Uniaxial negative thermal expansion induced by molecular rotation in a one-dimensional supramolecular assembly with associated peculiar magnetic behavior
Uniaxial negative thermal expansion induced by molecular rotation in a one-dimensional supramolecular assembly with associated peculiar magnetic behavior
复制标题
一维超分子组装体中分子旋转引起的单轴负热膨胀以及相关的特殊磁性行为
DOI：
10.1039/d2tc04874d
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发表时间：
2023
影响因子：
6.4
通讯作者：
Nakamura Takayoshi
中科院分区：
文献类型：
--
作者：
Takahashi Kiyonori;Shirakawa Yuki;Sakai Hiroki;Hisaki Ichiro;Noro Shin-ichiro;Akutagawa Tomoyuki;Nakano Motohiro;Nakamura Takayoshi
一般来说，负热膨胀（NTE）是熵驱动的。我们发展了另一种方法来实现单轴NTE的分子晶体诱导的超分子变形和分子旋转，沿着与特殊的磁响应。在（pyridazinium+）2（dibenzo[24]crown-8）3[Ni（dmit）2]−2（1）（dmit = 1，3-dithiole-2-dithiolate-4，5-dithiolate）的晶体中，pyridazinium包含在二苯并[24]crown-8中，并形成平行于a轴的一维柱状结构。该柱沿着a轴伸长，并且沿着b轴收缩。这为哒嗪鎓旋转提供了空间，这进一步促进了183 K以上的NTE。此外，[Ni（dmit）2]−形成二聚体，其中二聚体内磁交换相互作用（J）随温度升高而增加。修正的单重态-三重态热激发模型，其中J随温度的升高而增加，可以拟合到1的温度依赖性磁化率。在180 K以上观察到与模型的偏离，这归因于[Ni（dmit）2]−二聚体内的结构变化，由哒嗪鎓部分的分子旋转引起。
In general, negative thermal expansion (NTE) is entropy-driven. We have developed the alternative approach for achieving uniaxial NTE in a molecular crystal induced by supramolecular deformation and molecular rotation, along with peculiar magnetic responses. In the crystal of (pyridazinium+)2(dibenzo[24]crown-8)3[Ni(dmit)2]−2 (1) (dmit = 1,3-dithiole-2-thione-4,5-dithiolate), pyridazinium was included within the dibenzo[24]crown-8, and formed a one-dimensional columnar structure parallel to the a-axis. This column elongates along the a-axis, and shrinks along the b-axis. This provides space for the pyridazinium to rotate, which promotes further NTE above 183 K. In addition, the [Ni(dmit)2]− forms a dimer, where the intradimer magnetic exchange interaction (J) increases with increasing temperature. The modified singlet–triplet thermal excitation model, where J increased with increasing temperature, can be fitted to the temperature-dependent magnetic susceptibility of 1. A deviation from the model was observed above 180 K, which is attributed to the structural changes within the [Ni(dmit)2]− dimer, caused by the molecular rotation of the pyridazinium moiety.