ИСТИНА

Trifluoromethylated fullerenes are of interest for studying their molecular and electronic properties due to a large structural diversity of this family of fullerene derivatives with varying number of addends and addition patterns. In particular, electrochemical behavior of a number of individual lower trifluoromethylated fullerenes C70(CF3)2–12, being comparatively easier isolated and purified, are yet investigated by Popov A.A. and co-workers.1 Here we report electrochemical properties of a variety of individual isomers of higher trifluoromethylated derivatives C70(CF3)12–20. A mixture of higher trifluoromethylated fullerenes C70(CF3)12–20 was synthesized according to standard procedure.2 Contrary to previous works,3,4 here we report another strategy for HPLC separation of the obtained mixture including utilization of several HPLC columns with different stationary phases. Thereby, individual isomers of C70(CF3)12, C70(CF3)14, C70(CF3)16 (4 isomers), C70(CF3)18 (5 isomers) and C70(CF3)20 (2 isomers) were isolated in sufficient quantities. Notably, structures of three novel compounds: two isomers of С70(CF3)18 and one isomer of С70(CF3)16, were determined by single-crystal X-ray diffraction analysis. Molecular structures of previously characterized compounds: С70(CF3)20,3 C70(CF3)18 (2 isomers)3,4, С70(CF3)12,2 and C70(CF3)14,5 were also confirmed by means of single-crystal XRD studies. Electrochemical properties of the obtained individual isomers of higher trifluoromethylated [70]fullerenes were studied by means of cyclic voltammetry. Most of investigated compounds exhibited reversible one-electron reduction. Similar to lower trifluoromethylated fullerenes,1 the values of first reduction potential, and therefore electron affinity, of studied C70(CF3)12–20 are significantly dependent on addition pattern of CF3 groups and in a less degree on number of addends. Energies of frontier molecular orbitals of compounds under study were estimated using electrochemical and electronic spectra data.