Diagrammes de phases des systemes binaires KNO3-CsNO3 et KNO3-NaNO3

(K?Na)NO₃ and (K?Cs)NO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The first phase diagram shows a minimum freezing equimolar mixture at 494 K, a continuous solid solution in equilibrum with liquid phase and an eutectic mixture (88 molar % of KNO₃) at 380 K. The second one exhibits an invariant at 400 K corresponding to the KNO₃ solid-solid transition, an eutectoid mixture at 10 molar % of KNO₃ and 418 K involving the CsNO₃ solid-solid transition and an eutectic mixture at 60 molar % of KNO₃ and 495 K.     

Synthesis and Upconversion Luminescence in LaF3:Yb3+, Ho3+, GdF3: Yb3+, Tm3+ and YF3:Yb3+, Er3+ obtained from Sulfide Precursors

Rare earth fluorides are mainly obtained from aqueous solutions of oxygen‐containing precursors. Probably, this method is simple and efficient, however, oxygen may partially be retained in the fluoride structure. We offer an alternative method: obtaining fluorides and solid solutions based on them from an oxygen‐free precursor. As starting materials, we choose sulfides of rare‐earth elements and solid solutions based on them. The fluorination is carried out by exposure to hydrofluoric acid of various concentrations. The transmission electron microscopy images revealed the different morphologies of the products, which depend on the concentration of the fluorinating component (HF) and the host element. The solid solution particle size varied from 30–35 nm in the case of GdF₃:Yb³⁺, Tm³⁺ (4 % HF) to larger structures with dimensions exceeding 200 nm, such as that for LaF₃:Yb³⁺, Ho³⁺ (40 % HF). The thermal characteristics, such as the temperatures of the transitions and melting and enthalpies, were determined for the solid solutions and simple fluorides. Applicability of the materials obtained as biological luminescent markers was tested on the example of upconversion luminescence, and good upconversion properties were detected.     

ChemInform Abstract: Theoretical Study of Structural and Vibrational Properties of Al3N3, Ga3N3, and In3N3.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Synthesis and Biological Activity of α-Methylene-γ-butyrolactones

α-Methylene-γ-butyrolactones [dihydro-3-methylene-2(3H)furanones] constitute an important group of natural products and possess wide-ranging biological activities. Progress in the synthesis of the heterocycle and the classification of the synthetic methods are not only of practical interest, but also fundamentally important as a current example for the construction of an unusual 1,4-functionality distance and an α-substituted acrylic ester moiety which is susceptible to nucleophilic attack.     

Die Systeme Tl3SbS3-Tl3AsS3 und TlSbS2-TlAsS2

The influence of structural relationships between the components of (pseudo)binary systems with no intermediate compounds on the type of phase diagram was investigated. Structurally and chemically closely related Tl₃SbS₃ and Tl₃AsS₃ form a complete solid solution series whereas crystallographically different TlSbS₂ and TlAsS₂ constitute an eutectic type system.

     

K3SbSe3, Rb3SbSe3 und Cs3SbSe3 – Synthese und Kristallstruktur

K₃SbSe₃, Rb₃SbSe₃, and Cs₃SbSe₃ – Synthesis and Crystal Structure The compounds K₃SbSe₃, Rb₃SbSe₃ and Cs₃SbSe₃ were synthesized by heating mixtures of Sb₂O₃ and an alkalicarbonate in a stream of hydrogen saturated by selenium in a temperature range between 750 °C and 800 °C. The compounds crystallize isostructural with Na₃AsS₃. A comparison of atomic distances and bond angles with those of the isostructural arsenic and bismuth compounds shows the effect of lone pairs.     

KMgF3:Ce3+,Tb3+纳米粒子中Ce3+→Tb3+的发光及能量传递

利用微乳液方法,合成了铈、铽共掺杂的氟镁钾纳米粒子,研究了体系中Ce3+→Tb3+的发光特性以及它们之间的相互作用,结果表明KMgF3:Ce3+Tb3+纳米粒子中存在Ce3+→Tb3+的能量传递过程,即Ce3+可以将吸收的能量直接传递给Tb3+离子,使得Tb3+的绿色发光强度大为增加.     

Comparison of proton conduction in KTaO3 and SrZrO3

In the present paper, the authors focus on proton conduction pathways in a cubic perovskite KTaO(3) and an orthorhombic perovskite SrZrO(3). Density functional theory with a generalized gradient approximation is used to find proton binding sites. The nudged elastic band method is used to find transition states between minima. With this potential energy map of binding and transition states, adjacency matrices and their analogs identify four types of conduction paths in KTaO(3). Distortions from these paths are seen in SrZrO(3). In both cases, the lowest energy path has an intraoctahedral transfer rate-limiting barrier. A Fourier analysis of the OH stretch in ab initio molecular dynamics simulations revealed a strongly redshifted OH stretch in SrZrO(3) relative to KTaO(3). Hence, an orthorhombic system with a lowest energy conduction path limited by an intraoctahedral barrier can exhibit a redshifted OH stretch.     

Tandem epoxysilane rearrangement/Wittig-type reactions using γ-phosphinoyl- and γ-phosphonio-α,β-epoxysilane

Reaction of γ-phosphinoyl- and γ-phosphonio-α,β-epoxysilane with a base followed by addition of a ketone or an aldehyde afforded dienol silyl ether derivatives via a tandem process that involves base-induced ring opening of the epoxide, Brook rearrangement, and Wittig-type reaction.     

Syntheses of 3-Deoxy-3-Fluoroglucosamine Derivatives

ABSTRACT

Methyl

2-acetamido-4,6-di-0-acetyl-2,3-dideoxy-3-fluoro-α-D-glucopyranoside (5) and methyl 2-diallylamino-2,3,6-trideoxy-3,6-difluoro-4-0-methanesulfonyl-α-D-glucopyranoside (10) were prepared from methyl 4,6-0-benzylidene-α-D-glucopyranoside. Fluorination at C-3 was carried out by ring opening of an aziridinium ion. Two fluorinating reagents were used depending on the starting material.     

Low-temperature heat capacity studies on DyFe3, DyCo3, DyNi3, and LaNi3

Low-temperature heat capacity measurements were made on DyFe₃, DyCo₃, DyNi₃, and LaNi₃ over the temperature range 1.4–15°K. Two anomalies, observed at 1.8 and 9.3°K, are ascribed to the presence of an oxide and a hydride. Another anomaly exists at 3.2°K, which may be due to hydroxide. The observed electronic specific heat coefficients are interpreted in terms of the band structure of these materials.     

3-Azidodifluoromethyl-3H-diazirin-3-yl group as an all-in-one functional group for radioisotope-free photoaffinity labeling

The 3-azidodifluoromethyl-3H-diazirin-3-yl group was designed and synthesized as an all-in-one functional group for radioisotope-free photoaffinity labeling.     

Schwingungsspektren und Kraftkonstanten der Übergangsreihen OP(OCH3)3?OPCl3 und SP(OCH3)3?SPCl3

The IR- and RAMAN -spectra are reported from OP(OCH₃)₂Cl, OP(OCH₃)Cl₂, SP(OCH₃)Cl, SP(OCH₃)Cl₂. The assignement to the fundamental vibration is given and all Valence-force-constants are calculated. With increasing number of chlorine atoms decrease f P? OCH₃ and f P? Cl. In the contrary, f O? P and f S? P increase. Here the influence of decreasing electro negativity is compensated by the change from an element of the first period of eight elements to an element of the second period.     

Phosphine-catalyzed annulations of azomethine imines: allene-dependent [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] pathways

In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways-the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol--the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates--suggest that it might find extensive applications in heterocycle synthesis.     

Dimethylarsenazid (CH3)2AsN3, Dimethylwismutazid (CH3)2BiN3 und Dimethylthalliumzid (CH3)2TiN3

The reaction of (CH₃)₂AsJ and AgN₃ yields (CH₃)₂AsN₃; a colourless liquid (b. p. 136°C) which dissolves as a monomeric in benzene. (CH₃)₂BiN₃ is precipitated in form of colourless needles (dec. temp. 150°C) from an etherical solution of Bi(CH₃)₃ and HN₃. According to its vibrational and mass spectra the molecules are not associated although the (CH₃)₂BiN₃ is not soluble; dipole association of this polar molecules is assumed for the crystal structure. (CH₃)₂TlN₃ can be obtained from TI(CH₃)₃ and ClN₃ as well as from (CH₃)₂TlOH and HN₃ in form of colourless needles and leaves (dec. temp. 245°C). According to its vibrational spectra it has an ionic structure, (CH₃? Tl? CH₃)⁺N^?₃.     

Ammonia-free synthesis of 3-trifluoromethyl-3-phenyldiaziridine

An ammonia-free synthesis of 3-trifluoromethyl-3-phenyldiaziridine, an important intermediate in the synthesis of a widely used photolabel 3-trifluoromethyl-3-phenyldiazirine, is described. By avoiding the use of volatile, corrosive, and toxic anhydrous ammonia, the major hazard involved in the synthesis of this widely used photolabel is eliminated. Furthermore, this synthesis is convenient compared to the conventional route, since it is significantly less time consuming and, due to the absence of liquid ammonia, this method does not require the maintenance of low temperature for prolonged periods.     

Michael condensation of 3-arylidene-3H-pyrrol-2-ones and 3-arylidene-3H-furan-2-ones with cyclohexanone

The Michael condensation in the series of 5-aryl-3-arylidene-3H-pyrrol-2-ones and 5-aryl-3-arylidene-3H-furan-2-ones, containing an activated C=C bond, with cyclohexanone was investigated. It was shown that the condensation products were 1,5-dicarbonyl compounds containing a heterocyclic fragment. The enolization of one of the oxo groups, leading to the formation of hydroxypyrrole or hydroxyfuran structures, was demonstrated by the spectral data. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 823–827, June, 2007.     

The structure and magnetic properties of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2

A new μ₃-O triiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NO₃)(CH₃OH)₂ (HOBZ = benzoic acid) has been synthesized, its structure has been determined and variable temperature magnetic susceptility has also been measured. In the molecule, three iron atoms formed an equilateral triangle with μ₃-O in center. The fitting to the magnetic susceptibility showed that an intramolecular antiferromagnetic exchange interaction occurred between iron atoms with J=-25.51 cm^?1, and a weaker intermolecular autiferromagnetic exchange interaction occurred with zJ' = ?2.30 cm^?1.     

3, 3, 3-Trifluoropropyl(methyl)cyclosiloxanes

The catalytic rearrangement of the cyclopentasiloxanes Φ_mD_5-m, where Φ represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously [1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from Φ_mD_5-m and from Φ_mD_4-m (m=0–4) [1] is inversely proportional to the molar fraction of Φ links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes Φ_mD_n (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes Φ_mD_5-m. It has been established that at equilibrium a mixture of cyclosiloxanes Φ_mD_n containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes Φ_mD_5-m are less active in the process of rearrangement than the cyclotetrasiloxanes Φ_mD_4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D₄?ΦD₃ ≈ Φ₂D₃<Φ₃D₂<Φ₄D < Φ₂D₂ < Φ₃D.     

Two‐Step Synthesis of Multifunctional γ‐Lactams from γ‐Lactone

We present herein an efficient and rapid method for the synthesis of N,1‐dialkyl‐4‐(2‐hydroxyethyl)‐5‐oxopyrrolidine‐3‐carboxamides based on the conversion of γ‐lactone to γ‐lactam via the conjugate addition of primary amines to an ethyl α‐functionalized acrylate followed by intramolecular cyclization.