Liquid Crystalline Properties and Nanostructures Growth of Imidazole and 1,2,4-triazole Metal Complexes.

• Main Authors: Shih-Jen Hsu, 許世仁
• Other Authors: Ivan J.B. Lin
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/5e7be5

博士 === 國立東華大學 === 化學系 === 96 === chapter 1 Abstract: Three series of Au(I)-imidazole complexes with stoichiometries of [Au(Cn-bim)Cl], [Au(Cn-im)Cl], and [Au(Cn-im)2][NO3]･2H2O (Cn-bim = N-CnH2n+1-substituted benzimidazole and Cn-im = N-CnH2n+1-substituted imidazole) together with the compound of [Au(C18-bim)2][NO3] are synthesiszed. Typical structures of each series are determined by single crystal X-ray diffraction. The last series of compounds, are liquid crystals, and exhibit wider mesophase range than their Ag(I) analogues. These Au(I) complexes form Au nanostructures both through chemical reduction or thermolysis. For the first time, N-long chain imidazole is utilized to stabilize colloidal Au in solution. Also for the first time, the unique examples of simple thermolysis to produce large Au plates with nanothickness are demonstrated. Formation of plate-like morphology through fusion of sphere-like nanoparticles at an early stage is evidenced by the images of TEM. chapter 2 Abstract: Ag(I) complexes of 1,2,4-triazole derivatives of different ligand to Ag(I) ratios, when 1-alkyl-1,2,4-triazoles (1-Cn-Taz, Cn = CnH2n+1) are employed, [Ag(1-Cn-Taz)2][NO3] (n = 18, 16, 14, 12, 10, and 8), with two 1- Cn-Taz ligands coordinating to a silver metal ion are metal containing ionic liquid crystals. When 4-alkyl-1,2,4-triazoles (4-Cn-Taz, Cn = CnH2n+1) are used [Ag(4-Cn-Taz)]NO3 (n = 18, 16, 14, and 12), in which 4- Cn-Taz behaves as a bridging ligand, forms polymeric metal containing ionic liquid crystals; analogous compounds [Ag(4-Cn-Taz)]BF4 and [Ag(4-Cn-Taz)]PF6 are not liquid crystals. chapter 4 Abstract Micron-sized gold nanosheets were produced through thermolysis of a mixture composed of 1-octadecanylimidazole (C18-im) and HAuCl4 in a molar ratio of 4:1 at 200 oC for 1 h. Effects of the molar ratio of [C18-im]/[HAuCl4], the reaction temperature, and the N-alkylimidazole chain length were studied. Adjusting the molar ratio of [C18-im]/[HAuCl4] can tune the morphology and size of the nanostructures; the effect of reaction temperature is minimum; while using long chain imidazole tends to favor the formation of nanosheets, using 1-methylimidazole (C1-im) produces micron-sized polyhedra. The growth mechanism of these nanostructures was proposed. C18-im functions both as a templating and capping agent and favors the growth of nanosheets. On the other hand, C1-im functions only as a capping agent and thus favors the formation of polyhedra, especially octahedra. chapter 5 Abstract A one pot method to fabricate gold crystals through thermolysis of mixtures of N-alkylimidazole, HAuCl4, and AgNO3 is described. The preferential growths of Au crystals are dependent on N-alkylimidazole chain length and mixture concentration. For the first time, two series of morphology transitions of Au crystals are observed. Thermolysis of mixtures of N-octadecanylimidazole (C18-im), HAuCl4, and AgNO3 yields Au platelets, octahedrons, cuboctahedrons, and cubes. On the other hand, thermolysis of mixtures of N-methyl-imidazole (C1-im), HAuCl4, and AgNO3, unusual transformation of Oh symmetric Au crystals from octahedron via edge-truncated octahedron (octahedron dominant and dodecahedron dominant) to rhombic dodecahedron and even tetrahexahedron occurs. Our laboratory synthesis of two Au crystals previously found in nature, octahedron truncated at edges and tetrahexahedron (THH), are unprecedented. This thus accounts for the different morphology transformations of Au crystals with low-index surfaces.