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Encapsulation-Controlled Photoisomerization of a Styryl Derivative: Stereoselective Formation of the Anti Z-Isomer in the Cucurbit[7]uril Cavity |
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| Authors: | Dr Ekaterina Y Chernikova Dr Daria V Berdnikova Dr Alexander S Peregudov Prof Olga A Fedorova Dr Yuri V Fedorov |
| Institution: | 1. Laboratory of Photoactive Supramolecular Systems, A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Science, Vavilova st. 28, 119991, Moscow, Russia;2. Universität Siegen, Organische Chemie II, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany;3. Laboratory of Nuclear Magnetic Resonances, A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Science, Vavilova st. 28, 119991 Moscow, Russia |
| Abstract: | The photochemical isomerization of a styrylpyridinium dye ( SP ) bearing an unsymmetrically attached benzo-15-crown-5 ether has been studied in aqueous solution in the absence and presence of cucurbit7]uril (CB7]). The detailed analysis of the UV/Vis and NMR spectra showes that the isomeric composition of the photostationary mixtures of SP can be modulated by the host-guest complexation with CB7]. It was found that steric hindrance caused by encapsulation of SP in the host cavity induces the exclusive formation of the anti conformer of Z- SP in contrast with the mixture of both anti and syn conformers obtained during photoisomerization of the dye without CB7]. Remarkably, the displacement of anti Z- SP from CB7] does not lead to the transformation of the anti Z-isomer into the syn Z-isomer pointing out the conformational memory of the system. The results provide an interesting example of the supramolecular stereorecognition by the achiral CB7] host. |
| Keywords: | cucurbituril photochemistry self-assembly stereoisomers styryl dye |