Physical properties of 3-methyl-N-butylpyridinium tetracyanoborate and 1-butyl-1-methylpyrrolidinium tetracyanoborate and ternary LLE data of [3-mebupy]B(CN)4 with an aromatic and an aliphatic hydrocarbon at T = 303.2 K and 328.2 K and p = 0.1 MPa

Several physical properties were determined for the ionic liquids 3-methyl-N-butylpyridinium tetracyanoborate ([3-mebupy]B(CN)₄) and 1-butyl-1-methylpyrrolidinium tetracyanoborate ([1-mebupyr]B(CN)₄), viz. liquid density, viscosity, surface tension, thermal stability, and heat capacity over the temperature range from 283.2 K to 475.2 K and at 0.1 MPa. The density and the surface tension were well correlated with linear equations and the viscosity with a Vogel–Fulcher–Tamman equation. The IL [3-mebupy]B(CN)₄ is stable up to a temperature of 480 K and the IL [1-mebupyr]B(CN)₄ up to a temperature of 548 K.Ternary data for the systems {(benzene + n-hexane), or (toluene + n-heptane), or (p-xylene + n-octane + [3-mebupy]B(CN)₄)} were determined at T = 303.2 K and 328.2 K and p = 0.1 MPa. All experimental data were well correlated with the NRTL model. The values of the experimental and calculated aromatic/aliphatic selectivity are in good agreement with each other. The LLE data of [1-mebupyr]B(CN)₄ were only measured in a 10 vol% aromatic feed for the three systems.     

A topographic view of the Pt(1 1 1) surface at the electrochemical interface in the presence of carbon monoxide

In this communication we present topographic images of the Pt(1 1 1) surface in CO saturated 0.1 M HClO₄, obtained by scanning tunneling microscopy.The topography presents two different structures, depending on the CO adsorption potential (E_ad = 0.15 V or E_ad = 0.5 V vs RHE). For adsorption at 0.15 V the system presents a heterogeneous appearance, which totally covers the surface and impedes the observation of steps on the substrate surface. When CO is adsorbed at 0.5 V large clusters forming chains along the steps are observed. These aggregates can be, tentatively, correlated with the H-bonded water structure suggested earlier on the basis of FTIR spectroscopy. The clusters have inhibitory effects on CO oxidation.     

Identifying spectator bonds in modeling reactions: OH + CO → H + CO2

An adiabatic quantum dynamical model is introduced to solve a paradox with respect to the role of the CO vibration in the OH + CO(v) → H + CO₂ reaction. The previous agreement of five-dimensional diabatic with six-dimensional results for CO(v = 0), which erroneously suggested that the CO bond acts as a spectator, is due to a compensation of effects. For CO(v = 1), the reduced dimensionality adiabatic model approximates better the full-dimensional results. Whether AB acts as a spectator in a reaction with X cannot be decided on the basis of a diabatic calculation for AB(v = 0) + X only.     

The molecular orientation of CO on Pd(1 1 1): a polarization-dependent SFG study

The molecular orientation of carbon monoxide adsorbed on Pd(1 1 1) was examined by sum frequency generation (SFG) vibrational spectroscopy utilizing different polarization combinations of the visible and SFG light. This allows to determine the CO tilt angle with respect to the substrate, provided that a proper optical model for the interface can be defined. It is demonstrated that it is essential to invoke the β_aac hyperpolarizability into the analysis and that polarization-dependent SFG of CO/Pd(1 1 1) yields information on β_aac/β_ccc rather than the tilt angle.     

Hot band spectroscopy of CCO in the C–O stretching region: The (ν1 + 2ν3) − 2ν3 and (2ν1 + ν3) − (ν1 + ν3) bands

Two C–O stretching hot bands, (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), of the CCO radical in the ground electronic state were measured. These hot bands are red shifted by approximately 70 cm⁻¹ compared to the C–O stretching fundamental. CCO was produced in a discharge through a flowing mixture of carbon suboxide and helium. The spectra were recorded using a diode laser spectrometer. The band origins were determined to be 1904.32512(62) and 1902.69130(56) cm⁻¹ for (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), respectively. The measurements in this band together with previously reported frequencies in the C–C and C–O stretching regions were analysed to determine harmonic frequencies and anharmonicity constants.     

Voltammetric characterization of stepped platinum single crystal surfaces vicinal to the (1 1 0) pole

Platinum stepped surfaces vicinal to the (1 1 0) crystallographic pole have been investigated voltammetrically in 0.1 M HClO₄ and 0.1 M H₂SO₄ solutions. Changes in the voltammetric profile with the step density suggest the existence of two types of surface sites, that has been ascribed to linear and bidimensional domains. This result indicates the existence of important restructuring processes that separate the real surface distribution from the nominal one. The electronic properties of the surfaces have been characterized with the CO charge displacement method and the potential of zero total charge has been calculated as a function of the step density.     

Thermochemical behavior of crown ethers in the mixtures of water with organic solvents. Part VIII. Hydrophobic hydration and preferential solvation of 1,4-dioxane in {(1 − x)amide + xH2O} at T = 298.15 K

The enthalpies of solution of 1,4-dioxane in {(1 − x)F + xH₂O}, {(1 − x)NMF + xH₂O}, and {(1 − x)DMF + xH₂O} have been measured within the whole mole fraction range at T = 298.15 K. Based on the obtained data, the effect of substituting methyl groups at the nitrogen atom in formamide on the preferential solvation of 1,4-dioxane has been analyzed. A simple model has been proposed to describe the influence of structural and energetic properties of the mixed solvent on the energetic effect of hydrophobic hydration and preferential solvation of 1,4-dioxane by the components of the examined mixture.     

Excess molar volumes of (an alkane + 1-chloroalkane) atT = 298.15 K

The densities of the following: (pentane  +  1-chloropropane, or 1-chlorobutane, or 1-chloropentane, or 1-chlorohexane), (hexane  +  1-chloropropane, or 1-chlorobutane, or 1-chloropentane, or 1-chlorohexane), (heptane  +  1-chloropropane, or 1-chlorobutane, or 1-chloropentane, or 1-chlorohexane), (octane  +  1-chloropropane, or 1-chlorobutane, or 1-chloropentane, or 1-chlorohexane), were measured at T =  298.15 K by means of a vibrating-tube densimeter. The excess molar volumes V_m^E, calculated from the density data, are negative for (pentane  +  1-chloropentane, or 1-chlorohexane) and (hexane  +  1-chlorohexane) over the entire range of composition. (Pentane  +  1-chlorobutane), (hexane  +  1-chloropentane) and (heptane  +  1-chlorohexane) exhibit an S-shapedV_m^E dependence. For all the other systems,V_m^E is positive. The V_m^Eresults were correlated using the fourth-order Redlich–Kister equation, with the maximum likelihood principle being applied for determining the adjustable parameters.     

Volumetric and viscometric behaviour of binary systems: (1-hexanol + hydrocarbons)

Densities and viscosities of binary liquid mixtures of (1-hexanol  + n -hexane, or cyclohexane, or benzene) have been measured at a number of mole fractions at T =  (303, 313, and 323) K. The excess molar volume V_m^Eand apparent molar volume V_φhave been calculated from the density data. TheV_m^E anddV_m^E / dT for the system, (1-hexanol  + n -hexane) have been found negative, while those for the systems, (1-hexanol  +  cyclohexane) and (1-hexanol  +  benzene), were found to be positive. Excess viscosities η^Ecalculated from viscosity data, have been found to be negative over the whole composition range at the temperatures studied for all the three systems. Volumetric and viscometric behaviours indicate that dispersion is the major force of interaction between the components in (1-hexanol  +  cyclohexane, or benzene), while inclusion of hydrocarbon chains into the interstices of polymolecular ring structures of alcohol formed by hydrogen bonding has been assumed to play a significant role apart from dispersion in the system (1-hexanol  + n -hexane). Thermodynamic parameters of activation for viscous flow have been calculated from the viscosity data at different temperatures and a possible explanation suggested.     

Calorimetric investigation of mixing enthalpy of liquid (Co + Cu + Zr) alloys at T = 1873 K

The enthalpies of mixing of liquid (Co + Cu + Zr) alloys have been determined using the high-temperature isoperibolic calorimeter. The measurements have been performed along three sections (x_Co/x_Cu = 3/1, 1/1, 1/3) with x_Zr = 0 to 0.55 at T = 1873 K. Over the investigated composition range, the partial mixing enthalpies of zirconium are negative. The limiting partial enthalpies of mixing of undercooled liquid zirconium in liquid (Co + Cu) alloys are (−138 ± 18) kJ · mol⁻¹ (the section x_Co/x_Cu = 3/1), (−155 ± 10) kJ · mol⁻¹ (the section x_Co/x_Cu = 1/1), and (−130 ± 22) kJ · mol⁻¹ (the section x_Co/x_Cu = 1/3). The integral mixing enthalpies are sign-changing. The isenthalpic curves have been plotted on the Gibbs triangle. The main features of the composition dependence of the integral mixing enthalpy of liquid ternary alloys are defined by the pair (Co + Zr) and (Cu + Zr) interactions.     

Speeds of sound in {(1 − x)CH4 + xN2} with x = (0.10001, 0.19999, and 0.5422) at temperatures between 170 K and 400 K and pressures up to 30 MPa

The speed of sound in {(1 − x)CH₄ + xN₂} has been measured with a spherical acoustic resonator. Two mixtures with x = (0.10001 and 0.19999) were studied along isotherms at temperatures between 220 K and 400 K with pressures up to 20 MPa; a few additional measurements at p = (25 and 30) MPa are also reported. A third mixture with x = 0.5422 was studied along pseudo-isochores at amount-of-substance densities between 0.2 mol · dm⁻³ and 5 mol · dm⁻³. Corrections for molecular vibrational relaxation are discussed in detail and relaxation times are reported. The overall uncertainty of the measured speeds of sound is estimated to be not worse than ±0.02%, except for those measurements in the mixture with x = 0.5422 that lie along the pseduo-isochore at the highest amount-of-substance density. The results have been compared with the predictions of several equations of state used for natural gas systems.     

Study of bromide salts solubility in the (m1NaBr + m2MgBr2)(aq) system at T = 323.15 K. Thermodynamic model of solution behavior and (solid + liquid) equilibria in the (Na + K + Mg + Br + H2O) system to high concentration and temperature

The bromide minerals solubility in the mixed system (m₁NaBr + m₂MgBr₂)(aq) have been investigated at T = 323.15 K by the physico-chemical analysis method. The equilibrium crystallization of NaBr·2H₂O(cr), NaBr(cr), and MgBr₂·6H₂O(cr) has been established. The solubility-measurements results obtained have been combined with all other experimental equilibrium solubility data available in literature at T = (273.15 and 298.15) K to construct a chemical model that calculates (solid + liquid) equilibria in the mixed system (m₁NaBr + m₂MgBr₂)(aq). The solubility modeling approach based on fundamental Pitzer specific interaction equations is employed. The model gives a very good agreement with bromide salts equilibrium solubility data. Temperature extrapolation of the mixed system model provides reasonable mineral solubility at high temperature (up to 100 °C). This model expands the previously published temperature variable sodium–potassium–bromide and potassium–magnesium–bromide models by evaluating sodium–magnesium mixing parameters. The resulting model for quaternary system (Na + K + Mg + Br + H₂O) is validated by comparing solubility predictions with those given in literature, and not used in the parameterization process. Limitations of the mixed solution models due to data insufficiencies at high temperature are discussed.     

An ab initio study of CO adsorption on ceria(1 1 0)

Hartree–Fock and DFT calculations are reported for the CO/CeO₂(1 1 0) surface system. The electron density, electrostatic potential, atomic charges and projected electronic density of states have been calculated from an ECP-and-point-charge-embedded cluster model and is compared with periodic calculations. The agreement between the two surface models is reasonably good. A number of weakly bonding CO adsorption sites were found, with E_ads (BSSE-corrected) ranging from 0.01 to 0.22 eV per adsorbed molecule. The two most favourable sites are found in the vicinity of surface cerium ions, with the CO molecule oriented in a tilted fashion, C-end down. The surface-induced CO stretching vibrational frequency shifts on these sites are a redshift of ≈−30 cm⁻¹ and a blueshift of ≈25 cm⁻¹, respectively.     

(Solid + solute) phase equilibria in aqueous solution. XIII. Thermodynamic properties of hydrozincite and predominance diagrams for (Zn2 + + H2O + CO2)

The thermodynamic properties ofZn₅(OH)₆(CO₃)₂ , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO₄media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I =  1.00 mol · kg ^− 1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I =  3.00 mol · kg ^− 1NaClO₄at T =  298.15 K. The standard molar heat capacity C_{p, m}^ofunction fromT =  318.15 K to T =  418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T =  298.15 K): solubility constant log ^* K_{ps 0}⁰ =  (9.0  ±  0.1), standard molar Gibbs energy of formationΔ_fG_m^o {Zn₅(OH)₆(CO₃)₂ }  =  ( − 3164.6  ±  3.0)kJ · mol ^− 1, standard molar enthalpy of formation Δ_fH_m^o{Zn₅(OH)₆(CO₃)₂ }  =  ( − 3584  ±  15)kJ · mol ^− 1, standard molar entropy S_m^o{Zn₅(OH)₆(CO₃)₂ }  =  (436  ±  50)J · mol ^− 1· K ^− 1and C_p,m^o / (J · mol ^− 1· K ^− 1)  =  (119  ±  11)  +  (0.834  ±  0.033)T / K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn^2 +  +  H₂O  +  CO₂) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO₃) / n(Zn)} of the solid compoundsZnCO₃ and Zn₅(OH)₆(CO₃)₂can be checked by thermodynamically analysing the measured solubility data.     

Electrochemical deposition of PbTe onto n-Si(1 0 0) wafers

Electrochemical deposition of PbTe from 50 mM Pb(NO₃)₂ + 1 mM TeO₂ + 0.1 M HNO₃ solution onto n-Si(1 0 0) wafers was studied using cyclic voltammetry (CV), chronoamperometry, ex situ SEM, XRD and EDX. Electrochemical behavior of n-Si(1 0 0) electrode in electrolytes 50 mM Pb(NO₃)₂ + 0.1 M HNO₃ and 1 mM TeO₂ + 0.1 M HNO₃ was also studied. No underpotential deposition (UPD) of Pb and Te onto n-Si was observed in the investigated systems indicating weak Pb–Si and Te–Si interactions. Deposition of Pb and Te on n-Si occurred with overvoltage via 3D island growth. Electrosynthesis of PbTe (NaCl-like structure, a = 0.650 nm) takes place due to codeposition of Pb and Te at potentials E > E_{Pb²⁺/Pb⁰} (lead UPD onto tellurium). Cathodic deposition of PbTe onto n-Si(1 0 0) is irreversible – there is no anodic current in the CV curve. Oxidation of PbTe on n-Si is observed only under illumination, when photoelectrons and photoholes are generated in silicon substrate.     

Thermodynamic properties of (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures at T = (298.15, 303.15, and 308.15) K

Density ρ, viscosity η, and refractive index n_D, values for (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures over the entire range of mole fraction have been measured at temperatures (298.15, 303.15, and 308.15) K at atmospheric pressure. The speed of sound u has been measured at T = 298.15 K only. Using these data, excess molar volume V^E, deviations in viscosity Δη, Lorentz–Lorenz molar refraction ΔR, speed of sound Δu, and isentropic compressibility Δk_s have been calculated. These results have been fitted to the Redlich and Kister polynomial equation to estimate the binary interaction parameters and standard deviations. Excess molar volumes have exhibited both positive and negative trends in many mixtures, depending upon the nature of the second component of the mixture. For the (tetradecane + chlorobenzene) binary mixture, an incipient inversion has been observed. Calculated thermodynamic quantities have been discussed in terms of intermolecular interactions between mixing components.     

Adsorption of hydrogen on Pt(1 1 1) and Pt(1 0 0) surfaces and its role in the HOR

Hydrogen adsorption isotherms, evaluated by combination of cyclic voltammetry and chronoamperometry, are reported on Pt(1 1 1) and Pt(1 0 0) surfaces in 0.1 M HClO₄. We found that at E > 0.05 V Pt(1 1 1) and Pt(1 0 0) are only partially covered by the adsorbed hydrogen (H_ad). On both surfaces, a full monolayer of the adsorbed hydrogen is completed at −0.1 V, i.e. the adsorption of atomic hydrogen is observed in the hydrogen evolution potential region. We also found, that the activity of the hydrogen oxidation reaction is mirrored by the shape of the hydrogen adsorption isotherms, implying that H_ad is in fact a spectator in the HOR.     

Comparative theoretical study of the structure and bonding of propyne on the Pt(1 1 1) and Pd(1 1 1) surfaces

The interaction of propyne with the Pt(1 1 1) and Pd(1 1 1) surfaces has been studied by means of the generalised gradient approach of density functional theory using periodic slab models. For both surfaces, the most stable adsorption mode of propyne is di-σ/π mode where the hydrocarbon is σ-bonded to two metal atoms with some additional π bonding to a third adjacent surface atom. The adsorption geometry is a highly distorted propyne with the C₁ and C₂ in a nearly sp² hybridisation. Two equivalent surface structures have been found on Pt and Pd. These correspond to the adsorption on the fcc or hcp hollow sites. The adsorption energies on Pt(1 1 1) and Pd(1 1 1) are predicted to be ∼−197 and −161 kJ mol⁻¹, respectively. The electronic factors that control the chemisorption have been analysed by means of the projected density of states.     

Synthesis,structure and magnetic properties of 2-D and 3-D [cation]{M[Au(CN)2]3} (M = Ni, Co) coordination polymers

In order to study the templating effect of the cation and the resulting impact on the magnetic properties, reactions of M(II) salts with [cation][Au(CN)₂] were conducted, yielding a series of coordination polymers of the form [cation]{M[Au(CN)₂]₃} (cation = ⁿBu₄N⁺, PPN⁺ (bis(triphenylphosphoranylidene)ammonium); M = Ni(II) and Co(II)). The structures of ⁿBu₄N{M[Au(CN)₂]₃} and PPN{M[Au(CN)₂]₃} (M = Ni and Co) contain two distinct 3-D anionic frameworks of {M[Au(CN)₂]₃}⁻, hence the framework was sensitive to the cation, but not to the identity of the metal center. In ⁿBu₄N{M[Au(CN)₂]₃}, the metal centers are connected by [Au(CN)₂] units to form six 2-D (4, 4) rectangular grids that are fused through the M centers to yield a complex three-dimensional framework which accommodates the ⁿBu₄N⁺ cations. In PPN{M[Au(CN)₂]₃}, the framework adopts a simpler non-interpenetrated Prussian-blue-type pseudo-cubic array, with the PPN⁺ cations occupying each cavity; no reduction in dimensionality occurs despite the large cation size. In the presence of water, {Co(H₂O)₂[Au(CN)₂]₂} · ⁿBu₄N[Au(CN)₂] was obtained, a 2-D layered polymer that contains neutral sheets of {Co(H₂O)₂[Au(CN)₂]₂} which are separated by ⁿBu₄N[Au(CN)₂] layers; aurophilic interactions of 3.4250(13) Å and hydrogen-bonding connect the layers. The magnetic properties of all compounds were investigated by SQUID magnetometry. The Ni(II) polymers have similar magnetic behaviour, which are dominated by zero-field splitting with very weak antiferromagnetic interactions at low temperature (D ∼ 2–3 cm⁻¹, zJ < 1 cm⁻¹). The magnetic behaviour of all of the Co(II) polymers were found to be very similar, and dominated by single-ion effects (i.e. a large first-order orbital contribution). No significant magnetic coupling is observed in any of these coordination polymers, suggesting that the [Au(CN)₂] bridging unit behaves as a poor mediator of magnetic exchange in these high-dimensionality systems.     

Critical behaviour of { water + n-nonane + sodium di(2-ethyl-1-hexyl)sulphosuccinate } microemulsions

Coexistence curves of ( T, n), ( T, ϕ), and ( T, Ψ), where n, ϕ, and Ψ are the refractive index, volume fraction and effective volume fraction ψ = ϕ / {ϕ +  [(1  − ϕ )ϕ_c / (1  − ϕ_c )]}, respectively, for ternary microemulsion systems of {water  + n -nonane  +  sodium di(2-ethyl-1-hexyl)sulphosuccinate} have been determined at temperatures within 8.7 K above the critical temperature by measurements of refractive index at constant pressure and a constant molar ratio of water to sodium di(2-ethyl-1-hexyl)sulphosuccinate. The critical exponent β deduced from ( T,n ), ( T, ϕ), and ( T, Ψ) coexistence curves was found consistent with nonmonotonic crossover observed in all aqueous ionic solutions. The values of β deduced from the experimental data in the range of 1 K above T_cwere consistent with the universality class of three-dimensional Ising-like systems. The coexistence curves have been interpreted by a combination of the Wegner expansion and the rectilinear diameter. The present results indicate that the molar mass dependence of critical amplitudes, we proposed recently, is valid for microemulsion systems.