Novel Metallomesogens Derived from Heterocycles

  • Lai, Chung-Kung (PI)

Project Details


This two-year proposal continues our original research in generating metallomesogenicmaterials derived from five- and six-membered heterocycles. This research is to propose astrategic approach for the formation of novel metallomesogens with superstructures, whichare expected to exhibit liquid crystalline behavior, magnetic and related electro-opticalproperties. These materials are associated with unique molecular assemblies in which metalcenters as core group have geometries of square plane or pyramid with a coordinationnumber of 4 and 5. Five different types of heterocyclic structures are applied to generate themetallomesogenic materials; (a) pyrazoles/isoxazoles (b) benzoxazoles (c), 1,2,4-triazzoles,and (d) 1,3,4-oxadiazes/1,3,4-thiadiazoles.A variety of transition metals will be incorporated to induce the microscopic dipole,and the choice of the metals incorporated will be focused on their preferred coordinationgeometry, oxidation state or electronic state of the metal ions. Metal complexesincorporated with a twisted square planar (Cu2+), square planar structure (Ni2+/Pd2+) areoften easily to form mesophases, however, complexes with a tetrahedron (Co2+/Zn2+) isnot easy to form a mesophase due to a 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 togenerate the proposed metal complexes. Occasionally, complexes with a CN = 3 (Cu1+/Ag1+)might be also possible. A noncentrosymmetric structure and the large resulting moleculardipoles are prerequisites in order to give rise to large bulk macroscopic polarization. Theability to reorient the polarization with electric field applied and to have this polarizationpersist after the field is removed will make these materials polar ordering.A major distinction between metallomesogens and organic mesogens is their greatertendency to exhibit intermolecular dative coordination in the mesophase, which makesthese materials attractive candidates for poling into acentric states. In these systems a lowersymmetry is promoted at the molecular level by the self-ordering properties of liquidcrystalline materials, the complementary shape of the molecules and head-to-tail orderingimposed by the linear chain superstructures, and these methods are also widely employed tofacilitate the formation of these mesogenic materials. Self-organizing properties of liquidcrystalline materials, the geometric shape of the molecules, and weak intermolecular dativecoordination will be employed to facilitate the formation of the proposed materials.Preparation, characterization and mesomorphic properties of these poly-metalliccompounds will be studied in the initial stage, and future research will be focused on thephysical studies.
Effective start/end date1/08/1631/07/17

UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):

  • SDG 2 - Zero Hunger
  • SDG 12 - Responsible Consumption and Production
  • SDG 17 - Partnerships for the Goals


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