| Complexes with acentric structure may be obtained by the coordination between 1,3,5-tris(1-imidazolyl) benzene(tib) and metal ion as well as 18-crown-6 and guest molecules amine salt, because of acentric structure of three-connecting ligand tib with N donors and 18-crown-6, and controllable flexible pore space of 18-crown-6, providing some new ideas in quest of new-type ferroelectrics. The whole dissertation is divided into two parts.The first section: the hydrothermal reaction of tib and sulfate MSO4(Mn SO4, Co SO4·7H2O, Fe SO4·7H2O) lead to the formation of three new metal-organic frameworks, that is, {[Mn(tib)2(H2O)4]SO4}n(1),{[Co(tib)2(H2O)4]SO4}n(2) and {[Fe(tib)2/3(H2O)4]SO4}n(3)(Chapter 2). Single-crystal X-ray diffraction studies reveal that complexes 1, 2 and 3 belong to the polar point group 3m, and have the same two-dimensional honeycomb networks with(6, 3) topology. The ferroelectric behavior investigation indicates that all of these compounds are typical ferroelectric with an electric hysteresis loop showing a remnant polarization(Pr) of ca. 0.586 μC/cm2 and coercive field(Ec) of 2000 V/cm for 1,(Pr) of ca. 0.208 μC/cm2 and coercive field(Ec) of 2600 V/cm for 2 and(Pr) of ca. 0.27 μC/cm2 and coercive field(Ec) of 2 k V/cm for 3.Two new different CuII MOFs with two dimensional frameworks containing different building blocks {[Cu(tib)2]×(H2O)2×Br2}n(4)、{[Cu2(tib)×Br×Cl]×2Br}n(5)(Chapter 3) were obtained by one pot synthesized of tib with Cu Br in the presences of HCl, The CuII atom in complex 4 is four coordinated. However, there are two different cryptographic CuII atoms in complex 5, including four coordinated and six coordinated. The new novel metal-organic framework(MOF) {[Ni3(tib)2(H2O)12](SO4)3}n(6)(Chapter 4) was obtained by hydrothermal reaction of Ni SO4·6H2O and tib. Complex 6 is a 2D network honeycomb networks with(6, 3) topology, which is further linked together to three-dimensional(3D) frameworks by hydrogen bonds and π-π space superimposed effect.The second section: Clathrate compounds of crown [C6H14N-(18-crown-6)]+[Cl O4]-(7)、[C2H9N2-(18-crown-6)]+[Cl O4]-(8)、[H5N2-(18-crown-6)]+[Cl O4]-(9)(Chapter 5)were obtained by the solution method reaction of 18-crown-6, amine(such as cyclohexylamine, 1,2-ethanediamine, hydrazine hydrate etc.) under the adjustment of perchloric acid. The structures and properties of the compounds have been characterized by single-crystal X-ray diffraction studies, infrared spectra, elemental analysis, ferroelectric hysteresis loop analysis, measurement of dielectric constant, Differential Scanning calorimetry(DSC) and thermal gravimetric analysis so on in the paper. The measurements further confirm that all of the clathrate compounds 7, 8, 9 contain protonated amino groups; the compound 7 has the really rare reversible ferroelectric phase transition at high temperature 389.4 K; and 8 displays structural phase transition at about 287.4 K. |
PDF Full Text Request