A faux hawk fullerene with PCBM-like properties [electronic resource].
- Washington, D.C. : United States. Dept. of Energy, 2014. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Additional Creators:
- Pacific Northwest National Laboratory (U.S.), United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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- Free-to-read Unrestricted online access
- Reaction of C<sub>60</sub>, C<sub>6</sub>F<sub>5</sub>CF<sub>2</sub>I, and SnH(n-Bu)3 produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C<sub>60</sub>(CF<sub>2</sub>C<sub>6</sub>F<sub>5</sub>)H (1) and 1,9-C<sub>60</sub>(cyclo-CF2(2-C<sub>6</sub>F<sub>4</sub>)) (2). The highest isolated yield of 1 was 35% based on C<sub>60</sub>. Depending on the reaction conditions, the relative amounts of 1 and 2 generated in situ were as high as 85% and 71%, respectively, based on HPLC peak integration and summing over all fullerene species present other than unreacted C<sub>60</sub>. Compound 1 is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 °C but was rapidly converted to 2 upon addition of Sn<sub>2</sub>(n-Bu)<sub>6</sub> at this temperature. In contrast, complete conversion of 1 to 2 occurred within minutes, or hours, at 25 °C in 90/10 (v/v) PhCN/C<sub>6</sub>D<sub>6</sub> by addition of stoichiometric, or sub-stoichiometric, amounts of proton sponge (PS) or cobaltocene (CoCp<sub>2</sub>). DFT calculations indicate that when 1 is deprotonated, the anion C<sub>60</sub>(CF<sub>2</sub>C<sub>6</sub>F<sub>5</sub>)<sup>-</sup> can undergo facile intramolecular S<sub>N</sub>Ar annulation to form 2 with concomitant loss of F<sup>-</sup>. To our knowledge this is the first observation of a fullerene-cage carbanion acting as an SNAr nucleophile towards an aromatic C–F bond. The gas-phase electron affinity (EA) of 2 was determined to be 2.805(10) eV by low-temperature PES, higher by 0.12(1) eV than the EA of C<sub>60</sub> and higher by 0.18(1) eV than the EA of phenyl-C<sub>61</sub>-butyric acid methyl ester (PCBM). In contrast, the relative E<sub>1/2</sub>(0/-) values of 2 and C<sub>60</sub>, -0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the E<sub>1/2</sub>(0/-) of PCBM is -0.09 V). Time-resolved microwave conductivity charge-carrier yield x mobility values for organic photovoltaic active-layer-type blends of 2 and poly-3-hexylthiophene (P3HT) were comparable to those for equimolar blends of PCBM and P3HT. The structure of solvent-free crystals of 2 was determined by single-crystal X-ray diffraction. The number of nearest-neighbor fullerene–fullerene interactions with centroid∙∙∙centroid (⊙∙∙∙⊙) distances of ≤ 10.34 Å is significantly greater, and the average ⊙∙∙∙⊙ distance is shorter, for 2 (10 nearest neighbors; ave. ⊙∙∙∙⊙ distance = 10.09 Å) than for solvent-free crystals of PCBM (7 nearest neighbors; ave. ⊙∙∙∙⊙ distance = 10.17 Å). Finally, the thermal stability of 2 was found to be far greater than that of PCBM.
- Published through SciTech Connect., 12/16/2014., "pnnl-sa-105706", "48349", "KC0301020", Chemical Science (Online) 6 3 ISSN 2041-6539 AM, and San, Long K.; Bukovsky, Eric V.; Larson, Bryon W.; Whitaker, James B.; Deng, Shihu; Kopidakis, Nikos; Rumbles, Garry; Popov, Alexey A.; Chen, Yu-Sheng; Wang, Xue B.; Boltalina, Olga V.; Strauss, Steven H.
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