Pressure and isotope effects on the proton jump of the hydroxide ion at 25°C

The limiting molar conductances Λ⁰ of potassium deuteroxide KOD in D₂O and potassium hydroxide KOH in H₂O were determined at 25°C as a function of pressure to disclose the difference in the proton-jump mechanism between an OH^? (OD^?) and a H₃O⁺ (D₃O⁺) ion. The excess conductance of the OD^? ion in D₂O λ _E ^O (OD ^-), as estimated by the equation $$\lambda _E^O (OD^ - ) = \Lambda ^O (KOD/D_2 O) - \Lambda ^O (KCl/D_2 O)$$ increases a little with pressure as well as the excess conductance of the OH^? ion in H₂O $$\lambda _E^O (OH^ - ) = \Lambda ^O (KOH/H_2 O) - \Lambda ^O (KCl/H_2 O)$$ However, their rates of increase with pressure are much smaller than those of the excess deuteron and proton conductances, λ _E ^O (D ⁺) and λ _E ^O (H ⁺). With respect to the isotope effect on the excess conductance, λ _E ^O (OH ^-)/λ _E ^O (D ⁺) decreases with presure as in the case of λ _E ^O (H ⁺)/λ _E ^O (D ⁺), but the value of λ _E ^O (OH ^-)/λ _E ^O (OD ^-) itself is much larger than that of λ _E ^O (H ⁺)/λ _E ^O (D ⁺) at each pressure. These results are ascribed to the difference in the pre-rotation of water molecules, which is brought about by the difference in the intial orientation of the rotating water molecule adjacent to the OH^? (OD^?) or the H₃O⁺ (D₃O⁺) ion.     

Kinetic energy release of clusters after multiphoton ionisation with time of flight and electrostatic analyser techniques

A new technique is presented which allows direct observation of initial kinetic energies in multiphoton ionisation-fragmentation processes of molecules and clusters and provides an unambiguous determination of metastable decay channels. Results are presented for the unimolecular loss of a monomer from clusters (C₆H₆) ₈ ⁺ to (C₆H₆) ₁₂ ⁺ and for the reaction C₆H ₆ ⁺ →C₄H ₄ ⁺ +C₂H₂. We also observe a significant amount of probably collision induced fragmentation processes (C₆H₆) _n ⁺ →(C₆H₆) _n?x ⁺ + (C₆H₆) _x withx much larger than 1.     

Analytical photoion spectroscopy applied to dissociative single and double photoionization of diatomic molecules (H2, N2, O2, CO,and NO)

This work reports the principle, advantage, and limitations of analytical photoion spectroscopy which has been applied to dissociative photoionization processes for diatomic molecules such as H₂, N₂, CO, and NO. Characteristic features observed in the differential photoion spectra are summarized with a focus on (pre)dissociation of(i) multielectron excitation states commonly observed in the inner valence regions,(ii) shape resonances, and(iii) doubly charged parent ions. Possible origins for negative peaks in the differential spectra are discussed. This spectroscopy is applied to the reported photoion branching ratios for D₂ (and H₂ at high energies). The main findings are as follows: (1) The direct dissociation of theX ²Σ _g ⁺ (1sσ _g ) state of D ₂ ⁺ , the two-electron excited state¹Σ _u ⁺ (2pσ _u 2sσ _g ) of D₂, and the²Σ _u ⁺ (2pσ _u ) state of D ₂ ⁺ appear clearly in the differential spectrum, as previously observed for H₂. (2) Decay of H ₂ ⁺ (D ₂ ⁺ ) to H⁺ (D⁺) above 38 eV is due to the direct dissociation of highly excited states of H ₂ ⁺ (D ₂ ⁺ ) such as the²Σ _g ⁺ (2sσ _g ) and high-lying Rydberg states converging on H ₂ ²⁺ (D ₂ ²⁺ ). (3) In the ionization continuum of H ₂ ²⁺ (D ₂ ²⁺ ) peculiar dissociation pathways are observed. The differential photoion spectra for O₂ derived from the reported photoion branching ratios are also presented. The (pre)dissociation of theb ⁴Σ _g ^? ,B ²Σ _g ^? , III²Π _u ,²Σ _u ^? , and^2,4Σ _g ^? states of O ₂ ⁺ appears as the corresponding positive values in the spectra in accord with previous observations. Some other dissociation pathways possibly contributing to the spectra are discussed including dissociative double ionization.     

Observations of magic numbers in gas phase hydrates of alkylammonium ions

Hydration of alkylammonium ions under nonanalytical electrospray ionization conditions has been found to yield cluster ions with more than 20 water molecules associated with the central ion. These cluster ion species are taken to be an approximation of the conditions in liquid water. Many of the alkylammonium cation mass spectra exhibit water cluster numbers that appear to be particularly favorable, i.e., “magic number clusters” (MNC). We have found MNC in hydrates of mono- and tetra-alkyl ammonium ions, NH₃(C _m H_2m+1)⁺(H₂O) _n , m=1–8 and N(C _m H_2m+1) ₄ ⁺ (H₂O) _n , m=2–8. In contrast, NH₂(CH₃) ₂ ⁺ (H₂O) _n , NH(CH₃) ₃ ⁺ (H₂O) _n1 and N(CH₃) ₄ ⁺ (H₂O) _n do not exhibit any MNC. We conjecture that the structures of these magic number clusters correspond to exohedral structures in which the ion is situated on the surface of the water cage in contrast to the widely accepted caged ion structures of H₃O⁺(H₂O) _n and NH ₄ ⁺ (H₂O) _n .     

Formation of helium cluster ions HHe x + (x≦14) and H3He x + (x≦13) in a very low temperature drift tube

The formation of cluster ions when hydrogen molecular ions H ₂ ⁺ and H ₃ ⁺ are injected into a drift tube filled with helium gas at 4.4 K has been investigated. When H ₂ ⁺ ions are injected, cluster ions HHe _x ⁺ (x≦14) are produced. No production of H₂He _x ⁺ ions is observed. When H ₃ ⁺ ions are injected, cluster ions HHe _x ⁺ (x≦14) are produced as well as H₃He _x ⁺ (x≦13), and very small signals corresponding to H₂He _x ⁺ (3≦x≦10) are observed. Information on the stability of HHe _x ⁺ and H₃He _x ⁺ is derived from the drift field dependence of the cluster size distributions. The cluster sizex=13 is found to be a magic number for HHe _x ⁺ , and for H₃He _x ⁺ ,x=10 and 11.     

The enthalpies of solution and solvation of glycine in mixed water-formamide solvents at 298.15 K

The enthalpies of solution (ΔH _sol ^o ) of glycine in aqueous formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were determined by calorimetry at 298.15 K over the concentration range x ₂=0–0.3 mole fractions. The enthalpies of glycine solvation (ΔH _solv ^o ) and transfer from water to mixed solvents (ΔH _tr ^o ) were calculated. The ΔH _sol ^o =f(x ₂) dependences for glycine in water-N-and water-N,N-substituted amide mixtures had extrema and, in water-formamide mixtures, this dependence was a smooth function, whose values changed in the opposite direction. The enthalpy coefficients of pair glycine-amide interactions were calculated. The interrelation between the enthalpy characteristics of solution, transfer, and solvation of glycine and the structure and physicochemical characteristics of solvents, on the one hand, and the composition of mixtures, on the other, was revealed.     

Equilibria of aqueous solutions of isopolyniobotungstates-6 with c Nb : c W = 1 : 5

Complex formation in the Nb₆O ₁₉ ^8? -WO ₄ ^2? -H⁺-H₂O system with c _Nb : c _W = 1 : 5 and varied c _{Nb + W} ⁰ = 10^?2, 5 × 10^?3, 2.5 × 10^?3, and 10^?3 mol/L) has been studied. Distribution diagrams were simulated for individual niobium(V) and tungsten(VI) isopolyanions and mixed isopolyniobotungstates for $Z = \frac{{c_{H^ + }^0 }}{{c_{Nb + W}^0 }} = 0 - 3.0$ in an NaCl background electrolyte. We have shown that isopolyniobotungstates-6 of composition H _x NbW₅O ₁₉ ^{(3 ? x)?} are formed via H _x Nb _n W_6?n O ₁₉ ^{(2 + n ? x)?} (n=2, 3, 5) ions. The concentration formation constants and thermodynamic formation constants of isopolyniobotungstate anions (IPNTAs) in aqueous solution have been calculated. Salt Tl₃NbW₅O₁₉·9H₂O has been synthesized and identified by chemical analysis and IR spectroscopy.     

Collision-induced dissociation evidence for charge separation and “ball-and-chain” propagation in the addition of 1-butene to C 60 2+

The collision-induced dissociation of the adduct ions C₆₀(C₄H₈) ₂ ²⁺ and C₆₀(C₄H₈) ₃ ²⁺ formed by sequential reactions of C ₆₀ ²⁺ with 1-butene has been investigated by using a selected-ion flow tube (SIFT) apparatus. Experiments at 295 ± 2 K in 0.35 ± 0.02 torr of helium indicated that C ₆₀ ²⁺ adds at least five molecules of 1-butene in a sequential fashion with rates that decrease with the number of molecules added. Collision-induced dissociation experiments in which the downstream sampling nose cone of the SIFT was biased with respect to the flow tube indicated that the adduct ions C₆₀(C₄H₈) ₂ ²⁺ and C₆₀(C₄H₈) ₃ ²⁺ dissociate into C ₆₀ ^·+ and (C₄H₈) ₂ ^·+ and (C₄H₈) ₃ ^·+ , respectively. These observations provide evidence for the occurrence of charge separation in the derivatization of C₆₀ dications and support the “ball-and-chain” mechanism first proposed by Wang et al. in 1992 for the sequential multiple addition of 1,3-butadiene to C ₆₀ ²⁺ and C ₇₀ ²⁺ .     

Quantum chemical DFT calculations of the local structure of the hydrated electron and dielectron

The adiabatic bound state of an excess electron is calculated for a water cluster (H₂O) ₈ ^? in the gas phase using the DFT-B3LYP method with the extended 6-311++G(3df,3pd) basis set. For the liquid phase the calculation is performed in the polarizable continuum model (PCM) with regard to the solvent effect (water, ? = 78.38) in the supermolecule-continuum approximation. The value calculated by DFT-B3LYP for the vertical binding energy (VBE) of an excess electron in the anionic cluster (VBE(H₂O) ₈ ^? = 0.59 eV) agrees well with the experimental value of 0.44 eV obtained from photoelectron spectra in the gas phase. The VBE value of the excess electron calculated by PCM-B3LYP for the (H₂O) ₈ ^? cluster in the liquid phase (VBE = 1.70 eV) corresponds well to the absorption band maximum λ_max = 715 nm (VBE = 1.73 eV) in the optical spectrum of the hydrated electron hydr e _hydr ^? . Estimating the adiabatic binding energy (ABE)e _hydr ^t- in the (H₂O) ₈ ^? cluster (ABE = 1.63 eV), we obtain good agreement with the experimental free energy of electron hydration ΔG ₂₉₈ ⁰ (e _hydr ^? ) = 1.61 eV. The local model (H₂O) ₈ ^2? of the hydrated dielectron is considered in the supermolecule-continuum approximation. It is shown that the hydrated electron and dielectron have the same characteristic local structure: -O-H{↑}H-O- and -O-H{↑↓}H-O-respectively.     

Synthesis, crystal structure, and luminescent properties of a silver(I) perrhenate complex with phenazine

The silver complex with phenazine [Ag(Phz)₂(H₂O)]ReO₄ (Phz is C₁₂H₈N₂) has been synthesized, and its crystal structure has been determined. The crystals are triclinic: space group $P\bar 1$ , a = 9.587(1) Å, b = 10.875(1) Å, c = 11.668(1) Å, α = 104.98(1)°, β = 103.87(1)°, γ = 92.94(1)°, V = 1132.6(2) ų, Z = 2, ρ_calc = 2.160 g/cm³. The structure is composed of the [Ag(Phz)₂(H₂O)]⁺ silver cationic complexes and ReO ₄ ^? anions. The Ag⁺ ion is coordinated by two nitrogen atoms of independent phenazine molecules and the water oxygen atoms and has a T-shaped coordination (Ag-N_av 2.223 Å, Ag-O_w 2.498(8) Å). Phenazine, being an electron-donor ligand, forms columns due to π-π stacking interaction between the aromatic groups. The water molecules form hydrogen bonds with the oxygen atoms of water molecules of neighboring complexes and with oxygen atoms of the ReO ₄ ^? anions.     

Redox, complexation, and substitution reactions in [Cu2B10H10]-2,2′-bipyridylamine-CH3CN system

Reaction of [Cu₂B₁₀H₁₀] with 2,2′-bipyridylamine (bpa) in acetonitrile was studied. A redox reaction was found to proceed in reaction solution at ambient temperature. Copper coordination compounds with the metal of different oxidation states—[Cu ₂ ^I (bpa)₂B₁₀H₁₀] · 2NCCH₃, [Cu ₄ ^II (bpa)₄(OH)₄][Cu ₂ ^I (B₁₀H₁₀)₃] · nNCCH₃, [Cu^II(bpa)₂(NCCH₃)₂](2-B₁₀H₉bpa)₂ · 2H₂O, [Cu ₂ ^II (bpa)₂(OH)₂B₁₀H₁₀], and [(Cu ₂ ^II (bpa)₂(CO₃)₂] · H₂O—were isolated under various reaction conditions. The compounds were characterized by IR spectroscopy, X-ray crystallography, and elemental analysis.     

Study of ionic equilibria and computation of thermodynamic characteristics of heteropoly anion formation in GdW10O 36 9− solution

Interaction in GdW₁₀O ₃₆ ^9? -H⁺(OH^?)-H₂O system ( \(C_{GdW_{10} O_{36}^{9 - } } \) = 1 × 10^?3 mol/L) was studied by pH potentiometry at 25 ± 0.1°C, and a model that describes equilibrium processes in acid and alkaline regions was selected. Logarithms of concentrational and thermodynamic constants, values of Gibbs energy of monomeric ions reactions, and standard Gibbs energies of formation (ΔG _f ^o ) of heteropoly anions H _n GdW₁₀O ₃₆ ^(9?n)? and H _m GdW₅O ₁₈ ^(3?n)? were calculated. A series-parallel scheme of ion transitions was pro-posed, ion distribution diagrams in aqueous solutions were built, the regions of preferable anion content were found, and heteropoly salts were synthesized.     

4-hydroxy-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxide-oxalohydrazide (1:1): X-ray structure and DFT calculations

The title compound, 4-hydroxy-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxide-oxalohydrazide (1:1), is determined using X-ray diffraction techniques and the molecular structure is also optimized at the B3LYP/6-31G(d,p) level using density functional theory (DFT). The asymmetric unit consists of four independent molecules. The oxalohydrazide molecules have the centre of symmetry at the mid-point of the central C-C bond. Each thiazine ring adopts a half-chair conformation. Intermolecular C-H...O, N-H...O and N-H...N hydrogen bonds produce R ₂ ² (10), R ₂ ² (13), R ₃ ³ (12) and R ₃ ³ (15) rings, which lead to one-dimensional polymeric chains. An extensive three-dimensional supramolecular network of N-H...N, N-H...O, C-H...O and O-H...O hydrogen bonds is responsible for crystal structure stabilization.     

Crystal structure of Na2[(UO2)2(SeO4)3(H2O)2] · 6.5H2O

The compound Na₂[(UO₂)₂(SeO₄)₃(H₂O)₂] · 6.5H₂O (I) is studied using X-ray diffraction. The compound crystallizes in the monoclinic crystal system with the unit cell parameters a = 19.7366(8) Å, b = 10.8206(4) Å, c = 21.3577(8) Å, β = 103.4311(1)°, Z = 4, and the space group P2₁/c, R ₁ = 0.0379. Compound I is found to be a representative of the crystal-chemical group A₂T ₂ ³ B²M ₂ ¹ (A = UO ₂ ²⁺ ) of uranyl complexes and contains the cage group [(UO₂)₂(SeO₄)₃(H₂O)₂]^2?.     

FTMS studies of sputtered metal cluster ions (IV): size-selective effects in the chemistry of Fe n + with NH3 and Pd n + with D2 or C2H4

Fe _n ⁺ and Pd _n ⁺ clusters up ton=19 andn=25, respectively, are produced in an external ion source by sputtering of the respective metal foils with Xe⁺ primary ions at 20 keV. They are transferred to the ICR cell of a home-built Fourier transform mass spectrometer, where they are thermalized to nearly room temperature and stored for several tens of seconds. During this time, their reactions with a gas leaked in at low level are studied. Thus in the presence of ammonia, most Fe _n ⁺ clusters react by simply adsorbing intact NH₃ molecules. Only Fe ₄ ⁺ ions show dehydrogenation/adsorption to Fe₄(NH) _m ⁺ intermediates (m=1, 2) that in a complex scheme go on adsorbing complete NH₃ units. To clarify the reaction scheme, one has to isolate each species in the ion cell, which often requires the ejection of ions very close in mass. This led to the development of a special isolation technique that avoids the use of isotopically pure metal samples. Pd _n ⁺ cluster ions (n=2...9) dehydrogenate C₂H₄ in general to yield Pd _n (C₂H₂)⁺, yet Pd ₆ ⁺ appear totally unreactive. Towards D₂, Pd ₇ ⁺ ions seem inert, whereas Pd ₈ ⁺ adsorb up to two molecules.     

Dichlorotriethylphosphine-[N-formyl-N,N′-bis(3,4-dimethoxy)benzyl-trimethylenediamine] platinum(II)

By treatment of 1,3-bis(3,4-dimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium chloride (1) with KOBu ^t and [PtCl₂(PEt₃)₂]₂ N-coordinated platinum complex (2) is obtained. The Pt atom is coordinated in square planar arrangements by two chloride ions in a trans-configuration, the N-formyl-N,N′-bisaryltrimethylenediamine nitrogen atom, and the phosphine P atom. An extensive three-dimensional network of three C-H…O hydrogen bonds, two C-H…π and one π…π interactions are responsible for the crystal stabilization. Intermolecular hydrogen bonds and C-H…π interactions produce R ₂ ² (6), R ₂ ² (22), R ₂ ² (24), R ₃ ³ (23), R ₄ ⁴ (26), and R ₄ ⁴ (32) rings.     

Solubility characteristics of poly(ethylene oxide): Effect of molecular weight,end groups and temperature

The general solvation equation $${\text{Log }}L = c + r \cdot R_2 + s \cdot \pi _2^{\text{H}} + a \cdot \alpha _2^{\text{H}} + b \cdot \beta _2^{\text{H}} + l \cdot \log {\text{ }}L^{16} $$ has been used to evaluate the effect of molecular weight, hydroxyl end groups and temperature on the solubility characteristics of poly(ethylene oxide), PEO. In this equationL is the gas-liquid partition coefficient of a series of probes on PEO, and the explanatory variables are solute properties describing the excess molar refraction,R ₂, the probe dipolarity-polarisability, π ₂ ^H , and the probe hydrogen-bond acidity and basicity, α ₂ ^H and β ₂ ^H .L ¹⁶ is the gas-liquid partition coefficient of the probe onn hexadecane at 298 K. Ther·R ₂ andl·logL ¹⁶ terms increased with increase in molecular weight whereas thes·π ₂ ^H and a α ₂ ^H terms decreased; in all cases theb·α ₂ ^H term was not significant. Since thes-constant is a measure of polymer polarity-polarisability, and thea-constant a measure of polymer basicity, we deduce that these polymer properties decrease with increasing molecular weight. Chains with molecular weight below 3000 showed a more rapid decrease in basicity compared to the higher molecular weight species. Thes·π ₂ ^H ,a·α ₂ ^H andl·logL ¹⁶ terms all decreased with increase in temperature. Finally, the contribution of the terminal hydroxyl groups to the total polymer basicity was evaluated and discussed.     

Gas-phase reactivity of rare earth cations with phenol: Competitive activation of C-O, O-H, and C-H bonds

The gas-phase reactions of Sc⁺, Y⁺, and Ln⁺ (Ln=La-Lu, except Pm) ions with phenol were studied by Fourier transform ion cyclotron resonance mass spectrometry. All the ions except Yb⁺ were observed to react with the organic substrate, activating O-H, C-O, and/or C-H bonds, with formation of MO⁺, MOH⁺, and/or MOC₆H ₄ ⁺ ions as primary products. The product distributions and the reaction efficiencies obtained showed the existence of important differences in the relative reactivity of the rare earth metal cations, which are discussed in terms of factors like the electron configurations of the metal ions, their oxophilicity, and the second ionization energies of the metals. The primary product ions participated in subsequent reactions, yielding species such as M(OH)(OC₆H₅)⁺, which lead mainly to M(OC₆H₅)₂(HOC₆H₅) _n ⁺ ions, where n=0–2. Formation of M(OC₆H₅)(HOC₆H₅) _n ⁺ species was also observed in the case of the metals that have high stabilities of the formal oxidation state 2+, Sm and Eu.     

Synthesis and X-ray diffraction study of cs3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)] and Cs5[UO2(CH3COO)3]3[UO2(NCS)4(H2O)] · 2H2O

Cs₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] (I) and Cs₅[UO₂(CH₃COO)₃]₃[UO₂ (NCS)₄(H₂O)] · 2H₂O (II) have been synthesized via the reaction between uranyl acetate and cesium thiocyanate in aqueous solution. According to single-crystal X-ray diffraction data, both compounds crystallize in monoclinic system with the unit cell parameters a = 18.7036(5) Å, b = 16.7787(3) Å, c = 12.9636(3) Å, β = 92.532(1)°, space group C2/c, Z = 4, R = 0.0434 (I); and a = 21.7843(3) Å, b = 24.6436(5) Å, c = 13.1942(2) Å, β = 126.482(1)°, space group Cc, Z = 4, R = 0.0273 (II). Uranium-containing structural units of compound (I) are mononuclear [UO₂(CH₃COO)₃]^? and [UO₂(CH₃COO)(NCS)₂(H₂O)]^? moieties, which correspond to the AB ₃ ⁰¹ and AB⁰¹M ₃ ¹ crystallochemical groups (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?, M¹ = NCS^? and H₂O). The structure of compound II is built of [UO₂(CH₃COO)₃]^? and [UO₂(NCS)₄(H₂O)]^2? complexes, which belong to the AB ₃ ⁰¹ and AM ₅ ¹ crystallochemical groups, respectively. Uranium-containing complexes in both structures are linked into a framework by hydrogen bonds and electrostatic interactions with cesium cations. The IR spectra of compounds I and II agree well with X-ray diffraction data.