Crystalline C60 fulleride with metal inside

TL;DR

This study reports the first successful isolation and structural analysis of crystalline C60-based metallofullerenes with encapsulated Gd and La atoms, revealing their unique properties and potential superconductivity.

Contribution

It presents the first purified crystalline C60 metallofullerenes with encapsulated Gd and La, including structural and electromagnetic characterization, expanding understanding of metallofullerene chemistry.

Findings

Gd@C60(CF3)5 and La@C60(CF3)5 were successfully isolated and structurally confirmed.

The HOMO-LUMO gaps of these metallofullerenes are significantly increased by CF3 groups.

Weak antiferromagnetic coupling observed in Gd@C60(CF3)3 at low temperatures.

Abstract

Endohedral metallofullerenes have been extensively studied, since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, all of these studies have been carried out on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based metallofullerenes except for [Li@C60]+(SbCl6)- salt. Pure (metal)@C60 has not been obtained because of their extremely high chemical reactivity. We report here the first isolation, structural determination and electromagnetic properties of crystalline C60-based metallofullerenes, Gd@C60(CF3)5 and La@C60(CF3)5. Synchrotron X-ray single-crystal diffraction reveals that La and Gd atoms are indeed encapsulated in the Ih-C60 fullerene. The HOMO-LUMO gaps of Gd@C60 and La@C60 are significantly widened by an order of magnitude with addition of CF3- groups. Magnetic measurements show the presense of a weak antiferromagnetic coupling in Gd@C60(CF3)3 crystals at low temperatures. Gd@C60 and La@C60 might exhibit superconductivity as the electronic structures resemble those of superconducting alkali-doped C60 fullerides.