Synthesis, Characterization, Ferroelectric And Dielectric Properties Of The Complexes Based On Chiral Ligands?H₂-nbpdc? And DABCO Derivatives

High performance ferroelectric, dielectric materials are functional materials with wide applications prospect in aerospace, energy, construction and other fields. Viewed from current situation, researches and applications of ferroelectric and dielectric materials with high performance are still in the developing stage. In order to find new ferroelectric and dielectric materials, based on reading a lot of ferroelectric and dielectric materials on the related literature, modified high symmetry heterocyclic ligand 1,4-diazabicyclo [2.2.2] octane (Dabco) with chemical method, we obtained a nitrogen oxide 1,4-diazabicyclo [2.2.2] octane-N,N'-oxide (Dabcodo) and a quaternary ammonium salt based on Dabco. A series of metal organic compounds and molecular ion compounds prepared by the synthesis of two compounds and axially chiral ligand,2,2'-dinitro-4,4'-biphenyl dicarboxylic acid H2-nbpdc, the phase transition point, molecular structures of in two phases, ferroelectric and dielectric properties of the compounds were further studied.1. Two metal-organic coordination compounds with phase transition properties were prepared by the self-assembly of Dabcodo and transition metal ions M (M= Ag+, Pb2+) respectively. {[Ag3(Dabcodo)(NO3)3]·H2O}n (1); [Pb(Dabcodo)(NO3)(OH)]n (2);The crystal structures and phase transition temperature of two compounds were determined by variable temperature single crystal structure analysis and DSC measurements. The phase transition of compound 1 was further verified by means of variable temperature X-ray powder diffraction. Furthermore, ferroelectric and dielectric properties of compound 1 and dielectric properties of compound 2 have been studied separately. Among which, the DSC result of 1 shows that the compound occurs phase transition when the temperature cooling to 217 K, single crystal structure in both room temperature phase (293 K) and low temperature phase (123 K) were determined by single crystal structure test, meanwhile, dielectric response of 1 is evident around point of phase transition. Ladder shaped peak dielectric response were occurred at both heating and cooling processes. Hysteresis loop of compound 1 show that remanent polarization value 0.23?C/cm2, the saturation polarization value 0.36 ?C/cm2 and the coercivity 13.3 kV/cm, respectively. Compound 2 underwent a phase transition at 176 K with DSC measurement. Crystal structure of 2 also crystallized in tetragonal system space group I41/a in room temperature phase, and translated to monoclinic system space group C2/c via variable temperature single crystal structure analysis. The disorder of Dabcodo ring was the main reason of phase transition.2. Six novel 3-D metal-organic compounds were prepared by hydrothermal method of H2-nbpdc,4,4'-bpy and transition metal ions M (M= Ag+, Pb2+) respectively. [Ni(nbpdc)(4,4'-bpy)(H2O)]n (3); [Ni2(nbpdc)2(4,4'-bpy)2(H2O)2]n (4); [Ni(nbpdc)(4,4'-bpy)]n (5); [Mn(nbpdc)(4,4'-bpy)]n (6); [Co(nbpdc)(4,4'-bpy)]n (7); [Zn2(nbpdc)2(4,4'-bpy)]I1 (8);Dielectric test results showed that compounds 3-8 had different responses in different temperature ranges. Compounds 3 and 8 occurred ladder response of dielectric at 275K. Compound 4 exhibited a slightly steep platform at 250 K and nearly double that before 250 K. Compounds 5,6 and 7 also appeared ladder response at 230 K,245 K and 265 K, respectively. Besides, Gas sorption measurement confirmed the permanent porosity of complex 3, which revealed N2 adsorption at 77 K. The total pore volume is 0.20cm3/g with the BET area 391.76 m2/g. The distribution of pore sizes of complex 3 is less than 2 nm. Magnetic tests showed that compounds 6 and 7 have obvious antimagnetic properties. Compound 3 showed a new topology structure of sqc6. Complex 4 exhibited a rare three-interlude 3D structure with (44.62)(48.66.8) topology. Complexes 5-7 featured the same topology structure of (44.610.8)(44.62). Complex 8 had a 3D framework with (10)(6.82.103.124)2(62.8)2(8)2 topology.3. One organic molecular-ionic compound with ferroelectric phase transition was obtained based on Dabcodo ligand. C6Hi4N2O22+2C1O4-(9);Phase transition of compound 9 appeared at around 218.5 K and crystallized in monoclinic system space group P21/c in room temperature (293 K) phase, and translated to monoclinic system space group P21 in low temperature (123 K) phase. Dielectric anomaly also found at around transformation temperature. Hysteresis loop of compound 9 show that remanent polarization value 1.47 ?C/cm2, the saturation polarization value 0.75 ?C/cm2 and the coercivity 12.74 kV/cm, respectively. The order-disorder transition of Dabcodo ring caused the phase transition.4. One organic molecular-ionic compound with phase transition was obtained based on [(CH3)2CH-Dabco]+Br" ligand. C9H20N2+·2PF6- (10);Compound 10 underwent a phase transition at 133.1 K and variable temperature crystal structure showed 10 crystallized in orthorhombic system space group Pbca in room temperature phase, and translated to monoclinic system space group P21/c in low temperature phase and was also confirmed by dielectric measurement. The change of intermolecular hydrogen bonds and twist of Dabco ring caused the phase transition.