Vibrational dependence of the NH3 (v2)+NO and NO(v)+NH3 charge transfer cross sections

A tandem quadrupole mass spectrometer is used to study the charge transfer reactions NH₃⁺ + NO and NO⁺ + NH₃ over a collision energy range 1.5–13 eV. The vibrational state of the reagent ions is selected by resonance-enhanced multiphoton ionization. For the 0.9 eV exothermic process NH₃⁺ + NO → NH₃ + NO⁺ excitation of the v₂ umbrella bending mode (v₂ = 0–12) causes no marked change in the charge transfer cross section, while in the reverse process NO⁺ + NH₃ → NO + NH₃⁺ excitation of the NO⁺ vibration (v = 0–6) strongly enhanced the charge transfer cross section.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

The multichannel reaction NH2 + NH2 at ambient temperature and low pressures

NH₂ profiles were measured in a discharge flow reactor at ambient temperature by monitoring reactants and products with an electron impact mass spectrometer. At the low pressures used (0.7 and 1.0 mbar) the gas-phase self-reaction is dominated by a ‘bimolecular’ H₂-eliminating exit channel with a rate coefficient of k_3b(300 K) = (1.3 ± 0.5) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ and leading to N₂H₂ + H₂ or NNH₂ + H₂. Although the wall loss for NH₂ radicals is relatively small (k_w ≈ 6–14 s⁻¹), the contribution to the overall NH₂ decay is important due to the relatively slow gas-phase reaction. The heterogeneous reaction yields N₂H₄ molecules.     

SO_4~(2-)功能化处理对Fe_2O_3催化剂上氨选择性催化还原NO_x性能的促进机理研究

采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。     

Novel iodoammonium cations: Synthesis and characterization of o-C6H4(NH2)2IX (X = I, AsF6, AlI4)

The new iodoammonium salts o-C₆H₄(NH₂)₂I⁺I⁻ (1) and o-C₆H₄(NH₂)₂I⁺ AsF₆⁻ (2) were prepared by reaction of o-phenylene diamine with I₂ or I₃⁺AsF₆⁻, respectively. Compound 1 reacts with AlI₃ yielding quantitatively the corresponding tetraiodoaluminate o-C₆H₄(NH₂)₂I⁺AlI₄⁻ (3). The species were characterized by chemical analysis, vibrational (IR and Raman) and temperature-dependent ¹H NMR spectropscopy. Direct evidence for a N---I bond was found in the Raman spectra of 1, 2 and 3 (ν(NI) = 599–600 cm⁻¹).     

The ν3 infrared spectrum of the He---NH4 complex

The mid-infrared spectrum of the ionic complex He---NH₄⁺ has been recorded in the vicinity of the triply degenerate ν₃ (t₂) vibration of the free ammonium ion. Apart from a small blue shift (≈ 0.7 cm⁻¹), the spectrum of the complex closely resembles that of the monomer. Ab initio calculations predict a vertex-bound minimum structure with an intermolecular well depth D_e ≈ 150 cm⁻¹, a center-of-mass separation of R_e ≈ 3.17 Å and barriers for internal rotation less than 30 cm⁻¹.     

The A Πu-X Πg emission spectrum of I2

The A ²Π_u-X ²Π_g electronic emission spectrum of I₂⁺ has been recorded at a low rotational temperature in a crossed molecular beam/electron beam apparatus. Six vibrational sequences with five or more members have been assigned to progressions in ν′, giving ω′_e = 122±8 cm⁻¹, but a full vibrational analysis has not been possible. It is not known whether this is due to the relatively poor resolution (≈5 cm⁻¹) at which the spectrum has been recorded or because the A ²Π_u state is perturbed in one or both spin-orbit components. Existing data on the A state of I₂⁺ are reviewed.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

Ion chromatography of organic-rich natural waters from peatlands II. Na, NH4, K, Mg and Ca

Organic rich natural waters from peat bogs in continental (Switzerland) and maritime (Shetland Islands, Scotland) environments were analysed for Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ using ion chromatography. These cations were determined simultaneously in surface and pore water samples from the continental bogs using a 250-μl injection loop in an isocratic separation. Using this loop, detection limits of the order of 1 ng/g were achieved. An organics-removal cartridge (Dionex OnGuard P) was used to remove humic materials. Analyses of deionized water filtered through these cartridges showed acceptably low blank values (e.g., ca. 5 ng/g) and appeared to have no significant effect on the measured cation concentration. For the maritime bog waters, the low concentrations of NH₄⁺ (ca. 1 μg/g) compared with Na⁺ (ca. 100 μg/g) required improved peak separation. This was accomplished using a gradient separation beginning with 40 mM HCl—1 mM , -2,3-diaminopropionic acid monochloride (DAP) and switching to 40 mM HCl-12 mM DAP after 2 min. Using a 25 μl injection loop, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ were determined simultaneously in less than 25 min. In this instance, even with Na⁺/NH₄⁺ > 100, there was no interference from Na⁺ in the determination of NH₄⁺ (baseline separated).     

Oxygen abstraction from tetrahydrofuran by molybdenum-iodide complexes. X-ray molecular structure of [Mo2(μ-O)(μ-I)(μ-O2CCH3)I2(THF)4][MoOI4(THF)] (THF = tetrahydrofuran)

The interaction between Mo₂(O₂CCH₃)₄, Me₃SiI and I₂ in THF resulted in oxygen abstraction from the solvent and formation of [Mo₂(μ-O)(μ-I)(μ-O₂CCH₃) I₂(THF)₄]⁺[MoOI₄(THF)]⁻ and I---(CH₂)₄---I. The molybdenum complex has been characterized by X-ray diffractometry. Crystal data: triclinic, space group P , a = 13.827(3) Å; b = 15.803(7) Å; c = 9.950(3) Å; = 93.34(4)°; β = 102.40(2)°; γ = 90.09(2)°; V = 2120(2) Å₃; Z = 2; d_calc = 2.559 g cm⁻³; R = 0.0476 (R_w = 0.0613) for 370 parameters and 3938 data with F₀²> 3σ(F₀²). The metal-metal distance in the cation is 2.527(2) Å and indicates a strong interaction. The magnetic behavior is consistent with the assignment of one unpaired electron to the Mo₂⁷⁺ core of the cation and one to the d¹ Mo(V) center of the anion. The interaction between Mo(CO)₆ and I₂ in THF also results in the formation of 1,4-diiodobutane.     

X-ray diffraction, Raman study and electrical properties of the new mixed compound [Rb0.44(NH4)0.56]2HgCl4 · H2O

Differential scanning calorimetry of [Rb_0.44(NH₄)_0.56]₂HgCl₄ · H₂O material showed three anomalies at 340, 355 and 424 K, respectively. The room temperature phase has space group Pcma (a=8.433(1) Å, b=9.1817(9) Å and c=11.954(1)). Phase II (T=350 K) is disordered and exhibits orthorhombic symmetry (a=8.456(13), b=9.202(9) and c=12.011(10) Å). Hydrogen bonding, the nature and the degree of structure (dis)order and the mechanisms of the transitions are discussed. The dielectric constant ^′ at different frequencies and temperature revealed a phase transition at T=340 K related to NH₄⁺ reorientation and H⁺ diffusion, and a characteristic increase above 355 K, which might be due to loss of water of crystallization. Transport properties in this compound appear to be due to an Rb⁺/NH₄⁺ and H⁺ ions hopping mechanism.     

NH3-SCR反应过程中NH3和NOx在Cu/SAPO-34分子筛催化剂上的吸附特性和作用

通过离子交换法制得Cu/SAPO-34菱沸石分子筛催化剂, 同时研究了NH₃和NO_x (NO和NO₂)在该催化剂上的吸附位、吸附强度、吸附量和吸附速率, 得到了不同反应气氛在Cu/SAPO-34 上的吸附性能及其在NH₃选择性催化还原(NH₃-SCR)反应中的作用. 研究采用瞬态实验、程序升温脱附(TPD)和漫反射傅里叶变换红外光谱(DRIFTS)等方法进行表征实验. 瞬态实验结果表明NH₃是吸附性气体. 程序升温脱附实验和红外漫反射实验结果表明NH₃可以吸附在布朗斯特和路易斯酸性位上形成不同的NH₃物种, 它们显示不同的SCR活性. NH₃在Cu²⁺上的吸附速率最快, 且键强最强. NO_x可以氧化并以硝酸盐/亚硝酸盐的形式吸附在Cu物种上. 最后, 本文讨论了NH₃选择性催化还原反应过程中在Cu物种上的中间物种并推测反应机理.     

暴露CeO2不同晶面的VOx-MnOx/CeO2催化剂低温NH3-SCR脱硝的原位红外研究

为实现低温(200-250℃) NH_3-SCR烟气脱硝,开发出了一种高分散暴露CeO_2不同晶面的VO_x-MnO_x/CeO_2低温脱硝催化剂。脱硝性能评价实验结果表明,暴露{110}晶面的VO_x-MnO_x/CeO_2-R催化剂在很宽的温度范围内(220-330℃)都保持了95%的脱硝效率。原位漫反射红外分析结果可知,暴露{110}晶面的VO_x-MnO_x/CeO_2-R催化剂表面更易发生NH_3和NO吸附,进而提高NO的转化效率。气态NH_3在VO_x-MnO_x/CeO_2-R催化剂上吸附生成NH_3(L)和NH_4~+(B),该中间体与NO吸附的中间体桥联硝酸盐和双齿硝酸盐反应生成N_2和H_2O,并遵循Langmuir-Hinshelwood机理。     

Thermal studies of novel molecular perovskite energetic material (C6H14N2)[NH4(ClO4)3]

(C6H(14)N2)[NH4(ClO4)3] is a newly developed porous hybrid inorganic-organic framework material with easy access and excellent detonation performances,however,its thermal properties is still unclear and severely hampered further applications.In this study,thermal behaviors and non-isothermal decomposition reaction kinetics of(C6H(14)N2)[NH4(ClO4)3] were investigated systematically by the combination of differential scanning calorimetry(DSC) and simultaneous thermal analysis methods.In-situ FTIR spectroscopy technology was applied for investigation of the structure changes of(C6H(14)N2) NH4(ClO4)3]and some selected referents for better understanding of interactions between different components during the heating process.Experiment results indicated that the novel molecular perovskite structure renders(C6H(14)N2)[NH4(ClO4)3] better thermal stability than most of currently used energetic materials.Underhigh temperature s,the stability of the cage skeleton constructed by NH4^+and ClO4^-ions determined the decomposition process rather than organic moiety confined in the skeleton.The simple synthetic method,good detonation performances and excellent thermal properties make(C6H(14)N2)[NH4(ClO4)3] an ideal candidate for the preparation of advanced explosives and propellants.     

The vibration-rotation spectrum and anharmonic potential of H3

Some qualitative effects of anharmonicity on the spectra of H₃⁺ and D₃⁺ between low vibrational levels are described. Using large-basis vibration-rotation calculations with a Morse-based discrete variable representation for the vibrations and a symmetric-top basis for the rotations, new spectra of H₃⁺ and D₃⁺ have been assigned. This procedure was assisted by adjusting eight coefficients for H₃⁺ and six coefficients for D₃⁺ in the Meyer-Botschwina-Burton ab initio potential function, and eventually 621 new and old lines of H₃⁺ to levels up to 3ν₂ and 529 new and old lines of D₃⁺ to levels up to 2ν₂ have been fitted with standard deviations of 0.118 and 0.059 cm⁻¹, respectively. An attempt is made to compare five different potential energy functions for the H₃⁺ system, two ab initio and three adjusted to fit spectra of H₃⁺ or D₃⁺, by expanding them by the same procedure in the same variables. For extension of the present work to higher vibrational levels, more accurate boundary behaviour at linear configurations will be required, and some aspects of the use of hyperspherical coordinates are discussed.     

On the origin of the splittings of the ν3(SO4) modes in the specular reflectance IR spectra of gypsum

The IR polarized spectra of gypsum CaSO₄·2H₂O were recorded at incidence angles of approximately 10 and 16 degrees. Band singlet or doublet was observed for the higher frequency ν₃(SO₄²⁻) mode of B_u symmetry type, depending on polarization (n or p). A doublet was observed for the lower frequency ν₃(SO₄²⁻) mode of B_u symmetry type too, irrespectively of the type of polarization. In order to give an explanation for the doublets origin, a model permittivity function was constructed. Quite good agreement exists between the reflectance based on the model permittivity function and the experimentally measured one for the high-frequency doublet. The origin of the lower frequency doublet could not be explained in this way, but may be speculated to result from an Evans type interaction between a combination of a water libration and ν₂(SO₄²⁻), with the lower frequency ν₃(SO₄²⁻) mode.     

添加Cl离子对V_2O_5-WO_3/TiO_2催化剂低温NO转化率的影响

考察添加不同含量Cl离子对浸渍法制备的Cl-V_2O_5-WO_3/TiO_2催化剂低温NO转化率的影响。随着Cl离子质量添加量从0增加到2.5%,Cl-V_2O_5-WO_3/TiO_2催化剂NO转化率先升高后降低,结合在含有SO_2和H2O的SCR实验结果,确定1.5%Cl-V_2O_5-WO_3/TiO_2为性能最优催化剂。在反应温度为149-362℃,NO转化率大于95%;在145-385℃,NO转化率大于90%。采用XRF、BET、XRD、TG、FT-IR和H2-TPR等方法表征了催化剂的物理化学性能和结构。结果表明,在反应气氛中加入SO_2和H2O后,催化剂比表面积和孔容均减小,副反应产物含有NH+4和SO_2-4。适量Cl离子可以抑制硫物种沉积,减少副反应产物生成,增强催化剂抗中毒能力。     

Ab initio study of the two competitive channels HO2 + H → H2 + O2 and HO2 + H → H2O + O

Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO₂(²A″)+H(²S) → H₂(¹Σ⁺_g)+O₂(³Σ⁻_g) and the concerted H approach-O removing reaction HO₂ (²A″)+H(²S) → H₂O(¹A₁)+O(³P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of C_s symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×10⁹ ℓ mol⁻¹ s⁻¹ for the first reaction, 20.0 kcal and 5.4.10⁻⁵ ℓ mol⁻¹ s⁻¹ for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO₂ is an efficient mechanism for the formation of H₂ + O₂, while the concerted mechanism envisaged for the formation of H₂O + O is highly unlikely.     

Crystal Structure, Nano-particle Morphology and Interaction with ATP of [ NH3 CH2 CH（ NH2 ） CH3 ]2 [ M（ Ⅵ ） O2 （ OC6 H4 O）2 ] （M = Mo0. 6 W0. 4 ） and Its Activity to Promote DNA Cleavage

The title complex [NH_3CH_2CH(NH_2)CH_3]_2 [M(Ⅵ)O_2(OC_6H_4O)_2](M= Mo_(0.6)W_(0.4))was synthesized via a simple solution-phase chemical route.The determination of single crystal X-ray diffraction revealed that the title compound is crystallized in a monoclinic system with P2(1)/n space group,a=1.0913(10)nm,b=1.0442(10)nm,c=1.8842(19)nm,α=90°,β=96.530(17)°,γ=90°,Z=4,and V=2.133(4)nm3.The mononuclear anionic unit [M(Ⅵ)O2(OC6H4O)2]2-displays chiral pseudo-octahedral [MO_6] coordination geometry and is linked by chiral cations via hydrogen bond and π…π stacking interaction.The transmission electron microscopy images show that the title complex is comprised of nano-particles with diameters ranging from 20 to 50 nm.The NMR study shows the 1H downfield chemical shifts of [NH_3CHaHbCH(NH_2)CH_3] cations in the title complex when it is mixed with adenosine-triphosphate(ATP),and the chemical shift difference between Ha and Hb is increased greatly,and most of the catecholate ligands dissociate from the central metal atoms.The DNA cleavage activity experiment reveals that DNA cleavage promoted by the title complex is lower than that by Na_2MoO_4 which possesses antitumor pro-perty,but higher than that by Na_2WO_4.     

Pathway studies in the fragmentation of Ge(CH3)4 involving Ge(3d,3p,3s) and C(1s) inner-shell photoexcitation in the range 49.5–450 eV

The dissociative multiple photoionization of tetramethylgermane (Ge(CH₃)₄) in the valence, and in the Ge(3d,3p,3s) and C(1s) inner-shell regions has been studied by using time-of-flight mass spectrometry coupled to synchrotron radiation in the range 49.5–450 eV. Total and individual photoion yields have been recorded as a function of the incident photon energy. Several discrete resonances over a structureless giant resonance are observed below the Ge(3p), Ge(3s) and C(1s) threshold regions. The structureless giant resonance corresponding to the Ge(3d) presumably arises from the continuum enhancement caused by the 3d→εf transition. Various monocations of H⁺, H₂⁺, CH_n⁺ (n=0–4), C₂H_n⁺ (n=0–5), GeH_n⁺, GeCH_n⁺, GeC₂H_n⁺, and GeC₃H_n⁺ are detected in the whole energy range. Dissociation processes have also been investigated by photoelectron–photoion and photoion–photoion coincidence methods. The dominant dissociation channel is found to be CH_n⁺–GeCH_n⁺ in the whole energy examined. Specific energy dependence of dissociation processes is observed in the Ge(3p) and Ge(3s) regions. With the help of ab initio HF/6-311++G(2df,p) calculation, we roughly estimated the photoabsorption positions and symmetries for the discrete core hole states.