Crystal Melting by Light: X-ray Crystal Structure Analysis of an Azo Crystal Showing Photoinduced Crystal-Melt Transition
Crystal Melting by Light: X-ray Crystal Structure Analysis of an Azo Crystal Showing Photoinduced Crystal-Melt Transition
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DOI：
10.1021/ja503652c
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发表时间：
2014-06-25
影响因子：
15
通讯作者：
Koshihara, Shin-ya
中科院分区：
文献类型：
--
作者：
Hoshino, Manabu;Uchida, Emi;Koshihara, Shin-ya
在含有偶氮苯发色团和长链烷基链的偶氮化合物中，反式顺式光异构化导致了光致晶体-熔融转变(PCMT)。晶体的X-射线结构分析表明，在室温附近，结构有序的生色团通过pi中心点pi相互作用和无序的烷基链特征共存。这些结构特征表明，PCMT开始于晶体表面附近，并向深处传播，牺牲了pi中心点pi的相互作用。粉末X射线衍射图在光照射下的时间变化和双组分相图可以作为产物积累的函数对PCMT进行定性分析，并随后进行顺式异构体的重建结晶。这是第一次对显示PCMT的化合物进行结构表征，克服了使X射线晶体结构分析困难的低周期性。
Trans-cis photoisomerization in an azo compound containing azobenzene chromophores and long alkyl chains leads to a photoinduced crystal-melt transition (PCMT). X-ray structure analysis of this crystal clarifies the characteristic coexistence of the structurally ordered chromophores through their pi center dot center dot center dot pi interactions and disordered alkyl chains around room temperature. These structural features reveal that the PCMT starts near the surface of the crystal and propagates into the depth, sacrificing the pi center dot center dot center dot pi interactions. A temporal change of the powder X-ray diffraction pattern under light irradiation and a two-component phase diagram allow qualitative analysis of the PCMT and the following reconstructive crystallization of the cis isomer as a function of product accumulation. This is the first structural characterization of a compound showing the PCMT, overcoming the low periodicity that makes X-ray crystal structure analysis difficult.