Electrochemical behavior of C(60)(CF(2))(n), n = 1, 2 and C(60)(CCl(2)) has been investigated. [6,6]-Opened C(60)(CF(2)) and cis-2-C(60)(CF(2))(2) exhibit reversible reductions at potentials 150 and 145 mV more positive than C(60), unlike the related [6,6]-closed C(60)(CCl(2)), which shows reduction at the potential close to that for C(60). The structures, electron localization and lifetimes of the observed radical anions C(60)(CF(2))(-*) and cis-2-C(60)(CF(2))(2)(-*) have been elucidated by the ESR study and DFT calculations. The protonation pathway of decay of C(60)(CF(2))(-*) yields [6,6]-opened 1,9-dihydro-(1a,1a-difluoro-1aH-1(9)a-homo(C(60)-I(h))fullerene, C(60)(CF(2))H(2), which becomes the first characterized derivative of [6,6]-opened C(60)(CF(2)). DFT calculations of the structure and electron affinity of a number of homofullerene structures have been carried out to rationalize the experimental findings.

Difluoromethylenation of C60 with thermally decomposed CF2ClCO2Na provides novel C60(CF2) and C60(CF2)2 compounds with unique [6,6]-open structures. A theoretical survey of CF2 derivatives of C60 demonstrates that carbon cage opening can be controlled via charging of the molecule and that the thermodynamically preferable structures combine the trend to form open isomers with the compactness of the addition motifs, which results in the formation of windows in the fullerene cage.

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