Trifluoromethylfullerenes have highly tunable electronic properties and can be used as adaptable building blocks for advanced organic electronics. Previously, our group has shown that the frontier orbitals of a series of C60(CF3) n are greatly influenced by the addition pattern of CF3 groups, which in turn, has a profound influence on electron affinities.1 Judicious additions of strong electron-withdrawing groups, such as CN or CF3, to fullerene cages are typically expected (and theoretically predicted) to increase electron affinity.Indeed, regioselective synthesis of a new SPP derivative with three unique addends, C60(CF3)4(CN)H, made possible due to the use of a new isomer of C60(CF3)4 as a substrate, resulted in the experimental and theoretical identification of a family of superhalogen fullerene radicals, species with the gas-phase electron affinity higher than that of the most electronegative halogens, F and Cl.2 The addition of one CN group to C60(CF3)4 increases the measured gas-phase electron affinity by more than 1 eV to 4.28(1) eV; such a large increase is likely due to a significant stabilization of the skew pentagonal pyramid pattern (SPP), and electron-withdrawing effect of CN group. In contrast, the measured electron affinity of another SPP open shell molecular species, C60(CF3)4H, is considerably lower, 3.96(1) eV.Regioselective cyanation of several C70(CF3) n compounds has also been carried out using recently described technique.3 In the case of C 1-C70(CF3)10, the addition of two CN groups results in an expected increase in the measured gas-phase electron affinity by 0.22 eV. Surprisingly, the addition of two electron-withdrawing CN groups to Cs -C70(CF3)8 results in a decrease in the measured gas-phase electron affinity! This decrease is observed for two different CN addition patterns. The underlying reasons and implications for the design of electrophilic fullerene derivatives are rationalized using DFT calculations.References 1 Popov, A. A.; Kareev, I. E.; Shustova, N. B.; Stukalin, E. B.; Lebedkin, S. F.; Seppelt, K.; Strauss, S. H.; Boltalina, O. V.; Dunsch, L. J. Am. Chem. Soc. 2007, 129, 11551. 2 Clikeman, T. T.; Deng, S. H. M.; Avdoshenko, S.; Wang, X.-B.; Popov , A. A.; Strauss, S. H.; Boltalina, O. V. Chem. Eur. J. 2013, 19, 15404. 3 Clikeman, T. T.; Kuvychko, I. V.; Shustova, N. B.; Chen, Y.-S.; Popov, A. A.; Boltalina, O. V.; Strauss, S. H. Chem. Eur. J. 2013, 19, 5070.