Unprecedented Reverse Volume Expansion in Spin-Transition Crystals
Unprecedented Reverse Volume Expansion in Spin-Transition Crystals
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DOI：
10.1002/chem.202001821
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发表时间：
2020-09-16
影响因子：
4.3
通讯作者：
Guionneau, Philippe
中科院分区：
文献类型：
--
作者：
Guo, Wenbin;Daro, Nathalie;Guionneau, Philippe
目前围绕自旋交叉现象的研究热潮在一定程度上可以用金属离子从HS态到LS态的转变导致的体积减小的力学性质来解释。与此相反，分子络合物[Fe(PM-pBrA)(2)(NCS)(2)]的晶胞体积从HS增大到LS。单晶和粉末X射线衍射与磁性测量相结合，揭示了这一与热和光激自旋转换有关的前所未有的反直觉行为。有趣的是，这种异常的体积变化似乎伴随着苯环的广泛旋转，这导致晶体中的结构堆积发生了剧烈的修改，尽管是可逆的。此外，通过光诱导激发自旋态陷阱获得的光诱导HS态显示出非常高的弛豫温度，即T(LIESST)，为109K，是迄今报道的最高温度之一。上述一组非常不同寻常的特性为旋转交叉材料的开发开辟了新的可能性领域。
The current craze for research around the spin crossover phenomenon can be justified to some extent by the mechanical properties due to the decrease of volume associated with the transition of the metal ion from the HS state to the LS state. As demonstrated here, the molecular complex [Fe(PM-pBrA)(2)(NCS)(2)] exhibits, on the contrary, an increase of the unit-cell volume from HS to LS. This counter-intuitive and unprecedented behavior that concerns both the thermal and the photoexcited spin conversions is revealed by a combination of single-crystal and powder X-ray diffraction complemented by magnetic measurements. Interestingly, this abnormal volume change appears concomitant with the wide rotation of a phenyl ring which induces a drastic modification, though reversible, of the structural packing within the crystal. In addition, the light-induced HS state obtained through the Light-Induced Excited Spin-State Trapping shows a remarkably high relaxation temperature, namely T(LIESST), of 109 K, one of the highest so far reported. The above set of quite unusual characteristics opens up new fields of possibilities within the development of spin crossover materials.