Synthesis, Structure, and Theoretical Study of Trifluoromethyl Derivatives of the IPR Isomer of C₈₄ Fullerene, C₈₄(11)(CF₃)_10,12,14

Abstract

C84 is the most abundant higher fullerene which is present in the arc‐discharge fullerene soot. Among 24 topologically possible Isolated‐Pentagon Rule isomers of C84, two major isomers, C84(22) and C84(23), and several minor ones have been identified experimentally. We report the synthesis, HPLC isolation, and synchrotron X‐ray structure elucidation of trifluoromethyl derivatives of the most abundant minor isomer of C84, C84(11)(CF3)10,12,14. The experimentally determined addition patterns are discussed in terms of the attachments in ribbons of edge‐sharing para C6(CF3)2 hexagons and the uniform distribution of CF3 groups on the C2‐C84(11) carbon cage. A general scheme of C84(11) trifluoromethylation pathways was proposed on the basis of theoretical DFT calculations of formation energies. Thus, trifluoromethylation pathways are now discussed in details for five different isomers of C84.

Synthesis, Isolation, and Structural Study of Trifluoromethyl Derivatives of the IPR Isomer of C84 Fullerene, C84(11)(CF3)14,16,18

“…The sublimate was dissolved in toluene and subjected to HPLC separation in toluene or toluene/ n ‐hexane mixtures. Some HPLC fractions isolated from the residue gave crystals of C 84 (11)(CF 3 ) 10,12,14 as reported previously [8] . Several fractions obtained via multi‐stage HPLC separation (including a recycling HPLC) of the sublimate afforded crystals by slow concentration or recrystallization from other solvents.…”

“…The early stages of high‐temperature trifluoromethylation of C 84 (11) by consecutive addition of CF 3 groups up to C 84 (11)(CF 3 ) 12 have been considered in the previous report [8] . It was shown that both experimentally isolated C 84 (11)(CF 3 ) 10 ‐I and C 84 (11)(CF 3 ) 12 ‐I are the most stable isomers of a given composition.…”

“…[6d,7] The addition pattern of the only reported isomer C 84 (11)(CF 3 ) 14 -I is characterized by a simple addition of two CF 3 groups to C 84 (11)(CF 3 ) 12 -I. [8] In this work, four other isomers, C 84 (11)(CF 3 ) 14 -II-V, have been isolated and structurally characterized. Their molecular structures are shown in Figure 1.…”

“…Some HPLC fractions isolated from the residue gave crystals of C 84 (11)(CF 3 ) 10,12,14 as reported previously. [8] Several fractions obtained via multi-stage HPLC separation (including a recycling HPLC) of the sublimate afforded crystals by slow concentration or recrystallization from other solvents. The crystals obtained were studied by X-ray crystallography with the use of synchrotron radiation.…”

“…Systematic experimental and theoretical studies have been performed for major isomers, C 84 (22) and C 84 (23), as well as for two minor isomers, C 84 (16) and C 84 (18) [7] . Recently, we reported the use of the same approach for C 84 (11)(CF 3 ) n in the range of n =2–12 [8] …”