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Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes
Carmine Gaeta1, Carmen Talotta1, Placido Neri1
1Dipartimento di Chimica e Biologia " A. Zambelli", Università di Salerno, Via Giovanni Paolo II 132, 84084 Fisciano (Salerno), Italy.
This study reports atropoisomeric pseudorotaxanes formed by threading a calixarene wheel with ammonium axles. The distinct conformations of the calixarene wheel lead to kinetic and thermodynamic isomers.
Area of Science:
- Supramolecular Chemistry
- Organic Chemistry
Background:
- Atropoisomerism in pseudorotaxanes arises from restricted rotation around chemical bonds.
- Calixarenes are versatile macrocyclic hosts capable of forming inclusion complexes.
Purpose of the Study:
- To synthesize and characterize atropoisomeric pseudorotaxanes using a calixarene wheel and ammonium axles.
- To investigate the conformational dynamics and interconversion mechanisms of these pseudorotaxanes.
Main Methods:
- Synthesis of hexahexyloxycalix[6]arene and functionalized ammonium axles.
- Formation and isolation of pseudorotaxane complexes.
- Structural characterization using spectroscopic techniques.
Main Results:
- Two distinct atropoisomeric pseudorotaxanes were formed, adopting 1,2,3-alternate and cone conformations.
- Interconversion between conformations requires axle de-threading and re-threading due to blocked rotation.
- The 1,2,3-alternate and cone forms were identified as kinetic and thermodynamic products, respectively.
Conclusions:
- The conformational preferences of the calixarene wheel dictate the atropoisomerism in these pseudorotaxanes.
- Axle inclusion significantly restricts conformational mobility of the calixarene host.
- Understanding these isomerism mechanisms is crucial for designing novel supramolecular architectures.
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