A layered ionic crystal of polar Li@C60 superatoms

Abstract

If the physical properties of C₆₀ fullerene molecules can be controlled in C₆₀ products already in use in various applications, the potential for industrial development will be significant. Encapsulation of a metal atom in the C₆₀ fullerene molecule is a promising way to control its physical properties. However, the isolation of C₆₀-based metallofullerenes has been difficult due to their insolubility. Here, we report the complete isolation and determination of the molecular and crystal structure of polar cationic Li@C₆₀ metallofullerene. The physical and chemical properties of Li@C₆₀ cation are compared with those of pristine C₆₀. It is found that the lithium cation is located at off-centre positions in the C₆₀–I_h cage interior and that the [Li⁺@C₆₀] salt has a unique two-dimensional structure. The present method of purification and crystallization of C₆₀-based metallofullerenes provides a new C₆₀ fullerene material that contains a metal atom.