Synthesis, structure and properties of three-dimensional organic–inorganic hybrids based on α-metatungstate

Four new organic–inorganic hybrids with three-dimensional (3D) framework based on the α-metatungstate clusters [H2W12O40]6−, (NH4)2[Ln2(L)2(H2W12O40)(H2O)7]·nH2O (Ln = CeIII (1), n = 9; PrIII (2), n = 12; NdIII (3), n = 11; SmIII (4), n = 10; L = 2-pyrazinecarboxylate), have been conventionally synthesized and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra and thermal gravimetric analyses. Single-crystal X-ray diffraction analyses reveal these compounds are isostructural with a P2(1)/c space group. And L ligand connects two kinds of Ln3+ ions in a tridentate chelating-bridging coordination mode, resulting in two sorts of infinite one-dimensional (1D) zigzag chains. [H2W12O40]6− cluster acting as a pentadentate linker connects five Ln3+ ions from three zigzag chains through its five terminal oxygen atoms, forming a complicated 3D framework structure with a novel (32415261)(32425363)(3143536172) topology. In compounds 1–4, there exist S-type channels with maximum length of ca. 12.563 Å and minimum length of ca. 3.888 Å along the a-axis direction. In addition, solid-state luminescence properties of compounds 1, 2, 4 and 2-pyrazinecarboxylic acid (HL) have been studied at room temperature.