Аннотация: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 in the presence of cucurbit[7]uril (CB[7]). The detailed analysis of the UV/Vis and NMR spectra showed that the isomeric composition of the photostationary mixtures of SP can be modulated by the host–guest complexation with CB[7]. It was found that steric hindrance caused by encapsulation of SP in the host cavity induced 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 dye without CB[7]. Remarkably, the displacement of anti Z-SP from the CB[7] did not lead to the transformation of the anti Z-isomer into the syn Z-isomer pointing out the conformational memory of the system. The obtained results provide an interesting example of the supramolecular stereorecognition by achiral CB[7] host.
