Cation transport at 25°c from binary Na+Mn+, Cs+Mn+ and Sr2+Mn+ nitrate mixtures in a H2OCHCl3H2O liquid membrane system containing a series of macrocyclic carriers

Cation fluxes from binary mixtures of either Na⁺, Cs⁺ or Sr²⁺ with other alkali metal cations, alkaline earth metal cations, and Pb²⁺ through a H₂OCHCl³H₂O bulk liquid membrane system containing one of several macrocyclic carriers have been determined Nitrate salts were used in all cases. The most selective transport of Na⁺ over all other cations studied was found with the carrier cryptand [2.2.1]. Selective transport of Na⁺ relative to Li⁺, Cs⁺ and the alkaline earth cations was found with cryptand [2.2.2B] and cryptand [2.2.2D]. The ligands 21-crown-7 and dibenzo-24-crown-8 showed selective transport of Cs⁺ over the second cation in all cases. Several macrocycles showed selectivity for Sr²⁺ over the second cation with the macrocycle 1,10-diaza-18-crown-6 showing the highest selectivity for this cation of all ligands studied. Relative fluxes from binary cation mixtures are rationalized in terms of macrocycle cavity size, donor atom type and ring substituents.     

The properties of clusters in the gas phase: ammonia about Bi+, Rb+, and K+

Thermodynamic data are reported for NH₃ clustered about Bi⁺, Rb⁺, and K⁺ in the gas phase. Unusually strong bondings of NH₃ to Bi⁺ suggests the probable importance of partial covalent bonding in stabilizing the first ligand cluster. Differences in relative bond strengths for NH₃ and H₂O about Rb⁺ andK⁺ are consistent with the results of extended Hückel calculations reported herein.     

The structure of the H3O+ (hydronium) ion

Near Hartree-Fock level ab initio molecular orbital calculations on H₃O⁺ and a minimum energy structure with θ(HOH) = 112.5° and r(OH) = 0.963 Å and an inversion barrier of 1.9 kcal/mole. By comparing these results to calculations on NH₃ and H₂O, where precise experimental geometries are known, we estimate the “true” geometry of isolated H₃O⁺ to have a structure with θ(HOH) = 110-112°, r(OH) = 0.97–0.98 Å and an inversion barrier of 2–3 kcal/mole. Our prediction for the proton affinity of water is ≈ 170 kcal/mole, which is somewhat smaller than the currently accepted value.     

Luminescence in near-thermal charge exchange. II. He+ + H2O and He+ + D2O

An ICR spectrometer fitted with synchronous photon counting equipment is used to study the emission produced by near-thermal (? 0.1 eV) collisions between He⁺ and H₂O (D₂). Within the investigated wavelength region, 185 to 500 nm, the only significant emission features are the A³Π (υ' ? 3) → X³Σ^? bands in OH⁺ and OD⁺, and the A²Σ⁺ → X²Π(0.0) band in OH and, possibly, in OD. The corresponding excitation rate constants represent only ? 2% of the total He⁺/H₂O (D₂O) charge transfer. The resonant electron-jump model for thermal-energy charge exchange is discussed in the light of recent information on the He⁺/H₂O reaction and on the excited states of H₂O⁺ and their excitation by electron and photon impact on H₂O (D₂O).     

Experimental determination of repulsive potentials between alkali ions (Li+, Na+, and K+) and N2 and CO molecules

Integral scattering cross sections have been measured for alkali ions (Li⁺, Na⁺ and K⁺) in the energy range 500–4000 eV scattered by room temperature N₂ and CO molecules through effective laboratory angles greater than 5 × 10^?3 rad. The repulsive potentials deduced from the cross sections are represented bya practically identical formula for the Na⁺N₂ and Na⁺CO systems, and for the K⁺CO systems, respectively, while the repulsive potentials of the Li⁺N₂ system are somewhat smaller than those of the Li⁺CO system at larger intermolecular distances.     

Studies of layered uranium (VI) compounds. VI. Ionic conductivities and thermal stabilities of MUO2PO4 · nH2O,where M = H,Li,Na,K,NH4 or 12Ca, and where n is between 0 and 4

We have measured the ionic conductivities of pressed pellets of the layered compounds MUO₂PO₄ · nH₂O, and correlated the results with TGA data. The conductivities (in ohm^?1 m^?1), at temperatures increasing with decreasing water content over the range 20 to 200°C, were approximately as follows: Li⁺4H₂O, 10^?4; Li⁺, Na⁺, K⁺, and NH₄⁺3H₂O, 10^?4, 10^?2, 10^?4, and 10^?4; H⁺, Li⁺, and Na⁺1.5H₂O, 10^?2, 10^?4, and 10^?4; Na⁺1H₂O, 10^?5; H⁺, K⁺, and NH₄⁺0.5H₂O, all 10^?5; and H⁺, Li⁺, Na⁺, K⁺, NH⁺₄, and $\text{1}\text{2}\text{Ca}{}^{\mathrm{2+}}\text{}\text{OH}{}_2\text{O}$, 10^?5, 10^?5, 10^?4, 10^?5, 10^?5, and 10^?6. A ring mechanism is proposed to account for the high conductivity found in NaUO₂PO₄ · 3.1H₂O. The accurate TGA data showed that most of the hydrates had water vacancies of the Schottky type, and should be represented as MUO₂PO₄(A ? x)H₂O, where x can be between 0 and 0.3.     

Localized vibrations of H−Na+H− impurity in KCl crystal

Localized modes due to H^?Na⁺H^? complex impurity in KCl crystal have been computed by a Green function method and compared with experimental data.     

尖晶石型LiMn2O4晶体结构及锂离子筛H+/Li+交换性质研究

采用密度泛函理论平面波超软赝势和广义梯度近似法对尖晶石型LiMn2O4及其锂离子筛HMn2O4的晶体结构和性质进行了从头计算。PW91泛函最为有效,Li+被H+取代后HMn2O4晶胞收缩,点阵常数从LiMn2O4的0.823 nm减小至0.799 nm,其XRD峰也相应向高角度方向明显位移。经同种格点原子的XRD分析表明,Mn、O两元素对XRD方式和强度起着决定作用。其中Li呈+1价完全离子化,可被H+彻底交换,H与周围O在等电子密度图中呈现电子云相互连接,只带有0.42个正电荷。价轨道分态密度表明,Mn-O之间强的共价键合主要归因于Mn-d和O-p在费米能级下-7.3~-1.6 eV间的轨道重叠,形成了有利于H+/Li+交换的骨架空穴隧道。阵点和空穴多面体的体积遵守如下顺序:V8a>V48f>V8b、V16c>V16d、V16c>V48f。Li+最易迁移至邻近的16c位置,碱金属离子的交换受到离子半径和作用能大小的限制。     

The energy balance and branching ratios associated with the chemiluminescent reaction Si(3P) + N2O(1Σ) → SiO*(a3Σ+, b3Π, A1Π) + N2(υ″ ⩾ 5) — possible formation of vibrationally excited N2

Silicon atoms react under single collision conditions with N₂O to yield chemiluminescent emission corresponding to the SiO a³Σ⁺?X¹Σ⁺ and b³Π?X¹Σ⁺ intercombination systems and the A¹Π?X¹Σ⁺ band system. A most striking feature of the SiN₂O reaction is the energy balance associated with the formation of SiO product molecules in the A¹Π and b³Π states. A significant energy discrepancy ( = 10000 cm^? = 1.24 eV) is found between the available energy to populate the highest energetically accessible excited-state quantum levels and the highest quantum level from which emission is observed. It is suggested that this discrepancy may result from the formation of vibrationally excited N₂ in a concerted fast SiN₂O reactive encounter. Emission from the SiO a³Σ⁺ (A¹Π) and b³Π(A¹Π, E¹Σ₀⁺) triplet-state manifold results primarily from intensity borrowing involving the indicated singlet states. Perturbation calculations indicate the magnitude of the mixing between the b³Π, A¹Π and E¹Σ₀⁺ states ranges between 0.5 and 2%. On the basis of these calculations, the branching ratio (excited triplet)/(excited singlet) is found to be well in excess of 500. An approximate vibrational population distribution is deduced for those molecules formed in the b³Π state. The present studies are correlated with those of previous workers in order to provide an explanation for diverse relaxation effects as well as observed changes in the ratio of a³Σ⁺ to b³Π emission as a function of pressure and experimental environment. Some of these effects are attributable to a strong coupling between the a³Σ⁺ and b³Π state. Based on the current results, there appears to be little correlation between either (1) the branching ratio for excited state formation or (2) the total absolute cross section for excited-state formation and (3) the measured quantum yield for the SiN₂O reaction. Implications for chemical laser development are considered.     

Vibrational branching ratios for the A3Πi → X3Σ− system of OH+ and OD+

Near-thermal charge exchange between He⁺ and H₂(D₂O) is used as a source of OH⁺(OD⁺) A³H_i→ X³Σ^? emission. A comparison between experimental emission branching ratios and those calculated in the r-centroid approximation suggests that the electronic transition moment varies as a function of the r-centroid.     

Thermal-energy charge transfer of Ar+ with H2O: Internal and kinetic energy of the product H2O+

The reaction of Ar⁺ with H₂O has been investigated at near-thermal energy. The product ions H₂O⁺ and ArH⁺ account for 90 and 10% of the total reaction rate, respectively. Kinetic energy measurements and emission spectroscopy of the H₂O⁺ product ions are reported. It is concluded that at least 60% of H₂O⁺ ions are in the X? state with ≈2.4 eV vibrational energy while up to 40% are in the à state with a mean vibrational energy of 1.4 eV; the à state vibrational distribution has been determined. It is shown that both H₂O⁺ states are populated via an energetically “non-resonant” charge transfer process.     

Endothermic reactions of Ni+ with H2, HD and D2

An ion-beam apparatus is employed to study the reaction of Ni⁺ with H₂, HD, and D₂ as a function of kinetic energy. These reactions lead to the endothermic formation of NiH⁺, NiH⁺ and NiD⁺, and NiD⁺, respectively. Interpretation of the threshold for these processes yields the average bond energies, D⁰(Ni⁺H) = 1.86 ± 0.09 eV and D⁰(Ni⁺D) = 1.90 ± 0.14 eV. The total reaction cross sections for all three systems are similar; however, a striking isotope effect is observed for Ni⁺ reacting with HD. The dependence of the cross sections on relative kinetic energy is discussed in terms of simple models for reaction.     

Solubility and Ionic Processes in the Cu X 2? MX ?H2O ( X ?=Cl?, Br?; M +=Li+, Na+, K+, NH4+, Cs+) Systems

 Solubility isotherms in the CuBr₂−MBr−H₂O (M ⁺ = Li⁺, Na⁺, Cs⁺) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated solutions was performed.     

Computed potential hypersurface (including electron correlation) of the system Li+/H2

The potential hypersurface of the system LiH₂* is calculated in the Hartree—Fock approximation and with the IEPA PNO method (including electron correlation). The basis set consists of gaussian lobes. The region of HH distances considered is 0.9 to 3 a_o (occasionally to 5 a_o) whereas the distance of the Li nucleus to the midpoint of the H₂ subunit is varied between 1 and 15 α_o. The angular dependence of the hypersurface is investigated as well. The maximum overall error (except for a parallel shift of the whole hypersurface) is estimated to be less than 0.002 au and even smaller in more limited regions of space. The role of the correlation energy is discussed and the asymptotic behaviour of the Li⁺/H₂ interaction is compared with results from perturbation theory. The results are given both as tables of numbers in the form of an analytic fit. The change of energy, equiblirium distance and force constant of the H₂ as a function of the approach of the Li⁺ is also tabulated.     

Reduction of copper (II) chloride by molybdenum and rhenium biscyclopentadienyl hydrides. Investigation of the crystal and molecular structure of [(η5-C5H5)2Re]+[CuCl2]−

The reduction of copper (II) chloride by molybdenum and rhenium biscyclopentadienyl hydrides upon their interaction in donor-type solvents has been studied by NMR, X-ray diffraction, and magnetic methods. It is established that the ionic complex [(η⁵-C₅H₅)₂Re]⁺[CuCl₂]^? forms ortho rhombic crystals with a - 13.696(2) Å, b = 7.317(1) Å, c = 5.969(1) Å, space group Pm2₁n, Z = 2. The cyclopentadienyl rings make a bent-sandwich with an angle between the ring centres and Re atom of 150.1°; the ClCuCl angle being 174.8° and the ReCu minimum distance 4.346(29) Å. The solution of [(η⁵-C⁵H₅)²Re]⁺ [CuCl₂]^? seems to activate the CH bond of the C₅H₅ rings, which results in the addition of the [(C₅H₅)(C₅H₄)ReH]⁺ hydride ion.     

Compounds containing CSF4 and CS+F4

The preparations of CH₂SF₄ and CH₃CHSF₄ are presented and the structures are discussed. Addition reactions of polar species give a wide range of new compounds, like Hg(CH₂SF₅)₂, F₄AsCH₂SF₅, cisBrSF₄CH₃, cisF₅SeOSF₄CH₂Br, a.o. While CH₂SF₄ decomposes at room temperature slowly to CH₂CH₂ and SF₄, at high temperatures HF and CSF₂ are formed. CH₃CHSF₄ gives mainly CH₃CHF₂ at room temperature. The “saturated” compounds CH₃SF₅ and C₂H₅SF₅ have been prepared. They react with SbF₅ in SO₂ at low temperatures to form the cations CH₃SF₄⁺ and C₂H₅SF₄⁺. The CH₃SF₄⁺ ion has been investigated in detail by nmr methods at low temperatures. It decomposes to CH₃ and SF₄, which react further in the SO₂/SbF₅ system to CH₃OSO⁺ and SF₃⁺.     

Solubility and Ionic Processes in the Cu X 2? MX ?H2O ( X ?=Cl?, Br?; M +=Li+, Na+, K+, NH4+, Cs+) Systems

Summary.  Solubility isotherms in the CuBr₂−MBr−H₂O (M ⁺ = Li⁺, Na⁺, Cs⁺) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated solutions was performed. Corresponding author. E-mail: jitka@prfdec.natur.cuni.cz Received August 6, 2002; accepted (revised) November 29, 2002 Published online April 3, 2003     

A kinetic study of proton transfer reactions of NH+4, CH3NH+3, and PH+4 with calcium atoms

Cross section measurements for the proton transfer reactions of NH⁺₄, CH₃NH⁺₃, and PH⁺₄ with Ca(g) have been obtained over a range of low ion kinetic energies. For all reactions studied the cross sections drop sharply with increase in ion kinetic energy, indicating exothermic behavior. The results show that Ca(g) is an unusually strong base with a proton affinity in excess of 9.2 eV. Cross sections for the PH⁺₄Ca reaction are an order to magnitude higher than those for the NH⁺₄Ca reaction for ion energies between one and three eV. This effect is not explained by simple theories of ion-induced dipole interactions. It is suggested that the enhanced rate of the PH⁺₄Ca reaction may be due to d-orbital participation.     

Study of the structure of molecular complexes. Coordination numbers for Li+, Na+, K+, F− and Cl− in water

A cluster of 200 water molecules containing a single ion (either Li⁺ or Na⁺ or K⁺ or F^? or Cl^?) has been studied at T = 298 K using Monte Carlo techniques. The waterwater interaction is obtained from a quantum-mechanical study of CI type; the ionwater potentials have been obtained from HartreeFock type computations. The computed coordination numbers in the first shell for Li⁺, Na⁺, K⁺, F^? and Cl^? are 4.0, 4.3, 5.1, 3.85 and 4.3, respectively; the corresponding first hydration shell radii are 2.28 Å, 2.59 Å, 3.27 Å, 1.99 Å and 2.85 Å, respectively. A discussion of the second and third hydration shell radii and coordination numbers is given.     

Solvent extraction of H3O+, NH4+, Ag+, K+, Rb+ and Tl+ into nitrobenzene by using cesium dicarbollylcobaltate in the presence of a hexaarylbenzene-based receptor

From extraction experiments and γ-activity measurements, the extraction constants corresponding to the general equilibrium M⁺(aq) + 1·Cs⁺(nb) \rightleftarrows \rightleftarrows 1·M⁺(nb) + Cs⁺(aq) taking part in the two-phase water–nitrobenzene system (1 = hexaarylbenzene-based receptor; M⁺ = H₃O⁺, NH₄ ⁺, Ag⁺, K⁺, Rb⁺, Tl⁺; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complex species in nitrobenzene saturated with water were calculated; they were found to increase in the series of Rb⁺ < K⁺ < Ag⁺, Tl⁺ < H₃O⁺, NH₄ ⁺.