Isolation and structure determination of missing fullerenes Gd@C 74 (CF 3 ) n through in situ trifluoromethylation

International audienc

Isolation and structure determination of missing fullerenes Gd@C 74 (CF 3 ) n through in situ trifluoromethylation

International audienc

Crystalline functionalized endohedral C60 metallofullerides

Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C₆₀ in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C₆₀ such as (metal)@C₈₂, and there are no reported purified C₆₀-based monomeric metallofullerenes, except for [Li@C₆₀]⁺(SbCl₆)⁻salt. Pure (metal)@C₆₀ compounds have not been obtained because of their extremely high chemical reactivity. One route to their stabilization is through chemical functionalization. Here we report the isolation, structural determination and electromagnetic properties of functionalized 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 presence of a weak antiferromagnetic coupling in Gd@C₆₀(CF₃)₅ crystals at low temperatures