Synthesis, isolation, and molecular structures of twelve new isomers of trifluoromethylfullerene C60(CF3)14

Abstract

Trifluoromethyl derivatives C₆₀(CF₃)₁₄ were synthesized by the reactions of fullerene C₆₀ or chlorofullerenes C₆₀Cl_n with gaseous CF₃I in glass ampoules at 400–450 °C. The chromatographic separation of isomers of C₆₀(CF₃)₁₄ was performed by a one- or two-step HPLC separation in hexane. Twelve out of 15 isomers were isolated for the first time. The molecular and crystal structures of the new isomers were determined by single-crystal X-ray diffraction analysis using synchrotron radiation. All isomers were characterized by MALDI mass spectrometry and UV—Vis absorption spectroscopy. The addition patterns of CF₃ groups on the fullerene cage are considered in detail taking into account the formation of structural units, such as isolated or almost isolated C=C bonds, unoccupied pentagons, skew pentagonal-pyramid addition patterns, the attachment of CF₃ groups in ortho positions, and benzenoid rings. The influence of different structural factors on the relative formation energy of the isomers (0.0–32.1 kJ mol⁻¹), which was calculated by the DFT method, was analyzed. The isomers of C₆₀(CF₃)₁₄ are the largest group of C₆₀ trifluoromethyl derivatives with known molecular structures.