Molecular-based dielectric switching materials are special crystal–crystal structure phase transition materials, and play an important role in multifunctional materials and other fields. In this paper, a trivalent cyclic amine is used as the building unit to successfully prepare a molecular crystal material, 1,4,7-triazacyclononane trihydrochloride, 1, with abundant hydrogen bonds and high temperature dielectric switching properties, and its IR, TGA, DSC, VT-PXRD (variable-temperature PXRD), VT-structures, and T–ε′ (temperature dependence of the real part of the dielectric constant) are characterized and analyzed. The space group of 1 is P2₁/n at 298 K and Rm at 403 K. Two endothermic peaks appeared near 369 K and 380 K and one exothermic peak appeared near 363.5 K in the DSC heating–cooling cycle test. In the vicinity of the corresponding phase transition temperature, 1 shows an obvious reversible change of dielectric plateau and small dielectric loss. The dielectric switching cycle curves show that 1 has good dielectric switching performance. All of these interesting physical properties are closely related to the reversible order–disorder states of cations and anions in the molecule. This work shows that 1 is a switchable dielectric molecular crystal material with broad application prospects, and provides a new route for design and synthesis of switchable dielectric materials with excellent properties.

中文翻译：

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分子晶体材料1,4,7-三氮杂环壬烷三盐酸盐的高温可切换介电性能

分子介电开关材料是特殊的晶-晶结构相变材料，在多功能材料等领域发挥着重要作用。本文以三价环胺为构建单元，成功制备了具有丰富氢键和高温介电开关性能的分子晶体材料1,4,7-三氮杂环壬烷三盐酸盐1 ，并对其IR、TGA、对 DSC、VT-PXRD（变温 PXRD）、VT 结构和T – ε ′（介电常数实部的温度依赖性）进行了表征和分析。1的空间群在 298 K 时为P 2 ₁ / n且R m为 403 K。DSC 加热-冷却循环测试中，在 369 K 和 380 K 附近出现两个吸热峰，在 363.5 K 附近出现一个放热峰。在相应的相变温度附近，1表现出明显的介电平台可逆变化和较小的介电损耗。介电开关循环曲线表明1具有良好的介电开关性能。所有这些有趣的物理性质都与分子中阳离子和阴离子的可逆有序无序状态密切相关。这项工作表明1是一种具有广阔应用前景的可开关介电分子晶体材料，为设计和合成性能优良的可开关介电材料提供了新的路线。