Vitaliy Yu. Markov

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.

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.

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis, Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C70(CF2 )n (n=1-3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2 ) mono-adducts with [6,6]-open and [6,6]-closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X-ray analysis and high-level spectroscopic techniques. The [6,6]-open isomer of C70(CF2 ) constitutes the first homofullerene example of a non-hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2 ) isomers showed that it is substantially higher for the [6,6]-open isomer (the 70-electron π-conjugated system is retained) than the [6,6]-closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2 ) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter-conversion between the [6,6]-closed and [6,6]-open forms of a cage-modified fullerene driven by an electrochemical one-electron transfer. Thus, [6,6]-closed C70(CF2 ) constitutes an interesting example of a redox-switchable fullerene derivative.

Mass spectrometric studies of 1-ethyl-3-methylimidazolium and 1-propyl-2,3-dimethylimidazolium bis(trifluoromethyl)-sulfonylimides

RATIONALE Ionic liquids ([Cat(+)][An(-)]) were believed to decompose before reaching vaporization temperatures, but recently some of them have been shown to vaporize congruently. Low-temperature vaporization of ionic substances is an intriguing phenomenon, so the vapor-phase composition and reactions of ionic liquids deserve more extensive study. METHODS Evaporation of two ionic liquids, [C2MIM(+)][Tf2 N(-)] and [C3MMIM(+)][Tf2N(-)], was studied by means of Knudsen effusion mass spectrometry. These liquids were also characterized using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, UV/Vis, IR, NMR spectroscopy, and elemental analysis. RESULTS The vaporization enthalpies of (118 ± 3) and (124 ± 2) kJ·mol(-1) were determined for [C2MIM(+)][Tf2N(-)] and [C3MMIM(+)][Tf2N(-)], respectively. The corresponding equations for their saturated vapor pressures are: ln(p{[C2MIM(+)][Tf2N(-)]}/Pa) = -(14213 ± 325)/(T/K) + (26.57 ± 1.04), ln(p{[C2MMIM(+)][Tf2N(-)]}/Pa) = -(14868 ± 221)/(T/K) + (27.19 ± 0.60). The MALDI studies (positive and negative ion modes) enabled detection of monomeric [Cat(+)] and [An(-)] ions, the cluster ions {[Cat(+)]2 [An(-)]}(+) and {[Cat(+)][An(-)]2}(-), and some complex anions {2[An(-)] + Na(+)}(-), {2[An(-)] + K(+)}(-), {2[An(-)] + Cu(+)}(-) and {3[An(-)] + Ca(2+)}(-). CONCLUSIONS Knudsen effusion mass spectrometry proved to be a valuable method to study the thermodynamics of ionic liquids. The saturated vapor pressure and vaporization enthalpy of [C3MMIM(+)][Tf2N(-)] were accurately determined for the first time. MALDI is also capable of providing indirect information on hydrogen bonding.

Regioselective near-equatorial chlorination of Cs-C70(CF3)8

The chlorination of Cs-C70(CF3)8 by ICl occurs at near-equatorial [5,6] bond in agreement with quantum chemical predictions; structure of the synthesized Cs-C70(CF3)8Cl2 was proven by 19F NMR spectroscopy and single crystal X-ray crystallography.

Orienting effect of the cage addends: the case of nucleophilic cyclopropanation of C2-C70(CF3)8

C2 -C70 (CF3 )8 was found to be a very promising substrate in the Bingel and the Bingel-Hirsch reactions combining perfect regioselectivity with much higher reactivity compared to its analogs. The reactions with diethyl malonate yield a single isomer of the monoadduct C70 (CF3 )8 [C(CO2 Et)2 ] and a single C2 -symmetrical bisadduct C70 (CF3 )8 [C(CO2 Et)2 ]2 . The Bingel-Hirsch variation is particularly interesting in that it additionally affords, in a similar regioselective manner, the unexpected alkylated derivatives C70 (CF3 )8 [CH(CO2 Et)2 ]H and C70 (CF3 )8 [C(CO2 Et)2 ][CH(CO2 Et)2 ]H. The novel compounds have been isolated and structurally characterized by means of (1) H and (19) F NMR spectroscopy as well as single-crystal X-ray diffraction. The mechanistic and regiochemical aspects of the reaction are explained with the aid of DFT calculations.

Synthesis and structure of cycloperfluoroalkylated derivatives of C70, C70(C2F4) and C70(C4F8)n, n = 1–6

The addition reactions of biradicals thermally generated from 1,2-C2F4I2 or 1,4-C4F8I2 were applied to functionalize C70 fullerene. The mixtures of C70(C2F4)m and C70(C4F8)n products were separated by HPLC resulting in several individual compounds. Molecular structures of new cycloperfluoroalkylated C70, C70(C2F4), C70(C4F8) (two isomers), C70(C4F8)2, C70(C4F8)4, C70(C4F8)5 (two isomers), and C70(C4F8)6 (two isomers) were determined by single crystal X-ray diffraction and discussed in terms of their addition patterns and relative energies of their formation.

Reductive hydrogenation of Cs-C70(CF3)8 and C1-C70(CF3)10

CF3 -derivatized fullerenes prove once again to be promising scaffolds for regioselective fullerene functionalization: now with the smallest possible addends-hydrogen atoms. Hydrogenation of Cs -C70 (CF3 )8 and C1 -C70 (CF3 )10 by means of reduction with Zn/Cu couple in the presence of water proceeds regioselectively, yielding only one major isomer of C70 (CF3 )8 H2 and only two for C70 (CF3 )10 H2 , whose addition patterns are combined in the only abundant isomer of C70 (CF3 )10 H4 . The observed selectivity is governed by the electronic structure of trifluoromethylated substrates. Interestingly, we discovered that Clars theory can be utilized to predict the regiochemistry of functionalization, and we look forward to testing it on forthcoming cases of derivatization of pre-functionalized fullerene building blocks.

Chloro Derivatives of Azafullerenes C59NCl5 and Non-Classical C97NCl21

High-temperature chlorination of HPLC fullerene fractions containing mainly C92 /C94 and C102 /C104 resulted in the isolation and X-ray structural characterization of chloro derivatives of azafullerenes, C59 NCl5 and C97 NCl21 . It was assumed that formation of azafullerenes in the arc-discharge synthesis of fullerenes occurred due to air leakage into the reactor. The molecule of C59 NCl5 contains an isolated aromatic pyrrole ring on the fullerene cage and possesses C5v symmetrical shape typical of other known C59 NR5 derivatives. The molecule of non-classical (NC) C97 N(NC)Cl21 contains an NC6 heptagon on the azafullerene cage that assumes its formation by a C2 loss from C99 N in the course of chlorination. The chlorination pattern is characterized by the presence of stabilizing isolated aromatic systems and isolated double C=C bonds on the C97 N(NC) azafullerene cage.

Stepwise Regioselective Hydrogenation of cis‐2‐C60(CF2)2 Homofullerene with [6,6]‐Open/Closed Valence Tautomerism

The homofullerene compound cis-2-C60 (CF2 )2 , which has an unusual kind of open/closed valence tautomerism undergoes consecutive regioselective hydrogenation at bridgehead carbon atoms upon reduction with Zn/Cu couple in H2 O-toluene mixture. The tautomerism barrier in cis-2-C60 (CF2 )2 is negligible in the neutral state, whereas negative charging both impedes tautomeric transformation and promotes regioselective addition of electrophilic species at the bridgehead carbon atoms. In light of this observation, two novel homofullerene derivatives, mixed [6,6]-open/closed C60 (CF2 )2 H2 and [6,6]-open cis-2-C60 (CF2 )2 H4 , were synthesized and their structures were unambiguously determined by means of single crystal X-ray crystallography and NMR spectroscopy.