Three-Dimensional Architectures Based on Lanthanide-Substituted Double-Keggin-Type Polyoxometalates and Lanthanide Cations or Lanthanide-Organic Complexes

A family of three-dimensional (3D) architectures based on lanthanide-substituted polyoxometaloborate building blocks, [LnK(H2O)12][Ln(H2O)6]2[(H2O)4LnBW11O39H]2·20H2O (Ln = Ce 1, Nd 2), H2K2(H2O) n [(C6NO2H5)Ln(H2O)5]2[(H2O)4LnBW11O39H]2·18H2O (Ln = Ce n = 8 3, Nd n = 9 4, C6NO2H5 = pyridine-4-carboxylic acid), have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, powder X-ray diffraction and single crystal X-ray diffraction. Compounds 1 and 2 are isostructural, and are built up of lanthanide-substituted double-Keggin-type polyoxoanions [{(H2O)4Ln(BW11O39H)}2]10− linked by Ln3+ cations to form a 3D open framework with one-dimensional (1D) channels. The polyoxoanion [{(H2O)4Ln(BW11O39H)}2]10− consists of two α1-type mono-Ln-substituted Keggin anions, constituted by two [BW11O39H]8− polyoxoanions and two lanthanide cations. When pyridine-4-carboxylic acid ligand was added to the reaction system of 1, 2, compounds 3, 4 were obtained. Isostructural compounds 3 and 4 are constructed from the lanthanide-substituted double-Keggin-type polyoxoanions [{(H2O)4Ln(BW11O39H)}2]10− linked by the [Ln(C6NO2H5)]3+ bridges to form a 3D channel framework. From the topological point of view, the 3D nets of compounds 1−4 are binodal with three- and six-connected nodes and exhibit a rutile topology. Compounds 1−4 represent the examples of 3D architectures based on lanthanide-substituted polyoxometalates. The magnetic properties of compounds 1−4 have been studied by measuring their magnetic susceptibility in the temperature range 2−300 K.