School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, PR China.
J Phys Chem Lett. 2021 Feb 4;12(4):1307-1315. doi: 10.1021/acs.jpclett.0c03739. Epub 2021 Jan 27.
Halogenation brings about dramatic variations to the performance of self-assembled organic species, such as luminescence and crystallinity, but it has seldom been utilized for chirality control. Here we show the halogenation effect of self-assembling organic building units on supramolecular chirality and chiroptical responses. N-terminal aromatic amino acids with different substituted halogen atoms at -phenylalanine residues self-assembled into one-dimensional fibrous structures. Halogenation induced the emergence of macroscopic chirality regardless of halogen properties like electronegativity, generating exclusive homochiral helical structures. Solid-state X-ray structures and time-dependent density functional theory were utilized for calculated electronic circular dichroism spectra, which evidenced the diverse driving forces to enable chiral molecular arrangements, including H-bonds and halogen bonds. Red-shifted luminescence was observed in brominated building units, giving rise to active circularly polarized luminescence. This work elucidates the multiple roles of halogen in chiral self-assembly systems, which provides insight into the rational control over supramolecular chirality and their chiroptical applications.
卤化作用使自组装有机物种的性能发生显著变化，例如发光和结晶性，但很少用于手性控制。在这里，我们展示了自组装有机构筑单元在手性超分子和圆二色性响应中的卤化效应。具有不同取代卤原子的 N-端芳族氨基酸在 - 苯丙氨酸残基处自组装成一维纤维结构。卤化作用导致宏观手性的出现，而与卤原子的性质（如电负性）无关，从而产生了独特的同手性螺旋结构。利用固态 X 射线结构和含时密度泛函理论计算了电子圆二色性光谱，证明了包括氢键和卤键在内的多种驱动手性分子排列的力。在溴化构筑单元中观察到红移发光，导致活性圆偏振发光。这项工作阐明了卤化在手性自组装体系中的多重作用，为合理控制超分子手性及其圆二色性应用提供了新的思路。
