Sergey I. Troyanov

Non-aqueous synthesis of high surface area aluminium fluoride-a mechanistic investigation

Fluoride can do it too! Sol–gels of metal fluorides play an important role in the formation of high surface area metal fluorides. The synthesis of amorphous high surface area metal fluorides via a recently discovered two-step synthetic route was investigated in detail, exemplified for aluminium fluoride. The first step is fluorination of aluminium alkoxide with anhydrous HF in organic solvents, which proceeds as a sol–gel process known until now only for metal oxide formation. The reaction pathway is illustrated including crystal structure determination of the intermediate aluminium alkoxide fluoride. The resulting amorphous aluminium alkoxide fluoride has to be freed in a second step of solvating alcohol and of residual alkoxidic groups. This is done by heating in a stream of a mild fluorinating agent like a HCFC or CFC or in HF to obtain high surface area and very high Lewis acidity; an inert gas such as N2 is not sufficient. Using a variety of analytical techniques, including liquid and solid state NMR, X-ray structure analysis and XPS, the reaction pathways have been elucidated.

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]

Facile preparation of amine and amino acid adducts of [60]fullerene using chlorofullerene C60Cl6 as a precursor.

We report a general synthetic approach to the preparation of highly functionalized amine and amino acid derivatives of [60]fullerene starting from readily available chlorofullerene C(60)Cl(6). The synthesized water-soluble amino acid derivative of C(60) demonstrated pronounced antiviral activity, while the cationic amine-based compound showed strong antibacterial action in vitro.

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.

Connectivity patterns of two C90 isomers provided by the structure elucidation of C90Cl32.

Two for the price of one: The first halogenated derivative of C(90), C(90)Cl(32) (see structure; gray C, green Cl), is obtained by chlorination of a higher fullerene mixture with SbCl(5). Its molecular structure, elucidated by single-crystal X-ray diffraction, reveals the presence of two isomeric C(90) cages that correspond to C(2v) isomer 46 and C(s) isomer 34. The addition of 32 chlorine atoms is the maximum degree of chlorination achieved for fullerenes.

Bromination of [60]Fullerene. I. High‐Yield Synthesis of C60Br x (x=6, 8, 24)

Abstract The systematic study of the bromination of C60 was performed under various experimental conditions. Application of some chloroarenes as reaction media resulted in the high‐yield (70–96%) selective synthesis of C60Br6 and C60Br8. Direct bromination of fullerene yielded either C60Br8, C60Br14, or C60Br24 depending on the reaction time. Possible pathways of bromination of C60Br8 were analyzed using semiempirical (AM1) calculations, two most probable molecular structures are conjectured for the first isolated C60Br14.

Design of indigo derivatives as environment-friendly organic semiconductors for sustainable organic electronics

We report the synthesis and systematic investigation of nine different indigo derivatives as promising materials for sustainable organic electronics. It has been shown that chemical design allows one to tune optoelectronic properties of indigoids as well as their semiconductor performance in OFETs. Fundamental correlations between the molecular structures of indigo derivatives, structural characteristics of their films, charge carrier transport properties and transistor characteristics have been revealed. Particularly important was lowering the LUMO energy levels of indigoids bearing strong electron withdrawing groups which improved dramatically ambient stability of n-type OFETs. Chemical structures of novel indigoids enabling truly air-stable n-channel OFET operation were proposed.

Four Isomers of C96 Fullerene Structurally Proven as C96Cl22 and C96Cl24

Investigations of higher fullerenes (larger than C70) have been hampered by their low abundance in fullerene soot and by the fact that the number of stable fullerene isomers obeying the isolated pentagon rule (IPR) increases rapidly with the cage size. Structural characterization of higher fullerenes is typically accomplished by means of C NMR spectroscopy which provides information on molecular symmetry. However, the identification of higher fullerenes by this conventional method is not unambiguous in many cases since several isomers may exhibit the same molecular symmetry. Theoretical calculations provide information concerning the relative stability and the expected line distribution in the NMR spectra, thus assisting in the cage assignment. The derivatization of higher fullerenes followed by the separation of derivatives and characterization by direct methods appeared to be a rather effective approach, as illustrated by some examples for C78–C90 based on their perfluoroalkylated and halogenated derivatives. Experimental observations on higher fullerenes beyond C90 are additionally hindered by the very small amounts of available materials and the large number of possible isomers to be separated. As one of the largest higher fullerenes isolable from fullerene soot, C96 is predicted to have 187 possible IPR cage isomers according to the topological analysis. The first chromatographic isolation and C NMR characterization of C96 fullerenes indicated the presence of as many as ten different isomers in fullerene soot. Theoretical calculations were performed for C96 isomers to predict their relative stabilities. According to the calculations by the tight binding energy method, the four most stable C96 isomers possess C1, C1, Cs, and D6d symmetry. [6a] Another series of stable isomers was suggested by using MM3 and MNDO calculations with the D2 isomer as the most stable followed by another D2 isomer then C2 and D6d isomers. [6b] More exhaustive computations at the B3LYP/6-31G level predicted isomer 183 (D2) to be the most stable at low temperatures followed by isomers 181 (C2), 144 (C1), and 145 (C1). [7a] This order of stability was confirmed by PBE1PBE/6311G* single point energy calculations. The first direct experimental proof of the cage connectivity of C96 (isomer 145) was achieved by pentafluoroethylation of a C76–C96 mixture with C2F5I, followed by HPLC separation and a single-crystal X-ray analysis of C96(C2F5)12. [8] Very recently, the isolation of four pristine C96 isomers and X-ray structural characterization of two of them (nos. 3 and 181) have been reported. In the present work we used chlorination as the derivatization method; we isolated and crystallographically characterized C96 chlorides containing four different C96 cages, three of which were detected for the first time. The results are compared with theoretical predictions for C96 IPR isomers and discussed further in terms of cage connectivities, addition patterns, and formation energies. We isolated three C96 fractions from the fullerene soot synthesized from an undoped graphite rod by three-stage HPLC (see the Supporting Information for experimental details). Briefly, in the first stage, the C96 fraction with retention times ranging from 35.3 to 39.0 min was collected using a Cosmosil 5PYE column. This fraction was further separated in the second stage by recycling HPLC using a Buckyprep column to afford two major fractions. In the third stage, each of these fractions was further separated by recycling HPLC under similar conditions, resulting in the isolation of three C96 subfractions which were labeled C96 (I), C96 (II), and C96 (III). MALDI-TOF MS analysis showed that these fractions are compositionally pure and and differences in their elecronic structures are clearly seen in UV/Vis/NIR spectra (see the Supporting information). C96 fractions (I–III) were used in chlorination experiments with VCl4 as the chlorinating agent. A small amount of C96 (I, II, or III) (0.05–0.1 mg) and an excess of VCl4 (ca. 0.4 mL) were heated in a glass ampoule at 340–3608C for 7– 30 days. The formation of microcrystals was observed after several days; upon further heating crystals slowly grew with dimensions of up to 0.01–0.03 mm. After the ampoule was opened, the excess VCl4 was removed by washing the residue with water. The remaining tiny crystals were investigated by X-ray diffraction with the use of synchrotron radiation. The crystallographic results revealed that the chlorides obtained from fractions C96 (I) and C96 (III) have the compo[*] Prof. Dr. S. F. Yang, T. Wei Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Materials for Energy Conversion Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 (China) E-mail: sfyang@ustc.edu.cn

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.