Light-Triggered Crystallization of a Molecular Host-Guest Complex
Light-Triggered Crystallization of a Molecular Host-Guest Complex
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DOI：
10.1021/ja103620z
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发表时间：
2010-07-28
影响因子：
15
通讯作者：
Shionoya, Mitsuhiko
中科院分区：
文献类型：
--
作者：
Clever, Guido H.;Tashiro, Shohei;Shionoya, Mitsuhiko
超分子组装体结构变化的控制是分子机器发展的关键。使用光作为外部输入的有机化合物如偶氮苯的可逆光异构化是特别适合的，因为不产生废物。基于我们以前的研究定量封装适当大小的双磺酸客人的自组装，金属有机笼组成的四个刚性，弯曲的双单齿吡啶配体和两个Pd（II）离子，我们在这里展示了如何光开关客体顺式-4，4 '-偶氮苯双磺酸酯可以从其1：1的主客体络合物的光异构化引发的反式异构体驱逐。使用高度可溶的PEG化笼衍生物，证明了这种光驱动的封装/释放过程的完全可逆性。相比之下，含有1当量顺式客体的可溶性较低、未取代笼的样品显示在客体光异构化后会立即结晶。X射线结构分析证实了客体分子已经离开了主体的空腔，相反，通过从外部结合到它们的Pd（II）中心，将笼连接成聚合物材料。
The control of structural changes in supramolecular assemblies is a key point in the development of molecular machines. The reversible photoisomerization of organic compounds such as azobenzene using light as an external input is especially suited because no waste products are generated. Based on our previous studies on the quantitative encapsulation of suitably sized bis-sulfonate guests by a self-assembled, metal organic cage consisting of four rigid, bent bis-monodentate pyridyl ligands and two Pd(II) ions, we show here how the light-switchable guest cis-4,4'-azobenzene bis-sulfonate can be expelled from its 1:1 host guest complex triggered by its photoisomerization to the trans-isomer. Using a highly soluble, PEGylated cage derivative, the full reversibility of this light-driven encapsulation/release process is demonstrated. In contrast, a sample of the less soluble, unsubstituted cages including 1 equiv of the cis-guest was shown to result in immediate crystallization upon photoisomerization of the guest. X-ray structure analysis confirmed the guest molecules having left the cavity of the host and on the contrary joining the cages into a polymeric material by binding to their Pd(II) centers from outside.