Neutral anion-detecting organic cages based on anion-π interactions

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Molecular cages are crucial for selective guest encapsulation.
• Anion-π interactions are key for binding anions within electron-deficient cavities.
• Tuning cage properties through precursor modification is essential for optimizing host-guest chemistry.

Purpose of the Study:

• To synthesize novel neutral tetrahedral molecular cages.
• To investigate the role of substituents on tris-aldehyde precursors in modulating anion binding affinity.
• To explore the impact of anion encapsulation on intramolecular CH-π interactions within the cages.

Main Methods:

• Self-assembly of tetrahedral molecular cages via condensation reactions.
• Systematic variation of substituents on tris-aldehyde precursors.
• Anion binding studies using various analytical techniques.
• Nuclear Magnetic Resonance (NMR) spectroscopy to probe host-guest interactions.

Main Results:

• Neutral tetrahedral molecular cages were synthesized in high yields.
• Electron-withdrawing substituents (Cl, Br, CF3-Ph) enhanced anion binding affinity.
• Electron-donating groups (Ph) decreased binding affinity.
• Fluorine substituents unexpectedly reduced binding affinity due to a repulsive field effect.
• Anion encapsulation modulated intramolecular CH-π interactions, providing anion-specific NMR signatures.

Conclusions:

• The electron-deficient cavity of the triazine core facilitates anion encapsulation via anion-π interactions.
• Substituent effects on the tris-aldehyde precursors significantly influence anion binding affinity.
• Intramolecular CH-π interactions within the cage framework are sensitive to guest encapsulation, enabling anion recognition.