁₂O₁₂(RCOO)₁₆(H₂O)_n] (R = CH₃, C₆H₅ (n = 4) and C₂H₅ (n = 3)) and [Mn₄(CH₃COO)₂(pdmH)₆] (pdmH = 2,6-bis (hydroxymethyl)pyridine) presenting Single Molecule Magnetic (SMM) behaviour were inserted into hexagonal mesoporous silica with pore size in the 25–100 Å range. An optimum host pore size exists which maximizes the amount of embedded cluster. The composites were studied by X-ray diffraction, infrared spectroscopy, magnetic measurements, nitrogen sorption, thermogravimetric analysis and transmission electronic microscopy. All these methods reveal the presence of intact guest clusters inside the silica pores. Moreover, if the magnetic properties of the clusters appear globally unmodified by the insertion process, the absence of a magnetic isomer form of [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)₄] within silica porosity suggests an influence of the confinement on the cluster structure.