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Novel difluoromethylenated [70]fullerene derivatives, C70(CF2 )n (n=1-3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2 ) mono-adducts with [6,6]-open and [6,6]-closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X-ray analysis and high-level spectroscopic techniques. The [6,6]-open isomer of C70(CF2 ) constitutes the first homofullerene example of a non-hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2 ) isomers showed that it is substantially higher for the [6,6]-open isomer (the 70-electron π-conjugated system is retained) than the [6,6]-closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2 ) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter-conversion between the [6,6]-closed and [6,6]-open forms of a cage-modified fullerene driven by an electrochemical one-electron transfer. Thus, [6,6]-closed C70(CF2 ) constitutes an interesting example of a redox-switchable fullerene derivative.

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The structures of two bis-ethylpyrrolidinoadducts of Gd3N@I h -C80, obtained by regioselective 1,3-dipolar cycloadditions, were elucidated by single crystal X-ray, visible-near infrared (vis-NIR) spectra, studies on their thermal isomerization, and theoretical calculations. The structure of the minor-bis-adduct reveals a C 2-symmetric carbon cage with [6,6]­[6,6]-addition sites and with an endohedral Gd3N cluster that is completely flattened. This is the first example of a crystal structure of Gd3N@I h -C80 derivatives. The structure of the major-bis-adduct was inferred by the vis-NIR spectrum being corresponded to the structure of a previously reported major-bis-adduct of Y3N@I h -C80 known to have an asymmetric [6,6]­[6,6]-structure. Based on experimental results showing that the minor-bis-adduct of Gd3N@I h -C80 isomerized to the major-adduct, a possible second addition site was elucidated with support from density functional theory calculations.

Fullerene derivatives with >CH2 addends in [6,6]‐open or [5,6]‐closed configuration are uncommon of fullerene derivatives, but they are readily accessible via treatment of Cs‐C70(CF3)8 with diazomethane followed by thermolysis or photolysis. Both thermodynamic and kinetic factors favor regioselective addition of diazomethane at the near‐equatorial [5,6]‐double bond of Cs‐C70(CF3)8 to give a thermally labile pyrazoline intermediate. Thermal extrusion of N2 from the latter is a kinetically controlled process with orbital symmetry controlled Woodward–Hoffmann‐allowed mechanism. It quantitatively yields the less thermodynamically favorable [6,6]‐open isomer of C70(CF3)8[CH2] homofullerene, but the latter turns out to be capable of unexpectedly rapid quantitative phototransformation into the thermodynamically preferable [5,6]‐closed methanofullerene isomer. The transformation involves the manifold of the triplet states that facilitate the required cleavage of the Ccage–CH2 bonds.