Cucurbit[8]uril (Q[8] or CB[8]), as a synthetic macrocyclic host, plays an important role in constructing various water soluble dynamic supramolecular polymers and materials. Here we report host–guest interactions of Q[8] with π-conjugated bispyridinium guests in aqueous solution that resulted in a series of unprecedented dynamic 2 : 2, 2 : 3, and 1 : 2 assemblies (guest/Q[8]). Most importantly, these subtly different host–guest binding modes could be distinguished by naked-eye observation of the resulting quantitative fluorescence emissions. Further characterization suggested that the Q[8] host-stabilized charge-transfer interactions could be dissociated and controlled by the N-substituted alkyl chains on the cationic guests via the formation of a 2 : 3 quinary complex or a U-shaped conformation, which led to the discovery of new possible binding modes for the Q[8] host.

中文翻译：

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葫芦[8]触发的动态主客体组装的荧光可视化

葫芦[8]尿素（Q [8]或CB [8]），作为合成的大环主体，在构建各种水溶性动态超分子聚合物和材料中起着重要作用。在这里，我们报告了Q [8]与π共轭双吡啶鎓客体在水溶液中的主客体相互作用，这导致了一系列前所未有的动态2：2、2：3和1：2组装（guest / Q [8]） 。最重要的是，可以通过肉眼观察所得的定量荧光发射来区分这些微妙的宿主-客体结合模式。进一步的表征表明，可以通过阳离子客体上的N-取代的烷基链通过以下途径解离和控制Q [8]稳定的主体电荷转移相互作用： 2：3的五元复合物或U形构象的形成，导致Q [8]宿主发现新的可能的结合模式。