Cation self-diffusion and impurity diffusion in Fe2O3+

Cation self-diffusion D¹_Fe, parallel to the c axis has been measured as a function of temperature (1100–1300°C) and oxygen partial pressure p_o2 (2 × 10^?3-1 atm) in the same single crystals of Fe₂O₃ as those used by Chang and Wagner. Whereas the p_o2 dependence of D1_Fe, observed by Chang and Wagner has been confirmed, the absolute value of D¹_Fe and the activation enthalpy for self-diffusion are much higher than those reported by them. The various diffusion studies indicate that cation self-diffusion occurs by an interstitial-type mechanism. However, the sample-to-sample variations in D¹_Fe, suggest that all diffusion measurements may have been performed on samples where the defect concentrations are impurity controlled. Impurity diffusion of ⁶⁰Co, ⁵¹Cr, and ⁸⁸Y has also been measured as a function of p_o2 at 1200°C. The results indicate that these impurities diffuse by an interstitialcy mechanism in Fe₂O₃.     

A concise synthesis of monoazaporphyrin from 1,19-dideoxybiladiene-ac

1,19-Dideoxybiladiene-ac was found to be cyclized into monoazaporphyrin in 18-33% yield in the presence of iodine/potassium iodide mixture and ammonium hydroxide or sodium azide as the nitrogen source. The synthesis circumvents the tedious preparation of 1,19-dibromobiladiene-ac for monoazaporphyrin.     

Symmetry-resolved absorption spectra of vibrationally excited CO2 molecules

Symmetry-resolved x-ray absorption spectroscopy has been first carried out on high-temperature molecules. From the angle-resolved ion yield spectra of CO2 both at room temperature and at 430 degrees C, symmetry-resolved absorption profiles of the C 1s(-1) 2pi(u) and O 1s(-1) 2pi(u) resonances have been extracted for the vibrational ground state molecules and bending-vibration excited ones. The profiles change dramatically between them, and the Renner-Teller effect becomes more evident for the vibrationally excited molecules. The effects of the multimode vibronic coupling are suggested for the O 1s(-1) 2pi(u) and O 1s(-1) 3s sigma(g) resonances.     

Bezichung zwischen den chemischen ESCA- und NMR-Verschiebungen von C-Atomen in linearen Polymeren

Ohne Zusammenfassung     

ESCA-Spektren von fluorhaltigen Polymeren und deren Beziehung zum Kristallisationsgrad, zur Oberfl?chenspannung und zurn Gehalt an adsorbierten Gasen

Ohne Zusammenfassung     

A novel fluorescence reagent, 10-hydroxybenzo[h]quinoline-7-sulfonate, for selective determination of beryllium(II) ion at pg cm(-3) levels.

A facile method has been developed for the highly sensitive and selective determination of ultratrace Be(II) ion using a new fluorimetric reagent, 10-hydroxybenzo[h]quinoline-7-sulfonate (HBQS), under extremely alkaline conditions, at pH 12.0. This reagent is quite suitable for the very small ion, Be(II), to form a 6-membered chelate ring, compatible with a high fluorescence yield. The stoichiometry of the chelate is 1:1 for Be-HBQS at pH 12.0. The calibration graph gave a wide linear dynamic range, 2-100 nmol dm(-3) of Be(II) ion with the detection limit (3s blank) of 0.52 nmol dm(-3), or 4.7 pg cm(-3). The excellent sensitivity and toughness toward the matrix influence were demonstrated using the artificial sample solutions for air-dust. Coupled with the simple masking procedure using EDTA, the method enables one to determine Be(II) ion at nanomolar levels in the presence of metals at the natural abundance levels in air-dust samples, typically Al, Ca, Cu, Fe, Mg, Pb, and Zn at 130, 150, 1.0, 70, 33, 3.0, and 8.0 micromol dm(-3), respectively, in the final solution. The proposed method was successfully applied to the determination of Be in urban air.     

Formations and electrochemical behavior of mononuclear and binuclear molybdenum dithiolene complexes with nitrosyl ligands: Evidence for the formation of a coordinatively unsaturated species [CpMo(NO)(dithiolene)]

The one-pot reaction of [Cp^∗Mo(NO)(CO)₂] with elemental sulfur and dimethyl acetylenedicarboxylate (C₂Z₂ (Z = COOMe)) gave the [2+2] cycloadduct of the mononuclear molybdenum dithiolene complex [Cp^∗Mo(NO)(S₂C₂Z₂)(C₂Z₂)] (1), and some binuclear complexes:[Cp^∗Mo(NO)(S₂C₂Z₂)]₂ (2), [Cp^∗₂Mo₂(NO)₂S₂(S₂C₂Z₂)] (3) and [Cp^∗Mo(NO)S₂]₂ (4).The reaction of [Cp^∗Mo(NO)(Cl)(μ-Cl)]₂ with OC{S₂C₂(COOMe)₂} in the presence of sodium methoxide also produced complex 2 and the paramagnetic Cp^∗Mo bisdithiolene complex [Cp^∗Mo(S₂C₂Z₂)₂] (5, Z = COOMe).The structures of complexes 1-5 were determined by X-ray crystal structure analysis.The nitrosyl ligands of complexes 1-4 showed a linear coordination to the molybdenum center (the Mo-N-O bond angles = 169-174°), and their N-O bond lengths were 1.17-1.20 Å.In the binuclear complexes 2-4, two nitrosyl ligands were placed at cis-position.Complexes 1 and 2 were characterized by cyclic voltammetry and spectroelectrochemistry (visible and IR). The electrochemical reduction of the dimeric complex 2 formed the monomeric dithiolene complex[Cp^∗Mo(NO)(S₂C₂Z₂)]⁻ (X⁻) whose lifetime was several minutes. When the anion X⁻ was electrochemically oxidized, the coordinatively unsaturated species X was generated, but it was immediately dimerized to afford the original dimeric complex 2. The reduction of the complex 1 included the elimination of the bridged DMAD moiety (C₂Z₂) to give the anion X⁻.     

Highly Regioselective 5-endo-tet Cyclization of 3,4-Epoxy Amines into 3-Hydroxypyrrolidines Catalyzed by La(OTf)3

Highly regioselective intramolecular aminolysis of 3,4-epoxy amines has been achieved. Key features of this reaction are (1) chemoselective activation of epoxides in the presence of unprotected aliphatic amines in the same molecules by a La(OTf)₃ catalyst and (2) excellent regioselectivity for anti-Baldwin 5-endo-tet cyclization. This reaction affords 3-hydroxy-2-alkylpyrrolidines stereospecifically in high yields. DFT calculations revealed that the regioselectivity might be attributed to distortion energies of epoxy amine substrates. The use of this reaction was demonstrated by the first enantioselective synthesis of an antispasmodic agent prifinium bromide.