Synthesis,Structural Phase Transition And Dielectric Properties Of Compounds Based On High Symmetry Amine Derivatives

Solid-to-solid phase transition materials have attracted global interest,because of potential applications in data communication,phase shifters,signal processing,environment monitoring,etc,.It is crucial to prepare new phase transition materials,not only for the theoretical study of structure–property relationships,but also for the exploration of novel physical properties.In this paper,some compounds in the experiment were analyzed and discussed,and the structural analysis,dielectric performance test analysis and other detailed instructions were given to guide the further study.1.Based on 2,6-dimethylaniline,Two phase transition materials were synthesized and characterized with perchloric acid in deionized water and deuterium water environment.(C₈O₅H₁₂N)⁺·ClO₄^–·H₂O?1?;(C₈O₅H₁₂N)⁺·ClO₄^–·D₂O?2?;The crystal cell parameters of the compounds 1 and 2 were significantly changed by X–ray single crystal diffraction.Two compounds underwent the same phase transitions from space group Iba2 to C2/c but in different temperatures,and differential scanning calorimetry detected that two compounds underwent reversible phase transitions at 220 K and 283 K,respectively.The temperature dependence of the dielectric measurements also confirmed the phase transition.Comparison and analysis of them,The deuterium generation effect is helpful to find high-dielectric response and high temperature phase transition materials.2.Two compunds were synthesized by the mixed solution of Dabcodo and Metal salts.Ca?Dabcodo??H₂O?₄Cl₂?3?;?Dabcodo?·[Cu₃?H₂O?₈Cl₆]·2H₂O?4?;The characterization of IR,TG,PXRD and DSC and dielectric properties of the two compounds were investigated.Compound 3 underwent the phase transitions from space group I4/mmm to Cmcm in different temperatures.DSC evidenced that the compound 3 has a reversible phase transformation,However,compared with compound 3,the compound 4 had differdent coordination mode under the same experimental conditions,if only the metal elements were changed.The Ca ion in compound 3 is directly associated with the O coordination on Dabcodo.However,the Cu ion in compound 4 does not directly coordinate with O in Dabcodo.Through the above experimental comparison,it is concluded that the elements in main group can carry out coordination under certain conditions.3.The inorganic-organic hybrid compounds Zn?CH₃-DabcoH?X₃?X=Cl,Br,I?was synthesized under slow evaporation conditions.Zn?CH₃-DabcoH?Cl₃?5?;Zn?CH₃-DabcoH?Br₃?6?;Zn?CH₃-DabcoH?I₃?7?;Three compounds underwent the same phase transitions from space group P2₁/c to P2₁/m but in different temperatures,Differential scanning calorimetry?DSC?measurements indicated that compound 1,2 and 3 underwent the reversible phase transitions at-27.9?,35.1?and 113.4?,respectively.The disorder–order transformation of the Dabco ring and H atom of-CH3 in Zn?CH3-DabcoH?X3?X=Cl,Br,I?may drive the structural phase transition.The dielectric permittivity of compound 5 and 6 can be switched between two states,which could be used in switchable dielectric devices.It is found that,under the same conditions,as the halogen atom radius increases,the phase transition point of compounds is transferred to the high temperature region.4.Two organic–inorganic hybrid compounds was synthesized by the reaction of MI₂?M=Zn,Co?with[CH₃-Dabco-CH₃]²⁺·2Br^–in aqueous solution.?CH₃-DabcoH₂-CH₃?·ZnI₄?8?;?CH₃-DabcoH₂-CH₃?·CoI₄?9?;Single-crystal X-ray diffraction data disclose that the phase transitions of compounds 8 and 9 are from the low-temperature phase with the space group P2₁/n to the high-temperature phase with the space group P2₁/m.Differential scanning calorimetry measurements indicate that two compounds underwent a reversible phase transition at 20.5?and 48.7?,respectively.At the same time,The temperature dependence of the dielectric permittivity demonstrates a step-like change.