Solvent effects on oxygen atom transfer reaction between manganese(V)-oxo corrole and alkene

Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo (F₁₅CMn（V）-oxo),5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo(F₁₀CMn（V）-oxo),5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F₅CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F₀CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.     

β-Octafluorinated tetrakis(ethoxycarbonyl)porphyrin

Tetrakis(alloxycarbonyl)porphyrin and its β-octafluoro-substituted derivatives were synthesized via Lindsey method and transformed to their zinc complexes.Single crystal X-ray structures of corresponding Zn(Ⅱ) porphyrins revealed that β-octafluorination will give more compactness of porphyrin moieties in the crystal structure owing to the hydrogen bonding interactions involving β-fluorine atoms.An unusual six-coordinated Zn(Ⅱ) was found via intramolecular coordination of oxygen atom of meso-substituents with central Zn(Ⅱ).     

Magnetic disaccommodation in Sr hexagonal ferrites with X-phase (2SrO·15Fe2O3) initial composition

The relaxation of the initial permeability has been measured in polycrystalline Sr hexaferrites with the initial composition of X-phase (2SrO·15Fe₂O₃) in the temperature range between 80 and 500 K. The time decay of the initial permeability after sample demagnetization is represented by means of isochronal disaccommodation curves which show the presence of different disaccommodation processes whose maxima lie at 380, 300 and 160 K (resp. A, B and D peaks). This behaviour is explained regarding the spectra corresponding to barium ferrites in order to ascribe the different relaxation processes found for ionic transitions in the cationic sites within the hexagonal structure.     

Magnetic interactions and Preisach distributions of nanostructured barium hexaferrite

Barium hexaferrite (phase M) samples with different nanostructures were studied. Sample M1 is composed of nanocrystals of BaFe₁₂O₁₉ produced after milling the elemental oxides (Fe₂O₃ and BaCO₃) and heating in air atmosphere. Two more samples were produced by milling the same oxides and a 20% excess of -Fe. The resulting powder (composed of phase M and a 20% hematite) was heat-treated in different conditions, resulting in samples MF1 (with a partially sintered structure) and MF8 (with almost completely sintered structure).

In order to have an insight into the interactions in each sample, Preisach distributions were obtained using first-order reversion curves (FORCs) measurements. The Preisach distribution corresponding to M1 is a Gaussian-shaped one, with a maximum around 4.1 kOe. The distribution of MF1 has a narrow and high peak at 5.3 kOe, a number of overlapping small peaks down to 2.6 kOe and a distinct and low-intensity peak at 2 kOe. MF8 has a Preisach distribution with a succession of equally spaced distinct peaks from 4.2 to 1.5 kOe.

The found Preisach distributions suggest that the interactions occur among nanocrystals inside conglomerates with different number of particles.     

Correction to: EQRAIN: uranium and plutonium interlaboratory exercises from 1997 to 2016—comparison to ITVs-2010

Journal of Radioanalytical and Nuclear Chemistry - In the original publication of the article, the values of u(s), u(r) and ITV for HKED were published incorrectly in Table 6.     

Second-derivative UV spectrophotometric assay for determining the degradation kinetics of 3-bromo-N-bromo-N-(3,4-dimethyl-5-isoxazolyl-4-amine)-1,2-naphthoquinone

The application of the second-derivative UV spectrophotometry for determining the stability of 3-bromo-N-bromo-N-(3,4-dimethyl-5-isoxazolyl-4-amine)-1,2-naphthoquinone in ethanolic solutions is described. The validity of this method was evaluated using synthetic mixtures of the intact drug and its degradation products and by statistical analysis of the calibration data. In order to verify the usefulness of this method for stability studies, recovery experiments by the standard addition method were also carried out.     

Mass spectra and thermochemistry of methyl phenanthrenes. A contribution to the analogy between mass spectral and thermal fragmentation reactions

The mass spectra of both nonhindered and sterically hindered methyl phenanthrene derivatives follow the patterns established for other alkyl aromatics. The ‘unimolecular’ thermochemistry of these systems parallels the mass spectral fragmentation in a qualitatively predictable way. Generally the major thermochemical products correspond to one of the five most intense fragment ions, and the importance of products which correspond to ions with high appearance potentials increases with increasing temperature of the thermolysis system. On the basis of this empiricism we have outlined a tentative procedure for anticipating the results of thermolysis experiments based on mass spectral data. The use of appearance potential differences to estimate steric strain energies in the compounds studied did not give satisfactory results.     

Application of FORC distributions to the study of magnetic interactions in ferrites of composition

Magnetic interactions in hexaferrite samples of Ba_1-xLa_x+δFe_12-xCo_xO₁₉ composition were studied. The precursor powders—barium carbonate (BaCO₃), lanthanum oxide (La₂O₃), hematite (Fe₂O₃) and cobalt acetate—were milled for 100 h in air atmosphere and heat-treated for 1 h at . The structural characterization was performed by X-ray diffraction. The FORC distributions show a single peak at high switching fields, indicating that the substituted systems are formed by weakly interacting particles. La excess induces the decoupling of the particles.     

Unexpected one-pot synthesis of A3-type unsymmetrical porphyrin

The first direct synthesis of A₃-type unsymmetrical porphyrin is achieved via conventional pyrrole–aldehyde condensation in a one-pot procedure in an appreciable yield. Generalization of this approach to a variety of other aldehydes revealed that it is advantageous for highly electron-rich aldehydes giving unsymmetrical porphyrin, while electron-poor aldehydes even failed to cyclize under the same experimental conditions.