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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 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 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 in anionic C1-C70(CF3)10 promotes its dimerization in the condensed phase.

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Publication details

The article was received on 18 Nov 2018, accepted on 10 Jan 2019 and first published on 10 Jan 2019


Article type: Paper
DOI: 10.1039/C8NJ05847D
Citation: New J. Chem., 2019, Accepted Manuscript
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    Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene

    D. V. Konarev, S. S. Khasanov, A. A. Goryunkov, S. I. Troyanov, V. A. Brotsman, I. N. Ioffe and R. N. Lyubovskaya, New J. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C8NJ05847D

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