Thermosalience of 1,2,4,5-Tetrachlorobenzene,Israel Journal of Chemistry

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Thermosalience of 1,2,4,5-Tetrachlorobenzene
Israel Journal of Chemistry ( IF 2.3 ) Pub Date : 2021-08-19 , DOI: 10.1002/ijch.202100056
Durga Prasad Karothu ₁ , Panče Naumov ₁

Affiliation

Crystals undergoing a thermosalient phase transition are capable of small and cooperative rearrangement of their structural units that is converted into rapid and readily observable crystal shape transformation, ballistic events, and/or progression in space. This amplification of dynamics from molecular to macroscopic scale is attractive for fast and efficient conversion of heat into mechanical work in devices such as micromechanical actuators. By using microscopic, thermal and structural analysis here we demonstrate the thermosalient effect in single crystals of 1,2,4,5-tetrachlorobenzene (TCB), an analogue of the well-known thermosalient tetrabromo compound. It is shown that TCB crystals are reversibly thermosalient when they transition between two solid phases, labeled forms I and II, however contrary to the tetrabromo compound which is thermosalient above room temperature, the effect occurs below room temperature. Comparison of the structures of the two phases shows that, similar to other thermosalient solids, the two phases of TCB feature identical sheet motif of molecules in their structures, and the transition is governed by subtle changes in the orientation of molecules which are held together by π-π and weak Cl⋅⋅⋅Cl interactions. This structural perturbation generates strain within the crystal and the sudden release of the accumulated strain results in crystal motion.

中文翻译：

1,2,4,5-四氯苯的热显着性

经历热显着相变的晶体能够对其结构单元进行小的协同重排，从而转化为快速且易于观察的晶体形状转变、弹道事件和/或空间进展。这种从分子到宏观尺度的动力学放大对于将热快速有效地转换为微机械致动器等设备中的机械功很有吸引力。通过在此使用微观、热和结构分析，我们证明了 1,2,4,5-四氯苯 (TCB) 单晶的热显着效应，这是众所周知的热显着四溴化合物的类似物。结果表明，当 TCB 晶体在两个固相（标记为 I 型和 II 型）之间转变时，它们具有可逆的热显着性，然而，与在室温以上具有热显着性的四溴化合物相反，该效应在室温以下发生。两相结构的比较表明，与其他热固性固体类似，TCB 的两相在其结构中具有相同的分子片状基序，并且转变是由分子取向的细微变化控制的，这些分子通过π-π 和弱 Cl⋅⋅⋅Cl 相互作用。这种结构扰动在晶体内产生应变，累积应变的突然释放导致晶体运动。过渡是由分子取向的细微变化控制的，这些变化通过 π-π 和弱 Cl⋅⋅⋅Cl 相互作用保持在一起。这种结构扰动在晶体内产生应变，累积应变的突然释放导致晶体运动。过渡是由分子取向的细微变化控制的，这些变化通过 π-π 和弱 Cl⋅⋅⋅Cl 相互作用保持在一起。这种结构扰动在晶体内产生应变，累积应变的突然释放导致晶体运动。

更新日期：2021-10-25

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