Liu Yiping, Hao Aiyou, Xing Pengyao
Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University Jinan 250100 People's Republic of China
Chem Sci. 2024 Aug 28;15(38):15790-8. doi: 10.1039/d4sc04216f.
Developing chiral molecular platforms that respond to external fields provides opportunities for designing smart chiroptical materials. Herein, we introduce a molecular clamp whose chiral properties can be turned on by photoactivation. Selective anion binding achieves rational tuning of the conformations and chiroptical properties of the clamp, including circular dichroism and circularly polarized luminescence. Cyanostilbene segments were conjugated to chiral amines with a rotatable axis. Negligible chiroptical signals were significantly enhanced through a light illumination-induced isomerization. Binding with halide ions (F, Cl and Br) enables chiroptical inversion and subsequent amplification of the resulting opposite handedness state by photo treatment. In contrast, the larger I and NO ions failed to achieve chiroptical inversion. Also the handedness inversion was hampered in conformationally locked amines. Density-functional theory-based computational studies and experimental results reveal a structural transformation that proceeds from a butterfly-like open geometry to a closed V-shaped state initiated by four hydrogen bonds and the rotatable axis. This work illustrates design protocols for use in smart chiroptical molecular platforms mediated by photo treatment and anion binding.
开发能够响应外部场的手性分子平台为设计智能手性光学材料提供了机会。在此，我们介绍一种分子钳，其手性性质可通过光激活开启。选择性阴离子结合实现了对分子钳构象和手性光学性质（包括圆二色性和圆偏振发光）的合理调控。氰基芪片段与具有可旋转轴的手性胺共轭。通过光照诱导的异构化，可忽略不计的手性光学信号得到显著增强。与卤离子（F、Cl和Br）结合能够实现手性光学反转，并通过光处理对产生的相反手性状态进行后续放大。相比之下，较大的I⁻和NO₃⁻离子未能实现手性光学反转。同样，在手性构象锁定的胺中，手性反转也受到阻碍。基于密度泛函理论的计算研究和实验结果揭示了一种结构转变，该转变从类似蝴蝶的开放几何结构开始，通过四个氢键和可旋转轴引发，转变为封闭的V形状态。这项工作阐述了用于光处理和阴离子结合介导的智能手性光学分子平台的设计方案。
