Crystallographic characterization and identification of a minor isomer of C(84) fullerene

We report the synthesis and single crystal X-ray analysis of C(84) ().AgTPP (Ag tetraphenylporphyrin) cocrystal-the first ordered crystal structure containing a pristine higher fullerene.     

Isolation and crystal structure of the trifluoromethyl derivative C84(24)(CF3)18 of a minor C84 fullerene isomer

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Deformation and thermodynamic instability of a C84 fullerene cage

Quantum chemical calculations of electronic and geometric structures were performed for molecules of 24 isomers of C₈₄ fullerenes obeying the isolated pentagons rule. The reasons for the instability of isomers not obtained experimentally were established, and the possibility of obtaining some of them was proven. It was shown that the deformation of hexagons and pentagons is the most important geometric parameter directly connected with the thermodynamic instability of fullerenes having closed shells, reflecting the local strain of the molecules.     

In situ ESR–UV/VIS/NIR spectroelectrochemistry of an empty fullerene anion and cation: The C82:3 isomer

The application of in situ ESR–UV/VIS/NIR spectroelectrochemistry to the highly purified C₈₂:3 fullerene isomer with C₂ symmetry made the detailed characterization of the radical structures formed by electrochemical generation possible. This first comprehensive spectroelectrochemical study of the stable radical anion and cation of an empty cage higher fullerene in acid-free organic electrolyte is a contribution to the general understanding of charged states at endohedral fullerenes.     

Radical character of non-IPR isomer 28324 of C80 fullerene

Russian Chemical Bulletin - The molecular structure of the 28324 isomer (C1) of C80 fullerene was analyzed based on the concept of substructures in fullerene molecules and with allowance for...     

A combination of in situ ESR and in situ NMR spectroelectrochemistry for mechanistic studies of electrode reactions: the case of p-benzoquinone

A combined in situ NMR and in situ ESR spectroelectrochemical study of a reaction mechanism is presented detecting and describing the whole number of paramagnetic and diamagnetic intermediates and final products in an electrode reaction. While in situ NMR spectroelectrochemistry provides a powerful method for the study of structural or electronic changes of diamagnetic molecules in any electrochemical reaction mechanism, in situ ESR spectroelectrochemistry is the method of choice to detect paramagnetic structures and to characterise their electronic state via the g-value and hyperfine splitting in redox reactions. To demonstrate the power of this combination of magnetic spectroscopies in electrochemistry, the reduction of p-benzoquinone to hydroquinone is followed by both these spectroelectrochemical methods at selected pH values, thus considering the influence of the proton on the reaction mechanism. The results of both in situ spectroelectrochemical methods at the same redox system are used to get the complete reaction mechanism of p-benzoquinone at electrodes in aqueous solutions.     

Preparation and crystal structure of C84(11)Cl20,22, chloro derivatives of a C84 minor isomer

Chlorofullerenes C₈₄(11)Cl₂₀ and C₈₄(11)Cl₂₂ were prepared by chlorination of C₂–C₈₄(11) with VCl₄ at 340–360 °C. An X-ray crystallographic study with the use of synchrotron radiation revealed the chlorination patterns featuring only para additions in C₆Cl₂ hexagons.     

The carbon skeleton of the belt region of fullerene C84 (D2)

The synthesis and structural characterization of the double-stranded carbon skeleton in the belt region of a C84 fullerene has been achieved. The synthetic methodology used is based on cyclic dimerization of diastereomeric AB-type monomers 18 by a non-diastereospecific Diels-Alder reaction with isobenzofuran and acenaphthylene groups as reactive termini. Four diasteromeric monomer precursors 17 were prepared for the first time by the use of dihydropyracylene (12) in a multistep synthesis. The synthesis of dihydropyracylene itself has been optimized to the degree that it is now available on the 10 g scale. The belt-shaped macrocycle 19, obtained from dimerization of the monomers 17, could be partly aromatized by an acid-catalyzed dehydration reaction to give 23, which differs from the fully unsaturated belt by two water molecules. Semiempirical AM1 calculations of the electronic and thermodynamic properties of cyclic fluoranthenes revealed strain energy as the essential reason for the incomplete aromatization of 19. The structures of the macrocycles 19 and 23, one of the monomer precursors, and two diastereomeric epoxybenzo[k]fluoranthenes were elucidated by single-crystal X-ray crystallography.     

ESR study of spin-adducts of trimethylaminoboryl radicals with fullerene C60

It was established by ESR that trimethylaminoboryl radicals formed by UV irradiation of BH₃NMe_6w in the presence of di-tert-butyl peroxide in saturated benzene solutions of fullerene C₆₀, add to fullerenes to give C₆₀-BH₂NMe₃ spin-adducts. The latter undergo dimerization with a rate constant ofca. 2.5 · 10⁶ L mol^–1 s^–1. A more prolonged photolysis of excess BH₃NMe₃ in a benzene solution of C₆₀ results in multiple addition of the trimethylaminoboryl radicals to the fullerene to give stable radicals C₆₀[BH₂NMe₃]_n.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 673–675, April, 1994.     

Catalytic cycloaddition of diazoalkanes generated in situ to fullerene C60

Russian Journal of Organic Chemistry -     

Absolute configuration of D(2)-symmetric fullerene C(84)

The D(2)-symmetric isomer of fullerene C(84) predominantly found in soots is inherently chiral. We determine its absolute configuration by comparison of the experimental electronic circular dichroism (CD) spectrum with time-dependent density functional calculations.     

X-ray crystallographic proof of the isomer D2-C84(5) as trifluoromethylated and chlorinated derivatives, C84(CF3)16, C84Cl20, and C84Cl32

Minor isomer comes forward: Minor isomer C(84)(5) has been captured by high temperature trifluoromethylation with CF(3)I and chlorination with VCl(4). The compounds C(84)(CF(3))(16), C(84)Cl(20), and C(84)(5)Cl(32) were investigated by X-ray crystallography providing the first direct proof of the cage connectivity of D(2)-C(84)(5). The D(2)-C(84)(5)Cl(32) molecule (see figure; C grey, Cl green) contains two flattened, pyrene-like substructures on opposite poles of the cage resulting in its drum-like shape.     

Study of ESR spectra of fullerene C60 doped with magnesium and mercury

An increase in the intensity of the ESR signal and of its g value was observed in the course of annealing of the diamagnetic product of the reaction between magnesium amalgam and a toluene solution of C₆₀. The formation of a crystalline substance Mg_rC₆₀ with semiconductor properties was assumed. The ESR spectra of the products of vapor-phase synthesis of MgC₆₀ and Hg_rC₆₀ were recorded.Translated fromlzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2256–2258, September, 1996.     

Electronic structures of some of C84 fullerene isomers and the structures of their perfluoroalkyl derivatives

The electronic structures of the pristine fullerene molecules have been shown for the first time to be is the most important factor affecting the distribution of addends in the addition reactions of perfluoroalkyl radicals R^F to C₈₄ fullerene, and most likely positions of addends on the fullerene core are hexagons with delocalized π-bonds.     

Determination of coenzyme Q10 by in situ EPR spectroelectrochemistry

A rapid and sensitive method is developed for the determination of coenzyme Q₁₀ (CoQ₁₀) on the basis of the measurement of the radical intermediate (ubisemiquinone) formed during the reduction reaction of CoQ₁₀ at a silver electrode by in situ EPR spectroelectrochemical techniques. At the potential of −0.55 V (versus SCE), the ubisemiquinone is formed and is stable in ethanol+water. Under optimal conditions, it was found that the proposed method provided a linear response over the CoQ₁₀ concentration range 5–100 μmol l⁻¹ with a detection limit of 3 μmol l⁻¹. The relative standard deviation of the results was 7.5% for six successive determinations at 10 μmol l⁻¹ CoQ₁₀. This method is a useful tool for improving the selectivity when other chemicals present in the sample do not interfere in the assay.     

Synthesis,electrochemistry and in situ spectroelectrochemistry of water-soluble phthalocyanines

The synthesis, characterization and voltammetric and spectroelectrochemical properties of newly synthesized metal-free and metallo phthalocyanines (M = Co, Cu, Zn) containing four dialkylaminophenoxy or trialkylammoniumphenoxy substituents on peripheral positions have been presented in this work. The new compounds have been characterized by using elemental analysis, UV–Vis, FT-IR, ¹H NMR and MS spectroscopic data. Phthalocyanines with trialkylammoniumphenoxy substituents are soluble in aqueous solution over a wide pH range, and these compounds are present as aggregated species in solution as confirmed by the blue shift of Q-bands in their electronic spectra. The electrochemical behavior of the phthalocyanines was investigated by cyclic voltammetry and differential pulse voltammetry on a platinum-working electrode in DCM and DMSO. The voltammetric and spectroelectrochemical measurements of the complexes show that while cobalt phthalocyanine gives both ligand- and metal-based redox processes, metal-free, zinc and copper phthalocyanine complexes give only ligand-based processes in harmony with common phthalocyanine complexes.