Structure of [60]fullerene with a mobile lithium cation inside

Abstract

The structure of crystalline [60]fullerene with a lithium cation inside (Li + @C 60 ) was determined by synchrotron radiation X-ray diffraction measurements to understand the electrostatic and thermal properties of the encapsulated Li + cation. Although the C 60 cages show severe orientation disorder in [Li + @C 60 ](TFPB − )·C 4 H 10 O and [Li + @C 60 ](TFSI − )·CH 2 Cl 2 , the Li + cations are rather ordered at specific positions by electrostatic interactions with coordinated anions outside the C 60 cage. The Li + @C 60 molecules in [Li + @C 60 ](ClO 4 − ) with a rock-salt-type cubic structure are fully disordered with almost uniform spherical shell charge densities even at 100 K by octahedral coordination of ClO 4 − tetrahedra and show no orientation ordering, unlike [Li + @C 60 ](PF 6 − ) and pristine C 60 . Single-bonded (Li + @C 60 − ) 2 dimers in [Li + @C 60 − ](NiOEP)⋅CH 2 Cl 2 are thermally stable even at 400 K and form Li + –C bonds which are shorter than Li + –C bonds in [Li + @C 60 ](PF 6 − ) and suppress the rotational motion of the Li + cations.