Synthesis and oxidative polycondensation of 4, 4−diethynylbiphenyl

Summary 4,4-Diethynylbiphenyl was synthesized. By polycondensing it an oligomer with alternating biphenyl (-4,4) and diacetylene chains was obtained.     

Effect of EDTA on the diffusion behavior of 99TcO4 − and ReO4 − in GMZ bentonite

Polyaminopolycarboxylate EDTA with powerful metal-binding property, which often presents in low and intermediate-level waste, can enhance the radionuclide migration. The effect of EDTA on the diffusion behavior of ⁹⁹TcO₄ ^? and ReO₄ ^? in Gaomiaozi (GMZ) bentonite was investigated by using through-diffusion method. For ⁹⁹TcO₄ ^? in present of EDTA, the D _e values was (1.2 ± 0.1) × 10^?11 m²/s, which was 4 times higher than that in absent of EDTA. It can be explained that the complexation between ⁹⁹TcO₄ ^? and EDTA might be formed. By contrast, the D _e values of ReO₄ ^? remained unchanged in present or absent of EDTA, indicating that ReO₄ ^? could not complex with EDTA. However, the diffusion of ReO₄ ^? could be increased in present of EDTA, the D _a value was found to be increased from 1.8 × 10^?10 to 5.4 × 10^?10 m²/s. It demonstrated that ReO₄ ^? need more drastic conditions to form the Re(VII)–EDTA complexes than those used for ⁹⁹TcO₄ ^?. For both ReO₄ ^? and ⁹⁹TcO₄ ^?, the rock capacity factor α is less than the total porosity ε _tot, indicating that they has little retention/sorption on the surface of bentonite.     

A vibrational analysis of the MnO 4 − bands

Teltow'S [14,15] measurements of the permanganate bands are reanalyzed using the level scheme of Ballhausen and Liehr [2]. For KMnO ₄ dissolved in KClO ₄ the components of the first ¹ T ₂ state are found at 18050 cm^–1 18078 cm^–1 and 18043 cm^–1. The breathing frequency of the MnO _– ⁴ unit is in this state 768 ^–1. The electronic origin of the second ¹ T ₂ state is found at 30723 cm^–1 with a breathing frequency of 760 cm^–1.Evidence is further found for a ¹ T ₁ state with its split components located at 14446 cm^–1, 14526 cm^–1 and 14600 cm^–1. The breathing frequency is here found to be 800 cm^–1.Finally for KMnO ₄ dissolved in NaClO ₄ there are indications that one or two spin-triplets are located near 13200 cm^–1.

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Zusammenfassung TeltowS Messungen des Permanganatspektrums [14, 15] werden mit Hilfe des Termschemas von Ballhausen und Liehr [2] von neuem analysiert. Für KMn ₄ in KClO ₄ findet man die zum ersten ¹ T ₂-Zustand gehörenden Komponenten bei 18050, 18078 und 18043 cm^–1. Die Valenzschwingung des MnO _– ⁴ liegt hier bei 768 cm^–1. Der Ursprung des zweiten ¹ T ₂-Systems wird bei 30723 cm^–1 gefunden, die dazugehörige Valenzfrequenz ist 760 cm^–1.Bei 14446, 14526 und 14600 cm^–1 liegen offenbar die Komponenten eines ¹ T ₁-Terms, wozu eine Valenzfrequenz von 800 cm^–1 gehört.Schließlich findet man für KMnO ₄ in NaClO ₄ Anzeichen für ein oder zwei Spin-Tripletts um 13200 cm^–1.

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Résumé Les bandes d'absorption du permanganate, mesurées par Teltow [14,15], sont réanalysées à l'aide d'un système de termes proposé par Ballhausen et Liehr [2]. Pour KMnO ₄ dans KClO ₄, on trouve les composants du premier état ¹ T ₁ à 18050, 18078 et 18043 cm^–1. La vibration symétrique du MnO _– ⁴ dans cet état se situe à 768 cm^–1. L'origine électronique du second état ¹ T ₂ est trouvé à 30723 cm^–1, la fréquence oscillatrice correspondante est de 760 cm^–1.Un état ¹ T ₁ avec ses composants à 14446, 14526 et 14600 cm^–1 est mis en évidence, avec une vibration symétrique de 800 cm^–1.Finalement, au cas du KMnO ₄ dissous dans le NaClO ₄, il y a des indications pour un ou deux triplets de spin vers 13200 cm^–1.

     

The thermodynamic stability of the LaBr 4 − ion

The thermodynamic stability of the LaBr ₄ ^? anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction $ LaBr_4^ - = Br^ - + LaBr_3 The thermodynamic stability of the LaBr₄⁻ anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction were Δ_r H°(298.15 K) = 302 ± 14 and 303 kJ/mol, respectively. The value Δ_f H° (LaBr₄⁻, g, 298.15 K) = −1105 ± 14 kJ/mol was recommended as the enthalpy of formation of the LaBr₄⁻ anion. Original Russian Text ? M.F. Butman, L.S. Kudin, V.B. Motalov, D.A. Ivanov, V.V. Sliznev, K.W. Kr?mer, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 5, pp. 885–890.     

The conformational changes of 5SrRNA from lupin seeds in presence of ClO 4 − , NO 3 − , Br−, BF 4 − , SO 4 2− , Cl−, COO− anions by adiabatic scanning calorimetry

The results of calorimetric studies of 5SrRNA solutions isolated from lupin seeds in the pressence of the ClO ₄ ^? , NO ₃ ^? , Br ₄ ^? , SO ₄ ^2? , Cl^?, COO^? (maleic and fumaric acids) anions were reported. The plots of calorimetric curves, enthalpy of conformational changes of two state transitions were presented. Using the deconvolution method proposed by Freire and Biltonen the elementary transitions were distinguished and discussed.     

Structural and thermal characterization of Zn2−xCoxTiO4

In this work, spinels with the general formula Zn_2?xCo_xTiO₄ were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn₂TiO₄ after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination was favored.     

Solid State Chemistry of A4B3−Molecules

Abstract

The system P₄S₃?P₄Se₃?As₄S₃?As₄Se₃ was investigated by thermal and X-ray methods. Five regions of solid solubility with different crystal structures were found. All transform at higher temperatures into the plastically-crystalline state with β-P₄S₃?structure.

The substituted species P_4-nAs_nS_mSe_3-m (n = 0–4, m = 0–3) are formed in molten mixtures of A₄B₃?molecules (FIGURE 1). They were identified by HPLC and mass-spectrometric measurements.

After long equilibration times P₄Se₃, As₄S₃ and As₄Se₃ decompose peritectoidally into the resp. A₄B₄?species and an amorphous product.     

Pyrolysis Mass Spectrometry Analysis of BF4 − Doped Polythiophene

Abstract

Pyrolysis of electrochemically prepared BF₄ ^? doped polythiophene (PTh) by direct insertion probe and Currie point pyrolysis gas chromatography mass spectrometry techniques indicated that thermal decomposition of PTh occurs in two steps. In accordance with literature results, the first step is assigned to the loss of the dopant, and the second step to the degradation of the polymer backbone producing segments of various conjugation lengths. At elevated temperatures, detection of products such as H₂S and C₂H₂ indicating cleavage of the thiophene (Th) ring was associated with a network structure. For the dedoped samples, a significant increase in the relative intensities of the peaks characteristic to the counter ion of the dopant, N(C₄H₉)₄ ⁺ pointed out the inward diffusion of (C₄H₉)₄N⁺ during the dedoping process.     

Potentiometric investigation of NaSO 4 − ion pair formation in NaClO4 medium

The ion pair formation of NaSO ₄ ⁻ has been investigated potentiometrically in 1M NaClO ₄ medium at 25°C using two different sodium-selective indicator electrodes and a perchlorate reference electrode. The stability constant of NaSO ₄ ⁻ obtained in this study was . Although is small, it lowers the free sulfate concentration drastically in 1M NaClO ₄ medium and is a factor which should be considered in the use of NaClO ₄ as inert supporting electrolyte.     

Thermochemical investigations of the systems KCl−KBr−H2O,K2SO4−(NH4)2SO4−H2O and KNO3−NH4NO3−H2O at 298.15 K

For the equilibrium solid phases occurring in the systems: KCl?KBr?H₂O, K₂SO₄?(NH₄)₂SO₄?H₂O and KNO₃?NH₄NO₃?H₂O, the concentration dependencies of differential solution enthalpies, Δ_sol H ₂ for several crystallization paths, were measured. The limiting differential solution enthalpies, Δ_sol H ₂ ⁰ , were determined by extrapolation of the above dependencies to the ionic strength,I _m ⁰ , corresponding to the appropriate binary solutions. For KCl?KBr?H₂O system only, the clear dependence between Δ_sol H ₂ ⁰ andI _m ⁰ values was found and discussed.     

Synthesis and properties of BaCe1−xYxO3−δ–BaWO4 composite protonic conductors

Barium cerate doped by trivalent rare earth metal ions is a potentially huge component of materials for electrochemical industry due to its high protonic conductivity. However, the poor chemical stability especially in the presence of CO₂, SO₂ or H₂O, resulting in decreasing the mechanical durability of obtained materials, limits their possible applications. The new approach towards stable ceramic protonic conductors with high electrical conductivity is presented. Thermal stability of yttrium doped (10 mol%) of BaCeO₃ was enhanced by forming the composite material BaCe_0.9Y_0.1O₃–BaWO₄ (10 mol% of BaWO₄). The synthesis was performed by solid-state reaction method. The detailed study of thermal decomposition of starting powders mixture was performed using thermogravimetry and differential thermal analysis (TG/DTA) techniques combined with Evolved Gas Analysis (EGA—mass spectrometry). Structure, phase composition and microstructure together with thermal stability of sintered materials were determined. The exposition tests were performed to characterise the stability of composites in carbon dioxide and water vapour-rich atmospheres. The samples were exposed to atmosphere containing CO₂/H₂O (7 % of CO₂ in air, 100 % RH) at temperature of 25 °C for 300 h. Thermal analysis supplied with mass spectrometry was applied to analyse the materials after the test. The results of this experiment showed better chemical resistance of composite material—BaCe_0.9Y_0.1O₃ with 10 mol% of BaWO₄ compared to single phase material.     

Excitation and luminescence spectra of UO2F2−4

The luminescence and excitation spectra of [(CH₃)₄]₂UO₂F₄, M₃UO₂F₅ (M = K and Rb) and Cs₂SnCl₆:UO₂Cl²⁻₄ have been recorded at temperatures down to 10 K. The excitation spectrum of [(CH₃)₄]₂UO₂F₄ is unique because the electronic origin is located at the lowest energy reported for any uranyl compound. The analysis of the excitation spectrum is consistent with a D_4h, but not a D_5h coordinated uranyl chromophore. A detailed interpretation of the vibronic structure of the spectrum enables the lower excited states of the uranyl ion to be located, and the symmetries of these are consistent with the model of Denning. A comparison with the excitation spectra of salts of the UO₂F³⁻₅ anion is made.     

Kinetic and thermal studies of removal of CrO 4 2− ions by ettringite

Ettringite was prepared in the presence of various dosages of CrO ₄ ^2? ions at three different temperatures. X-ray diffraction (XRD) and differential scanning calorimetery (DSC) results showed shift in the peaks characterized to ettringite as the result of formation of Cr-substituted ettringite. Substitution of SO ₄ ^2? by CrO ₄ ^2? ions in ettringite crystal resulted in delay in the rate of its formation, as well as reduction in the crystal diameters. However, the crystal diameters and rate of formation of both ettringite and Cr-substituted ettringite were increased by increasing temperature of preparation, and this was confirmed by scanning electron microscope (SEM) micrographs. The thermodynamic parameters: the enthalpy, entropy, and Gibbs free energy changes for substitution process were studied. It is concluded that the removal of chromate ions by ettringite is an endothermic spontaneous process. The positive value of ΔS° suggests increasing in randomness during the removal process.     

Structure of the Mo(CN)8 4− ion

Summary The question of the hybridization of the atomic orbitals of Mo in the Mo(CN)₈ ^4– ion is examined, and it is shown that the dodecahedral structure can exist without the participation off electrons.     

F− Preference of Polyamide Cryptand to Cl−

The variations in geometry structure, IR spectra, as well as the molecular orbitals upon anion recognition for polyamide cryptand are explored with the hybrid density functional theory. The cavity generated by six amide NH groups shrinks upon F ^? recognition because of the strong hydrogen bonds between the amide protons and F ^? , while the cavity expands upon Cl ^? binding because of the strong electron repulsion between the p electron of Cl ^? and the lone pair electrons of the nitrogen atom of the pyridine moieties. The “electropositive field space” …Cl ^? coupling exists when Cl ^? is recognized. The strong anion binding energy with F ^? indicates that the polyamide cryptand prefers F ^? to Cl ^? .     

Single-crystal X-ray diffraction study of α-quartz-type Al1−xGaxPO4

Single crystals in the AlPO₄GaPO₄ system prepared by hydrothermal methods were investigated by electron microprobe analysis and X-ray diffraction. The fine details of the crystal structures, and, in particular, the intertetrahedral bridging angle and the tetrahedral tilt angle, were found to vary in an essentially linear manner with gallium content. The piezoelectric properties of α-quartz homeotypes are known to be correlated to these angles. The present results thus open the possibility to tune the piezoelectric properties of these materials by varying the chemical composition.     

Development of sterically hindered SPOs and enantioselective Ni−Al bimetallic catalyzed C−H cyclization of 4-oxoquinazolines with tethered alkenes

The Ni−Al bimetallic catalysis of intramolecular enantioselective and regioselective C−H cyclization of 4-oxoquinazolines with tethered alkenes has been successfully developed. Some new secondary phosphine oxides (SPOs) with large steric hindrance (SPO6-11) were designed and successfully synthesized from readily available chiral amines or amino acids. The developed chiral SPOs as ligands or preligands demonstrate much higher efficiency in the asymmetric catalytic reactions than the reported traditional ones. A new class of chiral tricyclic pyrroloquinazolinones were obtained in up to 95% yield and 99% ee.     

Chromatography of Anions on Alumina Thin Layers: Effect of Transition Metals on CI−-Br−-I− and No− 2-NO− 3 Separations

Abstract

Chromatographic behaviour of eighteen anions on thin layers of alumina and alumina mixed with silica gel (1:1, 1:2 and 2:1) has been studied using mixed acidic organic solvent systems containing formic acid. Though the addition of silica gel to alumina enhances the mobility and clarity of detection of anions, but it causes the increased tailing for Fe(CN)^3- ₆, Cr0₄ ^2- and Cr₂O₄ ^2-. Formic acid is responsible for the differential migration of anions. All the anions remained at the starting line (R_F = 0) in pure organic solvents. Formic acid-Ketone systems gave better results compared to formic acid-alcohol systems. Development time increases with the increase of viscosity/mol. wt. of organic solvents. The mutual separation of C1, Br^?, Br^?, I^? and NO^? ₂ and NO^? ₃ were achieved on pure alumina using formic acid-acetone solvent systems. The effect of transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) on C1^?-Br^?-I^? and NO^? ₂-NO^? ₃ separations has been studied.     

Spin-adduct of the P4 ·− radical anion during the electrochemical reduction of white phosphorus

The radical anion P₄·⁻ was detected and identified by the ESR method as a spin-adduct with nitrone during the electrochemical reduction of white phosphorus in the presence of a spin trap, viz., α-phenyl-N-tert-butylnitrone, in a special electrolysis cell with a helical platinum working electrode in the potentiostatic mode. The character of the behavior of P₄·⁻ and the spin trap during electrochemical reduction was monitored by cyclic voltammetry directly in the electrolysis cell, and the spin-adduct formed was detected by ESR.