圆偏振光及搅拌对自组装体系中的超分子手性调控

Chirality is one of the basic properties of the nature. Achiral components can self-assemble into chiral supermolecules via various intermolecular non-covalent interactions, which is called spontaneous symmetry breaking, attracted more and more attentions recently, owing to it is closely related to the origin of life. However, based on the achiral nature of building blocks, these chiral assemblies often appear in left handed sense and right handed sense simultaneously, or the numbers of two enantiomers of chiral assemblies are equivalent and enantiomeric excess is zero in an unperturbed state. Control the preference of chiral assemblies or obtain homochirality is an interesting issue from a fundamental perspective but can also lead to novel functional materials. To solve this problem, two strategies are elucidated. One is to introduce chiral dopants to induce the assemblies exhibiting homochirality. The other that does not involve chiral molecular species is to use physical force field, including circularly polarized light, vortex stirring, and magnetic field. The physical force field is supposed to provide a chiral environment for the formation of assemblies. In this project, we will investigate whether the physical force field is effective in inducing almost 100% ee (enantiomeric excess). Irradiation of circularly polarized light (CPL) and vortex stirring will be used as physical force field here. We want to obtain a large imbalance in the two chiral domains and inducing homochirality of assemblies from achiral building blocks using CPL. The enantioselectivity can be controlled by the handedness of the CPL. Further, vortex stirring with clockwise or counterclockwise is another physical force to be provided. These techniques will open up the possibility of enantioselectively converting achiral components into chiral assemblies for practical use in functional materials. In order to understand the influence of the nucleation and growth process of supramolecular assemblies on the chirality of the final self-assembled system, the competition and synergism between molecular chirality and physical force field will be also explored.

手性是自然界的基本属性之一。从非手性分子出发，经由分子间非共价键相互作用自发组装形成超分子手性组装结构的过程， 称之为“自发的对称性破缺”，这为理解与模拟自然界中手性的起源，乃至于生命的起源，提供了可行的思路。而由非手性分子出发构筑的手性组装体经常会出现手性方向的不可控性，即可能是左旋超分子，也可能是右旋自组装体，这影响了对自然界“单一手性”的深入认识，及后续相关手性功能的开发和利用。 针对这一问题，我们拟采用物理力场的方法诱导自组装体系的对称性破缺，在不引入本征手性分子的情况下，依靠物理力场的作用，力图实现超分子组装体的单一手性。拟采用的物理力场为圆偏振光辐照和涡流搅拌，通过圆偏振光的左旋或右旋及涡流搅拌方向的顺时针或逆时针，诱导单一超分子手性组装体的出现。并初步探索分子手性与物理力场的竞争，理解超分子组装体的成核、生长过程对最后所构筑的自组装体的手性的影响。

本项目旨在从自组装体系中的对称性破缺出发，拟采用物理力场的方法诱导自组装体系的对称性破缺，希望依靠物理力场的作用，实现超分子组装体的单一手性。采用的物理力场为光辐照、涡流搅拌和超声，诱导单一超分子手性组装体的出现。并在此基础上，探索了分子手性与物理力场的竞争，理解超分子组装体的成核、生长过程对最后所构筑的自组装体的手性的影响。在研究过程中，我们发现了一种简单的非手性小分子-3-硝基肉桂酸可通过氢键和分子间偶极-偶极相互作用自组装形成能量较低的螺旋结构，导致对称性破缺，详细研究了本体相中组装体中手性偏斜的出现及界面诱导的手性放大，有助于更好的理解自然界中手性的产生和放大。并在组装过程引入不同物理力场，如圆偏振光的辐照、涡流搅拌等，研究物理力场对硝基肉桂酸组装体的单一手性的影响，利用手性溶剂实现了单一手性的控制。此外，在非手性的金属-有机分子配合物体系中，实现了超声诱导的超分子手性的产生以及控制，为手性光学材料的构筑提供了新方法。再者，在分子本征手性和物理力场的竞争研究中，设计合成了含有可光二聚的肉桂酸谷胺酰胺手性两亲分子，发现两者的竞争中，分子的本征手性对超分子手性起着决定性的作用。