Coated wire silver-ion selective electrode based on a N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene.

A novel membrane coated platinum-wire electrode (MCPWE) based on N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene (BTMD) for highly selective determination of Ag+ ion has been developed. The influences of membrane composition and pH on the potentiometric responses of electrode were investigated. The potentiometric responses are independent of the pH of the test solution in the range of 5.0 - 9.0. The electrode shows a linear response for Ag+ ion over the concentration range of 1.0 x 10(-60 to 1.0 x 10(-1) M with a lower detection limit of 6.0 x 10(-7) M. The electrode possesses a Nernstian slope of 59.7 mV decade(-1) and a fast response time of < or = 17 s and can be used for at least 2 months without any observable deviation. The proposed electrode displayed very good selectivity for Ag+ ion with respect to NH4+ and alkali, alkaline earth and some common transition metal ions. The practical utility of the electrode has been demonstrated by its use as the indicator electrode in the potentiometric titration of an AgNO3 solution with a NaI solution and in determination of the silver content of a developed radiological film.     

Response of periodic structures due to moving loadsRéponse de structures périodiques à des charges mobiles

A method is proposed to calculate the response of periodic structures subjected to moving loads. It is based on the Floquet decomposition which allows the restriction of the analysis for the overall system to a generic cell. The main contribution of the approach presented hereafter is that the response is directly deduced from transfer functions in the space-wavenumber domain calculated in an unbounded generic cell. Moreover, the equivalence of this new solution with the response of invariant structures obtained using Fourier transforms is established. To cite this article: H. Chebli et al., C. R. Mecanique 334 (2006).     

Synthesis and Crystal Structure of Bis (Tetrabutylammonium)(4,4′-Azodi(phenylcyanamide)) Salt · [(<Emphasis Type="Italic">n</Emphasis>-Bu)<Subscript>4</Subscript>N]<Subscript>2</Subscript>[Azodicyd<Superscript>2−</Superscript>] · H<Subscript>2</Subscript>O

Abstract The chemical preparation and crystal structure for a 4,4′-azodi(phenylcyanamide) salt) in the solid state are reported. This compound crystallizes in the triclinic space group P with the following unit cell parameters: a = 9.759(3) ?, b = 11.237(4) ?, c = 11.919(4) ?, α = 95.54(3)°, β = 98.50(3)°, γ = 109.39(2)°, Z = 1 and V = 1204.4(7) ?³. The 4,4′-azodi(phenylcyanamide) dianion, azodicyd²⁻, is approximately planar, with the cyanamide groups (–N=C=N) in an anti conformation relative to each other and the azo group (–N=N–) adopting the more thermodynamically stable trans conformation. The crystal X-ray analysis shows that there are one azo molecule cation, two tetrabutylammonium cations and one water molecule in unit cell. Intermolecular O–H···N hydrogen bonds may be effective in the stabilization of the crystal structure of this compound and to form linear chain structure in the packing. Index Abstract Synthesis and crystal structure of Bis (Tetrabutylammonium)(4,4′-Azodi(phenylcyanamide)) salt . [(n-Bu)4N]2[Azodicyd^2-] · H₂O Davar M. Boghaei ^1*, Fatemeh Behzadian-Asl ¹ and Hamid Reza Khavasi^{2 1} Department of Chemistry, Sharif University of Technology, P.O. Box 11155-9616, Tehran, Iran ² Department of Chemistry, Shahid Beheshti University, Evin, Tehran 1983963113, Iran Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of 1,2,4,6-tetraphenylpyridinium tetrabromoferrate(III)

The title structure, which belongs to the triclinicP¯1 space group witha=13.901(4),b=10.732(1),c=10.570(8)Å=109.14(4),=96.17(4), =90.34(2)°, is refined toR=0.052 for 2985I3(I) reflections. The structure consists of a non-interacting 1,2,4,6-tetraphenylpyridinium and tetrahedral tetrabromoferrate (III) ions.     

Fluorine-functionalized nanoporous graphene as an effective membrane for water desalination

Most water in the world is as saline water in seas and oceans. Desalination technology is a promising method to solve the global water crisis. Recently, many attentions have been paid to the graphene-based membranes in water desalination due to their low production cost and high efficiency. In this paper, molecular dynamics simulations are employed to investigate the effect of functionalized graphene nanosheet (GNS) membranes on the performance of salt separation from seawater in terms of water permeability and salt rejection. For this purpose, the hydrogenated (–H) and fluorinated (–F) pores were created on the GNS membrane. Then, the functionalized graphene membrane was placed in the middle of the simulation box in an aqueous ionic solution containing Na⁺ and Cl^? ions. The applied pressure (in the range of 10–100 MPa) was used as the driving force for transport of water molecules across the reverse osmosis (RO) graphene-based membrane in order to obtain the water permeability and salt rejection. Also, radial distribution functions (RDFs) of ion–water and water–water as well as the water density map around the membrane were obtained. The results indicated that the hydrophilic chemical functions such as fluorine (–F) can improve the water permeability at low pressures.

     

Synthesis of 1<Emphasis Type="Italic">H</Emphasis>-1,3-benzimidazoles,benzothiazoles and 3<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-c]pyridine using DMF in the presence of HMDS as a reagent under the transition-metal-free condition

An operationally simple method for synthesis of benzimidazole and 3H-imidazo[4,5-c]pyridine from o-phenylenediamine or pyridine-3, 4-diamine and N,N-dimethylformamide (DMF) in the presence of hexamethyldisilazane (HMDS) as a reagent is described. To evaluate the scope of application of this reagent, it was also used to prepare benzothiazole, 1H-perimidine, and benzoxazole, which was successful for benzothiazole and 1H-perimidine but benzoxazole was not formed. This reaction complies with the principles of green chemistry as it does not use toxic solvents, transition metals, or strong acids. The products are obtained in moderate to excellent yields.     

Utility of 2-furan-2-yl-4-mercapto-6-methylpyrimidine-5-carbonitrile as a precursor for the synthesis of some novel pyrimidines: antibacterial activity

The starting material 2-furan-2-yl-4-mercapto-6-methylpyrimidine-5-carbonitrile 3 was reacted with various reagents resulting in the formation of a group of new pyrimidines and condensed pyrimidines including quinazoline 6 tetrazolopyrimidine 12, pyrazolopyrimidines 14, 18, and 19, triazolopyrimidine 16, and pyrimidopyridazine 20. The antibacterial activity was evaluated for a group of the synthesized compounds against examples of Gram-positive and Gram-negative bacteria.     

A modified reaction for the preparation of amidoalkyl naphthols

An efficient synthesis of amidoalkyl naphthols using FeCl₃·SiO₂ as a heterogeneous catalyst is described. This thermal solvent-free procedure offers advantages such as shorter reaction times, simple work-up, excellent yields, and recovery and reusability of the catalyst.     

Synthesis,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

Comparison of sample preparation methods for determination of free carbon in boron carbide by X-ray powder diffraction

Several sample preparation methods were evaluated for determination of free carbon in boron carbide powders by quantitative X-ray diffraction method, including ultrasonication, wet ball milling and dry ball milling–wet mixing. Quantitation was based on measuring the integral peak area ratio of the diffraction lines of graphite (002) to boron carbide (012) in samples spiked with pure graphite. The dry milling–wet mixing method provided the best precision and accuracy in all the measurements as well as in determination of free carbon in a boron carbide reference material. There was a linear relationship between the integral peak area ratios and graphite added to boron carbide samples which were purified from their free carbon content. The method provided a low detection limit of 0.05 wt% free carbon.