Magnetic ordering in gadolinium aluminate,GdAlO3

An analysis of Magneto-Electric Susceptibility, Magnetic Susceptibility and X-ray results has shown that the direction of sub lattice alinement in the antiferromagnetically ordered state of GdAlO₃ corresponds to the orthorhombic a-axis. This result is contrary to the previous analysis which favoured the b-axis.     

Photochemically knocking out glutamate receptors in vivo

AMPA (alpha-amino-3-hydroxy-5-methyl-4-isooxazole) receptors, a major subtype of ionotropic glutamate receptors (iGluRs), mediate the majority of the fast communication between neurons, and the activity-dependent trafficking of AMPA receptors at synapses plays a role in mammalian learning and memory. Here we describe the design, synthesis, and evaluation of a photoreactive AMPA receptor antagonist that provides a means of "knocking out" AMPA receptors present on the surface of cells. The antagonist, 6-azido-7-nitro-1,4-dihydroquinoxaline-2,3-dione (ANQX), was designed by introducing a photoreactive azido group onto a quinoxalinedione inhibitor scaffold. Computational docking of ANQX to the AMPA receptor ligand-binding core predicted efficient binding to AMPA receptors. Glutamate-evoked currents were reversibly blocked at micromolar ANQX concentrations prior to photolysis and irreversibly blocked following photolysis. ANQX provides a means of directly evaluating the trafficking of native AMPA receptors with unparalleled spatiotemporal resolution.     

Reaction of a cyclic triphosphenium ion with triflic acid and SnX2 (X = Br or Cl): A 31P NMR study

The di‐ium dication formed by triflic acid protonation of the cyclic triphosphenium ion derived from 1,4‐bis‐diphenylphosphinobutane, (dppb), and P₃(X = Br or Cl) decomposes via an acyclic dication bearing a  PHX group; this intermediate is reduced by SnX₂ in the presence of HX to yield a dication with a  PH₂ primary phosphane terminal group, which is comparatively stable. The structure of this species has been unequivocally confirmed by ³¹P solution‐state NMR spectroscopy. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:609–612, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20302     

Flow synthesis using gaseous ammonia in a Teflon AF-2400 tube-in-tube reactor: Paal-Knorr pyrrole formation and gas concentration measurement by inline flow titration

Using a simple and accessible Teflon AF-2400 based tube-in-tube reactor, a series of pyrroles were synthesised in flow using the Paal-Knorr reaction of 1,4-diketones with gaseous ammonia. An inline flow titration technique allowed measurement of the ammonia concentration and its relationship to residence time and temperature.     

A more reactive trigonal-bipyramidal high-spin oxoiron(IV) complex with a cis-labile site

The trigonal-bipyramidal high-spin (S = 2) oxoiron(IV) complex [Fe(IV)(O)(TMG(2)dien)(CH(3)CN)](2+) (7) was synthesized and spectroscopically characterized. Substitution of the CH(3)CN ligand by anions, demonstrated here for X = N(3)(-) and Cl(-), yielded additional S = 2 oxoiron(IV) complexes of general formulation [Fe(IV)(O)(TMG(2)dien)(X)](+) (7-X). The reduced steric bulk of 7 relative to the published S = 2 complex [Fe(IV)(O)(TMG(3)tren)](2+) (2) was reflected by enhanced rates of intermolecular substrate oxidation.     

Localized π-orbitals,pauling bond orders,and the origin of aromatic stability

Energy-localized -orbitals are obtained for twenty-one cata- and peri-condensed hydrocarbons in the Hückel approximation. Coefficients for the localized orbitals are given. Four different orbital types are found to occur. Rules are given relating the localized orbitals to Pauling bond orders and an interpretation of the theoretical resonance energy is offered.

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Zusammenfassung Energielokalisierte -Elektronenorbitale für 21 kata- und perikondensierte Kohlenwasserstoffe werden im Rahmen der Hückelschen Näherung angegeben. Es zeigt sich, daß vier verschiedene Arten von ihnen auftreten und daß sich Regeln für ihre Beziehung zu den Paulingschen Bindungsordnungen finden lassen. Die lokalisierte Formulierung erlaubt eine einleuchtende Interpretation der theoretischen Resonanzenergie.

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Résumé Obtention d'orbitales de Hückel localisées selon le critère d'énergie pour 21 hydrocarbures cataet peri-condensés. Donnée des coefficients des orbitales localisées. On trouve quatre types d'orbitales. On donne des règles reliant les orbitales localisées aux indices de liaison de Pauling et une interprétation de l'énergie de résonance théorique est proposée.

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Work performed in the Ames Laboratory of the U.S. Atomic Energy Commision, Contribution No. 2924.     

USE OF TRIS (2,2'-BIPYRIDINE) RUTHENIUM(II) DICATION IN A NOVEL METHOD FOR THE DETERMINATION OF SINGLET OXYGEN REACTION RATES: APPLICATION TO STUDIES OF GELATIN

Abstract— A novel method for the determination of singlet oxygen reaction rate constants is described and applied to studies of cyclohexadiene in methanol and gelatins in H₂O and D₂O. The technique uses tris (2,2'-bipyridine) ruthenium(II) dication (Ru(bipy)₃₂₊) as both singlet oxygen sensitizer and in situ oxygen concentration monitor during irradiation of sealed samples. Because of the high efficiency with which the luminescence of Ru(bipy)₃2+* can be detected, and the fact that emission lifetimes are used, the method offers some advantages over those previously described. The advantages and disadvantages of the method are discussed. A rate constant of 2.1 (±0.3) x 10⁶ mol^-1 dm³ s^-1 has been determined for the reaction of ¹O₂ with cyclohexadiene in methanol. For two different photographic gelatins the sums of reaction and quenching rate constants are 2.0 (±0.4) x 10⁶ and 3.1 (±2.0) x 10⁵ mol^-1 dm³ s^-1; for swine skin gelatin this value is 3.9 (±2.4) × 10⁵ mol^-1 dm³ s^-1. Chemical reaction, rather than physical quenching, is the dominant reaction route for gelatins and ¹O₂.