Jouvelet Benjamin, Isare Benjamin, Bouteiller Laurent, van der Schoot Paul
Chimie des Polymères, UPMC Univ Paris 06, UMR 7610 , F-75005 Paris, France.
Langmuir. 2014 Apr 29;30(16):4570-5. doi: 10.1021/la403316a. Epub 2013 Nov 6.
The amplification of chirality, where a small imbalance in a chiral constituent is propagated into a strong optical purity, can occur in the spontaneous formation of helical 1-D stacks of molecules stabilized by hydrogen bonding, also known as supramolecular polymers. We have extended a statistical model by van Gestel et al. describing the highly nonlinear relationship between supramolecular helicity and enantiomeric excess for mixtures of enantiomers (the majority-rules effect) and quantitatively account for how this affects the thermodynamic stability of the assemblies. Our method allows for a direct comparison with experimental data, providing an unambiguous determination of the key parameters of the model (i.e., the mismatch and the helix reversal penalties). We demonstrate the successful application of this model to calorimetry data for bis-urea-based helical nanotubes, showing that reversals in the handedness of these nanotubes are not all that rare even though the helix reversal penalty is fairly large. By contrast, the mismatch penalty we obtain is small, implying that a large proportion of enantiomers are present in tube fractions not of their preferred handedness.
手性放大是指手性成分中的微小不平衡被放大为强烈的光学纯度，这种现象可发生在通过氢键稳定的分子螺旋一维堆叠的自发形成过程中，这种堆叠也被称为超分子聚合物。我们扩展了范·格斯特尔等人的统计模型，该模型描述了对映体混合物中超分子螺旋度与对映体过量之间的高度非线性关系（多数规则效应），并定量说明了这如何影响组装体的热力学稳定性。我们的方法允许与实验数据进行直接比较，从而明确确定模型的关键参数（即错配和螺旋反转罚分）。我们证明了该模型在基于双脲的螺旋纳米管量热数据中的成功应用，表明尽管螺旋反转罚分相当大，但这些纳米管的手性反转并非罕见。相比之下，我们得到的错配罚分较小，这意味着很大一部分对映体存在于非其偏好手性的管级分中。
