Study On The Synthesis,Property Of Quaternary Ammonium And Cyclic Amine Organic-Inorganic Hybrid Compounds

Phase-transition materials,as a type of functional materials with switchable properties,hold significant application potential in various fields such as data storage,data communication,and signal sensing.These materials not only induce phase transitions by adjusting the organic amine framework but also enhance their optical properties through modifications to the inorganic framework.Therefore,the use of organic-inorganic hybrid materials are considered a promising chemical strategy for designing multi-channel switchable materials.In organic-inorganic hybrid materials,changes in physical properties at the microscopic level before and after phase transitions are closely related to the dynamics of molecular dipole motion,such as the common order-disorder phase transition.However,current research faces two main challenges:(1)how to rationally modify organic cations;(2)how to construct metal halide-inorganic frameworks to obtain multifunctional organic-inorganic hybrid materials.Molecular design methods may be an effective strategy to address these issues.Based on molecular design strategies,this paper designs and synthesizes a series of phase change materials with dielectric,nonlinear optical properties,semiconductor properties,and ferroelectricity.Through molecular design and crystal engineering,this thesis designed and synthesized 28 novel organic-inorganic hybrid phase change materials,and characterized and studied their structures,phase transitions,and related physical properties.In Chapter 3,a series of organic-inorganic hybrid compounds with reversible phase transitions and dielectric properties were synthesized based on the hybrid design of metal Cd salts and quaternary ammonium salts:[F2C5H12N]2CdI4(1),[C7H18N]2CdI4(2),[ClC6H15N]2CdI4(3),[BrC6H15N]2CdI4(4),[F2C5H12N]2CdBr4(5),[C7H18N]2CdBr4(6),[BrC6H15N]2CdBr4(7),[ClC6H15N]2CdBr4(8).By modifying the substituents of the organic cations,significant changes were induced in the crystal structures and interactions between the anions and cations of the corresponding compounds,thereby regulating their phase transition behavior and dielectric properties.In Chapter 4,nine zero-dimensional organic-inorganic hybrid compounds were synthesized based on the hybridization of metal Fe salts,Gd salts,and quaternary ammonium salts:[C3H7NF]FeBr4(9),[C7NH18]FeCl4(10),[C7NH18]GaCl4(11),[C6NH16]FeCl4(12),[ClC6NH15]FeCl4(13),[BrC6NH15]FeCl4(14),[ClC6NH15]FeBr4(15),[F2C5H12N]FeCl4(16),and[F2C5H12N]GaCl4(17).Particularly,compound 9 represents the first example of a solid-state Second Harmonic Generation(SHG)switch exhibiting a true three-step "on-off-on-off" behavior above room temperature.Compounds 10 and 11 belong to rare two-step nonlinear optical materials,while compounds 12,13,14,and 15 exhibit single-step switchable SHG responses.Furthermore,significant dielectric anomalies were observed at the frequency doubling points for compounds 9,10,11,12,and 15,a characteristic feature of ferroelectric materials.Hence,it is inferred that these five compounds are potential ferroelectric materials.However,the single crystal quality of these compounds is characterized by poor hardness,brittleness,and high viscosity,especially compounds 13 and 14,making them easily film-forming.To improve crystal quality,compounds 16 and 17 were synthesized by introducing multiple fluorine atoms,with the results showing a significant enhancement in the crystal quality of these two compounds.In Chapter 5,based on metal Sn salts as the inorganic framework and organic ligand quaternary ammonium salts for hybridization,six zero-dimensional organicinorganic hybrid perovskite compounds were synthesized:[C6H16N]2SnBr4(18),[ClC6H15N]2SnBr4(19),[BrC6H15N]2SnBr4(20),[C7H18N]2SnCl4(21),[F2C5H12N]2SnCl4(22),[BrC6H15N]2SnBr4(23).The introduction of halogens is investigated to explore its influence on the semiconductor properties and nonlinear optical properties.Specifically,compounds 19 and 20,obtained by introducing halogens into the prototype compound 18,not only exhibit gradually enhanced phase transition temperatures but also demonstrate semiconductor properties.In the study of compounds 21,22,and 23,rapid nonlinear optical switching phenomena are observed at the phase transition points with the introduction of halogens,and this phenomenon persists after multiple cycle tests for compounds 22 and 23.In Chapter 6,utilizing trans-4-methylcyclohexylamine as an organic ligand,and tetrahedral acids HClO4,HReO4,along with inorganic halide salts CdCl2,SnBr4,FeBr3 as inorganic ligands,five organic-inorganic hybrid compounds were synthesized:[4MCHA]ClO4(24),[4-MCHA]ReO4(25),[4-MCHA]CdCl3(26),[4-MCHA]2FeBr5(27),and[4-MCHA]2SnBr6(28).The phase transitions of these five compounds rely on the synergistic effect of organic cation configuration flipping and the ordereddisordered transition of inorganic salts.Compound 24 exhibits switchable ferroelectric domains,belonging to a novel metal-free ferroelectric material,which is validated through Density Functional Theory(DFT)calculations.Comparatively,compound 25 shows a significant increase in phase transition temperature compared to compound 24,which is closely related to the magnitude of intramolecular hydrogen bonding and the mass of the high-rexide ion.The phase transition temperatures of compound 26 are 399 K/369 K,accompanied by distinct stepped dielectric anomalies and rare anti-symmetric breaking,where the crystal adopts a centrosymmetric space group before the phase transition and falls into a non-centrosymmetric space group afterwards.Compound 27 undergoes three phase transitions,making it a multi-phase transition compound.However,due to the close proximity of the phase transition points,the dielectric anomaly curve is highly complex and challenging to analyze.Compound 28 has a lower phase transition temperature but exhibits rare two-step switchable nonlinear optical properties controlled by signal intensity.In summary,this study comprehensively examines the dielectric properties,nonlinear optical behaviors,ferroelectricity,and semiconductor characteristics in the realm of organic-inorganic hybrid phase-change crystalline materials.This research furnishes essential experimental data and theoretical insights,paving the way for the development of multifunctional phase-change materials.