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Pretzelanes with Planar Chirality and Guest Recognition Capabilities.
Songna Zhang1,2, Yuxi Wei1, Qiong Chen1
1Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
Journal of the American Chemical Society
|September 26, 2025
Summary
Researchers synthesized large macrocycles called pretzelanes using catenation, achieving high yields due to dynamic hydrazone bonds and hydrophobic effects. These chiral macrocycles can encapsulate guests and protect them from oxidation.
Area of Science:
- Supramolecular Chemistry
- Organic Synthesis
- Host-Guest Chemistry
Background:
- Developing macrocycles with guest recognition is crucial in host-guest chemistry.
- Efficient synthesis of large, robust macrocycles remains a challenge.
Purpose of the Study:
- To synthesize large macrocycles (pretzelanes) with high yields.
- To explore the guest recognition and photophysical properties of these macrocycles.
Main Methods:
- Utilizing catenation as the key ligation reaction for ring closure.
- Employing dynamic hydrazone bonds for error correction and hydrophobic effects to drive macrocycle formation.
- Characterizing the synthesized pretzelanes and their host-guest interactions.
Main Results:
- Achieved pseudo-quantitative yields for macrocycles with over 100 non-hydrogen atoms.
- Synthesized pretzelanes exhibiting intrinsic planar chirality due to a bridging unit.
- Demonstrated the ability of the pretzelane cavity to encapsulate hydrophobic guests.
- Showcased photo-induced electron transfer for guest protection within the macrocycle.
Conclusions:
- Catenation provides an efficient route to complex macrocyclic architectures like pretzelanes.
- The chiral pretzelane structure enables specific host-guest interactions and functional properties.
- Pretzelanes can act as protective cages for guest molecules, preventing photochemical degradation.
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