Selective Synthesis of a Trifluoromethylated Fullerene and the Crystal Structure of C₆₀(CF₃)₁₂

Abstract

Unerwartete Selektivität: [60]Fulleren reagiert mit CF3I bei 440 °C selektiv zu C60(CF3)12. In dessen S6‐Isomer bilden die zwölf CF3‐Gruppen eine kontinuierliche Schleife alternierender para‐ und meta‐C6(CF3)2‐Sechsecke. Stapelwechselwirkungen und Abschirmeffekte der CF3‐Gruppen in der Kristallpackung bewirken eine Stärkung der Molekülketten, was die geringe Flüchtigkeit und Löslichkeit der Verbindung erklärt.

Synthesis, Spectroscopic and Electrochemical Characterization, and DFT Study of Seventeen C70(CF3)n Derivatives (n=2, 4, 6, 8, 10, 12)

“…We recently reported the X-ray structure of a C 1 isomer of [22] made with CF 3 I at high temperature, that is 39 kJ mol À1 higher in energy (using the same DFT code and functional [22] ) than the S 6 isomer of this composition, [9,18] the X-ray structure of which has also been reported. [18] This represents the least thermodynamically stable fullereneA C H T U N G T R E N N U N G (CF 3 ) n derivative isolated to date (i.e., the highest energy isomer of a given fullereneA C H T U N G T R E N N U N G (CF 3 ) n composition). Before C 1 -C 60 12 was reported, the highest energy isomer that had been isolated was C s -C 60 A C H T U N G T R E N N U N G (CF 3 ) 6 , [23] which was predicted to be only 14.4 kJ mol À1 higher in energy than the C 1 isomer.…”

“…[a] The first five rows refer to syntheses carried out using reactor 1; the last two rows refer to syntheses carried out using reactor 2 (see Experimental Section for details). [1][2][3][4][5][6][7][8][9][10][11][18][19][20][21][22] ii) CF 3 groups on contiguous cage carbon atoms are rare for n = 2-12 (only one example out of 38 well-characterized compounds before this work; [23] this example is also the only case of three CF 3 groups sharing the same hexagon for n = 2-12-note that all fullerenes have precisely 12 pentagons); iii) two CF 3 groups sharing the same pentagon (i.e., a 1,3-C 5 A C H T U N G T R E N N U N G (CF 3 ) 2 pentagon) are rare for n = 2-12 derivatives (only two examples [5,22] out of 38 wellcharacterized compounds); iv) terminal CF 3 groups, and CF 3 groups on isolated C 6 A C H T U N G T R E N N U N G (CF 3 ) 2 hexagons, have always been found to be para to their nearest-neighbor CF 3 group, never meta (but see below); v) stable exohedral fullerene(X) n derivatives with substituents on triple-hexagon junctions and without endohedral atoms are unknown for n < 38 (the only known example for C 70 is C 70 F 38 [24] ); vi) J FF coupling between CF 3 groups is only observed for proximate CF 3 groups on the same hexagon or pentagon; [1,5,9,[25][26][27] vii) the 6 J FF and 7 J FF values for m- 2 hexagons, respectively, depend upon the F···F distance between the CF 3 groups and on the F-C···C-F torsion angle (shorter distances and larger torsion angles lead to larger J FF values); [1,9,27] and viii) 19 F NMR Àd values for the CF 3 multiplets are less than 60 ppm only when the corresponding CF 3 groups are eclipsed or nearly eclipsed. [5,9,<...>…”

Preparation, Crystallographic Characterization, and Theoretical Study of C70(CF3)14

“…[6] In addition, the first selective synthesis of a trifluoromethylated C 60 (CF 3 ) 12 molecule and determination of its molecular and crystal structure have recently been reported. [9] Here we report the isolation, X-ray crystallographic characterization, and theoretical study of four C 70 (CF 3 ) 14 isomers that continue the series of well characterized trifluoromethylated C 70 derivatives with sequentially growing number of CF 3 groups.…”

ESR‐Vis/NIR Spectroelectrochemical Study of C70(CF3)2−. and C70(C2F5)2−. Radical Anions

“…[25] Since derivatives of fullerene(R f ) n compounds may be used as electronacceptor components of photovoltaic assemblies in the near future, detailed studies of the frontier orbitals and Vis-NIR transitions of their radical anions are essential. We previously reported (1) Vis-NIR transitions for C 60 A C H T U N G T R E N N U N G (CF 3 ) 2 À C, C 60 A C H T U N G T R E N N U N G (CF 3 ) 2 2À , and C 60 A C H T U N G T R E N N U N G (CF 3 ) 10 À C [22] and (2) that radical-anion ESR spectra can provide meaningful information about the electron distribution in the singly occupied molecular orbitals (SOMOs) of C 60 A C H T U N G T R E N N U N G (CF 3 ) 4 À C and C 60 A C H T U N G T R E N N U N G (CF 3 ) 10 À C (i.e. the LUMOs of the neutral derivatives).…”

“…Recent developments in fullerene perfluoroalkylation methodologies have resulted in the isolation and structural characterization of more than 40 CF 3 derivatives and 9 C 2 F 5 derivatives of C 60 , [1][2][3][4][5][6][7][8][9] C 70 [10][11][12][13][14][15][16][17][18][19] and higher fullerenes. [20,21] Due to the electron-withdrawing nature of perfluoralkyl groups, most, but not all, C 60,70 A C H T U N G T R E N N U N G (CF 3 ) n compounds are stronger electron acceptors than their parent fullerenes.…”