Design And Synthesis Of Organic-Inorganic Hybrid Phase Change Materials And Study Of The Phase Change,Dielectric And Second-Order Nonlinear Optical Properties

Organic-inorganic hybrid materials occupy an important position in the fields of information storage,energy conversion,photoelectric switches and multifunctional devices because of their rich and diverse phase transition properties,dielectric properties,nonlinear optical properties and ferroelectric properties.The organic amine cations in organic-inorganic hybrid compounds are easy to undergo ordinal-disordered or displacement phase transitions under the influence of the environment,which may result in dielectric anomalies,second harmonic generation（SHG）effect or pyroelectric effect.Therefore,organic amine molecules play a crucial role in the functional design of organic-inorganic hybrid compounds.Spherical organic amine molecules are prone to directional rotation under the influence of temperature,from an initial spherical structure with low symmetry to a quasi-spherical structure with higher symmetry.It not only can induce structural phase transition efficiently,but also has outstanding performance in inducing ferroelectric properties.Based on the organic-inorganic hybrid design strategy and quasi spherical type theory,a series of phase change materials with dielectric and second harmonic bistable effects were designed and synthesized using spherical organic amine molecules as organic ligands and metal halides as inorganic ligands.In Chapter II,based on the bicyclic molecule 1,5-diazabicyclo[330]octane and its derivatives,we designed and synthesized a series of organic inorganic hybrid compounds with reversible phase transitions,dielectric,and second harmonic effects:[330-Hdabco]PbBr₃（1）、[330-Hdmedabco]PbBr₃（2）、[330-Br CH₂-dabco]Fe Br₄（3）、[330-Br C₂H₄-dabco]Fe Br₄（4）、[330-FCH₂-dabco]Fe Br₄（5）.Compounds 1 and 2 are the one-dimensional chain organic-inorganic hybrid perovskite compounds constructed by PbBr₂ and 1,5-diazabicyclo[330]octane and 2,6-dimethyl-1,5-diazabicyclo[330]octane in high concentration HBr solution,respectively.Compounds1 and 2 exhibited an order-disorder structural phase transition and switchable second harmonic generation effects at 387 K and 456 K,respectively.Compounds 3 and 4crystallized in non-centric space groups Pca2₁ and P3c₁,respectively,before the phase transition.The three compounds underwent two reversible phase transitions,and all had obvious dielectric anomalies and SHG switchable properties.These three compounds may be potential ferroelectric compounds based on their spatial group information,SHG switchable and large dielectric anomaly behavior.Chapter III,Based on three spherical molecules,1,5-diazabicyclo[322]nonane（1,5-322-dabcn）,1,5-diazabicyclo[332]decane（332-dabcd）and 1,5-diazabicyclo[333]undecane（333-dabcu）,We constructed five organic-inorganic hybrid perovskite compounds with three-dimensional skeleton structure[1,5-322-H₂dabcn]Rb（NO₃）₃（6）、[332-H₂dabcd]Cs I₃（7）、332-H₂dabcd]Cs Br₃（8）、[333-H₂dabcu]Cs I₃（9）、[333-H₂dabcu]Cs Br₃（10）.All the five compounds underwent phase transitions above room temperature,among which 6、7、8 and 9 had reversible SHG properties,compound 7 underwent three-step SHG switches and compound 8underwent two-step SHG switches.In addition,compounds 6 and 8 crystallized in the same polar space group Pca2₁,indicating that the two compounds not only have nonlinear optical properties,but also may have ferroelectric properties.In Chapter IV,four zero-dimensional organic-inorganic hybrid like perovskite compounds were designed and synthesized using the bicyclic molecules 1,5-diazabicyclo[330]octane and 1,4-diazabicyclo[322]nonane（1,4-322-dabcn）as organic ligands and zinc halide as inorganic skeleton:[330-H₂dabco]Zn Br₄（11）,[1,4-322-H₂dabcn]Zn Cl₄（12）、[1,4-322-H₂dabcn]Zn Br₄（13）、[1,4-322-H₂dabcn]Zn I₄（14）.Compound 11 underwent a reversible phase transition at 373/337 K.Before the phase transition,the compound crystallizes in a monoclinic system with a polar point group m,and after the phase transition,it crystallizes in a triclinic system with a lower symmetry,using a central symmetric space group P2₁/n.That is,compound 11 underwent a phase transition behavior of antisymmetric breaking.In addition,the compound has stable dielectric bistable and SHG switching properties.Compound 12、13 and 14underwent reversible phase transitions at 391/352 K、380/365 K and 471/336 K,respectively,but only compound 12 showed dielectric anomaly.The three compounds crystallized in space groups P2₁/n、P2₁/nand Pca2₁ at room temperature,respectively,and none of them showed reversible SHG switching properties.In Chapter V,using bicyclic molecules 1,5-diazabicyclo[330]octane,1,4-diazabicyclo[322]nonane,1,5-diazabicyclo[332]decane,and1,5-diazabicyclo[333]undecane as organic ligands,tetrahedral acids HCl O₄,HRe O₄,HBF₄,inorganic acids HNO₃,and HI acids as inorganic ligands,we synthesized six non-metallic organic-inorganic hybrid compounds:[330-Hdabco]Cl O₄（15）、[330-Hdabco]Re O₄（16）、[333-Hdabcu]Cl O₄（17）、[333-Hdabcu]BF₄（18）、[1,4-322-dabcn][NO₃]₂（19）、[332-dabcd]I₂（20）.Compounds 15、16、17、18 and 19 crystallized at room temperature in centrosymmetric space groups Pbcm、P2₁/n、P4₂/mbc、P4₂/mbc、Pbca,respectively.The transformation temperatures are 225/210 K、341/311 K、368/360 K、375/364 K and 417/393 K,respectively,and the dielectric anomalies are obvious.Different from the above five compounds,Compound 20 crystallized in the polar space group Pca2₁ before the phase transition.The phase transition temperature was about 300 K,and the reversible SHG switching property was observed at the phase transition point.The information of the space group and the SHG switching property suggested that the compound could be a potential ferroelectric compound.