具有共轭结构的非手性分子在界面通过自组装能够形成手性超分子, 这种自发对称性破缺的过程为解释生命起源提供了线索, 相关研究具有重要的科学意义。 目前, 尽管文献中对于界面手性自组装的机理有了详细的探讨, 但对于手性结构的动力学过程缺乏深入的研究。 为了阐明界面自组装手性是否会随时间变化, 利用二次谐波-线二色谱方法(SHG-LD)研究了偶氮苯衍生物PARC18在气/液界面的超分子自组装手性。 结果表明, PARC18在纯水表面形成了手性状态稳定的宏观结构, 而在亚相为NaOH溶液时, 界面形成的手性结构状态随时间变化。 此外, 在纯水表面, 谐波信号主要源于电偶极矩的贡献, 而在NaOH溶液表面, 磁偶极距对谐波信号, 尤其是手性信号的贡献占主导。 推测这是由于在碱性条件下, 界面的PARC18分子发生构型异构化, 分子中的两个发色团相互耦合, 导致手性结构发生变化, 同时增强了磁偶极的贡献。

Achiral molecules with conjugated structures can form chiral supramolecules through interfacial self-assembly. These spontaneous symmetry breaking processes may help elucidate the origin of life and are thus of great importance. So far, the mechanism of interfaciam self-assembly has been discussed in detail. However, dynamics of the chiral assemblies was rarely investigated. In order to clarify whether the chiral structures are stable or dynamic, we employed second harmonic generation linear dichroism (SHG-LD) to investigate the supramolecular chirality of PARC18 at air/aqueous interface. It was shown that PARC18 formed chiral structures with stable chiral state at air/water interface. While at air/NaOH solution interface, the chiral state changed with time. In addition, on NaOH solution subphase, contributions of magnetic dipole to second harmonic signals were dominant. We suggest that this is due to isomerization of PARC18 molecules on NaOH solution subphase. As a result, the two chromophores coupled with each other and the magnetic dipole contribution was enhanced.