Addition of primary phosphines to the unsaturated triosmium cluster [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}]: Synthesis of triosmium clusters bearing dppm, phosphide and phosphinidene ligands via P-H bond activation

Treatment of the electronically unsaturated cluster [(μ-H)Os₃(CO)₈{Ph₂PCH₂P(Ph)C₆H₄}] (1) with primary phosphines PPhH₂ and PCyH₂ gives the phosphido bridged compounds [(μ-H)Os₃(CO)₈(μ-PPhH)(μ-dppm)] (2) and [(μ-H)Os₃(CO)₈(μ-PCyH)(μ-dppm)] (3), respectively, by P-H bond activation of the phosphines and demetallation of the phenyl ring of the diphosphine ligand. Thermolysis of 2 and 3 in refluxing octane at 128 °C results in the formation of the phosphinidene compounds [(μ-H)₂Os₃(CO)₇(μ₃-PPh)(μ-dppm)] (4) and [(μ-H)₂Os₃(CO)₇(μ₃-PCy)(μ-dppm)] (5), respectively, by further P-H bond cleavage of the phosphido groups. All the compounds have been characterized by infrared, ¹H NMR, ³¹P{¹H} NMR and mass spectroscopic data together with single-crystal X-ray diffraction studies for 4. Compound 4 consists of a triangular cluster of osmium atoms with a symmetrically capped phosphinidene ligand and a bridging dppm ligand.     

A new practical method for the synthesis of unsymmetrical ureas via high-pressure-promoted condensation of 2,2,2-trichloroethyl carbamates (Troc-carbamates) with amines

A new practical method for the synthesis of unsymmetrical ureas was achieved by condensation between 2,2,2-trichloroethyl carbamates (Troc-carbamates) and primary or secondary amines under high-pressure conditions.     

Membrane-based receptor affinity chromatography.

Membrane-based receptor affinity chromatography (MRAC), which utilizes the molecular recognition between an immobilized receptor and its soluble protein ligand, has been developed for the purification of human interleukin-2 and related biomolecules. The multi-purpose affinity membrane used in this study consisted of a soluble form of interleukin-2 receptor (IL-2R) chemically bonded to hollow-fiber membranes in an oriented fashion. A model system involving anti-Tac-H (a humanized monoclonal antibody to IL-2R) was used to study the important factors influencing the performance of MRAC, including support morphology, mass transfer rate and adsorption kinetics. All three are shown to be highly efficient. MRAC has been successfully applied to the purification of anti-Tac-H, recombinant human interleukin-2 (rIL-2) and interleukin 2-Pseudomonas exotoxin fusion protein (IL2-PE40). Overall, MRAC was found to be a viable, scalable and extremely productive affinity purification method.     

Determination of binding constants between the antibiotic ristocetin A and D-Ala-D-Ala terminus peptides by affinity capillary electrophoresis

Summary Binding constants between the antibiotic ristocetin A (Rist A) and D-Ala-D-Ala terminus peptides were determined using affinity capillary electrophoresis (ACE). In these experiments two techniques are used to obtain binding constants. In the first, a plug of Rist A and non-interacting standards are injected and electrophoresed. Analysis of the change in the relative migration time ratio (RMTR) of Rist, relative to the non-interacting standards, as a function of the concentration of peptide, yields a value for the binding constant (Kb). In the second, samples of peptide and standards are injected and electrophoresed in increasing concentrations of Rist A in the running buffer. Analysis using theRMTR yields aK _b. The findings described here demonstrate the advantage of using ACE for estimating binding parameters between antibiotics and ligands.     

Chiral induction in a ribose-decorated metallostar through intrinsic and interionic diastereomeric interactions

A ribose-functionalized bpy ligand has been prepared and shown to give modest diastereomeric excesses of Lambda-[FeL(3)](2+) complexes; interconversion of Delta and Lambda cations is relatively fast, and in CHCl(3), the favored complexes with Delta- or Lambda-TRISPHAT counterions are homochiral, (Delta(+)Delta(-)) or (Lambda(+)Lambda(-)). In the case of the Delta-TRISPHAT salt, a single diastereomer is observed (de > or = 96%).     

Improving the Photocatalytic Activity of Modified Anatase TiO2 with Different Concentrations of Aluminum under Visible Light: Mechanistic Survey

Visible light‐driven Al‐doped TiO₂ with different aluminum contents (2, 5 and 10 mol%) were synthesized via a facile sol–gel method. Fourier transform infrared (FTIR), UV‐visible diffuse reflectance, energy dispersive X‐ray (EDX) spectroscopy as well as X‐ray diffraction (XRD), X‐ray fluorescence (XRF) and scanning electron microscopy (SEM) methods were used for the characterization of the obtained nanoparticles. The photocatalytic performance of the samples was evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. The yield of the degradation RhB was estimated to be 71%, 89%, 65% and 56%, for the bare TiO₂, 2%, 5% and 10% Al‐doped TiO₂, respectively. It was found that 2 mol% of Al‐doped TiO₂ shows the best photocatalytic performance. In low concentration of dopant, separation of photogenerated electron–hole pairs promoted, and subsequently, the degradation efficiency increased. It was proposed that the degradation of RhB by 2 mol% Al‐doped TiO₂ photocatalyst follows both N‐deethylation and chromophore cleavage mechanisms, while the N‐deethylation still predominated over cleavage of dye chromophore structure. The key role of hydroxyl radicals in RhB degradation was verified by the effects of scavengers. In addition, the photocatalyst can be reused for three runs without any significant loss of its catalytic activity.     

Effect of metal permittivity on resonant properties of terahertz metamaterials

We investigate the effect of metal permittivity on resonant transmission of metamaterials by terahertz time-domain spectroscopy. Our experimental results on double split-ring resonators made from different metals confirm the recent numerical simulations [Phys. Rev. E 65, 036622 (2002)] that metamaterials exhibit permittivity-dependent resonant properties. In the terahertz regime, the measured inductive-capacitive resonance is found to strengthen with a higher ratio of the real to the imaginary parts of metal permittivity, and this remains consistent at various metal thicknesses. Furthermore, we found that metamaterials made even from a generally poor metal become highly resonant owing to a drastic increase in the value of the permittivity at terahertz frequencies.     

Solutions of Heat-Like and Wave-Like Equations with Variable Coefficients by Means of the Homotopy Analysis Method

We employ the homotopy analysis method （HAM） to obtain approximate analytical solutions to the heat-like and wave-like equations. The HAM contains the auxiliary parameter h, which provides a convenient way of controlling the convergence region of series solutions. The analysis is accompanied by several linear and nonlinear heat-like and wave-like equations with initial boundary value problems. The results obtained prove that HAM is very effective and simple with less error than the Adomian decomposition method and the variational iteration method.     

Prescribing a multistage analytical method to a prey-predator dynamical system

This article discusses the effectiveness of a fresh analytical method in solving a prey-predator problem, which is described as a system of two nonlinear ordinary differential equations. The method of interest is the multistage variational iteration method (MVIM), which provides a slight modification of the classical variational iteration method (VIM). We shall compare solutions of the classical VIM along with MVIM and match them against the conventional numerical method, Runge-Kutta (RK4) (fourth-order).     

Na4ReN3, das erste Alkalimetall‐Nitridorhenat(V)

Na₄ReN₃, the First Alkali Metal Nitridorhenate(V) Rhenium powder reacts in a mixture with NaNH₂ in autoclaves at 773 K to orange colored crystals embedded in a matrix of sodium metal. After extracting the sodium metal with liquid ammonia single crystals were seperated. The structure was solved by X‐ray single crystal methods and for the evaluation of the correct space group by optical SHG experiments: spacegroup Cc (No. 9), Z = 4, a = 10.903(2) Å, b = 6.022(1) Å, c = 8.944(2) Å, β = 115.57(3)°. The structure contains trigonal pyramidal anions ReN₃^4–, which are embedded in three‐dimensionally linked, fourfold capped cubes of 12 Na.