Crystallographic Structure Determination of Both [5,6]- and [6,6]-Isomers of Lithium-Ion-Containing Diphenylmethano[60]fullerene

Organic functionalization of lithium-ion-containing [60]­fullerene, Li<sup>+</sup>@C<sub>60</sub>, was performed by using diphenyl­(diazo)­methane as a stable, readily available diazo compound to obtain lithium-ion-containing [5,6]- and [6,6]-diphenylmethano[60]­fullerenes, Li<sup>+</sup>@C<sub>61</sub>Ph<sub>2</sub>. The bis­(trifluoromethanesulfonyl)­imide (TFSI) salts of [5,6]- and [6,6]-Li<sup>+</sup>@C<sub>61</sub>Ph<sub>2</sub> were successfully separated by using a cation exchange column with eluent containing LiTFSI. Improved separation protocol and high crystallinity of ionic components in less polar solvents enabled separate crystallization of each isomer. Both [5,6]-open and [6,6]-closed structures of Li<sup>+</sup>@C<sub>61</sub>Ph<sub>2</sub> were determined by synchrotron radiation X-ray crystallography. Elucidating the [5,6]-open methano[60]­fullerene (fulleroid) structure will contribute to materials research on fulleroids.