Theoretical study of unimolecular rearrangements of vinylidenes to acetylenes

The rearrangement of vinylidene to acetylene has been studied in detail by the density functional method, using Becke's three‐parameter exchange functional and the gradient‐corrected functional of Lee, Yang, and Parr. The rearrangement of the anion, as well as that of fluoro‐substituted systems, has also been investigated, in order to determine the effect of fluorine substitution on the activation barrier to the 1,2‐hydrogen shift, as well as the relative migratory aptitudes of hydrogen and fluorine. Natural bond orbital analysis is invoked to gain insight into the mechanisms of the rearrangements. Basis size effects are also discussed, particularly in relation to anionic systems. The need to include diffuse functions in geometry optimizations of anionic systems is reinforced by the present calculations. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Mirror image nanostructures

Chiral molecules that self-assemble to form chiral supramolecular structures exhibit interesting structural features reminiscent of tertiary and quaternary structures of proteins and have applications in catalysis and nonlinear optics. Often, these structures are hierarchical, with their chiral structure difficult to interpret on the molecular scale. In this communication, we observe chiral assembling molecules that form well-defined helices with a pitch of 28 nm. We observe the behavior in both R- and S-enantiomers of the molecule, forming mirror image nanostructures. The molecular chirality is determined by the dimethyloctyl alkyl coil of the molecule and is located more than 4 nm from the hydrogen-bonding segment. The nanostructures observed are not hierarchical, which could be a result of the significant separation between the stereocenter and hydrogen-bonding dendron. The subtle structural modification at the periphery of the molecule biases the supramolecular assembly, which is driven primarily by strong hydrogen-bonding and pi-pi stacking interactions.     

Enantioselective separation on a naturally chiral surface

Kinked-stepped, high Miller index surfaces of metal crystals are chiral and, therefore, exhibit enantiospecific properties. Previous temperature-programmed desorption (TPD) spectra have shown that the desorption energies of R-3-methylcyclohexanone (R-3-MCHO) on the chiral Cu(643)(R) and Cu(643)(S) surfaces are enantiospecific (J. Am. Chem. Soc. 2002, 124, 2384). Here, a comparison of the TPD spectra from Cu(111), Cu(221), Cu(533), Cu(653)(R&S), and Cu(643)(R&S) surfaces reveals that the enantiospecific desorption occurs from the chiral kink sites on the Cu(643) surfaces. Titration of the chiral kink sites with I atoms confirms this assignment of desorption features in the TPD spectra. Finally, the enantiospecific difference in the desorption energies of R- and S-3-MCHO has been used as the basis for demonstration of an enantioselective, kinetic separation of racemic 3-MCHO into its purified components during adsorption and desorption on the Cu(643)(R&S) surfaces.     

Synthesis,characterization, molecular docking and biological activity of 5,6-bis-(4-fluoro-phenyl)-3,4,7,8-tetraaza-bicyclo[8.3.1]tetradeca-1(13),4,6,10(14),11-pentaene-2,9-dione and its transition metal complexes

Macrocyclic Schiff base ligand through the condensation of 1,3-dicarbonyl-phenyl-dihydrazide with 4,4′-difluorobenzil and its Co(II), Ni(II), Cu(II) and Zn(II) metal complexes have been synthesized. The ligand and metal complexes were characterized by analytical and physicochemical methods. An octahedral geometry arising from coordination of N2O2 donor atoms from the macrocyclic framework has been proposed for all metal complexes. Synthesized ligand and metal complexes were investigated for in vitro antibacterial and antioxidant activity. Complex [Ni(C₂₂H₁₄N₄F₂O₂)(OCOCH₃)₂] has shown remarkable antibacterial activity (Minimum inhibitory concentration 8–16?μg/ml) comparable to commercial antibiotic Ciprofloxacin. Anticancer activity of synthesized compounds against Squamous Cell Carcinoma (SCC4), head and neck cancer cell line has also been studied at different concentrations and at different time points. Complexes [Co(C₂₂H₁₄N₄F₂O₂)(NO₃)₂] and [Cu(C₂₂H₁₄N₄F₂O₂)(OCOCH₃)₂] have shown remarkable anticancer results (IC₅₀ 31.1 and 43.1?μM) against the tested cell line in concentration dependent manner. Molecular docking studies were carried out to find the binding mode of the synthesized macrocyclic Schiff base ligand to Epidermal Growth Factor Receptor (EGFR) Kinase (PDB ID: 1M17).     

Comparable Ionicity of the Solutions of Aprotic and Protic Ionic Liquids by Anion Substitution

Temperature dependent molar conductances and fluidities of bisulfate and ethyl sulfate anion-based ionic liquids were measured. The extent of dissociation of the ionic liquids was estimated from the Walden plot in term of ionicity. The ionicity mainly depends on the magnitude of Coulombic forces, altered by the anion’s Lewis basicity. Aqueous solutions of aprotic ionic liquids, in general, possesses ionicity in the range of ≈70–99%. This article reveals that the substitution of the anion by bisulfate and ethylsulfate reduces the ionicity of aqueous solution of these ionic liquids to the range of 10–37%. This is very close to that exhibited by some of the protic ionic liquids and phosphonium based ionic liquids with sweetner anions. The concentration dependent molar conductance of these ionic liquids has been fitted to Mahiuddin and Ismail’s equation. To our surprise, the molar conductances of bisulfate-based aprotic ionic liquids are remarkably high, even though these ionic liquids possess lower ionicity.     

α-Glucosidase inhibitory activity of marine sponges collected in Mauritius waters

This report describes the use of α-glucosidase to evaluate the anti-diabetic potential of extracts from marine sponges collected in the Mauritius waters. Initial screening at 1.0 mg/mL of 141 extracts obtained from 47 sponge species revealed 10 extracts with inhibitory activity greater than 85%. Seven of the 10 extracts were further tested at 0.1 and 0.01 mg/mL and only the methanol extract of two sponges namely Acanthostylotella sp. (ASSM) and Echinodictyum pykei (EPM) showed inhibition activity greater than 60% at 0.1 mg/mL with an IC₅₀ value of 0.16 ± 0.02 and 0.04 ± 0.01 mg/mL, respectively, while being inactive at 0.01 mg/mL.     

Highly Selective and Sensitive Graphene Based Electrochemical Sensor for Quantification of Receptor Agonist Rizatriptan

A highly selective and sensitive electrochemical sensor has been developed by modification of a glassy carbon electrode (GCE) with graphene (GRP) for quantification of Rizatriptan. The significant increase of the peak current and the improvement of the oxidation peak potential indicate that the electrochemical sensor facilitates the electron transfer of Rizatriptan. The oxidation peak current was proportional to the Rizatriptan concentration in the range from 100 to 600 µg/mL with detection (LOD) and quantification limit (LOQ) of 36.52 and 121.73 µg/mL, respectively. The developed method was successfully employed for quantification of Rizatriptan in pharmaceutical formulations. The sensor shows great promise for simple, sensitive and quantitative detection of Rizatriptan.     

High-rate and high-density gas separation adsorbents and manufacturing method

High-rate and high-density gas separation adsorbents used in vacuum pressure swing adsorption (VPSA) processes are described. Agglomerated zeolite Li–LSX compositions made using colloidal silica binding agents and having improved nitrogen pore diffusivity compared to like compositions prepared with traditional clay binders, are also described. Preparation methods for the colloidal silica-bound adsorbents are described together with their characterization by mercury (Hg) porosimetry, scanning electron microscopy (SEM) and low dead-volume breakthrough testing, from which the pore diffusivity is obtained. In this article, we show how the location and dispersion of the colloidal silica binding agent within the agglomerated zeolite particle yields pore-architectures that resemble “state-of-the-art” binderless adsorbents. In addition, we use VPSA process simulations to show that the best process performance is achieved by the combination of high-rate and high-density adsorbent properties.     

Electrochemical determination of thermodynamic properties of DyRhO3 and phase relations in the system Dy-Rh-O

Thermodynamic properties of Dysprosium rhodite (DyRhO₃) are measured in the temperature range from 900 to 1,300 K using a solid-state electrochemical cell incorporating yttria-stabilized zirconia as the electrolyte. The standard Gibbs free energy of formation of DyRhO₃ with O-type perovskite structure from its components binary oxides, Dysprosia with C-rare earth structure and β-Rh₂O₃ with orthorhombic structure, can be represented by the equation: $$ {{{\varDelta G_{{f\left( {ox} \right)}}^o\left( {\pm 182} \right)}} \left/ {{{\mathrm{J} ~ \mathrm{mo}}{{\mathrm{l}}^{{ - 1}}}}} \right.} = - 52710 + 3.821\left( {{{T} \left/ {\mathrm{K}} \right.}} \right). $$ By using the thermodynamic data for DyRhO₃ from experiment and auxiliary data for other phases from the literature, the phase relations in the system Dy-Rh-O are computed. Thermodynamic data for intermetallic phases in the binary system Dy-Rh, required for constructing the chemical potential diagrams, are evaluated using calorimetric data available in the literature for three intermetallics and Miedema’s model, consistent with the phase diagram. The results are presented in the form of Gibbs triangle, oxygen potential–composition diagram, and three-dimensional chemical potential diagram at 1,273 K. Temperature–composition diagrams at constant oxygen partial pressures are also developed. The decomposition temperature of DyRhO₃ is 1,732 (±2.5) K in pure oxygen and 1,624 (±2.5) K and in air at standard pressure.     

Synthesis and thermal evaluation of novel mono- and bis-adamantylated resorcinol-based phthalonitrile resins with enhanced solubility

Journal of Thermal Analysis and Calorimetry - Phthalonitrile (PN) resins are high-temperature-resistant thermosetting polymers which find applications in military as well as aerospace owing to...