Single-Atom Tuning of Pyridine-Strapped Pillar[5]arene Capsules for Specific Guest Binding

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Host-Guest Chemistry

Background:

• Pillar[5]arenes are macrocyclic hosts with tunable cavities.
• Bis(carboxamide) functionalization can introduce specific binding interactions.
• Controlling supramolecular capsule structure is key to functional applications.

Purpose of the Study:

• To synthesize pyridine bis(carboxamide)-strapped pillar[5]arene capsules.
• To investigate the structure-property relationships of these supramolecular capsules.
• To evaluate their host-guest binding capabilities for aliphatic organic guests.

Main Methods:

• Synthesis of pyridine bis(carboxamide)-strapped pillar[5]arene macrocycles.
• Characterization of supramolecular capsule structures, including macrotricyclic products.
• Host-guest binding studies using various aliphatic guests (nitrile, isocyanide, amine functionalities).

Main Results:

• Successful synthesis of pyridine bis(carboxamide)-strapped pillar[5]arene capsules.
• Discovery of serendipitous macrotricyclic product formation.
• Demonstrated length-selective recognition of aliphatic guests, with exceptional affinity for 1,2-diaminoethane (Ka > 10^4 M^-1).

Conclusions:

• The structural integrity, dictated by nitrogen atom orientation, governs the capsule's electronic properties.
• These supramolecular capsules exhibit high selectivity and affinity for specific organic guests.
• The findings highlight the potential of pillararene-based capsules in precise molecular recognition.