Phototriggered self-assembly of hydrogen-bonded rosette.
Phototriggered self-assembly of hydrogen-bonded rosette.
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DOI：
10.1021/ja047783z
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发表时间：
2004-08
影响因子：
15
通讯作者：
S. Yagai;T. Nakajima;T. Karatsu;K. Saitow;Akihide Kitamura
中科院分区：
文献类型：
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作者：
S. Yagai;T. Nakajima;T. Karatsu;K. Saitow;Akihide Kitamura
设计并合成了偶氮苯修饰的三聚氰胺M2和巴比妥酸盐B2，这两种化合物均具有大体积的三（十二烷氧基苯基）楔形结构，以构建光响应氢键超分子组装体.带有两个E-偶氮苯部分的几何异构体EE-M2很容易与B2络合，在氯仿、甲苯和甲基环己烷中得到非常稳定的环状六聚体EE-M2（3）. B2（3）（玫瑰花结），如尺寸排阻色谱、动态光散射、（1）H NMR和UV-vis研究所证实。由于TDP楔形物的空间拥挤（在玫瑰花结中总共有9个TDP楔形物），在用UV光照射时偶氮苯部分的E -> Z光异构化在玫瑰花结中被显著抑制，而单体EE-M2的照射导致容易转化成带有两个Z-偶氮苯部分的ZZ-M2。(1)H通过对初始光生ZZ-M2与B2络合的NMR研究发现，由于TDP楔之间的分子间空间相互作用，ZZ-M2很难与B2形成玫瑰花结。M2的光调节络合效率允许我们通过使用可见光照射ZZ-M2和B2的单体混合物来完成玫瑰花结的光触发形成。
Azobenzene-appended melamine M2 and barbiturate B2, both possessing bulky tridodecyloxyphenyl (TDP) wedge(s), were designed and synthesized to establish a photoresponsive hydrogen-bonded supramolecular assembly. The geometrical isomer EE-M2 bearing two E-azobenzene moieties easily complexed with B2, affording a remarkably stable cyclic hexamer EE-M2(3).B2(3) (rosette) in chloroform, toluene, and methylcyclohexane, as confirmed by size exclusion chromatography, dynamic light scattering, (1)H NMR, and UV-vis studies. The E --> Z photoisomerization of the azobenzene moieties upon irradiation with UV light was significantly suppressed in the rosette because of the steric crowding of the TDP wedges (total of nine TDP wedges in a rosette), whereas irradiation of the monomeric EE-M2 resulted in facile transformation into ZZ-M2 bearing two Z-azobenzene moieties. (1)H NMR studies of the complexation of the initially photogenerated ZZ-M2 with B2 revealed that it is hard for ZZ-M2 to form a rosette with B2 because of the intermolecular steric interaction between the TDP wedges. The photoregulatable complexation efficiency of M2 allowed us to accomplish the phototriggered formation of the rosette by irradiation of a monomeric mixture of ZZ-M2 and B2 using visible light.