Preparation and electrochemical properties of {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} cathode materials for intermediate-temperature solid oxide fuel cells

Cathodic materials $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ (x?=?0.5, 0.6, 0.8, 1.0) with K₂NiF₄-type structure, for use in intermediate-temperature solid oxide fuel cells (IT-SOFCs), have been prepared by the glycine?Cnitrate process and characterized by XRD, SEM, AC impedance spectroscopy, and DC polarization measurements. The results have shown that no reaction occurs between an $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ electrode and an Sm_0.2Gd_0.8O_1.9 electrolyte at 1,200?°C, and that the electrode forms a good contact with the electrolyte after sintering at 1,000?°C for 2?h. In the series $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ (x?=?0.5, 0.6, 0.8, 1.0), the composition $ {\hbox{N}}{{\hbox{d}}_{{{1}.0}}}{\hbox{S}}{{\hbox{r}}_{{{1}.0}}}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ shows the lowest polarization resistance and cathodic overpotential, 2.75????cm² at 700?°C and 68?mV at a current density of 24.3?mA?cm^?2 at 700?°C, respectively. It has also been found that the electrochemical properties are remarkably improved the increasing Sr content in the experimental range.     

Infrared Spectroscopy of \hbox {CH}_4/\hbox {N}_{2} and \hbox {C}_{2}\hbox {H}_{m}/\hbox {N}_{2} ({m = 2, 4, 6}) Gas Mixtures in a Dielectric Barrier Discharge

Fourier transform infrared spectroscopy of \(\hbox {CH}_{4}/\hbox {N}_{2}\) and \(\hbox {C}_{2}\hbox {H}_{m}/\hbox {N}_2\) ( \(m = 2, 4, 6\) ) gas mixtures in a medium pressure (300 mbar) dielectric barrier discharge was performed. Consumption of the initial gas and formation of other hydrocarbon and of nitrogen-containing HCN and \(\hbox {NH}_{3}\) molecules was observed. \(\hbox {NH}_{3}\) formation was further confirmed by laser absorption measurements. The experimental result for \(\hbox {NH}_{3}\) is at variance with simulation results.     

Transport, thermomechanical, and electrode properties of perovskite-type {\left( {{\hbox{L}}{{\hbox{a}}_{0.{75} - x}}{\hbox{S}}{{\hbox{r}}_{0.{25} + x}}} \right)_{0.{95}}}{\hbox{M}}{{\hbox{n}}_{0.{5}}}{\hbox{C}}{{\hbox{r}}_{0.{5} - x}}{\hbox{T}}{{\hbox{i}}_x}{{\hbox{O}}_{{3} - }}_\delta \left( {x = 0 - 0.{5}} \right)

Increasing Sr²⁺ and Ti⁴⁺ concentrations in perovskite-type $ {\left( {{\hbox{L}}{{\hbox{a}}_{0.{75} - x}}{\hbox{S}}{{\hbox{r}}_{0.{25} + x}}} \right)_{0.{95}}}{\hbox{M}}{{\hbox{n}}_{0.{5}}}{\hbox{C}}{{\hbox{r}}_{0.{5} - x}}{\hbox{T}}{{\hbox{i}}_x}{{\hbox{O}}_{{3} - }}_\delta \left( {x = 0 - 0.{5}} \right) $ results in slightly higher thermal and chemical expansion, whereas the total conductivity activation energy tends to decrease. The average thermal expansion coefficients determined by controlled-atmosphere dilatometry vary in the range (10.8?C14.5)?×?10^?6?K^?1 at 373?C1,373?K, being almost independent of the oxygen partial pressure. Variations of the conductivity and Seebeck coefficient, studied in the oxygen pressure range 10^?18?C0.5?atm, suggest that the electronic transport under oxidizing and moderately reducing conditions is dominated by p-type charge carriers and occurs via a small-polaron mechanism. Contrary to the hole concentration changes, the hole mobility decreases with increasing x. The oxygen permeation fluxes through dense ceramic membranes are quite similar for all compositions due to very low level of oxygen nonstoichiometry and are strongly affected by the grain-boundary diffusion and surface exchange kinetics. The porous electrodes applied onto lanthanum gallate-based solid electrolyte exhibit a considerably better electrochemical performance compared to the apatite-type La₁₀Si₅AlO_26.5 electrolyte at atmospheric oxygen pressure, while Sr²⁺ and Ti⁴⁺ additions have no essential influence on the polarization resistance. In H₂-containing gases where the electronic transport in $ {\left( {{\hbox{L}}{{\hbox{a}}_{0.{75} - x}}{\hbox{S}}{{\hbox{r}}_{0.{25} + x}}} \right)_{0.{95}}}{\hbox{M}}{{\hbox{n}}_{0.{5}}}{\hbox{C}}{{\hbox{r}}_{0.{5} - x}}{\hbox{T}}{{\hbox{i}}_x}{{\hbox{O}}_{{3} - }}_\delta $ perovskites becomes low, co-doping deteriorates the anode performance, which can be however improved by infiltrating Ni and $ {\hbox{Ce}}{{\hbox{O}}_{{\rm{2}} - }}_\delta $ v into the porous oxide electrode matrix.     

Electrical conductivity and defect chemistry of {\hbox{B}}{{\hbox{a}}_x}{\hbox{S}}{{\hbox{r}}_{{1} - x}}{\hbox{C}}{{\hbox{o}}_y}{\hbox{F}}{{\hbox{e}}_{{1} - y}}{{\hbox{O}}_{{3} - \delta }} perovskites

Bulk $ {\hbox{B}}{{\hbox{a}}_x}{\hbox{S}}{{\hbox{r}}_{{1} - x}}{\hbox{C}}{{\hbox{o}}_y}{\hbox{F}}{{\hbox{e}}_{{1} - y}}{{\hbox{O}}_{{3} - \delta }} $ compositions (BSCF) were synthesized by the solid-state reaction method. The electrical conductivity of ceramic bars was measured using a dc four-probe method as a function of temperature in air up to 970?°C. All compositions showed thermally activated p-type semi-conductivity up to ~450?°C and then a transition to metal-like conductivity. The small-polaron hopping p-type semi-conductivity depends on the oxygen nonstoichiometry, which increases with increasing temperature. Metal-like conductivity is attributed to the overlap of the transition metal d-electron orbitals with the oxygen p-orbitals. Strontium-rich compositions show higher conductivity. The Co/Fe ratio does not influence much the p-type semi-conduction. Iron-rich compositions revealed more metal-like conduction behavior. The degree of overlap between transition metal d-orbitals and oxygen p-orbitals depends on the Ba/Sr as well as on the Co/Fe ratios.     

Reactions of Unsaturated Quinoline Triosmium Clusters [Os3(CO)9(μ3-η2-C9H5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os3(CO)8(μ-η2-C9H5(4-Me)N)(η2-SC(NMe2NCH2Me)(μ-H)2] and [Os3(CO)9(μ-η2-C9H6N)(η1-SC(NMe2)2)(μ-H)]

Treatment of the electronically unsaturated 4-methylquinoline triosmium cluster $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]$ (1) with tetramethylthiourea in refluxing cyclohexane at 81°C gave $[\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]$ (2) and $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]$ (3). In contrast, a similar reaction of the corresponding quinoline compound $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]$ (4) with tetramethylthiourea afforded $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]$ (5) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and a quinolyl ligand coordinated to the Os₃ triangle via the nitrogen lone pair and the C(8) atom of the carbocyclic ring. In 3 and 5, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom, which is also bound to the carbon atom of the quinolyl ligand. Compounds 3 and 5 react with PPh₃ at room temperature to give the previously reported phosphine substituted products $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]$ (6) and $[\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]$ (7) by the displacement of the tetramethylthiourea ligand.     

On the role of lattice dynamics on low-temperature oxygen mobility in solid oxides: a neutron diffraction and first-principles investigation of {\hbox{L}}{{\hbox{a}}_2}{\hbox{Cu}}{{\hbox{O}}_{{4 + \delta }}}

The structure of oxygen-intercalated La₂CuO_4.07 has been investigated at 20 and 300?K by neutron diffraction on an electrochemically oxidized single crystal. At 20?K, reconstruction of the nuclear density by maximum entropy method shows strong displacements of the apical oxygen atoms towards [100] with respect to the F-centred unit cell, whilst displacements towards [110] and [100] were both found to be present at ambient temperature. Combining structural studies with first-principles lattice dynamical calculations, we interpret the displacements of the apical oxygen atoms to be at least partially of dynamic origin already at ambient temperature. Strong displacements of the apical oxygen atoms of stoichiometric and oxygen-doped $ {\hbox{L}}{{\hbox{a}}_{{2}}}{\hbox{Cu}}{{\hbox{O}}_{{{4} + \delta }}} $ and corresponding associated lattice instabilities, i.e. low-energy phonon modes, are considered as a general prerequisite of low-temperature oxygen diffusion mechanisms. Lattice dynamical calculations on $ {\hbox{L}}{{\hbox{a}}_{{2}}}{\hbox{Cu}}{{\hbox{O}}_{{{4} + \delta }}} $ suggest that the oxygen species diffusing at low temperature are not the interstitial but, more prominently, the apical oxygen atoms. The presence of interstitial oxygen atoms is, however, important to amplify via specific, low-energy phonon modes, a dynamic exchange mechanism between apical and vacant interstitial oxygen sites, thus allowing a dynamically triggered, shallow potential oxygen diffusion pathway. The crucial role of lattice dynamics to enable low-temperature oxygen mobility in K₂NiF₄-type oxides is discussed on a microscopic scale and compared to similar low-temperature oxygen diffusion mechanisms, recently proposed for non-stoichiometric oxides with Brownmillerite-type structure.     

Acid–Base Properties of the \mathrm{Fe}(\mathrm{CN})_{6}^{3-}/\mathrm{Fe}(\mathrm{CN})_{6}^{4-} Redox Couple in the Presence of Various Background Mineral Acids and Salts

The acid?Cbase behavior of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ was investigated by measuring the formal potentials of the $\mathrm{Fe}(\mathrm{CN})_{6}^{3-}$ / $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ couple over a wide range of acidic and neutral solution compositions. The experimental data were fitted to a model taking into account the protonated forms of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ and using values of the activities of species in solution, calculated with a simple solution model and a series of binary data available in the literature. The fitting needed to take account of the protonated species $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ and $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ , already described in the literature, but also the species $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ (associated with the acid?Cbase equilibrium $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}\rightleftharpoons \mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-} + \mathrm{H}^{+}$ ). The acidic dissociation constants of $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ , $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ and $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ were found to be $\mathrm{p}K^{\mathrm{II}}_{1}= 3.9\pm0.1$ , $\mathrm{p}K^{\mathrm{II}}_{2} = 2.0\pm0.1$ , and $\mathrm{p}K^{\mathrm{II}}_{3} = 0.0\pm0.1$ , respectively. These constants were determined by taking into account that the activities of the species are independent of the ionic strength.     

Density functional theoretical study of A series of pentazolide compounds \hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q} (A = B, Al, Si, P, and S; n = 1–3; q = +1, 0, −1, −2, and −3)

The structure and the stability of pentazolide compounds $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ (A = B, Al, Si, P, and S; n= 1–3; q = +1, 0, ?1, ?2, and ?3), as high energy-density materials (HEDMs), have been investigated at the B3LYP/6-311+G* level of theory. The natural bond orbital analysis shows that the charge transfer plays an important role when the $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ species are decomposed to $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 5-{\it n}}\hbox{N}_3^{\it q}$ and N₂. The more negative charges are transferred from the N₂ molecule after breaking the N₅ ring, the more stable the systems are with respect to the decomposition. Moreover, the conclusion can be drawn that ${\hbox{Al}(\hbox{N}_5)_5^{2-}}$ and ${\hbox{Al}_2(\hbox{N}_5)_4^{2-}}$ are predicted to be suitable as potential HEDMs.     

Free ions Pr IV (4\text{ f }^{2}) and Tm IV (4\text{ f }^{12}): intermediate versus LS coupling scheme

The intermediate and LS-coupling schemes for the free lanthanide ions $\text{ Pr }^{3+}$ Pr 3 + and $\text{ Tm }^{3+}$ Tm 3 + have been compared by the matrix elements of the tensor operator ${{\varvec{U}}}^{({\varvec{k}})}, \text{ k } = 2, 4, 6$ U ( k ) , k = 2 , 4 , 6 . The necessary eigenvectors and eigenvalues have been computed with the aid of four parameters, $\text{ F }_{2}, \text{ F }_{4}, \text{ F }_{6}$ F 2 , F 4 , F 6 , and $\zeta _{4\mathrm{f}}$ ζ 4 f , known from free-ion spectra of the same ions. It has been found that both coupling types for each ion lead to close values of ${\vert }{{\varvec{U}}}^{({\varvec{k}})}{\vert }^{2}$ | U ( k ) | 2 only for transitions from the ground level to certain lower-lying energy levels within the $4\text{ f }^\mathrm{N}$ 4 f N configuration.     

Theoretical and computational modelling of functionalization energy for the {\rm{C}}_{{6{n}}^{2}} {\rm{H}}_{6{n}} polycyclic aromatic hydrocarbons (PAHs) homologue series

Based on the free electron metallic disc model, the derivation of a simple expression for evaluation of the Fukui function for the molecular models of polycyclic aromatic hydrocarbons (PAHs) of the general formula $ {\rm{C}}_{{6{n}}^{2}} {\rm{H}}_{6{n}} $ was described. We also investigated the functionalization energy with OH radicals for the molecular models of PAHs (n = 1–6). Our metallic disc model-based functionalization reaction energy was in agreement with the DFT:B3LYP/6-31G(d) calculated values. Asymptotic values of the functionalization energies ( $ {{n}} \to \infty $ ) were predicted to be ?30.1 ± 0.1 and ?8.7 ± 0.1 kcal/mol for the external and internal border carbon atoms, respectively.     

On the anomaly of the quasiclassical product distributions of the \hbox{OH} +\hbox{CO} \rightarrow\hbox{H} +\hbox{CO}_2 reaction

A grid empowered molecular simulator (GEMS) embodying in a single workflow the ab initio treatment of elementary chemical processes has been extended to four atom reactions. GEMS has been used to carry out a massive quasiclassical investigation for the $\hbox{OH} +\hbox{CO} \rightarrow\hbox{H} +\hbox{CO}_2$ reaction on the most recently proposed potential energy surface. The type of potential energy surface used and the possibility of running the simulations on the grid have allowed us to keep the error of the order of a few percent at all values of the collision energy and to estimate accurately the dependence of the reaction cross section on the collision energy. The accuracy of the calculations has allowed to unequivocally single out the fact that the calculated center-of-mass angular distribution is clearly isotropic and radically differs from the asymmetric forward?Cbackward structure obtained from the experiment. However, when the laboratory frame analogues are compared, the difference almost vanishes.     

Direct Ab Initio Dynamics Study for the Hydrogen Abstraction Reaction: CH _{2} ({^{3}}B_{1}) + H2CO \rightarrow CH3 + CHO

We present a direct ab initio dynamics study of thermal rate constants of the hydrogen abstraction reaction of CH $_{2}(^{3}B_{1})$ + H₂CO $\rightarrow $ CH₃ + CHO. The MP2/cc-pVDZ method is employed to optimize the geometries of stationary points as well as the points on the minimum energy path. The energies of all the points were further refined at the CCSD(T)/cc-pVTZ level of theory based on the Moller– Plesset perturbation theory (MP2) optimized geometries. The rate constants were evaluated using the conventional transition state theory, the canonical variational TST, and the improved canonical variational TST, also both including small-curvature tunneling correction in the temperature range of 300–2,500 K. The calculated results show that the rate constants have positive temperature dependence in the calculated temperature range. The calculated results show that the tunneling effect is important at low temperature region.     

Quasi-classical trajectory insight into stereodynamics for reaction $$\hbox {He}+\hbox {D}_{2}^{+}\rightarrow \hbox {HeD}^{+}+\hbox {D}$$ with the improved potential energy surface

In this work, a theoretical study on the detailed vector correlation for the reaction \(\hbox {He}+\hbox {D}_{2}^{+}\rightarrow \hbox {HeD}^{+}+\hbox {D}~(\hbox {v}, \hbox {j})\) has been carried out at the collision energy of 23.06 kcal/mol with different rotational states of j \(=\) 0–5 and vibrational states v \(=\) 1–5 by use of the quasi-classical trajectory calculation on an improved potential energy surface. The features of \({{\varvec{P}}}\mathbf{(}{\varvec{\theta }}_{{\varvec{r}}}{} \mathbf{)}\) distributions describing k and \(\mathbf{j}^\prime \) correlations were discussed. In addition, in order to get full knowledge of stereodynamics of the system, the distributions of dihedral angle \({{\varvec{P}}}\mathbf{(}{\varvec{\varphi }}_{{\varvec{r}}}{} \mathbf{)}\) and the polarization-dependent differential cross-sections (PDDCSs) were also reported. It has been demonstrated that both product alignment and polarization are sensitive to the reagent vibrational and rotational number. Furthermore, the dynamics behavior of the reaction is independently changed with respect to j under a certain v except for the product alignment effect \(({\varvec{P}}({\varvec{\theta }}_{{\varvec{r}}}))\), while it exhibits a generally regular trend concerning v when j is invariable.     

Counter-Ion Association Effect in Dilute Giant Polyoxometalate [AsIII 12CeIII 16(H2O)36W148O524]76−({W148}) and [Mo132O372(CH3COO)30 (H2O)72]42− ({Mo132}) Macroanionic Solutions

This article reports the use of simple conductivity measurements to explore the state of small counter-ions (mostly NH ₄ ⁺ and Na⁺) in $[\hbox{As}^{\rm III}_{12}\hbox{Ce}^{\rm III}_{16}(\hbox{H}_2\hbox{O})_{36}\hbox{W}_{148}\hbox{O}_{524}]^{76-} (\{\hbox{W}_{148}\})$ and $[\hbox{Mo}_{132}\hbox{O}_{372}(\hbox{CH}_{3}\hbox{COO})_{30} (\hbox{H}_{2}\hbox{O})_{72}]^{42-} (\{\hbox{Mo}_{132}\})$ macroanionic solutions. All the solutions are dialyzed to remove the extra electrolytes. Conductivity measurements on {(NH₄)₇₀Na₆W₁₄₈} and {(NH₄)₄₂Mo₁₃₂} solutions at different concentrations both before and after dialysis indicate that the state of counter-ions has obvious concentration dependence. The “counter-ion association” phenomenon, that is, some small counter-ions closely associate with macroanions and move together, has been observed in both types of macroionic solutions above certain concentration. The association of counter-ions in hydrophilic macroionic solutions provides support on our previous speculation that the counter-ions might be responsible for the unique self-assembly of such macroanions into single-layer blackberry-type structures.     

Electrogenerated chemiluminescence sensor for glutathione with Ru\left( {bpy} \right)_3^{2+ } -doped silica nanoparticles

An electrogenerated chemiluminescence (ECL) sensor for reduced glutathione was developed based on $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ -doped silica nanoparticles-modified gold electrode (Ru-DSNPs/Au). These uniform Ru-DSNPs (about 58?+?4 nm) were prepared by a water-in-oil microemulsion method and characterized by transmission electron microscope and scanning electron microscope. With such a unique immobilization method, a considerable $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ was immobilized three dimensionally on the electrode, which could greatly enhance the ECL response and thus result in an increased sensitivity. The ECL analytical performances of this sensor for reduced glutathione based on the quenched ECL emission of $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ have been investigated in detail. Under the optimum condition, the ECL intensity was linear with the reduced glutathione concentration in the range of 1.0?×?10^?9 to 1.0?×?10^?4?mol?L^?1 (R?=?0.9971). This method has been successfully applied for the determination of reduced glutathione in serum samples with satisfactory results. The as-prepared ECL sensor for the determination of reduced glutathione displayed good sensitivity and stability.     

Synthesis and reactivity of(\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_9 : An unusually reactive triosmium cluster

The synthesis of $(\mu - H)(\mu - \eta ^2 - H_2 )_4 )Os_3 (CO)_{10} $ (4) from piperidine and Os₃(CO)₁₀(CH₃CN)₂ and its solid state structure are reported. The room temperature reactions of the decarbonylation product of4, $(\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_9 $ (3), with P(C₆H₅)₃, CNCH₃, HCl and H₂ are reported. Overall, the products obtained closely resemble those obtained from the analogous, $(\mu - H)(\mu _3 - \eta ^2 - H_2 )_3 )Os_3 (CO)_9 $ (1). The isomerizations of the phosphine addition products $(\mu - H)(\mu - \eta ^2 - H_2 )_n )Os_3 (CO)_9 P(C_6 H_5 )_3 $ (n = 3,6a;n = 4,5a) have been studied by¹H-NMR techniques and the initial rearrangement was shown to be an intramolecular process. Slower conversion to the complex $(\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_8 P(C_6 H_5 )_3 $ (8) was observed and the solid state structure of this product is reported and compared with a related compound containing an ethyl,n-propylμ ₃-imidoyl ligand. Compound4 crystallizes in the triclinic space group Pl (#2) withZ= 2, and unit cell parametersa = 9.294(3) Å,b = 15.758(5) Å,c = 7.406(2) Å,a = 81.10(2)°,β=76.47(2)°,y =74.88(2)°, andV =1013(l) ų. Least-squares refinement of 2677 reflections gave a final discrepancy factor ofR = 0.054 (R _w = 0.066). Compound8 crystallizes in the space group C2/c with unit cell parametersa = 24.818(3) Å,b = 16.389(3) Å,c = 18.111(3) Å,β= 120.94(2)°,V = 6318(4) ų, andZ = 8. Least squares refinement of 3439 reflections gave a final discrepancy factor ofR = 0.039 (R _w =0.047).     

A thermodynamic study of complexation of 18-crown-6 with Zn2+, Tl+, Hg2+ and {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} cations in acetonitrile-dimethylformamide binary media and study the effect of anion on the stability constant of (18C6-Na+) complex in methanol solutions

The equilibrium constants and thermodynamic parameters for complex formation of 18-crown-6(18C6) with Zn²⁺, Tl⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations have been determined by conductivity measurements in acetonitrile(AN)-dimethylformamide(DMF) binary solutions. 18-crown-6 forms 1:1 complexes [M:L] with Zn²⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations, but in the case of Tl⁺ cation, a 1:2 [M:L₂] complex is formed in most binary solutions. The thermodynamic parameters ( $ \Delta {\text{H}}^{ \circ }_{{\text{c}}} $ and $ \Delta {\text{S}}^{ \circ }_{{\text{c}}} $ ) which were obtained from temperature dependence of the equilibrium constants show that in most cases, the complexes are enthalpy destabilized but entropy stabilized and a non-monotonic behaviour is observed for variations of standard enthalpy and entropy changes versus the composition of AN/DMF binary mixed solvents. The obtained results show that the order of selectivity of 18C6 ligand for these cations changes with the composition of the mixed solvent. A non-linear relationship was observed between the stability constants (logK_f) of these complexes with the composition of AN/DMF binary solutions. The influence of the $ {\text{ClO}}^{ - }_{{\text{4}}} $ , $ {\text{NO}}^{ - }_{{\text{3}}} $ and $ {\text{Cl}}^{ - } $ anions on the stability constant of (18C6-Na⁺) complex in methanol (MeOH) solutions was also studied by potentiometry method. The results show that the stability of (18C6-Na⁺) complex in the presence of the anions increases in order: $ {\text{ClO}}^{ - }_{{\text{4}}} $  >  $ {\text{NO}}^{ - }_{{\text{3}}} $  >  $ {\text{Cl}}^{ - } $ .     

Synthesis and electrochemical properties of {\text{C}}{{\text{a}}_{{0.9}}}{\text{L}}{{\text{a}}_{{0.1}}}{\text{W}}{{\text{O}}_{{4 + \delta }}} electrolyte for solid oxide fuel cells

$ {\text{C}}{{\text{a}}_{{0.9}}}{\text{L}}{{\text{a}}_{{0.1}}}{\text{W}}{{\text{O}}_{{4 + \delta }}} $ powder was prepared by gel auto-ignition process. According to X-ray diffraction analysis, the resulted $ {\text{C}}{{\text{a}}_{{0.9}}}{\text{L}}{{\text{a}}_{{0.1}}}{\text{W}}{{\text{O}}_{{4 + \delta }}} $ solid solution has tetragonal scheelite structure. Results of electrochemical testing reveal that the performances of La-doped calcium tungstate are superior to that of pure CaWO₄, a conductivity of 5.28?×?10^?3?S?cm^?1 at 800?^??C could be obtained in the $ {\text{C}}{{\text{a}}_{{0.9}}}{\text{L}}{{\text{a}}_{{0.1}}}{\text{W}}{{\text{O}}_{{4 + \delta }}} $ compound sintered at 1,200?^??C. The electrical conductivity as a function of oxygen partial pressure and also the electromotive force of oxygen concentration cell are measured to prove the mainly ionic conductivity of the investigated material.     

The Formation and Stability of the [FePy3Cl3]· Py Clathrate in the Pyridine–Iron(III) Chloride System: Phase Diagram and Solid–Gas Equilibria Study

The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy₃Cl₃]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy₃Cl₃]·Py_(solid)=[FePy₂Cl₃]_(solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy₃Cl₃]·Py_(solid)=[FePy2Cl₃]_(solid) + 2 Py_(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process ${1 \over 2}[\hbox{FePy}_{3}\hbox{Cl}_{3}]\cdot \hbox{Py}_{\rm (solid)} = {1 \over 2}[\hbox{FePy}_{2}\hbox{Cl}_{3}]_{\rm (solid)} + \hbox{Py}_{\rm (gas)}$ in the range 292–327 K, ΔH $^{0}_{298}$ =70.8 ± 0.8 kJ/mol, ΔS $^{0}_{298}$ =197 ± 3 J/(mol K), ΔG $^{0}_{298}$ =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH $^{0}_{298}$ =44.4 ± 1.3 kJ/mol, ΔS $^{0}_{298}$ =116 ± 4 J/(mol K), ΔG $^{0}_{298}$ =9.9 ± 0.3 kJ/mol.     

Positive ions of SiH4: Jahn-Teller-like distortions for {{\rm SiH}_{4}^{+}} and eventually molecular collapse on further ionisation.

We have recently studied by quantum-chemical calculations some fifteen tetrahedral and octahedral molecules. These seemingly disparate numerical tabulations were, it was demonstrated, pulled together by comparison with model semiclassical scaling laws for (i) nuclear–nuclear repulsion energy at the equilibrium geometry and (ii) total energies likewise. Here, we again appeal to such model scaling predictions, but now for positive ions of SiH₄. We then report Hartree-Fock equilibrium geometries and MP2 corrections. For ${{\rm SiH}_{4}^{+}}$ , we assumed the symmetry to be C_2v , by analogy with ${{\rm CH}_{4}^{+}}$ for which experimental confirmation of this symmetry is available. Larger distortions, but still for C_2v symmetry, are found from our quantum-chemical studies in the case of ${{\rm SiH}_{4}^{2+}}$ . But for ${{\rm SiH}_{4}^{3+}}$ there is a marked tendency to return to a configuration quite close to tetrahedral symmetry. But non-convergence is found for ${{\rm SiH}_{4}^{4+}}$ . Finally relations to the admittedly simplistic semiclassical geometry scaling predictions of Lawes and March are conjectured.