The effect of NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> and OH<Superscript>−</Superscript> ions on the laser ablation of Cs<Superscript>+</Superscript> ion on Type 304 stainless steel

Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO₃ solution, respectively. Cs⁺ ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm² were performed. The surface morphology and the relative atomic mole ratio of the specimen surface were investigated by SEM and EPMA. The order of Cs⁺ ion removal efficiency of laser was no-treatment < KOH < KNO₃ during the 42 shots. From the investigation of XPS peaks around 532.7 and 292.9 eV, KNO₃ on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that Cs₂O particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs⁺ ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and it changed into Fe₂O₃. It was also suggested that Cs₂O particulates were formed by the reaction between the reactive oxygen generated from the decomposition of K₂O and Cs⁺ ion on the metal surface..     

SO<Stack><Subscript>2</Subscript><Superscript>−·</Superscript></Stack> electron transfer ion/ion reactions with disulfide linked polypeptide ions

Multiply-charged peptide cations comprised of two polypeptide chains (designated A and B) bound via a disulfide linkage have been reacted with SO2-* in an electrodynamic ion trap mass spectrometer. These reactions proceed through both proton transfer (without dissociation) and electron transfer (with and without dissociation). Electron transfer reactions are shown to give rise to cleavage along the peptide backbone, loss of neutral molecules, and cleavage of the cystine bond. Disulfide bond cleavage is the preferred dissociation channel and both Chain A (or B)-S* and Chain A (or B)-SH fragment ions are observed, similar to those observed with electron capture dissociation (ECD) of disulfide-bound peptides. Electron transfer without dissociation produces [M + 2H]+* ions, which appear to be less kinetically stable than the proton transfer [M + H]+ product. When subjected to collision-induced dissociation (CID), the [M + 2H]+* ions fragment to give products that were also observed as dissociation products during the electron transfer reaction. However, not all dissociation channels noted in the electron transfer reaction were observed in the CID of the [M + 2H]+* ions. The charge state of the peptide has a significant effect on both the extent of electron transfer dissociation observed and the variety of dissociation products, with higher charge states giving more of each.     

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> by APCI-MS

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH₂Cl₂). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n−Bu)₄N⁺X⁻ (X⁻ = Cl⁻, NO₃⁻, Br⁻, I⁻). Solutions of receptors and anions in CH₂Cl₂ were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M+X]⁻, (M=1–3, X⁻=Cl⁻, NO₃⁻, Br⁻, I⁻) were observed in negative mode APCI-MS along with the deprotonated receptors [M−H]⁻. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.     

A new method of synthesis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

A new method of synthesis of the B₃H₈⁻ anion has been suggested. The method uses the reaction of some metal halides (CuCl, SnCl₂, CrCl₃, PbF₂, PbCl₂, PbBr₂, and BiCl₃) with sodium tetrahydroborate. It is characterized by high (up to quantitative) yields and simplicity of isolation of the target products ((n-C₄H₉)₄N)[B₃H₈] and Cs[B₃H₈].     

The ESCA analysis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

Compounds [Et₄N]₂B₃H₈ and CsB₃H₈ are studied using the ESCA method. The results of analysis of the B1s electron spectra and estimation of the effective charge differences in [Et₄N]₂B₃H₈ are compared to the data of theoretical calculations of the B₃H₈⁻ anion.     

Chemical Bonding in the Complexes XeF<Stack><Subscript>5</Subscript><Superscript>+</Superscript></Stack>XF<Stack><Subscript>6</Subscript><Superscript>−</Superscript></Stack> (X = P,As, Sb,and Bi)

Ab initio quantum-chemical calculations of the complexes XeF ₅ ⁺ XF ₆ ^? (X = P, As, Sb, and Bi) were performed with the use of relativistic pseudopotentials for heavy atoms and full-electron basis sets. The chemical bonds were characterized by the parameters of critical points (electron density, its Laplacian, total electron energy, and its kinetic and potential components). It was demonstrated that the interaction between the XeF ₅ ⁺ cation and the XF ₆ ^? anion in XeF ₅ ⁺ XF ₆ ^? follows a key-lock scheme involving directed interactions of bridging fluorine atoms F_b → Xe and that the structuring function of the lone electron pair of the Xe atom is to compensate the destabilizing electrostatic interaction between the Xe and X atoms bearing excess positive charges.     

Kinetics of electroreduction of S<Subscript>2</Subscript>O<Stack><Subscript>8</Subscript><Superscript>2−</Superscript></Stack> anions on mechanically renewable silver electrode

The kinetics of electroreduction of peroxodisulfate anions on a mechanically renewed silver electrode is studied by voltammetric and impedance methods. Impedance diagrams obtained in the region of negatively charged metal surface are successfully modeled by the equivalent circuit formed by the solution resistance and also the reaction resistance connected in parallel with the constant-phase element substituted for the double layer capacitance. The analysis of experimental data carried out in terms of this circuit and their comparison with the literature data makes it possible to assume that the reduction kinetics of S₂O ₈ ^2? anions on this electrode can be adequately described in the framework of the phenomenological theory of slow discharge. The reasons for deviation of the literature data on the kinetics of this reaction on polycrystalline Ag electrode from the relationships following from the slow discharge theory are put forward and substantiated.     

Study on nonlinear kinetic and thermodynamics of oscillating reaction of amino Acid-BrO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>-Mn<Superscript>2+</Superscript>-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-acetone system

With the help of the kinetic parameters (the rate constant (k _in k _p) and the apparent activation energy (E _in E _p) of the oscillatory induction period and oscillation period) of the oscillating reaction using thirteen amino acids, leucine (Leu), threonine (Thr), arginine (Arg), lysine (Lys), histidine (His), alanine (Ala), glutamine (Glu), glycine (Gly), methionine (Met), cystine (Cys), tryptophan (Trp), serine (Ser) and tyrosine (Tyr), as organic substrates in amino acid-BrO₃⁻-Mn²⁺-H₂SO₄-acetone system, then based on the Oregonator model and the thermodynamics theory on irreversible process, the thermodynamic function (ΔH _in, ΔG _in, ΔS _in and ΔH _p, ΔG _p, ΔS _p) of these oscillating system are studied. The results indicate the entropy ΔS of these oscillating reaction are negative, thereby it is proved that the oscillating reaction is a noequilibrium system with dissipation structure in agreement with the character of the oscillating reaction from disorder to order in irreversible thermodynamics. These are satisfactorily to explain the experimental phenomena.     

Enthalpy of solution of VOCl<Subscript>3</Subscript> in dilute sodium hydroxide solutions and the standard enthalpy of formation of the HVO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack> ion

The calorimetric enthalpies of solution of liquid vanadium oxytrichloride in dilute sodium hydroxide solutions were measured at 298.15 K and ionic strengths I = 0.5, 1.0, or 1.5 (NaClO₄). The standard enthalpy of formation of the HVO ₄ ^2? ion was calculated from the measured data.     

Study on the thermal behavior of the complexes of the type [PdX<Subscript>2</Subscript>(tdmPz)] (X = Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, I<Superscript>−</Superscript>, SCN<Superscript>−</Superscript>)

Four new mononuclear Pd(II) complexes of the type [PdX₂(tdmPz)] {X = Cl⁻ (1); Br⁻ (2); I⁻ (3); SCN⁻ (4); tdmPz = 1-thiocarbamoyl-3,5-dimethylpyrazole} have been synthesized and characterized by elemental analysis, IR spectroscopy, ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 1–4 has been investigated by means of thermogravimetry (TG) and differential thermal analysis (DTA). From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 3 < 4 ≡ 2 < 1. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Synthesis and physicochemical study of the PMo<Subscript>11</Subscript>(TiO)O<Stack><Subscript>39</Subscript><Superscript>5−</Superscript></Stack> heteropolyanion

Procedures were developed for the synthesis of the guanidinium (Gua) and tetrabutylammonium (TBA) salts of 11-molybdotitano(IV)phosphate heteropolyanion (MTPH) from solutions with the stoichiometric ratio P: Mo = 1: 11 and in excess of titanium(IV) ions, Ti: P ≥ 1.5, at pH 1.85–1.90. MTPH was isolated as the (Gua)₅PMo₁₁(TiO)O₃₉ and (TBA)₅PMo₁₁(TiO)O₃₉ salts. The composition and formula of MTPH were established by chemical analysis, electronic absorption spectroscopy in the visible region of the oxidized and reduced MTPH forms, IR spectroscopy, and ³¹P NMR. H₅PMo₁₁(TiO)O₃₉, obtained by ion exchange of the Gua salt in an aqueous-organic medium, is a strong pentabasic acid. MTPH reacts with H₂O₂ to form a peroxo complex with limited stability in an aqueous solution. In aqueous-organic media, the peroxo complex is more stable. In acetonitrile, MTPH persists for several days.     

Isothermal solubility diagram of the 2Na<Superscript>+</Superscript>,Mg<Superscript>2+</Superscript>‖2Cl<Superscript>−</Superscript>, 2ClO<Stack><Subscript>3</Subscript><Superscript>‒</Superscript></Stack>-H<Subscript>2</Subscript>O quaternary system at 20 and 100°C

The solubility in the 2Na⁺,Mg²⁺‖2Cl⁻, 2ClO₃⁻-H₂O system was studied at 20 and 100°C and the solubility diagrams were plotted. New compounds were not found to form in the title quaternary reciprocal system. The sodium chloride field was observed to expand with rising temperature.     

Preparation of nano-SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>/TiO<Subscript>2</Subscript> catalyst and its application in esterification of sebacic acid with 2-ethyl hexanol

A pure anatase phase nano-SO₄²⁻ /TiO₂ catalysts were synthesized and their catalytic activities were tested. Nano-SO₄²⁻/TiO₂ shows high activity and effective re-usable when used as basic catalysts for the synthesis of dioctyl sebacate.     

Mercury complex [(HOCH<Subscript>2</Subscript>)<Subscript>3</Subscript>CNH<Subscript>3</Subscript>]<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> [HgI<Subscript>4</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

The complex [(HOCH₂)₃CNH₃] ₂ ⁺ [HgI₄]^2? (I) was synthesized by reacting (trioxymethyl)methylammonium iodide with mercury dioide (2: 1 mol/mol) in acetone. X-ray crystallography shows that the complex consists of two types of crystallographically independent [(HOCH₂)₃CNH₃]⁺ cations and tetrahedral anions [HgI₄]^2? (IHgI, 106.49(2)°–113.99(4)°; Hg-I, 2.7849(8)-2.8105(8) Å. [(HOCH₂)₃CNH₃]⁺ cations are linked via hydrogen bonds O…H-N and O-H…N (O…N, 2.84–2.92 Å) to form polymer chains, which are cross-linked with one another via anions (I…H, 2.81, 2.82 Å).     

A study of the hydrolysis of ZrF<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack> and the structure of intermediate hydrolysis products by <Superscript>19</Superscript>F and <Superscript>91</Superscript>Zr NMR in the 9.4 T field

The high-field ¹⁹F and ⁹¹Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate ZrF₆²⁻ in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only ZrF₆²⁻ and F⁻ ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ([F₅Zr-OO-ZrF₅]⁴⁻ dimer) was detected. The dimer structure is confirmed by ¹⁹F and ⁹¹Zr NMR. In high fields (¹⁹F NMR frequency > 200 MHz), the fluorine exchange between ZrF₆²⁻ and F⁻ is slow in the ¹⁹F NMR scale and has a multisite character.     

Structures of the complex ions [CuCl<Subscript>4</Subscript>]<Superscript>2−</Superscript> and [CuCl<Subscript>5</Subscript>]<Superscript>3−</Superscript>

The electronic structures of the complex ions [CuCl₄]^2? and [CuCl₅]^3? were analyzed in terms of the extended angular overlap model (AOM) with consideration to sd and pd mixing. The total antibonding orbital energies of these ions show no anomalies in the transition from a tetrahedron to a planar square [CuCl₄]^2? and from a trigonal bipyramid to a tetragonal pyramid [CuCl₅]^3?. Presumably, the existence of numerous intermediate forms of these complexes is mainly due to the packing effects rather than the electronic factors.     

Experimental Determination of the Isotherm at 15°C of the System Mg<Superscript>2+</Superscript>/Cl<Superscript>−</Superscript>, SO<Subscript>4</Subscript><Superscript>2</Superscript>–H<Subscript>2</Subscript>O

Summary.  The diagram of the ternary system Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO₄·6H₂O, MgSO₄·7H₂O, and MgCl₂·6H₂O. The solubility field of MgSO₄·7H₂O is important whereas those of MgSO₄·6H₂O and MgCl₂·6H₂O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO₄:MgCl₂=2.73:33.80 and MgSO₄: MgCl₂=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C.  Corresponding author. E-mail: ariguib@planet.tn Received October 16, 2002; accepted (revised) December 3, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70^th birthday     

Ion-selective sensors for determining Au(CN)<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> with membranes based on the ionic liquid tetradecylphosphonium dicyanoaurate

A polymeric membrane for an ion-selective electrode is proposed on the basis of supramolecular systems including a polymeric compound (polyvinyl chloride, PVC) and an ionophore (ionic liquid tetradecylphosphonium dicyanoaurate) in which ionic liquid is simultaneously used as a PVC plasticizer. The selectivity, linear response range, and potential stability of ion-selective electrodes with the optimum membrane composition are measured. The detection limit for Au(I) with the developed electrode is 4.5 × 10^?7 M.     

Comparison of Magnetic Properties between Spin Singlet and Triplet Li<Subscript>3</Subscript>Al<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Clusters

With a second-order Møller–Plesset perturbation theory and Hartree–Fock nuclear magnetic resonance calculations, we investigated the magnetic properties of spin singlet and triplet Li₃Al ₄ ^? clusters. The obtained gauge-independent atomic orbital magnetic shielding tensors confirm the paramagnetism of singlet Li₃Al ₄ ^? and diamagnetism of the triplet. The planar rings composed of four aluminum atoms make the magnetic properties of Li₃Al ₄ ^? clusters versatile. The localized molecular orbital, low symmetry of geometric conformation and narrow gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are found to correlate with the paramagnetism of singlet Li₃Al ₄ ^? . The origin of the paramagnetism is explained. In triplet Li₃Al ₄ ^? , the two outmost orbitals are degenerate, causing a conversion from the paramagnetism to diamagnetism.