Chasing chirality recognition reaction in the solid-state

在固体状态下，分子的行为通常与溶液状态不同。我们发现，包合物中的非手性化合物与光学活性主体发生光环化反应，对映体选择性地生成手性产物。这与在溶液中进行的相同反应形成了鲜明的对比，在溶液中产生外消旋混合物。通过X射线结构分析，揭示了高对映体选择性的原因。用单晶X-射线单晶衍射法跟踪反应过程。主体分子的晶胞内结构和位置几乎不受反应的影响，主体与客体分子之间的氢键保持不变。固态Cd在反应过程中表现出一系列具有等色点的光谱，为了检测固态Cd的手性，有必要观察固态Cd。固态由于其巨大的各向异性而受到伪影的困扰。我们设计并制作了一台用于去除伪影以获得真镉的固态专用镉分光光度计，该仪器包括高质量的光电倍增管和光弹调制器，以及可方便地插入或从光路中取出的分析器。样品和分析仪可以方便地旋转。安装了两个锁定放大器来记录50和100 kHz信号。将该方法应用于单晶和薄膜中。

In the solid state, molecules often behave differently from solution state. We have found that a photocyclization reaction of a non-chiral compound in an inclusion compound with an optically active host, enantio-selectively produced a chiral product. This is in sharp contrast to the same reaction carried out in solution state where racemic mixture was produced. We have revealed the reason behind the high enantio-selectivity by X-ray structural work. The reaction process was followed by X-ray single-crystal diffractometry using one single-crystal. The structure and location within the unit-cell of the host molecule hardly changed by the reaction and the hydrogen bonds between the host and the guest molecules were kept. Solid-state CD exhibited a series of spectra with isosbestic points during the reaction process.To detect solid-state chiroptical properties, it is necessary to observe CD in the solid state. Solid-state suffers from artifacts due to its large anisotropy. We have designed and made a solid-state dedicated CD spectrophotometer to remove artifacts to obtain true CD.The instrument houses a good quality phtomultiplier and a photoelastic modulator, and an analyzer which can be inserted or removed from the optical path easily. Sample and the analyzer can be rotated easily. Tow lock-in-amplifiers are installed to record 50 and 100 kHz signals. This method was applied to single crystals and films.