New pyrrolidine and pyrroline derivatives of fullerenes: from the synthesis to the use in light-converting systems

The results of the authors’ studies on the [2+3] cycloaddition of azomethine and nitrile ylides generated from picolylamine and benzylamine derivatives to fullerenes are systematized and new experimental data are considered. Catalysts and microwave radiation promoting the formation of ylides and their addition to fullerenes were successfully used for the first time. A large series of new pyrrolidine and pyrroline derivatives of fullerenes C₆₀ and C₇₀ were synthesized and characterized. The proposed procedures afford the reaction products in yields twice as high (80–85%) as those attained by the classical Prato reaction. The reactions proceed with virtually complete regio- (in the case of C₇₀) and stereoselectivity to afford only cis-2′,5′-disubstituted and trans-1′,2′,5′-trisubstituted pyrrolidinofullerenes. Pyridyl-substituted pyrrolidinofullerenes react with metalloporphyrins and phthalocyanines to form self-ordered coordination complexes. The latter are analogs of natural photosynthetic antenna systems due to photoinduced charge separation that occurs in these complexes upon exposure to light. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 873–898, May, 2008.     

Isomerization kinetics of carbon clusters 1. Potential of interatomic interaction

Formation of fullerenes — spherical carbon clusters C₆₀ and clusters of other sizes — during condensation of carbon vapors has not yet received theoretical explanation. Recent experimental works concerned with cluster formation in carbon vapors have established that during condensation carbon atoms form rings and then polycyclic clusters, which are precursors of fullerenes. Theoretical investigation of the spontaneous formation of fullerenes from polycyclic rings calls for a simple model of the potential of interatomic interaction of carbon, which would allow fast calculations of bond energies and statistical sums of the clusters. We use the modified Brenner potential, which was developed for hydrocarbon molecules. The parameters of the potential are refitted according to the results of quantum chemical calculations. Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences. Institute of Computation Technologies, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Struktumoi Khimii, Vol. 37, No.4, pp. 664–670, July–August, 1996. Translated by I. Izvekova     

Determination of the rate constants of addition of.P(O)(OPri)2 radicals to fullerenes C60 and C70

The rate constants of the addition of phosphoryl radicals to fullerenes C₆₀ and C₇₀ were determined by the method of competitive reactions. The phosphoryl radicals were shown to be 1.5–3 orders of magnitude more reactive than the carbon-centered radicals. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1652–1655, September, 2000.     

Solubility of light fullerenes in vegetable oils

Polythermal (in the temperature range 0−80°C) solubility of light fullerenes (C₆₀ and C₇₀), and also of fullerene mixtures (65% C₆₀, 34% C₇₀, and 1% C_76–90) in vegetable oils (of unrefined and refined sunflower, corn, olive, linen, apricot, grape, cedar, and walnut) was studied; the corresponding solubility polytherms are given and characterized.     

Effect of the iron content on the properties of a zirconium dioxide catalyst in the hydrogenation of carbon monoxide

The hydrogenation of Co on zirconium dioxide catalysts containing from 0 to 10 mass % iron was studied. Small additions of iron up to about 0.5 mass % promote the ZrO₂ catalysts relative to the formation of C₂–C₄ olefins. In the presence of large iron additives, the catalyst operates as a complex metal-oxide system featuring interaction of its components. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 153–158, May–June, 1997.     

Separation of C60 and C70 fullerenes on silica modified by polyaromatic and π-acid aromatic compounds

Separation of C₆₀ and C₇₀ fullerenes by HPLC was studied using sorbents synthesized by reaction of perylenedicarboxylic anhydride, dimethoxyviolanthrene, the tetramer of chromotropic acid with formaldehyde (TCA), trinitrobenzoyl chloride, or chlorotrinitrobenzene with γ-aminopropyl silica. These sorbents possess satisfactory chromatographic properties. The sorbent based on TCA is effective for separation of preparative amounts of fullerenes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1544–1546, August, 1997.     

A combination of Clar number and Kekulé count as an indicator of relative stability of fullerene isomers of C<Subscript>60</Subscript>

Kekulé count is not as useful in predicting the thermodynamic stability of fullerenes as it is for benzenoid hydrocarbons. For example, the Kekulé count of the icosahedral C₆₀, the most stable fullerene molecule, is surpassed by its 20 fullerene isomers (Austin et al. in Chem Phys Lett 228:478–484, 1994). This article investigates the role of Clar number in predicting the stability of fullerenes from Clar’s ideas in benzenoids. We find that the experimentally characterized fullerenes attain the maximum Clar numbers among their fullerene isomers. Our computations show that among the 18 fullerene isomers of C₆₀ achieving the maximum Clar number (8), the icosahedral C₆₀ has the largest Kekulé count. Hence, for fullerene isomers of C₆₀, a combination of Clar number and Kekulé count predicts the most stable isomer.     

Rate constants for the formation and decomposition of the σ-adduct in the reactions of N-arylpyridinium salts

The rate constants for the formation (k₁) and decomposition (k ₋₁ ,k ₂ ,k ₃ ) of the σ-adduct were determined for the reactions of 4-R-N-(2,4-dinitrophenyl)pyridinium salts [R=Py, CON(C₂H₅)₂] with 4-methoxyaniline, which takes place by the ANRORC substitution mechanism. L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 282–285, September–October, 1998.     

Separation of C1–C4 hydrocarbon gases on impregnated liquid membranes

Diffusion plays an important role along with complexation in the separation of C₁–C₄ hydrocarbon gases on copper-containing impregnated liquid membranes. The partition factor changes as the process goes from nonsteady-state to steady-state. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 191–195, May–June, 1998.     

Factors determining selectivity of ethylene conversion to butadiene over aluminosilicate catalyst

A study has been made of the influence of temperature, partial pressure of C₂H₄, and contact time on the selectivity of direct conversion of ethylene to butadiene over an aluminosilicate catalyst. A critical analysis has been made of the competing directions of C₂H₄ conversion, which determine the selectivity of C₄H₆ formation under conditions of a heterogeneous-homogeneous mechanism in carrying out the process. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine, 31 Nauka Prospect, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 78–82, March–April, 1997.     

Nonlinear optical properties of solutions of heavy fullerenes in the near-ultraviolet region

Nonlinear optical properties (particularly optical limiting) are determined for solutions of heavy fullerenes C₇₆ + C₇₈ + C₈₄ + C₉₀ + …, in the near-ultraviolet region (λ ≈ 280 ± 7 nm). It is shown that no optical limiting is observed in solutions of light fullerenes (C₆₀ and C₇₀), but found in solutions of water-soluble fullerenol-d (a mixture of oxypolyalcohols of fullerene C₆₀-C₆₀(OH) _n1O _n2, with their sodium salts) based on light fullerenes.     

Endohedral chemical shifts in higher fullerenes with 72–86 carbon atoms

For all isolated pentagon isomers of the fullerenes C₆₀–C₈₆ with nonzero HOMO–LUMO gap and for one nonclassical C₇₂ isomer (C_{2 v} ), endohedral chemical shifts have been computed at the GIAO-SCF/3-21G level using B3LYP/6-31G* optimized structures. The experimental ³He NMR signals are reproduced reasonably well in cases where assignments are unambiguous (e.g. C₆₀, C₇₀ and C₇₆). On the basis of the calculated thermodynamic stability order and the comparison between the computed and experimental ³He chemical shifts, the assignments of the observed ³He NMR spectra are discussed for all higher fullerenes, and new assignments are proposed for one C₈₂ and one C₈₆ isomer (C₈₂:3 and C₈₆:17). The calculated helium chemical shifts also suggest the reassignment of the δ(³He) resonances of two C₇₈ isomers. Received: 26 March 2001 / Accepted: 10 May 2001 / Published online: 11 October 2001     

Spectroscopic and Theoretical Investigations on Supramolecular Interaction of a Newly Designed Monoporphyrin with Fullerenes and Functionalized Fullerenes in Solution

The present paper reports the results of a photophysical investigation of a designed monoporphyrin (1) and its supramolecular complexes with C₆₀, C₇₀ and derivatized fullerenes, namely tert-butyl-(1,2-methanofullerene)-61-carboxylate (2) and [6,6]-phenyl C₇₁ butyric acid methyl ester (3) in toluene. UV–vis studies reveal appreciable ground state interaction between the fullerenes and compound 1. Steady state fluorescence studies show quenching of fluorescence of 1 in the presence of fullerenes. The binding constants of the C₆₀/1, C₇₀/1, 2/1 and 3/1 complexes are estimated to be 300, 20770, 1150 and 13170 dm³⋅mol⁻¹, respectively. Molecular mechanics calculations in vacuo evoke the stereoscopic structures of the fullerene/1 complexes and allow interpretation of the stability difference among various fullerene complexes of 1 in terms of their enthalpies of formation.     

Fusing C60 units without Stone–Wales bond rotations

Abstract  

Using ab-initio calculation, we have explored new chemical paths for the coalescence of C₆₀ units into higher fullerenes and novel structures. Besides the Stone–Wales paradigm used for rationalizing the fusion of fullerenes and nanotubes, we demonstrated that an alternative path exists for the fusion of two C₆₀ units. This path uses successive “π–π” additions and subsequent bond reorganizations to lead to a specific C₁₂₀ peanut-like structure. The energies of the chemical barriers, the intermediate structures, and the final product are markedly lower than their counterparts found in the chemical paths based on Stone–Wales bond rotations. The results rationalize the existence of a temperature range in which peanut-like structures are obtained during thermal treatment of peapod structures.     

X-ray spectra and electronic structure of K x C60

Highly resolved CK_α spectra of the compounds K₃C₆₀ and K₆C₆₀ synthesized by thermal decomposition of potassium azide in a vacuum chamber of an X-ray tube were obtained. The possibility of monitoring the extent of intercalation of fullerenes by the CK_α spectra is demonstrated. The results are compared with the MNDO calculations for K₆C₆₀. The data are used to construct a diagram of the structure of the highest occupied and C1s levels in the series C₆₀−K₃C₆₀−K₆C₆₀. Deceased. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 3, pp. 514–519, May–June, 1996.     

Effect of the nature of the support on the activity of palladium catalysts for oxidation of carbon monoxide

We have studied the catalytic activity of TiN_0.65, TiO₂, Al₂O₃, and palladium catalysts supported on them in the oxidation of carbon monoxide. The order in which the activities of the supported catalysts vary, Pd/Al₂O₃>Pd/TiO₂>Pd/TiN_0.65, is the reverse of the activity series for the supports. This is explained by the effect of transfer of electron density from the palladium to the substrate. Taras Shevchenko Kiev University, 64 Vladimirskaya ul., Kiev 252033, Ukraine, G. V. Kurdyumov Institute of the Physics of Metals, National Academy of Sciences of Ukraine, 36 Akademika Vernadskogo bul’var, Kiev-142 252642, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 118–121, March–April, 1998.     

Gas dynamics in an arc discharge chamber as a factor governing the isolation of C60 and other “magic” fullerenes

A joint analysis of fullerene assembly kinetics and gas flow dynamics in an arc chamber for the production of fullerenes showed that the effective annealing of fullerenes and the evident dominance of “magic” fullerenes C₆₀ and C₇₀ were mainly explained by the difference between the thermal dissociation rates of these and less stable C₆₂ and C₆₈ fullerenes. The percent of “nonmagic” fullerenes was also shown to depend on the structure of the gas flows formed in the arc discharge chamber. The majority of newly formed fullerenes were not immediately removed from the chamber, bur were trapped by closed gas flows. Back in the hot region of the chamber, fullerenes were simultaneously annealed and dissociated under the action of high temperature and, partially, UV radiation. The “nonmagic” fullerenes were most actively suppressed in a non-pumpable discharge chamber.     

The effect of sulfur dioxide on the activity of modified mordenites in the selective reduction of Nox

The results of a comparative investigation into the activity of modified natural and synthetic mordenites in the selective reduction of NO_x by C₁ and C₃−C₄ hydrocarbons (methane and a propane-butane mixture), the effect of sulfur dioxide on the process, and the acidic characteristics of the mordenites by temperature programmed desorption of ammonia and IR spectroscopy are presented. Sulfur dioxide has practically no effect on the selective reduction of NO_x by C₃−C₄ hydrocarbons at the H forms of synthetic and previously recationized natural mordenites but substantially retards the process at the Cu-, Co-, and Cr-substituted forms and palladium-containing mordenites. The decrease in the concentration of the strong B centers in the transition from the hydrogen to the copper-containing form of the mordenites reduces their activity in selective reduction. Prior recationization of natural mordenites increases their activity, stability, and resistance to the action of sulfur dioxide. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 119–124, March–April, 1999.     

Occupation of trigonal vacancies and the spatial structure of superfullerides

It is assumed that occupation of small trigonal vacancies in the fcc, bcc, and hcp lattices of C₆₀ clusters leads to formation of superfulleride phases. Specific energies of 59 different phases are calculated. These data for fullendes are in agreement with their observed stability. The fcc cluster A₉C₆₀ and the bcc cluster A₁₂C₆₀ are predicted to be the most stable superfullerides. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1122–1129, November–December, 1997.