Convenient syntheses of metabolically important quercetin glucuronides and sulfates

Synthetic approaches to the major human plasma metabolites of quercetin, quercetin 3′-sulfate and the β-d-glucopyranosiduronic acid derivatives 3′-methylquercetin 3-glucuronide (isorhamnetin 3-glucuronide), quercetin 3-glucuronide and quercetin 3′-glucuronide are described. This is the first report of the chemical synthesis of quercetin 3′-glucuronide. All procedures start from the same precursor, 4′,7-di-O-benzylquercetin, and all are more convenient than existing methods.     

Understanding the Effects of Binders in Gas Sorption and Acidity of Aluminium Fumarate Extrudates

Understanding the impact of shaping processes on solid adsorbents is critical for the implementation of MOFs in industrial separation processes or as catalytic materials. Production of MOF-containing shaped particles is typically associated with loss of porosity and modification of acid sites, two phenomena that affect their performance. Herein, we report a detailed study on how extrusion affects the crystallinity, porosity, and acidity of the aluminium fumarate MOF with clays or SiO₂ gel binders. Thorough characterization showed that the clay binders confer the extrudates a good mechanical robustness at the expense of porosity, while silica gel shows an opposite trend. The CO₂ selectivity towards CH₄, of interest for natural gas separation processes, is maintained upon the extrusion process. Moreover, probe FTIR spectroscopy revealed no major changes in the types of acid sites. This study highlights that these abundant and inexpensive clay materials may be used for scaling MOFs as active adsorbents.     

N-(p-methoxyphenyl)-N-prop-2-ynyl-urea: a crystal structure with the rare Z′=5, and statistical data on Z′ values

The crystal structure of N-(p-methoxyphenyl)-N-prop-2-ynyl-urea contains five symmetry-independent molecules (Z′=5), which is a high and rarely occurring value. The five molecules have similar but not identical conformations, and form similar but not identical intermolecular interactions. The terminal alkyne groups of the five molecules are oriented differently, and form different hydrogen bond interactions (C–HO and C–Hπ). This is an example of how simple molecules can form a highly complicated solid state structure.     

Strong intramolecular O—H⋯O hydrogen bonds in quinaldic acid N‐oxide and picolinic acid N‐oxide

The title compounds contain very short intramolecular hydrogen bonds of the type C—O—H?O—N. The O?O distances are 2.425 (2) Å in picolinic acid N‐oxide (2‐carboxy­pyridine N‐oxide), C₆H₅NO₃, (I), and 2.435 (2) Å in quinaldic acid N‐oxide (2‐carboxy­quinoline N‐oxide), C₁₀H₇NO₃, (II). In (II), this is associated with slight molecular distortion from planarity, while in (I), such an effect cannot be observed because the mol­ecule crystallizes on a mirror plane.     

The appearance of gap solitons in a nonlinear Schrödinger lattice

We study the appearance of discrete gap solitons in a nonlinear Schrödinger model with a periodic on-site potential that possesses a gap evacuated of plane-wave solutions in the linear limit. For finite lattices supporting an anti-phase (q=π/2) gap edge phonon as an anharmonic standing wave in the nonlinear regime, gap solitons are numerically found to emerge via pitchfork bifurcations from the gap edge. Analytically, modulational instabilities between pairs of bifurcation points on this “nonlinear gap boundary” are found in terms of critical gap widths, turning to zero in the infinite-size limit, which are associated with the birth of the localized soliton as well as discrete multisolitons in the gap. Such tunable instabilities can be of relevance in exciting soliton states in modulated arrays of nonlinear optical waveguides or Bose-Einstein condensates in periodic potentials. For lattices whose gap edge phonon only asymptotically approaches the anti-phase solution, the nonlinear gap boundary splits in a bifurcation scenario leading to the birth of the discrete gap soliton as a continuable orbit to the gap edge in the linear limit. The instability-induced dynamics of the localized soliton in the gap regime is found to thermalize according to the Gibbsian equilibrium distribution, while the spontaneous formation of persisting intrinsically localized modes (discrete breathers) from the extended out-gap soliton reveals a phase transition of the solution.     

Synthesis,structures and luminescence properties of two gallium(III) complexes with 5,7-dimethyl-8-hydroxyquinoline

Luminescent gallium(III) complexes featuring 5,7-dimethyl-8-hydroxyquinoline (DimOx) are systematically compared and their structural features are correlated with their photophysical properties. The two complexes are chemically identical; however, contain various number of solvent molecules in the crystalline lattice which is representative of the bulk material confirmed by both nuclear magnetic resonance and elemental analysis. Detailed structural comparisons highlight the effect which the solvent molecules have on the intra- and intermolecular interactions. A distinct number of interactions are found for the gallium complex (1) containing more than one solvent molecule for unit cell. Variation in complex morphology is similarly observed via SEM micrographs. The distinct luminescent properties of the two gallium complexes appear directly related to octahedral coordination of the 8-hydroxyquinoline ligand as well as the number of identical coordinated solvent molecules.     

Crystal and molecular structures of three 2,2′-thio- and 2,2′-sulfonyl-bis(1,3-diarylprop-2-en-1-ones)

The X-ray crystal structures of 2,2-thio- and 2,2-sulfonylbis(1,3-diarylprop-2-en-1-ones) are determined [1: 2,2-thiobis(3-(p-chlorophenyl)-1-phenylprop-2-en-1-one), C₃₀H₂₀Cl₂O₂S, space group C2/c, a = 14.275(3), b = 6.280(1), c = 26.533(5) Å, = 94.55(3)°, Z = 1/2; 2: 2,2-sulfonylbis(1,3-diphenylprop-2-en-1-one), C₃₀H₂₂O₄S, space group P , a = 9.652(1), b = 12.044(1), c = 12.182(1) Å, = 61.985(6), = 77.511(5), = 74.340(6)°, Z = 1; 3: 2,2-sulfonylbis(3-(p-chlorophenyl)-1-phenylprop-2-en-1-one), C₃₀H₂₀Cl₂O₄S, space group P , a = 8.294(1), b = 13.175(2), c = 13.470(1) Å, = 62.870(9), = 83.796(7), = 85.282(8)°, Z = 1]. The C=C double bonds are all clearly defined. The sulfide 1 crystallizes on a crystallographic twofold axis, leading to a symmetric molecular conformation. The sulfones 2 and 3 crystallize on general positions, with different and irregular conformations.     

Asymptotic mechanical fields at the tip of a mode I crack in rubber-like solids

Asymptotic analyses of the mechanical fields in front of stationary and propagating cracks facilitate the understanding of the mechanical and physical state in front of crack tips, and they enable prediction of crack growth and failure. Furthermore, efficient modelling of arbitrary crack growth by use of XFEM (extended finite element method) requires accurate knowledge of the asymptotic crack tip fields. In the present work, we perform an asymptotic analysis of the mechanical fields in the vicinity of a propagating mode I crack in rubber. Plane deformation is assumed, and the material model is based on the Langevin function, which accounts for the finite extensibility of polymer chains. The Langevin function is approximated by a polynomial, and only the term of the highest order contributes to the asymptotic solution. The crack is predicted to adopt a wedge-like shape, i.e. the crack faces will be straight lines. The angle of the wedge and the order of the stress singularity depend on the hardening of the strain energy function. The present analysis shows that in materials with a significant hardening, the inertia term in the equations of motion becomes negligible in the asymptotic analysis. Hence, there is no upper theoretical limit to the crack speed.     

On the evolution equations for a self-gravitating charged scalar field

We consider a complex scalar field minimally coupled to gravity and to a U(1) gauge symmetry and we construct of a first order symmetric hyperbolic evolution system for the Einstein-Maxwell-Klein-Gordon system. Our analysis is based on a $1+3$ tetrad formalism which makes use of the components of the Weyl tensor as one of the unknowns. In order to ensure the symmetric hyperbolicity of the evolution equations, implied by the Bianchi identity, we introduce a tensor of rank 3 corresponding to the covariant derivative of the Faraday tensor, and two tensors of rank 2 for the covariant derivative of the vector potential and the scalar field.     

A conformal approach for the analysis of the non-linear stability of radiation cosmologies

The conformal Einstein equations for a trace-free (radiation) perfect fluid are derived in terms of the Levi-Civita connection of a conformally rescaled metric. These equations are used to provide a non-linear stability result for de Sitter-like trace-free (radiation) perfect fluid Friedman–Lemaître–Robertson–Walker cosmological models. The solutions thus obtained exist globally towards the future and are future geodesically complete.