Product formation in the association reaction of ClO with NO2 investigated by diode laser kinetic spectroscopy

Diode laser spectroscopy has been employed to monitor the formation of chlorine nitrate (ClONO₂) in the association reaction of ClO with NO₂. Chlorine nitrate is the only stable end-product of this reaction at room temperature. Time-resolved measurements of ClONO₂ formation using molecular modulation showed no evidence for any involvement of unstable isomers of ClNO₃ in the reaction. These measurements gave a value of k₁ = (1.8 ± 0.4) × 10^?31 cm⁶/molecule² · s for the reaction at 295 K and an upper limit of 5 ms for the lifetime of any isomeric products at this temperature.     

Theoretical investigation of the isomers photolysis reaction for chlorine nitrate

For the reactant ClONO₂ the equilibrium geometry and energy have been calculated by using various density functional (DFT) theory methods. The harmonic vibrational frequencies were computed using the B3LYP method for the ground state of the reactant; the results were in good agreement with those of the experiment. It was shown that the DFT methods were superior to other ab initio methods in optimizing geometry and predicting vibrational frequencies. In the process of forming the products from the dissociation reactions of ClONO₂, the results indicated it undergoes the TS₂, but not the TS₁ transition state. According to the relative energies of various species, the potential energy surface reflected intuitively the mechanisms of these dissociation reactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 44–50, 2003     

Production of atomic oxygen following flash photolysis of ClONO2

The photodissociation of ClONO₂ using a broad-band ultraviolet photolysis source has been investigated using time-resolved atomic absorption spectroscopy in the vacuum ultraviolet. The predominant atomic photolysis product is O(³PJ), the quantum yield for Cl(²PJ) production being less than 4%.     

Evaluation of data for atmospheric models: Master Equation/RRKM calculations on the combination reaction ClO + NO2 → ClONO2, a recurring issue

Experimental data for the title reaction have been modeled using Master Equation/RRKM methods based on the Multiwell suite of programs. The starting point for the exercise was the empirical fitting provided by the NASA and IUPAC data evaluation panels, which represent the data in the experimental pressure ranges rather well. Despite the availability of quite reliable parameters for these calculations (molecular vibrational frequencies and a value of the bond dissociation energy of ClONO₂, DH₂₉₈(ClONO₂) = 26.5 kcal mol^?1, corresponding to ΔH₀⁰ = 25.35 kcal mol^?1 at 0 K) and use of RRKM/Master Equation methods, fitting calculations to the reported data was anything but straightforward. Using these molecular parameters resulted in a discrepancy between the calculations and the database of rate constants of a factor of ca 4 at, or close to, the low‐pressure limit. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 573–581, 2009     

Reaktion von Chlornitrat mit CF3I: Isolierung von Trifluormethylchloriodnitrat CF3I(Cl)ONO2 und Kristallstruktur von Trifluormethylioddinitrat CF3I(ONO2)2

Reaction of Chlorine Nitrate with CF₃I: Isolation of Trifluormethylchloroiodinenitrate CF₃I(Cl)ONO₂ and the Crystal Structure of Trifluormethyliodinedinitrate CF₃I(ONO₂)₂ CF₃I reacts with ClONO₂ to Iodine(III)-compounds. After an addition CF₃I(Cl)ONO₂ is isolated and characterized by vibrational spectra. With surplus ClONO₂ it is formed CF₃I(ONO₂)₂. CF₃I(ONO₂)₂ crystallizes monoclinic in the space group P2₁/c with the cell parameters a = 1 024.3(6) pm, b = 873.5(6) pm, c = 873.4(6) pm and Z = 4. We measered following bonding distances: I? O: 207.3(3) and 220.8(2) pm, I? C: 221.1(4) pm and N? O: from 119.1(4) to 141.5(3) pm. Through an intermolecular I ··· O-contact the central iodine becomes a distorted plane geometry.     

Ion imaging studies of ClONO2 photodissociation: Primary branching ratios and secondary dissociation

The photodissociation dynamics of ClONO₂ at 235 nm has been reinvestigated using velocity map ion imaging. We report branching ratios for the Cl + NO₃ and ClO + NO₂ channels to be 0.49:0.51 with anisotropy parameters of β = 0.5 ± 0.1 and β = −0.1 ± 0.3 for the Cl and ClO production channels, respectively. Photodissociation at 248 nm and 262 nm results in similar branching ratios and dynamics as observed at 235 nm. Measured O(³P₂) images arising from ClONO₂ dissociation at 226 nm suggest that oxygen atoms result from the spontaneous dissociation of metastable NO₃. The quantum yield of O atoms arising from the spontaneous dissociation of NO₃ varies from 0.09 at 262 to 0.38 at 235 nm based on the derived internal energy distributions of the NO₃ fragments. We also describe a Monte-Carlo forward-convolution fitting of imaging data which permits detailed analysis of both spontaneous secondary dissociation and secondary photodissociation.     

A kinetic study of chlorine radical reactions with ketones by laser photolysis technique

Rate coefficients for reactions between Cl radicals and four ketones were determined at 294 ± 1 K with a relative rate method using a laser photolysis technique. The experiments were conducted in synthetic air in a flow system at atmospheric pressure. A mixture of Cl₂/ClONO₂ was photolyzed and the formation of NO₃ through the reaction Cl + ClONO₂ → Cl₂ + NO₃ was measured with and without ketones in the reaction mixture. The NO₃ radical concentration was measured by optical absorption using a diode laser as the light source. The rate coefficients for the Cl-ketone reactions could then be evaluated. The following rate coefficients were obtained (in units of cm³ molecule⁻¹ s⁻¹): cyclohexanone (7.00 ± 1.15) × 10⁻¹¹; cyclopentanone (4.76 ± 0.33) × 10⁻¹¹; acetone (1.69 ± 0.32) × 10⁻¹²; and 2,3-butanedione (7.62 ± 1.66) × 10⁻¹³. The accuracy of the method employed was tested by using the well-studied reaction between Cl and methane and a rate coefficient of (9.37 ± 1.04) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹ was obtained, which is in good agreement with previous work. The errors are at the 95% confidence level. The results in this work indicate that a carbonyl group in a ketone lowers the reactivity towards α-hydrogen abstraction by Cl radicals, compared to the corresponding Cl-alkane reactions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 195–201, 1997.     

The HCl+ClONO2 reaction rate on various water ice surfaces

The reaction ClONO₂+HCl → Cl₂+HNO₃ on ice surfaces was investigated using a fast flow reactor coupled to a chemical ionization mass spectrometer. Rough and relatively smooth ice surfaces and single-crystal ice particles were employed to investigate the effect of the different surface morphologies on the reaction mechanism. Large reaction probabilities (γ>0.1), independent of HCl partial pressure in the range from 2×10⁻⁷ to 8×10⁻⁶ Torr, were measured on these three ice surfaces. These results are consistent with an ionic reaction mechanism involving HCl solvation on a liquid-like surface layer.     

Perfluoralkyltellur-Verbindungen: Oxidation von (CF3)2Te Darstellungen und Eigenschaften von (CF3)2TeCl2, (CF3)2TeBr2, (CF3)2Te(ONO2)2 und (CF3)2TeO [1]

Perfluorosalkyl Tellurium Compounds: Oxidation of (CF₃)₂Te; Preparations and Properties of (CF₃)₂TeCl₂, (CF₃)₂TeBr₂, (CF₃)₂Te(ONO₂)₂, and (CF₃)₂TeO From the oxidation of (CF₃)₂Te with Cl₂, Br₂, O₂, and ClONO₂ the new trifluoromethyl tellurium compounds (CF₃)₂TeCl₂, (CF₃)₂TeBr₂, (CF₃)₂TeO, and (CF₃)₂Te(ONO₂)₂ are prepared. The ¹⁹F, ¹³C and ¹²⁵Te n.m.r. spectra, the vibrational and mass spectra as well as the chemical properties of these compounds are described. By variation of the reaction conditions CF₃TeCl₃ and CF₃TeBr₃ are also formed. It has not been possible to isolate (CF₃)₂TeI₂, but there is some evidence that it is formed as an intermediate. (CF₃)₂Te reacts with ozone to a very unstable compound, which decomposes at low temperature.     

Chlorine nitrate photolysis by a new technique: very low pressure photolysis

Very low pressure photolysis (VLPØ) of chlorine nitrate was performed in a quartz Knudsen cell. The light source was a 2500 W high-pressure xenon lamp, and a modulated molecular-beam mass spectrometer was used to monitor the concentration of ClONO₂ and photolysis products. Because of the low pressures used (? 10^?3 torr) and the short residence time in the cell (≈1 s), secondary reactions were unimportant and the primary products could be directly identified. The primary photolysis products (λ ≈ 2700 Å) are atomic chlorine and NO₃ free radical. Chlorine atoms were identified both by the appearance of Cl₂ (wall recombination product; the walls were not poisoned) and by HCl produced when C₂H₆ was added to the cell. Nitrate free radical was directly identified as a mass peak at m/e = 62, as well as by chemical titration with nitric oxide: NO₃ + NO → 2NO₂. It was verified by direct tests that the peak at m/e = 62 did not arise from possible HNO₃ contamination or from N₂O₅, a possible secondary product. This titration reaction was used to measure quantitatively a lower limit to the primary quantum yield, φ ? 0.5 ± 0.3. This represents a lower limit because of the unknown extent of the secondary photolysis of NO₃ under our conditions. We believe this to be the first observation using mass spectrometry of the NO₃ free radical. The quantum yield for atomic chlorine is φ = 1.0 ± 0.2. N₂O was used to test for O(¹D) according to the reaction, O(¹D) + N₂O → products; none was observed. Triplet oxygen, O(³P) was observed to the extent of ≈ 10% by the reaction O(³P) + NO₂ → NO + O₂, but this yield can also be due to the photolysis of NO₃ free radical produced in the primary step. We conclude that the predominant reaction pathway is

.     

Investigation of synthesis and microstructure of bismuth titanates with TiO<Subscript>2</Subscript> rich compositions

Preliminary examinations regarding formation of bismuth titanates in a part of Bi₂O₃—TiO₂ system rich with TiO₂ have been carried out. Bismuth titanates have been synthesized from mixtures of Bi₂O₃ and TiO₂ (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi₄Ti₃O₁₂, Bi₂Ti₂O₇ and Bi₂Ti₄O₁₁. Existence of controversial bismuth titanate of formula Bi₂Ti₃O₉ in the Bi₂O₃—TiO₂ system has not been confirmed.     

Synthesis of complex cesium hydrosulfatophosphates

Solubility of the CsH₂PO₄-CsHSO₄-H₂O system has been studied using the isothermal method (25.0°C); the compounds Cs₄(HSO₄)₃(H₂PO₄), Cs₃(HSO₄)₂(H₂PO₄), and Cs₅(HSO₄)₂(H₂PO₄)₃ have been found to form; Cs₅(HSO₄)₂(H₂PO₄)₃ has been obtained for the first time. Single crystals of the isolated phases have been grown. Their composition has been determined, and agreement between the results of studying solid phases in the CsH₂PO₄-CsHSO₄-H₂O and these single-crystal samples has been demonstrated. X-ray diffraction analysis of these phases has been carried out.     

Thiosemicarbazone complexes of the platinum metals. A story of variable coordination modes

Salicylaldehyde thiosemicarbazone (H₂saltsc) reacts with [M(PPh₃)₃X₂] (M = Ru, Os; X = Cl, Br) to afford complexes of type [M(PPh₃)₂(Hsaltsc)₂], in which the salicylaldehyde thiosemicarbazone ligand is coordinated to the metal as a bidentate N,S-donor forming a four-membered chelate ring. Reaction of benzaldehyde thiosemicarbazones (Hbztsc-R) with [M(PPh₃)₃X₂] also affords complexes of similar type, viz. [M(PPh₃)₂(bztsc-R)₂], in which the benzaldehyde thiosemicarbazones have also been found to coordinate the metal as a bidentate N,S-donor forming a four-membered chelate ring as before. Reaction of the Hbztsc-R ligands has also been carried out with [M(bpy)₂X₂] (M = Ru, Os; X = Cl, Br), which has afforded complexes of type [M(bpy)₂(bztsc-R)]⁺, which have been isolated as perchlorate salts. Coordination mode of bztsc-R has been found to be the same as before. Structure of the Hbztsc-OMe ligand has been determined and some molecular modelling studies have been carried out determine the reason for the observed mode of coordination. Reaction of acetone thiosemicarbazone (Hactsc) has then been carried out with [M(bpy)₂X₂] to afford the [M(bpy)₂(actsc)]ClO₄ complexes, in which the actsc ligand coordinates the metal as a bidentate N,S-donorformingafive-membered chelate ring. Reaction of H₂saltsc has been carried out with [Ru(bpy)₂Cl₂] to prepare the [Ru(bpy)₂(Hsaltsc)]ClO₄ complex, which has then been reacted with one equivalent of nickel perchlorate to afford an octanuclear complex of type [Ru(bpy)₂(saltsc-H)₄Ni₄](ClO₄)₄.     

Structure, stability and dissociation of silanitriles RSiN (R = H2B, H2N, H2P)

Structure, stability, and dissociation of H₂BSiN, H₂NSiN, H₂PSiN and their isomers H₂BNSi, H₂NNSi, H₂PNSi have been studied in detail using ab initio MP2 and CCSD(T) methods. After dissociation of H₂BNSi, H₂NNSi, H₂PNSi and their isomers, the fragmented atoms have been considered to be either in their ground state or in their valence excited state in various dissociation channels. Only allowed dissociations of these molecules are considered. Various dissociation channels of H₂BNSi, H₂NNSi, H₂PNSi and their isomers have been explored and interesting trends are observed for the dissociation of stable isomers H₂BNSi, H₂NNSi, H₂PNSi and less stable isomers H₂BSiN, H₂NSiN, H₂PSiN. The effect of substituents on their structural properties has been discussed. The potential energy surfaces for the RSiN ? RNSi isomerization reactions have been analyzed. The structural properties of these molecules agree well with the theoretical values wherever available.     

Novel dioxorhenium complex with bis(3,5-dimethypyrazol-1-yl)methane ligand – Synthesis,spectroscopic characterization,X-ray structure and DFT calculations

The reactions of [ReOBr₃(PPh₃)₂] and [ReOBr₃(AsPh₃)₂] with bis(3,5-dimethypyrazol-1-yl)methane (bdmpzm) have been examined and novel dioxorhenium(V) complex [ReO₂(bdmpzm)₂]Br · HBr · 2H₂O has been obtained. The compound has been studied by IR, UV–Vis, ¹H NMR spectroscopy, magnetization measurements and X-ray crystallography. The electronic structure of the [ReO₂(bdmpzm)₂]⁺ cation has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of [ReO₂(bdmpzm)₂]⁺ have been calculated with the TDDFT/PCM method, and the UV–Vis spectrum of [ReO₂(bdmpzm)₂]Br has been discussed on this basis.     

Phase equilibria in the Ce<Subscript>2</Subscript>O<Subscript>3</Subscript>-K<Subscript>2</Subscript>O-P<Subscript>2</Subscript>O<Subscript>5</Subscript> system

Ce₂O₃-K₂O-P₂O₅ ternary system has been investigated by thermoanalytical methods (DTA, DSC), powder X-ray diffraction, XPS and IR spectroscopy. The existence of three double potassium-cerium(III) phosphates has been confirmed and a new binary phosphate K₄Ce₂P₄O₁₅ has been found. Phase diagram and isothermal section at room temperature of the system Ce₂O₃-K₂O-P₂O₅ have been presented.     

Zinc(II) di(o-hydroxybenzoate) complexes with imidazole and its derivativesSynthesis,thermal characterization and molecular structures

Mixed complexes of the type: Zn(Hsal)₂(Him)₂, Zn(Hsal)₂(Him)₅, Zn(Hsal)₂(4-MeHim)₂ and Zn(Hsal)₂(1,2-diMeim)₂ (where Hsal=OHC₆H₄COO^-, Him=imidazole, 4-MeHim=4-methylimidazole, 1,2-diMeim=1,2-dimethylimidazole) have been synthesized. The application of chemical, thermal and X-ray methods has enabled us to analyze the complexes and their sinters. The gaseous products of pyrolysis of Zn(Hsal)₂(Him)₂ and Zn(Hsal)₂(4-MeHim)₂ have been investigated. Thermal decomposition pathways have been postulated for synthesized complexes. The molecular structures of the Zn(Hsal)₂(Him)₂ and Zn(Hsal)₂(1,2-diMeim)₂ have been solved.     

Subsolidus phase diagrams of the systems Cs2MoO4-R2(MoO4)3-Zr(MoO4)2, where R = Al, Sc, or In

The systems Cs₂MoO₄?R₂(MoO₄)₃?Zr(MoO₄)₂, where R = Al, Sc, or In, have been investigated in the subsolidus region by X-ray powder diffraction. Quasi-binary joins have been revealed, and triangulation has been carried out. Six new triple molybdates have been prepared with the component ratio equal to 1 : 1 : 1 (mol/mol) (S ₁) and 5 : 1 : 2 (S ₂). The crystal parameters for the 5 : 1 : 2 compounds have been determined, and the electrical properties of the 1 : 1 : 1 compounds have been investigated.     

Effective IR Laser Conversion of Carbon-13 Enriched Chlorodifluoromethane to Dibromodifluoromethane

Infrared laser conversion of chlorodifluoromethane (CF₂HCl) enriched in ¹³C to 31%, to dibromodifluoromethane (CF₂Br₂) with the same enrichment has been studied. Optimum conditions have been found, and effective laser synthesis of macroscopic amounts (1 g) of CF₂Br₂ has been carried out. IR absorption spectra of synthesized CF₂Br₂ with a ¹³C concentration of 31% have been recorded. The ¹³C isotope shifts of the ν₁, ν₆, and ν₈ modes have been measured.     

NEW PHTHALOCYANINE PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY

Six new aluminum and silicon phthalocyanines have been synthesized and their photocytotoxicity toward V79 cells has been studied. The compounds that have been prepared are: AIPcOSi(CH₃)₂(CH₂),N(CH₃)₂, I; AIPcOSi(CH₃)₂(CH₂)₃N(CH₃)₃⁺I^?, II; CH₃SiPcOSi(CH₃)₂(CH₂)₃N(CH₃)₂, III; HOSiPcOSi(CH₃)₂(CH₂)₃N(CH₃)₂, IV; HOSiPcOSi(CH₃)₂(CH₂)₃)₃(CH₃)₃⁺I^?, V; and SiPc[OSi(CH₃)₂(CH₂)₃N(CH₃)₃⁺I^?]₂, VI. Relative growth delay values for compounds I-VI and relative cytotoxicity values for compounds I, II, IV, V and VI have been determined. Compounds I and II have been shown to be comparable in photocytotoxicity to what is presumed to be AIPcOH.xH₂O, and compound IV has been shown to have greater activity. The classes of compounds to which these six compounds belong appear to have potential for photodynamic therapy.