Synthesis of nonequilibrium Ir<Subscript>x</Subscript>Re<Subscript>1-x</Subscript> solid solutions. Crystal structure of [Ir(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl]<Subscript>2</Subscript>[ReCl<Subscript>6</Subscript>]Cl<Subscript>2</Subscript>

Synthesis of five binary complex salts with an [Ir(NH₃)₅Cl]²⁺ complex cation is described. The counterions are [ReCl₆]^2–, [IrCl₆]^2–, [ReBr₆]^2–, and Cl^–. A polycrystal X-ray diffraction study has been performed for [Ir(NH₃)₅Cl]₂[ReCl₆]Cl₂, and its crystal structure has been determined. A series of Ir _x Re_1–x phases (0.5 x > 1) were obtained by reductive thermolysis. For the Ir-Re system, the history of the V/Z(x) dependence has been refined.Original Russian Text Copyright © 2004 by S. A. Gromilov, S. V. Korenev, I. V. Korolkov, K. V. Yusenko, and I. A. BaidinaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 508–515, May–June 2004.     

Counterion and solvent effects on the dilute solution viscosity of polystyrene ionomers

We present an analysis of data on the intrinsic viscosity [η] of sulfo-polystyrene ionomers in several solvents for a variety of sulfonation levels and counterions. For solvents of low dielectric constant, 2 < ε < 18, [η] decreases from the base polymer value [η]₀ with increasing substitution level. This behavior was attributed to intramolecular association of ionic dipoles. The ratio [η]/[η]₀ was found to depend on a single reduced variable α_Aα_Sx, where x is the fractional substitution, α_A depends only on the counterion, and α_S ∝ ε^?1 depends only on the solvent. For solvents of high dielectric constant, 36 < ε < 47, [η] increases approximately as x³, and counterion effects are small. This behavior was attributed to ionic dissociation, giving rise to a polyelectrolyte effect. Implications of the low ε results are discussed in relation to association-induced gelation behavior and possible generalizations of the reduced variables approach.     

Hexamethylphosphorsäuretriamid als Ligand, 2. Mitt.: Umsetzungen von [Co(HMPT)4]2+ mit Chlorid-, Bromid- und Jodidionen

Zusammenfassung Folgende Koordinationsformen entstehen aus [Co(HMPT)₄]²⁺ bei Zusatz von Halogenidionen in Hexamethylphosphorsäuretriamid (HMPT): [Co(HMPT)₃Cl]⁺, [Co(HMPT)₂Cl₂], [Co(HMPT)Cl₃]^–, [CoCl₄]^2–, [Co(HMPT)₃Br]⁺, [Co(HMPT)₂Br₂] und [Co(HMPT)₃J]⁺.

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Hexamethylphosphoric triamide as a ligand II: Reactions of Co(HMPT)₄ ²⁺ with chloride, bromide, and iodide ions

The following coordination species are formed from [Co(HMPT)₄]²⁺, by addition of halide ions in hexamethylphosphoric triamide (HMPT): [Co(HMPT)₃Cl]⁺, [Co(HMPT)₂Cl₂], [Co(HMPT)Cl₃]^–, [CoCl₄]^2–, [Co(HMPT)₃Br]⁺, [Co(HMPT)₂Br₂] and [Co(HMPT)₃J]⁺.

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V. Gutmann, A. Weisz undW. Kerber, 1. Mitt., Mh. Chem.100, 2096 (1969).     

Electron-impact fragmentation of aliphatic polynitro compounds

The mass spectra of two series of aliphatic polynitro compounds are reported and discussed. The fragmentation patterns of aliphatic nitro and polynitro compounds are similar in that no appreciable molecular ion current is observed; however, there are several other features in the fragmentation of aliphatic polynitro compounds which differ from that of nitroalkane spectra. Both series of compounds studied-C(NO₂)_x(CH₃)_4?x, where x = 4 to 0 and C₂(NO₂)_x(CH₃)_6?x, where x = 6,4,2-show a decrease in the number and intensity of alkylions with an increase in the NO⁺ and NO₂⁺ ion current as x increases. The main ions resulting from the more nitrated compounds are [NO]⁺, [NO₂]⁺, [CO₂]^+. and [CH₃CO]⁺, whose noncharged counterparts are the principal species produced in the detonation of these compounds. This similarity of the products of the two processes suggests the use of mass spectroscopy for the investigation of the initial explosive processes. The principal fragmentation pathways of the polynitroalkanes have been elucidated by exact mass measurements and the observation of metastable ion transitions.     

Structure of complex bromides crystallizing in MBr<Subscript>2</Subscript>-NEt<Subscript>4</Subscript>Br-H<Subscript>2</Subscript>O systems (M = Cd,Cu, Co) at 25°C

The crystalline structures of four tetraethylammonium salts, [Et₄N]CdBrP₃, [Et₄N]Cd₂Br₅, [Et₄N]₂CoBr₄, and [Et₄N]₂CuBr₄ were determined by X-ray analysis of their single crystals. The CdBr _x ^{2 − x} anions in the examined salts are linked to polymeric chains, and the coordination number of cadmium ion is 5 or 6. The d-metal ion in the copper and cobalt complexes has tetrahedral configuration, and the corresponding anions are discrete.     

Farbe und Konstitution bei anorganischen Feststoffen, 14. Mitt.: Die Lichtabsorption des zweiwertigen Kupfers in oxidischen Wirtsgittern

Zusammenfassung Um die Beziehungen zwischen der Lichtabsorption des zweiwertigen Kupfers nach isomorphem Einbau in ein oxidisches Wirtsgitter und dessen Konstitution aufzufinden, wurde Cu²⁺ in oktaedrischer (Cu _x Mg _1–x TiO₃, Cu _x Cd _1–x TiO₃, Cu _x Mg _1–x CaSiO₄, Cu _x Mg _1–x CaGeO₄, Cu _x Mg _2–x SiO₄, Cu _x Mg _2–x GeO₄) und tetraedrischer Koordination (Cu _x Zn_2–x SiO₄, Cu _x Mg _1–x Cr₂O₄) spektralphotometrisch untersucht. Die Farbkurven besitzen mindestens 2 Absorptionsbanden (Kristallfeldbanden) im längerwelligen und eine oft gut ausgeprägte Elektronenübergangsbande (charge transfer) im kürzerwelligen Spektralbereich. In einigen Fällen ist noch eine zweite Elektronenübergangsbande als Schulter zu erkennen. Es wurden auch Cu-haltige 2,3- und 2,4-Spinelle spektralphotometrisch untersucht (Cu _x Mg _1–x Al₂O₄, Cu _x Mg _1–x Ga₂O₄, Cu _x Cd _y Zn _1–x–y Al₂O₄, Cu _x Mg _2–x SnO₄, Cu _x Mg _2–x TiO₄, Cu _x Zn _1–x MgTiO₄, Cu _x Mg _1–x Cd _y TiO₄). Es zeigte sich, daß Cu²⁺ immer auf Tetraeder- und Oktaederlücken verteilt ist. Eine Aufweitung des Wirtsgitters durch isomorphen Einbau größerer Kationen bewirkt nicht immer eine IR-Verschiebung der Banden, sondern in einigen Fällen (Spinellphasen) auch eine UV-Verschiebung. Eine Sonderstellung nimmt das ägyptisch-Blau CuCaSi₄O₁₀ ein, da hier das Cu²⁺ von 4 O_2– in planarer Anordnung umgeben ist. Die Farbkurve weist 3 Maxima auf im Einklang mit der Kristallfeldtheorie.

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In order to find out relations between the lightabsorption of bivalent copper isomorphously incorporated into an oxidic host lattice and the constitution of this lattice, the spectrum of Cu²⁺ has been investigated in octahedral (Cu _x Mg_1–x TiO₃, Cu _x Cd _1–x TiO₃, Cu _x Mg _1–x CaSiO₄, Cu _x Mg _1–x CaGeO₄, Cu _x Mg _2–x SiO₄, Cu _x Mg _2–x GeO₄) and tetrahedral coordination (Cu _x Zn _2–x SiO₄, Cu _x Mg _1–x Cr₂O₄). The colour curves show at least 2 absorption bands within the region of longer wave length and a charge transfer band often well developed in the range of shorter wavelength. In some cases also a second charge transfer band becomes conspicuous as a shoulder. Copper containing 2,3- and 2,4-spinels have been also investigated (Cu _x Mg _1–x Al₂O₄, Cu _x Mg _1–x Ga₂O₄, Cu _x Cd _y Zn _1–x–y Al₂O₄, Cu _x Mg _2–x SnO₄, Cu _x Mg _2–x TiO₄, Cu _x Zn _1–x MgTiO₄, Cu _x Mg _1–x Cd _y Zn _1–y TiO₄). From the colour curve one can infer that Cu²⁺ occupies in the spinels always tetrahedral as well as octahedral interstices. A widening of the lattice does not effect always a shifting of the absorption bands towards IR but in some cases (spinel phases) also the inverse shifting will occur. An exceptional case represents the egyptian blue CuCaSi₄O₁₀ since in this lattice the Cu₂₊ are surrounded by four O^2– in a coplanar arrangement. The colour curve shows three absorption bands in agreement with the crystal field theory.

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Mit 20 Abbildungen     

Ruthenium(III) – catalyzed oxidative cleavage of <Emphasis Type="Italic">p</Emphasis>-aminoazobenzene by chloramine-B in alkaline medium and uncatalyzed reaction in acid medium: spectrophotometric kinetic and mechanistic study

p-Aminoazobenzene (PAAB) is one of the important monoazo dyes and its oxidation kinetic study is of much use in understanding the mechanistic profile of PAAB in redox reactions. Consequently, the kinetics of oxidation of PAAB by sodium N-chlorobenzenesulfonamide or chloramine-B (CAB) in HClO₄ medium and in NaOH medium catalyzed by ruthenium(III) chloride (Ru^III) have been investigated at 298 K. U.v.–vis spectrophotometry was used as a basic analytical approach in this study. Under an identical set of experimental conditions, the reactions of PAAB–CAB in HClO₄ medium were facile, but the reactions became too slow to be studied in alkaline medium and hence ruthenium(III) chloride has been used as a catalyst in alkaline medium. The stoichiometry (1:2) and oxidation products (nitrosobenzene and p-nitrosoaniline) are the same in both media, but the kinetic and mechanistic patterns were found to be different. The experimental rate laws obtained are: − d[CAB]/dt = k [CAB]₀ [PAAB]₀ [H⁺] in acid medium and − d[CAB]₀/dt = k [CAB]₀ [PAAB]₀[OH⁻] ^x [Ru^III] ^y in alkaline medium, where x and y are less than unity. The reaction was examined with reference to changes in (a) concentration of benzenesulfonamide, (b) concentration of added neutral salts, (c) ionic strength, (d) dielectric permitivity and (e) solvent isotope effect. The reaction was also studied at different temperatures and the overall activation parameters have been evaluated. The oxidation reaction fails to induce the polymerization of added acrylonitrile. C₆H₄SO₂NHCl and C₆H₄SO₂NCl⁻ have been postulated as the reactive oxidizing species in acidic and alkaline media, respectively. It was found that the reactions are nearly 20 times faster in acid medium in comparison with alkaline medium. It was also observed that ruthenium(III) was an efficient catalyst for the facile oxidation of PAAB by CAB in alkaline medium by making the reaction go twelve-fold faster than the uncatalyzed reactions. The catalytic constant (K _C) has been calculated at different temperatures and the values of activation parameters with respect to ruthenium(III) have also been evaluated in alkaline medium. The observed results have been explained by plausible mechanisms and the relative rate laws have been deduced.     

Thermal Activation of CH4 and H2 as Mediated by the Ruthenium Oxide Cluster Ions [RuOx]+ (x=1–3): On the Influence of Oxidation States

Thermal gas-phase reactions of the ruthenium-oxide clusters [RuO_x]⁺ (x=1–3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]⁺/CH₄ couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO₂]⁺ brings about the generations of [Ru,O,C,H₂]⁺/H₂O, [Ru,O,C]⁺/H₂/H₂O, and [Ru,O,H₂]⁺/CH₂O, whereas [RuO₃]⁺ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H₂). Regarding the reactions with H₂, as compared to CH₄, both [RuO]⁺ and [RuO₂]⁺ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO₃]⁺ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H−H bond activation. Furthermore, the reactivity patterns of [RuO_x]⁺ (x=1–3) with CH₄ and H₂ have been compared with the previously reported results of Group 8 analogues [OsO_x]⁺/CH₄/H₂ (x=1–3) and the [FeO]⁺/H₂ system. The electronic origins for their distinctly different reaction behaviors have been addressed.     

Synthesis,spectroscopic, thermal and biological aspects of drug‐based copper(II) complexes

A series of novel complexes of the type Cu(II)(L_n)₂(H₂O)₂]^•xH₂O [where L_n = L _1–4 , these ligands being described as: L ₁ , 2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)phenol, x = 1; L ₂ , 2‐({4‐[6,7‐dihydrothieno[3,2‐c] pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)‐5‐(methoxy)phenol, x = 2; L ₃ , 5‐chloro‐2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)phenol, x = 2; and L ₄ , 5‐bromo‐4‐chloro‐2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino} methyl)phenol, x = 1] was investigated. They were characterized by elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR and electronic spectra, magnetic measurements and thermal studies. The FAB‐mass spectrum of [Cu(II)( L ₁ )₂(H₂O)₂]^•H₂O was determined. A magnetic moment and reflectance spectral study revealed that an octahedral geometry could be assigned to all the prepared complexes. Ligands (L_n) and their metal complexes were screened for their in vitro antibacterial activity against Bacillus subtillis, Pseudomonas aeruginosa, Escherichia coli and Serratia marcescens bacterial strains. Kinetic parameters such as order of reaction (n), the energy of activation (E_a), the pre‐exponential factor (A), the activation entropy (ΔS^≠), the activation enthalpy (ΔH^≠) and the free energy of activation (ΔG^≠) are reported. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetics and reactivities of ruthenium(III)- and osmium(VIII)-catalyzed oxidation of ornidazole with chloramine-T in acid and alkaline media: A mechanistic approach

Ornidazole is an antiparasitic drug having a wide spectrum of activity. Literature survey has revealed that no attention has been paid towards the oxidation of ornidazole with any oxidant from the kinetic and mechanistic view point. Also no one has examined the role of platinum group metal ions as catalysts in the oxidation of this drug. Such studies are of much use in understanding the mechanistic profile of ornidazole in redox reactions and provide an insight into the interaction of metal ions with the substrate in biological systems. For these reasons, the Ru(III)- and Os(VIII)-catalyzed kinetics of oxidation of ornidazole with chloramine-T have been studied in HCl and NaOH media, respectively at 313 K. The oxidation products and kinetic patterns were found to be different in acid and alkaline media. Under comparable experimental conditions, in Ru(III)-catalyzed oxidation the rate law is −d[CAT]/dt = k [CAT]_o[ornidazole]_o^x[H⁺]^−y[Ru(III)]^z and it takes the form −d[CAT]/dt = k [CAT]_o[ornidazole]_o^x[OH⁻]^y[Os(VIII)][ArSO₂NH₂]^−z for Os(VIII)-catalyzed reaction, where x, y and z are less than unity. In acid medium, 1-chloro-3-(2-methyl-5-nitroimidazole-1-yl)propan-2-one and in alkaline medium, 1-hydroxy-3-(2-methyl-5-nitroimidazole-1-yl)propan-2-one were characterized as the oxidation products of ornidazole by GC–MS analysis. The reactions were studied at different temperatures and the overall activation parameters have been computed. The solvent isotope effect was studied using D₂O. Under identical set of experimental conditions, the kinetics of Ru(III) catalyzed oxidation of ornidazole by CAT in acid medium have been compared with uncatalyzed reactions. The relative rates revealed that the catalyzed reactions are about 5-fold faster whereas in Os(VIII) catalyzed reactions, it is around 9 times. The catalytic constant (K_C) has been calculated for both the catalysts at different temperatures and activation parameters with respect to each catalyst have been evaluated. The observed experimental results have been explained by plausible mechanisms. Related rate laws have been worked out.     

Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Collisional activation study of cyclic polysulfides

Cyclic polysulfides isolated from higher plants, model compounds and their electron impact induced fragment ions have been investigated by various mass spectrometric methods. These species represent three sets of sulfur compounds: C₃H₆S_x (x=1?6), C₂H₄S_x (x=1?5) and CH₂S_x (x=1?4). Three general fragmentation mechanisms are discussed using metastable transitions: (1) the unimolecular loss of structural parts (CH₂S, CH₂ and S_x); (2) fragmentations which involve ring opening reactions, hydrogen migrations and recyclizations of the product ions ([M? CH₃]⁺, [M? CH₃S]⁺, [M? SH]⁺ and [M? CS₂]^+˙); and (3) complete rearrangements preceding the fragmentations ([M? S₂H]⁺ and [M? C₂H₄]^+˙). The cyclic structures of [M]^+˙ and of specific fragment ions have been investigated by comparing the collisional activation spectra of model ions. On the basis of these results the cyclic ions decompose via linear intermediates and then recyclizations of the product ions occur. The stabilities of the fragment ions have been determined by electron efficiency vs electron energy curves.     

Solid Solution Formation between Vanadium(V) and ­Tungs­ten(V) Oxide Phosphate

The solid solutions (V_1–xW_x)OPO₄ with β‐VOPO₄ structure type (0.0 ≤ x ≤ 0.01) and α_II‐VOPO₄ structure type (0.04 ≤ x ≤ 0.26) were obtained from mixtures of V^VOPO₄ and W^VOPO₄ by conventional solid state reactions and by solution combustion synthesis. Single crystals of up to 3 mm edge length were obtained by chemical vapor transport (CVT) (800 → 700 °C, Cl₂ as a transporting agent). Single crystal structure refinements of crystals at x = 0.10 [a = 6.0503(2) Å, c = 4.3618(4) Å, R₁ = 0.021, wR₂ = 0.058, 21 parameters, 344 independent reflections] and x = 0.26 [a = 6.0979(2) Å, c = 4.2995(1) Å, R₁ = 0.030, wR₂ = 0.081, 21 parameters, 346 independent reflections] confirm the α_II‐VOPO₄ structure type (P4/n, Z = 2) with mixed occupancy V/W for the metal site. Due to the specific redox behavior of W⁵⁺ and V⁵⁺, solid solutions (V_1–xW_x)OPO₄ should be formulated as (V^IV_xV^V_1–2xW^VI_x)OPO₄. The valence states of vanadium and tungsten are confirmed by XPS measurements. V⁴⁺ with d¹ configuration was identified by EPR spectroscopy and magnetic measurements. Electronic spectra of the solid solutions show the IVCT(V⁴⁺ → V⁵⁺) and the LMCT(O^2– → V⁵⁺). (V_0.74W_0.26)OPO₄ powders exhibit semi‐conducting behavior (E_g = 0.7 eV).     

Oxidation of metronidazole with sodium N‐bromo‐p‐toluenesulfonamide in acid and alkaline media: A kinetic and mechanistic study

A kinetic study of oxidation of metronidazole (Met) with sodium N‐bromo‐p‐toluenesulfonamide or bromamine‐T (BAT) has been carried out in HClO₄ (30°C) and NaOH (40°C) media. The experimental rate laws obtained are –d[BAT]/dt=k[BAT][Met]^x [H⁺]^y in acid medium and –d[BAT]/dt=k[BAT][Met]^x [OH^?]^y/[PTS]^z in alkaline medium, where x, y, and z are less than unity and PTS is p‐toluenesulfonamide. The reaction was subjected to changes in (a) ionic strength, (b) concentration of added reduction product PTS, (c) concentration of added neutral salts, (d) dielectric permittivity, and (e) solvent isotope effect. In both media, the stoichiometry of the reaction was found to be 1:1, and the oxidation product of metronidazole was identified as its aldehyde. The reaction was studied at different temperatures, and the activation parameters have been evaluated. The reaction constants involved in the proposed schemes were deduced. The reaction was found to be faster in acid medium in comparison with alkaline medium, which is attributed to the involvement of different oxidizing species. Mechanisms proposed and the rate laws derived are consistent with the observed kinetics. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 700–709, 2005     

Bromokomplexe von Co(II) und Ni(II) in Acetonitril,Propandiol-1,2-carbonat und Trimethylphosphat

Zusammenfassung Die Bildung von Bromokomplexen von Co(II) und Ni(II) wird in Acetonitril (AN), Propandiol-1,2-carbonat (PDC) und Trimethylphosphat (TMP) auf spektrophotometrischem, potentiometrischem und konduktometrischem Wege untersucht. Folgende Koordinationsformen dürften vorliegen: [CoBr]⁺ (oktaedrisch inAN undTMP), CoBr₂ (tetraedrisch inAN, oktaedrisch inTMP), [CoBr₃]^– (tetraedrisch inAN, oktaedrisch inTMP), [CoBr₄]^2– (tetraedrisch inAN undPDC, oktaedrisch inTMP), [NiBr]⁺ (oktaedrisch inAN), NiBr₂ (tetraedrisch inAN, oktaedrisch inTMP), [NiBr₃]^– (tetraedrisch inAN), [NiBr₄]^2– (tetraedrisch inAN undPDC, oktaedrisch inTMP).

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The formation of bromo complexes of Co(II) and Ni(II) is investigated in acetonitrile (AN), propanediol-1,2-carbonate (PDC) and trimethylphosphate (TMP) by spectrophotometric, potentiometric and conductometric methods. The following coordination forms are reported: [CoBr]⁺ (octahedral inAN andTMP), CoBr₂ (tetrahedral inAN, octahedral inTMP), [CoBr₃]^– tetrahedral inAN, octahedral inTMP), [CoBr₄]^2– (tetrahedral inAN andPDC, octahedral inTMP), [NiBr]⁺ (octahedral inAN), NiBr₂ (tetrahedral inAN, octahedral inTMP), [NiBr₃]^– (tetrahedral inAN), [NiBr₄]^2– (tetrahedral inAN andPDC, octahedral inTMP).

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Mit 8 Abbildungen     

Missing Member in the MIIMIIISi4N7 Compound Class: Carbothermal Reduction and Nitridation Synthesis Reveal Substitution of Nitrogen by Carbon and Oxygen in CaLu[Si4N7–2xCxOx]:Eu2+/Ce3+ (x≈0.3)

The nitridosilicate CaLu[Si₄N_7–2xC_xO_x] (x≈0.3) was synthesized by carbothermal reduction and nitridation starting from CaH₂, Lu₂O₃, graphite and amorphous Si₃N₄ at 1550 °C in a radiofrequency furnace. CaLu[Si₄N_7–2xC_xO_x] (x≈0.3) crystallizes isotypically to many previously known M^IIM^IIISi₄N₇ compounds in the space group P6₃mc, as was confirmed by Rietveld refinement based on powder X-ray diffraction data. Incorporation of carbon into the crystal structure as a result of the carbothermal synthesis route was confirmed by ¹³C and ²⁹Si MAS NMR spectroscopy. For the first time in the M^IIM^IIISi₄N₇ compound class, complementary EDX measurements suggest that simultaneous incorporation of oxygen compensates for the negative charge excess induced by carbon, resulting in an adjusted sum formula, CaLu[Si₄N_7–2xC_xO_x] (x≈0.3). When excited with UV-to-blue light, CaLu[Si₄N_7–2xC_xO_x] (x≈0.3) shows an emission maximum in the blue spectral region (λ_em=484 nm; fwhm=4531 cm⁻¹) upon doping with Ce³⁺, whereas Eu²⁺-doped CaLu[Si₄N_7–2xC_xO_x] (x≈0.3) exhibits a yellow-green emission (λ_em=546 nm; fwhm=3999 cm⁻¹).     

State of atoms and interatomic interactions in complex perovskite-like oxides: XXXI. Influence of magnesium concentration on chromium atoms state and interatomic interactions in lanthanum gallate doped with chromium and magnesium

Magnetic susceptibility of LaCr _x Ga_1−1.2x Mg_0.2x O_3−δ and LaCr _x Ga_1−1.5x Mg_0.5x O_3−δ solid solutions with the ratios [Cr]:[Mg] = 5:1 and 2:1 was studied. Fractions of clusters and single chromium atoms were calculated for the series of solid solutions with [Cr]:[Mg] = 5:1. The relation of the systems with [Cr]:[Mg] = 5:1 and [Cr]:[Sr]:[Mg] = 5:1:1 was revealed. For the system with [Cr]:[Mg] = 2:1 a temperature dependence of effective magnetic moment was found, which suggests that the exchange parameter is temperature dependent.     

Neue Sr‐Verbindungen mit planaren Al‐Si/Ge‐Anionen und eine Korrektur zu SrSi‐II und SrGe0.76

New Sr Compounds with Planar Al‐Si/Ge Anions and a Correction of SrSi‐II and SrGe_0.76 Planar anions with considerable p_π‐p_π interactions between heavier group 13 and 14 elements are observed in several alkaline earth trielides and tetrelides. In the intermetallics of the series SrAlxGe_2?x (border phases: x = 1: , a = 429.4(3), c = 474.4(3) pm, Z = 1, R1 = 0.0305, SrPtSb type and x = 1.6: P6/mmm, a = 440.4(2), c = 478.2(2) pm, Z = 1, R1 = 0.0125, AlB₂ type) graphite analogue planar Al/Ge nets with short Al‐Ge bonds are stacked in identical orientation, showing inter‐layer distances of approx. 475 pm. Starting from the related planar ribbons of condensed six‐membered rings in the known intermetallics (M^IV = Si, Ge) a series of new metal‐rich oxides with chain pieces consisting of three, two and finally only one six‐membered ring have been prepared and characterized on the basis of single crystal X‐ray data. The formal fragmentation of the ribbons is achieved by the incorporation of [OSr₆] octahedra, chains of which (connected via common corners) exactly fit the distance between the planar anions. The structures of the two compounds (M^IV = Si, Ge; formerly erroneously reported as SrSi and SrGe_0.76, space group Immm, a = 482.48(5)/484.55(8), b = 1306.5(2)/1342.2(2), c = 1814.0(2)/1857.4(3) pm, Z = 2, R1 = 0.0369/0.0316) contain isolated planar anions [M₂Al₂M₂Al₂M₂]^18? with only one six‐membered ring. In the monoclinic structures of the silicide Sr₁₃[Al₆Si₈][O] (C2/m, a = 2245.1(4), b = 482.76(5), c = 1720.6(5) pm, β=125.21(2)°, Z = 2, R1 = 0.0579) and the germanide Sr₁₆[Al₈Ge₁₀][O] (C2/m, a = 2287.23(14), b = 484.94(3), c = 2065.70(13) pm, β=120.150(4)°, Z = 2, R1 = 0.0730) anions [Si₂Al₂Si₂Al₂Si₂Al₂Si₂] and [Ge₂M₂Ge₂M₂Ge₂M₂Ge₂M₂Ge₂] with two and three six‐membered rings are left as fragments of the ribbons in Sr₃Al₂M₂. The puzzling bonding situation in these type of polar intermetallics at the Zintl border is calculated (using the DFT FP‐LAPW approach) for the structures with manageably small unit cells and discussed for the series SrAlM – Sr₃Al₂M₂ – Sr₁₆[Al₈M₁₀][O] – Sr₁₃[Al₆M₈][O] – Sr₁₀[Al₄M₆][O].     

1,2-Oxazoline durch Addition von Trimethylbenzonitriloxid an 2-Hydroxyethylamino-1,4-benzochinone und deren Chinolderivate

Summary Addition of trimethylbenzonitril oxide to 2-hydroxyethylamino-1,4-quinones and 3,4-dihydro-4-alkyl-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-ones leads to 7,8,9a,9b-tetrahydro-3aH-1,2-oxazolo[4,5-h]-1,4-benzoxazin-4(6H)-ones. In order to determine constitution and conformation of the addition products an NMR-spectroscopic analysis and an X-ray crystal structure analysis of 6-benzyl-9a-hydroxy-3-mesityl-7,8,9a,9b-tetrahydro-3aH-1,2-oxazolo[4,5-h]-31,4-benzoxazin-4-(6H)-one3a were carried out at room temperature: C₂₅H₂₆N₂O₄,M _r=418.49, monoclinic, P2₁/n,a=13.716(6),b=19.993(6),c=15.348(6) Å, = 98.55(4)°,V=4162(1)ų,Z=8,d _x=1.336g/cm³,R=6.77%,R _w=4.55% (2994 observables, 560 parameters).