Suit[3]ane

Suitanes are a class of mechanically interlocked molecules (MIMs) that consist of two components: a body with limbs protruding outward and a suit that fits appropriately around it, so that there is no easy way for the suit to be removed from the body. Herein, we report the synthesis and characterization of a suit[3]­ane, which contains a benzotrithiophene derivative (THBTT) with three protruding hexyl chains as the body and a 3-fold symmetric, extended pyridinium-based cage, namely, HexaCage6+, as the suit. Central to its realization is effective templation, provided by THBTT during cage formation, an observation that has been supported by the strong binding constant between benzotrithiophene (BTT) and the empty cage. The solid-state structure of the suit[3]­ane reveals that the body is confined within the suit’s cavity with its alkyl chains protruding outward through the orifices in the cage. Notably, such a seemingly unstable molecule, having three flexible alkyl chains as its only protruding limbs, does not dissociate after prolonged heating in CD3CN at 100 °C under pressure for 7 days. No evidence for guest exchange with the host was observed at this temperature in a 2:1 mixture of THBTT and HexaCage6+ in CD3CN. The results indicate that flexible protruding limbs are sufficient for a suit[3]­ane to remain mechanically stable even at high temperatures in solution.

索套烷（Suitanes）是一类机械互锁分子（mechanically interlocked molecules, MIMs），由两种组分构成：带有向外伸出臂状结构的骨架主体，以及与之精准适配的套状组件，二者无法通过常规手段实现分离。本文报道了套[3]烷（suit[3]ane）的合成与表征：该分子以带有三条伸出己基链的苯并三噻吩衍生物（THBTT）作为骨架主体，以三重对称的扩展型吡啶鎓基笼HexaCage6+作为套状组件。实现该合成的核心在于笼体形成过程中THBTT所提供的有效模板效应，这一结论得到了苯并三噻吩（BTT）与空笼之间强结合常数的实验佐证。套[3]烷的固态结构显示，骨架主体被限制在套状组件的空腔内部，其烷基链通过笼体开孔向外伸展。值得注意的是，这类仅以三条柔性烷基链作为伸出臂的看似不稳定的分子，在加压条件下于100℃的氘代乙腈（CD3CN）中加热7天后并未发生解离。在该温度下，将THBTT与HexaCage6+以2:1的比例混合于氘代乙腈中，未观察到客体与主体发生交换的迹象。实验结果表明，仅依靠柔性伸出臂即可使套[3]烷在溶液高温条件下仍保持机械稳定性。