Comparison study of adsorption of Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ions from dimethyl formamide on In-Ga and Tl-Ga electrodes

The adsorption of Cl⁻, Br⁻, and I⁻ ions on the renewable liquid In-Ga and Tl-Ga electrodes from 0.1 M solutions in dimethyl formamide (DMF) is investigated by using the method of differential capacitance measurements. The results are compared with similar data obtained on Hg and Ga electrodes in DMF and with the corresponding data obtained in acetonitrile (AN). It is shown that, in DMF, the adsorption parameters and the series of surface activity of halide ions (Hal⁻) significantly depend on the metal nature. In contrast to Hg electrode, on which the surface activity of halide ions increases in the series: Cl⁻ < Br⁻ < I⁻, on In-Ga, as well as on the Ga electrode, it varies in the reverse order: I⁻ < Br⁻ < Cl⁻, whereas on the Tl-Ga electrode, partially reversed series of surface activity is observed: Br⁻ < I⁻ < Cl⁻. The results are explained within the framework of Andersen-Bockris model. An analysis of experimental results leads to the following qualitative conclusions: (1) on the In-Ga and Tl-Ga electrodes, as well as on Ga electrode, free energy of metal-Hal⁻ interaction ( $ \Delta G_{_{M - Hal^ - } } $ \Delta G_{_{M - Hal^ - } } ) increases in series I⁻ < Br⁻ < Cl⁻; (2) for Cl⁻, Br⁻, and I⁻, $ \Delta G_{_{M - Hal^ - } } $ \Delta G_{_{M - Hal^ - } } ) grows in series Tl-Ga < In-Ga < Ga; (3) an absolute magnitude of $ \Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } } $ \Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } } (Hal₁⁻, and Hal₂⁻ are any ions of Cl⁻, Br⁻, and I⁻) increases in series Hg < Tl-Ga < In-Ga < Ga; (4) the metal-DMF chemisorption interaction is much stronger than the metal-AN interaction and increases in series Tl-Ga < In-Ga < Ga.     

Structural transformation of silver nanoprisms in aqueous solution initiated by Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ions: electrochemical mechanism

It has been found that halide ions (Cl^–, Br^–, and I^–) in aqueous solution initiate structural transformation of silver trigonal prisms (20?50 nm in size) in the sequence prism ? disc ? sphere. It has been demonstrated that the change in structure is caused by the formation of poorly soluble silver salts on nanoprisms and occurs by the electrochemical mechanism. The efficiency of the process is dictated by the nature of the halide ion.     

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.     

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.     

Counterion effects on the isotopic properties of the Cl<Superscript>−</Superscript> and Li<Superscript>+</Superscript> ions in aqueous solutions

The reduced partition function ratios between isotopic forms (β-factors) were calculated by the ab initio RHF/6-311++G**(3df, 3p) and MP2/6-311++G**(3df, 3p) quantum-chemical methods for hydrated chloride ion and ion pair hydrates NaCl·nH₂O and LiOH · nH₂O. The influence of the Na⁺ cation on the β-factor value and the chlorine isotope separation factor in the precipitation of NaCl from concentrated aqueous solutions was found to be substantial. At the same time, the presence of OH^? counterions had no noticeable effect on the β-factor of the hydrated Li⁺ cation.     

Pulse radiolysis study of the oxidation of the I<Superscript>−</Superscript> ions with the radical anions Br<Subscript>2</Subscript><Superscript>·−</Superscript> in an aqueous solution: formation and properties of the radical anion BrI<Superscript>·−</Superscript>

The radiation chemical redox transformations in solutions of bromides in the presence of minor additives of iodides were studied by pulse radiolysis. The change in the concentrations of the Br⁻ and I⁻ ions changes the ratio of the formed short-lived radical anions Br₂ ^·−, BrI^·−, and I₂ ^·−. The spectrum of the mixed radical anion BrI^·− contains a broad optical band at 370 nm with ɛ₃₇₀ = 9650 L mol⁻¹ cm⁻¹. The reduction potential of the BrI^·−/Br⁻, I⁻ pair is 1.25 V. The rate constants for the forward and backward reactions Br₂ ^·− + I⁻ ⇌ BrI^·− + Br⁻ are k _f = 4.3·10⁹ and k _r = 1.0·10⁵ L mol⁻¹ s⁻¹, respectively; for the reactions BrI^·− ⇌ Br⁻ + I^·, k _f = 5.7·10⁸ s⁻¹ and k _r = 1.0·10¹⁰ L mol⁻¹ s⁻¹. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1787–1792, September, 2008.     

Computational studies of the interactions of I<Superscript>−</Superscript> and I<Subscript>3</Subscript><Superscript>−</Superscript> with TiO<Subscript>2</Subscript> clusters: implications for dye-sensitized solar cells

Abstract  

First principle density-functional theory calculations have been carried out on the interaction of I⁻ and I₃ ⁻ with TiO₂ anatase surfaces, modeled by finite clusters that range in size from 48 to 180 atoms. The total energy per TiO₂ unit and the HOMO-LUMO gaps decrease with increasing the size of the clusters. Both redox species (I⁻ and I₃ ⁻) are strongly adsorbed on the TiO₂ surface with the adsorbtion of I⁻ being stronger. Adsorption of triiodide leads to its dissociation. The positions of the HOMO and LUMO of the adsorbed systems shift negatively from their respective cluster values. Solvation effects have been modeled using the CPCM model. Introducing solvent reduces the shifting of HOMO and LUMO. Implications for dye-sensitized solar cells (DSSC) are discussed. Both the HOMO-LUMO shifting and the strong adsorption might affect the performance of the cell.     

Ionic complexes simultaneously containing fullerene anions and coordination structures of metal phthalocyanines with I<Superscript>−</Superscript> and EtS<Superscript>−</Superscript> anions

The ionic complexes simultaneously containing negatively charged coordination structures of metal phthalocyanines and fullerene anions, viz., {Mn^IIPc(CH₃CH₂S^?) _x ·(I^?)_1?x }·(C₆₀ ^·?)· ·(PMDAE⁺)₂·C₆H₄Cl₂ (PMDAE is N,N,N′,N′,N′-pentamethyldiaminoethane, x = 0.87, 1) and {Zn^IIPc(CH₃CH₂S^?)_y·(I^?)_1?y }₂·(C₆₀ ^?)₂·(PMDAE⁺)₄·(C₆H₄Cl₂) (y = 0.5, 2) were synthesized. The both compounds were obtained as single crystals, which made it possible to study their crystal structures. In complex 1, the fullerene radical anions form honeycomb-like layers in which each fullerene has three neighbors with center-to-center interfullerene distances of 10.13–10.29 Å. Rather long distances between the C₆₀ ^·? radical anions results in the retention of monomeric C₆₀ ^·? in this complex down to the temperature of 110(2) K. In complex 2, fullerenes form dimers (C₆₀ ^?)₂ bonded by one C-C bond. The dimers are packed in corrugated honeycomb-like layers with interfullerene center-to-center distances of 9.90–10.11 Å. Manganese(II) and zinc(II) phthalocyanines coordinate iodide and ethanethiolate anions to the central metal atom to form unusual negatively charged coordination structures M^IIPc(An^?) (An^? is anion) packed in dimers {M^IIPc(An^?)}₂ with a short distance between the phthalocyanine planes (3.14 Å in 1 and 3.27 Å in 2). The pthalocyanine dimers also form layers with the PMDAE⁺ cations, and these layers alternate with the fullerene layers. The packing of spherical fullerenes with planar phthalocyanine molecules is attained by the insertion of fullerenes between the phenylene groups of phthalocyanines. The π-π-interactions of the porphyrin macrocycle with five- or six-membered fullerene rings are characteristic of the earlier studied ionic porphyrin and fullerene complexes. Such interactions are not observed for ionic complexes 1 and 2.     

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     

Adsorption of Cl<Superscript>−</Superscript> ions on γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> oxide from nitrate solutions

The adsorption of chloride ions on γ-Fe₂O₃ oxide (maggemite) from nitrate solution is studied using the method of potentiometric titration and an ion-selective electrode. The specific character of adsorption is determined. It is shown that the maggemite surface coverage with Cl^? ions increases with increasing concentration of ions in the solution, decreasing pH value, and increasing potential. The adsorbability of ions changes drastically in the pH range about pH₀ (γ-Fe₂O₃)6.2. It is found that the adsorption of chloride ions from neutral nitrate solution exponentially increases in the potential range from 0.1 to 1.0 V. The type of adsorption isotherm and the adsorption parameters are determined. It is found that, in the absence of external polarization, the concentration dependences of adsorption of Cl^? ions are complex-shaped, and their initial portions are described by the Langmuir isotherm. Further increase of adsorption is explained by the penetration of Cl^? ions inwards the oxide.     

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.     

Mean force potential of interaction between Na<Superscript>+</Superscript> and Cl<Superscript>−</Superscript> ions in planar nanopores in contact with water under pressure

The mean force potential (MFP) of interaction between counterions Na⁺ and Cl^? in a planar nanopore with structureless hydrophobic walls is calculated via computer simulation under the condition that the nanopore is in contact with water at an external pressure that exceeds the saturation pressure but remains insufficient to fill the nanopore with water. For a nanopore with a liquid phase, the MFP dependence on the interionic distance indicates the dissociation of an ion pair into two hydrated ions in a nanopore that is not completely filled with water. Fluctuations in the number of water molecules drawn into the interionic space decisively influence the dissociation. The attraction between counterions, averaged over thermal fluctuations, depends largely on the pore width and grows as the shielding of the ions’ electric field by water molecules in a narrow pore diminishes. The contributions from energy and entropy to the free energy of hydration are analyzed.     

Interactions between AuCl<Subscript>4</Subscript><Superscript>−</Superscript> and CTA<Superscript>+</Superscript> ions in water

The solubility of hexadecyltrimethylammonium tetrachloroaurate (CTA·AuCl₄) in water was measured at different temperatures of 288.2, 293.2, 298.2, 303.2, and 308.2 K. The enthalpy change associated with the formation of the CTA·AuCl₄ precipitate was estimated on the basis of the van’t Hoff equation and was found to be −42.5 ± 2.8 kJ mol⁻¹ at 298.2 K. The calorimetric enthalpy change for the CTA·AuCl₄ precipitate formation was directly determined by isothermal titration calorimetry performed at 298.2 K and was found to agree well with that estimated from the van’t Hoff equation.     

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..     

Nucleation of water vapor on Na<Superscript>+</Superscript>Cl<Superscript>−</Superscript> ion pairs: Computer simulation

The Monte Carlo method is used to calculate the free energy, entropy, and work of water cluster formation in the field of Na⁺Cl⁻ ion pairs. A detailed model is used that allows for polarization and covalent many-particle interactions, as well as the effects of ion charge reversal. The model is matched to the experimental data on the free energy of ion hydration and the results of the quantum-chemical calculations of stable configurations. The hydration leads to the cleavage of an ion pair in a molecular cluster after approximately ten water molecules are captured. As vapor molecules are added, the stable interion distance monotonically elongates. The low free energy barrier separating the dissociated and nondissociated states of the ion pair in an equilibrium cluster does not hinders the reversible spontaneous transitions between the states, which are responsible for strong fluctuations and the instability of the system. Unlike hydroxonium-containing ion pairs, the formation of long-lived metastable states of hydrated Na⁺Cl⁻ pairs is impossible.     

Electrical conductivity of potassium titanyl phosphate KTiOPO<Subscript>4</Subscript> pure crystals and those doped with Na<Superscript>+</Superscript>, Rb<Superscript>+</Superscript>, and F<Superscript>–</Superscript> ions

KTiOPO₄ crystals, both pure and doped with rubidium Rb⁺ and fluorine F^– ions, were grown in temperature range from 1060 to 846°С from salt solvent containing potassium metaphosphate КРО₃ and potassium orthophosphate К3РО₄ by using a Czochralski modified method. Potassium–sodium titanyl phosphate crystals were obtained from KTiOPO₄ crystals by the potassium isomorphic replacement with sodium; to this purpose, sodium chemical diffusion from NaNO₃ melt was used. Their ionic conductivity was studied by the electrochemical impedance spectroscopy method. The KTiOPO₄ crystal doping with rubidium and sodium ions was shown to lower the conductivity, whereas the doping with fluorine ions results in increased conductivity.     

Comparison of the specific adsorption of sulfate (HSO<Subscript>4</Subscript><Superscript>−</Superscript>) ions on Cr and Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>

The specific adsorption of sulfate ions on powdered Cr was studied by a radiotracer technique using ³⁵S-labeled sulfuric acid in low concentration (c<10^–3 mol dm^–3) in the presence of a large excess of perchlorate supporting electrolyte. The pH and concentration dependence were determined. On the basis of a comparison of the results obtained for Cr₂O₃ and Cr, it can be assumed that, similar to other metals, the overall sorption behavior of Cr is determined by the protective oxide film present on the surface.     

Structure and stability of endohedral complexes <Superscript>4/2</Superscript>X@(HAlNH)<Subscript>2</Subscript> (X = N,P, As,C<Superscript>−</Superscript>, Si<Superscript>−</Superscript>)

The structures of a closo-hedral cluster (HAlNH)₁₂ and endohedral complexes ^4/2X@(HAlNH)₁₂ (X = N, P, As, C⁻, Si⁻) are studied by density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency (ν₁), energetic parameters, magnetic shielding constants (σ), and nucleus independent chemical shifts (NICSs) are discussed. It is found that all guest species are minima at the cage center. Inclusion energies (ΔE _inc) of all species are negative except those of ⁴N and ^4/2P. In all species, the endohedral quartet states (⁴X) are energetically less favorable than their doublet states (²X). The calculations predict that caged X states only donate <0.50 e to the cage and preserve their unencapsulated ground states.     

A theoretical study of the interaction between [HB≡CH]<Superscript>−</Superscript>, [H<Subscript>2</Subscript>B=CH<Subscript>2</Subscript>]<Superscript>−</Superscript>, and boratabenzene anions with alkali and alkaline earth metals: properties and structures

The nature of [HB≡CH]⁻, [H₂B=CH₂]⁻, and boratabenzene interactions with alkaline and alkaline earth metals are studied by ab initio calculations. The interaction energies are calculated at the B3LYP/6-311++G(d,p) level. The calculations suggest that the cation size and charge are two influential factors that affect the nature of the interaction. AIM and NBO analyses of the complexes indicate that the variation of densities and the extent of charge transfers upon complexation correlate well with the obtained interaction energies.