A cyclic oligophenylene containing two 1,8-naphthalene units bridged by two face-to-face biphenyl linkages exhibiting unusual strain and pi-pi interaction

1,8-[1,8-Naphthalenediylbis(4',4-biphenyldiyl)]naphthalene, a very stable strained cyclophane, has been synthesized in moderate yield using the copper-catalyzed coupling of 1, 8-bis(4-(tributylstannyl)phenyl)naphthalene. The X-ray analysis of the titled compound discloses bent p,p'-biphenylylene chains with splayed naphthalene rings, and the p,p'-biphenylylene chains located face-to-face indicate a fairly strong pi-pi interaction.     

Fällung nichtionogener Tenside durch Polymersäuren. Zusatzeffekt anorganischer Salze und Säure

Zusammenfassung Zusatz von Säure oder anorganischen Salzen, insbesondere von mehrwertigen Kationen, bewirkt die Fällung nichtionogener Tenside vom Typus des Polyoxyäthylens aus Wasser in Gegenwart von Polymersäuren wie Polyakrylsäure und Polymethakrylsäure, und zwar der Wirkung nach zunehmend mit der Temperatur. Die nichtionogenen Tenside bilden wasserlösliche Komplexe mit diesen Polymersäuren, und die Kationen und H⁺ veranlassen Kontraktion der Komplexe und führensomit zu ihrer Fällung. Die Rolle der Gegenionen (Anionen) ist bei hohen Salzkonzentrationen nicht zu vernachlässigen. Der Komplex von Polymersäure und nichtionogenen Tensiden mit län geren Polyoxyäthylenketten ist auf die Fällung hin sichtlich ihrer Zusätze weniger von Einfluß.

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Summary Addition of acid or inorganic salts, particularly of polyvalent cations, causes precipitation of nonionic surfactants of the polyoxyethylene type from water in the presence of polymeric acids, such as polyacrylic and polymethacrylic acids. The precipitation takes place more remarkably at higher temperature. The non-ionics form water-soluble complexes with these polymeric acids, and the cations and H+ give rise to contraction of the complexes, thus leading them to precipitation. The counterions (anions) also play some part in the precipitation reaction at high salt concentrations. The complex of polymeric acid and nonionics with longer polyoxyethylene chains is less affected by these additives on precipitation.

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Mit 9 Abbildungen     

Measurement of Cu K-shell and Ag L-shell ionization cross sections by low-energy positron impact

Inner shell ionization cross sections by low-energy positron impact have been measured. Development of an x-ray detector with thin Si(Li) crystals has enabled the first measurements of the absolute cross sections for the positron impacts in the energy range below 30 keV. Threshold behavior of the measured cross sections for the Cu K shell and Ag L shell are compared with the theoretical results of Gryzinski and Kowalski [Phys. Lett. A 183, 196 (1993)]] and Khare and Wadehra [Can. J. Phys. 74, 376 (1996)]]. Good agreement has been found for the Cu K shell, while the experimental values for the Ag L shell were found to be smaller than the corresponding theoretical results.     

Asymptotics for the nonlinear dissipative wave equation

We are interested in the asymptotic behaviour of global classical solutions to the initial-boundary value problem for the nonlinear dissipative wave equation in the whole space or the exterior domain outside a star-shaped obstacle. We shall treat the nonlinear dissipative term like , , 0)$"> and prove that the energy does not in general decay. Further, we can deduce that the classical solution is asymptotically free and the local energy decays at a certain rate as the time goes to infinity.

     

Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser‐enhanced magnetic resonance imaging

Agarose is a tissue‐equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3‐carboxy‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl (carboxy‐PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy‐PROXYL in phosphate‐buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy‐PROXYL in water/agarose mixture (99 : 1) compared with phosphate‐buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy‐PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser‐enhanced magnetic resonance imaging.     

Irreversible helix rearrangement from Cis‐transoid to Cis‐cisoid in poly(p‐n‐hexyloxyphenylacetylene) induced by heat‐treatment in solid phase

Polymerization of p‐n‐hexyloxyphenylacetylene (pHPA) by using a [Rh(norbornadine)Cl]₂‐triethylamine catalyst was carried out at room temperature to afford stereoregular helical poly(p‐n‐hexyloxyphenylacetylene)s (PpHPAs). When ethanol and n‐hexane were used as polymerization solvents, a bright yellow PpHPAs, poly( Y ) with M_n = 8.5 × 10⁴ and its purple red polymer, poly( R ) with M_n = 5.3 × 10⁴ were obtained in 95% yields and 84% yields, respectively. Diffuse reflective UV–vis spectra of poly( Y ) and poly( R ) in solid phase showed different broad absorption peaks at 445 and 575 nm, respectively. X‐Ray diffraction patterns of poly( Y ) and poly( R ) showed typical columnar structures assignable to cis‐transoid and cis‐cisoid structures, respectively, which were also supported by molecule mechanics calculation. Poly( Y ) was irreversibly transformed to a reddish‐black polymer, poly( Y‐B ), which columnar diameter was nearly the same as that of poly( R ). Further, poly( Y ) showed an exothermic peak in the differential scanning calorimetry trace at 80 °C for 1 h in N₂ gas. Thus, these findings suggest a thermally irreversible rearrangement from an unstable cis‐transoid form, poly( Y ) with a stretched cis‐transoid helix to a stable cis‐cisoid form, poly( R ), with a contracted cis‐cisoid helix in the solid phase to give poly( Y → B ) with the cis‐cisoid form. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Free radical copolymerization of sulfur dioxide with phenylacetylene

Free radical copolymerization of sulfur dioxide with phenylacetylene (PA) in o-dichlorobenzene was studied in a range of temperatures from 30 to 80^oC as a function of total monomer concentration ([SO₂] + [PA]). PA content in the copolymers increases with decreasing total monomer concentration and increasing temperature. M _w/M _n becomes sharper with decreasing the total monomer concentration, but does not depend upon feed compositions which are changed keeping total monomer concentration constant at 2, 4, and 6 mol/L, respectively. These results strongly indicate the existence of depropagation. Thermal decomposition of the copolymers happens more easily than PA homopolymer and the carbon-centered free radicals are detected during the decomposition. Reactivity of ～ CH??(Ph) free radical (～ PA · ) is also discussed.     

An Efficient Halogen‐Free Electrolyte for Use in Rechargeable Magnesium Batteries

Unlocking the full potential of rechargeable magnesium batteries has been partially hindered by the reliance on chloride‐based complex systems. Despite the high anodic stability of these electrolytes, they are corrosive toward metallic battery components, which reduce their practical electrochemical window. Following on our new design concept involving boron cluster anions, monocarborane CB₁₁H₁₂^? produced the first halogen‐free, simple‐type Mg salt that is compatible with Mg metal and displays an oxidative stability surpassing that of ether solvents. Owing to its inertness and non‐corrosive nature, the Mg(CB₁₁H₁₂)₂/tetraglyme (MMC/G4) electrolyte system permits standardized methods of high‐voltage cathode testing that uses a typical coin cell. This achievement is a turning point in the research and development of Mg electrolytes that has deep implications on realizing practical rechargeable Mg batteries.     

Phosphoproteome Profiling Using a Fluorescent Phosphosensor Dye in Two-Dimensional Polyacrylamide Gel Electrophoresis

We validated the novel PhosphoQUANTI SolidBlue Complex (PQSC) dye for the sensitive fluorescent detection of phosphorylated proteins in polyacrylamide- and two-dimensional gel electrophoresis (PAGE and 2DE, respectively). PQSC can detect as little as 15.6 ng of ß-casein, a pentaphosphorylated protein, and 61.3 ng of ovalbumin, a diphosphorylated protein. Fluorescence intensity correlates with the number of phosphorylated residues on the protein. To demonstrate the specificity of PQSC for phosphoproteins, enzymatically dephosphorylated lysates of Swiss 3T3 cells were separated in 2DE gels and stained by PQSC. The fluorescence signals in these gels were markedly reduced following dephosphorylation. When the phosphorylated proteins in Swiss 3T3 cell lysates were concentrated using a phosphoprotein enrichment column, the majority of phosphoproteins showed fluorescence signals in the pI 4–5 range. Finally, we performed phosphoproteome analysis to study differences in the protein phosphorylation profiles of proliferating and quiescent Swiss 3T3 cells. Over 135 discernible protein spots were detected, from which a selection of 15 spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF-MS). The PQSC staining procedure for phosphoprotein detection is simple, reversible, and fully compatible with MALDI TOF-MS.