Syntheses And Properties Of Coordination Polymers Based On Flexible Bis(triazole) Ligands

The research focus and direction of coordination polymers as functional materials has transformed from the synthesis and structure characterizations to function, which is mainly embodied in two aspects:study the relationship of structures and properties and explore advanced crystalline metal-organic materials with more superior properties. Employment of the principle and method of crystal engineering can realize the modification and assembling of the metal-organic architectures, which is beneficial to obtain novel topological frameworks with special functions. So it becomes one of the development trends of modern coordination chemisty, which attracts much interest of chemists. At present, how to get the crystalline materials with espected structures and excellent properties is the core task in crystal engineering. It demonstrates that choosing and designing suitable building blocks should be the key factor in constructing the target products. In this paper, with the aim of preparing novel metal-organic materials with intriguing structures and good properties, we select two flexible bis(triazole) ligands as building blocks, and obtain 32 new coordination polymers under the specific transition metal ions and auxiliary polycarboxylate ligands. The coordination behavior of the ligands, synthetic conditions, rules and the topological types has been discussed. In addition, we explore the relationships between the structures and properties.This work includes the following four parts:1. The combination of a long flexible ligand 4.4'-bis(l,2,4-triazol-l-ylmethyl)biphenyl (btmb) and auxiliary polycarboxylate ligands in the presence of metal ions affords six three-dimensional (3D) coordination polymers under hydrothermal conditions. Complex 1 presents a 6-connected self-penetrating mab framework, which indicates that the existence of the long flexible ligand btmb favors the formation of peculiar motifs. The effect of pH values, metal ions on the structures of complexes was analysed. Furthermore, the relationship between structures and catalytic properties was also discussed, and a plausible reaction mechanism for the present oxidative coupling reaction was proposed.2. Six novel Cd(II) coordination polymers have been synthesized by the reactions of btmb with Cd(II) salts in the presence of different anions (I-, NO3-, NCS-, CH3COO- or Cl-) under appropriate reaction conditions. These complexes exhibit one-dimensional (1D), two-dimensional (2D) structures. We have made a comparison of conformation of btmb in these Cd(II) polymers, and discussed the influence of inorganic anions on the structures and photoluminescent properties of complexes.3. Under hydrothermal conditions, the mixed ligands of l,4-bis(l,2,4-triazol-l-ylmethyl)-2,3,5,6-tetramethylbenzene (btmx) with different polycarboxylate ligands in the presence of Zn(II) or Cd(II) ions give six Zn(II) coordination polymers and four Cd(II) coordination polymers. The results reveal that polycarboxylate ligands have a great influence on the architectures of coordination polymers and can be used as a tool to tune structures. Besides, complexes 15 and 19, 17 and 20 contain the same main ligand and auxiliary ligand but different metal ions, respectively, which finally lead to the different structures, indicating the structures of complexes can be modulated by the kinds of metal ions. These complexes display good thermal stability and intense fluorescence, which shows that they can be used as potential flourescent materials.4. In order to enrich the coordination chemistry of ligand btmx, the reactions of ligand btmx and Cu(II) or Co(II) ions with the help of polycarboxylate ligands afford six Cu(II) coordination polymers and four Co(II) coordination polymers. We investigate the catalytic properties of two different Cu(II) complexes with the same raw materials, and discuss the influence of structures on the catalytic properties.