SCHEDULED MAINTENANCE
Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene†
Abstract
Salts of fullerene derivative C1-C70(CF3)10 and bare fullerene C70 with cryptates of alkali metals as cations have been obtained: {cryptand[2.2.2](K+)}2[C70(CF3)10−]2·Solvent (1), {cryptand[2.2.2](K+)}2(C70−)2·Solvent (2) and {cryptand[2.2.1](Na+)}2(C70−)2·3C6H4Cl2 (3) in the form of single crystals. Radical anions of both functionalized and bare fullerene C70 form diamagnetic and EPR silent singly-bonded [C70(CF3)10−]2 and (C70−)2 dimers stable at least up to room temperature (according to the EPR data). The length of the intercage C–C bonds and the center-to-center interfullerene distances are 1.570(7) and 10.516 Å for the [C70(CF3)10−]2 dimer in 1 and 1.576(4)–1.587(4) Å and 10.493–10.507 Å for the (C70−)2 dimers in 2 and 3. Optical spectra of 1–3 manifest new bands in the NIR range characteristic of negatively charged fullerenes. These bands are blue shifted in the spectrum of 1 with [C70(CF3)10−]2 in comparison with the spectrum of underivatized C70˙−. It is shown that negatively charged fullerene dimers show new low-energy broad absorption bands in the NIR range most probably associated with charge transfer between fullerene anions within the dimers. According to DFT calculations, the singly-bonded [C70(CF3)10−]2 dimer demonstrates negative binding energy in the gas phase, but becomes bound by 54 kJ mol−1 when the solvent effects are taken into account via the D-PCM model. Charge asymmetry incurred by CF3 groups at the pole region of anionic C1-C70(CF3)10 promotes its dimerization in the condensed phase.
![Graphical abstract: Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene](/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=C8NJ05847D&imageInfo.ImageIdentifier.Year=2019)
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