Synthesis, Structure, and Theoretical Study of Trifluoromethyl Derivatives of C₈₄(23) Fullerene

Abstract

Trifluoromethylation of a higher fullerene mixture with CF3I was performed in ampoules at 550 °C. HPLC separation followed by crystal growth and X-ray diffraction study resulted in the structure elucidation of nine CF3 derivatives of D2d-C84 (isomer 23). The molecular structures of C84(23)(CF3)4, C84(23)(CF3)8, C84(23)(CF3)10, C84(23)(CF3)12, two isomers of C84(23)(CF3)14, two isomers of C84(23)(CF3)16, and C84(23)(CF3)18 were discussed in terms of their addition patterns and the relative formation energies. Extensive theoretical DFT calculations were performed to identify the most stable molecular structures. It was found that the addition of CF3 groups to the C84(23) fullerene is governed by two main rules: no additions in positions of triple hexagon junctions and predominantly para additions in C6(CF3)2 hexagons on the fullerene cage. The only exception with an isolated CF3 group in C84(23)(CF3)12 is discussed in more detail.

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

“…Although the carbon cages of C 2v -C 78 (2) and C 2v -C 78 (3) differ by the position of only one C-C bond [2], the addition patterns of the derivatives with equal numbers of CF 3 groups, C 78 (2,3)(CF 3 ) 12 , differ significantly. A similar phenomenon has also been found for (CF 3 ) 12 derivatives of isomers C 84 (22) and C 84 (23), which also differ by the position of one bond on the carbon cages [16,17]. In contrast, the addition patterns of C 78 X 18 (X = Cl, Br) are the same for isomers C 78 (2), C 78 (3), and even C 78 (5) [8][9][10][11] which give rise to co-crystallization phenomena for these halides [8,11] thus demonstrating the levelling effect for a large number of addends on the addition patterns of fullerene derivatives with similar carbon cages.…”

“…Two different starting higher fullerene mixtures were used for trifluoromethylation with gaseous CF 3 I in quartz ampules following a previously described procedure [16][17][18]. The mixture of higher fullerenes C 76 -C 96 (45 mg; MER Corp.) was trifluoromethylated at 560…”

Synthesis and structures of trifluoromethyl derivatives of fullerenes C84(16) and C84(18)

“…5 After wards, the use of X ray diffraction method for the deter mination of the cage structures of fullerenes (only for C s C 84 (14) 7 ) or their derivatives confirmed the existence of all the indicated isomers except C 84 (19) and C 84 (24). The presence in the mixtures of C 2v C 84 (18) isomer was confirmed 8 by the crystal and molecular structures of its C 84 (18)(C 2 F 5 ) 12 derivative.…”

“…17) and C 84 (23)(CF 3 ) 4-18 (see Ref. 18) became available, which in combination with calculations of relative stabili ties allowed one to suggest the schemes of sequential addi tion of pairs of CF 3 groups to the fullerene cage. It was found that trifluoromethylated C 84 (22) and C 84 (23) iso mers have not only similar addition patterns, but also con siderable differences due to the different structures of their carbon cages.…”

“…The present work is devoted to the synthesis, separa tion, and determination of molecular structures of tri fluoromethyl derivatives of two minor isomers C s C 84 (16) and C 2v C 84 (18). The compounds of the formulas C 84 (16)(CF 3 ) 2m (2m = 8, 10,12,14,18) and C 84 (18)(CF 3 ) 2m (2m = 10, 12) were isolated and characterized by X ray diffraction method for the first time.…”