Metal-organic frameworks assembled from lanthanide and 2,5-pyridinedicaboxylate with cubane-like [Ln4(OH)4] building units

Lanthanide-organic frameworks based on 2,5-pyridinedicaboxylate (25p) ligand, formulated as [Yb-4(OH)(4)(25p)(4)(H2O)(3)]center dot H2O (25pYb), [Y-4(OH)(4)(25p)(4)(H2O)(3)]center dot H2O (25pY-1) and [Y-6(OH)(8)(25p)(5)(H2O)(2)] (25pY-2), have been obtained as single phases under hydrothermal conditions. 25pYb and 25pY-1 are isostructural, and crystallize in the triclinic space group, P-1, with a=8.6075(5) angstrom, b=14.8478(7) angstrom, c=15.9164(9) angstrom, alpha=86.277(4)degrees, beta=80.196(5)degrees, gamma=81.785(4)degrees, and a=8.7166(6) angstrom, b=14.966(1) angstrom, c=15.966(1) angstrom, alpha=86.260(6)degrees, beta=80.036(6)degrees, gamma=81.599(6)degrees, respectively. 25pY-2 crystallizes in the monoclinic space group, P2(1)/c, with a=24.9117(17) angstrom, b=13.7340(8) angstrom, c=14.3385(10) angstrom, beta=100.551(7)degrees. 25pYb and 25pY-2 have been structurally characterized by single-crystal X-ray diffraction. The 25pYb structure is based on tetranuclear cubane-like [Yb-4(OH)(4)](8+) clusters, which are interconnected to eight neighbouring clusters through teen surrounding 25p ligands leading to neutral 3D framework, while the structure of 25pY-2 is based on two independent cuban-like [Y-4(OH)(4)](8+) clusters, which are joined together through Y1 cation leading to the formation of hexanuclear [Y-6(OH)(8)](10+) clusters, which in turn are joined via Y2 cation resulting in infinite inorganic chain extending along c-axis, and each chain is interconnected to six adjacent chains through 25p ligands leading finally to 3D framework. The luminescence properties of Eu3+ and Tb3+ doped 25pY-1 and 25pY-2 compounds have also been investigated. All materials has been characterized by powder X-ray diffraction, thermal analyses (TG-SDTA-MS), FTIR spectroscopy, C-H-N elemental analysis, scanning electron microscopy (SEM-EDX), and powder X-ray thermodiffraction. (C) 2015 Elsevier Inc. All rights reserved.