Catalysts for convenient aerobic alcohol oxidations in air: systematic ligand studies in Pd/pyridine systems

We report highly convenient Pd catalysts for the aerobic oxidation of alcohols, which are generated in situ by combining commercially available catalyst precursors. Systematic optimizations of the L- and X-type ligand environment and the employed additive allow the use of air as the sole oxidant without formation of Pd black. The resulting novel protocol provides quantitative yields of a broad variety of ketones and aldehydes.     

Alternating-current losses in two-layer superconducting cables consisting of second-generation superconductors coated by U-shaped ferromagnetic materials

Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by either a non-magnetic or strong ferromagnetic material having a U profile is numerically investigated. Computations are carried out through the finite-element method. The alternating-current losses do not increase significantly if the relative permeability of the coating is increased three orders of magnitude, provided that the current amplitude is less than half of the critical current in a superconducting wire. However, the losses are much higher for ferromagnetic coating if the amplitude of the applied current oscillating at 50 Hz is close to the critical current. The ferromagnetic coating is seen to accumulate the magnetic field lines normally on its surfaces, while the field lines are parallel to the long axes of the wires, leading to more significant flux penetration in the coated regions. This facilitates a uniform low-loss current flow in the uncoated regions of the wires. In contrast, coating with a non-magnetic material gives rise to a considerably smaller current flow in the uncoated regions, whereas the low-loss flow is maintained in the coated regions. Moreover, the current flows in opposite directions in the coated and uncoated regions, where the direction in each region is converse for the two materials.     

Monitoring the Instant Creation of a New Fluorescent Signal for Evaluation of DNA Conformation Based on Intercalation Complex

Here we report the monitoring the instant creation of a new fluorescent signal (FS) aroused from a positively charged water-soluble fluorogenic probe, ethidium bromide (EtBr) in the presence of a radical initiator, ammonium persulfate (APS) and an accelerator, tetraethylmetilendiamine (TEMED) for evaluation of deoxyribonucleic acid (DNA) conformation. The results revealed that the occurred FS (λ_ex?=?430 nm; λ_max?=?525 nm) is a reduced form of EtBr (λ_ex?=?480 nm; λ_max?=?617 nm) and it is completely distinct from hydroethidine (λ_ex?=?350 nm; λ_max?=?430 nm), which is two-electron reduced form of EtBr. It was noticed that EtBr was reduced to a new FS during the polymerization of N, N dimethyacrylamide (DMAA) too, at 25 °C in the presence of APS and TEMED or at 55 °C with only APS, and the rate of formation of FS was increased upon treatment time. The effect of nanoclays such as Laponite XLG® and Laponite XLS®, which provide a protective environment for DNA in nature, were also investigated through the reduction process of EtBr in the absence and presence of a water soluble monomer DMAA. We demonstrated that DNA conformation might be evaluated by monitoring FS effectuated during the reduction of EtBr in the presence of nanoclays having positively and negatively charged surfaces. Protective property of DNA against the formation of reduced product was elucidated by carrying out the polymerization at 55 °C. The results revealed that the monitoring of formation of FS in the presence of radical initiator could lead to elucidate the conformation of DNA upon formation of intercalator complex.     

Ruthenium(II) complexes derived from 2‐phenylthiazoline‐4‐carboxylic acid: structure and catalytic activity for transfer hydrogenation reaction

Piano‐stool ([(p‐cymene)Ru(thz)Cl], 2 ) and six‐coordinated ([Ru(thz)₂(PPh₃)₂], 3 ) ruthenium complexes derived from 2‐phenylthiazoline‐4‐carboxylic acid (Hthz, 1 ) were synthesized for the first time, and fully characterized using conventional methods. Also, the molecular structure of complex 3 was determined using X‐ray analysis. These complexes were evaluated as catalysts for transfer hydrogenation of carbonyl compounds in the presence of isopropyl alcohol and KO^tBu. Complex 2 was found to be more active than 3 in transfer hydrogenation. Copyright © 2016 John Wiley & Sons, Ltd.     

Pharmacological properties of dicyanidoaurate(I)-based complexes: characterization and single crystal X-ray analysis

The synthesis of three bimetallic cyanido complexes with edbea [2,2′-(ethylenedioxy)bis(ethylamine)] ligand is reported. [Ni^II(μ-edbea)₂{Au(μ-CN)₂}₂]_n (1), [{Cu^II(edbea)}₂{Au(μ-CN)₂}₄]_n (2) and [Cd^II(edbea)₂][Au(CN)₂]₂·H₂O (3) were fully characterized by elemental, infrared, XRD (3), ESI-MS and thermal analysis. The DNA/BSA binding properties of these complexes were evaluated by spectrophotometric titration, fluorometric ethidium bromide kinetics, and DNA electrophoresis studies and their partially minor groove binding mode between the base pairs of DNA and electrostatic interaction between the amino acid residues of BSA were explained. The complexes were tested for their pharmacological properties. These molecules had excellent in vitro antiproliferative activity and also exhibited a strong tumor inhibiting effect against HT29, HeLa, C6 and Vero cell lines. These complexes had metastatic features as they are able to reduce cell migration activity and suppress tumor growth in vitro. Analysis of the DNA topoisomerase I relaxing activity indicates that the complexes do not inhibit topoisomerase I which regulates the topological states of the DNA double helix during DNA processing reactions. The TUNEL and DNA laddering assay results indicated that these compounds may destroy cell maintenance by triggering apoptosis. Immunohistochemistry staining analysis demonstrated that these complexes significantly decreased the expression of Bcl-2 in HeLa and HT29 cells while increasing the expression of P53 levels. Overall, the potent antiproliferative activity, low cytotoxic effect, good solubility, and micro molar range dosage observed for these complexes emphasizes their potential as anticancer drug candidates.     

SPE and determination by FAAS of heavy metals using a new synthesized polymer resin in various water and dried vegetables samples

Firstly, poly[phenyl thiadiazole methacrylamide-co-divinylbenzene-co-2-acrylamido-2-methylpropane sulfonic acid] (PTMAAm-co-DVB-co-AMPS), a new polymer resin was synthesized. This polymer resin was characterized by elemental analyzer, X-ray diffractometer, scanning electron microscope (SEM) and IR spectrometer. The glass column packed with the synthesized polymer resin was used for solid phase extraction (SPE). At the same time, the analytes were separated and preconcentrated from various water, dried vegetables samples and standard reference material (CRM) with SPE and determined by flame atomic absorption spectrometer (FAAS). The experimental conditions of this method such as pH, flow rates of sample, flow rates of eluent, type / concentration / volume of eluent, sample volume and matrix ions were examined. The limits of detection (µg L^?1) were calculated (3s) 0.9 for Mn(II), 1.4 for Cd(II), Co(II) and Zn(II), 1.5 for Cr(III), 2.2. for Cu(II), 1.9 for Pb(II),1.5 for Ni(II) and 1.9 for Fe(III) (n = 21). The low relative standard deviation, ≤ 2% (n = 11) and preconcentration factor as 75 for analytes were obtained.     

Aluminium fractionation using cation exchange: comparison of results obtained after fractionation in the field and in the laboratory

Dissolved aluminium was fractionated in the field and the laboratory using a cation-exchange method. Although absolute differences between results obtained from field and laboratory fractionations were generally small, relative differences, expressed as the ratio between labile aluminium determined after laboratory fractionation (Al_ll) and that obtained after field fractionation (Al_lf) could be large. The differences found were not statistically significant, although this may simply reflect the spread in the results. Al_ll/Al_lf had no apparent relationship with the temperature difference between the field and the lab. Although some significant correlations were found between Al_ll/Al_lf and H⁺, no significant correlations were found with the equivalent relative difference in {H⁺} between the lab and the field; nor was any significant correlation found with dissolved organic carbon.     

On-line preconcentration and determination of Au(III) in various environmental/industrial samples by flame atomic absorption spectrometry

A rapid and simple on-line method is described for the determination of Au(III) in various samples. The method is based on the sorption of gold(III) on Lewatit MonoPlus TP207 chelating resin including the iminodiacetate group, which is used as sorbent material and packed in a minicolumn. The chemical variables such as the pH of the sample solution, eluent type, interfering ions and concentrations of reagents, and instrumental variables such as sample loading volume, reagents flow rates, and tubing length, which affect the efficiency of the method were studied and optimised. Au(III) was sorbed on the chelating resin, from which it could be eluted with 3 mol L^?1 HCl, and then introduced directly to the nebuliser-burner system of FAAS. The limit of detection of the method was 0.2 µg L^?1 while the relative standard deviation was <4.0% for 20 µg L^?1 Au(III) concentration. The preconcentration factor was found to be 106 while the optimised sample volume was 15.3 mL. The accuracy of the method was verified by analysing the certified reference material. The developed method was applied successfully for the determination of gold in different samples with satisfactory results.