Putting atoms and molecules into chemically opened fullerenes.

Area of Science:

• Supramolecular Chemistry
• Physical Chemistry
• Nanotechnology

Background:

• Fullerenes are carbon-based molecules with unique cage-like structures.
• Encapsulating atoms or molecules within fullerenes (endohedral fullerenes) is a key area of research.
• Understanding the dynamics of guest molecules inside fullerene cages is crucial for their applications.

Purpose of the Study:

• To investigate the encapsulation and release kinetics of various gas molecules within a chemically opened fullerene.
• To determine the equilibrium constants and reaction rates for guest-fullerene interactions.
• To elucidate the factors influencing the binding strength and dynamics of encapsulated species.

Main Methods:

• Gas adsorption and desorption measurements.
• Determination of equilibrium constants (Keq) for guest encapsulation.
• Kinetic studies to measure rate constants and activation energies for guest release.
• Analysis of pre-exponential factors in unimolecular dissociation reactions.

Main Results:

• Equilibrium constants (Keq) were measured for Argon (Ar), Krypton (Kr), Carbon Monoxide (CO), and Nitrogen (N2) interacting with fullerene 1.
• A particularly large Keq was observed for Ar, attributed to strong van der Waals attraction between Ar and the fullerene cage.
• Rate constants and activation energies for the unimolecular release of Ar, CO, and N2 from the fullerene were determined.
• Unusually small pre-exponential factors were found for these release reactions, suggesting loose binding of the guest molecules.

Conclusions:

• The study quantifies the thermodynamics and kinetics of gas encapsulation in a fullerene.
• Van der Waals forces play a significant role in the binding of noble gases like Ar within fullerene cages.
• The loose binding of guest molecules inside the fullerene cage influences the reaction dynamics, leading to small pre-exponential factors.