Aza-Ferrier rearrangement of glycals with amides promoted by molecular iodine

Amidoglycosidation of tri-O-acetyl-d-glucal with different N-nucleophiles such as t-butyl carbamate, N-benzyl carbamate, N-ethyl carbamate, tosyl amide, and mesyl amide has been achieved using an equimolar amount of molecular iodine under mild and neutral conditions to afford the corresponding N-glycosyl amides in good yields with a preferential α-anomeric selectivity. The use of iodine makes this method simple, convenient, and cost-effective. This is the first report on aza-Ferrier rearrangement using molecular iodine.     

Water‐Induced Formation,Characterization, and Photoluminescence of Carbon Nanotube‐Based Composites of Gadolinium(III) and Platinum(II) Dithiolenes

Understanding the nature of interactions of targeted drug‐delivery vehicles, such as functionalized carbon nanotubes (f‐CNTs) and their composites, with a cell or its organelles or DNA, where water is a major constituent, requires molecular‐level understanding of f‐CNTs with analogous chemical systems. The nature of interaction has not yet been explored within the scope of formation of giant aggregates by self‐assembly processes. Crystals of platinum(II) dithiolene [Pt(mnt)₂][PPh₄]₂ ( 1 ) and gadolinium(III) dithiolene [Gd(mnt)₃][PPh₄]₃ ( 2 ) (mnt=maleonitrile dithiolate) form nanospheres (diameter 88 nm) and nanoflowers (400–600 nm) in acetonitrile/water and DMF/water solvent mixtures, respectively. The formation of nanospheres or nanoflowers is proposed to be a water‐induced phenomenon. These nanospheres and nanoflowers interact with f‐CNTs by forming either spherical supramolecular assemblies ( 3 , diameter up to 45. 5 μm) in the case of platinum(II) dithiolene or composite flowers ( 4 ) with CNT buckling for gadolinium(III) dithiolene. Both nanostructures, ( 3 ) and ( 4 ), show emission upon excitation at a range of wavelengths (λ_ex=385–560 nm). The fluorescence emissions of the composite materials 3 and 4 are proposed to be due to separation of energy states of the nanospheres of 1 or the nanoflowers of 2 by the energy states of the f‐CNTs, leading to the possibility of new electronic transitions.     

Selective separation of some ecotoxic transition metal ions from aqueous solutions using immobilized macrocyclic material containing solid phase extraction system

A simple flow-based method was developed for the simultaneous separation of certain transition metal ions (Co, Ni, Cu, Zn, Cd) from aqueous systems, which ions show ecotoxic effects when present at elevated concentrations. A silica-gel-bonded macrocycle system, commonly known as molecular recognition technology (MRT) gel, was used for solid phase extraction (SPE) of the target analytes. The collection behavior of the MRT-SPE system was studied based on pH. Fortified deionized water samples containing 250 μg L⁻¹ of each of the elements were treated at the flow rate of 1 mL min⁻¹. The collected analytes were then eluted by 3 M HNO₃ and analyzed using inductively coupled plasma spectrometry. Detection limits of the proposed technique were in the range of 0.004–0.040 μg L⁻¹ for the studied metal ions. The validity of this separation technique was checked with spiked ‘real’ water samples, which produced satisfactory recoveries of 96–102%. The non-destructive nature and highly selective ion-extraction capability of the SPE material are the most important aspects of the proposed method and they are the main focus of this paper.      

Dangling thiyl radical: stabilized in [PPh4]2[(bdt)W(VI)(O)(μ-S)2Cu(I)(SC6H4S•)

The synthesis, crystal structure, and spectroscopic characterization of [PPh(4)](2)[(bdt)W(O)(S(2))Cu(SC(6)H(4)S(?))] (3; bdt = benzenedithiolate) relevant to the active site of carbon monoxide dehydrogenase are presented. Curiously, in 3, the copper(I) benzenemonothiolate subcenter possesses a dangling thiyl radical that is stabilized by a disulfido-bridged oxo tungsten dithiolene core. The benzenedithiolate ligand, which is generally bidentate in nature, acts as a bidentate and also as a monodentate in 3. The formation of an unusual dangling thiyl radical has been magnetically and spectroscopically identified and has been supported by the density functional theory level of calculation.     

Separation of lead from high matrix electroless nickel plating waste solution using an ion-selective immobilized macrocycle system

Separation of trace levels of lead from concentrated-matrix electroless nickel plating (ENP) waste solutions is required to meet the increasingly stringent environmental regulations. A solid phase extraction (SPE) system using a molecular recognition technology (MRT) gel was used for the selective separation of trace levels of lead (Pb) from the waste discharge of ENP operations, followed by subsequent analysis with inductively coupled plasma optical emission spectrometry (ICP-OES). Two SPE-MRTs, AnaLig® Pb-01 and AnaLig® Pb-02, packed in 3 mL polypropylene cartridges were used to treat the synthetic metal-waste solutions that were used to simulate the typical metal mixture in ENP bath waste. The fortified solutions contained 100-1000 μg L^− 1 of Pb in an HNO₃ matrix with pre-added Ni, Cu and other interfering elements (1000 mg L^− 1). After the sample treatment, the SPE-MRT cartridges were washed with water and 0.1 M nitric acid, followed by elution with 0.03 M EDTA. The matrix elements (e.g., Ni, Cu) were completely removed at the washing step, while the ‘captured’ Pb was quantitatively eluted, as determined by ICP-OES measurements. The detection limit of the proposed method was 2.6 μg L^− 1. ‘Real’ samples from commercial ENP operations were used to assess the validity of this method, and almost quantitative Pb recovery was observed. The excellent Pb selectivity of the SPE-MRT system indicates the potential of the proposed technique for trace-level Pb separation from the Pb-containing high matrix aqueous waste discharge.     

Design of highly nonlinear octagonal photonic crystal fiber with near-zero flattened dispersion at 1.31μm waveband

This paper presents a highly nonlinear octagonal photonic crystal fiber (HN-OPCF) with a Ge-doped core for dental optical coherence tomography (OCT) applications. The simulation results show that a nonlinear coefficient of 56.3W⁻¹ km⁻¹ and the flattened dispersion of less than −1:0 ps/(nm·km) are obtained in 75 nm waveband (1265–1340 nm). Owing to its high nonlinear coefficient and flattened dispersion, the HN-OPCF is expected to be suitable for supercontinuum generation, which is very important in OCT applications. The numerical simulation results demonstrate that the proposed HN-OPCF can generate wideband supercontinuum.     

Synthesis,characterization, biological screening and molecular docking of Zn(II) and Cu(II) complexes of 3,5-dichlorosalicylaldehyde-N4-cyclohexylthiosemicarbazone

A 3,5-dichlorosalicylaldehyde-N⁴-cyclohexylthiosemicarbazone (C₁₄H₁₆Cl₂N₃OS) and its complexes [Zn(dsct)(phen)]·DMF ( 1 ), [Zn(dsct)(bipy)]·DMF ( 2 ), [Cu(dsct)(bipy)]·DMF ( 3 ) (phen = 1,10-phenathroline, bipy = 2,2’bipyridine) were synthesized and characterized by CHN analysis, FT-IR, UV–vis and NMR spectra. The molecular structure of the thiosemicarbazone (H₂dsct) and its complexes have been resolved using single crystal XRD studies. In the complexes, thiosemicarbazone exist in the thioiminolate form and acts as dideprotonated tridentate ligand coordinating through phenolic oxygen, thioiminolate sulfur and azomethine nitrogen. The antibacterial activity of the prepared compounds were screened against Escherichia coli, Salmonella typhi, Enterobacter aerogenes, Shigella dysentriae, Bacillus cereus, Staphylococcus aureus. All the complexes showed activity against bacterial strains E.coli and Salmonella typhi. The thiosemicarbazone showed activity against three bacterial strains such as E. coli, Enterobacter aerogenes and Shigella dysentriae. Complex 2 showed very good antibacterial activity as compared to standard drug (Ampicillin) against the bacterial strain, Salmonella typhi. Finally, the thiosemicarbazone and its complexes have been used to accomplish molecular docking studies against an Epidermal Growth Factor Receptor (EGFR) and breast cancer mutant 3hb5-oxidoreductase to determine the most preferred mode of interaction. The results confirm that the complex [Cu (dsct)(bipy)]·DMF( 3 ) showed the highest docking score as compared to other complexes under study. The [Cu(dsct)(bipy)]·DMF( 3 ) complex was evaluated for their anticancer activities against breast cancer cell line (MCF-7) and normal L929 (Mouse Fibroblast) cell line. It was found that the compound showed an LC₅₀ of 6.25 μg/mL against breast cancer cell line (MCF-7).     

A numerical study of boundary layer flow of viscous incompressible fluid past an inclined stretching sheet and heat transfer using nonpolynomial spline method

In the present paper, we study the boundary layer flow of viscous incompressible fluid over an inclined stretching sheet with body force and heat transfer. Considering the stream function, we convert the boundary layer equation into nonlinear third-order ordinary differential equation together with appropriate boundary conditions in an infinite domain. The nonlinear boundary value problem has been linearized by using the quasilinearization technique. Then, we develop a nonpolynomial spline method, which is used to solve the flow problem. The convergence analysis of the method is also discussed. We study the velocity function for different angles of inclination and Froude number with the help of various graphs and tables. Then using these in heat convection flow, we obtain the expression for temperature field. Skin friction is also calculated. The various results have been given in tables. At last, we calculated the Nusselt number.     

Solar wind driven electrostatic instabilities with generalized (r,q) distribution function

Using Boltzmann–Vlasov kinetic model, a currentless ion acoustic instability driven by stream of solar wind plasma is studied in a non‐thermal distributed electrons and ions. The non‐thermal distribution considered here is the generalized distribution which has low energetic flat‐top and velocity power law tail at higher energies. The instability threshold is found to be affected and depends upon the spectral indices r and q . It is found that the growth rate increases with the decrease in the value of r and increase with q . Moreover, such kinetic instability has also been discussed for three species electron–ion–dust plasma using the generalized (r, q) distribution function. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust and excites electrostatic instabilities. The dispersion properties and growth rates for ion‐acoustic and dust‐acoustic mode are calculated analytically and plotted for different values of the spectral indices r and q .     

Deoxygenation and X-ray photoelectron studies on some quinoxalines and their N-oxides

Deoxygenation results of some quinoxaline dioxides with phosphorous trichloride are presented and compared with previous deoxygenations with other reagents. Differentiation between isomeric quinoxaline oxides using X-ray photoelectron spectroscopy is also discussed.