Two-photon spectroscopy of SnO2 under hydrostatic pressure

The pressure shift of S excitons in the rutile-type semiconductor tin oxide (SnO₂) is measured by two-photon absorption. From these data the pressure coefficients of the band gap (62.0 meV/GPa) and of the exciton binding energy (0.87 meV/GPa) are determined.     

EPR study of topoisomers of La@C82 and La@C90

An analysis of the temperature dependence of the line width variation of topoisomers (I) and (II) of La@C₈₂ revealed that both molecules exhibit practically identical rotational correlation times from room temperature down to the freezing point of CS₂. Although this result indicates confinement of the metal ion, from the increased line width of¹³C satellites in isomer (II) we conclude that in this molecule there might be increased mobility within a confine volume. Three stable topoisomers of La@C₉₀ were identified for the first time. One of these topoisomers was separated by HPLC technique. We were unable, however, to detect any nuclear spin dependence of the EPR line width even at low temperatures. This might indicate that in this case the ion is no longer confined to a specific binding site, although a more trivial explanation assuming small anisotropies of all hyperfine interactions cannot yet be ruled out.     

Total synthesis of iejimalide B

Iejimalide B, a structurally unique 24-membered polyene macrolide having a previously underutilized mode of anticancer activity, was synthesized according to a strategy employing Julia-Kocienski olefinations, a palladium-catalyzed Heck reaction, a palladium-catalyzed Marshall propargylation, a Keck-type esterification, and a palladium-catalyzed macrolide-forming, intramolecular Stille coupling of a highly complex cyclization substrate. The overall synthesis is efficient (19.5% overall yield for 15 linear steps) and allows for more practical scaled-up synthesis than previously reported strategies that differed in the order of assembly of key subunits and in the method of macrocyclization. The present synthesis paves the way for efficient preparation of analogues for drug development efforts.     

Synthesis and Spectral Study of Several Solid M3[Eu(2,6-Pyridinedicarboxylate)3] Salts (M=Li+, Na+, K+, Rb+, Cs+, NH4 +, and Pyridinium+)

Abstract

Salts of the [Eu(2,6-pyridinedicarboxylate)₃]^3- complex anion and various monovalent inorganic and organic counterions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺, and pyridinium⁺) have been synthesized and studied by emission spectroscopy. The Eu³⁺ ion emission spectra exhibited by these salts have been observed with high resolution (less than 1.0 cm^?1) and at low temperature (77 K). The emission spectra of these compounds indicate that changing the attached counterion does not affect the site symmetry observed by the europium ion beyond slight distortions indicated by small shifts in the energies of the Eu³⁺ electronic levels.     

Pion mass dependence of the nucleon mass in the chiral quark soliton model

The dependence of the nucleon mass on the mass of the pion is studied in the framework of the chiral quark-soliton model. A remarkable agreement is observed with lattice data from recent full dynamical simulations. The possibility and limitations to use the results from the chiral quark soliton model as a guideline for the chiral extrapolation of lattice data are discussed.     

Die Verfahren zur jodometrischen Zinnbestimmung in Mineralien

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