A faux hawk fullerene with PCBM-like properties

• Published in: Chemical science (Cambridge) 2015-03, Vol.6 (3), p.1801-1815
• Main Authors: San, Long K, Bukovsky, Eric V, Larson, Bryon W, Whitaker, James B, Deng, S H M, Kopidakis, Nikos, Rumbles, Garry, Popov, Alexey A, Chen, Yu-Sheng, Wang, Xue-Bin, Boltalina, Olga V, Strauss, Steven H
• Format: Article
• Language: English
• Subjects: Blends; Buckminsterfullerene; Derivatives; Electron affinity; Fullerenes; Organic chemistry; Polymer blends; Thermal stability
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c4sc02970d

Reaction of C , C F CF I, and SnH( -Bu) produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C (CF C F )H ( ) and 1,9-C ( -CF (2-C F )) ( ). The highest isolated yield of was 35% based on C . Depending on the reaction conditions, the relative amounts of and generated were as high as 85% and 71%, respectively, based on HPLC peak integration and summing over all fullerene species present other than unreacted C . Compound is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 °C but was rapidly converted to upon addition of Sn ( -Bu) at this temperature. In contrast, complete conversion of to occurred within minutes, or hours, at 25 °C in 90/10 (v/v) PhCN/C D by addition of stoichiometric, or sub-stoichiometric, amounts of proton sponge (PS) or cobaltocene (CoCp ). DFT calculations indicate that when is deprotonated, the anion C (CF C F ) can undergo facile intramolecular S Ar annulation to form with concomitant loss of F . To our knowledge this is the first observation of a fullerene-cage carbanion acting as an S Ar nucleophile towards an aromatic C-F bond. The gas-phase electron affinity (EA) of was determined to be 2.805(10) eV by low-temperature PES, higher by 0.12(1) eV than the EA of C and higher by 0.18(1) eV than the EA of phenyl-C -butyric acid methyl ester (PCBM). In contrast, the relative (0/-) values of and C , -0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the (0/-) of PCBM is -0.09 V). Time-resolved microwave conductivity charge-carrier yield × mobility values for organic photovoltaic active-layer-type blends of and poly-3-hexylthiophene (P3HT) were comparable to those for equimolar blends of PCBM and P3HT. The structure of solvent-free crystals of 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 (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 was found to be far greater than that of PCBM.