Despite trifluoromethylfullerene Cs-C-70(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 C-70(CF3)(8)(CX2) compounds are discussed, as well as electrochemically promoted switching of the electronic properties based on disruption of the conjugated 62 pi-electron system into the isolated 32 and 28 pi-electron fragments upon closing the [5,6]-bond. (C) 2016 Published by Elsevier Ltd.