Matrix isolation study of the products of the interaction between metastable Ar and Kr atoms and chloroform. Photodecomposition of HCCl+2 and HCCl−2

The emission spectrum of a microwave discharge through argon and the infrared and ultraviolet spectra of the products of the interaction of HCCl₃ with the periphery of such a discharge, observed after radpid quenching in an argon matrix at 14 K, indicate that metastable argon atoms play an important role in matrix isolation experiments using such a discharge configuration to produce free radicals and molecular ions. Exceptionally high yields of HCCL⁺₂ and HCCl^?₂ and a significant concentration of CCl⁺₃ were stabilized in these experiments. The observations support the assignment of the 1037 cm^?1 peak to “isolated” CCl⁺₃. Upon exposure of the sample to 370-280 nm radiation, a prominent, slightly perturbed absorption of ClHCl^? appeared at 705 cm^?1. This absorption was destroyed by 280-260 nm radiation. The relative stability of both HCCl⁺₂ and CCl⁺₃ upon exposure of the sample to radiation of wavelength longer than 280 nm is attributed to electron scavenging by the HCCl₃ in the matrix; this species is present in considerably greater concentration than are the ion products. Evidence is presented for the photodecomposition of HCCl⁺₂ at wavelengths shorter than about 280 nm. A marked increase in the concentration of HAr⁺_n when HCCl⁺₂ was photolyzed by radiation of wavelength shorter than 260 nm is consistent with the calculated threshold energy for proton transfer from HCCl⁺₂ to Ar. The results of krypton matrix experiments are also consistent with this mechanism. Unstructured absorption bands near 285 and 250 nm are tentatively attributed to ClHCl^? and HCCl⁺₂, respectively. An increase in the concentration of “nonrotating” H₂O, compared to H₂O molecules free to undergo rotational transitions, when ions are present in the matrix can be attributed to the electric field producted by ionic interactions.     

Matrix isolation study of the products of the interaction of electrons and of argon atoms in excited Rydberg states with HCCIF2

Infrared absorptions of the (CICF)?H—F^? and HCF^?₂ anions have been identified in the spectrum of the products of the photolysis of HCCIF₂ isolated in an argon matrix at 14 K using radiation in the 147—105 nm spectral range. These anions are also produced in matrix experiments in which the Ar:HCCIF₂ sample is codeposited with an atomic beam of sodium and charge transfer processes are induced by mercury are radiation, as well as in experiments in which the sample is codeposited with a beam of argon that has been passed through a microwave discharge. Both the spectral data and molecular orbital calculations for HCF^?₂ indicate that this molecule has an exceptionally weak CH bond and that its apex angle is considerably more acute than that of the uncharged HCF₂ radical. The high threshold for ion production from HCCIF₂ dictates consideration of the role played by highly excited Rydberg states of argon in the discharge experiments. It appears probable that charge transfer occurs between these excited argon and HCCIF₂. The high ion yield typical of the discharge experiments is also consistent with product formation resulting from collision of matrix-isolated HCCIF₂ with free excitons formed by the impact of highly excited argon atoms at the surface of the solid deposit.     

Matrix isolation study of the interaction of excited argon atoms with CF2Cl2, CF2ClBr,and CF2Br2. Infrared spectra of the CF2Cl+ and CF2Br+ molecular ions

The infrared absorptions associated with the two CF stretching fundamentals of CF₂Cl⁺ and CF₂Br⁺ have been identified in studies of the matrix-isolated products of the interaction of excited argon atoms with CF₂Cl₂, CF₂ClBr, and CF₂Br₂. The exceptionally high values of the CF stretching frequencies obtained in these experiments are consistent with the implications of previous experimental and theoretical studies.     

Matrix isolation study of the interaction of excited argon atoms with methyl cyanide,vibrational and electronic spectra of ketenimine

When methyl cyanide mixed with an excess of argon is codeposited at 14 K with a beam of argon atoms that has been excited by a low power microwave discharge, infrared and ultraviolet absorptions of several previously unidentified products appear. The most prominent set of absorptions is assigned to ketenimine, previously tentatively identified as the product of the reaction of NH with C₂H₂ in an argon matrix. Using a molecular geometry resulting from a recent ab initio calculation and a valence force field with four interaction constants, it has been possible to obtain a satisfactory least-squares force constant fit to the infrared data for seven isotopic species of ketenimine. Two electronic band systems are also reported for ketenimine, which is photodissociated by 2537-A radiation. The mechanism by which ketenimine is formed may involve an initial electron transfer from excited argon to methyl cyanide. Spectrospic data are also considered for the other products, one of them tentatively identified as CH₂CH, which differ in their behavior on mercury-are photolysis of the sample.     

Plasma diagnostics of barrier-torch discharge in argon flow in a capillary by cross-correlation spectroscopy

The radiation kinetics of the plasma of barrier-torch disrcharge in argon flow in a capillary has been studied by cross-correlation spectroscopy. It was established that the discharge emission spectrum consists of peaks of electronically excited states of argon, bands of hydroxyl radicals, and a second positive system of nitrogen. An analysis of the spatio-temporal distributions of emission intensity for the selected spectral indicators showed that the causes of the torch are ionization waves that extend through the capillary from the electrode system with a speed of 10⁵ m/s and project up to 3–4 mm. It was established that the formation of electronically excited molecules of nitrogen N₂(C ³Π _u ) in the torch of discharge occurs mainly on the reaction between metastable electronically excited atoms of argon and molecules of nitrogen in the electronic ground state.     

Time resolved HF vibrational fluorescence from the IR photodissociation of SF6/H2 mixtures

Time resolved measurements of HF spontaneous emission, following the irradiation of SF₆/H₂ mixtures with the focused output from a CO₂ TEA laser, are reported. Our results indicate that F atoms are produced directly by the photodissociation process, and that these atoms have a recoil energy which is ≤500 cm^?1, and varies only slightly with the radiation intensity. Further, our results show a linear dependence of fluorescence intensity with laser energy, indicating that processes other than direct photodissociation may play a significant role in the ultimate fate of species excited by IR collisionless multiple photon absorption.     

Effect of Inorganic Ions on the Oxidation of Methyl Violet with Gliding Arc Plasma Discharge

Gliding arc discharge process was used for the treatment of methyl violet wastewater. First, the intermediate products were studied by gas chromatography coupled with mass spectrometry and Fourier transform infrared spectrometry, and ultraviolet–visible spectrometer. Second, the effects of inorganic anions including chloride (Cl^?), carbonate (CO₃ ^2?), sulfate (SO₄ ^2?), phosphate (PO₄ ^3?), nitrate (NO₃ ^?) on the degradation efficiency of methyl violet were examined. The research results indicated that hydroxyl radicals attacked carbon atom that situated in the center of dye molecule, and the conjugating structure of methyl violet was destroyed, and dye was degraded and decolored, so a possible degradation pathway was proposed by the analysis of intermediate products detected. The methyl violet degradation rate decreased with increasing anions concentrations, and their order of sequence according to the inhibition reaction was CO₃ ^2? > Cl^? > SO₄ ^2? > NO₃ ^?.     

Proton-donor properties of HCCl3, HSiCl3, and HGeCl3 molecules: a quantum-chemical study

Proton-donor properties of HCCl₃, HSiCl₃, and HGeCl₃ molecules were studied by quantum-chemical methods. According to calculations, the Mulliken charge of H is positive in trichloromethane and negative in the other two molecules. Trichlorogermane readily interacts with bases (B) to give the contact ion pairs HB⁺·GeCl₃ ^–. Reactions of trichlorosilane with strong bases also can lead to its reorganization and the formation of contact ion pairs. In all the ion pairs, the anions are oriented to the HB⁺ cations by the negatively charged Cl atoms. Owing to possible transfer of Cl^– to HB⁺, this type of ion pairs can be a source of dichlorogermylene GeCl₂ and, probably, dichlorosilylene SiCl₂.     

Wirkung von Substituenten und Anionen auf die Fluoreszenzeigenschaften gemischtligandiger (Amin-triphenylphosphan)kupfer(I)-Halogenide

Effect of Substituents and Anions on the Fluorescence Properties of Mixed-Ligand (Amine-triphenylphosphane) Copper(I) Halides Mixed-ligand complexes analyzing CuHal · PΦ₃ · Py? R where Hal = Cl^?, Br^?, I^? and where R are various substituents at the pyridine (Py) exhibit an intense solid state fluorescence depending on substituent and anion when excited with uv radiation (365 nm). It will be shown that there is a relation between fluorescence and mesomeric and inductive properties of substituents and anions.     

A five-coordinate complex of copper chloride with 2-amino-5-ethyl-1,3,4-thiadiazole

A complex of Cu(II) chloride with 2-amino-5-ethyl-1,3,4-thiadiazole (AET) was prepared, and its structure was studied by IR spectroscopy and single crystal X-ray diffraction. The complex has the composition CuCl₂(AET)₄. The coordination sphere of the copper atom includes four molecules of the heterocyclic ligand coordinated via N atoms of thiadiazole rings and one of Cl^? anions; the second Cl^? anion is in the outer sphere.     

Unexpectedly strong anion–π interactions on the graphene flakes

Interactions of anions with simple aromatic compounds have received growing attention due to their relevancy in various fields. Yet, the anion–π interactions are generally very weak, for example, there is no favorable anion–π interaction for the halide anion F^? on the simplest benzene surface unless the H‐atoms are substituted by the highly negatively charged F. In this article, we report a type of particularly strong anion–π interactions by investigating the adsorptions of three halide anions, that is, F^?, Cl^?, and Br^?, on the hydrogenated‐graphene flake using the density functional theory. The anion–π interactions on the graphene flake are shown to be unexpectedly strong compared to those on simple aromatic compounds, for example, the F^?‐adsorption energy is as large as 17.5 kcal/mol on a graphene flake (C₈₄H₂₄) and 23.5 kcal/mol in the periodic boundary condition model calculations on a graphene flake C₁₁₃ (the supercell containing a F^? ion and 113 carbon atoms). The unexpectedly large adsorption energies of the halide anions on the graphene flake are ascribed to the effective donor–acceptor interactions between the halide anions and the graphene flake. These findings on the presence of very strong anion–π interactions between halide ions and the graphene flake, which are disclosed for the first time, are hoped to strengthen scientific understanding of the chemical and physical characteristics of the graphene in an electrolyte solution. These favorable interactions of anions with electron‐deficient graphene flakes may be applicable to the design of a new family of neutral anion receptors and detectors. © 2012 Wiley Periodicals, Inc.     

Distribution of metastable argon atoms in the modified Grimm-type electrical discharge

The absorbance by metastable argon atoms of the Ar 696.543 nm line in the modified Grimm-type electrical discharge source was measured at different discharge conditions and at distances varying from 0.25 to 6 mm from the cathode. A uranium/argon hollow cathode lamp was used as primary source, which gave an argon gas temperature of 850 K when run at 12 mA. A maximum absorbance of 0.57 was found 3 mm from the cathode at 600 V, 80 mA. The magnitude of absorbance increases with discharge current while the position of maximum absorbance shifts away from the cathode with increase in discharge voltage. The quenching of metastable atoms by nitrogen is demonstrated.The spatial distribution of the intensity of four different types of spectral lines is shown. The approximate number densities of the different particles are 10¹²cm^?3 for metastable argon atoms, 10¹⁶cm^?3 for neutral argon atoms, 10¹³ cm^?3 for sputtered copper atoms and 10¹⁴cm^?3for electrons.     

On‐site sampling of inorganic contamination on the metal surface and analysis with capillary electrophoresis

Pipes are the primary structural elements used for transporting fluid in various industries. The most common damage mechanism is corrosion, which occurs in pipes surface of turbine. The corrosive compounds for pipes are inorganic ion (Na⁺, Cl^?, NH₄⁺, NO₃^?, etc.) and grinding oil. For rapid and quantitative detection of inorganic ions on site, more reliable and reproducible analytical methods are demanded. A highly efficient solid–liquid sampling collection system is introduced in this work. Papering on the sample surface, inorganic cations and anions were simultaneously collected and analyzed by capillary electrophoresis with indirect ultraviolet detection. As a result, five cations (Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺) and three anions (Cl^?, NO₃^?, SO₄^2?) were completely separated. The efficiency of the sampling and ability of capillary electrophoresis analysis were presented by the determination of trace‐level (mg/m²) contaminants. The recoveries of cations and anions on the paper from metal surface were between 86.6 and 107.2%, and the relative standard deviations were less than 12.85%.     

An Internal Fluorescent Probe Based on Anthracene to Evaluate Cation–Anion Interactions in Imidazolium Salts

A series of fluorescent imidazolium‐based salts containing the cation [AnCH₂MeIm]⁺ (in which An=anthracene and Im=the imidazolium cation) with Cl^?, BF₄^?, PF₆^?, SO₃CF₃^?, [N(CN)₂]^?, [N(SO₂CF₃)₂]^?, or PhBF₃^? anions have been prepared and characterized. X‐ray diffraction analysis of four of the salts reveals a number of C? H???X‐type (X=O, N, F) hydrogen bonds between the hydrogen atoms from the imidazolium ring and in some cases from the anthracene ring with the electronegative atoms of the anions. Additionally, C? H???π interactions can be found in all the salts analyzed by X‐ray diffraction, whereas π–π stacking is observed only in the salt containing the phenyltrifluoroborate anion. Fluorescence emission analysis in acetonitrile shows that the fluorescence of these salts varies significantly according to the nature of the anion, and correlates to the extent of ion pairing present in solution. Photodimerization of these salts was observed, and in one case a dimer has been isolated and characterized by X‐ray crystallography.     

Reactions of the fluorobromocarbene radical studied by laser-induced fluorescence

CFBr radicals produced by the reaction of atomic oxygen with F₂CCFBr were monitored in a discharge flow system by fluorescence excited at 424 nm. The rate coefficients for reactions of the CFBr radicals were measured between 298 and 358 K, and the following values were obtained in units of cm³/molec·s: O₂ < 2 × 10^?16 at 353 K; NO < 10^?14 at 298 K; F₂CCFBr < 10^?15 at 298 K; Cl₂ (1.9 ± 0.6) × 10^?12 exp(?762 ± 92/T) Br₂ (1.4 ± 0.3) × 10^?12 exp(?533 ± 62/T).     

Excitation of H2 using continuously tunable coherent XUV radiation (97.3–102.3 nm)

Broady tunable EUV radiation from 97.3 to 102.3 nm has been generated by frequency tripling the second-harmonic output of a Nd:YAG-pumped dye laser in a pulsed argon source. About 7 × 10⁹ photons per shot in a 1.7 cm^?1 bandwidth are produced, corresponding to a conversion efficiency of ≈10^?6. Four bands of the Lyman system and two bands of the Werner system of molecular hydrogen were excited. Detection of H₂ densities of ≈2 × 10⁸ molecules/cm³ in a ω″, J″, level was accomplished using laser-induced fluorescence.     

Niobium oxochlorides in the gas phase: Quantum chemical calculations of the structure and relative stability of isomers

The gas-phase niobium oxochloride anions that result by the interaction between the finely dispersed stereoselective acetylene cyclotrimerization catalyst NbCl₂(C _n H _n ) (n = 10–12) and atmospheric oxygen and moisture have been characterized by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. From the relative intensities of mass spectrometric lines, it has been deduced that, among the various niobium oxochloride species passing into the gas phase under the action of laser radiation, the most abundant monomer ion is NbO₂Cl ₂ ^? , the most abundant dimers are Nb₂O₄Cl ₃ ^? and Nb₂O₃Cl ₅ ^? , the most abundant trimer is Nb₃O₆Cl ₅ ^? , and the most abundant tetramer is Nb₄O₈Cl ₅ ^? . The gas phase also contains low concentrations of fragments corresponding to the pentanuclear anion Nb₃O₁₁Cl ₄ ^? and the hexanuclear anion Nb₆O₁₅Cl ₂ ^? . The geometric parameters and total energy of the stable isomers of the dinuclear and polynuclear niobium oxochloride anions existing in the gas phase has been calculated by quantum chemical methods, and their relative thermodynamic stabilities have been determined for different metal core configurations and different arrangements of oxygen and chlorine ions. The stereochemistry of the niobium oxochlorides is discussed.     

Anion binding properties of tris(2-hydroxyphenyl)methanes

Tris(2-hydroxyphenyl)methane derivatives (1) displayed excellent selectivity for Cl^? in comparison with other anions tested (Br^?, I^? and NO₃ ^?) by ¹H NMR titration experiments. This selectivity is attributed to the fit size and shape of Cl^?, which favor the formation of a stable host–guest complex with 1 through the multiple intermolecular hydrogen bonds.     

Fluorescence of Xe2 molecules in the vacuum-ultraviolet

Fluorescence of the Xe₂ continuum between 1460 and 1800 Å has been observed during excitation of Xe₂ molecules with CO fourth positive bands from a microwave discharge lamp. Fluorescence spectra at different Xe and added gas pressures show that in collisions with Xe or Kr atoms, the excited Xe₂ diatoms are efficiently relaxed to low vibrational levels of the ¹Σ_u⁺ and ³Σ_u⁺ potentials without being quenched noticeably. With Kr the rate constant for relaxation out of the primarily excited high vibrational levels is found to be about 3×10^?11 cm³ molecule^?1 s^?1.     

Hypervalent silicon versus carbon: ball-in-a-box model

Why is silicon hypervalent and carbon not? Or why is [Cl? CH₃? Cl]^? labile with a tendency to localize one of its axial C? Cl bonds and to largely break the other one, while the isostructural and isoelectronic [Cl? SiH₃? Cl]^? forms a stable pentavalent species with a delocalized structure featuring two equivalent Si? Cl bonds? Various hypotheses have been developed over the years focusing on electronic and steric factors. Here, we present the so‐called ball‐in‐a‐box model, which tackles hypervalence from a new perspective. This model reveals the key role of steric factors and provides a simple way of understanding the above phenomena in terms of different atom sizes. Our bonding analyses are supported by computation experiments in which we probe, among other things, the shape of the S_N2 potential‐energy surface of Cl^? attacking a carbon atom in the series of substrates CH₃Cl, ^.CH₂Cl, ^..CHCl, and ^...CCl. Our findings for ClCH₃Cl^? and ClSiH₃Cl^? are generalized to other Group 14 central atoms (Ge, Sn, and Pb) and axial substituents (F).