Anisotropic strain release in a thermosalient crystal: correlation between the microscopic orientation of molecular rearrangements and the macroscopic mechanical motion
Anisotropic strain release in a thermosalient crystal: correlation between the microscopic orientation of molecular rearrangements and the macroscopic mechanical motion
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DOI：
10.1039/c8sc05563g
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发表时间：
2019-04-21
期刊：
影响因子：
8.4
通讯作者：
Ito, Hajime
中科院分区：
文献类型：
--
作者：
Seki, Tomohiro;Mashimo, Takaki;Ito, Hajime
显着效应是指有机和有机金属分子晶体在外界刺激下发生相变而引发的跳跃现象，在过去的五年中得到了广泛的研究。在这一研究领域中的一个具有挑战性的课题是如何表征相变过程中积累的微观应变的释放，这产生了宏观机械运动的问题。在本文中，我们描述了三苯基乙烯基金4-氯苯基异氰化物络合物1的热凸效应，其在以50 ℃ min（-1）冷却和以30 ℃ min（-1）加热时在约-100 ℃可逆地跳跃。单晶X-射线衍射测量和差示扫描量热分析1表明在此温度下发生的热相变。详细的结构分析表明，各向异性的变化，分子排列发生在1，从而结晶a轴收缩冷却时，而B轴膨胀。同时，晶体尺寸发生宏观变化。这被观察为弯曲，即，作为晶体边缘的倾斜，并且以分裂的形式，其发生在与主晶轴垂直的方向上。因此，这项研究的桥梁之间的差距差距的宏观机械响应，观察到在高速摄影图像和微观变化的晶体结构，这是通过X射线衍射测量面索引进行评估。
The salient effect, which refers to a jumping phenomenon of organic and organometallic molecular crystals typically triggered by phase transitions in response to external stimuli, has been investigated intensively in the last five years. A challenging topic in this research area is the question of how to characterize the release of microscopic strain accumulated during phase transitions, which generates macroscopic mechanical motion. Herein, we describe the thermosalient effect of the triphenylethenyl gold 4-chlorophenyl isocyanide complex 1, which jumps reversibly at approximately -100 degrees C upon cooling at 50 degrees C min(-1) and heating at 30 degrees C min(-1). Single-crystal X-ray diffraction measurements and differential scanning calorimetric analyses of 1 suggest the occurrence of a thermal phase transition at this temperature. Detailed structural analyses indicate that anisotropic changes to the molecular arrangement occur in 1, whereby the crystallographic a axis contracts upon cooling while the b axis expands. Simultaneously, macroscopic changes of the crystal dimensions occur. This is observed as bending, i.e., as an inclination of the crystal edges, and in the form of splitting, which occurs in a perpendicular direction to the major crystal axis. This study thus bridges the gap between macroscopic mechanical responses that are observed in high-speed photographic images and microscopic changes of the crystal structure, which are evaluated by X-ray diffraction measurements with face indexing.