Extraction of Hetero Polyanions, P2W17O6110−, P2W18O626−, SiW11O398− by TBP

Hetero polyanions, namely, P₂W₁₇O₆₁ ^10–, P₂W₁₈O₆₂ ^6– and SiW₁₁O₃₉ ^8– were extracted by TBP/dodecane from HNO₃ or HCl solution, as H₁₀P₂W₁₇O₆₁ in the case of P₂W₁₇O₆₁ ^10–. The distribution ratio of P₂W₁₇O₆₁ ^10– depended on both H⁺ concentration and ionic strength of aqueous solution, and free-TBP concentration in organic solution. Experimental equation was established for predicting the distribution ratio of P₂W₁₇O₆₁ ^10– in nitrate system.     

New Heteropolytungstates Incorporating Dioxouranium(VI). Derivatives of α-[SiW9O34]10−, α-[AsW9O33]9−, γ-[SiW10O36]8−, and [As4W40O140]28−

Reaction of uranium salts with several lacunary polyoxotungstate anions yields four new heteropolyanion assemblies in which the uranium atoms occupy pentagonal bipyramidal coordination polyhedra. Treatment of A,-[SiW₉O₃₄]^10– with UO₂(NO₃)₂ leads to Na₁₄[Na₂(UO₂)₂(SiW₉O₃₄)₂]38H₂O (1, Monoclinic, P2₁/c, a=16.5719(8) Å, b=14.1689(7) Å, c=21.2528(10) Å, =111.6670(10)°, V=4786.6(4) ų, Z=2) which proves to be isostructural with the analogous derivative of [PW₉O₃₄]^9– reported previously. Solutions of 1 exhibit the 5-line W-NMR spectrum expected for the structure of C _i point symmetry. The salt (NH₄)₁₇[(UO₂)₃(H₂O)₄As₃W₂₆O₉₄]16H₂O (2, Orthorhombic, Pnma, a=40.1747(2) Å, b=18.25840(10) Å, c=18.0817(2) Å, V=13263.4(2) ų, Z=4) was isolated in 64% yield from a reaction of UO₂(NO₃)₂ with B,-[AsW₉O₃₃]^9–. The structure of the anion in 2 has C _s symmetry and contains one -AsW₉O₃₃ and two novel -AsW₈O₃₀ units linked by the UO²⁺ ₂ groups; an additional WO₆ links the two AsW₈ fragments. Spectrophotometric titration of UCl₄ with the sodium salt of [As₄W₄₀O₁₄₀]^28– indicated the formation of a 4:1 U:As₄W₄₀ complex. During attempts to isolate a crystalline product from this reaction the uranium became oxidized and a guanidinium salt of [Na(UO₂)₃(OH)(H₂O)₆As₄W₄₀O₁₄₀(WO)]^18– (3, Orthorhombic, Fdd2, a=54.848(3) Å, b=80.809(4) Å, c=20.2874(2) Å, V=89919(7), Z=16) was isolated. The partially disordered structure of 3 shows the S₂ and adjacent sites of the lacunary As₄W₄₀ anion to be occupied by three UO₅ and one WO₅ polyhedra. A tetrameric assembly of -SiW₁₀ units linked by UO²⁺ ₂ groups occurs in [{M(OH₂)}₄(UO₂)₄(OH)₂(SiW₁₀O₃₆)₄]^22– (lithium salt, M=Na, 4a, tetragonal, P4₂/nmc, a=b=26.5285(2) Å, c=15.0463(2) Å, V=10589.0(2) ų, Z=2; sodium-potassium salt, M=K, 4b, orthorhombic, Fddd, a=24.180(5) Å, b=31.696(6) Å, c=58.012(12) Å, V=44460(15) ų, Z=8). Tungsten-183 NMR spectra show the slow transformation of the expected 5-line (1:1:1:1:1) spectrum of 4a to a new species giving a 6-line spectrum (2:2:2:1:2:1). The latter complex has not been successfully isolated.     

The behaviour of cellulose in hydrated melts of the composition LiXċn H2O (X=I−, NO3−, CH3COO−, ClO4−)

The dissolution behaviour of cellulose in low temperature molten salts was investigated. Depending on the chosen anions in the melt, cellulose shows different reaction behaviour in different Li⁺containing melts. Dissolution of the polymer was observed in molten LiClO₄3H₂O and molten LiI2H₂O. In the hydrated melts of LiCH₃COO2H₂O and LiNO₃3H₂O a fine distribution of cellulose was stated. Cellulose can be regenerated by cooling the melt and removing the salt by dissolution in water.The structure of the recrystallized product is determined by the used low temperature molten salt.     

Direct versus indirect many-body methods for calculating vertical electron affinities: applications to F−, OH− , NH2−, CN−, Cl−, SH− and PH2−

Electron propagator theory (EPT) is applied to calculating vertical ionization energies of the anions F⁻, Cl⁻, OH⁻,SH⁻, NH₂⁻, PH₂⁻ and CN⁻. Third-order and outer valence approximation (OVA) quasiparticle calculations are compared with ΔMBPT(4) (MBPT, many-body perturbation theory) results using the same basis sets. Agreement with experiment is satisfactory for EPT calculations except for F⁻ and OH⁻, while the ΔMBPT treatments fail for CN⁻. EPT(OVA) estimates are reliable when the discrepancy between second- and third-order results is small. Computational aspects are discussed, showing relative merits of direct and indirect methods for evaluating electron binding energies.     

Fluxional Bonds in Planar B19−, Tubular Ta@B20−, and Cage-Like B39−

Based on detailed bonding analyses on the fluxional behaviors of planar B₁₉⁻, tubular Ta@B₂₀⁻, and cage-like B₃₉⁻, we propose the concept of fluxional bonds in boron nanoclusters as an extension of the classical localized bonds and delocalized bonds in chemistry. © 2018 Wiley Periodicals, Inc.     

Prediction of phase equilibrium for the aqueous systems Rb+, Cs+/Cl−, SO 4 – -H2O and K+, Cs+/Cl−, SO 4 2− -H2O at 25°C

The Pitzer ion-interaction extended by Harvic and Weare was applied to predict the solubility isotherms of reciprocal quaternary systems in which mixed crystals are formed. On the basis of data concerning the binary and ternary subsystems, the four components systems Rb⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O, and K⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O were investigated at 25°C.The results of calculation can be used to model salt crystallization during the concentration of brines.     

Solid state mechanism of the thermal dehydration of [Rh(NH3)5(H2O)]X3 (X = Cl−, Br−, I−)

The solid phase thermal deaquation-anation of [Rh(NH₃)₅(H₂O)]X₃ (X = Cl⁻, Br⁻, I⁻) has been investigated by means of isothermal TG measurements applying all the principal g(α) expressions (0.8 ⩾ α ⩾ 0.2). The values found for the activation energy are low: ≈ 95 kJ mol⁻¹ for the Cl⁻ compound; ~105 kJ mol⁻ for the Br⁻ compound and ≈110 kJ mol⁻¹ for the I⁻ compound. These data permit the assignment of the deaquation-anation mechanism of the S_N1 dissociative type, involving a square-based pyramid activated complex and elimination of water as Frenkel defects. These values are similar to those reported for the Co(III) and Ir(III) analogues, indicating that the D_q parameter is not the principal contribution to the activation energy of the dehydration-anation process.     

Low-voltage thin-layer electrophoresis of inorganic anions on silica gel-G and titanium (IV) tungstate layers: separation of coexisting F−, Cl−, Br− and I−, I−, IO3− and IO4−, Fe(CN)64− and Fe(CN)63−

The electrophoretic behavior of twenty anions has been studied on silica gel-G, titanium (IV) tungstate and silica gel-G- titanium (IV) tungstate admixture layers using 0.1 M solutions of oxalic acid, citric acid, tartaric acid, succinic acid and acetic acid as background electrolyte. The mechanism of migration is explained in terms of adsorption and the solubility of various sodium or potassium salts of the anions in water. Titanium (IV) tungstate behaves only as an adsorbent and not as an ion exchanger. Being a cation exchanger, there is no exchange phenomenon occurring with anions. The migration of halides increase linearly with an increase in the bare ion radii of these ions. Differential migration of the anions on silica gel-G layers led to binary, ternary and quaternary separations of similar anions such as F⁻ – Cl⁻ – Br⁻ – I⁻, I⁻ – IO₃⁻ – IO₄⁻, BrO₃⁻ – IO₃⁻ and Fe(CN)₆³⁻ – Fe(CN)₆⁴⁻. The two cyanoferrate ions are separated from industrial waste water and from fixer and bleach solutions. The migration of anions has also been found to be in accordance with their lyotropic numbers.

     

OH stretching force constants in complexes of water with F−, Cl−, Li+ ions and LiF,LiCl ion pairs by 6-31G ab initio MO calculations

Ab initio MO calculations using 6-31G and 6-31 + G (for complexes with F⁻ and LiF) basis sets have been carried out for complexes of H₂O (monomer and dimer) with F⁻, Cl⁻, Li⁺ ions as well as with LiF and LiCl ion pairs for the evaluation of the OH stretching force constants. The changes in force constants are discussed in terms of molecular interactions, cooperativity effect and interionic electrostatic interactions. It is noticed that the cooperativity effect also operates through ionic bonds in symmetrically hydrated ion pairs and that OH stretching force constants are found to increase in the case of solvent bound ion pairs and symmetrically hydrated halide ions showing anticooperativity effect.     

Dimerization of cobalt-substituted Keggin phosphotungstate, [PW11O39Co(X)]5−, in nonpolar solvents

The tetraheptylammonium (THA) salt of cobalt-substituted polyoxotungstate with Keggin-like structure, (THA)₅[PW₁₁O₃₉Co^II(X)], was investigated by ³¹P NMR and UV/VIS spectroscopies in toluene. A solution obtained after transferring PW₁₁Co from aqueous solution into toluene, using THABr as a transfer agent, and rigorous drying, gives multiple peaks in the ³¹P NMR spectrum. The spectrum in dry toluene significantly simplifies, after extracting a hexane solution several times with water, which removes simple inorganic ions. However, even the dry toluene solution after purification has ³¹P NMR and UV/VIS spectra which cannot be explained using the known equilibrium between (THA)₅[PW₁₁O₃₉Co(H₂O)] and (THA)₅[PW₁₁O₃₉Co(__)]. Both ³¹P NMR and UV/VIS spectroscopies indicate the existence of dimers in dry toluene solutions, (THA)₁₀[(PW₁₁O₃₉Co)₂]. Pure (THA)₅[PW₁₁O₃₉Co(_)] with five-coordinate cobalt can, however, be obtained in dry toluene in the presence of excess inert salt (high ionic strength conditions). Quantum mechanical/molecular mechanical calculations also support dimer formation in toluene.     

Binding of multiple SO2 molecules to small gold cluster anions (AuN−, AuNOH−, N = 1-8)

The binding of SO₂ on gas-phase gold cluster anions, Au_N⁻, and their hydroxide counterparts, Au_NOH⁻, have been studied using density functional theory combined with flow reactor/time-of-flight mass spectrometry techniques. SO₂ is adsorbed on all of the Au_N⁻ and Au_NOH⁻ clusters (N = 1-8) and the hydroxide clusters are more active than the bare anionic clusters. Successive additions of SO₂ molecules (up to four) have been analyzed. In all cases, anionic clusters are shown to bind multiple SO₂ molecules. Theoretical analyses are in agreement with the experimental results, showing that the addition of more than one molecule is thermodynamically favorable. Larger clusters do not necessarily absorb more molecules, as different SO₂ binding motifs on these clusters are present. These results provide important insight for the potential use of these anionic clusters as SO₂ hunters.     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.     

The Catalytic Performance of Preyssler's Anion, [NaP5W30O110]14−, in the Oxidation of Benzyl Alcohols

Under mild conditions, monosubstituted benzyl alcohols were oxidized to benzaldehydes and benzoic acids in the presence of sodium 30-tungstopentaphosphate (Preyssler's anion), [NaP₅W₃₀O₁₂₀]^14? , and hydrogen peroxide as an oxidant. This polyanion with high hydrolytic stability (pH = 0–12), high thermal stability, and high acidic strength shows good activities. The effects of various parameters on the yield of the products, including a catalyst type, a nature of the substitutents, and temperature, were studied. Comparison between Keggin's heteropolyacids, H₃[PW₁₂O₄₀], H₃[PMo₁₂O₄₀], H₄[SiW₁₂O₄₀], and H₄[SiMo₁₂O₄₀], and Preyssler's anion shows that this polyanion reacts similar to Keggin's acids whitout any degradation of the structure.     

[H4AsW18O62]7−, A novel Dawson heteropolyanion and two of its sandwich-type derivatives [Zn4(H2O)2(H4AsW15O56)2]18−, [Cu4(H2O)2(H4AsW15O56)2]18−: cyclic voltammetry and electrocatalytic properties towards nitrite and nitrate

The cyclic voltammetry behaviours of the new Dawson heteropolyanion (HPA) octadecatungstomonoarsenate [H₄AsW₁₈O₆₂]⁷⁻ were studied as a function of pH. The electrochemistry of the fully symmetrical octadecatungstodiarsenate [As₂W₁₈O₆₂]⁶⁻ in a pH 0.3 medium is constituted mainly by four reduction steps, the first two featuring reversible one-electron processes. The comparison of the cyclic voltammetry behaviours of two complexes reveals, interestingly, that the merging of the first two waves of the monoarsenate occurs in a less acidic pH medium than for the diarsenate. The voltammograms of the two corresponding trivacant species, [H₄AsW₁₅□₃O₅₆]¹³⁻ and [As₂W₁₅□₃O₅₆]¹²⁻, in which the symbol □ represents the vacancy, were also studied and compared. The comparison was extended to the Zn- and Cu-sandwich-type derivatives, with particular emphasis on the compounds of the monoarsenate series, [Zn₄(H₂O)₂(H₄AsW₁₅O₅₆)₂]¹⁸⁻ and [Cu₄(H₂O)₂(H₄AsW₁₅O₅₆)₂]¹⁸⁻. All these species prove efficient in the electrocatalytic reduction of nitrite, but only copper-substituted derivatives are active for the electrocatalytic reduction of nitrate. To our knowledge, this observation constitutes the first example of electrocatalysis of nitrate reduction by a sandwich complex of the polyoxometalate family.     

X-ray Crystal Structure of (CNSSS)2(M)2 (M = AsF6 −, SbF6 −, Sb2F11 −)

The crystal structures of (CNSSS)₂(AsF₆)₂, (CNSSS)₂(SbF6)₂, and two phases of (CNSSS)₂(Sb₂F₁₁)₂ have been determined. The AsF₆ ^?, SbF₆ ^?, and α-Sb₂F₁₁ ^? salts crystallize as reddish-brown plates whereas the β-Sb₂F₁₁ ^? salt crystallizes as green rods. The dication ^ß+SSSNCCNSSS^+ß (1²⁺) is the same in all four structures and consists of two 7π rings linked by a sp²-sp² C-C bond (1.462 Å in 1 (AsF₆)₂). The packing in the four structures is similar with stacks of dications along the a-axis and alternating sheets of dications and anions lying in the bc-plane. The differences in the dication-dication contacts is reflected in the variable temperature magnetic data.     

Thermodynamics of Aqueous Diethylenetriaminepentaacetic Acid (DTPA) Systems: Apparent and Partial Molar Heat Capacities and Volumes of Aqueous H2DTPA3−, DTPA5−, CuDTPA3−, and Cu2DTPA− from 10 to 55°C

Apparent molar heat capacities and volumes have been determined for aqueous solutions of the mixed electrolytes Na₅DTPA + NaOH, Na₃CuDTPA + NaOH, and NaCu₂DTPA + NaOH, and the single electrolyte Na₃H₂DTPA (DTPA=diethylenetriaminepentaacetic acid) at temperatures from 10 to 55°C. The experimental results have been analyzed in terms of Young's rule with the Guggenheim form of the extended Debye–Hückel equation and the Pitzer ion-interaction model. These calculations led to standard partial molar heat capacities and volumes for the species H₂DTPA^3–(aq), DTPA^5–(aq), CuDTPA^3–(aq), and Cu₂DTPA^–(aq) at each temperature. The partial molar properties at 0.1 m ionic strength were also calculated. The standard partial molar properties were extrapolated to elevated temperatures with the revised Helgeson–Kirkham–Flowers (HKF) model. Values for the partial molar heat capacities from the HKF model have been combined with the literature data to estimate the ionization constants of H₂DTPA^3–(aq) and the formation constant of the CuDTPA^3–(aq) copper complex at temperatures up to 300°C.     

Adsorption of Cl−, Br−, and I− ions from 0.1 M solutions in methanol on Ga, (In-Ga), and (Tl-Ga) electrodes

Adsorption of Cl^?, Br^?, and I^? (Hal^?) ions from 0.1 M solutions in methanol (MeOH) is studied on the liquid renewable Ga, (In-Ga), and (Tl-Ga) electrodes by the methods of differential capacitance and jet electrode. It is shown that the adsorption parameters and the series of surface activity of halide ions in MeOH essentially depend on the metal nature. On the (In-Ga) and (Tl-Ga) electrodes, as well as on the Hg electrode, the surface activity of halide ions increases in the series: Cl^? < Br^? < I^?; on the Ga electrode, it varies in another series: Br^? < Cl^? < I^?. The data for the Ga/MeOH interface support the result, which was first obtained on the Ga/N-methyl formamide (N-MF) interface, that the effect of inversion of surface activity series can be observed not only in the aprotic solvents, but also in the protic solvents. The data, which were obtained in MeOH, are compared with the corresponding data, which were obtained in N-MF, dimethyl formamide (DMF), acetonitrile (AN), and water. For Ga, (In-Ga), and (Tl-Ga) electrodes, the adsorption of Hal^? varies in the series: H₂O < MeOH ≈ N-MF < DMF < AN. The data obtained in MeOH indicate that the energy of metal-Hal^? interaction (ΔG _M-Hal) increases in the series (Tl-Ga) < (In-Ga) < Ga as the electronic work function increases. This is in agreement with the data, which were obtained in other solvents, and is the evidence for the donor-acceptor nature of metal-Hal^? interaction, where the Hal^? ions are the donors of electron pair with respect to the metal.