CF₂‐Functionalized Trifluoromethylated Fullerene C₇₀(CF₃)₈(CF₂): Structure, Electronic Properties, and Spontaneous Oxidation at the Bridgehead Carbon Atoms

Abstract

Thermally-induced CF 2 addition to C s -C 70 (CF 3 ) 8 upon reaction with sodium chlorodifluoroacetate is found to proceed via the nucleophilic cyclopropanation pathway, possibly with a certain involvement of the alternative singlet carbene pathway. Of the two major isomers of C 70 (CF 3 ) 8 (CF 2 ) characterized by X-ray diffraction and spectroscopically, the less abundant one has a [6,6]-open structure whereas the more abundant product is a [5,6]-open isomer with highly reactive bridgehead sites. Under ambient conditions, its rapid oxidation and hydration produce C 70 (CF 3 ) 8 [CF 2 ](OH) 2 and C 70 (CF 3 ) 8 [CF 2 ](OH)H, respectively, in which the π-system is split in two disjoint caps and the HOMO-LUMO gap is considerably increased, as evidenced by the blue-shifted fluorescence.

Reversibly switchable methanofullerene by photoexcitation and reduction

“…485 nm. 13 In the same time, red emission peak at 700 nm was reported for the [5,6]-open C 70 (CF 3 ) 8 [CF 2 ] 11 (Fig. 2d).…”

“…Thus, compared to the parent C s -C 70 (CF 3 ) 8 with the absorption edge at 630 nm, 7 splitting of the π-system blue-shifts the red absorption edge by ca. 150–170 nm in the molecules with [X] = H 2 , 8 Cl 2 , 9 (CN) 2 , 10 CH 2 , 6 and [CF 2 ](OH)H. 11…”

“…The other known C s -C 70 R 8 [X] compounds, [X] denoting the combination of the addends at the [5,6]-bond, divalent or tetravalent on aggregate (in the latter case the bond being inevitably cleaved), rather show blue emission due to the above discussed splitting of their p-system into smaller fragments. For example, C 70 (CF 3 ) 8 [CF 2 ](OH)H emits at 465 nm 11 and C 70 (OMe) 8 [X], X = O, (OH) 2 , [O](OAc) 2 , at ca. 485 nm.…”

Para‐C60(CF2)(CF3)R: a family of chiral electron accepting compounds accessible through a facile one‐pot synthesis

“…To discriminate between these two mechanisms, we studied two cases: (i) nucleophilic trifluoromethylation of individual C 60 (CF 2 ) during the thermolysis of CF 3 COOCs and (ii) difluoromethylenation of C 60 (CF 3 ) − [deprotonated C 60 (CF 3 )H] via the thermolysis of CF 2 ClCOONa (which is a known difluoromethylenation agent for fullerenes and their derivatives) [11–13] . HPLC‐MS traces of the acidified product mixtures of these reactions are shown on Figure 2(e, g).…”

Oxidative cage opening in the C70 fullerene facilitated by preceding trifluoromethylation

“…Compared to the parent C s -C 70 (CF 3 ) 8 , they demonstrate broadening of the HOMO–LUMO gap, which is likely due to effective decoupling of the two halves of the conjugated system of the molecule. The absorption edge of 2a and 2b is found at, respectively, 514 and 485 nm, or 2.4 and 2.6 eV ( vs. 2.1 eV for C s -C 70 (CF 3 ) 8 35 ). The fluorescence spectra of 2a and 2b were recorded in cyclohexane with the excitation at 355 nm.…”