Low-temperature structural phase transition in SrMo6S8 studied by X-ray powder diffraction

Lattice parameters as a function of temperature for, and atomic coordinates of the low-temperature phase of, SrMo₆S₈ are reported from X-ray powder diffraction. The structure transforms atT ₁=135(3) K from the rhombohedral high-temperature modification (R ,a _rh=6.5630 (3) Å, _rh=88.9982(2)°,V _rh=282.55(5)ų at 298 K) into the triclinic low-temperature modification (P ,a _tr=6.481(1)Å,b _tr=6.572(1)Å,c _tr=6.611(1)Å, _tr=89.246(4)°, _tr=89.304(4)°, _tr=88.169(4)°,V _tr=281.4(2)ų at 20K). The triclinic distortion is larger than in the Ca analogue, and similar to the Ba and Eu analogues.

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Untersuchung des Tieftemperatur-Phasenübergangs von SrMo₆S₈ mittels Röntgenpulverdiffraktometrie (Kurze Mitt.)

Zusammenfassung Die Temperaturabhängigkeit der Gitterparameter und die Atomlagen der Tieftemperaturphase von SrMo₆S₈ wurden mittels Röntgenpulverdiffraktometrie bestimmt. Die rhomboedrische Hochtemperaturmodifikation (R ,a _rh=6.5630(3)Å, _rh=88.9982(2)°,V _rh=282.55(5)ų,T=298 K) wandelt beiT ₁=135(3) K in die trikline Tieftemperaturmodifikation (P ,a _tr=6.481(1)Å,b _tr=6.572(1)Å,c _tr=6.611(1)Å, _tr=89.246(4)°, _tr=89.304(4)°, _tr=88.169(4)°,V _tr=281.4(2)ų,T=20 K) um. Die trikline Deformation ist stärker ausgeprägt als in der Ca-Verbindung und ähnlich jener der Ba- and Eu-Verbindung.

     

Studies on styrene phosphonic acid

Some properties of styrene phosphonic acid (SPA) were studied. The crystals were triclinic, witha=0.6434 nm,b=0.5842 nm,c=2.0338 nm, =96.17°, =97.33°, =79.65° andZ=4. SPA underwent a change in crystal structure at 78.8°C, the hydrocarbon network became disordered (liquid-like) at 138.5°C. Crystals melted at 148.6°C giving a cubic mesophase, then changed to an isotropic liquid at 155.6°C and at 162.13°C SPA underwent decomposition. Values for pK₁=2.15 and pK₂=7.66 were obtained at 25°C. The water solubility of SPA at several temperatures, and its interaction with surfactant micelles were determined.     

Cation distribution in Ni-substituted Mn-ferrites by Mössbauer technique

The neutron spectra of one outer (#10) and two inner (#2 and #3) sites of the Dalhousie University SLOWPOKE-2 reactor (DUSR) have been calibrated for the k ₀-based neutron activation analysis (k ₀-NAA). The parameters determined include the cadmium ratio (R _Cd), epithermal neutron flux shape factor (), subcadmium-to-epithermal neutron flux ratio (f), thermal-to-fast neutron flux ratio (f _F), modified spectral index r()(T_n/T₀)^1/2, Westcott g _Lu(T _n)-factor, and absolute neutron temperature (T _n). The a-values of -0.0098±0.0045 and -0.0425±0.0047 and -0.0422±0.0053 and f-values of 57.1±2.2 and 18.8±0.4 and 18.9±0.4 were obtained for the sites #10, #2 and #3, respectively. The modified spectral index (MSI), g _Lu(T _n)-factor, and T _n have been determined for the handling of non 1/v (n,) reactions. The accuracy of the method was evaluated by analyzing reference materials.     

Neutral molecule/crown ether interactions 5. Comparison of the C−H acidic interactions of nitromethane and acetonitrile with 18-crown-6 and dibenzo-18-crown-6. Crystal structures of dibenzo-18-crown-6·2 CH3NO2 and dibenzo-18-crown-6·2 CH3CN

Complete structural characterization of dibenzo-18-crown-6·2 CH₃NO₂ and dibenzo-18-crown-6·2 CH₃CN have been carried out, including location and refinement of the methyl hydrogen atoms. Dibenzo-18-crown-6·2 CH₃NO₂ is monoclinic,P2₁/c, with (at –150°C)a=9.573(2),b=14.636(2),c=33.471(7) Å, =93.77(2)°, andD _calc=1.37 g cm^–3 forZ=8. Interactions between the solvent methyl groups and the crown ethers and other solvent nitro groups associate the 1 : 2 complexes into polymeric chains alongb. The acetonitrile adduct exists as discreet 1 : 2 complexes in the solid state with C–H...O interactions exlusively to the ether. This complex is triclinic,P 1, with (at –150°C)a=9.458(6),b=9.570(5),c=14.404(5) Å, =73.18(4), =79.85(5), =66.82(6)°, andD _calc=1.28 g cm^–3 forZ=2. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82070 (22 pages).For part 4, see reference [1].     

Inclusion of water by a crown amide. First crystal structure of a respective host-guest combination

Crown amide (1) forms a stoicheiometric 1:1 inclusion complex with water, the X-ray crystal structure of which is reported. Crystals of1 · H₂O are triclinic, space groupP1, witha=7.503(1),b=11.394(3),c=13.443(2) Å, =107.066(18), =96.627(10), =106.377(14)°, andZ=2.R _F =0.039 for 1697 MoK reflections [I>3(I)] measured at 24°C. The structure features a hydrogen bonded hostguest relationship with concrete1 · H₂O units. Hydrogen bonds are between the water oxygen and O(4), N(4), respectively. The crystal packing shows a cavity arrangement of four ligands around each water molecule. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82055 (16 pages).     

Application of two kinetic methods to evaluate the trap energy of lithium fluoride + sodium fluoride thermoluminescent phosphor

A mixture of equal quantities of powdered LiF and NaF was doped with 0.2% each of Ti, Mg and Mn and heated to obtain a LiF+NaF phosphor. After grinding and sieving, the thermoluminescent phosphor was used to obtain the thermoluminescence characteristics such as the glow curve; the dose-response curve, sensitivity, reproducibility and linearity were all established. The main goal was to introduce two new methods for the calculation of trap energy: the single-peak-differential and single-peak-integration methods, both modifications of the basic method of Randall-Wilkins. The plots used to calculate the trap energy were In[(d/dT)1/(1-)]vs. 1/T and ln[ln(1-)/(T _o-T)]vs. 1/T, respectively. These linear plots with slopes of (E/k) gave trap energies ofE=0.547 eV andE=0.551 eV, respectively.     

Stereochemie von Metallocenen, 20. Mitt.: Die Ermittlung der optischen Reinheit der Methylferrocen-α-carbonsäure (40. Mitt. über Ferrocenderivate)

Zusammenfassung Die optische Reinheit der Methylferrocen--carbonsäure (1) wurde mit Hilfe zweier Methoden ermittelt. Die Isotopenverdünnung unter Verwendung von (²H₁-Methyl)ferrocen--carbonsäure sowie ein Verfahren, das auf der Auswertung der Intensitätsverhältnisse diastereotoper Protonen in denNMR-Spektren der -Phenäthylamide von1 (verschiedener Drehung) beruht, lieferten übereinstimmende Ergebnisse: [] _d für optisch reines1 beträgt 55,6±1,0° bzw. 54±3°. Der durch Racematspaltung von1 gefundene Wert beträgt 51,5±0,8° (bzw. 53±2°)³. Damit sind die Drehungen aller 90, mit1 bereits früher chemisch korrelierten Ferrocenderivate, wenn überhaupt, nur geringfügig zu korrigieren.

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The optical purity of methylferrocene--carboxylic acid (1) was determined by two methods: isotope dilution, employing (²H₁-methyl)ferrocene--carboxylic acid, and a procedure based on the evaluation of the relative intensities of diastereotopic protons in theNMR-spectra of the -phenethylamides of1 having different rotations. By both methods corresponding results were obtained: optically pure1 has an []d of 55.6±1.0° and 54±3°, resp. The value for1 as found by optical resolution is 51.5±0.8° and 53±2°, resp.³. Hence, the rotations of all 90 ferrocene derivatives previously correlated with1 by unambiguous chemical methods have—if at all—to be corrected only slightly.

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Mit 2 Abbildungen

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19. Mitt.:H. Falk undG. Haller, Mh. Chem.99, 1103 (1968).

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39. Mitt.:K. Schlögl undHeidelore Soukup, Mh. Chem.99, 927 (1968).     

Kristallstruktur und thermisches Verhalten von Tetrakaliumcyclo-tetraphosphat(V)-Dihydrat, (KPO3)4·2H2O

The crystal structure of (KPO₃)₄ · 2H₂O was solved by direct methods andFourier-syntheses (triclinic; P ;a=1 114.9 (2),b=821.9 (2),c=815.7 (3) pm; =88,88 (2), =84.51 (2), =82.70 (2)°;Z=2; 5910 unique reflections;R=0.052). The cyclic anions exhibit point symmetry S₄ with four terminal oxygens in axial and four in equatorial position. Thermal investigations (DTA, TGA, X-Ray-methods) show that the dehydration occurs in two steps. The anhydrous form of (KPO₃)₄ is stable above 230 °C and undergoes a second order phase transition which is complete at 515±5 °C.

     

Studies of Nanocrystalline Phase and Residual Amorphous Phase of FeCuNbSib Alloy Using TG(M) Technique

The —T and d/dT—T curves of the FeCuNbSiB amorphous alloy, which are the relationship between the total saturated magnetic moment per unit mass and temperature, are investigated by magnetic thermogravimetry analysis (TG(M)) technique. It is found that the crystallization process of the samples can be divided into five stages. The studies of samples annealed in temperature range of 480–610°C for 1h show that when the annealing temperature (T_a) is less than 540°C, the quantity of nanocrystalline -Fe(Si) phase increases evidently with T_a, and the Curie temperature (T_C) of residual amorphous phase also increases linearly with T_a, i.e. T_C=0.52T_a+91.7°C, with correlation coefficient =0.98. The variation of volume fraction of -Fe(Si) nanocrystalline phase or residual amorphous phase with T_a is measured by TG(M) technique.This revised version was published online in November 2005 with corrections to the Cover Date.     

Rate constants for addition of triethylsilyl radicals to spin traps

Conclusions The rate constants for the addition of triethylsilyl radicals to -phenyl-N-tert-butylnitrone (k_add=(11±5)·10⁶ liter/mole·sec) and 2,4,6-tri-tert-butylnitrosobenzene (k_add= (1.5±0.3)·10⁹ liter/mole·sec) at 20°C were determined by the EPR method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–941, April, 1984.     

Synthesis and x-ray crystal structure oftrans-diaquabis (4-morpholino) acetatocopper (II)

Summary An efficient procedure for the synthesis of the potassium salts of (4-morpholino)acetic acid, HL, and its -substituted derivatives is described. The title complex has been prepared and characterized by x-ray crystallography:a=8.505(2),b= 7.901(1),c=12.253(2) Å, =110.48(1)°, space groupP2₁/c,Z = 2, R_F=0.038 for 2300 observed MoK data. Hydrogen bonds link the centrosymmetrictrans-octahedral bis-chelated CuL₂(H₂O)₂ moieties into layers parallel to (100) in the crystal lattice.     

Thermally stimulated currents in poly(bis(p-fluorophenoxy)phosphazene)

Thermally stimulated currents (TSC) were examined for poly(bis(p-fluorophenoxy)phosphazene) (PBFPP) film. TSC showed peaks at the glass transition temperature (Tg=–4 °C) and atT(1) (160 °C – 170 °C), where-form crystal phase transformed to mesophase of-form structure. Another peak was found atT _cc betweenTg andT(1). Linear relationship between polarization field and peak current ofT _cc -peak was found, which shows thatT _cc -peak was caused by motion of dipolar groups in crystalline phase. When heating (up to 200 °C) and cooling (down to 20 °C) thermal process was repeated,T _cc -peak shifted to higher temperature region approachingT(1) and simultaneously, the peak current ofT(1)-peak became smaller. Activation energy, time constant of dipolar relaxation and charge mobility were evaluated forT _cc -peak. From these results, it was concluded that-form and more ordered- form crystalline phases coexisted in PBFPP once heated aboveT(1) and the content of- form phase increased by repeated thermal hysteresis.     

Strukturuntersuchungen an Poly-3,3-bis(chloromethyl)-oxacyclobutan

Zusammenfassung Im Elektronenbeugungsbild zeigen aus der Schmelze gewachsene Penton-Sphärolithe eine bevorzugte Orientierung der Elementarzelle: diea-Achse liegt radial und dieb- undc-Achse tangential.Penton kristallisiert aus einer Xylollösung in derForm. Die aus dem Elektronenbeugungsbild bestimmte Elementarzelle konnte mit Röntgenweitwinkelaufnahmen an orientiertem Material bestätigt werden:=17,85 Å, b=8,16 Å, c=4,8 Å. Röntgenkleinwinkeluntersuchungen zeigen bei Kristallisationstemperaturen zwischen 60 und 135 °C eine Zunahme der Langperiode von 70 auf 135 Å. Elektronenmikroskopisch gemessene Lamellendicken stimmen mit den Langperioden überein.

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Summary Penton-spherulites grown from the melt show a favoured orientation in the electron-diffraction-pattern thea-axis being radial and theb- andc-axis tangential.Penton crystallizes from a xylene-solution in the-form. The elementary-cell, determined from the electron-diffraction-pattern, was confirmed byX-raywide-angle-patterns of oriented material:=17,85 Å,b=8,16 Å,c=4,8 Å.X-ray-low-angle-analysis shows an increase of the long-period from 70 to 135 Å at crystallisation-temperatures from 60 to 135 °C, respectively. The thicknesses of the lamellas, as measured in the electronmicroscope, are in convenience with the long-periods.

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Herrn Professor Dr.K. -H. Hellwege und Herrn Dr.U. Johnsen danken wir für Anregung und Diskussionen.     

Withasteroids ofPhysalis VI.1H and13C NMR spectra of withasteroids ixocarpalactone A and ixocarpanolide

The¹H and¹³C NMR spectra of two withasteroids isolated fromPhysalis ixocarpa Brot. have been studied in detail. Their spectral characteristics are discussed. A comparison of the results obtained has led to the identification of a withasteroid with the composition C₂₈H₄₀O₈, mp 291–292°C (from methanol) as ixocarpalactone A, in spite of some difference in its physical constants. The other compound, with mp 252–253°C (from methanol), had the composition C₂₈H₄₀O₆, [] _D ²⁰ +27±4°, is new and has been called ixocarpanolide. The structure of 5,20R-dihydroxy-1-oxo-6, 7-epoxy-22R-witha-2-enolide has been proposed for it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 326–332, May–June, 1986.     

Phase equilibria in the Ag4SSe-SnTe system

The phase diagram of the system Ag₄SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag₄SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag₄SSe·SnTe (phase A) and -Ag₄SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, =101.32°, =85.90°, =111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm, =90.74°, =108.94°, =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T _- =110°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

The designed synthesis and crystallographic characterization of three novel heterotrimetallic linear complexes of [Et4N][(Ph3P)2{M′S2 MS2Fe}Cl2] (M=Mo,M′=Ag;M=W,M′=Cu,Ag)

The complexes [Et₄N][(Ph₃P)₂{MS₂ MS₂Fe}Cl₂] (M=Mo,M=Ag;M=W,M=Cu, Ag) have been obtained by reaction of [Et₄N]₂[S₂ MS₂FeCl₂] (M=Mo, W) with Cu(PPh₃)₃Cl or Ag(PPh₃)₃NO₃ in MeCN/CH₂Cl₂, respectively. Crystal data for [Et₄N][(PPh₃)₂ {AgS₂MoS₂Fe}Cl₂] (I): triclinic, P (No. 2),Z=2,a=13.41(1)Å,b=15.54(1)Å,c=12.30(1)Å, =105.24(6)°, =94.63(7)°, =101.38(6)°, andV=2399(4)ų. The bond lengths of Mo-Fe bond and the Mo-Ag distance are 2.756(2)Å and 3.033(2)Å, respectively. Crystal data for [Et₄N][(PPh₃)₂ {AgS₂WS₂Fe}Cl₂] (II): triclinic, P (No. 2),Z=2,a=13.457(5))Å,b=15.601(6)Å,c=12.338(4)Å, =105.20(3)°, =94.61(4)°, =101.43(4)°, andV=2426(2)ų. The bond length of W-Fe bond and the W-Ag distance are 2.786(2)Å and 3.076(1)Å, respectively. Crystal data for [Et₄N][(PPh₃)₂ {CuS₂WS₂Fe}Cl₂] (III): triclinic, P (No. 2),Z=2,a=13.498(5)Å,b=15.372(4)Å,c=12.340(4)Å, =105.54(2)°, =93.32(3)°, =101.40(3)°, andV=2401(1)ų. The bond lengths of W-Fe bond and the W-Cu bond are 2.800(1)Å and 2.851(1)Å, respectively.     

Phytoecdysteroids of plants of the genusSilene X. Sileneoside E — 2-Deoxy-α-ecdysone 3-O-β-D-glucopyranoside — FromSilene brahuica

A new ecdysteroid has been isolated from the epigeal organs ofSilene brahuica Boiss. — 2-deoxy--ecdysone 3-O--D-glucopyranoside (I), C₃₃H₅₄O₁₀, mp 195–196°C, [] _D ²⁰ + 44.4° (methanol). The enzymatic hydrolysis of (I) led to 2-deoxy--ecdysone. Details of the IR, UV, mass, and¹H and¹³C NMR spectra of all the compounds are given.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 323–326, May–June, 1986.     

Simultaneous flow measurement of specific heats and thermal expansion coefficients of liquids: Aqueoust-BuOH mixtures and neat alkanols and alkanediols at 25°C

A flow method is described for the simultaneous measurement of volumetric specific heat capacities c _p ^v and thermal expansion coefficients of liquids, using a Picker heat capacity microcalorimeter. the method involves a simple sequence of operations in which the calorimeter unit is used alternately to measure a difference in volumetric specific heats at constant flow rate and temperature, or a flow rate variation resulting from a temperature scan on a flow cell. The precision of the method in measurements is close to 1% which is comparable to that of current dilatometric methods; the overall time for the combined c _p ^v - measurement is less than 30 minutes. Typical uses and reliability of the method are illustrated through results for aqueous NaCl solutions, t-BuOH-water mixtures, and ,-diols (C₂–C₅) at 25°C. The and c _p ^v values in homologous series of normal alkanes, alcohols and diols appear well represented by equations comprising two contributions, one related to the hydrocarbon chain length, the other dependent on the number density of –OH groups. The general trends in these data and comparison with similar results for H₂O₂ and H₂O illustrate the magnitude of the c _p ^v and anomalies in liquid water.     

Preparation and structure of (calix[8]arene methyl ether) · 2CDCl3

The methyl ether of calix[8]arene crystallizes from CDCl₃ with two molecules of the solvent per molecule of host. An X-ray structural investigation has shown that the CDCl₃ guests exist within the calixarene framework. The complex resides on a crystallographic center of inversion, and the cavity is roughly circular in projection as measured by the distance between centroids of aromatic rings related by the center: 14.5, 13.9, 10.1, and 11.2 Å. Six of the oxygen atoms are found on the inside and two on the outside. Crystals belong to the triclinic space group witha=11.741(9),b=11.810(9),c=12.484(8) Å, =94.74(8), =104.41(8), =111.30(9)°, andD _c =1.31 g cm^–3 forZ=1. Refinement led to a finalR value of 0.086 for 949 observed reflections. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82038 (10 pages).     

Wide angle X-ray diffraction studies of polytetrafluoroethylene and ethylen-tetrafluoroethylen-bipolymers in the range 9.5 K–270 K

PTFE shows in the whole temperature range investigated a triclinic crystal structure with cell parametersa=0.952 nm,b=0.559 nm,c=1.706 nm,=87.9°, = 90.0° and=91.8°. The temperature dependence ofa andb-axis is linear, thec-axis shows a change in thermal expansion at 150 K. The inherent strain is small. The crystallite sizes are measured, paracrystalline distortions are absent.The bipolymers show only an ordered arrangement in lateral direction under maintenance of the helical structure. The lateral arrangement is very distorted and the range of order is aboutD _L 10 nm.