Dynamic chiral cyclohexanohemicucurbit[12]uril.

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry
• Physical Chemistry

Background:

• Cyclic host molecules like cucurbiturils are crucial in supramolecular chemistry.
• Understanding the conformational dynamics of macrocycles is key to their application.
• Chiral variants offer unique possibilities in molecular recognition and catalysis.

Purpose of the Study:

• To investigate the solution-state conformation and dynamics of chiral cyclohexanohemicucurbit[12]uril.
• To elucidate the temperature-dependent structural changes and their impact on the macrocyclic cavity.
• To combine experimental NMR data with theoretical DFT calculations for comprehensive analysis.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study the molecule in solution.
• Density Functional Theory (DFT) modeling was used to predict and interpret structural and dynamic properties.
• Variable-temperature NMR experiments were conducted to probe conformational transitions.

Main Results:

• The macrocycle adopts a stable concave octagonal shape in solution.
• Two distinct temperature-dependent conformational flexibilities were identified: methylene bridge flipping (above 265 K) and urea monomer rotation (above 308 K).
• These dynamic processes lead to a loss of the confined space within the macrocycle at elevated temperatures.

Conclusions:

• Chiral cyclohexanohemicucurbit[12]uril displays significant conformational flexibility in solution.
• The identified dynamic transitions are critical for understanding its host-guest chemistry and potential applications.
• The study provides fundamental insights into the behavior of complex macrocyclic structures.