Stabilization of High-Energy Metallic Clusters via Superatom Formation Inside Fullerenes

Area of Science:

• Computational chemistry
• Materials science
• Nanotechnology

Background:

• Labile cluster isomers are typically unstable due to high energies.
• Fullerene cages can encapsulate various species, forming endohedral clusterfullerenes (ECFs).

Purpose of the Study:

• To investigate the stabilization of high-energy metal cluster isomers within fullerene cages.
• To explore the formation and properties of endohedral clusterfullerenes (ECFs) using computational methods.
• To identify potential new ECFs with high synthesis potential.

Main Methods:

• Density functional theory (DFT) calculations.
• Coupled cluster (CC) calculations.
• Analysis of electronic structure and relative energies of isolated clusters and ECFs.

Main Results:

• Certain high-energy isomers of Ti3C3, Sc4C3, and Ti3B4 clusters are stabilized within fullerene cages.
• Upon encapsulation and electron transfer, these clusters form "superatoms" with 18 valence electrons, significantly lowering their energy.
• Three ECFs (Sc4C3@Ih(7)-C80, Ti3C3@Ih(7)-C80, and Ti3C3@C2v(9)-C82) were experimentally confirmed.
• Ti3B4@Ih(7)-C80 is predicted as a promising new boride ECF.

Conclusions:

• Fullerene confinement is an effective strategy for stabilizing high-energy metastable clusters.
• The "superatom" electronic configuration within ECFs is key to their stability.
• This research provides guidelines for designing novel ECFs and cautions against using only the most stable free clusters in theoretical models of metallofullerene catalysts.