Search results for "CONDENSED MATTER"
showing 10 items of 13918 documents
Crystal structure of 1-hydroxy-2,2,6,6-tetramethylpiperidin-1-ium trifluoromethanesulfonate
2015
In the cation of the title salt, C9H20NO+·CF3O3S−, the six-membered heterocyclic ring displays a chair conformation. In the crystal, centrosymmetric pairs of cations and anions are linked by N—H...O and O—H...O hydrogen bonds to form rings with aR44(14) graph-set motif.
Crystal structure of an epoxysterol: 9α,11α-epoxy-5α-cholest-7-ene-3β,5,6α-triol 3,6-diacetate
2017
The title compound is a polyoxygenated epoxy steroid that crystallizes in the P212121 space group.
Densities and viscosities of imidazolium and pyridinium chloroaluminate ionic liquids
2013
Abstract The chloroaluminate ionic liquids are used in various types of reactions. However, due to their particular vulnerability on water, their physical properties have not been previously investigated very extensively. The densities and viscosities of series imidazolium and pyridinium chloroaluminate ionic liquids having alkyl (butyl, hexyl, octyl) or aralkyl (benzyl, ethylphenyl) chain at the cation, various effective molar fraction of AlCl 3 (χ AlCl3 = 0.5, 0.65, 0.7), as well as they mixture and mixture with common organic solvents (hexane, toluene) were measured at the temperature range 293.15–343.15 K (20–70 °C). Densities, and particularly viscosities decrease with the increase of…
Spin transition in heptanuclear star-shaped iron(III)–antimony(V) NCS- and CN-bridged compounds
2009
Abstract The precursor [FeIII(L)Cl] (LH2 = N,N′-bis(2′-hydroxy-benzyliden)-1,6-diamino-3-azahexane) has been prepared and Mossbauer spectroscopy assigned a high-spin (S = 5/2) state at room temperature. The precursor is combined with the bridging units [SbV(X)6]− (X = CN−, NCS−) to yield star-shaped heptanuclear clusters [(LFeIII–X)6SbV]Cl5. The star-shaped compounds are in general high-spin systems at room temperature. On cooling to 20 K some of the iron(III) centers switch to the low-spin state as indicated by Mossbauer spectroscopy, i.e. multiple electronic transitions. While the cyano-bridged complex performs a multiple spin transition the thiocyanate-compound shows no significant popul…
Stratification in Drying Polymer–Polymer and Colloid–Polymer Mixtures
2017
Drying polymer-polymer and colloid-polymer mixtures were studied using Langevin dynamics computer simulations. Polymer-polymer mixtures vertically stratified into layers, with the shorter polymers enriched near the drying interface and the longer polymers pushed down toward the substrate. Colloid-polymer mixtures stratified into a polymer-on-top structure when the polymer radius of gyration was comparable to or smaller than the colloid diameter, and a colloid-on-top structure otherwise. We also developed a theoretical model for the drying mixtures based on dynamical density functional theory, which gave excellent quantitative agreement with the simulations for the polymer-polymer mixtures a…
Crystal structure of C-2-benzo-thia-zole-N-methyl-nitrone.
2015
The molecule of the title compound {systematic name:N-[(benzothiazol-2-yl)methylidene]methylamineN-oxide}, C9H8N2OS, is close to planar [maximum deviation from the mean plane = 0.081 (2) Å], its conformation being stabilized by a strong intramolecular attractive S...O interaction [2.6977 (16) Å]. In the crystal, molecules are linked into centrosymmetric dimers by pairs of weak C—H...O hydrogen bonds.
(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect
2006
The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L = Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at …
N-Alkyl ammonium resorcinarene polyiodides
2016
Four N-alkyl ammonium resorcinarene halides incorporating polyiodides were obtained and structurally analyzed by single crystal X-ray crystallography. The unexpected formation of triiodides and pentaiodide anions in these structures was assumed to be the result of the heterolytic dissociation of molecular iodine (I2) in the presence of electron donors in the N-alkyl ammonium resorcinarene halide system, from which I− further binds one or two I2 molecules resulting in I3− or I5− species, respectively.
Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure
2000
Optical absorption of the diluted magnetic semiconductor Zn 1-x Co x Se (x = 0.02) has been measured at room temperature under hydrostatic pressure up to 14 GPa in a membrane diamond-anvil cell. We found two absorption features: (i) an absorption structure in the energy range 1.5 to 1.8 eV, with a negligible pressure shift (i.e. (0.45 ± 0.05) meV/GPa) which we have identified as the Co 2+ (3d 7 ) internal transition 4 A 2 (F) → 4 T 1 (P) and (ii) an onset in the energy range 2 to 2.7 eV which redshifts with pressure (dE/dP = (-8.1 ± 0.6) meV/GPa). We have attributed such absorption edge to charge transfer between the ZnSe valence band and the Co 2+ (3d 7 ) levels. On the assumption that tho…
Données expérimentales et modélisation d’adsorption des systèmes N2(g)/montmorillonite potassique de Camp-Berteau et N2(g)/hydrotalcite carbonatée
1999
Resume In this paper capacities of adsorption of nitrogen onto two clays at 77 K are compared and analyzed. One system is a montmorillonite of Camp-Berteau saturated by potassium cation and the second one is an hydrotalcite saturated by carbonate anion. Adsorbed amounts have been obtained using a volumetric technique. So it is shown that the smectite adsorbed more than the hydrotalcite at the same relative pressure of nitrogen. The modelling of experimental data by various theories of adsorption as de Brunauer, Emmett et Teller (BET) and t-method are used to calculate the specific surface and to have access to the porosity of these materials at 77 K. Then it is shown that the adsorption of …