Al2O3/K2O-containing non-stoichiometric lithium disilicate-based glasses

The crystallisation kinetics of experimental glasses in 3 different systems: (A) Li₂O–SiO₂, (B) Li₂O–Al₂O₃–SiO₂ and (C) Li₂O–K₂O–Al₂O₃–SiO₂ were studied under non-isothermal conditions. The DTA results revealed a stronger tendency to crystallisation of binary compositions in comparison to the ternary and quaternary compositions comprising Al₂O₃ and K₂O which present the lower crystallisation, i.e. the crystallisation propensity follows the trend A > B > C. The devitrification process in the Li₂O–SiO₂ and Li₂O–Al₂O₃–SiO₂ systems began earlier and the rate was higher in comparison to that of glasses in the quaternary Li₂O–K₂O–Al₂O₃–SiO₂ system. Thus, addition of Al₂O₃ and K₂O to glasses of Li₂O–SiO₂ system was demonstrated to promote glass stability against crystallisation. However, the activation energy for crystallisation was shown to depend also on the SiO₂/Li₂O ratio with the binary system showing a decreasing trend with increasing SiO₂/Li₂O ratio, while the opposite tendency was being observed for compositions with added Al₂O₃ and K₂O.     

Redox and oxo-abstraction Reactions of Silylamine with MoOCl4

Trimethylsilyldiethylamine Me₃SiNEt₂ and MoOCl₄ (1:1) undergo a free radical redox reaction in CH₂Cl₂ or Et₂O to form MoCl₃O(HNEt₂). Reduction occurs even in aprotic media like CCl₄ and CS₂ to give Mo^V complexes Mo₂Cl₆O₂(N₂Et₄) and Mo₂Cl₆O₂[(SCNEt₂)₂S₂], respectively. A 2:1 reaction in nonionizing protic solvents undergoes redox cum cleavage to provide MoCl₂O(NEt₂) (HNEt₂) but a reaction at reflux temperature in 1,2-dichloroethane leads to diethylammonium salt, [Et₂NH₂][MoCl₄O(HNEt₂)]. Higher molar reactions (3:1, 4:1) in CH₂Cl₂ or Et₂O are associated with redox reaction as well as oxygen atom abstraction to form de-oxo Mo^IV complex MoCl₃(NEt₂)(HNEt₂)₂, whereas, a 3:1 reaction in CS₂ forms Mo₂Cl₄O(S₂CNEt₂)₄. Compounds have been characterized by elemental analyses, redox titration, magnetic moment, conductance, infrared, electronic absorption and ¹H-NMR measurements.     

Hydrolysis and Oxidation Products of the Chemical Warfare Agents 1,2-Bis[(2-chloroethyl)thio]ethane Q and 2,2′-Bis(2-chloroethylthio)diethyl Ether T

Syntheses of diols of structure [HOCH₂CH₂S]₂(CH₂)_n in 86–95% yield from the sodium salt of 2-mercaptoethanol and Br(CH₂)_nBr (n = 1 to 5) or in 60–90% yield from 2-chloroethanol and NaS(CH₂)_nSNa (n = 2 to 5) are described. The diol [HOCH₂CH₂SCH₂CH₂]₂O was prepared in 82% yield from the sodium salt of 2-mercaptoethanol and [ClCH₂CH₂]₂O, and in 88% yield from 2-chloroethanol and [HSCH₂CH₂]₂O. Mono- and bis-sulfoxides and bis-sulfones of these species were prepared in generally high yield by treatment with an equivalent of KIO₄ in aqueous methanol, two equivalents of NaIO₄ in aqueous methanol, or four equivalents of H₂O₂ in trifluoroacetic acid respectively. The compounds are important analytical standards for investigating the fate of the chemical warfare agents sesquimustard Q and oxygen mustard T in environmental samples.     

Photoluminescence emission behavior on the reduced band gap of Fe doping in CeO2-SiO2 nanocomposite and photophysical properties

Fe/CeO₂-SiO₂ nanocomposite was synthesized via hydrothermal method. Bond length of nanocomposite was determined through FTIR analysis, while Raman analysis showed lattice relaxation of CeO₂ phase in Fe/CeO₂-SiO₂. TEM, XRD and DLS-PSA revealed an increase in size of Fe/CeO₂-SiO₂ as compared to CeO₂-SiO₂ which was attributed to have more oxygen vacancies in CeO₂ after doping of iron. Lattice contraction was also observed in some phases of CeO₂ in Fe/CeO₂-SiO₂ nanocomposite as compared to CeO₂-SiO₂ nanocomposite. This contraction was used for determination of Fe content incorporated in CeO₂ [1 1 1] phase. The band gap values of Fe/CeO₂-SiO₂ nanocomposite were found reduced after doping of Fe by factors of 0.62 and 0.55 eV, respectively. Photoluminescence study of the materials was carried out to study the different type of transitions occurring after absorption of electromagnetic radiation. Photoluminescence intensity at 2.12 eV was found enhanced after doping of Fe due to increased oxygen vacancy. Photocatalytic activity of the nanocomposites was studied with the degradation of chlorpyrifos pesticide.     

Untersuchungen zur Mischkristallbildung im System SrI2?BaI2 bei Normaldruck und bei 2,0 GPa

Investigations of the Solid Solution in the System SrI₂? BaI₂ at Ambient Pressures and at 2.0 GPa The P, T, x-diagram of the system SrI₂? BaI₂ has been investigated at ambient pressures and at 2.0 GPa. The amount of solid solution in the four structure types occuring in this system (SrI₂- or PbCl₂? ZrAs₂-type with SrI₂ and PbCl₂- or anti-Fe₂P-type with BaI₂) differs considerably. Structural geometries belonging to the same PbCl₂ structure family show marked differences in their toleration to cation substitution. Solid solution is especially pronounced in the BaI₂-rich phases which incorporate up to 60 mol-% Sr²⁺ in the high pressure phase of BaI₂.     

Hydrogen Peroxide Formation by Electric Discharge with Fine Bubbles

Pulsed discharge plasma is typical oxidation technology for disposing organic compounds in aqueous solutions. When this electrical discharge plasma was applied in water, it may produce hydrogen peroxide (H₂O₂) without any catalyst or chemical agent. In order to increase H₂O₂ production by electrical discharge plasma in water, fine bubbles were introduced into the electrical discharge plasma in this experiment. Bipolar pulsed voltages were applied to cylindrical electrodes in the water while Ar or O₂ bubbles were introduced, generating a pulsed discharge plasma. The introduction of the bubbles seemed to enhance the dissociation of water molecules and increased H₂O₂ formation, especially with O₂ bubbling. Dissolved oxygen in the water contributed to H₂O₂ formation by pulsed discharge plasma with the bubbles, while dissociation of water molecules was the cause of H₂O₂ formation by pulsed discharge plasma without bubbles. More H₂O₂ was formed by pulsed discharge plasma with O₂ bubbles, because the amount of dissolved oxygen in the water increased upon bubbling with O₂.     

Water Reduction and Dihydrogen Addition in Aqueous Conditions With ansa-Phosphinoborane

Ortho-phenylene-bridged phosphinoborane (2,6-Cl₂Ph)₂B-C₆H₄-PCy₂ 1 was synthesized in three steps from commercially available starting materials. 1 reacts with H₂ or H₂O under mild conditions to form corresponding zwitterionic phosphonium borates 1-H₂ or 1-H₂O . NMR studies revealed both reactions to be remarkably reversible. Thus, when exposed to H₂, 1-H₂O partially converts to 1-H₂ even in the presence of multiple equivalents of water in the solution. The addition of parahydrogen to 1 leads to nuclear spin hyperpolarization both in dry and hydrous solvents, confirming the dissociation of 1-H₂O to free 1 . These observations were supported by computational studies indicating that the formation of 1-H₂ and 1-H₂O from 1 are thermodynamically favored. Unexpectedly, 1-H₂O can release molecular hydrogen to form phosphine oxide 1-O . Kinetic, mechanistic, and computational (DFT) studies were used to elucidate the unique “umpolung” water reduction mechanism.     

Alternativ-Liganden. XXV. Neue Chelatliganden des Typs Me2ESiMe2(CH2)2E′Me2 (E=P,As; E′=N,P, As)

Alternative Ligands. XXV. New Chelating Ligands of the Type Me₂ESiMe₂(CH₂)₂E′Me₂ (E=P, As; E′=N, P, As) Chelating ligands of the type Me₂EsiMe₂(CH₂)₂E′ Me₂, have been prepared by the following routes: Starting from Me₂Si(Vi)Cl, the compounds with E=N and E′ =N ( 1 ), P ( 2 ), As ( 3 ) are obtained in yields of 65 to 78% by aminolysis to yield Me₂NSiMe₂Vi, followed by the LiE′ Me₂ catalyzed addition of He′Me₂ to the vinyl group. The intermediates ClSiMe₂(CH₂)E′Me₂ [E′=N ( 4 ), P ( 5 ), As ( 6 )] are produced by the reactions of 1 to 3 with PhPCl₂. 5 and 6 can be prepared in a purer form by the photochemical addition of HPMe₂ and HAsMe₂, respectively, to the vinyl group of Me₂Si(Vo)Cl. 4 to 6 react with LiEMe₂, in situ prepared from n-BuLi and HEMe₂, to yield the ligands Me₂ESiMe₂(CH₂)₂E′Me₂ ( 7–12 ) (E=P, As; E′=N, P, As). The new compounds have been characterized by analytical and spectroscopic investigations (NMR, MS).     

FLAVIN SENSITIZED PHOTOOXIDATION OF (POLY)AMINO ACIDS: FATE OF THE PHOTOSUBSTRATE

Abstract— With respect to literature data, which seemed to be contradictory, we examined the fate of ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) in flavin-sensitized photooxidation reactions by quantitation of all possible products, i.e. CO₂ by acidimetric titration, CH₂O by colometry and glyoxylate enzymatically; N-methyl groups were quantified by ₁H-NMR. Nitrilotriacetate yields 100% oxidative photodecarboxylation with CH₂O formation, while EDTA behaves quite differently, yielding quantitative amounts of CO₂ and glyoxylate, but no CH₂O. The electron balance in this reaction is found to be maintained by co-formation of one equivalent >N-CH₃. From these data it is concluded that the photooxidation of the structural element >NCH₂C0₂ containing a tertiary nitrogen atom, occurs by electron transfer, followed by decarboxylation. The neutral radical that is formed is reductant and will give off an electron equivalent to yield the easily hydrolysed structural element >N⁺= CH₂. With EDTA, containing the fragment –O₂CCH₂ >NCH₂CH₂N< CH₂CO₂–, the electron transfer towards flavin is strongly favoured by stabilisation of a cisoid mesomeric radical cation (₀₂cch₂ >₊ NCH₂CH₂N_CH2CO2 o₂cch₂ >NCH₂CH₂N_+CH2CO2), which, after loss of CO₂ undergoes internal 1,6-hydrogen shift to yield the more stable radical: _CH2>CH₂CH₂N CH₂CO₂CH₂lt NCH₂CH₂N_HCO2. The latter radical will easily be oxidized to the iminium ion >N_*= CH-C0_2-. which in turn hydrolyses to glyoxylate. Chelation of EDTA by metal cations prevents the 1,6-hydrogen shift, and leads to the product pattern obtained in the NTA photoreaction.     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.     

Synthesis and Structures of some Lithium and Sodium (Aminoalcoholato)hydrido Aluminates

LiAlH₄ and NaAlH₄ were allowed to react in a 1 : 1, 1 : 2 and 1 : 3 ratio with 2-dimethylaminoethanol, 1-dimethylamino-2-propanol, and (–)-N-methylephedrine. Reactions in the 1 : 1 ratio leads to mixtures of M(AlH_4–n(OR′NMe₂)_n) in thf solution showing a temperature dependent composition. From the solutions obtained in a 1 : 2 or 1 : 3 ratio the following compounds were isolated as single crystals: (thf)NaAlH₂ · (OCH₂–CH₂NMe₂)₂ ( 2 ), LiAlH₂(OCHMe–CH₂NMe₂)₂ ( 3 ), LiAlH₂(OCHPh–CHMe–NMe₂)₂ ( 4 ), LiAlH(OCH₂CH₂NMe₂)₃ ( 5 ), NaAlH(OCH₂CH₂NMe₂)₃ ( 6 ). All compounds are dimers in the solid state and their Al atoms are pentacoordinated. M–H–Al bridges were found only in the dihydridoaluminate  2 .     

New water-soluble (hydroxymethyl)triphosphine [(HOCH2)2PCH2CH2]2PCH2OH, a derived PdII(triphosphine) complex, and triphosphine trioxide

An aqueous solution of (hydroxymethyl)triphosphine [(HOCH₂)₂P(CH₂)₂]₂PCH₂OH (II) was synthesized in situ by treatment of the triphosphine H₂P(CH₂)₂PH(CH₂)₂PH₂ with formaldehyde. Addition of a CH₂Cl₂ solution of trans-PdCl₂(PhCN)₂ to an in situ aqueous solution of II resulted in the formation of a species thought to be [PdCl{[(HOCH₂)₂P(CH₂)₂]₂PCH₂OH}]⁺Cl⁻. Attempts to isolate the complex were unsuccessful because of conversion to material containing small amounts of phosphine oxide(s) formed via a redox reaction involving water. The triphosphine trioxide [(HOCH₂)₂P(O)(CH₂)₂]₂P(O)CH₂OH was readily isolated from an in situ solution of II by treatment with aqueous H₂O₂.     

Untersuchungen zur Existenz ternärer Amalgame der Alkalimetalle: Die Systeme KHg2?RbHg2 und NaHg2?CsHg2

Studies on the Existence of Ternary Amalgams of Alkali Metals: The Systems KHg₂-RbHg₂ and NaHg₂-CsHg₂ . The ternary systems KHg₂? RbHg₂ and NaHg₂? CsHg₂ are investigated by thermal analyses and X-ray methods. Both systems are quasibinary: Lattice constants and cell volumes of samples in the system KHg₂? RbHg₂ are in accordance with Vegards law (continous formation of mixed crystals). No ternary compound was detected in this system. NaHg₂? CsHg₂ however shows a peritectic decomposition at 300°C, which can be associated to the new ternary compound Na₂CsHg₆, crystallizing in the hexagonal system (a = 5.080(1) Å; c = 11.632(3) Å). Due to pronounced disorder the crystal structure of Na₂CsHg₆ cannot be determined in full details. In principal it corresponds to an ordered variant of the NaHg₂ structure (modified AlB₂ type) with a triple c-axis.     

富氧条件下乙炔选择催化还原NOx

Acetylene as a reducing agent of metal exchanged HY catalysts, for selective catalytic reduction of NO in the reaction system of 0.16% NO, 0 （C2H2-SCR） was investigated over a series 08% C2H2, and 9.95% O2 （volume percent） in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 ℃. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2-SCR of NO. The protons in zeolite were crucial to the C2H2-SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2-SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO.     

Ruthenium-Assisted Tellurium Abstraction in Bis(thiophen-2-yl) Ditelluride

The reaction of [RuCl₂(CO)₃]₂ and Te₂Tpn₂ (Tpn=thiophen-2-yl, C₄H₃S) in the absence of light resulted in the formation of cct-[RuCl₂(CO)₂(TeTpn₂)₂] ( 1 ) [cis(Cl)-cis(CO)-trans(TeTpn₂)] and TeTpn₂ ( 2 ) together with the precipitation of tellurium. The complex 1 and the monotelluride 2 were characterized by NMR spectroscopy and single-crystal X-ray diffraction. The decomposition of Te₂Tpn₂ to TeTpn₂ has been monitored by ¹²⁵Te NMR spectroscopy and seemed to be faster than the ligand substitution in [RuCl₂(CO)₃]₂ by TeTpn₂. A catalytic cycle is proposed for the decomposition of Te₂Tpn₂ to TeTpn₂ based on the PBE0-D3/def2-TZVP calculations.     

Transient Spark Discharge Generated in Various N2/O2 Gas Mixtures: Reactive Species in the Gas and Water and Their Antibacterial Effects

Reactive species generated in the gas and in water by cold air plasma of the transient spark discharge in various N₂/O₂ gas mixtures (including pure N₂ and pure O₂) have been examined. The discharge was operated without/with circulated water driven down the inclined grounded electrode. Without water, NO and NO₂ are typically produced with maximum concentrations at 50% O₂. N₂O was also present for low O₂ contents (up to 20%), while O₃ was generated only in pure O₂. With water, gaseous NO and NO₂ concentrations were lower, N₂O was completely suppressed and HNO₂ increased; and O₃ was lowered in O₂ gas. All species production decreased with the gas flow rate increasing from 0.5 to 2.2 L/min. Liquid phase species (H₂O₂, NO₂￣, NO₃￣, ^·OH) were detected in plasma treated water. H₂O₂ reached the highest concentrations in pure N₂ and O₂. On the other hand, nitrites NO₂￣ and nitrates NO₃￣ peaked between 20 and 80% O₂ and were associated with pH reduction. The concentrations of all species increased with the plasma treatment time. Aqueous ^·OH radicals were analyzed by terephthalic acid fluorescence and their concentration correlated with H₂O₂. The antibacterial efficacy of the transient spark on bacteria in water increased with water treatment time and was found the strongest in the air-like mixture thanks to the peroxynitrite formation. Yet, significant antibacterial effects were found even in pure N₂ and in pure O₂ most likely due to high ^·OH radical concentrations. Controlling the N₂/O₂ ratio in the gas mixture, gas flow rate, and water treatment time enables tuning the antibacterial efficacy.

     

Sulfur evolution from coal combustion in O2/CO2 mixture

O₂/CO₂ coal combustion technology is considered as one of the most promising technologies for CO₂ sequestration due to its economical advantages and technical feasibility. It is significant to study the sulfur transfer behavior of coal in O₂/CO₂ atmosphere for organizing combustion properly and controlling SO₂ emission effectively. To clarify the effect of atmosphere on the sulfur transfer behavior, thermogravimetry coupled with Fourier Transform Infrared (TG-FTIR) system was employed to study the formation behavior of sulfur-containing gas species from Xuzhou bituminous coal pyrolysis in CO₂ atmosphere compared with that in N₂ atmosphere. Also the SO₂ formation behaviors during Xuzhou bituminous coal combustion in O₂/N₂ and O₂/CO₂ atmospheres were investigated. Results show that COS is preferentially formed during the coal pyrolysis process in CO₂ atmosphere rather than in N₂ atmosphere. When temperature is above 1000 K, sulfate in the CO₂ atmosphere begins to decompose due to the reduction effect of CO, which comes from the CO₂ gasification. During coal combustion process, replacing N₂ with CO₂ enhances the SO₂ releasing rate. SO₂ emission increases first and then decreases as O₂ fraction increases in the O₂/CO₂ mixture. XPS result of the ash after combustion indicates that higher O₂ concentration elevates the sulfur retention ability of the mineral matter in the coal.     

Dinuclear Cobalt(III) Complexes Showing a Co2O2 Metallacycle

The heptadentate Schiff base H₃L reacts with cobalt(II) acetate in methanol to form the discrete dinuclear complex Co₂L(OAc)₂(OMe)(H₂O)₂ ( 1 ·2H₂O). The reaction of 1 ·2H₂O with NMe₄OH·5H₂O in methanol gives rise to displacement of the acetate by methanolate groups, yielding Co₂L(OMe)₃(H₂O) ( 2 ·1H₂O). Recrystallizations of the Schiff base, 1 ·2H₂O and 2 ·H₂O in different solvents, produce single crystals of H₃L, 1 ·2.5H₂O and 2 ·2MeOH, respectively. The crystal structures of 1 ·2.5H₂O and 2 ·2MeOH show the cobalt atoms double bridged by and endogenous phenol oxygen atom and an exogenous methanolate oxygen donor, giving rise to Co₂O₂ cores with Co···Co distances of ca. 2.87 Å.     

Die Kristallstruktur von W2CoB2 und isotypen Phasen

Zusammenfassung Die Phasen Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ und W₂NiB₂ kristallisieren in einem neuen Typ (W₂CoB₂-Struktur). Die Zelle ist orthorhombisch, die Raumgruppe D _2h ²⁵ -I mmm. Die Punktlagen sind 4 W in 4 f), 2 Co in 2 a) und 4 B in 4 h). Die strukturellen Bauelemente werden mit jenen von Mo₂FeB₂ (U₃Si₂-Typ) verglichen.

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The ternary compounds Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ and W₂NiB₂ crystallize with a new type (W₂CoB₂-structure). The elementary cell is orthorhombic, the space group being D _2h ²⁵ -I mmmm. The atomic positions are determined to be 4 W in 4 f), 2 Co in 2 a) and 4 B in 4 h). Both crystal structures W₂CoB₂ and Mo₂FeB₂ (U₃Si₂-type) are compared with respect to the trigonal prismatic surrounding of the boron atoms.

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Mit 1 Abbildung     

Studies on lanthanoid sulphites: V. thermal decomposition of cerium and neodymium sulphites

The preparation and thermal behaviour of Ce₂(SO₃)₃· 3H₂O, Nd₂(SO₃)₃·6H₂O and Nd₂(SO₃)₃ have been studied. Cerium sulphite undergoes first dehydration which is followed by decomposition to CeO₂ in the temperature range 500 – 850 °C. The decomposition involves two intermediate phases both in air and nitrogen. According to the TG curves the phases in air are Ce₂(SO₃)₂SO₄ and Ce₂SO₃(SO₄)₂. In nitrogen, Ce₂O₂SO₄ was identified and this provides a synthetic route to cerium oxysulphate.Neodymium sulphite decomposes to Nd₂O₂SO₄ when heated in air or in nitrogen up to 950°C. The intermediate levels observed do not correspond to single phases, and the reaction mechanism depends strongly on the experimental conditions.