Redox-induced hydrogen transfer from hydrofullerene C60H36 to fullerene C60

The possibility of hydrogen transfer from hydrofullerene C₆₀H₃₆ to electrogenerated radical anion C₆₀ ^.− or dianion C₆₀ ²⁻ in propylene carbonate-toluence (3∶2, v/v) was demonstrated by cyclic voltammetry. The process affords C₆₀H₂ as the product. The reaction found is the typical redox-induced process. Translated fromIzvestiya Akodemii Nauk. Seriya Khimicheskaya, No. 6, pp. 1136–1139, June, 1998.     

HPLC separations of meropenem and selected pharmaceuticals using a polar endcapped octadecylsilane narrow bore column

Summary Stability indicating high performance liquid chromatography methods have been developed for the assay of meropenem in combination with either dopamine (A), aminophylline (B), metoclopramide (C) or ranitidine (D) in intravenous fluid mixtures. Separations B, C and D were performed on a polar endcapped ODS column (150×2 mm) with aqueous, pH 3.0—acetonitrile (89∶11, 88∶12, and 92∶8) eluent and detection at 270, 290, 317 nm respectively. Meropenem was linear over the concentration ranges 126.88–507.50, 131.25–525, and 131.25–525 gmg mL⁻¹. Aminophylline, metoclopramide and ranitidine were linear over the concentration ranges 13–52, 37.5–150, and 25–100 μg mL⁻¹. Separation A was performed on a conventional ODS column (150×2.1 mm) with aqueous, pH 3.0—acetonitrile (85∶15) eluent and detection at 280 nm. Meropenem and dopamine were linear in the 61.25–245 and 10–40 μg mL⁻¹ ranges, respectively. Accuracy and precision for all methods were 0.20–3.30% and 0.10–1.58%, respectively. Accelerated stability studies have been carried out on each drug by exposure to acid, base, H₂O₂, and heat for different time periods.     

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.     

Electrochemical behavior and parameters of hydrofullerene C60H36

Electrochemistry of hydrofullerene C₆₀H₃₆ was studied by cyclic voltammetry in THF and CH₂Cl₂ in the −47–14 °C temperature range. Hydrofullerene undergoes reversible one-electron reduction to form a radical anion in THF (E ⁰=−3.18 V (Fc⁰/Fc⁺), Fc=ferrocene) and irreversible one-electron oxidation in CH₂Cl₂ (E _p ^a =1.22 V (Fc⁰/Fc⁺)). The reduction potential was used to estimate electron affinity of hydrofullerene as EA=−0.33 eV. It was suggested that C₆₀H₃₆ is an isomer withT-symmetry in which 12 double bonds form four isolated benzenoid rings located in vertices of an imaginary inscribed tetrahedron on the molecular surface. For hydrofullerene, the “electrochemical gap” is an analog of the energy gap (HOMO−LUMO), equal to (E ^Ox−E ^Red)=4.4 V, and indicates that C₆₀H₃₆ is a sufficiently “hard” molecule with a low reactivity in redox reactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2083–2087, November, 1999.     

Thermochemistry of Bu<Subscript>4</Subscript>NBr solutions in binary solvents containing formamide

The heats of solution of tetrabutylammonium bromide have been measured in mixtures of formamide (FA) with methanol (MeOH) and ethylene glycol (EG) at 313.15 K by calorimetric method. The standard enthalpies of solution in binary mixtures have been extrapolated to infinite dilution by Redlich–Rosenfeld–Meyer type equation using the literary data at 298.15 K and the present paper data at 313.15 K. The Debye–Hückel limiting law slope A _H required for calculation of the ∆_sol H ⁰ value has been obtained with application the new additive scheme of determination of the physic-chemical characteristics of binaries. The scheme is tested on the example of Bu₄NBr solutions in FA–MeOH mixture at 298.15 K. Its application yields the ∆_sol H ⁰ value very closed on the ones determined with the real (non-additive) characteristics of binaries. The standard enthalpies of solution extrapolated by Redlich–Rosenfeld–Meyer type equation are in a good agreement with the ones computed in terms of the Debye–Hückel theory in the second approximation. The heat capacities characteristics of Bu₄NBr have been calculated in H₂O–FA, MeOH–FA and EG–FA mixtures using the literary and present data. The sequence of solvents H₂O > FA > EG > MeOH located on their ability to solvophobic solvation found by us earlier for enthalpic characteristics is confirmed by the ∆C _p ⁰ values. The comparison of thermochemical characteristics of Bu₄NBr solutions in aqueous and non-aqueous mixtures containing FA has been carried out. The own structure of water remains in the region of small additions of formamide to co-solvents. It considerably differs the H₂O–FA mixture from the investigated non-aqueous systems.     

Determination of clozapine in human plasma by solid-phase extraction and liquid chromatography with amperometric detection

Summary A sensitive and selective high-performance liquid chromatographic method has been developed for monitoring clozapine levels in human plasma. Chromatography was performed on a reversed-phase column (C₈, 150 mm×4.6 mm i.d., 5 μm) with acetonitrile-aqueous sodium acetate solution, 88∶12 (v/v), as mobile phase; the flow rate was 1 mL min⁻¹. Clozapine oxidation at +800 mV was detected amperometrically. Response was linearly dependent on concentration over the range 50–1500 ng mL⁻¹ clozapine in plasma. Sample preparation by solid-phase extraction before HPLC analysis gave high extraction yield (94%). The accuracy and precision of the method were both very good (recovery: 97%;RSD<3.3%).     

Influence of injection parameters on column performance in nanoscale high-performance liquid chromatography

Summary The influence of the injection volume and the sample solvent on column efficiency has been evaluated in packed nano liquid chromatography using columns 150μ i.d. Evaluation of column performance was by means of reduced plate height (h) versus reduced velocity (v) for four polyaromatic hydrocarbon test compounds (PAHs). When compounds are dissolved in a weak solvent (such as MeCN: H₂O, 30∶70), and whatever the injection volume −60 or 200 nL-a gain in efficiency can be observed due to the well-known on-column focusing phenomenon, but keeping constant solute retention factors. Under optimized conditions (flow rate: 150 nLmin⁻¹, solvent sample MeCN: H₂O, 30∶70, injection volume 200 nL), a reduced plate height of 1.83 has been obtained for a 15 μm C₁₈ packing corresponding to 36000 plates m⁻¹, which illustrates the absence of any extracolumn band broadening under nano LC conditions.     

Synthesis of formamidines from 2-amino-3-methylquinazolin-4-one and its 6-nitro derivative

The condensation of 2-amino-3-methylquinazolin-4-one and its 6-nitro derivative with dialkyl-, arylalkyl-, and heterylformamides has given the corresponding formamidines of the quinazolinone series. The details of the compounds synthesized are as follows X, R, R′, yield (%), mp (°C, ethanol), R_f (chloroform-methanol (20:1) Al₂O₃): empirical formula: H, CH₃, CH₃, 77, 238–240, 0.49, C₁₂H₁₄ON₄; H, C₂H₅, C₂H₅, 65, 208–210, 0.96, C₁₄H₁₈ON₄; H, CH₃, C₆H₅, 84, 162–164, 0.54, C₁₇H₁₆ON₄; H, (CH₂)₂O(CH₂)₂, 60, 196–197, 0.43, C₁₄H₁₆O₂N₄; H, (CH₂)₅, 6.6, 196–198, 0.4, C₁₅H₁₈·ON₄; NO₂, CH₃, CH₃, 64. 194–196, 0.83, C₁₂H₁₃O₃N₅; NO₂, C₂H₅, C₂H₅, 37, 142–144, 0.8, C₁₄H₁₇O₃N₅; NO₂; CH₃, C₆H₅, 38, 298, 0.88, C₁₇H₁₅O₃N₅; NO₂, (CH₂)₂O(CH₂)₂, 60, 148–150, 0.7, C₁₄H₁₅O₄N₅. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 680–684, September–October, 1980.     

Magnetic properties of fullerene salts containing d- and f-metal cations (Co2+, Ni2+, Fe2+, Mn2+, Eu2+, Cd2+). Specific features of the interaction between C60·? and the metal cations

The interaction between the radical anions C₆₀ ^·− and divalent d- and f-metal (Co, Fe, Ni, Mn, Eu, Cd) cations in DMF and acetonitrile-benzonitrile (AN-BN) mixture was studied. Black solid polycrystalline salts (C₆₀ ^·−)₂{(M²⁺)(DMF) _x } (x = 2.4–4, 1–6) containing the radical anions C₆₀ ^·− and metal(ii) cations solvated by DMF were prepared for the first time and their optical and magnetic properties were studied. The salts containing Co²⁺, Fe²⁺, and Ni²⁺ are characterized by antiferromagnetic interactions between the radical anions C₆₀ ^·−, which result in unusually large broadening of the EPR signal of C₆₀ ^·− upon lowering the temperature (from 5.55–12.6 mT at room temperature to 35–40 mT at 6 K for Co²⁺ and Ni²⁺). The salts containing Mn²⁺ and Eu²⁺ form diamagnetic dimers (C₆₀ ⁻)₂, which causes a jumpwise decrease in the magnetic moment of the complexes and disappearance of the EPR signal of C₆₀ ^·− in the temperature range 210–130 K. A feature of salt 6 is magnetic isolation of the radical anions C₆₀ ^·− due to the presence of diamagnetic cation Cd²⁺. The salts prepared are unstable in air and decompose in o-dichlorobenzene or AN. Reactions of C₆₀ ^·− with metal(ii) cations in AN-BN mixture result in decomposition products of the salts that contain neutral fullerene dimers and metals solvated by BN. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1909–1919, September, 2008.     

Photodissociation spectrum of cyanobenzene dimer cation. Absence of intermolecular resonance interaction

Electronic spectra of a homo-molecular dimer cation, (C₆H₅CN)₂ ⁺, are measured by photodissociation spectroscopy in the gas phase. Broad features appeared in the 450–650 nm region are characteristic of π₃ → π_CN transitions of the C₆H₅CN⁺ chromophore. No intense band is observed in the 650–1300 nm region, where other aromatic dimer cations usually show charge resonance bands. Two component molecules of (C₆H₅CN)₂ ⁺ cannot take a parallel sandwich configuration suitable for the resonance interaction, because of geometrical constraints due to other stronger interactions.     

Reactions of [Cp*Ru(H<Subscript>2</Subscript>O)(NBD)]<Superscript>+</Superscript> with diynes

Abstract  Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H₂O)(NBD)][BF₄] (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂. The reaction of [Cp*Ru(H₂O)(NBD)][BF₄] with 1,4-diphenylbutadiyne generates the unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C₉H₈–Ph in addition to the organometallic compound [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄]. [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BPh₄]₂ is generated after the reaction of compound [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂ with Na[BPh₄]. The structure of this compound was confirmed by X-ray diffraction. A possible approach to form Ph–C≡C–C₉H₈–Ph and [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄] is suggested. Graphical Abstract  Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H₂O)(NBD)]BF₄ (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂. The reaction of [Cp*Ru(H₂O)(NBD)][BF₄] with 1,4-diphenylbutadiyne simply generates unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C₉H₈–Ph in addition to the organometallic compound [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄]. [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BPh₄]₂ is generated after the reaction of compound [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂ with Na[BPh₄]. The structure of this compound was confirmed by X-ray diffraction. And the possible approach to form Ph–C≡C–C₉H₈–Ph and [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄] was suggested. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dissociative Excitation of C2H2 in the Electron Cyclotron Resonance Plasma of Ar: Production of CH(A2Δ) Radicals and Formation of Hydrogenated Amorphous Carbon Films

The dissociative excitation reaction of C₂H₂ with the electron-cyclotron resonance plasma of Ar was investigated based on the electrostatic-probe measurements and on the optical emission spectroscopy of the CH(A²Δ–X²Π) transition. The density, n _e, and the temperature, T _e, of free electrons were controlled by adding H₂O molecules externally into the reaction region, and the dependence of the CH(A²Δ–X²Π) emission intensity on the addition of H₂O was observed to compare with the evaluated dependencies based on n _e and T _e. The mechanism of production of CH(A²Δ) was found, predominantly, to be the electron impact with the contribution of 10–20% of the electron-impact dissociation of C₂H radicals; the contribution of the ion–electron recombination was negligible. Hydrogenated amorphous carbon films were fabricated using the same reaction system. The atomic compositions, Raman spectra, and the hardness of films were discussed in terms of the variations of n _e and T _e upon the addition of H₂O molecules.     

A computational study of the radical–radical reaction of O(<Superscript>3</Superscript>P) + C<Subscript>2</Subscript>H<Subscript>5</Subscript> with comparisons to gas-phase kinetics and crossed-beam experiments

We present density functional theory (DFT) and complete basis set (CBS) calculations of the prototypical radical–radical reaction of ground–state atomic oxygen [O(³P)] with ethyl (C₂H₅) radicals. The respective reaction mechanisms and dynamics were investigated on the doublet potential energy surfaces using the DFT method and CBS model. In the title reaction, the barrierless addition of O(³P) to C₂H₅ led to the formation of energy-rich intermediates that underwent subsequent isomerization and decomposition to yield various products. The products predicted to be found were: H₂CO + CH₃, CH₃CHO + H, c–CH₂OCH₂ + H, ^1,3CH₃COH + H, ^1,3HCOH + CH₃, CH₂CHOH + H, C₂H₃ + H₂O, and CH₂CH₂ + OH. In particular, unlike previous kinetic results, proposed to proceed only through the direct H-atom abstraction process, two distinctive pathways to the formation of CH₂CH₂ + OH were predicted to be in competition: direct, barrierless H-atom abstraction mechanism versus addition process. The competition was consistent with the recent crossed-beam investigations, and their microscopic dynamic characteristics are discussed at the molecular level.     

Optimization of a high-performance liquid chromatography method to quantify bilirubin and separate it from its photoproducts

A rapid reversed-phase (RP) high-performance liquid chromatography method for the isolation of bilirubin from its photoproducts (e.g., biliverdin) is reported. The method is based on isocratic elution using methanol:water as the mobile phase. A 2⁴ full-factorial experimental design approach was adopted. For the optimization, the best separation was obtained using a flow rate of 1.50 mL/min, a mobile phase of 99∶1 methanol:water (v/v) at pH 3.60, and a 150×4.6 mm id RP (C₁₈) column containing 5-μm particles. These conditions produced the fastest total retention time of 3.38±0.055 min, and other chromatographic parameters were acceptable. Under the optimum conditions, a linear calibration curve for bilirubin was obtained over the 1.0–40.0 μg/L concentration range studied. The limit of quantification was 0.79 g/L and the limit of detection was 0.24 μg/L. Bilirubin in solution was monitored by ultraviolet detection at 450 nm.     

Corannulene derivatives as models for calculations of fullerene derivatives

Hypothetical derivatives of corannulene C₂₀H₁₀ (Cor), namely, CorX₅ ^• radicals, CorX₅ ⁻ anions (X=H, Cl, or Br), and their η⁵-π-complexes with SiCp, were calculated by the MNDO/PM3 method. The possibilities of using the results of these calculations for modeling the electronic structure and geometry of fragments of the analogous complexes of the fullerene derivatives C₆₀X₅ are discussed. Calculations of C₆₀X₅ ^• radicals and C₆₀X₅ ⁻ anions were also carried out. In all the compounds under study, the X atoms are attached to carbon atoms in α positions with respect to the same five-membered ring. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1268–1272, July, 1997.     

Destruction of Freon HFC-134a Using a Nozzleless Microwave Plasma Source

In this paper, results of the pyrolysis of Freon HFC-134a (tetrafluoroethane C₂H₂F₄) in an atmospheric pressure microwave plasma are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to produce plasma for the destruction of Freon HFC-134a. The processed gaseous Freon HFC-134a at a flow rate of 50–212 l min⁻¹ was introduced to the plasma by four gas ducts which formed a swirl flow in the plasma reactor (a quartz cylinder). The absorbed microwave power was 0.6–3 kW. The experimental results showed that the Freon was converted into carbon black, hydrogen and fluorine. The total conversion degree of HFC-134a was up to 84% with selectivity of 100% towards H₂, F₂ and C₂, which means that there was no conversion of HFC-134a into other hydrocarbons. The Freon destruction mass rate and corresponding energetic mass yield were up to 34.5 kg h⁻¹ and 34.4 kg per kWh of microwave energy absorbed by the plasma, respectively.     

Conversion of natural gas to C2 hydrocarbons through dielectric-barrier discharge plasma catalysis

The experiments are carried out in the system of continuous flow reactors with dielectric-barrier discharge (DBD) for studies on the conversion of natural gas to C₂ hydrocarbons through plasma catalysis under the atmosphere pressure and room temperature. The influence of discharge frequency, structure of electrode, discharge voltage, number of electrode, ratio of H₂/CH₄, flow rate and catalyst on conversion of methane and selectivity of C₂ hydrocarbons are investigated. At the same time, the reaction process is investigated. Higher conversion of methane and selectivity of C₂ hydrocarbons are achieved and deposited carbons are eliminated by proper choice of parameters. The appropriate operation parameters in dielectric-barrier discharge plasma field are that the supply voltage is 20–40 kV (8.4–40 W), the frequency of power supply is 20 kHz, the structure of (b) electrode is suitable, and the flow of methane is 20–60 mL · min⁻¹. The conversion of methane can reach 45%, the selectivity of C₂ hydrocarbons is 76%, and the total selectivity of C₂ hydrocarbons and C₃ hydrocarbons is nearly 100%. The conversion of methane increases with the increase of voltage and decreases with the flow of methane increase; the selectivity of C₂ hydrocarbons decreases with the increase of voltage and increases with the flow of methane increase. The selectivity of C₂ hydrocarbons is improved with catalyst for conversion of natural gas to C₂ hydrocarbons in plasma field. Methane molecule collision with radicals is mainly responsible for product formation.     

New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multinuclear NMR investigation on organometallic gold(III) pentafluorophenylarylazoimidazole complexes

Reaction of [Au(C₆F₅)(tht)₂Cl](OTf) with RaaiR′ in CH₂Cl₂ medium leads to [Au(C₆F₅)(RaaiR′)Cl](OTf) [RaaiR′ = p-R–C₆H₄–N=N–C₃H₂–NN-1-R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), tht is tetrahydrothiophen]. The maximum molecular peak of [Au(C₆F₅)(MeaaiMe)Cl] is observed at m/z 599.51 (100 %) in the FAB mass spectrum. Ir spectra of the complexes show –C=N– and –N=N– stretching near at 1590 and 1370 cm⁻¹ and near at 1510, 955, 800 cm⁻¹ due to the presence of pentafluorophenyl ring. The ¹H-NMR spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph shows AB type quartets. ¹³C-NMR spectrum of complexes confirm the molecular skeleton. In the ¹H-¹H-COSY spectrum as well as contour peaks in the ¹H-¹³C HMQC spectrum for the present complexes, assign the solution structure and stereoretentive conformation. The electrochemistry gives the ligand reduction peaks.     

Heteroatom derivatives of aziridine

Reaction of ethyleneimine with boron trichloride and tribromide below −20° C, with reactants in ratios 1∶1 and 2∶1, gives labile N-β-halo-genoethyl-substituted halogenoborazenes of the types XCH₂CH₂NHBX₂ and (XCH₂CH₂NH)₂BX (X = Cl, Br). These compounds decomposed spontaneously on coming to room temperature, with the evolution of HX and formation of substances whose compositions are, respectively C₂H₄NBX₂ and C₄H₉N₂BX₂. With a 3∶1 ratio of reactants the product is the relatively stable tris(β-halogenoethylamino)borane (XCH₂CH₂NH)₃ B (X = Cl, Br), which loses only one molecule of HX when heated under vacuum. For Part V see [1].