Solvent Extraction of Calcium and Strontium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate in the Presence of Dibutyl Diethylcarbamoylmethylene Phosphonate

Extraction of micro amounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibutyl diethylcarbamoylmethylene phosphonate (DBDECMP, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂⁺\mathrm{HL}_{2}^{+}, ML₂²⁺\mathrm{ML}_{2}^{2+} and ML₃²⁺\mathrm{ML}_{3}^{2+} (M²⁺=Ca²⁺,Sr²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations CaL₃²⁺\mathrm{CaL}_{3}^{2+}, SrL₃²⁺\mathrm{SrL}_{3}^{2+}, EuL₃³⁺\mathrm{EuL}_{3}^{3+} and AmL₃³⁺\mathrm{AmL}_{3}^{3+}, where L is DBDECMP, increases in the order Sr²⁺<Ca²⁺≪Eu³⁺≈Am³⁺.     

Thermochemistry of the silver(I) complexation with 18-crown-6 ether in binary acetonitrile—dimethylsulfoxide solvents

The effect of acetonitrile-dimethylsulfoxide solvents on the enthalpy of silver(I) complexation with 18-crown-6 ether is studied by means of calorimetry. It is found that an increase in the concentration of dimethylsulfoxide leads to an increase in the reaction exothermicity. It is shown that the determining factor in the change in the reaction enthalpy is the solvation effect of the ligand.     

Luminescence of Eu~(2 ) in Strontium Aluminum Oxide System with Long Decay Property

Luminescentmaterialshavinglongdecayperi0dhaveat-IIactedmuchinterestduetotheirpotentialwidespreadaPplicati0ns.Recently,alongdecayluminescentp0wderhavingthecomPositionofSrAl2O4activatedwithEu' wasreportedandregardedasthebestcandidateforpracticalaPPlicationbecauseofitsuniqueadVantages0veritsprecursors.l'2Inthispaper,wereportthesynthesisofthelongdecayluminescentpowderandtheinnuence0fthemolarratioofAlt0sr0ntheethessioncolor.Toproducethelundnescentp0wder,amixtureofSrCO3,Al2O3,Eu2O3andsomesol…     

Structure of the complex [trans-SnF4(H2O)2· (18-crown-6)· 2H2O]

The molecular and crystal structure of the title complex (I) obtained by addition of tin fluoride in a hydrofluoric acid solution to 18-crown-6 in methanol was investigated by X-ray structure analysis. The crystals are monoclinic, space group P2₁/n, a = 13.497(3), b = 7.806(2), c = 9.892(2) Å, β = 95.57(3)°, Z = 2 for C₁₂H₃₂F₄O₁₀Sn. In the polymer chain, the crown ether molecules alternate with the inorganic complexes [trans-SnF₄(H₂O)₂] and are linked to them by O-H...O type hydrogen bonds involving the intermediate water molecules. The weak C-H...F interactions bind the chains into the layers which are parallel to the xz plane.     

Conductance Study of the Binding of K+ by Dibenzo-pyridino-18-crown-6 and 1,10-N,N′-didecyl-diaza-18-crown-6 in Acetonitrile

The binding of K+ by dibenzo-pyridino-18-crown-6 (B2-py-18-C-6) and1,10-N,N-didecyl-diaza-18-crown-6 (22-DD) has been studiedconductometrically at 10, 15, 20 and 25 °C in acetonitrile. Thecomplexes formed were assumed to have 1 : 1 stoichiometry. The complexes ofK+ with 18-crown-6 (18-C-6) and dibenzo-18-crown-6 (B2-18-C-6) were alsostudied for comparison purposes. The stability constant, K, of a givencomplex and its molar conductance, c, were obtained by subjectingthe conductance data to a non-linear least-squares curve fitting procedure.The values of the enthalpy change, H, the entropy change, Sand the Gibbs free energy, G, associated with the formation of the 1: 1 complexes were derived and compared with relevant literature data. Thevalues of G at 25 °C indicate that the binding capacity of thefour macrocycles follows the order 18-C-6 > 22-DD > B2-18-C-6 >B2-py-18-C-6. The difference between the molar ionic conductance of the freeK+ cation and that of the bound cation, KL+, was estimated and the trend insuch differences correlates with the molecular size of the macrocycle, L.     

Computer simulation study of thermodynamic scaling of dynamics of 2Ca(NO3)2·3KNO3

Molecular dynamics (MD) simulations of the glass-former 2Ca(NO(3))(2·3KNO(3), CKN, were performed as a function of temperature at pressures 0.1 MPa, 0.5 GPa, 1.0 GPa, and 2.0 GPa. Diffusion coefficient, relaxation time of the intermediate scattering function, and anion reorientational time were obtained as a function of temperature and densitiy ρ. These dynamical properties of CKN scale as ρ(γ)∕T with a common value γ = 1.8 ± 0.1. The scaling parameter γ is consistent with the exponent of the repulsive part of an effective intermolecular potential for the repulsion between the atoms at shortest distance in the equilibrium structure of liquid CKN, Ca(2+), and oxygen atoms of NO(3)(-). Correlation between potential energy and virial is obeyed for the short-range terms of the potential function, but not for the whole potential including coulombic interactions. Decoupling of diffusion coefficient and reorientational relaxation time from relaxation time take place at a given ρ(γ)∕T value, i.e., breakdown of Stokes-Einstein and Debye-Stokes-Einstein equations result from combined thermal and volume effects. The MD results agree with correlations proposed between long-time relaxation and short-time dynamics, lnτ ∝ 1∕, where the mean square displacement concerns a time window of 10.0 ps. It has been found that scales as ρ(γ)∕T above and below the glass transition temperature, so that thermodynamic scaling of liquid dynamics can be thought as a consequence of theories relating short- and long-time dynamics, and the more fundamental scaling concerns short-time dynamical properties.     

Crystal Structure of [La(NCS)_3(18-crown-6)(DMF)]

ＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆ[Ｌａ（ＮＣＳ）_３（１８－ｃｒｏｗｎ－６）（ＤＭＦ）]ＭａｏＪｉａｎｇ－Ｇａｏ（ＦｕｊｉａｎＩｎｓｔｉｔｕｔｅｏｆＲｅｓｅａｒｃｈｏｎｔｈｅＳｔｒｕｃｔｕｒｅｏｆＭａｔｔｅｒ，ＡｃａｄｅｍｉａＳｉｎｉｃａ，Ｆｕｚｈ?..     

Preparation and crystal structure of bis(dibenzo-18-crown-6)-(tetrachlorocuprato(II)-Cl,Cl′, Cl″, Cl‴)dipotassium diaqua(dibenzo-18-crown-6)potassium dichlorocuprate(I)-dibenzo-18-crown-6

New mixed complex compound bis(dibenzo-18-crown-6)(tetrachlorocuprato(II)-Cl, Cl′, Cl″, Cl?) dipotassium diaqua(dibenzo-18-crown-6)potassium dichlorocuprate(I)dibenzo-18-crown-6 [(CuCl₄)[K(Db18C6)]₂]·[K(Db18C6)(H₂O)₂]⁺·[CuCl₂]^?·Db18C6 was prepared and its structure was studied by the X-ray structural analysis. The structure was found to be disordered. The asymmetric part of its unit cell contains 1/4 of each of its four components. For a given [CuCl₄]^2? anion its Cu²⁺ cation is disordered over two equally probable positions and its independent Cl atom is disordered over three positions differing by occupancy. In this structure two [K(Db18C6)]⁺ fragment of the complex molecule and the complex cation [K(Db18C6)(H₂O)₂]⁺ are of guest-host type with K⁺ cation as the guest. In this structure the statistically disordered alternating cations and Db18C6 molecules form infinite chains. The statistically disordered [CuCl₂]^? anions also form infinite chains.     

Contribution to the thermodynamics of complexes of alkali metal cations with 18-crown-6 in the water—nitrobenzene extraction system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇄ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L=18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. The stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they are found to increase in the cation order Cs⁺Li⁺Na⁺Rb⁺K⁺. Further, the individual extraction constants for the NaL⁺, KL⁺, RbL⁺ and CsL⁺ complex species in the wate-nitrobenzene system were determined; their values increase in the series Na⁺Rb⁺Cs⁺K⁺.     

Crystal structure of [Yb (NO3)3 (phen) (H2O)] · (12-crown-4)

The title complex was prepared by reacting Yb(NO₃)₃ (12-crown-4) with 1,10-phenanthroline (hereafter phen) in acetone. It crystallized in the triclinic space group witha=10.095(5),b=17.415(4),c=8.710(2) Å =92.45(2), =115.83(3), =74.08(3)⁰ andD _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. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. 82158 (27 pages).     

Preparation and Raman spectra of Ca(NO2)2·H2O,Ca(NO2)2 and Mg(NO2)2·H2O

The above named salts have been prepared from aqueous solutions of the pure nitrates. Distinct compounds Ca(NO₂)₂·H₂O and Ca(NO₂)₂ which are free of nitrate impurity have been characterized by their Raman spectra. The hydrated salt appears to contain four crystallographically non-equivalent nitrate groups. A distinct hydrate of magnesium formulated as Mg(NO₂)₂·H₂O can also be prepared and characterized by Raman spectroscopy but this sample always contained significant nitrate impurity.     

Complexation of Dioxovanadium (V) with CDTA in the Water + Methanol Solvent System

The solvent effect has been studied in this research for the interaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with trans-1,2-diaminocyclohexane-N, N, N′, N′- tetraacetic acid monohydrate at T = 298 K, I = 0.10 mol·dm^?3 sodium perchlorate, and in the range of 0–45 % water + methanol mixtures. UV absorbance data as a function of pH and dissociation constants, obtained from potentiometric titrations, were used for the determination of stability constants. The Kamlet–Abboud–Taft (KAT) model has been investigated for a plausible interpretation and calculation of the linear solvation energy relationship coefficient contribution to the formation of three species VO₂H₂L, VO₂HL^? and VO₂L^2?, which were identified in this work.     

Coordination-driven self-assembly of dibenzo-18-crown-6 functionalized Pt(Ⅱ) metallacycles

Coordination-driven self-assembly was used to construct two metallacycles of a dicarboxylatefunctionalized dibenzo-18-crown-6 in combination with either a 0° anthracene-based clip-type acceptor or a 60° phenanthrene-based acceptor. The angularities of these moieties make them suitable for the formation of a [2 + 2] rectangle and a [3 + 3] triangle, respectively. The synthesis, characterization and host-guest chemistry of two metallacycles were described and supported by³¹P{¹     

Syntheses and crystal structures of (18-crown-6)bis(perchlorato-O,O′)strontium and (18-crown-6)bis(perchlorato-O,O′)barium

Two complexes, namely, (18-crown-6)bis(perchlorato-O,O′)strontium (I) and (18-crown-6)bis(perchlorato-O,O′)barium (II), are synthesized. Their crystal structures are determined by X-ray diffraction analysis. The structures of I (space group P2₁/c, a = 15.266 Å, b = 11.080 Å, c = 13.235 Å, β = 109.20°, Z = 4) and II (space group P2₁/n, a = 8.330 Å, b = 11.202 Å, c = 11.752 Å, β = 98.38°, Z = 2) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.077 (I) and 0.041 (II) against 3714 (I) and 2478 (II) independent reflections (CAD-4 diffractometer, λMoK _α radiation). Complex molecules [Sr(18C6)(ClO₄)₂] in the structure of I and [Ba(18C6)(ClO₄)₂] in II (in the inversion center)—are of the host-guest type. The Sr²⁺ or Ba²⁺ cation is localized in the center of a cavity of the 18-crown-6 ligand and coordinated by its all six O atoms. In compounds I and II, the coordination polyhedron of the Sr²⁺ and Ba²⁺ cations (coordination number 10) can be described as a distorted hexagonal bipyramid with two bifurcated vertices at two O atoms of two ClO ₄ ^? ligands, which are disordered in I and II and each of them has two orientations.     

Enhancement of the Schottky Effect in a Si(100)—Water System Using Porous Polymeric Track-Etched Membranes

The kinetics of variation in the electronic work function (EWF) of single-crystal silicon Si(100) exposed to liquid water is studied. It is shown that immersing porous film track-etched membranes (TEMs) with pore sizes of 3.0–0.1 μm in water containing Si(100) considerably reduces the EWF of single-crystal silicon. It is found that a similar effect is observed when TEMs in the form of caps are held over the surface of water containing Si(100) at a distances of around 1.5–2.0 cm. It is speculated that the occurrence of a developed surface of TEMs in an open system changes the supramolecular structure of the water and leads to the formation of associates (H₂O)_n with increased dipole moments (compared to molecular moments), enhancing the Schottky effect during sorption on Si(100) surfaces.     

Enthalpy parameters for interaction of small peptides with 18-crown-6 and aza-18-crown-6 in water at 25°C

Enthalpies of dilution have been determined for binary aqueous solutions of 1-aza-18-crown-6 as well as for ternary aqueous solutions containing glycine, glycylglycine, glycyl-L--alanine, L--alanyl-glycine, L--alanyl-L--alanine, DL--alanyl-DL--alanine, trialanine and 18-crown-6 and/or 1-aza-18-crown-6 and or 1,10-diaza-18-crown-6 at 25°C. The results have been treated by the McMillan-Mayer approach in order to obtain enthalpic virial coefficients for homotactic and heterotactic interactions. A significant exo-effect is demonstrated by the enthalpically favorable interaction between peptides and the 18-crown-6. The additivity of the positive alanyl group contribution toh _xy has been confirmed on the basis of oligomeric data. The influence on the enthalpy of the 18-crown-6-peptide interaction of the methyl group position, in relation to the ammonium group in peptides, has been found to result in the exo-effect decreasing with a decrease of this distance. Some decrease in enthalpy of L--alanyl-L--alanine and DL--alanyl-DL--alanine by 18-crown-6 has been observed as well.Deceased.