Paracrystalline Nature of Poly (p-Phenylene)

The electron diffraction pattern of oriented, annealed poly (p-phenylene) is explained on the basis of an orthorhombic unit cell: a = 0.7781, b = 0.5520 and c(fiber axis) = 0.4300 nm. and exhibits the following features:

(1)The reflections on the equator and meridian are sharp. Only a few weak diagonal reflections can be observed.

(2) Strong diffuse scattering is seen on the third layer line.

(3)The reflections on the meridian (00l-reflections) have a characteristic line profile. in which the intensity increases suddenly at the Bragg angle and decreases gradually.

From (1) to (3), it can be concluded that the material is paracrystalline like a nematic structure in liquid crystals. Molecular chains are laterally packed in a rather regular way. However, the disorder by the shift of chains in the direction parallel to their axes is remarkable.     

Fine tuning of the structure of phosphine–phosphoramidites: application for rhodium-catalyzed asymmetric hydrogenations

Diastereomers of (4-(diphenylphosphino)pentan-2-yl)-N-isopropyl-{dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxa-phosphepin-2-yl}-4-amine, (S)-(2S,4S)-1, and (S)-(2R,4R)-3; the octahydro derivative 4 of (S)-(2S,4S)-1, and derivative 2 of (S)-(2S,4S)-1 containing a 1,3-propanediyl backbone, have been synthesized and used for rhodium-catalyzed asymmetric hydrogenations of prochiral olefins in order to study the role of the stereogenic elements in the backbone and in the terminal moiety. The central chirality in the bridge has been found to determine the configuration of the product with a cooperative effect from the terminal groups. Excellent ee’s (up to 99.9%) were obtained in the hydrogenation of methyl (Z)-α-acetamidocinnamate using a rhodium complex with the matched arrangement (S)-(2S,4S)-1. The hydrogenation is accomplished in a highly enantioselective manner by using green solvents such as propylene carbonate.     

Molecular simulation of adsorption and transport diffusion of model fluids in carbon nanotubes

Grand canonical Monte Carlo (GCMC) and dual-control-volume grand canonical molecular dynamics (DCV-GCMD) simulations were carried out with Lennard-Jones model fluids in carbon nanotubes, with the objective of investigating the effect of varying molecular properties on adsorption and diffusion. The influence of the molecular weight, and the Lennard Jones parameters σ (a measure of the molecule size) and ? (a measure of the interaction strength) on adsorption isotherms, fluxes, and transport diffusivities was studied. For these simulations, the properties of component 1 in the mixture were held constant and one of the properties of component 2 was changed systematically. Furthermore, the validity of Graham's law, which relates the fluxes of two counter diffusing species to their molecular weight, was investigated on a molecular level. Graham's law is fulfilled for the whole range of molecular weights and Lennard-Jones parameters σ investigated. However, large deviations were observed for large values of ?₂. Here, the interaction of the two components in the mixture becomes so strong that component 1 is dragged along by component 2.     

Efficient synthesis of pentakis- and tris(pyridine) ligands

A variety of substituted tris(pyridyl) frameworks, as well as a pentakis(pyridine) system, are conveniently accessible in a one-pot synthesis, which consists of two sequential nucleophilic aromatic substitutions, employing substituted pyridine precursors.     

Polymer electrolyte membranes based on p‐toluenesulfonic acid doped poly(1‐vinyl‐1,2,4‐triazole): Synthesis,thermal and proton conductivity properties

Throughout this work, the synthesis, thermal as well as proton conducting properties of acid doped heterocyclic polymer were studied under anhydrous conditions. In this context, poly(1‐vinyl‐1,2,4‐triazole), PVTri was produced by free radical polymerization of 1‐vinyl‐1,2,4‐triazole with a high yield. The structure of the homopolymer was proved by FTIR and solid state ¹³C CP‐MAS NMR spectroscopy. The polymer was doped with p‐toluenesulfonic acid at various molar ratios, x = 0.5, 1, 1.5, 2, with respect to polymer repeating unit. The proton transfer from p‐toluenesulfonic acid to the triazole rings was proved with FTIR spectroscopy. Thermogravimetry analysis showed that the samples are thermally stable up to ～250 °C. Differential scanning calorimetry results illustrated that the materials are homogeneous and the dopant strongly affects the glass transition temperature of the host polymer. Cyclic voltammetry results showed that the electrochemical stability domain extends over 3 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Charge transport relaxation times were derived via complex electrical modulus formalism (M*). The temperature dependence of conductivity relaxation times showed that the proton conductivity occurs via structure diffusion. In the anhydrous state, the proton conductivity of PVTri1PTSA and PVTri2PTSA was measured as 8 × 10^?4 S/cm at 150 °C and 0.012 S/cm at 110 °C, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1016–1021, 2010     

Eu(fod)3 binding on the 1H‐NMR spectra of bis(2′‐ethylbenzoate)ethylene glycol podands

The complexing and selective binding constants of Eu(fod)₃ with bis(2′‐ethylbenzoate)ethylene glycol podands having one to four oxyethylene groups was observed on their ¹H‐NMR spectra at 250 MHz and 295 K in CDCl₃. The Eu(fod)₃ interaction displayed the selective binding role of oxygen on H₂C–O–CH₂ backbones with referring the ¹H chemical shifts. The estimated equilibrium constants, K_a, of 1:1 ratio of interactions were in accordance with the Eu(fod)₃ ionic radii to bind the oxygen sites depending on the size and conformation of the esters. Esters having one or two ethyleneoxy groups gave mainly 2:2 complexes using ester sites. The minimum lanthanide‐podand ester distance displayed the maximum stability so that ester with four oxyethylene groups was found to bind the Eu(fod)₃ moderately, whereas ester with three oxyethylene groups showed a large induced chemical shift due to the stability of Eu³⁺ complexes with larger ethyleneoxy groups. Copyright © 2012 John Wiley & Sons, Ltd.