Size matching and electrostatic potential as complementary methods for understanding the metallic cluster...

Area of Science:

• Inorganic Chemistry
• Materials Science
• Computational Chemistry

Background:

• Endohedral clusterfullerenes (ECFs) often explain internal cluster configuration by size matching.
• Trimetallic nitride (M3N) clusters are expected to relax in larger fullerenes.
• Experimental data shows Sc3N clusters are pyramidal in larger fullerenes (C84, C86), contradicting size-matching expectations.

Purpose of the Study:

• To investigate the factors governing internal cluster configurations in nitride ECFs.
• To explain the abnormal pyramidal shape of Sc3N clusters in larger fullerenes.
• To explore the role of electrostatic interactions in determining ECF structures.

Main Methods:

• Density functional theory (DFT) calculations for nine Sc3N@C2n (2n = 68, 70, 78-86) nitride clusterfullerenes.
• Reproduction of experimentally observed structural characteristics.
• Analysis of electrostatic potentials (ESPs) within the anionic empty cages (C2n^6-).

Main Results:

• DFT calculations successfully reproduced experimental structures.
• Internal cluster configurations correlate with ESP distributions within the cages.
• Electrostatic interactions drive Sc3+ cations to negative ESP regions and N3- anion to less negative regions.
• This results in planar or pyramidal shapes for the (Sc3N)6+ unit.

Conclusions:

• Electrostatic potentials (ESPs) inside the cages are crucial for determining internal cluster configurations in ECFs.
• The "spider effect" and size matching are insufficient explanations.
• ESPs offer a unified explanation for cluster shapes across various ECF types.
• Internal cluster shapes can be regulated by manipulating ESPs.