2-(Trimethylsilyl)ethanesulfonyl amide as a new ammonia equivalent for palladium-catalyzed amination of aryl halides

2-(Trimethylsilyl)ethanesulfonyl amide (SES-NH₂) is an ammonia equivalent for the palladium-catalyzed amination of aryl bromides and aryl chlorides. Using these amine derivatives, it has been observed that anilines and anilines with sensitive functional groups can be readily prepared.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

A primal-dual approximation algorithm for a two depot heterogeneous traveling salesman problem

Surveillance applications require a collection of heterogeneous vehicles to visit a set of targets. We consider a fundamental routing problem that arises in these applications involving two vehicles. Specifically, we consider a routing problem where there are two heterogeneous vehicles that start from distinct initial locations and a set of targets. The objective is to find a tour for each vehicle such that each of the targets is visited at least once by a vehicle and the sum of the distances traveled by the vehicles is minimal. We consider an important special case of this routing problem where the travel costs satisfy the triangle inequality and the following monotonicity property: the first vehicle’s cost of traveling between any two targets is at most equal to the second vehicle’s cost of traveling between the same targets. We present a primal-dual algorithm for this case that provides an approximation ratio of 2.     

Etodolac:β-cyclodextrin inclusion complex as a novel fluorescent chemosensor probe for Ba2+

The inclusion complex of etodolac (ETD) with β-CD was investigated by UV-visible and fluorescence spectroscopy. The chemosensory ability of ETD:β-CD complex for various metal cations was investigated thoroughly, and we found that the emission of the complex showed a drastic increase in the intensity for Ba²⁺. Competitive experiments of ETD:β-CD complex with Ba²⁺ showed that no significant variation was found in the fluorescence intensity of the ETD:β-CD/Ba²⁺ complex upon adding other cations, such as Na⁺, Ag⁺, Hg²⁺, Cd²⁺, Al³⁺, Cr³⁺, Fe³⁺, Se⁴⁺, and Ti⁴⁺. The linearity range, limit of detection (LOD), and limit of quantitation (LOQ) were determined from the selectivity and sensitivity studies.     

An improved HPLC method with the aid of a chemometric protocol: simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations

Statistical experimental design and Derringer's desirability function were applied to develop an improved RP-HPLC method for the simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations. Four independent factors were considered: acetonitrile content in the mobile phase; buffer pH; buffer concentration; and flow rate. The preliminary screening step was carried out, according to a 2(4-1) fractional factorial design, to identify the significant factors affecting the analysis time response. Then central composite design was applied for a response surface study, in order to examine in depth the effects of the most important factors. Subsequently, Derringer's desirability function was employed to simultaneously optimize the six responses: retention factor of first peak; two resolutions; and three retention times, each having a different target. This procedure allowed deduction of two separate optimum conditions, intended for the analysis of quality control and plasma samples, within the experimental domain. The predicted optimum for the quality control samples was: methanol-acetonitrile-15 mM K(2)HPO(4) buffer (pH 5.33) (10:42.08:47.92, v/v/v) as the mobile phase and 1.12 mL/min as the flow rate. The method using this optimized condition showed higher sensitivity and shorter analysis time than the previously published reports. The optimized assay condition was validated according to International Conference on Harmonization guidelines.     

Multinuclear solid-state NMR spectroscopy of doped lanthanum fluoride nanoparticles

Multinuclear solid-state NMR spectroscopy and powder X-ray diffraction (XRD) experiments are applied to comprehensively characterize a series of pure and lanthanide-doped LaF3 nanoparticles (NPs) that are capped with di-n-octadectyldithiophosphate ligands (Ln3+ = diamagnetic Y3+ and Sc3+ and paramagnetic Yb3+ ions), as well as correlated bulk microcrystalline materials (LaF3, YF3, and ScF3). Solid-state 139La and 19F NMR spectroscopy of bulk LaF3 and the LaF3 NPs reveal that the inorganic core of the NP retains the LaF3 structure at the molecular level; however, inhomogeneous broadening of the NMR powder patterns arises from distributions of 139La and 19F NMR interactions, confirming a gradual change in the La and F site environments from the NP core to the surface. 139La and 19F NMR experiments also indicate that low levels (5 and 10 mol %) of Ln3+ doping do not significantly change the LaF3 structure in the NP core. Similar doping levels of paramagnetic Yb3+ ions severely broaden 19F resonances, but only marginally effect 139La powder patterns, suggesting that the dopant ions are uniformly distributed throughout the NP core and occupy vacant La sites. Measurements of 139La T1 and T2 relaxation constants are seen to vary between the bulk material and NPs and between samples with diamagnetic and paramagnetic dopants. 45Sc NMR experiments confirm that the dopants are integrated into the La sites of the LaF3 core. Solid-state 1H and 31P magic-angle spinning (MAS) NMR spectra aid in probing the nature of the capping ligands and their interactions at the NP surface. 31P cross-polarization (CP)/MAS NMR experiments identify not only the dithiophosphate head groups but also thiophosphate and phosphate species which may form during NP synthesis. Finally, 19F-31P CP/MAS and 1H MAS experiments confirm that ligands are coordinated to the NP surface.     

Study on δ‐Form Complex in a Syndiotactic Polystyrene/Organic Molecules System, 1. Preferential Complexing Behavior of Xylene Isomers

To investigate the preferential complexing behavior of isomeric xylenes, syndiotactic polystyrene (sPS) membranes are prepared using varying compositions of m‐ and p‐xylene. Complex formation between sPS and the xylenes was studied by means of thermogravimetric and FT‐IR analyses to determine the exact amounts of solvent molecules present per styrene repeating unit. A preferential complexing ability of p‐xylene was revealed due to its favorable interaction with sPS.     

Ultrasound assisted enhancement in natural dye extraction from beetroot for industrial applications and natural dyeing of leather

There is a growing demand for eco-friendly/non-toxic colorants, specifically for health sensitive applications such as coloration of food and dyeing of child textile/leather garments. Recently, dyes derived from natural sources for these applications have emerged as an important alternative to potentially harmful synthetic dyes and pose need for suitable effective extraction methodologies. The present paper focus on the influence of process parameters for ultrasound assisted leaching of coloring matter from plant materials. In the present work, extraction of natural dye from beetroot using ultrasound has been studied and compared with static/magnetic stirring as a control process at 45 °C. The influence of process parameters on the extraction efficiency such as ultrasonic output power, time, pulse mode, effect of solvent system and amount of beetroot has been studied. The use of ultrasound is found to have significant improvement in the extraction efficiency of colorant obtained from beetroot. Based on the experiments it has been found that a mixture of 1:1 ethanol–water with 80 W ultrasonic power for 3 h contact time provided better yield and extraction efficiency. Pulse mode operation may be useful in reducing electrical energy consumption in the extraction process. The effect of the amount of beetroot used in relation to extraction efficiency has also been studied. Two-stage extraction has been studied and found to be beneficial for improving the yield for higher amounts of beetroot. Significant 8% enhancement in % yield of colorant has been achieved with ultrasound, 80 W as compared to MS process both using 1:1 ethanol–water. The coloring ability of extracted beet dye has been tested on substrates such as leather and paper and found to be suitable for dyeing. Ultrasound is also found to be beneficial in natural dyeing of leather with improved rate of exhaustion. Both the dyed substrates have better color values for ultrasonic beet extract as inferred from reflectance measurement. Therefore, the present study clearly offers efficient extraction methodology from natural dye resources such as beetroot with ultrasound even dispensing with external heating. Thereby, also making eco-friendly non-toxic dyeing of fibrous substances a potential viable option.     

A new characterization of nonnegativity of Moore-Penrose inverses of Gram operators

In this article, a new characterization for the nonnegativity of Moore–Penrose inverses of Gram operators over Hilbert spaces is presented. The main result generalizes the existing result for invertible Gram operators.      

Synthesis, structure, and characterization of novel two- and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O

Two new vanadates, Ba(2.5)(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O, have been synthesized by hydrothermal methods using BaCO3, Ba(OH)2.H2O, La(NO3)3.6H2O, V2O5, TeO2, and H2SeO3 as reagents. The structures were determined by single-crystal X-ray diffraction. Ba(2.5)(VO2)3(SeO3)4.H2O exhibits a two-dimensional layered structure consisting of VO(5) square pyramids and SeO3 polyhedra, whereas La(VO2)3(TeO6).3H2O has a three-dimensional framework structure composed of VO(4) tetrahedra and TeO6 octahedra. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis are also presented. Crystal data: Ba(2.5)(VO2)3(SeO3)4.H2O, trigonal, space group P (No. 147) with a = b = 12.8279(15) A, c = 7.2631(9) A, V = 1035.1(2) A(3), and Z = 2; La(VO2)3(TeO6).3H2O, trigonal, space group R3c (No. 161) with a = b = 9.4577(16) A, c = 23.455(7) A, V = 1816.9(7) A3, and Z = 6.