Lev N. Sidorov

GIBBS ENERGIES OF GAS-PHASE ELECTRON TRANSFER REACTIONS INVOLVING THE LARGER FULLERENE ANIONS

Abstract Accurate data on the Gibbs energies of gas-phase fullerene anion/fullerene molecule exchange reactions have been obtained from equilibrium constant measurements using the Knudsen cell mass spectrometry method. The electron affinities (EA) for the series of [70 + 2n]fullerenes (n = 0, 1,…, 18) were determined. The EA values show an increase with the size of the molecule over the whole range, although disruption from the monotonic change was observed in the series of [70]-, [72]-,[74]- and [76]fullerenes. The correlation of the EA change in the larger fullerene series with their electronic structures is discussed.

Two Isomers of C60F48: An Indented Fullerene

Deflated buckyballs: The single-crystal structure of C60 F48 ⋅2 (mesitylene) revealed the presence of both D3 and S6 isomers in the same crystal. C(sp2 )-C(sp2 ) bonds (1.30 Å) are much shorter than C(sp3 )-C(sp3 ) bonds (1.54-1.63 Å). The C60 cage is characterized by concave areas in the regions of six double bonds. Each double bond is effectively shielded by four F atoms, which accounts for the low reactivity of C60 F48 .

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]

Isolation and Structural X‐ray Investigation of Perfluoroalkyl Derivatives of Six Cage Isomers of C84

Perfluoroalkylation of a higher fullerene mixture with CF(3)I or C(2)F(5)I, followed by HPLC separation of CF(3) and C(2)F(5) derivatives, resulted in the isolation of several C(84)(R(F))(n) (n=12, 16) compounds. Single-crystal X-ray crystallography with the use of synchrotron radiation allowed structure elucidation of eight C(84)(R(F))(n) compounds containing six different C(84) cages (the number of the C(84) isomer is given in parentheses): C(84) (23)(C(2)F(5))(12) (I), C(84) (22)(CF(3))(16) (II), C(84) (22)(C(2)F(5))(12) (III), C(84) (11)(C(2)F(5))(12) (IV), C(84) (16)(C(2)F(5))(12) (V), C(84) (4)(CF(3))(12) (VI with toluene and VII with hexane as solvate molecules), and C(84) (18)(C(2)F(5))(12) (VIII). Whereas some connectivity patterns of C(84) isomers (22, 23, 11) had previously been unambiguously confirmed by different methods, derivatives of C(84) isomers numbers 4, 16, and 18 have been investigated crystallographically for the first time, thus providing direct proof of the connectivity patterns of rare C(84) isomers. General aspects of the addition of R(F) groups to C(84) cages are discussed in terms of the preferred positions in the pentagons under the formation of chains, pairs, and isolated R(F) groups.

Preparation and crystal structure of solvent free C60F18

Abstract C60F18 single crystals were grown by vacuum sublimation from the product of reaction of C60 with K2PtF6 at 460 K in vacuo. Solvent free C60F18 containing only a few percent of C60F18O crystallizes in monoclinic lattice. The molecular structure of C60F18 is very close to that found in the C60F18 solvates with aromatic hydrocarbons. Two C…C distances are slightly elongated in the statistically averaged structure due to the presence of C60F18O.

The standard enthalpy of formation of fullerene chloride C60Cl30

A rotating-bomb calorimeter was used to measure the energy of combustion of crystalline fullerene chloride C60Cl30 · 0.09Cl2, ΔcU° = (−24474 ± 135 kJ/mol). The result was used to calculate the standard enthalpy of formation, ΔfH° (C60Cl30, cr) = 135 ± 135 kJ/mol, and the C-Cl bond energy, 195 ± 5 kJ/mol. The C-X (X = F, F, Cl, and Br) bond energies in fullerene C60 derivatives and other organic compounds are compared.

Mass spectrometric investigation of two-component systems of complex vapour composition by the isothermal evaporation method

The Isothermal Evaporation Method (IEM) and its application to the investigation of two-component systems is considered. The isothermal evaporation process should be carried out rather slowly (1–3% mole per hour). Under this condition the process can be considered as a sequence of equilibrium states. Ion current intensities are measured as a function of time. Taken in such a way the ion current time dependences are transposed into dependences of the partial pressures on the melt composition. The mathematical part of IEM which makes possible this transformation is based on two well-know equations, viz. Knudsens equation and the Gibbs—Duhem equation. Using EIM the following two-component systems were studied: NaFMFn (where M = Be, Mg, Ba, Al, Sc, Y, La, Zr), KFAlF3, LiFAlF3 and LiFScF3. In the equilibrium vapour of these systems four types of molecules were found: AB  NaBeF3, NaAlF4, NaScF4, NaYF4, NaZrF4, LiAlF4, LiScF4 KAlF4; A2B2(NaBeF3)2, (NaAlF4)2, (LiAlF4)2, (KAlF4)2; A2B  Na2BeF4, Li2AlF4, possibly Na2AlF5; AB2  NaV2F7. The mass spectra of the main positive ions, the relative ionization cross-sections, heats and entropies of dissociation of these molecules are given. Investigation of two-composition systems of complex vapour composition leads to the conclusion that some of the thermodynamic relations can usefully be written in a form which takes into account the complex vapour composition. Forms of Gibbs—Duhems and Schreders equations are considered. The relations which are true at the extreme points of the isothermal function are given. Examples illustrating the mass-spectrometric application of the given thermodynamic relations are given.

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.

Electron affinity of some trimetallic nitride and conventional metallofullerenes

Abstract The electron affinity of a series of discandium endohedral fullerenes and new trimetallic nitride endohedral molecules Sc x Er 3-x N@C 80 was determined by means of the Knudsen cell mass spectrometry—ion-molecular equilibria method. Some considerations were made concerning the influence of the charge transfer from the endohedral atoms to the carbon cage on the electron affinity of the endohedral molecule.

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.