An H₂ O₂ Molecule Stabilized inside Open-Cage C₆₀ Derivatives by a Hydroxy Stopper

Area of Science:

• Supramolecular Chemistry
• Nanotechnology
• Physical Chemistry

Background:

• Fullerene derivatives offer unique cage structures for molecular encapsulation.
• Controlling the internal environment of nanocapsules is crucial for stabilizing guest molecules.
• Hydrogen peroxide (H₂O₂) is a reactive molecule requiring stabilization for various applications.

Purpose of the Study:

• To isolate hydrogen peroxide (H₂O₂) molecules within hydroxylated open-cage fullerene derivatives.
• To investigate the structural and bonding interactions of encapsulated H₂O₂.
• To achieve high encapsulation ratios and prevent H₂O₂ escape.

Main Methods:

• Synthesis of hydroxylated open-cage fullerene derivatives.
• Encapsulation of H₂O₂ via mixing with a precursor and reduction.
• Structural characterization using ¹H NMR spectroscopy, X-ray analysis, and DFT calculations.
• Isolation of specific isomers using High-Performance Liquid Chromatography (HPLC).

Main Results:

• Two structural isomers of H₂O₂@open-fullerenes were obtained based on the reduction site.
• A high encapsulation ratio of 81% was achieved at low temperatures.
• Strong hydrogen bonding was observed between encapsulated H₂O₂ and the fullerene's hydroxyl group.
• The hydroxyl group acted as a kinetic stopper, and hydrogen bonding provided thermodynamic stabilization, preventing H₂O₂ escape.
• HPLC isolation yielded H₂O₂@open-fullerene with a 100% encapsulation ratio, likely due to intramolecular hydrogen bonding.

Conclusions:

• Hydroxylated open-cage fullerenes can effectively encapsulate and stabilize hydrogen peroxide.
• Hydrogen bonding plays a critical role in both the encapsulation process and the long-term stability of H₂O₂ within the fullerene cage.
• The developed method offers a promising route for storing and handling reactive molecules like H₂O₂.