Synthesis and crystal structure of a new supermolecular compound: [C12H24O6][H3PMo12O40]center dot 22H(2)O (C12H24O6=18-crown-6)

The title compound, [C12H24O6][H3PMo12O40]. 22H(2)O, was synthesized by the self-assembly of 18-crown-6 (abbreviated as C12H24O6 or 18C6) and H3PMo12O40 in the mixed solvent of CH3OH and CH3CN, and was characterized by IR, H-1 NMR and Xray diffraction for the first time. Crystal data: Triclinic, P (1) over bar, a = 13.428(3) Angstrom, b = 13.557(3)A, c = 14.642(3) Angstrom, a = 105.39(3)degrees, beta = 90.06(3)degrees, gamma = 119.56(5)degrees, V = 2207.5(8) Angstrom(3), Z = 1, R1 = 0.0719, wR2 = 0.1990. It has a disordered alpha-Keggin PMo12O403- anion, which contains the strong alternating short (mean 1.844 Angstrom) and long (mean 1.958 Angstrom) Mo-O-Mo bonds. In the unit cell, crown ethers and molybdophosphates are alternatively arranged in good order along c-axis. An oxonium ion is located at the center of a crown ether molecule., Oxonium ion interacts with 18C6 by the means of hydrogen bonds (mean 2.7771 Angstrom), which are electrostatic or resonant. The observations show the existence of [H3O(C12H24O6)](+) (C) 2000 Elsevier Science B.V. All rights reserved.

Voltammetric study of the sodium ion transfer across micro-water/1,2-dichloroethane interface facilitated by terminal-vinyl liquid crystal crown ether

Sodium ion transfer across micro-water/1,2-dichloroethane (DCE) interface facilitated by a novel ionophore, terminal-vinyl liquid crystal crown ether (LCCE) was studied by cyclic voltammetry. LCCEs have potential applications because of their physicochemical properties and the utilization of crown ethers as selective ionophoric units in other functionalized compounds are interesting. Host-guest-type behavior for such compounds in the liquid-crystalline state is studied. The experimental results suggest that the transfer of the sodium ion facilitated by LCCE was controlled by diffusion of LCCE from bulk solution of DCE to the interface. The diffusion coefficient of LCCE in DCE was calculated to be equal to (3.62 +/- 0.20) x 10(-6) cm(2)/s. Steady-state voltammograms are due to sodium ion transfer facilitated by the formation of 1: 1 metal (M)-LCCE complex at the interface and the mechanism tends to be transfer by interfacial complexation or dissociation (TIC or TID). The stability constant of the complex formed was determined to be log beta(o) = 5.5 in DCE phase. The influence of parameters such as concentration of sodium ion and concentration of LCCE on the sodium ion transfer was investigated.

Sodium ion transfer across micro water/1,2-DCE interface facilitated by liquid crystal crown ether

The sodium ion transfer across the micro-water/1,2-dichloroethane interface facilitated by a novel ionophore, liquid crystal crown ether was studied systematically. The sodium ion transfer facilitated by LCCE is controlled by diffusion studied by cyclic voltammetry. The diffusion coefficient of LCCE in 1,2-dichloroethane was calculated to be equal to (2.61 +/- 0.12) X 10(-6) cm(2)/s and the stability constant of the complex between Na+ and LCCE was determined as lg beta (o) = 5.7 in 1,2-dichloroethane.

Lamellar single crystals of nylon-10,10 crown from a dimethylformamide solution

A new solvent, dimethylformamide (DMF), and the traditional solvent, 1,4-butanediol, were used to prepare single crystals of nylon-10,10 from a dilute solution. The lamellae grown from DMF inhabited a more perfect structure and regular shape than those crystals crystallized from traditional solvents such as 1,4-butanediol and glycerin. These thin and perfect lamellar crystals demonstrated patterns of variation in spacing different from those of melt-crystallized spherulites on heating. Specifically, the two main spacings slightly separated rather than continuously approaching each other when the temperature was greater than 180 degreesC. This is a novel phenomenon observed in nylons. Nevertheless, the usual pattern of change in spacing was observed during the cooling process. These lamellar crystals showed more compact spacing of the (002) and (010/100) planes than spherulites at room temperature. (C) 2001 John Wiley & Sons, Inc.

The crystal structure and supramolecular chain of [La(NO3)(3)(OH2)(2)(phen)]center dot 15-crown-5

[La(NO3)(3)(OH2)(2)(phen)]. 15-crown-5 is hexagonal, P6(5), with a = 10.955(2), c = 43.769(9) Angstrom, and D-calc = 1.668 g cm(-3) for Z = 6. In the complex, two nitrogen atoms (from phen) and eight oxygen atoms (six from three bidentate nitrate anions and two from water molecules) are coordinated to the central La(III) ion, forming a coordination polyhedron which is approximately a bicapped square antiprism. The coordinated water molecules donate hydrogen bonds to the oxygen atoms of the crown ether, forming polymeric hydrogen bonded chains which wrap helically along the unit cell direction c.

Preparation and crystal structures of LaCl3(15-crown-5) and [LaCl2(phen)(H2O)(2)(mu-Cl)](2)center dot(15-crown-5)center dot MeCN

LaCl3(15-crown-5), I was prepared by the reaction of LaCl(3)nH(2)O with 15-crown-5 and bipy (2,2'-bipyridyl). [LaCl2(phen)(H2O)(2)(mu-Cl)](2) .(15-crown-5). MeCN, II, was crystallized from a mixture of LaC1(3) . nH(2)O, phen (1,10-phenanthroline) and 15-crown-5 in MeOH/MeCN, Crystal structures of these two complexes have been determined by X-ray methods. The La(III) ion in I is coordinated by three Cl anions and five oxygen atoms of a crown ether. The two metal ions in II are bridged by two Cl anions and the crown ligand is hydrogen-bonded to the coordinated water molecules to form polymeric... crown/cation/cation/crown... chains.

STRUCTURE OF [LA(NO3)(3)(OH2)(2)(OHME)(BIPY)].15-CROWN-5

[La(NO3)(3)(OH2)(2)(OHMe)(bipy).15-crown-5 is monoclinic, P2(1)/n, with a = 11.239(6), b = 19.302(7), c = 14.458(8) Angstrom, beta = 92.47(5)degrees, and D-calc = 1.63 g cm(-3) for Z = 4. In the complex, two nitrogen atoms (from bipy) and nine oxygen atom

CRYSTAL-STRUCTURES OF LN(NO3)(3) (LN=EU,LU) COMPLEXES WITH A CROWN-ETHER (16-CROWN-5)

The crystal structures of Ln(NO3)(3)(Ln = Eu,Lu) complexes with 16-crown-5 are reported. In [Eu(NO3)(2)(CH3CN)(16-crown-5)][Eu(NO3)(4)(H2O)2].1/2(16-crown-5) one Eu-III ion is coordinated to two bidentate nitrate ions, one acetonitrile molecule and five o

CRYSTAL-STRUCTURE OF [YB (NO3)3 (PHEN) (H2O)]CENTER-DOT(12-CROWN-4)

The title complex was prepared by reacting Yb(NO3)3 (12-crown-4) with 1, 10-phenanthiroline (hereafter phen) in acetone. It crystallized in the triclinic space group P1BAR with a = 10.095(5), b = 17.415(4), c = 8.710(2) angstrom; alpha = 92.45(2), beta = 115.83(3), gamma = 74.08(3)degrees and D(c), = 1.85 g cm-3; Z = 2. The metal ion in this complex is nine-coordinated to three bidentate nitrate ions, two nitrogen atoms of a phen and a water molecule. The crown ligand is hydrogen bonded to the coordination water molecule. The symmetry change of the crown ether is also discussed.

Growth and optical properties of peculiar ZnO tetrapods

Regular ZnO tetrapods with different morphologies have been obtained on Si(100) substrate via the chemical vapour deposition approach. Varying the growth temperature and gas rate, we have obtained different structured ZnO materials: tetrapods with a large hexagonal crown, a flat top and a small hexagonal crown. The results suggest that these tetrapods are all single crystals with a wurtzite structure that grow along the (0001) direction. However, photoluminescence spectra shows that their optical properties are quite different: for those with large hexagonal crown, the green emission overwhelms that of the near band-edge (NBE) ultraviolet (UV) peak, while others have only a strong NBE UV peak at ~386 nm.

Variation Of Flexural Strength Of Cement Mortar Attacked By Sulfate Ions

Under the environment of seawater, durability of concrete materials is one of the chief factors considered in the design of structures. The decrease of durability of structures is induced by the evolution of micro-damage due to the erosion of chlorine and sulfate ions, which is characterized by the reduction of modulus, strength, and toughness of the material. In this paper, the variation of the flexural strength of cement mortar under sulfate erosion is investigated. The results obtained in present work indicate that the erosion time, concentration of sulfate solution, and water-to-cement ratio will significantly affect the flexural strength. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.

Measuring Binding Kinetics Of Surface-Bound Molecules Using The Surface Plasmon Resonance Technique

Surface plasmon resonance (SPR) technology and the Biacore biosensor have been widely used to measure the kinetics of biomolecular interactions in the fluid phase. In the past decade, the assay was further extended to measure reaction kinetics when two counterpart molecules are anchored on apposed surfaces. However, the cell binding kinetics has not been well quantified. Here we report development of a cellular kinetic model, combined with experimental procedures for cell binding kinetic measurements, to predict kinetic rates per cell. Human red blood cells coated with bovine serum albumin and anti-BSA monoclonal antibodies (mAbs) immobilized on the chip were used to conduct the measurements. Sensor-grams for BSA-coated RBC binding onto and debinding from the anti-BSA mAb-immobilized chip were obtained using a commercial Biacore 3000 biosensor, and analyzed with the cellular kinetic model developed. Not only did the model fit the data well, but it also predicted cellular on and off-rates as well as binding affinities from curve fitting. The dependence of flow duration, flow rate, and site density of BSA on binding kinetics was tested systematically, which further validated the feasibility and reliability of the new approach. Crown copyright (c) 2008 Published by Elsevier Inc. All rights reserved.

Wave propagation and the frequency domain Green's functions in viscoelastic Biot/squirt (BISQ) media

In this paper, we examine the characteristics of elastic wave propagation in viscoelastic porous media, which contain simultaneously both the Biot-flow and the squirt-flow mechanisms (BISQ). The frequency-domain Green's functions for viscoelastic BISQ media are then derived based on the classic potential function methods. Our numerical results show that S-waves are only affected by viscoelasticity, but not by squirt-flows. However, the phase velocity and attenuation of fast P-waves are seriously influenced by both viscoelasticity and squirt-flows; and there exist two peaks in the attenuation-frequency variations of fast P-waves. In the low-frequency range, the squirt-flow characteristic length, not viscoelasticity, affects the phase velocity of slow P-waves, whereas it is opposite in the high-frequency range. As to the contribution of potential functions of two types of compressional waves to the Green's function, the squirt-flow length has a small effect, and the effects of viscoelastic parameter are mainly in the higher frequency range. Crown Copyright (C) 2006 Published by Elsevier Ltd. All rights reserved.

Variation of flexural strength of cement mortar attacked by sulfate ions

Under the environment of seawater, durability of concrete materials is one of the chief factors considered in the design of structures. The decrease of durability of structures is induced by the evolution of micro-damage due to the erosion of chlorine and sulfate ions, which is characterized by the reduction of modulus, strength, and toughness of the material. In this paper, the variation of the flexural strength of cement mortar under sulfate erosion is investigated. The results obtained in present work indicate that the erosion time, concentration of sulfate solution, and water-to-cement ratio will significantly affect the flexural strength. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.

Synthesis Of Plastic Zr-Based Bulk Metallic Glass Matrix Composites By The Copper-Mould Suction Casting And The Bridgman Solidification

Zr-based bulk metallic glass matrix composites with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.(5) were synthesized by the copper-mould suction casting and the Bridgman solidification. The composite, containing a well-developed flowery beta-Zr dendritic phase, was obtained by the Bridgman solidification with the withdrawal velocity of 0.8 mm/s and the temperature gradient of 45 K/mm, and the ultimate strength of 2050 MPa and fracture plastic strain of 14.6% of the composite were achieved, which was mainly interpreted by the homogeneous dispersion of bcc beta-Zr phase in the glass matrix. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.