文献类型：期刊文献

英文题名：Unidirectional threading synthesis of isomer-free [2]rotaxanes

作者：Wang, Qiao-Chun[1]; Ma, Xiang[1]; Qu, Da-Hui[1]; Tian, He[1]

机构：[1]E China Univ Chem Technol, Adv Mat Lab, Shanghai 200237, Peoples R China;[2]E China Univ Chem Technol, Inst Fine Chem, Shanghai 200237, Peoples R China

年份：2006

卷号：12

期号：4

起止页码：1088

外文期刊名：CHEMISTRY-A EUROPEAN JOURNAL

收录：;EI(收录号：2006059674986);WOS:【SCI-EXPANDED(收录号:WOS:000234945400013)】；

语种：英文

外文关键词：cyclodextrins; molecular shuttles; photoisomerization rotaxanes; supramolecular chemistry

摘要：The threading of an a-cyclodextrin (alpha-CyD) by an unsymmetrical dumbbell generally results in two isomeric [2]rotaxanes differing in the orientation of the alpha-CyD. In this work, two methods have been developed for the unidirectionally threading an alpha-CyD to obtain isomer-free [2]rotaxanes. These methods use the Suzuki coupling of a boronic acid derivative and a halide in aqueous alkaline solution. The conformations of the two unidirectional [2]rotaxanes-R3 and R4 were determined by 2D H-1 ROESY NMR spectra. The optical spectral studies revealed that each of the two [2]rotaxanes can proceed with E/Z photoisomerization and shuttling motions of the alpha-CyD ring on the thread under alternating irradiation at 330 and 275 nm, accompanied by fluorescence intensity changes at 530 run. The induced circular dichroism (ICD) spectra of another two analogous [2]rotaxanes R1 and R2 were also studied. Distinctive ICD signal changes resulting from the photoisomerization with respect to the movements of alpha-CyD were detected. This demonstrates that, besides the fluorescence, ICD signal is another way to identify the shuttling motions of alpha-CyD in these [2]rotaxanes.