Syntheses, Structures, and Photoluminescence of Five New Metal-Organic Frameworks Based on Flexible Tetrapyridines and Aromatic Polycarboxylate Acids

Solvothermal reactions of tetrakis(4-pyridyloxymethylene)methane (TPOM) with deprotonated 1,4-benzenedi-carboxylate (H(2)bdc) or 5-hydroxyisophthalic acid (5-OH-H(2)bdc) in the presence of nitrates of cadmium, zinc, and cobalt in H2O or H2O/DMF produced five new complexes, namely, {[Cd-2(TPOM)(bdc)(2)]center dot(H2O)(5)(DMF)}(n) (1), {[Zn-2(TPOM)(bdc)(2)]center dot(H2O)(4)}(n) (2), {[Zn-2(TPOM)(bdc)(2)]center dot(H2O)}(n) (3), {[Co-2(TPOM)(5-OH-bdc)(2)(H2O)(2)]center dot(H2O)5}(n) (4), and {[Cd-2(TPOM)(5-OH-bdc)(2)]center dot(H2O)(2)}(n) (5). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 reveals a 2-fold interpenetrating three-dimensional (3D) framework with pcu topology constructed from binuclear Cd clusters and TPOM ligands. In addition, the experiment of single-crystal-to-single-crystal (SC-SC) structural transformations upon guest exchange was tested. Zn complexes 2 and 3 possess different 3D frameworks and are prepared from TPOM and H2bdc under different reaction conditions. In complexes 4 and 5, TPOM and 5-OH-H(2)bdc link Co or Cd centers to generate 3D interpenetrating frameworks with bbf and qtz topology. In addition, thermal stabilities and photochemical properties of these new complexes in the solid state have been studied.