Synthesis, Crystal Structure, Thermal Behavior and IR Characterization of Pentacarbonyl(4-methylpyridine)chromium(0) Complex

Abstract  Pentacarbonyl(4-methylpyridine)chromium(0) complex was isolated from n-hexane solution as yellow plate-like crystals and characterized by using X-ray crystallography. It crystallizes in the orthorhombic system with the space group Cmcm and Z = 4. The unit cell parameters are a = 11.737(1) ?, b = 12.857(2) ?, c = 8.465(1) ?. The single crystal X-ray structure of the complex shows that the coordination sphere around the chromium central atom is slightly distorted octahedron, involving the 4-methylpyridine (4-mp), ligand as a monodentate N-donor ligand and five carbonyl groups. The four equatorial CO groups in the complex, with the Cr–C2 distance of 1.886 Ǻ, are slightly bent away from the 4-methylpyridine ligand with the N–Cr–C2 angle of 91.69°. The pyridine ring plane makes an angle of 135.17° with the Cr–N–CO bond axis. The thermal analysis (differential thermal analysis and thermal gravimetry) and IR spectra of the complex indicated that the compound undergoes complete decomposition to form the Cr₂O₃ as the final decomposition product. Index Abstract  The crystal structure of pentacarbonyl(4-methylpyridine)chromium(0) complex has been determined and its thermal behavior has also been studied.      

Crystal structure and computational studies of (E)-1-(benzo[b]thiophen-3-yl)-N-(4-ethoxyphenyl)methanimine

Crystallography Reports - The title compound, C17H15NOS, crystallizes in the orthorhombic sp. gr. Pca21. Two molecules in the asymmetric unit have similar structure. Crystal structure contains weak...     

Immunomodulatory properties of silver-containing nanocomposite on the basis of polyvinyltriazole

Russian Chemical Bulletin - The water-soluble nanocomposite with the uniform distribution of silver nanoparticles in polymer matrix was synthesized on the basis of poly-1-vinyl-1,2,4-triazole....     

Spectrometric studies on the cloud points of Triton X-405

The effect of various chemicals on the cloud point (CP) of nonionic surfactant Triton X-405 (TX-405) in aqueous solutions has been investigated. In the measurements of cloud point temperatures, UV–visible spectrophotometer was used instead of visual observation. The values of CP for Triton X-405 could not be measured directly because TX-405 had an average number of oxyethylene units per molecule, p ≈ 35 and a CP > 100 °C. To avoid additional measurements under pressure, TX-405 had their CP lowered below the normal boiling point of their solutions by adding the salting-out, CP-lowering salts at various concentrations, measuring the depressed CP values and extrapolating them to zero salt concentration. The CP values decrease linearly with increasing concentration of salts at studied concentrations. The results showed that the addition of the simple salts and nonionic surfactant Triton X-114 (TX-114) which are infinitely miscible with water decreased the cloud point of the TX-405. In this study, the real CP values of TX-405 which are merely listed as >100 °C in the literature was found as 116 ± 1 °C in various samples. In the lyotropic series, it is expected that the effect of F⁻ > Cl⁻ > Br⁻ will be on the decrease in CP, because the ionic sizes increase along the group consequently decreasing the formal charge density on anion, thus lowering the attraction on anion and thereby lowering the attraction of water. The order of CP depression for the other anions is as follows: PO₄³⁻ > SO₄²⁻ > NO₃⁻ > Br⁻. This means that electrolyte containing trivalent anions is more effective at salting-out the PEO chain than those containing divalent anions and monovalent anions. Cations effectiveness is present in the following order for change: Na⁺ > K⁺ > NH₄⁺ because of their effect on water structure and their hydrophilicity. Overall the electrolytes and nonelectrolytes have a large amount of effect on CP of nonionic surfactant, because of their effect on water structure and their hydrophilicity.     

Determination of some organophosphorus and azole group pesticides in water samples by dispersive liquid-liquid microextraction coupled with GC/MS

A dispersive liquid-liquid microextraction (DLLME) procedure coupled with GC/MS detection is described for preconcentration and determination of some organophosphorus and azole group pesticides from water samples. Experimental conditions affecting the DLLME procedure were optimized by means of an experimental design. A mixture of 60 microL chlorobenzene (extraction solvent) and 750 microL acetonitrile (disperser solvent), 3.5 min extraction time, and 7.5 mL aqueous sample volume were chosen for the best recovery by DLLME. The linear range was 1.6-32 microg/L. The LOD ranged from 48.8 to 68.7 ng/L. The RSD values for organophosphorus and azole group pesticides at spiking levels of 3, 6, and 9 microg/L in water samples were in the range of 1.1-12.8%. The applicability and accuracy of the developed method were determined by analysis of spiked water samples, and the recoveries of the analyzed pesticides from artesian, stream, and tap waters at spiking levels of 3, 6, and 9 microg/L were 89.3-105.6, 89.5-103.0, and 92.0-111.3%, respectively.     

A novel approach for highly proton conductive electrolyte membranes with improved methanol barrier properties: Layer-by-Layer assembly of salt containing polyelectrolytes

A series of highly proton conductive electrolyte membranes with improved methanol barrier properties are prepared from polyallylamine hydrochloride (PAH) and polystyrene sulfonic acid (PSS) including salt by Layer-by-Layer (LbL) method. The effects of added salt type (NaCl, MgCl₂) and salt concentration (1.0 M, 0.1 M) on proton conductivity (σ) and methanol barrier properties of the LbL self-assembled composite membranes are discussed in terms of controlled layer thickness and charge density. Furthermore, the influences of ion type in the multilayered composite membranes are studied in conjunction with physicochemical and thermal properties.The deposition of the self-assembly of PAH/PSS film on Nafion is followed by UV–Vis spectroscopy and it is observed that the polyelectrolyte layers growth on both sides of Nafion membrane regularly. (PAH/PSS)₅–Na⁺ and (PAH/PSS)₅–H⁺ with 1.0 M NaCl exhibits 49.6 and 27.8% reduction in lower methanol permittivity in comparison with the pristine Nafion^®117, respectively, while the proton conductivities are 12.97 and 74.69 mS cm⁻¹. Promisingly, it is found that the membrane selectivity values (Φ) of all multilayered membranes in H⁺ form are much higher than that of salt form (Na⁺ and Mg²⁺) and perfluorosulfonated ionomers reported in the literature. Also, we find out that the use of polyelectrolytes with high charge density causes a further improvement in proton conductivity and methanol barrier properties simultaneously. These encouraging results indicate that upon a suitable choice of LbL deposition conditions, composite membranes exhibiting both high proton conductivity and improved methanol barrier properties can be tailored for fuel cells.