Nuclear magnetic resonance study of aluminum chloride-n-Butylpyridinium chloride melts

High resolution proton and ¹³C-NMR measurements were used to follow the variation of the n-butylpyridinium (BP⁺) cation spectra in BP⁺Cl^?AlCl₃ molten mixtures. The mole fraction of AlCl₃ was varied between 0.45 and 0.60. It was found that chemical shifts and proton coupling constants are significantly affected by the BP⁺-Cl^? and BP⁺ -AlCl^?₄ associations. Analysis of the NMR results shows that in the melts the ionic association into ion pairs is essentially quantitative. Lithium-7 NMR of BPCl-AlCl₃-LiCl melt shows that when the mole-fraction of AlCl₃ is < 0.50 (basic melt) LiCl₂^? ion is formed, while in the acidic melts the Li⁺ ion probably interacts with two AlCl₄^? ions to form LiAl₂Cl^?₈ ion.     

Bis(2‐chloro‐N‐methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^?·I₃^?, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.     

AlCl3 · 2NH3 – eine Verbindung mit der Kristallstruktur eines Tetraammindichloroaluminium-tetrachloroaluminats – [AlCl2(NH3)4]+[AlCl4]−

ACl₃ · 2NH₃ – a Compound with the Crystal Structure of a Tetraammine Dichloroaluminiumtetrachloroaluminate – [AlCl₂(NH₃)₄]⁺[AlCl₄]^? Ammoniates of aluminiumchloride AlCl₃ · xNH₃ are in discussion as starting materials for the synthesis of aluminiumnitride. Therefore the reactions of melts of monoamminealuminiumchloride with ammonia were investigated. They react at 150°C within 10 min with one mole of ammonia to the diammoniate, [AlCl₂(NH₃)₄]⁺[AlCl₄]^?. The pure compound can be obtained by sublimation at 200°C in vacuumline apparatus. X-ray structure determination on [AlCl₂(NH₃)₄]⁺[AlCl₄]^? was carried out: see “Inhaltsübersicht”.     

Ternary diffusion with charged-complex formation in aqueous I2+NaI and I2+KI solutions

Diaphragm cells have been used to measure ternary diffusion coefficients for I₂+NaI and I₂+KI in aqueous solution at 25°C. Although most of the iodine molecules are bound to iodide ions and are transported as the triiodide species [I₂(aq)+I^–(aq)=I ₃ ^– (aq)], diffusion of the iodide salts produces relatively small countercurrent coupled flows of the iodine component. The ternary diffusivity of the iodine component in the solutions is 10 to 20% larger than the diffusivity of the triiodide species. This behavior can be understood by considering electrostatic coupling of the ionic flows. The diffusion equations for I₂+NaI and I₂+KI components are reformulated in terns of NaI₃+NaI and KI₃+KI mixed electrolyte components.     

Crystal structures of triphenylamylphosphonium iodide [Ph<Subscript>3</Subscript>AmP]I and triphenylamylphosphonium tetraiodide [Ph<Subscript>3</Subscript>AmP]I<Subscript>4</Subscript>

By reaction of triphenylamylphosphonium iodide [Ph₃AmP]I (I) with antimony iodide in acetone, triphenylamylphosphonium tetraiodide [Ph₃AmP]₂I₄ (II) was synthesized. Crystals of I consist of triphenylamylphosphonium cations and iodine anions. Compound II contains two types of tetrahedral triphenylamylphosphonium cations, iodine anions, and [I₃]^? anions. Atoms P have a distorted tetrahedral coordination in cations I and II (the CPC angles are 106.48(12)°–111.25(12)° in I and 107.05(9)°–112.62(10)° in II). The centrosymmetric trinuclear [I₃]^? anion in II is nearly linear (the I(2)I(1)I(3) angle is 178.65°, the I(1)–I(2) and I(1)–I(3) bond lengths are 2.8925(2) Å and 2.9281(2) Å, respectively).     

Structure of iodide ion arrays in iodinated nylon 6 and the chain orientation induced by iodine in nylon 6 films

Two species of iodide ions (I₃^? and I₅^?) are found in iodine—nylon 6 complexes. Orientation of I₅^? arrays (most likely I₂/I₃^? complex) along the polymer chain and I₃^? ions perpendicular to the chain axis in uniaxially drawn films and in films with planar orientation suggests that there is and intrinsic relation between the direction of iodide ion arrays and nylon 6 chains. When an unoriented film of nylon 6 in the amorphous or the α crystalline form is treated with an aqueous solution of iodine—potassium iodide, the I₃^? species in the resulting iodine—nylon complex lie in planes parallel to the surface of the film, and I₂/I₃^? units are oriented normal to the surface of the film. The γ form obtained by desorbing the iodine from this complex shows considerable uniaxial rientation with the nylon chains oriented perpendicular to the plane of the film; this orientation is maintained during the γ to α transition. It is proposed that the iodine-induced orientation of the nylon 6 chains is due to the nucleating effects of the iodide ion species as the iodine diffuses unidirectionally into the film.     

Ring-disk electrode studies of the open-circuit dissolution of iodine films formed during the anodic oxidation of iodide on platinum

The open-circuit behavior of iodine films formed on platinum by electrooxidation of iodide was studied at rotating disk and rotating ring-disk electrodes. The potential transient and ring current transient at open circuit for c_I^?>0.012 M can be explained by assuming: (1) convective-diffusion controlled dissolution of the film; (2) establishment of the I₂+I^?→ I₃^? equilibrium; (3) establishment of the I₂ (solid) →I₂ (solution) equilibrium. The behavior at lower concentrations of c_I^? suggests that convective-diffusion control is absent.     

Polyiodide composition in poly(vinyl acetate)-iodine-iodide complex

Polyiodide formed by complexation of poly(vinyl acetate) (PVAc) with iodine in the presence of iodide has been investigated by chemical analysis and resonance Raman spectrophotometry. When PVAc films were immersed in iodide-iodine aqueous solutions which had different ratios of iodide to iodine concentration [I^?]/[I₂], the complex films exhibited tremendous variations of swelling degree, despite the relatively small change in the amount of bound iodine. From a quantitative chemical analysis, the composition of polyiodide bound to PVAc was found to be 1.01 ± 0.035 in the molar ratio of iodide to iodine irrespective of the composition of the iodide-iodine aqueous solution ([I^?]/[I₂] = 2–500). The polyiodide formed in PVAc-iodine-iodide complex was therefore inferred to be (I₃^?)_n. Resonance Raman spectra obtained on PVAc-iodine-iodide complexes were also identical to those of the benzamide-iodine complex, in which the polyiodide consists of (I₃^?)_n, consistent with the result from chemical analysis.     

β‐Pyridinium di­chloro­iodide

The β modification of pyridinium di­chloro­iodide, C₅H₆N⁺·Cl₂I^?, was obtained as yellow crystals by the reaction of (C₅NH₅)AuCl₃, C₅H₆N⁺·Cl^? and I₂ in a vacuum‐sealed ampoule. The di­chloro­iodide ion is nearly symmetric and linear with I—Cl bond lengths of 2.544 (3) and 2.550 (3) Å and a Cl—I—Cl angle of 179.68 (12)°.     

Analysis of low-level 129I in brine using accelerator mass spectrometry

An improved solvent extraction procedure for iodine separation from brine samples has been applied at Xi’an Accelerator Mass Spectrometry (AMS) center. Oil in the brine sample has to be removed to avoid appearance of the third phase during solvent extraction and to improve the chemical yield of iodine. The small amount of oil remained in the water phase was first removed by phase separation through settling down sufficiently based on their immiscibility, and then by filtration through a cellulose filter, on which oil was absorbed and removed. After oil removed, extraction recovery of iodine could achieve more than 90 %. The sodium bisulfite as an effective reductant should be added before acidification to avoid loss of iodine by formation of I₂ in sample via reaction of iodate and iodide at pH 1–2, and then pH was adjusted to 1–2 to reduce the iodate to iodide followed by oxidation of iodide to I₂ and solvent extraction to separate all inorganic iodine. As a pre-nuclear era sample, ¹²⁹I/¹²⁷I ratio in brine is normally more than two orders of magnitude lower than that in present surface environmental samples, so prevention of cross-contamination and memory effect in apparatus during processing procedure are very critical for obtaining reliable results, and monitoring the procedure blank is very important for analytical quality of ¹²⁹I. The ¹²⁹I/¹²⁷I isotopic ratio in the brine samples and procedure blank of iodine reagents were measured to be (1.9–2.7) × 10^?13 and 2.08 × 10^?13, respectively, 3–4 orders of magnitudes lower than that in environmental samples in Xi’an, and the result of procedure blank is in the same level as the previous experiments in past 3 years, indicating contamination is not observed in our method.     

Speciation analysis of iodine and bromine at picogram-per-gram levels in polar ice

Iodine and bromine species participate in key atmospheric reactions including the formation of cloud condensation nuclei and ozone depletion. We present a novel method coupling a high-performance liquid chromatography with ion chromatography and inductively coupled plasma mass spectrometry, which allows the determination of iodine (I) and bromine (Br) species (IO ₃ ^? , I^?, Br^?, BrO ₃ ^? ) at the picogram-per-gram levels presents in Antarctic ice. Chromatographic separation was achieved using an IONPAC® AS16 Analytical Column with NaOH as eluent. Detection limits for I and Br species were 5 to 9 pg g^?1 with an uncertainty of less than 2.5% for all considered species. Inorganic iodine and bromine species have been determined in Antarctic ice core samples, with concentrations close to the detection limits for iodine species, and approximately 150 pg g^?1 for Br^?. Although iodate (IO ₃ ^? ) is the most abundant iodine species in the atmosphere, only the much rarer iodide (I^?) species was present in Antarctic Holocene ice. Bromine was found to be present in Antarctic ice as Br^?.     

Untersuchungen an Polyhalogeniden. XVII. Darstellung und Kristallstruktur von Urotropiniumtriiodid,UrHI3

Studies on Polyhalides. 17. Preparation and Crystal Structure of Urotropinium Triiodide, UrHI₃ Urotropinium triiodide C₆H₁₃N₄I₃ is formed by the reaction of equimolar amounts of urotropinium iodide and iodine in ^tBuOH as red-brown cube-like crystals melting at 402 K under decomposition. The compound crystallizes monoclinically in the space group P2₁/c with a = 952.0(3) pm, b = 1 160.2(6) pm, c = 1 149.9(4) pm, β = 92.22(3)° and Z = 4. The till now not described crystal structure (R = 0.027 for 1 860 observed reflexes) contains urotropinium ions UrH⁺ and slightly distorted triiodide ions I₃^?(d(I—I) = 292.3(1), 294.1(1) pm, φ(I—I—I) = 178.27(2)°) which are linked to ion pairs by a rather short contact (d(I …? I) = 389.0(1) pm, φ(I—I …? I) = 149.12(2)°).     

Electrochemical studies of iodine in an aluminium chloride-butylpyridinium chloride ionic liquid part II. Neutral and basic solvent composition

The electrochemical behavior of iodine in an ambient temperature molten salt system, aluminum chloride-N-(1-butyl)pyridinium chloride (BuPyCl), have been studied in basic (excess BuPyCl) and neutral (1.0:1.0 AlCl₃: BuPyCI mole ratio) melt compositions. Acid-base interactions of iodine in different oxidation states with the ionic solvent are observed. High stability of triiodide ion in neutral butylpyridinium tetrachloroaluminate indicates relatively weak intermolecular interactions in this solvent. In basic solutions polyhalogen equilibria involving iodine in different oxidation states and chloride ions are established. In iodine and tetraethylammonium triiodide solutions a mixture of ICI₂^?, I₂Cl^?, I₃^? and I^? ions forms. The formation constants of I₂Cl^? and I₃^? and the equilibrium constant for I₂Cl^? disproportionation are estimated.     

The Photochemistry of Ch3I in Various Matrices at Low Temperature

The photodissociation of methyl iodide in various matrices at low temperature was studied. The observed Raman spectra excited by 514.5 nm laser radiation showed that there were two different photolytically produced iodine species isolated in the matrices after illumination by a medium pressure mercury lamp. One species which was dominant at lower iodine concentrations and exhibited a progression with an ωe of 201 cm^?1, belonged to the matrix isolated iodine monomer (I₂). The other species, which was dominant at higher iodine concentrations with an ω_e of approximately 180 cm^?1, belonged to the iodine aggregate ((I₂)_n). Five progressions of resonance Raman or resonance fluorescence of these two species were also observed in the other matrices. The iodine aggregate in the methyl iodide matrix at 77 K was formed in a crystalline structure, while the photolytically generated iodine aggregate from CH₃I/Ar (2/3) matrix at 10 K, after illumination with a mercury lamp, was in amorphous form. The rearrangement of photolytically produced iodine aggregate in methyl iodide matrix was observed as a function of the duration of illumination. Local heating effects of the laser radiation might induce the iodine monomer to aggregate in matrices. The photodissociation mechanism of methyl iodide in matrices is also proposed.     

Reactions of bis-μ-iodo-bis(dinitrosyliron) with halide ions and with thiols: An electron paramagnetic resonance study

Solutions of Fe₂(NO)₄I₂ in DMF exhibit EPR spectra characteristic of [Fe(NO)₂]⁺ at concentrations of 2 x 10^?4 mol dm^?3, and of an equilibrium mixture of [Fe(NO)₂⁺, Fe(NO)₂I, and [Fe(NO)₂I₂]^? at higher concentrations: in THF solutions only Fe(NO)₂I is observed, regardless of concentration. Addition of excess halide ions X^? (X=Cl, Br, I) to the DMF solution yields [Fe(NO)₂X₂]^?, but addition of excess I^? or Br^? to the THF solution yields [Fe(NO)₂I₂^? or Fe₂(NO)₄Br₂ respectively. In mixed THF/Et₃N solutions, mixtures of [Fe(NO)₂]⁺, Fe(NO)₂I, and [Fe(NO)₂I₂]^? are again formed, and subsequent addition of a thiol RSH causes formation of [Fe(NO)₂(SR)₂]^?, a precursor of Fe₂(NO)₄(SR)₂. A scheme is suggested to describe the steps in the preparatively useful conversion of Fe₂(NO)₄I₂ into Fe₂(NO)₄(SR)₂.     

Untersuchungen an Polyhalogeniden. XVI. Darstellung und Kristallstrukturen der Bipyridiniumpolyiodide Bipy · HIn mit n = 3, 5 und 7

Studies on Polyhalides. 16. Preparation and Crystal Structures of Bipyridiniumpolyiodides Bipy · HI_n with n = 3, 5, and 7 With simply protonated α,α′-Bipyridyl Bipy · H⁺ a triiodide Bipy · HI₃, a pentaiodide Bipy · HI₅ and a heptaiodide Bipy · HI₇ may be prepared in the presence of iodide ions I^? and dependent of the iodine I₂ content. Bipyridiniumtriiodide C₁₀H₉N₂I₃ crystallizes at room temperature monoclinically in P2₁/n with a = 1 122.8(1) pm, b = 1 072.7(1) pm, c = 1 200.2(3) pm, β = 98.02(2)° and Z = 4. The crystal structure is built up from mixed cationic and anionic layers. Bipyridiniumpentaiodide C₁₀H₉N₂I₅ crystallizes at room temperature monoclinically in P2₁/c with a = 887.3(5) pm, b = 2 527.9(12) pm, c = 830.7(3) pm, β = 106.78(5)° and Z = 4. The crystal structure contains triiodide ions I₃^? till now uniquely connected by iodine molecules I₂ in a trigonal planar way. Bipyridiniumheptaiodide C₁₀H₉N₂I₇ crystallizes at room temperature triclinically in P&1macr; with a = 713.1(3) pm, b = 1 007.9(3) pm, c = 1 464,8(4) pm, α = 81.07(3)°, β = 89.92(3)°, γ = 82.77(3)° and Z = 2. The crystal structure contains a V-shaped pentaiodide ion I₅^? completed by an iodine molecule I₂ to a trigonal pyramidally shaped heptaiodide ion I₇^? and at the same time connected to a zigzag chain.     

ZnO nanoparticles and poly(acrylic) acid-based polymer gel electrolyte for photo electrochemical cell

This work presents a photo electrochemical cell based on zinc oxide (ZnO) nanoparticles and poly(acrylic) acid (PAA) doped with sodium iodide (NaI) and iodine (I₂) polymer gel electrolyte. The ZnO powders were synthesized by sol–gel storage and sol–gel centrifugation. The ZnO powder synthesized via sol–gel centrifugation showed the optimal structural properties, with largest crystallite sizes of 58 nm, average particles size between 20 and 80 nm and indirect band gap energy of 3.20 eV. The highest conductivity [(8.0 ± 0.1) × 10^?2 S cm^?1] was obtained for PAA + 0.8 M NaI + 0.02 M I₂. This sample achieved the lowest activation energy (0.029 eV) and electrochemical stability at 1.6 V. The ZnO powder synthesized via sol–gel centrifugation and PAA + 0.8 M NaI + 0.02 M I₂ was fabricated as a Cu–ZnO/PAA + 0.8 M NaI + 0.02 M I₂/C-ITO photo electrochemical cell.     

Electrochemistry in molten NaAlCl4 (at 210°C): Identification of dissolved oxide-containing species,solubility of alumina in terms of pCl− and properties related to H2O in this melt

It has been shown that a nickel electrode is an indicator of the presence of oxide ions dissolved in chloroaluminate melts. From quantitative interpretation of electrochemical results (voltammograms and potentiometric measurements), O^2? has appeared to behave, in terms of the chloro-acidobasicity concept, as a strong dibase, through a solvolytic reaction giving AlOCl₂^? as solvated form. AlOCl₂^? itself is a weak base, according to the system:AlOCl₂^?AlOCl+Cl^?, pK_B/mol kg^1-=4.35 (at210°C) Thus O^2? behaves cumulatively as a tribase. AlOCl is the solvated form of O^?II in very acidic melts.A saturation effect by Al₂O₃ appeared when the concentration of O^?II was increased. The solubility of Al₂O₃ in chloroaluminate melts (one third of total O^?II solubility) was determined from the electrochemical results obtained. A minimum of 0.13% in weight (solubility of O^?II=4×10^?2 mol kg^?1), is observed for pCl^?=4.5 that is in a mixture containing 51.4 moles per cent of AlCl₃. The solubility is increased by adding either more AlCl₃ (formation of AlOCl) or NaCl (formation of AlOCl₂^?). Its variation versus pCl^? has been expressed quantitatively.Through a study of the system HCl/H₂O, it was pointed out that hydrolysis of chloroaluminate melt does not occur to a great extent in basic media. On the contrary, elimination of oxide ions through H₂O formation by reaction with HCl was shown to be possible. A quantitative relation, which binds the total concentration of O^?II, pCl^? and the respective partial pressures of gaseous HCl and H₂O in equilibrium with the melt, is given.A treatment in order to carry out this purification in these melts appears necessary in order to prevent many dissolved metallic ions from precipitating under the form of oxides.     

Semiconducting tin oxide electrodes in molten sodium chloroaluminate at 175°C

Electrode behavior of Sb-doped poly-crystalline tin oxide electrodes has been investigated by means of current and differential capacity measurements in molten chloroaluminate melts (AlCl₃+NaCl) with different pCl values. The SnO₂ is stable in the melts consisting of near equimolar composition, being used as an indicator electrode possessing a polarizable potential region between chlorine evolution and its cathodic decomposition. The differential capacity is assigned to the space charge layer capacity of the electrode side and its potential dependence is explained by using the Mott-Schottky equation. It is found that the flat band potential does depend on pCl (=?log a_Cl^?) at a rate of 2(2.3kT/e) per pCl unit. This anomaly is attributed to the specific adsorption of Cl^? ions on the oxide electrode.     

Hybrid Calixarene/Inorganic Salt/Diiodoperfluorocarbon Supramolecular Assemblies

1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]crown-5 in the cone conformation (2), 1,8-diiodoperfluorooctane or 1,6-diiodoperfluorohexane, and potassium iodide ternary mixtures undergo in solution self-sorting and afford crystalline “supramolecular salts”. These hybrid materials consist of supercation [K⁺ ? 2] and superanion [I–(CF₂) _n –I…I^? …I–(CF₂) _n –I…I^? …] (n = 6,8) components. In the supercations the potassium ion is embedded in the ionophoric pocket created by the heteroatoms present at the lower rim. In the superanions the iodide ions form infinite fluorous polyanionic chains as a result of a self-assembly process which relies on halogen bonding. Both cation encapsulation and anion-perfluorocarbon halogen bonding were detected in solution by ¹H and ¹⁹F NMR, and in the gas phase by ESI MS.