Effect of high pressures and temperatures on carbon nano-onion structures: comparison with C<Subscript>60</Subscript>

The results of investigations of the structure and properties of carbon nano-onions before and after high-pressure high-temperature (HPHT) treatment are presented. The onion structures are retained after HPHT treatment up to 15 GPa and 1450 °C, which was confirmed by X-ray diffraction, electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The HPHT treatment was shown to increase the hardness and the density of these carbon forms due to the formation of sp³-hybridized carbon atoms.     

Selective Iridium‐Catalyzed Alkylation of (Hetero)Aromatic Amines and Diamines with Alcohols under Mild Reaction Conditions

Selective amine alkylation : A P,N‐ligand‐stabilized iridium complex has been used as an efficient catalyst for the alkylation of (hetero)aromatic amines with alcohols at mild reaction temperatures and catalyst loadings as low as 0.1 mol % Ir (see scheme). The excellent selectivity of the catalyst for monoalkylation of the amine function has also been exploited for the N,N′‐dialkylation of diamines in both symmetric and nonsymmetric fashions.

     

Effect of high-pressure high-temperature treatment on the structure of a hexagonal modification of fullerite C<Subscript>60</Subscript>

Powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular dynamics have been employed to investigate structural transformations in hexagonal and cubic modifications of fullerite C₆₀ after the action of high pressure (4 GPa) within the temperature range 20–1450°C. It has been found that fullerene molecules polymerize to afford polymer structures only in the case of face-centered cubic samples. Under the effect of high pressure and temperature, fullerite C₆₀ with a hexagonal close-packed structure is initially transformed into the cubic modification and, then, forms polymerized structures, which, during an increase in the treatment temperature, become less stable and ordered than the same polymerized structures obtained directly from cubic fullerite C₆₀. X-ray photoelectron spectroscopy measurements suggest deformation of the cages of fullerene molecules in the polymerized structures.     

Single and Double C?Cl‐Activation of Methylene Chloride by P,N‐ligand Coordinated Rhodium Complexes

Two in one : The simultaneous formation of bimetallic μ‐methylene bridged Rh^III complexes as well as dimeric Rh^III complexes with terminal chloromethyl groups is observed for P,N‐ligand stabilized Rh^I complexes by C? Cl bond activation of methylene chloride. A mechanistic proposal for the formation of both activation products is also discussed.

     

Structural models of the [Fe4S4] clusters of homologous nitrogenase Fe proteins

The iron (Fe) proteins of molybdenum (Mo)-, vanadium (V)-, and iron (Fe)-only nitrogenases are encoded by nifH, vnfH, and anfH, respectively. While the nifH-encoded Fe protein has been extensively studied over recent years, information regarding the properties of the vnfH- and anfH-encoded Fe proteins has remained scarce. Here, we present a combined biochemical, electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) analysis of the [Fe(4)S(4)] clusters of NifH, VnfH, and AnfH of Azotobacter vinelandii . Our data show that all three Fe proteins contain [Fe(4)S(4)] clusters of very similar spectroscopic and geometric structural properties, although NifH differs more from VnfH and AnfH with regard to the electronic structure. These observations have an interesting impact on the theory of the plausible sequence of evolution of nitrogenase Fe proteins. More importantly, the results presented herein provide a platform for future investigations of the differential activities of the three Fe proteins in nitrogenase biosynthesis and catalysis.     

Reductive carbodiazenylation of nonactivated olefins via aryl diazonium salts

[Structure: see text] The reduction of aryl diazonium salts in the presence of nonactivated olefins provides rapid entry to carbodiazenylation products. The regioselective functionalization of double bonds is achieved in a one-pot process starting from aniline derivatives. Carboamination of olefins is possible via a two-step carbodiazenylation-hydrogenation sequence in which one aniline equivalent is recovered.     

The Brunt–Väisälä frequency of rotating tokamak plasmas

The continuous spectrum of analytical toroidally rotating magnetically confined plasma equilibria is investigated analytically and numerically. In the presence of purely toroidal flow, the ideal magnetohydrodynamic equations leave the freedom to specify which thermodynamic quantity is constant on the magnetic surfaces. Introducing a general parametrization of this quantity, analytical equilibrium solutions are derived that still posses this freedom. These equilibria and their spectral properties are shown to be ideally suited for testing numerical equilibrium and stability codes including toroidal rotation. Analytical expressions are derived for the low-frequency continuous Alfvén spectrum. These expressions still allow one to choose which quantity is constant on the magnetic surfaces of the equilibrium, thereby generalizing previous results. The centrifugal convective effect is shown to modify the lowest Alfvén continuum branch to a buoyancy frequency, or Brunt–Väisälä frequency. A comparison with numerical results for the case that the specific entropy, the temperature, or the density is constant on the magnetic surfaces yields excellent agreement, showing the usefulness of the derived expressions for the validation of numerical codes.     

Chemically Induced Dynamic Nuclear Polarization VIII: Thermal decomposition of dibenzoyl peroxides in solution [1]

Thermolysis of di-(4-chlorobenzoyl)-peroxide was carried out in the probe of an NMR. spectrometer. The dependence of product distribution and chemically induced dynamic nuclear polarization (CIDNP.) patterns on the concentrations of radical trapping agents gives evidence that the CIDNP. effects are caused by singlet-triplet transitions, dependent on nuclear spin, in transient benzoyloxy/phenyl radical pairs and by the selective formation of radical products from singlet state pairs.     

A New Catalytic Reaction for Determining Phenothiazine Derivatives

The oxidation of phenetidine with sodium vanadate is proposed for determining phenothiazine derivatives by the kinetic method. The reaction rate was studied depending on the solution acidity and reagent concentrations, and the optimum determination conditions were selected. The analytical range was 3–100 ng/mL for six phenothiazine alkyl derivatives (aminazine, diprazine, promazine, meterazine, tisercine, and triphtazine). The detection limits (3 to 10 ng/mL) depend on the substituent in the phenothiazine molecule. The relative standard deviations were from 3 to 20%.