Structure And Dielectric Properties Of Organic-inorganic Hybrid Compounds Containing Trimethylphosphine Derivatives

In recent years,organic-inorganic hybrid phase transition compounds have become a research hotspot because of their potential applications in dielectric switching devices,signal processing,sensing and information storage.These materials combine the characteristics of organic materials and inorganic materials,showing many advantages such as structural tunability,easy property control,easy processability and low toxicity.Most of organic-inorganic hybrid phase transition compounds currently studied are mainly small molecular ammonium and small molecular phosphine compounds.Many phase transition materials with excellent properties can be obtained by group modification of cations or replacement of anions.In order to explore new organic-inorganic hybrid phase transition materials,we designed and synthesized a series of organic-inorganic hybrid compounds with quaternary phosphonium cation based on trimethylphosphine and explored their dielectric properties and phase transition behaviors.This thesis mainly introduces 10 new organic-inorganic hybrid compounds with quaternary phosphonium cation:[（CH₃）₃PCH（CH₃）₂]₂[Cd Br₄]（1）,[（CH₃）₃PCH（CH₃）]₂[Zn Br₄]（2）,[（CH₃）₃PCH（CH₃）₂]₂[Mn Br₄]（3）,[（CH₃）PCH（CH₃）₂][Cd（SCN）₃]（4）,[（CH₃）₃PCH₂CH（CH₂）₂][Cd Br₃]（5）,[（CH₃）₃PCH₂CH（CH₂）₂][Cd（SCN）₃]（6）,[（CH₃）₃PCH₂CH（CH₂）₂]₂[Zn Br₄]（7）,[（CH₃）₃PCH₂CH（CH₂）₂]₂[Mn Br₄]（8）,[（CH₃）₃PCH₂CH（OH）CH₃][Cd Br₃]（9）,[（CH₃）₃PCH₂SCH₃][Cd Cl₃]（10）.We performed infrared spectroscopy and X-ray powder diffraction experiments on these 10 substances to determine their purity and determined the single crystal structure by X-ray single crystal diffraction.Dielectric response test was used for preliminary screening of phase transition compounds and differential scanning calorimeter was used to further determine whether the compounds had undergone a phase transition.The experimental results show that dielectric anomalies are observed in a series of hybrid compounds 1,2,3 and 4 with（1-methylethyl）trimethylphosphine as the cation in the high temperature range and there are also obvious endothermic and exothermic peaks in differential scanning calorimetry measurement,confirming that they undergo reversible structural phase transitions.The stepped dielectric anomalies are observed in compounds 7 and 8 with（methylcyclopropyl）trimethylphosphine as the cation at high temperature and the corresponding endothermic and exothermic peaks also appear in the differential scanning calorimetry results,indicating that the compounds 7 and 8undergo reversible structural phase transitions.The dielectric constants and differential scanning calorimetry patterns of the remaining compounds show no anomalies,indicating that they don’t undergo structural phase transitions.