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- Item19F NMR-, ESR-, and vis-NIR-spectroelectrochemical study of the unconventional reduction behaviour of a perfluoroalkylated fullerene: dimerization of the C70(CF3)10− radical anion(Cambridge : Soc., 2015) Zalibera, Michal; Machata, Peter; Clikeman, Tyler T.; Rosenkranz, Marco; Strauss, Steven H.; Boltalina, Olga V.; Popov, Alexey A.The most abundant isomer of C70(CF3)10 (70-10-1) is a rare example of a perfluoroalkylated fullerene exhibiting electrochemically irreversible reduction. We show that electrochemical reversibility at the first reduction step is achieved at scan rates higher than 500 V s−1. Applying ESR-, vis-NIR-, and 19F NMR-spectroelectrochemistry, as well as mass spectrometry and DFT calculations, we show that the (70-10-1)− radical monoanion is in equilibrium with a singly-bonded diamagnetic dimeric dianion. This study is the first example of 19F NMR spectroelectrochemistry, which promises to be an important method for the elucidation of redox mechanisms of fluoroorganic compounds. Additionally, we demonstrate the importance of combining different spectroelectrochemical methods and quantitative analysis of the transferred charge and spin numbers in the determination of the redox mechanism.
- ItemPerfluoroalkylfullerenes(Washington, DC : ACS Publ., 2015) Boltalina, Olga V.; Popov, Alexey A.; Kuvychko, Igor V.; Shustova, Natalia B.; Strauss, Steven H.New chemical derivatives that possess the greatest variety of addition patterns than any other class of fullerene derivatives represent an important addition to the existing classes of perfluorocarbons, that is, compounds that are composed only of the two types of atoms, carbon and fluorine. These include aromatic and aliphatic perfluorocarbons such as perfluorodecalin, perfluorononane, hexafluorobenzene, etc., which are important as fluorous solvents used in medicine. The propensity of perfluoroalkylfullerenes (PFAFs) to readily crystallize from organic solutions upon slow evaporation in open air provided a straightforward access to their molecular structures via X-ray crystallography. Another crucial aspect that ensures future success in the characterization of numerous PFAFs of higher fullerenes and endohedral metallofullerenes is the possibility to apply HPLC methodologies to the separation of product mixtures. PFAFs, especially those of C60 and C70, are unique fullerene derivatives in terms of the number of structurally characterized derivatives with different number of RF groups and different addition patterns.
- ItemA faux hawk fullerene with PCBM-like properties(Cambridge : Royal Society of Chemistry, 2014) 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.Reaction of C60, C6F5CF2I, and SnH(n-Bu)3 produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C60(CF2C6F5)H (1) and 1,9-C60(cyclo-CF2(2-C6F4)) (2). The highest isolated yield of 1 was 35% based on C60. 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 C60. Compound 1 is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 °C but was rapidly converted to 2 upon addition of Sn2(n-Bu)6 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/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 C60(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 C60 and higher by 0.18(1) eV than the EA of phenyl-C61-butyric acid methyl ester (PCBM). In contrast, the relative E1/2(0/−) values of 2 and C60, −0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the E1/2(0/−) of PCBM is −0.09 V). Time-resolved microwave conductivity charge-carrier yield × 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.
- ItemPAH/PAH(CF3)n Donor/Acceptor Charge-Transfer Complexes in Solution and in Solid-State Co-Crystals(Weinheim : Wiley-VCH, 2019) Castro, Karlee P.; Bukovsky, Eric V.; Kuvychko, Igor V.; DeWeerd, Nicholas J.; Chen, Yu-Sheng; Deng, Shihu H.M.; Wang, Xue-Bin; Popov, Alexey A.; Strauss, Steven H.; Boltalina, Olga V.A solution, solid-state, and computational study is reported of polycyclic aromatic hydrocarbon PAH/PAH(CF3)n donor/acceptor (D/A) charge-transfer complexes that involve six PAH(CF3)n acceptors with known gas-phase electron affinities that range from 2.11(2) to 2.805(15) eV and four PAH donors, including seven CT co-crystal X-ray structures that exhibit hexagonal arrays of mixed π-stacks with 1/1, 1/2, or 2/1 D/A stoichiometries (PAH=anthracene, azulene, coronene, perylene, pyrene, triphenylene; n=5, 6). These are the first D/A CT complexes with PAH(CF3)n acceptors to be studied in detail. The nine D/A combinations were chosen to allow several structural and electronic comparisons to be made, providing new insights about controlling D/A interactions and the structures of CT co-crystals. The comparisons include, among others, CT complexes of the same PAH(CF3)n acceptor with four PAH donors and CT complexes of the same donor with four PAH(CF3)n acceptors. All nine CT complexes exhibit charge-transfer bands in solution with λmax between 467 and 600 nm. A plot of E(λmax) versus [IE(donor)−EA(acceptor)] for the nine CT complexes studied is linear with a slope of 0.72±0.03 eV eV−1. This plot is the first of its kind for CT complexes with structurally related donors and acceptors for which precise experimental gas-phase IEs and EAs are known. It demonstrates that conclusions based on the common assumption that the slope of a CT E(λmax) versus [IE−EA] plot is unity may be incorrect in at least some cases and should be reconsidered. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim