Mn12 single-molecule magnets incorporated into mesoporous MCM-41 silica

The incorporation of four Mn-12 derivatives, namely [Mn12O12(O2CR)(16)(H2O)(4)] (R = CH3 (1), CH3CH2 (2), C6H5 (3), C6F5 (4)), into the hexagonal channels of the MCM-41 mesoporous silica have been studied. Only the smallest clusters I and 2 that are those with compatible size with the pores of MCM-41 could be incorporated into the mesoporous silica. Powder X-ray diffraction (XRD) analysis and N-2 adsorption-desorption isotherm experiments show that the well-ordered hexagonal structure of MCM-41 is preserved and that the Mn-12 clusters are inside the pores. The magnetic properties of the MCM-41/1 nanocomposite material indicate that the structure of the cluster is maintained after incorporation into the MCM-41 walls, but some differences appear that may be attributed to partial substitution of carboxylate groups of 1 by silanol groups of the wall surface. In contrast with the pristine Mn12 derivatives calcination of the composite samples gives rise to materials with similar properties to those observed before calcination. (C) 2003 Elsevier Science Ltd. All rights reserved.