Die verschiedenen Methoden zur Alkaloidbestimmung in Ephedra-Drogen

Analytical and Bioanalytical Chemistry -     

Studies on the thermotropic liquid crystalline polymer. VI. Synthesis and properties of homo- and co-poly(amide-azomethine-ether)

Two series of poly(amide-azomethine-ether)s and poly(ester-azomethine-ether)s were prepared by the condensation of dialdehydes with N,N'-bis(aminobenzamide)s and 4,4′-bis(p-aminophenyl)terephthalester, respectively. The thermotropic liquid crystalline properties were examined by DSC microscopic observations. Almost half of the synthesized polymers exhibit thermotropic liquid crystalline properties which are in the nematic phase since threaded and/or Schlieren textures are observed under polarizing microscope. The effects of the number of amide group and the nature of the nonlinear bibenzamide moiety, which link in the rigid segment, on the thermotropic liquid crystalline properties of the homo- and co-poly(amide-azomethine-ether)s were also investigated.     

X-Ray spectra and electronic correlations of FeSe(1-x)Te(x)

Critical issues concerning emerging Fe-based superconductors include the degree of electron correlation and the origin of the superconductivity. X-Ray absorption spectra (XAS) and resonant inelastic X-ray scattering spectra (RIXS) of FeSe(1-x)Te(x) (x = 0-1) single crystals were obtained to study their electronic properties that relate to electron correlation and superconductivity. The linewidth of Fe L(2,3)-edges XAS of FeSe(1-x)Te(x) is narrower than that of Fe-pnictides, revealing the difference between their hybridization effects and localization character and those of other Fe-pnictides. While no significant differences exist between the Fe L-edge XAS and RIXS of FeSe(1-x)Te(x) and those of Fe-pnictides, Se K-edge and Te K-edge XAS exhibit substantial edge shift, suggesting that the superconductivity in an Fe-Se superconductor is strongly associated with the ligand states. A comparison of the Se K-edge and Te K-edge spectra reveals that the charge transfer may occur between Se and Te. Given the Coulomb interaction and the bandwidth, the spectral results indicate that FeSe(1-x)Te(x) is unlikely to be a weakly correlated system unlike the Fe-pnictides of the "1111" and "122" families. The spectral results further demonstrate that superconductivity in this class of Fe-based compounds is strongly associated with the ligand 4p hole state.     

Anti-scratch and transparency properties of transparent conductive carbon nanotube films improved by incorporating polyethoxysiloxane

Transparent conductive films of single-walled carbon nanotubes (SWCNTs) were fabricated by a simple method to significantly enhance anti-scratch and transparency properties by the incorporation of polyethoxysiloxane (PES). The reasons for changes in the mechanical properties and transmittance were investigated through the reflection property and morphology of thin films. With the incorporation of PES, the sheet resistance of the SWCNT thin film remained unchanged after the anti-scratch test. It was found that the transmittance of the thin films suddenly increased when the thickness of the PES layer was ca 100 nm. Although the PES incorporation resulted in a slight increase in the sheet resistance, the experimental results revealed that the sheet resistance of the SWCNT thin films with PES was lower than that of films without PES for the same transmittance due to the increase of the transmittance caused by the PES incorporation. We have demonstrated that the sheet resistance was halved at a transmittance of ～86% due to PES incorporation. SWCNT thin films with PES showed better electrical properties than those without PES after a bend test.     

Electrophoresis of an ellipsoid along the axis of a cylindrical pore: effect of a charged boundary

The influence of a charged boundary on the electrophoretic behavior of a particle is investigated by considering the electrophoresis of a nonconducting ellipsoid along the axis of a cylindrical pore at the level of the linear Poisson-Boltzmann equation ignoring the polarization effect. The problem considered simulates the electrophoresis conducted in a narrow space such as capillary electrophoresis and electrophoresis through a porous medium. Here, because the effect of electroosmotic flow can be important the electrophoretic behavior is much more complicated than that for the case where a boundary is uncharged. The influences of the thickness of double layer, the aspect ratio of an ellipsoid, the relative radius of a pore, and the charge conditions on the ellipsoid and pore surfaces on the mobility of the ellipsoid are discussed. Several interesting but nonintuitive electrophoretic behaviors are observed.     

Star-shaped mesogens of triazine-based dendrons and dendrimers as unconventional columnar liquid crystals

Dendrons Gn-Cl and Gn-NH (n = 2-4) and novel dendrimers Gn-N approximately N-Gn (n = 2-4) based on triazine and piperazine units were efficiently prepared in good yields without employing the protection and deprotection processes and are fully characterized by 1H NMR and 13C NMR spectroscopies, elemental analysis, and mass spectroscopy. These compounds are transparent and possess good thermal stability. G4-Cl shows a monotropic columnar phase in a narrow range with a coexisting crystalline phase. Dendron G4-NH shows a rectangular column-phase, and dendrimer G4-N approximately N-G4 exhibits a monotropic hexagonal columnar phase. These identifications were supported by the polarizing optical scope and powder XRD studies.     

Cucurbitane Triterpenoids from the Fruit Pulp of Momordica charantia and Their Cytotoxic Activity

Two new cucurbitane‐type triterpenes, 25‐methoxycucurbita‐5,23(E)‐diene‐3β,19‐diol ( 1 ) and 7β‐ethoxy‐3β‐hydroxy‐25‐methoxycucurbita‐5,23(E)‐dien‐19‐al ( 2 ), together with three known cucurbitane‐type triterpenes, 3β,7β,25‐trihydroxycucurbita‐5,23(E)‐dien‐19‐al ( 3 ), (23E)‐3β‐hydroxy‐7β,25‐dimethoxycucurbita‐5,23‐dien‐19‐al ( 4 ), and 3β‐hydroxy‐25‐methoxycucurbita‐6,23(E)‐dien‐19,5β‐olide ( 5 ), were isolated from the fruit pulp of Momordica charantia. The structures of two new compounds were elucidated on the basis of 1D and 2D NMR, MS, IR, optical rotation. Among these isolates, compounds 1 , 2 , and 5 showed slight cytotoxic activity against the SK‐Hep 1 cell line with IC₅₀ values of 33.1, 24.3, and 38.7 μM, respectively.     

Nucleophilic Addition Reactions of Tricarbonyl [η5−1-(Phenylsulfonyl)cyclohexadienyl]iron(I) Complex

Hydride abstraction of tricarbonyl[η⁴-1-(phenylsulfonyl)-1,3-cyclohexadiene]iron(0) complex 2 with Ph₃C⁺PF₆^? regiospecifically provided the title compound 3 in excellent yield. Cationic complex 3 could react with a variety of nucleophiles in good yields. Soft nucleophiles prefer to attack at the C-5 position, whereas hard nucleophiles such as methyllithium and the enolate of ethyl acetate gave the C-5 as well as the C-2 addition products. Some synthetic applications of the addition products were also studied.     

The First Heteropentanuclear Extended Metal‐Atom Chain: [Ni+Ru25+Ni2+Ni2+(tripyridyldiamido)4(NCS)2]

This study develops the first heteropentametal extended metal atom chain (EMAC) in which a string of nickel cores is incorporated with a diruthenium unit to tune the molecular properties. Spectroscopic, crystallographic, and magnetic characterizations show the formation of a fully delocalized Ru₂⁵⁺ unit. This [Ru₂]‐containing EMAC exhibits single‐molecule conductance four‐fold superior to that of the pentanickel complex and results in features of negative differential resistance (NDR), which are unobserved in analogues of pentanickel and pentaruthenium EMACs. A plausible mechanism for the NDR behavior is proposed for this diruthenium‐modulated EMAC.