Chirality Gearing in an Achiral Cage through Adaptive Binding

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Molecular Recognition

Background:

• Molecular cages are crucial for host-guest chemistry, enabling selective binding and encapsulation.
• Achiral hosts capable of inducing chirality in guests are rare and valuable for asymmetric synthesis.
• Understanding conformational changes upon guest binding is key to designing functional supramolecular systems.

Purpose of the Study:

• To synthesize and characterize an adaptive, achiral trithiourea molecular cage.
• To investigate the cage's conformational dynamics and stereodynamics upon binding tricarboxylate anions.
• To explore the potential for chiral induction using this flexible, achiral host system.

Main Methods:

• Multi-step organic synthesis for cage construction.
• Spectroscopic techniques (NMR, UV-Vis) for characterization and binding studies.
• Crystallography to determine complex structures and conformational changes.

Main Results:

• A novel achiral trithiourea molecular cage was synthesized with 44% yield.
• The cage forms a sandwich-like inclusion complex with 1,3,5-benzene tricarboxylate with high affinity (10^6 M^-1).
• Guest incorporation induces a conformational lock in the cage, and chiral guests lead to gear-like complexes with defined helical sense, demonstrating chiral induction.

Conclusions:

• The developed molecular cage is a flexible, achiral host capable of strong guest binding and conformational adaptation.
• This system represents a rare example of chiral induction by an achiral host, enabling decoupled studies of racemate generation and chiral discrimination.
• The findings offer a new platform for designing sophisticated molecular machines and sensors.