Isolation of the simplest hydrated acid

Area of Science:

• Supramolecular Chemistry
• Physical Chemistry
• Materials Science

Background:

• Acid dissociation in aqueous media is fundamental but poorly understood at the molecular level.
• Fullerenes offer unique nanoscale environments for encapsulating molecular species.

Purpose of the Study:

• To investigate the encapsulation of hydrogen fluoride (HF) and water (H2O) within a fullerene C70 derivative.
• To elucidate the molecular-level details of solvation and hydrogen bonding in confined environments.

Main Methods:

• High-pressure treatment of an open-cage fullerene C70 derivative with HF and H2O.
• Single crystal X-ray diffraction for structural determination of the H2O·HF complex.
• Nuclear Magnetic Resonance (NMR) spectroscopy to analyze molecular interactions and bonding.

Main Results:

• Successful encapsulation of H2O·HF and H2O molecules within the C70 fullerene cage, forming endohedral fullerenes (H2O·HF)@C70, H2O@C70, and HF@C70.
• Unambiguous structural determination of the H2O·HF complex via X-ray diffraction.
• NMR evidence confirmed a stable hydrogen bond between H2O and HF without proton transfer, even at elevated temperatures (140°C).

Conclusions:

• The study demonstrates a novel method for encapsulating molecular complexes within fullerenes, providing insights into confined solvation.
• The synergistic 'push-pull' mechanism facilitates the encapsulation of the H2O·HF complex.
• The findings reveal stable hydrogen bonding in a confined fullerene environment, relevant to understanding acid-base chemistry.