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首页> 外文期刊>Chemistry: A European journal >Influence of the solvent and the enantiomeric purity on the transition between different supramolecular polymers
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Influence of the solvent and the enantiomeric purity on the transition between different supramolecular polymers

机译：溶剂和对映体纯度对不同超分子聚合物之间过渡的影响

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摘要

The self-assembly of two enantiomerically pure hexa(oligo (p-phenylene vinylene))-substituted benzenes having 24 stereocenters was studied in pure methylcyclohexane (MCH) and in a mixture of MCH/toluene (4:1). Irrespective of the solvent a cooperative supramolecular polymerization mechanism was determined for these star-shaped molecules by using temperature-dependent CD and UV/Vis spectroscopy. Quite remarkably, a transition from one helical supramolecular state (A) to a second more thermodynamically stable supramolecular helical assembly (B) was observed. The rate of the AaB transition was strongly dependent on the nature of the solvent; being faster in the solvent mixture than in pure MCH. By using size exclusion chromatography we could relate the increased rate to a decreased stability of the supramolecular A state in the solvent mixture. Next, we mixed the two enantiomerically pure hexa-substituted benzene derivatives in a so-called majority-rules experiment, which lead to the anitcipated chiral amplification in the A state. More importantly it appeared that the AaB transition was significantly hampered in these mixed systems. Furthermore, the absence of chiral amplification in the B state revealed the formation of separated enantiomerically pure assemblies. Therefore, by using a wide variety of spectroscopic and chromatographic techniques we determined the influence of solvent and enantiomeric purity on the transition between different supramolecular states.
机译：在纯甲基环己烷（MCH）和MCH /甲苯（4：1）的混合物中研究了两个具有24个立体中心的对映体纯的六（低聚（对亚苯基亚乙烯基））取代苯的自组装。无论使用哪种溶剂，都可以通过使用依赖于温度的CD和UV / Vis光谱确定这些星形分子的协同超分子聚合机理。非常明显地，观察到从一种螺旋超分子状态（A）到第二种热力学更稳定的超分子螺旋组件（B）的转变。 AaB转变的速率在很大程度上取决于溶剂的性质。在溶剂混合物中比在纯MCH中更快。通过使用尺寸排阻色谱，我们可以将增加的速率与溶剂混合物中超分子A态稳定性的下降联系起来。接下来，我们在所谓的多数规则实验中混合了两种对映体纯的六取代苯衍生物，这导致了A状态的手性扩增。更重要的是，在这些混合系统中，AaB的转变似乎受到了很大的阻碍。此外，在B状态下没有手性扩增表明分离的对映体纯的组装体的形成。因此，通过使用各种光谱和色谱技术，我们确定了溶剂和对映体纯度对不同超分子状态之间过渡的影响。

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