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Azacalixquinarenes: From Canonical to (Poly-)Zwitterionic Macrocycles
Simon Pascal1, Lucien Lavaud1, Cloé Azarias2
1Aix Marseille Université, CNRS UMR 7325, CINAM , Campus de Luminy, case 913 , Marseille 13288 Cedex 09 , France.
The Journal of Organic Chemistry
|January 5, 2019
Summary
New azacalixquinarenes, macrocycles with unique quinone structures, were synthesized. These compounds exhibit tunable properties based on their canonical and zwitterionic forms, influenced by molecular structure and solvent.
Area of Science:
- Supramolecular Chemistry
- Organic Synthesis
- Materials Science
Background:
- Azacalixarenes are macrocyclic compounds with potential applications in various fields.
- Understanding the electronic properties of macrocycles is crucial for designing new materials.
Purpose of the Study:
- To synthesize and characterize a new family of macrocycles, azacalixquinarenes.
- To investigate the existence and properties of canonical and zwitterionic quinone forms within these macrocycles.
- To explore the factors influencing the equilibrium between these forms.
Main Methods:
- Selective oxidation of parent azacalixarenes to form azacalixquinarenes.
- Crystallographic analysis to determine molecular structures.
- Spectroscopic and electrochemical methods to study electronic properties.
- Theoretical calculations (first-principle approaches) to support experimental findings.
Main Results:
- Successful synthesis of azacalixquinarenes, macrocycles featuring diaminobenzoquinone diimine units linked by dinitrobenzene rings.
- Crystallographic data confirmed the coexistence of canonical (uncharged) and zwitterionic quinone forms within the same molecule.
- Intramolecular H-transfer, triggered by electron-withdrawing dinitrobenzene groups, leads to zwitterionic quinone formation.
- The equilibrium between canonical and zwitterionic forms is sensitive to N-substituents and solvent polarity, affecting optical and electrochemical properties.
- Poly-zwitterionic structures were achieved in [4]- and [6]-membered macrocycles, validated by experimental and theoretical studies.
Conclusions:
- Azacalixquinarenes represent a novel class of macrocycles with tunable electronic properties.
- The presence of both canonical and zwitterionic quinone forms offers opportunities for designing functional supramolecular materials.
- Understanding the factors controlling the quinone tautomerism is key to harnessing their distinct optical and electrochemical characteristics.
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