Temporary and Permanent Trapping of the Metastable Twisted Conformer of an Overcrowded Chromic Alkene via Encapsulation

An overcrowded alkene with an anti-folded conformation
was converted
to its twisted conformer, accompanied by a dramatic color change from
yellow to deep purple, by inclusion in a self-assembled Td-symmetric coordination cage. The shape
of the caged cavity was suitable and desirable for trapping of the
twisted conformer. The twisted conformation was temporarily memorized
in the alkene even after guest ejection. Permanent trapping of the
twisted conformation was achieved by bromination of the twisted conformer
formed in situ in the cage.

带有反折叠构象（anti-folded conformation）的拥挤烯烃（overcrowded alkene），经包裹进入自组装Td对称配位笼（self-assembled Td-symmetric coordination cage）后，可转化为其扭曲构象体（twisted conformer），同时伴随从黄色至深紫色的显著颜色变化。该配位笼的笼腔形状适配且适于捕获该扭曲构象体。即便客体（guest）被脱除后，该扭曲构象仍可在该烯烃中被暂时留存。通过对笼中原位（in situ）生成的扭曲构象体进行溴化（bromination）反应，可实现对该扭曲构象的永久捕获。