Etude du Systeme Ternaire Se-Te-Sn

This work is a part of the systematic study of the ternary based chalcogenides systems. The aim is to determine the phase equilibrium, and to determine the limits of the phase area. This is done in view to perfecting knowledge of elaboration conditions for new materials and to study of their physical properties. Few works have been devoted to the study of the ternary system Se-Te-Sn, only the cross section SnSe-SnTe has been studied [1] and [2]. The experimental study by DTA, DSC and X-ray diffraction on powder performed at room temperature, exhibits a miscibility gap in the liquid state which narrows as it goes through the Sn-Se binary system. Three cross sections behave as ‘quasi-binary‘ system and six ternary invariants have been exhibited: three ternary eutectics and three ternary quasi-peritectics. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic Method for Synthesis of Aspirin by a Green,Efficient and Recyclable Solid Acid Catalyst (Preyssler's Anion) at Room Temperature

Synthesis of aspirin at room temperature via O‐acetylation of salicylic acid in the presence of Preyssler type heteropolyacids has been investigated in order to contribute toward clean technology, which is the most important need of the society. All of the catalysts are recyclable and reusable.     

The synthesis of unsymmetrically N-substituted chiral 1,4,7-triazacyclononanes

A number of chiral unsymmetrically N-substituted 1,4,7-triazacyclononane ligands have been prepared by modular methods. The key step in the synthesis centres on the macrocyclisation of three tertiary amide precursors under standard Richman-Atkins conditions which allows for subsequent N-functionalisation.     

Pyrazine Complexes of Octacyanometallates of Mo(IV) and W(IV) With 8-hydroxyquinoline: Synthesis,characterisation and thermal studies

The complexes formed by photosubstitution of pyrazine (Pz) in octacyanomolybdate(IV) and -tungstate(IV) with 8-hydroxyquinoline have been assigned the formulae [Mo(CN)₂(OH)₂(Pz)₂(OX)] and [W(CN)₂(OH)₂(Pz)₂(OX)·1.5H₂O]. Coordination of Pz as an unidentate ligand by donating a lone pair of electron from nitrogen is shown by an absorption peak between 8–11 µ. Mechanism for the thermal decomposition of the complexes has been given. The formation of tungsten metal as residue in case of II has been confirmed by XRD analysis. The kinetic and thermodynamic parameters like activation energy (E _a), pre-exponential factor (A) and entropy of activation (S ^#) were calculated employing different integral methods of Doyle, Coats and Redfern and Arrhenius.H for each stage of decomposition was obtained from DSC.This revised version was published online in November 2005 with corrections to the Cover Date.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

Three New Acrylic Acid Derivatives from Achillea mellifolium as Potential Inhibitors of Urease from Jack Bean and α-Glucosidase from Saccharomyces cerevisiae

(1) Background: Achillea mellifolium belongs to a highly reputed family of medicinal plants, with plant extract being used as medicine in indigenous system. However, limited data is available regarding the exploitation of the medicinal potential of isolated pure compounds from this family; (2) Methods: A whole plant extract was partitioned into fractions and on the basis of biological activity, an ethyl acetate fraction was selected for isolation of pure compounds. Isolated compounds were characterized using different spectroscopic techniques. The compounds isolated from this study were tested for their medicinal potential using in-vitro enzyme assay, coupled with in-silico studies; (3) Results: Three new acrylic acid derivatives (1–3) have been isolated from the ethyl acetate fraction of Achillea mellifolium. The characterization of these compounds (1–3) was carried out using UV/Vis, FT-IR, 1D and 2D-NMR spectroscopy (¹H-NMR, ¹³C-NMR, HMBC, NOESY) and mass spectrometry. These acrylic acid derivatives were further evaluated for their enzyme inhibition potential against urease from jack bean and α glucosidase from Saccharomyces cerevisiae, using both in-silico and in-vitro approaches. In-vitro studies showed that compound 3 has the highest inhibition against urease enzyme (IC₅₀ =10.46 ± 0.03 μΜ), followed by compound 1 and compound 2 with percent inhibition and IC₅₀ value of 16.87 ± 0.02 c and 13.71 ± 0.07 μΜ, respectively, compared to the standard (thiourea-IC₅₀ = 21.5 ± 0.01 μΜ). The investigated IC₅₀ value of compound 3 against the urease enzyme is two times lower compared to thiourea, suggesting that this compound is twice as active compared to the standard drug. On the other hand, all three compounds (1–3) revealed mild inhibition potential against α-glucosidase. In-silico molecular docking studies, in combination with MD simulations and free energy, calculations were also performed to rationalize their time evolved mode of interaction inside the active pocket. Binding energies were computed using a MMPBSA approach, and the role of individual residues to overall binding of the inhibitors inside the active pockets were also computed; (4) Conclusions: Together, these studies confirm the inhibitory potential of isolated acrylic acid derivatives against both urease and α-glucosidase enzymes; however, their inhibition potential is better for urease enzyme even when compared to the standard.     

X-ray investigation of the crystallization of chalcogenide glasses of the type (As2Se3)1−x:(Tl2Se)x

Amorphous and crystalline states of As₂Se₃, (As₂Se₃)₃ : Tl₂Se and As₂Se₃ : Tl₂Se have been studied using X-ray diffraction techniques. Structural changes arise during the process of annealing in the temperature range between their softening and melting points are reported and their rates investigated. The crystallization temperatures were found to be 105 ± 5 °C, 135 ± 5 °C and 180 ± 5 °C respectively. The unit cell parameters are identified for each of the three resulting crystalline phases, that for As₂Se₃ : Tl₂Se being orthorhombic while the other two are monoclinic.     

Dispersive liquid–liquid microextraction and spectrophotometric determination of cobalt in water samples

A new simple and rapid dispersive liquid–liquid microextraction has been applied to preconcentrate trace levels of cobalt as a prior step to its determination by spectrophotometric detection. In this method a small amount of chloroform as the extraction solvent was dissolved in pure ethanol as the disperser solvent, then the binary solution was rapidly injected by a syringe into the water sample containing cobalt ions complexed by 1-(2-pyridylazo)-2-naphthol (PAN). This forms a cloudy solution. The cloudy state was the result of chloroform fine droplets formation, which has been dispersed in bulk aqueous sample. Therefore, Co-PAN complex was extracted into the fine chloroform droplets. After centrifugation (2 min at 5000 rpm) these droplets were sedimented at the bottom of conical test tube (about 100 µL) and then the whole of complex enriched extracted phase was determined by a spectrophotometer at 577 nm. Complex formation and extraction are usually affected by some parameters, such as the types and volumes of extraction solvent and disperser solvent, salt effect, pH and the concentration of chelating agent, which have been optimised for the presented method. Under optimum conditions, the enhancement factor (as the ratio of slope of preconcentrated sample to that obtained without preconcentration) of 125 was obtained from 50 mL of water sample, and the limit of detection (LOD) of the method was 0.5 µg L^?1and the relative standard deviation (RSD, n = 5) for 50 µg L^?1 of cobalt was 2.5%. The method was applied to the determination of cobalt in tap and river water samples.     

Silver(I)‐N‐heterocyclic carbene complexes of bis‐imidazol‐2‐ylidenes having different aromatic‐spacers: synthesis,crystal structure,and in vitro antimicrobial and anticancer studies

A series of Ag(I) complexes ( 6 , 7 , 8 , 9 ) derived from imidazol‐2‐ylidenes was synthesized by reacting Ag₂O with an o‐, m‐, p‐xylyl or 1,3,5‐triazine‐linked imidazolium salts ( 1 , 2 , 3 , 4 ) and then characterizing these using various spectro‐analytical techniques. Additionally, triazine‐linked bis‐imidazolium salt 5 was characterized using the single‐crystal X‐ray diffraction method. Complexes 6–9 were formed from the N‐heterocyclic carbene ligand precursors 1–3 as PF₆^‐ salts in good yields. Conversely, salt 5 does not form Ag(I) complex even under various reaction conditions. Using ampicillin as a standard, complexes 6–9 were tested against bacteria strains Escherichia coli and Staphylococcus aureus as Gram‐negative and Gram‐positive bacteria, respectively, showing potent antimicrobial activities against the tested bacteria even at minimum inhibition concentration and bacterial concentration levels. Furthermore, the potential anticancer activities of the reported complexes were evaluated against the human colorectal cancer (HCT 116) cell lines, using 5‐fluorouracil as a standard drug. The highest anticancer activities were observed for complex 8 with an IC₅₀ value of 3.4 μm , whereas the lowest was observed for complex 9 with an IC₅₀ value of 18.1 μm . Copyright © 2013 John Wiley & Sons, Ltd.     

Old Reagent,New Results: Aromatization of Hantzsch 1,4-Dihydropyridines with Supported Bismuth Nitrate under Microwave Irradiation in Solventless System

Hantzsch 1,4-dihydropyriines were rapidly and efficiently oxidized using bismuth nitrate supported onto silica gel under microwave irradiation.