One-step synthesis of pentavalent triphenylantimony derivatives Ph3Sb(OSiR3)2, Ph3Sb(OCH2CH2)2NH and Ph3Sb(OCH2CH2NMe2)2: X-ray molecular structure of Ph3Sb(OSiMe3)2

Pentavalent bis(triorganosiloxy)triphenylantimony derivatives, Ph₃Sb(OSiR₃)₂ (R = Me, Ph), were synthesized by reaction of triphenylantimony with trimethyl- or triphenylsilanol in the presence of tert-butylhydroperoxide by the mild reaction conditions (0-5 °C, 2 h). The reaction of triphenylantimony with diethanolamine in the presence of tert-butylhydroperoxide gave the cyclic compound Ph₃Sb(OCH₂CH₂)₂NH. The mixture of Ph₃SbO and Ph₃Sb(OCH₂CH₂NMe₂)₂ was obtained by the reaction of triphenylantimony with 2-(N,N-dimethylamino)ethanol in the presence of tert-butylhydroperoxide.     

Theoretical Evidence of Aromaticity in X3 − (X = B, Al, Ga) Species

We investigated the electronic structure and chemical bonding of the B₃ ^–, Al₃ ^–, and Ga₃ ^– anions, and the gas phase NaB₃, NaAl₃, and NaGa₃ molecules. We found that the ground state of the neutral gas phase salts contains an equilateral triangular anion interacting with a Na⁺ cation. The B₃ ^–, Al₃ ^–, and Ga₃ ^– anions possess two delocalized electrons and are found to be aromatic. The triangular anions have been shown to be related to recently synthesized organometallic compound containing an aromatic -Ga₃ ^2– unit, but they are differ from them by four valence electrons. The reason for earlier appearance of the -orbital in the B₃ ^–, Al₃ ^–, and Ga₃ ^– anions is discussed.     

Collision-induced dissociation study of cyclization of α-diazo-ω-arylsulphonylaminoalkan-2-ones

The collision-induced dissociation mass-analysed ion kinetic energy (CID MIKE) spectra (electron impact and chemical ionization) of five α-diazo-ω-arylsulphonylaminoalkan-2-ones and corresponding N-arylsulphonylazetidin-3-ones and N-arylsulphonylpyrrolidin-3-ones were studied. The [M ? N₂]⁺˙ and [MH ? N₂]⁺ ions of two types of the diazo ketones provide CID MIKE spectra similar to those of the corresponding M⁺˙ and MH⁺ of the heterocyclic compounds, i.e. a cyclization analogous to that in solution takes place. For the other three types of diazo compounds the Wolff rearrangement prevails in both the gas and liquid phases. The effect of the substituents on the cyclization process was studied. The data obtained permit the results of acid-catalysed cyclization of similar diazo ketones to be predicted on the basis of their CID MIKE spectra. Chemical ionization provides a closer similarity with reactions in solution than electron impact ionization, which can be rationalized by the protonation of the diazo ketone molecule being the driving force of the cyclization reaction either in solution or in the ion source of a mass spectrometer.     

Mixed conductivity and Mössbauer spectra of (La0.5Sr0.5)1−xFe1−yAlyO3−δ (x=0-0.05, y=0-0.30)

Aluminum incorporation in the rhombohedrally distorted perovskite lattice of (La_0.5Sr_0.5)_1−xFe_1−yAl_yO_3−δ (x=0-0.05, y=0-0.30) decreases the unit cell volume and partial ionic and p-type electronic conductivities, while the oxygen nonstoichiometry and thermal expansion at 900-1200 K increase on doping. The creation of A-site cation vacancies has an opposite effect on the transport properties of Al-substituted ceramics. The maximum A-site deficiency tolerated by the (La,Sr)(Fe,Al)O_3−δ structure is however limited, close to 3-4%. The Mössbauer spectroscopy revealed progressive localization of electron holes and a mixed charge-compensation mechanism, which results in higher average oxidation state of iron when Al³⁺ concentration increases. The average thermal expansion coefficients of (La_0.5Sr_0.5)_1−xFe_1−yAl_yO_3−δ are (12.2-13.0)×10⁻⁶ K⁻¹ at 300-900 K and (20.1-30.0)×10⁻⁶ K⁻¹ at 900-1200 K in air. The steady-state oxygen permeability (OP) of dense Al-containing membranes is determined mainly by the bulk ionic conductivity. The ion transference numbers at 973-1223 K in air, calculated from the oxygen permeation and faradaic efficiency (FE) data, vary in the range 1×10⁻⁴-3×10⁻³, increasing with temperature.     

Four 3‐cyano­difur­aza­nyl ethers: potential propellants

In earlier papers, we described the synthesis and structures of bis(3‐nitro­fur­azan‐4‐yl) ether, C₄N₆O₇, (I), bis­[3‐(nitro‐N,N,O‐azoxy)­fur­azan‐4‐yl] ether, C₄N₁₀O₉, (II), and bis[3‐­(5H‐[1,2,3]­triazolo­[4,5‐c]­fur­azan‐5‐yl)­fur­azan‐4‐yl] ether, C₈N₁₄O₅, (III). Here we compare the structures of (I)–(III) with those of four 3‐cyano­difur­aza­nyl ethers, namely bis(3‐­cyano­fur­azan‐4‐yl) ether, C₆N₆O₃, (IV), 3‐cyano­fur­aza­nyl 3‐­nitro­fur­aza­nyl ether, C₅N₆O₅, (V), 3,4‐bis(3‐cyano­fur­azan‐4‐­yl­oxy)­fur­azan, C₈N₈O₅, (VI), and bis­[3‐(3‐cyano­fur­azan‐4‐­yl­oxy)­fur­azan‐4‐yl]­diazene, C₁₀N₁₂O₆, (VII). It was found that the geometric parameters of the difur­aza­nyl ether fragments are similar in these structures and therefore not influenced by substituent effects; however, the conformation of this fragment is different, viz. structures (I), (III), (V) and (VI) have approximate C₂ symmetry, and structures (II), (IV) and (VII) have C_s symmetry. Dense crystal packing (1.626–1.898 Mg m⁻³) is characteristic for all these hydrogen‐free compounds. A linear correlation is also determined between crystal density and `molecular density' (M/V), where M is the mass of a mol­ecule and V is the molecular volume.     

Viscoelastoplasticity of Rubbery Polymers at Finite Strains

Constitutive relations are derived for the nonlinear response of rubbery polymers and polymeric melts at isothermal loading. The model is based on a concept of nonaffine temporary networks, where breakage and reformation of active chains are responsible for the viscoelastic behavior, whereas gliding of junctions with respect to a bulk medium reflects the plastic effects. Constitutive equations are developed using the laws of thermodynamics. They contain only one extra adjustable parameter compared to the Lodge formula in finite viscoelasticity. The model is applied to study stresses and residual strains in a bar at uniaxial extension and in a layer at simple shear. Fair agreement is demonstrated between experimental data for polystyrene and polyethylene at elevated temperature and the results of numerical simulation.Sommario. Vengono derivate equazioni costitutive che descrivono la risposta nonlineare di gomme polimeriche e fusioni di polimeri nel caso di carichi isotermi. Il modello proposto è basato sul concetto di reti temporanee non affini, in cui la rottura e la riformazione di legami attivi sono responsabili del comportamento viscoielastico, mentre lo scorrimento di giunzioni rispetto alla matrice del materiale è veicolo di effetti plastici. Le equazioni costitutive vengono sviluppate usando le leggi della termodinamica. Esse contengono solo un parametro regolabile aggiuntivo rispetto alla formula di Lodge in viscoelasticità finita. Il modello è applicato allo studio degli sforzi e delle deformazioni residue in una barra in allungamento uniassiale ed in uno strato soggetto a semplice scorrimento. Si dimostra un discreto accordo tra i dati sperimentali per il polistirene ed il polietilene ad elevate temperature e i risultati di simulazioni numeriche.     

Quantum chemical investigation of new model bent-shaped bis-azomethines for nonlinear optics applications

Abstract

Quantum-chemical calculations of the E,E-, E,Z- and Z,Z-isomers structure of model bis-azomethines by the semiempirical PM3 method and the time-dependent theory of the density functional (DFT) are performed. It is shown that a completely satisfactory agreement between the theory and experiment is achieved using the B3LYP/cc-pVDZ calculation level and the INDO/S method for calculating the absorption spectra of the new bis-azomethines. The values of polarizability, first and second hyperpolarizability of model compounds are calculated. The used approach allows to make the screening of the most promising bis-azomethines for nonlinear optics applications.     

Formation of the imidazolinone ring under mild conditions in the presence of sodium hydride

Substituted imidazolinones containing heterocyclic carboxylic acids as substituents and possessing herbicidal properties were synthesized by cyclization of 2-amino-2,3-dimethylbutyramide with heterocyclic ethyl dicarboxylates under mild conditions. The use of NaH as base leads to a significant increase in the reaction rate and allows the preparation of the target compounds in high yields.     

Design and Synthesis of a New Family of Fluorinated Liquid Crystals

A convenient and simple three‐step pathway to the new family of CF₂CF₂S‐bridged alkanes and CF₂S‐, CF₂O‐bridged alkenes and alkynes was elaborated by using catalytic olefination reaction as a key step of the synthetic sequence. The obtained compounds revealed attractive liquid crystalline characteristics.