Chirality Gearing in an Achiral Cage through Adaptive Binding

Herein we report an adaptive, achiral trithiourea molecular cage and its conformational and stereodynamics towardtricarboxylate anion binding. The cage was readily synthesized in four steps with a 44% yield for the irreversible cage-formingreaction. It possesses aflexible conformation and strongly binds 1,3,5-benzene tricarboxylate by forming a sandwich-like inclusioncomplex, with an affinity up to 106M-1in acetonitrile. Upon binding, the cage is locked in a twisted helical conformation. Byincorporation of three chiral arms on the guest, a gear-like complex dominant in one given helical sense was produced. Due to thesteric crowding in the helical grooves, a small change of methyl to ethyl on guest caused a striking difference on binding and chiralinduction. The system thus represents a rare example of chiral induction on aflexible, achiral host and provides a decoupled modelthat the generation of a racemate and following chiral discrimination can be individually probed

Automated summary

An adaptive, achiral trithiourea molecular cage and its conformational and stereodynamics toward tricarboxylate anion binding are reported. The cage exhibits a flexible conformation and strongly binds 1,3,5-benzene tricarboxylate, forming a sandwich-like inclusion complex. By incorporating chiral arms on the guest, a gear-like complex with a specific helical sense is produced.