Equatorial Sulfur Atoms in Bambusurils Spawn Cavity Collapse

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Computational Chemistry

Background:

• Bambusurils (BUs) are macrocyclic compounds with potential applications in molecular recognition.
• Understanding the conformational preferences of BUs is crucial for designing functional molecules.

Purpose of the Study:

• To investigate the conformational behavior of bambusurils with equatorial sulfur atoms.
• To explore the influence of intramolecular van der Waals interactions on BU conformation.
• To develop new synthetic routes to functionalized bambusurils.

Main Methods:

• Synthesis of novel bambusuril derivatives (eq-semithio-BU[4] and ax-semiaza-eq-semithio-BU[4]).
• Nuclear Magnetic Resonance (NMR) spectroscopy.
• X-ray crystallography.
• Computational modeling.

Main Results:

• Bambusurils with equatorial sulfur atoms adopt compact conformations, not the anion-binding jigger form.
• Strong intramolecular van der Waals attractive interactions are responsible for this conformational preference.
• Intramolecular distances and torsional angles are reliable conformational indicators for BUs.
• Chemoselective alkylation of thiourea groups provides access to novel hetero-BUs.

Conclusions:

• The hypothesis regarding the inability of equatorial sulfur-containing BUs to form jigger conformations is confirmed.
• The study provides insights into the structure-property relationships of bambusurils.
• A new synthetic strategy for creating diverse bambusuril architectures is established.