Alexey A. Goryunkov

Fusing Pentagons in a Fullerene Cage by Chlorination: IPR D2‐C76 Rearranges into non‐IPR C76Cl24

As is well known, fullerenes obtained by conventional arcdischarge synthesis obey the isolated pentagon rule (IPR). Unless fullerene molecules are directly subjected to “fullerene surgery”, exohedral functionalization does not affect the connectivity of their carbon networks. Non-IPR fullerene isomers have been available through appropriate modifications of the arc-discharge methodology to synthesize an already chemically derivatized molecule in which the derivatization stabilizes the pentagon–pentagon junctions. In particular, non-IPR cages are quite common in endohedral metallofullerenes, as encapsulated metal atoms are likely to stabilize the fused pentagon fragments by charge-transfer binding to them. More recently, a number of unconventional exohedral fullerene derivatives, including C50Cl10, [5, 6] C56Cl10, [7] C66H4, [8] C68Cl4, [6] and non-IPR C60Cl8 and C60Cl12, [9] have been obtained by means of an arc-discharge process in presence of additives such as CCl4, Cl2, and CH4. Rare examples of more classical chemical approaches to nonIPR fullerenes are indirectly confirmed transformation of dodecahedrane into C20 [10] and synthesis of a C62 derivative with four-membered cycle in its carbon cage from C60. [11]

Trifluoromethylated [60]Fullerenes: Synthesis and Characterization

Abstract The high temperature reaction of C60 with silver(I) trifluoroacetate followed by 500°C sublimation and HPLC purification has led to the characterization of the trifluoromethyl‐[60]fullerenes 1,4‐C60(CF3)2, C s‐C60(CF3)4, C 1‐C60(CF3)4, and C 1‐C60(CF3)6 by EI‐MS and 19F NMR. The compounds C 1‐C60(CF3)4 and C 1‐C60(CF3)6 were obtained with 90+% compositional purity. A sample of C60(CF3)2 also contained ca. 15–20% of a C s‐symmetry isomer of C60(CF3)4. The structural assignments are based on calculations at the AM1 and DFT levels of theory.

Synthesis, Structure, and Theoretical Study of Trifluoromethyl Derivatives of C84(22) Fullerene

Trifluoromethylation of higher fullerene mixtures with CF(3)I was performed in ampoules at 400 to 420 and 550 to 560 °C. HPLC separation followed by crystal growth and X-ray diffraction studies allowed the structure elucidation of nine CF(3) derivatives of D(2)-C(84) (isomer 22). Molecular structures of two isomers of C(84)(22)(CF(3))(12), two isomers of C(84)(22)(CF(3))(14), four isomers of C(84)(22)(CF(3))(16), and one isomer of C(84)(22)(CF(3))(20) were discussed in terms of their addition patterns and relative formation energies. DFT calculations were also used to predict the most stable molecular structures of lower CF(3) derivatives, C(84)(22)(CF(3))(2-10). It was found that the addition of CF(3) groups to C(84)(22) is governed by two rules: additions can only occur at para positions of C(6)(CF(3))(2) hexagons and no additions can occur at triple-hexagon-junction positions on the fullerene cage.

Reaction of silver(I) and (II) fluorides with C60: thermodynamic control over fluorination level

Silver(I) fluoride is shown to be a weak fluorinating agent (FA) for C-60 and gives mainly C60F18. Fluorination with silver(II) fluoride yields C60F44, a new compound, as the predominant product (> 80% in the crude). Fluorination degree of fullerenes in reaction with binary metal fluorides is found to be mainly thermodynamically controlled. The correlation between the level of C-60 fluorination and oxidising fluorinating strength of the metal fluorides used for fluorofullerene preparations is discussed, permitting development of a self-consistent quantitative scale for inorganic FAs.

Regioselective synthesis and crystal structure of C70(CF3)10[C(CO2Et)2]

The Bingel reaction of poly(trifluoromethyl)fullerene p7mp-C70(CF3)10 with diethyl malonate and CBr4 in the presence of bases yields the C70(CF3)10[C(CO2Et)2] cycloadduct as a major product, along with two C70(CF3)10[CH(CO2Et)] isomers. An XRD study of the main compound demonstrates that a [2 + 1] cycloaddition occurs at the unoccupied pole of the p7mp-C70(CF3)10 molecule. The observed regiochemical selectivity of the [2 + 1] cycloaddition is shown to be favored from both energetic and orbital reactivity viewpoints.

p-type doping in organic light emitting diodes based on fluorinated C60

We report on hybrid organic light emitting diodes based on spin coated PVK (poly(vinylcarbazole))/poly-TPD (poly(triphenyldiamine)) formulation electron blocking and conjugated peptide emitter layers while the hole blocking, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), layer is vacuum sublimed. The device structure is realized through the use of fluorinated C60 as a p-dopant in a cross-linked hole transporting formulation. The lowering of the turn-on voltage is demonstrated using a conjugated peptide as the emitter layer. We suggest that fluorinated C60s could play a major role as tunable dopants in organic electronics.

Synthesis and characterization of difluoromethylene-homo[60]fullerene, C60(CF2)

Refluxing of the o-DCB solution of C60 with CF2ClCOONa and 18-crown-6 leads to formation of C60(CF2)n (n = 1-3); the monoadduct C60(CF2) has been found to consist of the main [6,6]- and minor [5,6]-isomers, both having an open structure.

In situ synthesis and characterization of fullerene derivatives by Knudsen-cell mass spectrometry

Abstract The use of a mass spectrometer equipped with a Knudsen cell as a chemical reactor for studies of solid-state reactions of fullerenes is described. The simultaneous generation and mass-spectrometric detection of the volatile products provided a wealth of information on the dynamics of formation and the distribution of products as reaction conditions were varied in each synthesis/characterization experiment. A combination of new results and previously published data are used to demonstrate how in situ Knudsen-cell mass spectrometry led to the rapid development of an important branch of synthetic fullerene chemistry that has yielded many new fluorofullerenes and related derivatives with novel structures and properties.

Preparation, crystallographic characterization and theoretical study of two isomers of C70(CF3)12

Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers.

Transalkylation of Higher Trifluoromethylated Fullerenes with C70: A Pathway to New Addition Patterns of C70(CF3)8

We report three new isomers of C70(CF3)8, structurally related to p(7)mp-C70(CF3)10, that are inaccessible by direct trifluoromethylation, but can be easily identified among the products of the transalkylation of higher trifluoromethylfullerenes with C70. The reported compounds are characterized by UV/Vis, 1 D and 2 D COSY (19)F NMR spectroscopy, and DFT calculations. A rather unusual addition pattern is observed in p(6),i-C70(CF3)8 in which one addend is attached remotely from the others; polarization of the adjacent unsaturated bonds by the addend makes the molecule readily oxidizable.