Structural studies of some body-centered cubic phases of mixed oxides involving Bi2O3: The structures of Bi25FeO40 and Bi38ZnO60

The structures of the compounds initially reported to be 7·Bi₂O₃·ZnO and 96·Bi₂O₃·4Fe₂O₃, have been determined by X ray methods. Three dimensional, absorption corrected diffractometer data were used and atomic parameters were refined by least-squares procedures. The structures are isomorphous, cubic witha = 10.194(3)and10.179(3)A?, respectively, and space group I23. Each Bi³⁺ ion is surrounded by five oxygen atoms that form an incomplete octahedral arrangement with BiO distances ranging from 2.07–2.60A?. The6s²inert electron pair completes the octahedron. The Bi³⁺ ions are vibrating anisotropically. Tetrahedral sites in the structures contain 61 and 46 electrons, respectively. These values are consistent with a statistical distribution of Zn²⁺ and Bi⁵⁺ ions or Fe³⁺ and Bi⁵⁺ ions on these sites. Molar ratios are derived that agree with the observed distributions of electron density and give rise to perfectly stoichiometric systems, devoid of cationic or anionic vacancies. The compositions studied correspond to Bi³⁺₂₄Bi⁵⁺Fe³⁺O₄₀ and Bi³⁺₃₆Bi⁵⁺₂ZnO₆₀ and they are optical enantiomorphs.It is proposed that a reduction in the percentage composition of Bi₂O₅ leads to metastable phases, in which all atomic positions remain fully occupied but some tetrahedral sites contain Bi³⁺ ions. The end product of the series is γ-Bi₂O₃ in which 50% of these sites contain Bi³⁺ and the remainder Bi⁵⁺ ions. We believe that γ-Bi₂O₃ is Bi³⁺₂₅Bi⁵⁺O₄₀.     

Cupric decamolybdodivanadophosphate. A coordination polymer heterogeneous catalyst for rapid, high conversion, high selectivity sulfoxidation using the ambient environment

A new type of coordination network polymer involving the redox-active polyanion, PV(2)Mo(10)O(40)(5)(-), and bridging -Cu(II)(OH(2))(4)- units, [[(Cu(II)(OH(2))(4))(3)(OH)]PV(2)Mo(10)O(40)](n)() (1), has been characterized by X-ray crystallography and several other methods. It is the first efficient heterogeneous (insoluble) catalyst for selective and rapid sulfoxidation using only the ambient environment (air at room temperature). Catalytic activity is enhanced by soluble nitrate in nontoxic perfluoropolyether (PFPE) media.     

beta-galactosidase assay using capillary electrophoresis laser-induced fluorescence detection and resorufin-beta-D-galactopyranoside as substrate

beta-Galactosidase was incubated for 60 min with the fluorogenic substrate resorufin-beta-D-galactopyranoside, which is converted by the action of the enzyme into resorufin and galactose. A 160 pL aliquot of reaction mixture was analyzed by capillary electrophoresis utilizing laser-induced fluorescence detection. Based on the detection of the resorufin formed, the limit of detection of beta-galactosidase was 1.5 x 10(-15) M or 900 molecules of enzyme in a 1 microL sample.     

An improved system for data acquisition and analysis for viscoelastic measurements of dilute macromolecular solutions with the modified birnboim-schrag multiple lumped resonator

A new system of data acquisition and analysis has been developed for the modified Birnboim-Schrag multiple lumped resonator apparatus which is used to measure the viscoelastic properties of long-chain macromolecules in dilute solution. The modifications to the original apparatus include improved temperature control and vibration isolation. The original theory has been reworked so that each resonance mode can be characterized by a greater number of data points. The entire data acquistion/processing system is automated and placed under computer control; a correlation for mode coupling is derived. The modifications result in improved precision in the measured viscoelastic moduli and increased instrumental reliability.     

A facile approach to architecturally defined nanoparticles via intramolecular chain collapse

A novel approach is presented for the controlled intramolecular collapse of linear polymer chains to give well-defined single-molecule nanoparticles whose structure is directly related to the original linear polymer. By employing a combination of living free radical polymerization and benzocyclobutene (BCB) chemistry, nanoparticles can be routinely prepared in multigram quantities with the size being accurately controlled by either the initial degree of polymerization of the linear chain or the level of incorporation of the BCB coupling groups. The latter also allows the cross-link density of the final nanoparticles to be manipulated. In analogy with dendritic macromolecules, a significant reduction of up to 75% in the hydrodynamic volume is observed on going from the starting random coil linear chains to the corresponding nanoparticles. The facile nature of the living free radical process also permits wide variation in monomer selection and functional group incorporation and allows novel macromolecular architectures to be prepared. Furthermore, the use of block copolymers functionalized with benzocyclobutene groups in only one of the blocks gives, after intramolecular collapse, a hybrid architecture in which a single linear polymer chain is attached to the globular nanoparticle.     

A ‘one pot’ microwave-mediated synthesis of the basic canthine skeleton: expedient access to unnatural β-carboline alkaloids

In a ‘one pot’ microwave reaction, an acyl hydrazide-tethered indole underwent a 3-component condensation to form a triazine, followed by an inverse-electron demand Diels-Alder reaction and subsequent chelotropic expulsion of N₂ to deliver novel, unnatural β-carboline alkaloids in good isolated yields.     

Response of poly(vinyl chloride) electrodes based on the neutral carrier 1,4,7,10-tetraoxacyclododecane

Ion-selective electrodes based on the neutral carrier, 12-crown-4, in a poly(vinyl chloride) matrix were found to respond ideally, or almost ideally, to potassium, sodium, barium, strontium, magnesium, cobalt(II), nickel(II) and aluminum ions. The electrode showed good selectivity for Al³⁺ over Co²⁺ and Mg²⁺, and for Co²⁺ over Mg²⁺. Little selectivity was found for the other ions tested.     

Sonoelectroanalysis: investigation of bismuth-film-modified glassy carbon electrodes

Bismuth-modified glassy carbon electrodes have been investigated for their suitability in sonoelectroanalysis. The stability of the bismuth film to the application of ultrasound was assessed via voltammetric and atomic force microscopy (AFM) studies which revealed little ablation at powers up to an intensity of 130 W cm^–2 delivered from a 25-kHz sonic horn. Furthermore, bismuth-film-modified glassy carbon electrodes were evaluated for the sonoelectroanalytical quantification of zinc and cadmium. Detection limits of 2×10^–7 M and 6×10^–9 M respectively were found after a 60-s deposition time via an acoustically assisted deposition protocol.     

Investigations into the Pd-catalysed cross-coupling of phenylacetylene with aryl chlorides: simple one-pot procedure and the effect of ZnCl2 co-catalysis

[PdCl(C6H3(OPPri2)2-2,6)] 1 catalyses the coupling of electron-rich, electron-neutral and electron-deficient aryl chlorides with phenylacetylene in the presence of ZnCl2 as cocatalyst to give the products in modest to excellent yields.