Synthesis,characterization, and bonding properties of polymeric fullerides AC70.nNH3 (A = Ca,Sr, Ba,Eu, Yb)

Reduction of C70 with alkaline earth and rare earth metals dissolved in liquid ammonia results in metal fulleride solvates AC70.nNH3 (A = Ca, Sr, Ba, Eu, Yb) containing linear polymeric, anionic chains infinity 1 [C70(2-)]. The compounds were characterised by means of Raman spectroscopy and single-crystal structure determination. The accurate crystal structure of [Sr(NH3)8]C70.3NH3, determined with atomic resolution, allowed for a comparison with results of quantum chemical calculations. The nature of the C-C bonds in the fulleride is analysed in detail leading to a model explaining the unexpected polymerisation of C70(2-).     

Synthesis,Structure, and Properties of Scandium Dysprosium Antimonide ScDySb

Scandium dysprosium antimonide ScDySb was synthesized from scandium metal and DySb in an all‐solid state reaction at 1770 K. According to X‐ray analysis of the crystal structure [P4/nmm, Z = 4, a = 430.78(1) pm, c = 816.43(4) pm, R₁ = 0.0238, wR(all) = 0.0688, 268 independent reflections], ScDySb adopts the anti‐PbFCl type of structure, but with pronounced deviations in structural details, which are related to specific bonding interactions between the atoms involved. ScDySb shows antiferromagnetic ordering below 35.4 K, which was verified by susceptibility, heat capacity, and resistivity measurements. X‐ray structure determination, performed at 30 K, showed no significant structural changes to occur during the magnetic phase transition. The band structure was calculated in the framework of Density Functional Theory. The bonding properties are comparable to those of Sc₂Sb. Pronounced basins of the Electron Localization Function (ELF) appear in the tetragonal pyramidal Sc₄Dy voids.     

Necessary and sufficient conditions for existence of stationary solutions of some nonlinear stochastic systems

At the state of statistical stationarity, the response of a nonlinear system under multiplicative random excitations can be either trivial or non-trivial, depending on the spectral levels of the excitations and the values of certain system parameters. Assuming that the random excitations are Gaussian white noises, the two types of response may be investigated by way of their stationary densities, which are obtainable for first order dynamical systems and for higher order dynamical systems belonging to the class of generalized stationary potential. Alternatively, the Lyapunov exponents can be computed for perturbation from either the trivial or non-trivial solution, since a negative sign for the greatest Lyapunov exponent provides both the necessary and sufficient conditions for the stability of sample functions with probability one. It is shown in two specific examples, that the boundary at which the greatest Lyapunov exponent changes its sign coincides with the boundary for regularity (or being normalizable) for the probability density in both the trivial and non-trivial solutions. Thus, the stability conditions in the strong sense of probability one and the weak sense in distribution are identical in these cases.     

Zur Integration stochastischer Systeme mit stückweise linearen Kennlinien

Übersicht Stochastische Schwingungssysteme mit stückweise linearen Kennlinien oder Hystereseeigenschaften können mit Hilfe der Theorie der Markowschen Diffusionsprozesse exakt integriert werden. Diese neue Anwendung erlaubt, mehrdimensionale Verteilungsdichten und damit auch Mittelwerte oder Spektraldichten einfach und geschlossen anzugeben.

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Summary Stochastic dynamical systems with piecewise linear characteristics or hysteretic properties are exactly integrable by means of the theory of the Markow diffusion processes. This new application enables simple and closed calculations of multidimensional distribution functions and therewith mean values and spectral densities, too.

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Herrn Professor Dr. E. Mettler zum 70. Geburtstag gewidmet     

Synthesis,Crystal Structure,Bonding, and Properties of (Ba6O)(OsN3)2

The new barium nitridoosmate oxide (Ba₆O)(OsN₃)₂ was prepared by reacting elemental barium and osmium (3:1) in nitrogen at 815–830 °C. The crystal structure of (Ba₆O)(OsN₃)₂ as determined by laboratory powder X‐ray diffraction ( , No 148: a=b=8.112(1) Å, c=17.390(1) Å, V=991.0(1) ų, Z=3), consists of sheets of trigonal OsN₃ units and trigonal‐antiprismatic Ba₆O groups, and is structurally related to the “313 nitrides” AE₃MN₃ (AE=Ca, Sr, Ba, M=V–Co, Ga). Density functional calculations, using a hybrid functional, likewise indicate the existence of oxygen in the Ba₆ polyhedra. The oxidation state 4+ of osmium is confirmed, both by the calculations and by XPS measurements. The bonding properties of the OsN₃^5? units are analyzed and compared to the Raman spectrum. The compound is paramagnetic from room temperature down to T=10 K. Between room temperature and 100 K it obeys the Curie–Weiss law (μ=1.68 μ_B). (Ba₆O)(OsN₃)₂ is semiconducting with a good electronic conductivity at room temperature (8.74×10^?2 Ω^?1 cm^?1). Below 142 K the temperature dependence of the conductivity resembles that of a variable‐range hopping mechanism.     

Resolution of ephedrine derivatives by means of neutral and sulfated heptakis(2,3-di-O-acetyl)beta-cyclodextrins using capillary electrophoresis and nuclear magnetic resonance spectroscopy.

Beta-cyclodextrin (beta-CD), heptakis(2,3-di-O-acetyl)beta-cyclodextrin (Diac-beta-CD) and heptakis (2,3-di-O-acetyl-6-sulfato)beta-cyclodextrin (HDAS-beta-CD) were tested for their ability to discriminate the enantiomers of ephedrine, pseudoephedrine, norephedrine and methylephedrine. Using capillary electrophoresis (CE) under optimized conditions, with the exception of norephedrine in presence of beta-CD, all racemates could be resolved. Utilizing Job's plot by means of UV spectroscopy revealed 1:1 complexes formed with beta-CD and Diac-beta-CD. HDAS-beta-CD gave curved plots indicating mixed stoichiometry. Inspection of the cyclodextrin-induced chemical shifts (CICS) of both the ligands and the CDs showed that the ephedrine sits deeply in the cavity of beta-CD and HDAS-beta-CD. In the case of Diac-beta-CD, the ephedrine is located closely to the wider rim of the CD cavity. In conclusion, comparing the pattern of CICS of the various CD derivatives clearly indicates the differences in the complex geometry.