Synthesis And Properties Of Halogenoindium(Ⅲ) And Sulfates Phase Change Material Templated By Organic Amine

The organic-inorganic hybrid materials with organic and inorganic characteristics are inexpensive,environment friendly so they have been extensively studied.The kinetic state of organic-inorganic hybrid compounds are easily changed with the change of external temperature leading to micro-structural phase transitions.So they are potential molecular-based phase change materials.Phase transitions are always accompanied by changes in enthalpy,movement of molecules or ions,crystal structure and physical properties.In order to synthesize novel organic-inorganic hybrid phase change materials that meet the need of reality,it should be understood the response relationship among external stimulus,micro-structure and physical properties.we have read a large number of related literatures and selected N,N-dimethyl-1,3-propanediamine,cyclopentylamine and 2,2-dimethyl-1,3-propanediamine as primary ligands.Four organic-inorganic hybrid complexes were synthesized by amines and trivalent In metal salts.Then the crystal structure,phase transition temperature and dielectric properties of the target products were studied.1.The organic-inorganic hybrid compound(C5H16N2)2(InBr6)(InBr4)(1)was obtained by the reaction of N,N-dimethyl-1,3-propanediamine with indium trioxide(In2O3)in concentrated bromic acid aqueous solution.The variable temperature X-ray single crystal diffraction analyses indicated that compound 1 crystallizes in the orthorhombic crystal system with the Pnma space group.But crystal data have not been collected at low temperature because of crystal cracking.From microscopic phase transition mechanism,we can found that the phase transition could be mainly associated with the disorder of N,N-dimethyl-1,3-propanediamine cation and[InBr4]anion at room temperature.It was found by differential scanning calorimetry measurement(DSC)that compound 1 undergoes a reversible and second-order phase transition around T=170.2 K.As expected,the temperature-dependent dielectric constant measurement exhibited the dielectric constant increases with increasing temperature in a certain temperature range,according with the result of DSC.2.The organic-inorganic hybrid compound(C5H12N)8(InBr6)(InBr4)Br4(2)was obtained by the reaction of cyclopentylamine with indium trioxide(In2O3)in concentrated bromic acid aqueous solution.The DSC test showed that compound 2 has two consecutive reversible structural phase transitions at T1=158.7 K and T2=140.8 K,which belong to the second-order phase transition.The variable temperature X-ray single crystal diffraction analyses revealed that the compound 2 crystallizes in tetragonal system with the central symmetric I41/a space group at room temperature and low temperature.The main reason for the phase transition may be the structure change of the tetracoordinate[InBr4]-anion as well as reorientation of the flexible cyclopentylamine cation(C5H12N)+at room temperature and low temperature.The temperature-dependent dielectric constant exhibited the step-like dielectric anomaly.3.The organic-inorganic hybrid compound(C5H12N)4(InCl6)Cl·H2O(3)was obtained by the reaction of cyclopentylamine with Indium(Ⅲ)chloride tetrahydrate(InCl3·4H2O)in concentrated hydrochloric acid aqueous solution.The differential scanning calorimetry(DSC)showed that reversible structure phase occurred near 180 K.It can be found from the micro-structure that the crystals both crystallized in the orthorhombic system at 296 K(room temperature)and 100 K(low temperature).But the space group and the unit cell parameters are different at room and low temperatures.At the room temperature compound 3 belongs to the Pnma space group,and at the low temperature compound 3 belongs to the Cmcm space group.In addition,the accurately crystal structure analysis testified that the change of the cyclopentylamine cation configuration and the significant change of the disordered atoms are the major force for the structural phase transition with decreasing temperature.the temperature-dependent dielectric constant showed that the abnormal dielectric occurs at around the phase transition point.4.The organic-inorganic hybrid compound(C5H16N2)(InBr5)(4)was obtained by the reaction of 2,2-dimethyl-1,3-propanediamine with indium trioxide(In2O3)in concentrated bromic acid aqueous solution.The measurements of DSC showed that compound 4 undergoes second-order reversible structural phase transition near T=187.4 K.At room temperature,compound 4 crystallizes in the orthorhombic Pnma space group.However,the complete crystal data have not been collected and a rough crystal framework can be obtained at low temperature.The reason for the phase change is mainly that the protonated 2,2-dimethyl-1,3-propanediamine is disordered at room temperature,and the amine is frozen into an ordered state with decreasing temperature.The dielectric constant is obviously anomaly for compound 4 in the phase change process.5.N,N,N’N’-tetramethylethylenediamine dibisulfate(C6H18N2)(HSO4)2(5),was synthesized via the reaction of CuO4·5H2O with N,N,N’N’-tetramethylethylenediamine(TMEDA)in sulfuric acid aqueous solution.Differential scanning calorimetry measurement(DSC)discloses that(C6H18N2)(HSO4)2 undergoes a reversible second-order phase transition at 247.7 K with a small hysteresis(ca.2.5 K).The variable-temperature X-ray single crystal structural analyses indicate that(C6H18N2)(HSO4)2 crystallizes in triclinic system with centrosymmetric space group P 1 at low-temperature phase(LTP)and room-temperature phase(RTP).The cell volume of LTP shows an approximately doubling that of RTP and the remarkable differences of cell parameters between RTP and LTP reveal the phase transition.The phase transition of(C6H18N2)(HSO4)2 could be mainly associated with the disorder-order transformation of HSO4-as well as reorientation of the flexible branched chain-like(C6H18N2)2+cations with decreasing temperature.As expected,the temperature-dependent dielectric constant of(C6H18N2)(HSO4)2 exhibits remarkable peak-like dielectric anomalies around 245 K in accordance with the DSC result.