Superionic conductivity in (BEDT-TTF)AgXiY

We have synthesized the organic conductor (BEDT-TTF)Ag_XI_Y (X 1.8 and Y 2.9). This compound has, in addition to high electronic conductivity (_{300 k} 5–10 ^–1 · cm^–1), significant ionic conductivity connected with the motion of silver ions. The value of this ionic conductivity at room temperature is 10^{–3 –1} · cm^–1. The activation energy for diffusion of Ag ions is equal to 0.2 eV.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 247–249, March–April, 1989.     

Magnetic anisotropy of cyclopropane and epoxide rings

MO LCAO results are presented for the interatomic contribution to the anisotropy of the diamagnetic susceptibility; values of _d=–23.5 · 10^–6 and _d=–13.8 · 10^–6 cm³/mole are obtained for the cyclopropane and epoxide ring systems, respectively. The results are used to interpret PMR spectra in terms of the configuration and conformation of the and forms of caran-4-ol and two stereoisomers of caranone.     

High-Performance Liquid Chromatographic Determination of Quinolizidine Alkaloids in Radix Sophora Flavescens Using Tris(2,2′-Bipyridyl)Ruthenium(II) Electrochemiluminescence

Electrogenerated chemiluminescences (ECLs) of quinolizidine alkaloids including matrine (MT), sophocarpine (SC), and sophoridine (SRI) are studied. The light emission is caused by an electro-oxidation reaction between Ru(bpy)₃²⁺ and the tertiary amino group on the alkaloid compounds. A thin-layer flow cell equipped with a glassy carbon disk electrode (22.1mm²) at the potential of ⁺1.30V (vs. Ag/AgCl) was applied for ECL observation. MT, SC and SRI were separated and quantitatively determined within 25min by an ODS-80 Ts reversed-phase column with a mobile phase containing 80mmolL^–1 NaH₂PO₄–K₂HPO₄ buffer+acetonitrile (7:3)+40mmolL^–1 sodium dodecyl sulfate (pH 6.5). The determination limit at an S/N of 3 ranged from 3×10^–9gmL^–1 for MT, 6×10^–9gmL^–1 for SC and 1×10^–9gmL^–1 for SRI. The recoveries are from 92 to 108%, with repeatability ranging from 1.3 to 4.5% (relative standard deviation). The method was successfully applied to the determination of quinolizidine alkaloids in Sophora flavescens samples.     

Properties of aqueous salt solutions of poly(ethylene oxide). Cloud points, θ temperatures

The determination of the properties of aqueous salt solutions of poly(ethylene oxide) has been extended to the cloud point, and temperature measurements have been made at several concentrations for various salts (flourides, iodides, acetates, formates, phosphates, bromides, thiosulfates and perchlorates). The resulting dependency of the critical temperatures (mostly between 290–350 K) on the molar concentration can be expressed as sequences showing the decreasing effect of anion species or cation species in salting out the polymer. The decreasing order of effectiveness of the anions in reducing the temperature is PO ₄ > HPO ₄ > S₂O ₃ > H₂PO ₄ ^– >F^– > HCOO^– > CH₃COO^– > Br^– > I^–. The order for cations is K⁺ Rb⁺ Na⁺ Cs⁺ > Sr⁺⁺ > Ba⁺⁺ Ca⁺⁺ > NH ₄ ⁺ > Li⁺. The changes brought about in temperatures by the salts were found to be the results of the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and additive salts and of the change of water structure by structure making or structure breaking ions, and of the influence of salts on the hydration sheath of the polymer.     

Reaction of H2PtCl6 with 18-crown-6 and dibenzo-18-crown-6 in 1,2-dichloroethane and acetonitrile

Compounds of the compositions [2(18-crown-6)6(H₂O)2(C₂H₄Cl₂){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], [4(18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)(Pt₂Cl₁₀)^2–], [(dibenzo-18-crown-6)6(H₂O){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], and [4(dibenzo-18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)Pt₂Cl₁₀)^2–] were prepared by reactions of H₂PtCl₆ with 18-crown-6 and dibenzo-18-crown-6.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1593–1599.Original Russian Text Copyright © 2004 by Guseva, Busygina, Khasanshin, Polovnyak, Yarkova, Yusupov.This revised version was published online in April 2005 with a corrected cover date.     

Pressure effects on aminonaphthalene dye fluorescence in H2O and D2O

The pressure dependence of excited-state proton transfer equilibria has been examined for aqueous solutions of several substituted napthalene dyes, in particular 1-dimethylaminonaphthalene-5-sulfonic acid (DANS). The pressure-induced shift in equilibrium is characterized by volume changes spanning the range V ^*=–18 cm³ mole^–1 to V ^*=+4 cm³-mole^–1. A deuterium oxide solvent isotope effect is evident in the pressure response of DANS, leading to a 35% smaller V_* in D₂O relative to H₂O.     

Heating and quenching of metastable superconducting compounds with a plasma jet

Superconducting compounds, such as cubic -MoC_1–x, cubic -WC_1–x, hexagonal MoB₂, and cubic -TaN, which are metastable at room temperature, have been formed by heating and quenching of their respective equilibrium phases, such as hexagonal -MoC_1–x, hexagonal WC, rhombohedral Mo₂B₅, and hexagonal -TaN in a plasma jet. From calculations based on a simple model, the quenching rate of particles has been estimated to be 10⁵ deg s^–1.     

Determination of Total Selenium Content in Cereals and Bakery Products by Flow Injection Hydride Generation Graphite Furnace Atomic Absorption Spectrometry Applying in-situ Trapping on Iridium-Treated Graphite Platforms

A flow injection hydride generation graphite furnace atomic absorption spectrometric (FI-HG-GFAAS) method was applied to the determination of Se in Se-doped and undoped cereals and bakery products. For the purpose of doping, the soils used for the cultivation of the cereals were dosed with Se-doped foliar fertilizers. The samples were dissolved in a mixture of HNO₃ and H₂O₂ solutions using microwave-assisted digestion. The decomposition of H₂Se generated from the sample solutions and the trapping of elemental Se were performed at a temperature of 300°C on an Ir-pretreated integrated graphite platform of a transversally heated graphite atomizer (THGA). For release of the trapped Se within a fairly short atomization time (5s), an atomization temperature of 2200°C was observed to be optimal. The overall efficiency of hydride generation, transport and trapping was 86%.The upper limit of the linear dynamic range of calibration was 10µgL^–1, which corresponds to 0.5µgg^–1 for solid samples. Recovery of the samples spiked with Se^VI solutions was found to be 93±6% on average. The relative standard deviation of the determinations was less than 8%. The limit of detection was found to be 0.06µgL^–1, corresponding to 3ngg^–1 for solid samples. The accuracy of the method was verified with the use of IAEA-155 (whey powder) certified reference material. End-capped THGA tubes resulted in an extension of the linear calibration range compared to that of standard THGAs.The Se content in bakery products made of undoped cereals ranged from 7.7 to 68ngg^–1 (wet weight) in 18 samples, whereas the Se content of the corresponding cereals was found to be below 100ngg^–1 (wet weight). The Se level of cereals grown on soils treated with Se-doped fertilizers ranged from 128 to 1046ngg^–1 (wet weight), and it depended linearly on the Se concentration of the corresponding foliar fertilizer.     

Electron-transfer induced change of direction of interannular haptotropic isomerization of fluorenyltricarbonylchromium anions

It has been shown by cyclic voltammetry in a THF medium in the temperature range from –70 °C to +20 °C that one-electron electrochemical reduction of (⁶-C¹³H¹⁰)Cr(CO)₃ (1) to the corresponding 19-electron anion radical (1 ^–) is accompanied by splitting off of a H atom to form the 18-electron carbon-centered anion (⁶-C₁₃H₉)Cr(CO)₃ (^–2 ), which at room temperature undergoes intramolecular haptotropic isomerization to the metal-centered (⁵-C₁₃H₉)Cr(CO)₃ ^– (^– 3) anion. The reversible one-electron reduction of3 ^– to the corresponding 19-electron radical dianion3 ^2.– induces ^{5 6} interannular isomerization. In contrast to the equilibrium shift to the ⁵-isomer in 18-electron complexes 2 and 3, in their 19-electron analogs the equilibrium is shifted to the ⁶-isomer.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 48–53, January, 1994.This work was carried out with financial support from the Russian Foundation for Basic Research (no. 93-03-5209)     

Determination of Trace Iron in KH2PO4 Crystal by Derivative Adsorption Chronopotentiometry

A sensitive derivative adsorption chronopotentiometric method was developed to determine trace amounts of Fe³⁺. The influence of preconcentration time, pH of solution and constant reducing current of the peak height is discussed. The detection limit and the linear range are 5.0×10^–10 and 2.0×10^–93.0×10^–6molL^–1, respectively. The method was used to determine trace Fe³⁺ in KH₂PO₄ crystals (KDP).     

Dielectric properties of cleaned and monodisperse polystyrene latexes in microwaves

The dielectric behavior (, ) of three well-cleaned monodisperse polystyrene latexes having the same particle size and the same number of chemically-bound surface groups has been studied at a fixed microwave frequency (9.4 GHz), as a function of temperature and surface group (SO ₄ ^– , COO^–, OH).A large dielectric relaxation was observed in the sulfate-stabilized latex, which has the most polar surface end-group. The anomalous behavior in the thermal dependence of the hydroxyl and carboxyl-stabilized latexes (the OH latex being more pronounced than the COO^– latex) may originate from differences in the experimental conditions used for the preparation of such polymer colloids, or due to the presence of ionic species.On the basis of various dielectric models, the apparent volume fractions of the latexes were calculated. The amount of bound water around the latex particle was quantitatively correlated to the polarity of surface end-group (SO ₄ ^– > COO^– > OH). The differences between the calculated and actual values were not only a reflection of the thickness of vicinal water, but could also be indicative of the presence of oligomeric species in the suspension's medium (serum) of the latex. The permittivities of hydrated particle and of bound water were obtained with a non-linear iterative procedure.     

Diaqua[N,N-di(2-carboxyethyl)-o-anisidinato]copper(II) Dihydrate [Cu(o-Andp)(H2O)2] · 2H2O: Synthesis and Crystal Structure

Crystals of [Cu(o-Andp)(H₂O)₂] · 2H₂O (where o-Andp^2–is -anisidine-N,N-di-3-propionate) were synthesized and studied using X-ray diffraction analysis. The crystals are triclinic: a= 12.063(1) Å, b= 12.483(3) Å, c= 13.586(2) Å, = 91.29(1)°, = 111.67(1)°, = 104.00(1)°, V= 1830.5(5) ų, space group P , Z= 2, and R= 0.0528 for 5965 reflections with I2(I). The two crystallographically independent complexes are isostructural. The tetragonal–bipyramidal coordination of copper(III) involves three O atoms, the N atom of the tetradentate ligand o-Andp^2–, and two O atoms from water. The aminodipropionate group of the ligand (average Cu–O 1.939 Å and Cu–N 2.051 Å) and one of the coordinated water molecules (Cu–O(w) 1.991 Å) lie in the equatorial plane. The second water molecule (Cu–O(w) 2.32 Å) and the methoxy O atom of o-Andp^2–(Cu–O 2.37 Å) are in the apical positions of the bipyramid.     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Substitution of [Pt(terpy)H2O]2+ and [Pt(bpma)H2O]2+ with thiols in acidic aqueous solution. terpy = 2,2′:6′2″-terpyridine; bpma = bis(2-pyridylmethyl)amine

The substitution behaviour of [Pt(terpy)H₂O]²⁺ and [Pt(bpma)H₂O]²⁺, where terpy is 2,2:62-terpyridine and bpma is bis(2-pyridylmethyl)amine, was studied as a function of entering thiol concentration and temperature. The reactions between the Pt-complexes and DL-penicillamine, L-cysteine and glutathione were carried out in a 0.10 mol dm^–3 aqueous HClO₄ medium using stopped-flow and conventional u.v.–vis spectrophotometry. The observed pseudo-first-order rate constants for the substitutions are given by k _obs = k ₂[thiol] + k _–2. The k _–2 term represents the reverse solvolysis. This was found to be zero for Pt^II(terpy) which was the most reactive complex. The second-order rate constants, k ₂, for the three thiols varied between 0.107 ± 0.001 and 0.517 ± 0.025 M^–1 s^–1 for Pt^II(bpma) and 10.7 ± 0.7–711.9 ± 18.3 M^–1 S^–1 for Pt^II(terpy), whereas glutathione was found to be the strongest nucleophile. An analysis of the activation parameters, H and S , clearly shows that the substitution process is associative in nature.     

Differential pulse voltammetric methods for the simultaneous estimation of uranium-iron and uranium-cadmium mixtures in solution

Differential pulse voltammetric methods have been developed for the simultaneous estimation of the constituents of uranium-iron and uranium-cadmium mixtures in solution. A mixture of 1M H₃PO₄–1M KH₂PO₄ (with a pH1.5), was found to be the most ideal supporting electrolyte for both methods, among many that were evaluated for their suitability. In uranium-iron mixtures the calibration for iron was found to be linear up to 150 g ml^–1 (r²=0.9986), while that of uranium up to 500 g ml^–1 (r²=0.999). Iron at 6.7 g ml^–1 level could be determined in the presence of 800 fold uranium (wt/wt) without significant interference. Uranium at 21 g ml^–1 level could be analyzed with 5-fold iron (wt/wt). This upper limit of iron was due to the precipitation of iron as phosphate. In the case of uranium — cadmium mixtures, cadmium calibration for cadmium was found to be linear up to 1300 g ml^–1 (r²=0.9993). Concentration levels of 4.6 g ml^–1 Cd could be determined at a 500-fold excess (wt/wt) of uranium. Uranium calibration was linear up to 500 g ml^–1 (r²=0.999) and 21 g ml^–1 uranium could tolerate up to a 1000-fold excess of cadmium (wt/wt). Both procedures could tolerate 10 g ml^–1 levels of metal ions, such as chromium, copper, manganese, molybdenum and vanadium.     

Electrode kinetics in cyanide silver-plating electrolytes at different surface coverages by lead adatoms

Effective values of exchange current i ₀, cathodic and anodic transfer coefficients and , and cathodic and anodic reaction orders with respect to cyanide ions (P _c, P _a) are measured in cyanide silver-plating electrolytes at different surface coverages by lead adatoms . With increasing coverage, i ₀ and increase from 5 × 10^–5 A cm^–2 and 0.24 in pure solutions to 8 × 10^–5 A cm^–2 and 0.3 at = 0.4, with P _c and P _a hardly altering. The cathodic process markedly accelerates at = 0.6, while at 0.5 the kinetics of the cathodic process is unstable. Different effects of lead adatoms on cathodic and anodic gold and silver plating in cyanide solutions are due to lead salts not affecting the metal substrate dissolution mechanism in the latter case.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 468–474.Original Russian Text Copyright © 2005 by Bek, Shuraeva.     

The potentiometric determination of stability constants of macrocyclic ethers using linear regression techniques

Summary The stability constants of various stoichiometries of NaCl complexes of the macrocyclic ethers of 15-crown-5, benzo-15-crown-5, 18-crown-6 and benzo-18-crown-6 were measured by maintaining identical initial ion-ligand concentrations [A ₀ ⁺ ]=[L_o] and using the expression of the stability constant _i of a complex formation, 1/_i[L_o]^n+m–1=(1–nP)ⁿ(1–mP)^m/P where P=P_AL/[1+P_AL(m–1)]. The potentiometric measurements were carried out in water with a glass membrane electrode in a computer-ion meter system.Submitted to IUPAC, International Symposium on Macrocyclic Ligands for the Design of New Materials, 1992, Surrey, UK     

Complexation,solubilities and thermodynamic functions for cerium(III) fluoride-water system

The solubility, solubility product and the thermodynamic functions for the CeF₃–H₂O system have been measured using the radiometric, conductometric and potentiometric techniques. The radiometric values for the solubility and solubility product, the lowest and more acceptable for reasons cited in previous papers, are 3.14·10^–5 M and 2.17·10^–17 respectively. The enthalpy change measured by the conductometric method is almost twice as that obtained by potentiometric method due to abnormal conductances registered at higher temperatures. The average values for H^o and G^o and S^o at 298 K are 53.0±17.4, 91.7±4.0 and –129.7±58.2 KJ·mol^–1 respectively. The positive values for H^o and G^o and the negative value for S^o are indicative of the low solubility of this salt in water. The stability constants for the mono- and difluoride complexes of Ce(III) have been determined potentiometrically using unsaturated solution mixtures of Ce(III) and F^–. These values for CeF⁺ and CeF ₂ ⁺ are 997±98 and (1.03±0.44)·10⁵, respectively. Studies on pH dependence of the solubility shows that the solubility reaches a minimum value at a pH of about 3.2.     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: III. Products of >Si

Permenov  D. G.  Radzig  V. A. 《Kinetics and Catalysis》2004,45(2):273-278

Crystal and molecular structure of the simple cation-radical salt ethylenedithiopropylenedithiotetrathiafulvalene trichloromercurate (EPT)HgCl3

The new cation-radical salt (EPT)HgCl₃ is prepared. Its structure and electrical conductivity are studied. The crystal structure of (EPT)HgCl₃ contains (EPT)⁺ in the chair conformation and trigonal planar HgCl₃ ^– packed into organic and inorganic layers alternating along thea axis. Shortened intermolecular contacts join HgCl₃ ^– into infinite chains along the c axis (Hg...Cl, 3.289 and 3.387 Å), form stacks (S...S, 3.536 and 3.597 Å) and layers (S...S, 3.427–3.498 Å) of EPT⁺ cation-radicals, and create cation-anion interactions between neighboring layers in the crystal (Cl...S, 3.396–3.521 Å, Cl...C, 3.360 Å). The configuration of the bonds around Hg in HgCl₃ ^– is distorted trigonal planar: Hg-Cl, 2.342(3)–2.449(3) Å, Cl-Hg-Cl, 110.7(1)–137.4(1). The Hg atom lies out of the plane of the Cl atoms by 0.015 Å. The conductivity of (EPT)HgCl₃ at 20°C is ₃₀₀ 5·10^–2 (·cm)^–1. The dependence of conductivity on temperature is semiconducting in nature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2055–2061, September, 1991.