Chemistry of difluoromethylenefullerenes

Difluoromethylenefullerenes belonging to structurally flexible bridged fullerene derivatives have a rare distinctive feature, viz., insertion of CF2 group into the C=C bond of the fullerene cage is accompanied by electrocyclic rearrangement with the formation of unusual products termed homofullerenes. This makes the electron-withdrawing properties more pronounced, has a decisive influence on the chemical properties of compounds in the neutral and anionic states, and facilitates cleavage of the C—C bond between the bridgehead carbon atoms. Depending on the local environment of the difluoromethylene group and on the charge state, the distance between the bridgehead carbon atoms in difluoromethylenefullerenes changes from 1.7 Å to 2.3 Å, which is accompanied by transformation of the cyclopropane moiety to the bridging fragment. Methods of synthesis, the molecular and electronic structure, chemical properties, and potential application fields of difluoromethylenefullerenes are considered.