A carboxylate-based dinuclear dysprosium(III) cluster exhibiting slow magnetic relaxation behaviour

Herein, we present a carboxylate-based dinuclear dysprosium compound, namely [Dy(2)L(6)(MeOH)(2)(H(2)O)(2)] (LH = n-butyric acid) from the reaction of Dy(NO(3))(3)·xH(2)O with n-butyric acid and triethylamine in MeOH solvent. The single crystal X-ray diffraction analysis demonstrate that a total of six monocarboxylate ligands formed this dimeric compound by carboxylate bridging along with coordination from solvent molecules (water and methanol). Each Dy(III) ion is coordinated by nine donor atoms forming a mono-capped antiprismatic coordination environment. Alternating current (AC) magnetic measurements show a frequency dependence of the out-of-phase magnetic susceptibilities (χ') indicating a slow relaxation behaviour of the magnetization.     

Chemical routes to nanocrystalline thermoelectrically relevant AgPb(m)SbTe(m+2) materials

A direct synthesis of nanoparticles of the thermoelectrically relevant AgPbmSbTem+2 materials (m = 0, 1, 2) was accomplished in reverse micelles. The procedure offers several distinct advantages and opens the field for experimentation of thermoelectric properties for nanoparticle-derived materials.     

The potential for intrinsic bioremediation of BTEX hydrocarbons in soil/ground water contaminated with gas condensate

Applied Biochemistry and Biotechnology - Gas condensate liquids contaminate soil and ground water at two gas production sites in the Denver Basin, CO. A detailed field study was carried out at...     

DMAP-promoted cascade C–S/C–N bonds formation approach to 1,3-thiazolidin-4-ones via annulation of β-ketothioamides with α-halocarboxylic acids at room temperature

An operationally simple and efficient one-pot straightforward method for the construction of 1,3-thiazolidin-4-ones has been developed by cyclocondensation of β-ketothioamides and an in situ generated acid anhydride from α-halocarboxylic acid in the presence of DCC at room temperature. The attractive features of this strategy include metal-free mild reaction conditions, short reaction time, and efficacy of forming consecutive C–S and C–N bonds and one ring in a single synthetic operation. Noteworthy, a Z-stereochemistry was observed for the exocyclic α-oxoketene moiety at 2-position of 1,3-thiazolidine ring.     

Pd-catalyzed atom-economic couplings of triarylbismuth reagents with 2-bromo- and 2,6-dibromochromones and synthesis of medicinally important fisetin

Pd-catalyzed mono- and bis-arylation of chromones was demonstrated using triarylbismuths as threefold aryl transfer atom-economic reagents. This unprecedented study involving functionalized chromones afforded regio-selective mono-arylations leading to functionalized 2-arylchromones in good to high yields. Bis-arylation of 2,6-dibromochromones in one-pot operation furnished 2,6-diarylchromones in moderate to good yields. The present methodology was applied in the synthesis of naturally occurring and medicinally important fisetin molecule in high yield.     

Halogen bonding or close packing? Examining the structural landscape in a series of Cu(II)-acac complexes

A series of four bifunctional ligands based on β-diketonate moieties bearing methyl (2), chloro (3), bromo (4) and iodo (5) substituents and their corresponding Cu(II) complexes have been synthesized and crystallographically characterized in order to explore the possibility of using halogen bonds for the directed assembly of predictable architectures in coordination chemistry. The four ligands have characteristic O-H···O intramolecular hydrogen bonds and the structure of ligand 2 is close packed whereas, ligands 3, 4 and 5 contain extended 1-D architectures based on C=O···X halogen bonds. In each case, the halogen-bond donor seeks out the most powerful halogen-bond acceptor (based on electrostatic considerations). In the corresponding Cu(II) complexes the coordination chemistry remains a constant throughout the series, the four-coordinate metal ion sits in a slightly distorted square-planar arrangement, and there are no unexpected appearances of coordinated or non-coordinated solvent molecules. Furthermore, the most powerful halogen-bond acceptors have been almost depleted of charge as a result of metal chelation and none of the potential halogen-bond interactions are capable of competing with the head-to-head close packing that is observed in the methyl, chloro, and bromo, substituted Cu(II) complexes. The enhanced polarizability of the iodine atom, produces a more electropositive surface which means that this structure cannot accommodate a linear head-to-head arrangement due to electrostatic repulsion, and thus [Cu(5)(2)] adopts a unique close-packed structure very different from the other three iso-structural complexes, [Cu(2)(2)]-[Cu(4)(2)].     

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of ethionamide and ethionamide sulfoxide in human plasma: application to a human pharmacokinetic study

A highly sensitive and specific LC‐MS/MS method has been developed for simultaneous quantification of ethionamide and ethionamide sulfoxide in human plasma (300 µL) using prothionamide as an internal standard (IS). Solid‐phase extraction was used to extract ethionamide, ethionamide sulfoxide and IS from human plasma. The chromatographic separation of ethionamide, ethionamide sulfoxide and IS was achieved with a mobile phase consisting of 0.1% acetic acid : acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Peerless Basic C₁₈ column. The total run time was 3.5 min and the elution of ethionamide, ethionamide sulfoxide and IS occurred at 2.50, 2.18 and 2.68 min, respectively. A linear response function was established for the range of concentrations 25.7–6120 ng/mL (r > 0.998) for ethionamide and 50.5–3030 ng/mL (r > 0.998) for ethionamide sulfoxide. The intra‐ and inter‐day precision values for ethionamide and ethionamide sulfoxide met the acceptance as per FDA guidelines. Ethionamide and ethionamide sulfoxide were stable in battery of stability studies, viz. bench‐top, autosampler and freeze–thaw cycles. The developed assay was applied to a pharmacokinetic study in humans. Copyright © 2011 John Wiley & Sons, Ltd.     

Speciation of Mixtures of Copper (I) and Copper (II) Mixed Ligand Complexes by X-Ray Absorption Fine Structure Spectroscopy

Studies on speciation have been done in the mixtures of mixed ligand copper complexes. Three heterogeneous mixtures have been studied, each having one Cu(I) complex and one Cu(II) complex. The Cu(I) complex is [Cu(thu)Cl 0.5H₂O] (1) and the Cu(II) complexes are [Cu(L-phen)(bpy) H₂O] (2), [Cu(L-tyr)(phn) 2.5H₂O] (3), and [Cu(dien)(ina) 4H₂O.1/2SO₄] (4) (where thu = thiourea, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, tyr = tyrosine, dien = diethylenetriamine, and ina = isonicotinate anion). The mixtures have been prepared by mixing the Cu(I) complex with each of the Cu(II) complexes in the ratio of 1:1 by mole percentage. The X-ray absorption fine structure (XAFS) spectra have been recorded at the K-edge of copper in the mixtures as well as in the complexes, separately. The aim of the present work is to make a study of the different methods of speciation using XAFS, viz., principal component analysis (PCA) and the target transformation (TT) method, the linear combination fitting (LCF) method, derivative spectra methods, and normalized difference absorption edge spectra (NDAES) analysis. It has been shown that these methods can be used to determine the relative quantity of the mixed ligand complexes in their mixtures.     

XAFS study of aqua (diethylenetriamine)(isonicotinato)‐copper(II) complex – inference of square‐pyramidal geometry

X‐ray absorption fine structure (XAFS) of aqua (diethylenetriamine) (isonicotinato) copper(II) complex has been investigated. The crystal structure of the complex is unavailable. The X‐ray absorption near edge structure (XANES) spectrum of the complex has been compared with those of the standard compounds to estimate the coordination geometry and oxidation state of copper. This study indicates that the copper center has +2 oxidation state and that it may be penta or hexa‐coordinated. The spectrum has been further compared with those of the earlier studied complexes having square‐pyramidal geometry. Similarity has been observed between them indicating that the complex should have penta‐coordinated square‐pyramidal geometry. The same inference has been obtained from the study of the characteristic pre‐edge and XANES features. This inference has been further examined by analysis of the extended X‐ray absorption fine structure (EXAFS) spectrum. The experimental EXAFS data has been fitted with three different theoretical models for tetra‐coordination, penta‐coordination, and hexa‐coordination. The tetra model is unable to provide a satisfactory fit so it has been ignored. Although the penta and hexa models give comparable results, the parameters obtained indicate that the penta‐coordinated model fits better to the experimental data than the hexa‐coordinated model. This penta‐coordinated model has been further fitted to the experimental data by allowing the coordination number to vary. Such fitting also shows that the penta‐coordinated model is a satisfactory model for the studied complex. The obtained values of mean‐square disorder indicate that the force constants are different for the equatorial and axial bonds. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemically Tunable Proton‐Coupled Electron Transfer in Pd‐Catalyzed Benzaldehyde Hydrogenation

Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted‐acid sites. In contrast, the hydrogenation rate is not affected when H₂ is used as a reduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H₂‐induced hydrogenation pathways. The enhancement of electrocatalytic reduction is realized by the participation of support‐generated hydronium ions in the proximity of the metal particles.