Syntheses, Structures And Properties Of Coordination Polymers With Dicarboxylates

Great efforts have been expended on crystal engineering of coordination polymers because of their fascinating structural diversity and potential applications in catalysis, luminescence, magnetism and porosity. The organic ligands containing two or more carboxylate groups offer great potentials for fine control over coordination architectures. However, the control of the packing of the low-dimensional motifs is still a great challenge fraught with difficulties. With this aims, dicarboxylates are used as bridging ligands between divalent transition metal ions, in combination with the use of pyridyl/macrocyclic reagents as terminal ligands or bridging ligands, twenty-four new coordination polymers, including one dimensional, two dimensional and three dimensional motifs, have been prepared, and the adsorption properties of some of the complexes have been characterized.This dissertation covers the following four parts:(1) Low dimensional coordination polymers tuned by pyridyl-type terminal ligands. Solvothermal reactions of trans-stilbene-4,4'-dicarboxylic acid (H₂STDC) and metal ions(Zn, Cd, Co, Mn) in the presence of a series of systematically varied terminal ligands (L' = pyridine, 2,2'-bipyridine, 2,2'-biquinoline, 1,10-phenanthroline) afforded ten supramolecular architectures, [M(STDC)(L')]-S. X-ray analyses revealed that the structures of these compounds consist of infinite 1D zigzag polymer chains or 2D layers, and the packing modes of the frameworks were analyzed based on the intermolecular interactions (hydrogen bonding or Ï€-Ï€ interactions). The framework stability and guest-inclusion properties of the porous complexes also have been characterized.It has been demonstrated that the terminal ligands play a critical role in the construction of the supramolecular motifs by providing interaction information for the interchain or interlayer recognition. Among the seven 1D zigzag coordination polymers, the zigzag chains are packed in parallel or propagate along two or more different directions. Most intriguingly, we found a novel type of 3D entanglement ofzizag chains in the M(STDC)(phen) frameworks (M = Zn, Cd, Co), in which the chains with four different orientations are hierarchically entangled into 3D architectures with open channels. The resulting materials show reversible and selective guest inclusion.(2) One-dimensional coordination polymers tuned by macrocyclic terminal ligands. Four macrocyclic Ni(II) complexes have been obtained by the reaction of Ni(II) ions with quadridentate macrocyclic compounds as terminal chelating ligands. From H2STDC and different macrocyclic Ni(II) complexes, six one-dimension coordination polymers have been constructed, for which the linear shape is dictated by the quadridentate macrocyclic ligands that tend to assume planar coordination. It has been shown that the packing of the linear chains depends upon the macrocyclic ligands and the synthetic conditions. It is also possible to construct porous architectures in which the chains with three different orientations are interwoven.(3) Two- and three-dimensional coordination polymers constructed from polynuclear secondary building blocks (SBUs). Solvothermal reactions of H₂STDC and Zn(II) ions, with or without co-bridging ligands afforded six new coordination polymers. In absence of co-bridging ligands, two 2D compounds with Zn₃ linear clusters as SBUs and a 3D compound with infinite Zn(COO)₂ rods as SBUs have been obtained under different conditions. Three-fold interdigitation of the 2D networks and two-fold interpenetration of the 3D networks obviate the void space within individual networks. The interconversion between the 2D and 3D structures has been demonstrated.In the presence of co-bridging ligands of different lengths [4,4'-bipyridine, 1,2-bis(4'-pyridyl)ethane, 1,3-bis(4'-pyridyl)propane], three 3D pillared-layer structures on the above 2D layers with Zn₃ SBUs have been constructed. Although 3-fold interpenetration obviate the void space within the layers, interlayer apertures may be produced by increasing the length of the cobridge, demonstrating a promising approach to porous coordination polymers.(4) Three-dimensional supramolecular network constructed from a cubicmetalloligand. A soluble cobalt(II) cubic compound has been obtained by the reaction of Co(II) ions and the multifunctional ligand imidazole-4,5-dicarboxylic acid (H₃IDC). Using the cubic cage as metalloligand, a novel 3D assembly, where mixed-valence cubes are linked by macrocyclic Ni(II) complexes through coordination and hydrogen bonds, has been constructed.