Host–guest complexation-induced chirality switching of pillararenes by perylene diimide-based hexagonal metallacages

Chirality in confined nanospaces has brought some new insights into chirality transfer, amplification, and chiroptical properties. However, chirality switching, which is a common phenomenon in biological systems, has never been realized in confined environments. Herein, we report a type of hexagonal metallacages that shows good host–guest interactions with ethoxy pillar[5]arene and pillar[6]arene, as confirmed by single-crystal X-ray analysis. Importantly, when a chiral pillar[5]arene-based molecular universal joint (MUJ) is used as the guest, the host–guest complexation would drive the alkyl ring of the MUJ flip from outside to inside the cavity of its pillar[5]arene unit, which enables the configuration change along with the chirality inversion of the MUJ. Moreover, the host–guest complexation facilitates the chirality transfer from guests to hosts, giving circularly polarized luminescence to the system. This study provides a unique metallacage-pillararene recognition motif for the chirality switching of planar chiral pillararenes, which will promote the construction of host–guest systems with tunable chirality for advanced applications.