Thermally Stable Perfluoroalkylfullerenes with the Skew-Pentagonal-Pyramid Pattern:  C₆₀(C₂F₅)₄O, C₆₀(CF₃)₄O, and C₆₀(CF₃)₆

Abstract

Reaction of C(60) with CF(3)I at 550 degrees C, which is known to produce a single isomer of C(60)(CF(3))(2,4,6) and multiple isomers of C(60)(CF(3))(8,10), has now been found to produce an isomer of C(60)(CF(3))(6) with the C(s)-C(60)X(6) skew-pentagonal-pyramid (SPP) addition pattern and an epoxide with the C(s)-C(60)X(4)O variation of the SPP addition pattern, C(s)-C(60)(CF(3))(4)O. The structurally similar epoxide C(s)-C(60)(C(2)F(5))(4)O is one of the products of the reaction of C(60) with C(2)F(5)I at 430 degrees C. The three compounds have been characterized by mass spectrometry, DFT quantum chemical calculations, Raman, visible, and (19)F NMR spectroscopy, and, in the case of the two epoxides, single-crystal X-ray diffraction. The compound C(s)-C(60)(CF(3))(6) is the first [60]fullerene derivative with adjacent R(f) groups that are sufficiently sterically hindered to cause the (DFT-predicted) lengthening of the cage (CF(3))C-C(CF(3)) bond to 1.60 A as well as to give rise to a rare, non-fast-exchange-limit (19)F NMR spectrum at 20 degrees C. The compounds C(s)-C(60)(CF(3))(4)O and C(s)-C(60)(C(2)F(5))(4)O are the first poly(perfluoroalkyl)fullerene derivatives with a non-fluorine-containing exohedral substituent and the first fullerene epoxides known to be stable at elevated temperatures. All three compounds demonstrate that the SPP addition pattern is at least kinetically stable, if not thermodynamically stable, at temperatures exceeding 400 degrees C. The high-temperature synthesis of the two epoxides also indicates that perfluoroalkyl substituents can enhance the thermal stability of fullerene derivatives with other substituents.

Synthesis, isolation, and X-ray structural characterization of trifluoromethylated C78 fullerenes: C78(2)(CF3)10/12 and C78(3)(CF3)12/14

“…This effect can be explained by the increase of the compound volatility with the increasing number of CF 3 groups which influences the kinetics of sublimation in the reaction ampoule [19].…”

“…Among the most structurally investigated compounds are the bromides, C 78 (2,3)Br 18 [8], chlorides, C 78 (2,3,5)Cl 18 [9][10][11] and C 78 (1,2)Cl 30 [12,13], and several trifluoromethylated derivatives, C 78 (CF 3 ) 2n [14]. For the latter group, structural data obtained by 19 F NMR spectroscopy and/or X-ray studies are available for compositions C 78 (3)(CF 3 ) 8 , C 78 (1,2)(CF 3 ) 10 , and C 78 (3,5)(CF 3 ) 12 . The only structural X-ray study of a pentafluoroethyl derivative concerns the compound C 78 (2)(C 2 F 5 ) 10 [15].…”

Nitrogen Directs Multiple Radical Additions to the 9,9′‐Bi‐1‐aza(C60‐Ih)[5,6]fullerene: X‐ray Structure of 6,9,12,15,18‐C59N(CF3)5

“…The absence of terminal CF 3 groups (seen as quartets in the 19 F NMR spectra) implies that five CF 3 groups should be arranged in a para 5 (or p 5 ) loop rather than as a ribbon of edge-sharing p-C 6 (CF 3 ) 2 hexagons as most commonly observed in the C 60 (CF 3 ) n compounds. [5] The absorption spectrum (see the Supporting Information) is similar to that of C s -C 60 (CF 3 ) 6 . [6] The most probable addition pattern that agrees with the spectroscopic data and was previously observed for azafullerenes features an isolated pyrrole moiety on the fullerene core ( Figure 1).…”

“…[5] The absorption spectrum (see the Supporting Information) is similar to that of C s -C 60 (CF 3 ) 6 . [6] The most probable addition pattern that agrees with the spectroscopic data and was previously observed for azafullerenes features an isolated pyrrole moiety on the fullerene core ( Figure 1). [7] Interestingly, C 60 X 6 compounds with a similar addition pattern of skew-pentagonal pyramid (SPP) are formed abundantly, if not regioselectively, in various room-temperature reactions (see references in the Supporting Information).…”

“…[7] Interestingly, C 60 X 6 compounds with a similar addition pattern of skew-pentagonal pyramid (SPP) are formed abundantly, if not regioselectively, in various room-temperature reactions (see references in the Supporting Information). However, SPP-C s -C 60 (CF 3 ) 6 was found only as a minor isomer in the high-temperature synthesis, whereas C 1 -C 60 -(CF 3 ) 6 with a ribbon addition pattern (para 3 -meta-para; p 3 mp) was at least ten times more abundant. [5,6] The C s isomer is also 14.4 kJ mol À1 less stable than p 3 mp-C 1 -C 60 (CF 3 ) 6 at the DFT Figure 1.…”