Synthesis,Structure And Dielectric Properties Of Molecular-Ionic Compounds Based On Chain Divalent Amine C₅H₁₆N₂

Phase transition materials,their physical properties（such as,optical,electrical,magnetic,etc.）can be changes when stimulated by the external environment（light,temperature,electric field,magnetic field,etc.）changes.Thus,it has been widely used in optoelectronic devices,data storage,semiconductors,capacitors and other fields.A series of molecular-ionic salt phase transition materials consisting of single protonated Hdabco（dabco=1,4-diazodicyclic[2.2.2]octane）as cations and ClO₄^-,BF₄^-,ReO₄^-,Br^-or I^-as anions,show excellent ferroelectric and dielectric properties under the stimulation of external conditions.This prompted researchers are looking at similar diprotonated components in order to develop more molecular ionic compounds with excellent properties.However,previous studies were focused on diprotonated organic cations achieving charge banlance by the same anion,which result in such compounds are not rich enough and their properties need to be improved.Based on this,the principle of crystal engineering is used in this thesis to design diprotonated molecular-ionic salt compound.A series of molecular-ionic salt compounds with rich structure and higher dielectric constant have been isolated and characterized by introducing two different anions as valence equilibria.The work of this paper includes the following aspects:Using 2,2-dimethyl-1,3-propaneamine,a small chain organic molecule,as an organic cation,two different anions were introduced into the molecule-ionic salt system for charge balance for the first time.Nine molecular ionic salt compounds were obtained by aqueous solution and characterized in detail;Three compounds with the general formula of(C₅H₁₆N₂)BF₄X（X=Cl（1）,Br（2）,NO₃（3））were synthesized,and the phase transition occurred under the stimulation of temperature,with obvious first-order and reversible phase transition characteristics.Its dielectric constant increases obviously,which increases its application potential.By replacing BF₄^-anion with similar structure of ClO₄^-anion,four compounds of(C₅H₁₆N₂)ClO₄X（X=Cl（4）,Br（5）,I（6）,NO₃（7））were synthesized and characterized.They showed obvious first-order and reversible phase transition characteristics under the excitation of temperature.Two general formula of(C₅H₁₆N₂)PF₆X（X=Cl（8）,Br（9））compounds have been synthesized by substituting the tetrahedral anion with the PF₆^-anion with more coordination atoms.The as-synthesized of compound(C₅H₁₆N₂)PF₆Br exhibits obvious first-order reversible phase transition under temperature induction.The innovation of this thesis lies in:（1）For the first time,two different anions were introduced into the molecule-ionic salts system for valence equilibrium,which provides a new way to construct more solid phase transition materials with switchable dielectric behavior and higher dielectric constant.（2）The selection of chain organic cations with lower rotational degrees of freedom improves the phase transition temperature and dielectric constant of molecule-ionic salts compounds.（3）The phase transition temperature of the compound can be effectively adjusted by adjusting the types of the two anions.