Reactions of Phosphorus-Phosphorus Bonded Mixed-Valence Diphosphorus Compounds

Abstract

A novel type of mixed valence diphosphorus compound, involving the grouping Cl-P(-)-P(+)-NEt₂, with the two phosphorus atoms doubly bridged by N.N'-dimethylurea, has become readily available. Reactions of this type of compound have furnished a variety of new structural elements, involving two directly bonded phosphorus atoms in two different oxidation states and / or coordination numbers.     

Linear perturbation amplification in self-similar ablation flows of inertial confinement fusion

Exact similarity solutions for inviscid compressible ablative flows in slab symmetry with nonlinear heat conduction are proposed for studying unsteadiness and compressibility effects on the hydrodynamic stability of ablation fronts relevant to inertial confinement fusion. Both the similarity solutions and their linear perturbations are numerically computed with a dynamical multidomain Chebyshev pseudospectral method. Herewith the first analysis of laser-imprinting based on a dynamic solution is presented, showing that maximum perturbation amplification occurs for a laser-intensity modulation of zero transverse wave number, with growth dominated by the mean flow stretching.     

Local Observation of Field Polarity Dependent Flux Pinning by Magnetic Dipoles

A scanning Hall probe microscope is used to study flux pinning in a thin superconducting Pb film covering a square array of single-domain Co dots with in-plane magnetization. We show that single flux quanta of opposite sign thread the superconducting film below T(c) at the opposite poles of these dipoles. Depending on the polarity of the applied field, flux lines are attracted to a specific pole of the dipoles, due to the direct interaction with the vortexlike structures induced by the local stray field.     

An Approach for Extracting Small-Signal Equivalent Circuit of Double Heterojunction δ-Doped PHEMTs for Millimeter Wave Applications

Pseudomorphic high electron mobility transistors (PHEMTs) are very important in millimeterwave application. A simple and accurate method for extracting small-signal equivalent curcuit for Double Heterojunction -doped PHEMT valid up to 40GHz is presented. First, the parasitic parameters of the equivalent circuit are determined using pinch off PHEMT except for PAD capacitances. The initial intrinsic elements are then determined by conventional analytical method. Advanced Design System is then used to optimize the whole model parameters with very small dispersion of initial values. Good agreement is obtained between simulation results and measured results for a 0.25um DH PHEMT.     

The linear combination of localized orbitals methods (LCLO) for polymers

The application of the Linear Combination of Localized Orbitals (LCLO) method to the band structure of polyethylene in the T, TG, TGTG' and G conformations is reported. The method uses full ab initio results on molecules to construct Fock matrix elements and deduce the energy bands. The main advantages of the technique are the low cost and the simplicity. Results are compared with those obtained from published ab initio and empirical calculations.Chargé de Recherches of the Fonds National Belge de la Recherche Scientifique.Titulaire d'une bourse de spécialisation I.R.S.I.A.     

Stability of divalent europium in an ionic liquid: spectroscopic investigations in 1-methyl-3-butylimidazolium hexafluorophosphate

In this work, devoted to 1-methyl-3-butylimidazolium hexafluorophosphate ionic liquid (BumimPF(6)), the importance of the purity of the solvent for spectroscopic investigations is highlighted. Results from small angle X-ray scattering indicate that the pure solvent exhibits a local organization. Europium(II), which appears to be unusually stable in BumimPF(6), is characterized by spectroscopic techniques (absorption, luminescence). Solvation of Eu(II) in BumimPF(6) and complexation effects in the presence of the crown ether 15C5 solubilized in the ionic liquid are discussed.     

Order-disorder in the super-sodalite Zn3Al6(PO4)12, 4tren, 17H2O (MIL-74): a combined XRD-NMR assessment

A new mixed zinc-aluminum phosphate Zn(3)Al(6)(PO(4))(12), 4tren, 17H(2)O (MIL-74) has been hydrothermally synthesized with the tris(2-aminoethyl)amine (tren) as a structure-directing agent (453 K, 36 h, autogenous pressure). The solid was characterized by a nonclassical method combining single-crystal X-ray diffraction and several solid-state NMR experiments, RFDR, C7 double quantum ((31)P), and 3QMAS ((27)Al). Its crystal structure is cubic, a = 16.7942(1) A, but the choice of the space group does not follow usual routes of structure determination, due to some "disorder" between Zn and Al. It can be assigned as well to I-43m or to P-43n. The open-framework is built up from an enneameric unit (T = Zn, Al) containing five TO(4) and four PO(4) tetrahedra (one of the P-O bonds is terminal). A central TO(4) tetrahedral unit shares all of the corners with four phosphates groups. Two phosphate groups are connected to two other peripheral TO(4) units. It results in the formation of a "pseudo" planar building block T(5)P(4) consisting of four square 4-rings. The connection of the T(5)P(4) units generates a three-dimensional framework, which defines a super-sodalite topology. The resulting cavities (diameter of 10 A) are bound by 12-ring windows in which are located the tren species in interaction with the phosphate groups (mainly terminal P-O bonds) through hydrogen bonds. A cluster of 17 water molecules occupies the center of the super-sodalite cage. The cationic (Zn, Al) occupancy is discussed for this specific topology.     

Carbon-13 NMR study of some isomeric n-nitroindazole derivatives

The ¹³C NMR spectra of 1,5- and 2,x-dinitroindazoles “x=4-7” and 3-bromo-1,x-dinitroindazoles are recorded and discussed. The data on he 2,x-dinitroindazoles confirm our previous structurea assignment based on ¹H NMR spectroscopy. The ¹³C NMR spectra established that in the novel 3-bromo-1,x-dinitroindazoles the N-nitro group is attached at N-1.