科研之友
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摘要
Reaction of C-60, C6F5CF2I, and SnH(n-Bu)(3) produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C-60(CF2C6F5)H (1) and 1,9-C-60(cyclo-CF2(2-C6F4)) (2). The highest isolated yield of 1 was 35% based on C-60. 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-60. Compound 1 is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 degrees C but was rapidly converted to 2 upon addition of Sn-2(n-Bu)(6) at this temperature. In contrast, complete conversion of 1 to 2 occurred within minutes, or hours, at 25 degrees C in 90/10 (v/v) PhCN/C6D6 by addition of stoichiometric, or sub-stoichiometric, amounts of proton sponge (PS) or cobaltocene (CoCp2). DFT calculations indicate that when 1 is deprotonated, the anion C-60(CF2C6F5) can undergo facile intramolecular SNAr annulation to form 2 with concomitant loss of F . 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-60 and higher by 0.18(1) eV than the EA of phenyl-C-61-butyric acid methyl ester (PCBM). In contrast, the relative E-1/2(0/-) values of 2 and C-60, -0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the E-1/2(0/-) of PCBM is -0.09 V). Time-resolved microwave conductivity chargecarrier 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 (circle dot...circle dot) distances of <= 10.34 angstrom is significantly greater, and the average circle dot...circle dot distance is shorter, for 2 (10 nearest neighbors; ave. circle dot...circle dot distance = 10.09 angstrom) than for solvent-free crystals of PCBM (7 nearest neighbors; ave. circle dot...circle dot distance = 10.17 angstrom). Finally, the thermal stability of 2 was found to be far greater than that of PCBM.
- 出版日期2015
