Electron affinities of [5,6]-open and [5,6]-closed adducts of trifluoromethylfullerene C_s-C₇₀(CF₃)₈: even one bond matters!

Highlights: • Crucial influence of open-closed skeletal transitions on the electronic properties of fullerene was demonstrated. • Electrochemically promoted switching of electronic properties based on disruption of the conjugated 62π-electron system into the isolated 32 and 28π-electron fragments upon closing the [5,6]-bond in question. • Regioselective near-equatorial cycloproponation of trifluoromethylfullerene C_s-C₇₀(CF₃)₈ was elaborated. • More compact alternatives promising molecular switching capabilities can be found within the family of pyramidalized polyenes. - Abstract: Despite trifluoromethylfullerene C_s-C₇₀(CF₃)₈ has a multitude of available reaction sites, [2 + 1] cycloaddition of CX₂ moieties (X = F and p-MeOC₆H₄) proceeds regioselectively at a particular [5,6]-bond. Depending on the nature of X, the resulting derivative can be either [5,6]-open (i.e., the said C−C bond is cleaved) or [5,6]-closed, and this structural detail, seemingly insignificant for a molecule that large, brings about a remarkable 0.6 eV difference in the electron affinity, as revealed by electrochemical studies. Synthesis, structural and electrochemical elucidation of the C₇₀(CF₃)₈(CX₂) compounds are discussed, as well as electrochemically promoted switching of the electronic properties based on disruption of the conjugated 62π-electron system into the isolated 32 and 28π-electron fragments upon closing the [5,6]-bond.