English  |  正體中文  |  简体中文  |  Items with full text/Total items : 69937/69937 (100%)
Visitors : 23281078      Online Users : 568
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
Scope Tips:
  • please add "double quotation mark" for query phrases to get precise results
  • please goto advance search for comprehansive author search
  • Adv. Search
    HomeLoginUploadHelpAboutAdminister Goto mobile version

    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/62342

    Title: 含過渡金屬中心雜環結構之中間相材料;Metallomesogens Derived from Heterocycles
    Authors: 賴重光
    Contributors: 國立中央大學化學系
    Keywords: 化學
    Date: 2012-12-01
    Issue Date: 2014-03-17 11:30:34 (UTC+8)
    Publisher: 行政院國家科學委員會
    Abstract: 研究期間:10108~10207;This proposal continues our original research in metallomesogen derived from heterocycles. This research is to propose a strategic approach for the formation of novel metallomesogenic materials with superstructures, which are expected to exhibit liquid crystalline behavior, magnetic and related electro-optical properties. These materials are associated with unique molecular assemblies in which metal centers as core group have geometries of square planar or pyramid with a coordination number of 4, 5 and 6. Four different types of heterocyclic structures are applied to generate the metallomesogenic materials; (a) pyrazoles (b) benzoxazoles (c), 1,2,4-triazzoles, and (d) 1,3,4-oxadiazes. A variety of transition metals will be incorporated to induce the microscopic dipole, and the choice of the metals incorporated will be generally dependent on the coordination geometry, oxidation state or electronic state of the metals. Metal complexes incorporated with a twisted square planar (Cu2+), square planar structure (Ni2+/Pd2+) are often easier to form mesophases, however, complexes with a tetrahedron (Co2+/Zn2+) is not easy to form a mesophase due to unfavorable packing. A coordination number of 4 (Cu2+/Ni2+/Zn2+/Pd2+), 5 (VO2+/TiO2+/Mn2+), and 6 (Cr/3+Al/3+Ru3+/Fe3+) will be applied to generate the metal complexes. Occasionally, complexes with a CN = 3 (Cu1+/Ag1+) might be also possible. A non centrosymmetric structure and the large resulting molecular dipoles are prerequisites in order to give rise to large bulk macroscopic polarization. The ability to reorient the polarization with electric field applied and to have this polarization persist after the field is removed will make these materials polar ordering. A major distinction between metallomesogens and organic mesogens is their greater tendency to exhibit intermolecular dative coordination in the mesophase, which makes these materials attractive candidates for poling into acentric states. In these systems a lower symmetry is promoted at the molecular level by the self-ordering properties of liquid crystalline materials, the complementary shape of the molecules and head-to-tail ordering imposed by the linear chain superstructures, and these methods are also widely employed to facilitate the formation of these mesogenic materials. Self-organizing properties of liquid crystalline materials, the geometric shape of the molecules, and weak intermolecular dative coordination will be employed to facilitate the formation of the proposed materials. Preparation, characterization and mesomorphic properties of these poly-metallic compounds will be studied in the initial stage, and future research will be focused on the physical studies.
    Relation: 財團法人國家實驗研究院科技政策研究與資訊中心
    Appears in Collections:[化學學系] 研究計畫

    Files in This Item:

    File Description SizeFormat

    All items in NCUIR are protected by copyright, with all rights reserved.

    社群 sharing

    ::: Copyright National Central University. | 國立中央大學圖書館版權所有 | 收藏本站 | 設為首頁 | 最佳瀏覽畫面: 1024*768 | 建站日期:8-24-2009 :::
    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - Feedback  - 隱私權政策聲明