Slow relaxation of the magnetization in high-nuclearity Ln-complexes

By the surface modi. cation strategy, a novel high-nuclearity lanthanide complex with a discrete structure, Er26I(mu(3)-OH)(20)(mu(3)-O)(6)(NO3)(9)(IN)(33)(OH)(3)(H2O)(33) (noted Er-26, HIN = isonicotinic acid), has been prepared under hydrothermal conditions. The magnetic properties of Er26 and two analogue dysprosium assemblies Dy30I(mu(3)-OH)(24)(mu(3)-O)(6)(NO3)(9)(IN)(41)(OH)(3)(H2O)(38) (noted Dy-26-I) and Dy26I(mu(3)-OH)(20)(mu(3)-O) (6)(NO3)(9)(IN)(31.25)(OH)(4.75)(H2O)(41.75) (noted Dy-26-II) have been studied. The results show that the slow relaxation of the magnetization is newly found in Dy-26-I constructed from {Dy-26} and {Dy-4} cluster units. The {Dy-4} units in Dy-26-I, the relative orientation of the complex or the inter-molecular interactions between {Dy26} cores might play an important role in the origin of this magnetic behavior. (C) 2008 Elsevier B.V. All rights reserved.