Computer Simulation of the Absorption of CO<Subscript>2</Subscript> Molecules by Water Cluster: 1. The Stability

The (CO₂)_i(H₂O)₁₀ clusters with the kinetic energy corresponding to a temperature of 233 K is simulated by the molecular dynamics method. The stability of these clusters with respect to thermal, mechanical, and dielectric perturbations, as well as to the absorption of CO₂ molecules, is studied. It is shown that the cluster composed of 10 water molecules remains thermodynamically stable if it captures one or two CO₂ molecules. Clusters are absolutely unstable when 3 ≤ i ≤ 9. A metastable state of clusters is achieved at i > 9.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 308–314.Original Russian Text Copyright © 2005 by Galashev, Rakhmanova, Chukanov.     

Computer Simulation of the Absorption of CO<Subscript>2</Subscript> Molecules by Water Cluster: 2. The Microstructure

The simulation of the absorption of CO₂ molecules by the (H₂O)₁₀ cluster is performed by the molecular dynamics method using the modified TIP4P model of water. The detailed structure of (CO₂)_i(H₂O)₁₀ clusters (0≤i≤11) is analyzed by the statistic geometry method based on the construction of the Voronoi polyhedra. The obtained distributions of the geometric elements of polyhedra indicate the significant changes in the structure of a cluster after the absorption of one CO₂ molecule. Only polyhedra characterizing the structure of unstable water clusters that absorbed six or seven CO₂ molecules demonstrate a nonsphericity close to the ideal tetrahedron. Linear CO₂ molecule tends to be oriented in a cluster so that the average angle formed by this molecule and permanent dipole moments of water molecules would be equal to about 30°.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 315–321.Original Russian Text Copyright © 2005 by Galashev, Rakhmanova, Chukanov.     

Simulation of dielectric properties and stability of clusters (H2O)i, CO2(H2O)i, and CH4(H2O)i

Molecular dynamics method is used for studying complex permittivity ɛ and the stability of individual water clusters as a function of the number of involved molecules (7 ≤ i ≤ 20) and also the corresponding characteristics of water aggregates with a captured CO₂ or CH₄ molecule. Absorption of the latter molecules leads to considerable changes in dielectric properties and stability of clusters. In particular, upon the addition of a CO₂ molecule to a water cluster, the oscillation parameters of the real and imaginary parts of the permittivity change. Capture of a CH₄ molecule by a water aggregate changes the ɛ(ω) dependence from the relaxation to resonance type. For i ≥ 15, the thermal stability of individual water clusters can be lower than that of aggregates CO₂(H₂O) _i and CH₄(H₂O) _i . The mechanical stability of (H₂O) _{i ≥ 13} clusters can exceed that of heteroclusters under consideration. Clusters (H₂O) _i and CO₂(H₂O) _i have approximately the same dielectric stability, whereas aggregates CH₄(H₂O) _i exhibit lower stability with respect to electric perturbations. Original Russian Text ? A.E. Galashev, V.N. Chukanov, A.N. Novruzov, O.A. Novruzova, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 143–153.     

Electrochemical Synthesis of Co-intercalation Compounds in the Graphite-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript>System

Anodic oxidation of highly oriented pyrolytic graphite in an electrolyte containing concentrated sulfuric and anhydrous phosphoric acids is studied for the first time. The synthesis was carried out under galvanostatic conditions at a current I = 0.5 mA and an elevated temperature (t = 80°C). Intercalation compounds of graphite (ICG) are shown to form at all concentration ratios of H₂SO₄ and H³PO⁴ acids. The intercalation compound of step I forms in solutions containing more than 80 wt % H₂SO₄, a mixture of compounds of intercalation steps I and II forms in 60% H²SO⁴, intercalation step II is realized in the sulfuric acid concentration range from 10 to 40%, and a mixture of compounds of intercalation steps III and II is formed in 5% H₂SO₄ solutions. The threshold concentration of H₂SO₄ intercalation is ∼2%. With the decrease in active intercalate (H₂SO₄) concentration, the charging curves are gradually smoothed, the intercalation step number increases, and the potentials of ICG formation also increase. As the sulfuric acid concentration in the electrolyte changes from 96 to 40 wt %, the filled-layer thickness d _i in ICG monotonously increases from 0.803 to 0.820 nm, which apparently is associated with the greater size of phosphoric acid molecules. With further increase in H₃PO₄ concentration in solution, d _i remains unchanged. According to the results of chemical analysis, both acids are simultaneously incorporated into the graphite interplanar spacing and their ratio in ICG is determined by the electrolyte composition.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 651–655.Original Russian Text Copyright © 2005 by Leshin, Sorokina, Avdeev.     

Spectral effects of the clusterization of greenhouse gases: Computer experiment

Autocorrelation functions of the total dipole moment of clusters composed of H₂O and N₂O molecules are calculated in terms of the molecular dynamics method. The IR absorption and reflection spectra of systems composed of (H₂O)_i, N₂O(H₂O)_i, and (N₂O)₂(H₂O)_i clusters (2 ≤ i ≤ 20) are obtained on the basis of these functions. Frequency-dependent dielectric permittivity of clusters increases after the absorption of N₂O molecules. The absorption coefficient of cluster systems with trapped N₂O molecules increases at low frequencies and decays at frequencies ω > 500 cm^?1. The inclusion of N₂O molecules increases also reflection coefficient R and changes the pattern of R(ω) spectra. The absorption of IR radiation increases with the number of H₂O molecules in clusters. Dielectric losses also increase with an increase in i number upon the absorption of N₂O molecules. The number of electrons interacting with an incident electromagnetic wave increases upon the capture of N₂O molecules.     

An <Emphasis Type="Italic">ab initio </Emphasis> Quantum-Chemical Study of C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CH<Subscript>3</Subscript> and C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CF<Subscript>3</Subscript>

The potential functions of internal rotation around the C -S bond in the C₆H₅S(O)CH₃ and C₆H₅S(O)CF₃ molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C -S-C bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C -S bond, corrected for the zero-point vibration energy, are 21.29 [C₆H₅S(O)CH₃] and 28.98 [C₆H₅S(O)CF₃] kJ mol⁻¹. The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C SO), 106.3 (C SO) in C₆H₅S(O)CH₃; 93.5 (CSC), 108.2 (C SO), 105.2 (C SO) in C₆H₅S(O)CF₃. The bond lengths are as follows (Å): 1.520 (S=O), 1.804 (C -S), 1.810 (C -S) in C₆H₅S(O)CH₃; 1.507 (S=O), 1.799 (C -S), 1.870 (C -S) in C₆H₅S(O)CF₃. According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent σ bond (S→O) and an almost ionic bond. An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)→σ*(C -S) and n(O)→σ*(C -S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 96–104.Original Russian Text Copyright © 2005 by Bzhezovskii, Il’chenko, Chura, Gorb, Yagupol’skii.     

Phase Transitions,Thermal Desorption of Gases,and Electroconduction in BaCeO<Subscript>3</Subscript>, a Base for High-Temperature Protonic Conductors

Investigations of phase transitions in barium cerate are carried out by methods of dilatometry and differential scanning calorimetry. Thermal desorption of gases and temperature dependences of electroconduction in dry and humid air are studied. Barium cerate exhibits complex polymorphism, undergoing a number of structural conversions at 300– 1300 K. The peaks in the spectra of thermal desorption of CO₂ and H₂O correlate with variations in the crystal lattice. Structural changes in BaCeO₃ affect activation energies for the carrier transport and the shares of partial conductivities.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 620–626.Original Russian Text Copyright © 2005 by Kuz’min, Gorelov, Vaganov, Korzun, Kazantsev, Aksenova, Khromushin.     

Synthesis,crystal and molecular structure and magnetic properties of an extended two-dimensional fumarato-bridged polymeric cobalt(II) complex [Co(μ-fumarato)(γ-methylpyridine)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]<Subscript>∞</Subscript>

An extended hydrogen-bonded two-dimensional fumarato-bridged complex [Co(μ-fumarato)(γ-methylpyridine)₂(H₂O)₂]_∞ has been synthesized and its crystal structure determined by single crystal X-ray analysis. The X-ray analysis reveals that the cobalt atom is positioned in distorted octahedral surroundings. An extended twodimensional structure was formed through interchain hydrogen bonding. Magnetic measurements showed the presence of weak antiferromagnetic exchange interactions between the cobalt(II) ions within the chain, based on the spin Hamilitonian H = −2J ∑ S_i S_{i+ 1} (J = − 0.22 cm⁻¹).     

The influence of the molar ratio [H<Subscript>2</Subscript>O]/[Ti(OR)<Subscript>4</Subscript>] on the kinetics of the titanium-oxo-alkoxy clusters nucleation

The influence of the molar ratio h = [H₂O]/[Ti(OR)₄] (R = Pr ⁱ ) on the kinetics of the titanium-oxo-alkoxy clusters (TOAC) nucleation was studied. Clusters were formed by the titanium tetraisopropoxide Ti(OPr ⁱ )₄ chemical reaction with H₂O in n-propanol solution, with the fixed concentration of Ti(OPr ⁱ )₄ (c = 0.04 M), molar ratio h ∈ {11, 14, 17, 20} and temperature T ∈ {298, 308, 318} K. It was determined that the isothermal rate of clusters nucleation is a power law function of the molar ratio h. The kinetic parameter β value changes complexly as h and T change. The value of apparent activation energy of the nucleation process (E _a) decreases with the increase of value h. It was found that nucleation is a reaction with complex kinetics whose elementary stages are hydrolysis Ti(OR)₄ to Ti(OR)₃OH and formation of titanium-oxo-alkoxy clusters [Ti _{n + β}O_β](OR)_{4n + 2β} through the alcoxolation reaction.     

Effect of oxygen activity and water partial pressure to degradation rate of Ni cermet electrode contacting Zr<Subscript>0.84</Subscript>Y<Subscript>0.16</Subscript>O<Subscript>1.92</Subscript> electrolyte

The time curves of full polarization resistance of Ni cermet electrode modified with CeO_{2 − δ} additive were studied by means of impedance spectroscopy in binary gas mixtures x% H₂ + (100 − x)% H₂O, 10% CO + 90% CO₂ and multicomponent gas mixtures H₂ + CO₂ + H₂O + CO + Ar of various composition at the temperature of 900°C. The Ni cermet electrode degradation rate in binary gas mixtures H₂ + H₂O was shown to increase sharply at the partial water pressure over 45%. The Ni cermet electrode degradation rate in the mixture of 10% CO + 90% CO₂ was significantly lower than that in 10% H₂ + 90% H₂O. The major changes in the electrode characteristics upon long exposure in working conditions were accounted for by changes in the high-frequency partial polarization resistance. In the course of long testing, the electrode microstructure was not significantly changed. In the presence of hydrogen-containing components (H₂ and H₂O), the carbon-containing components (CO and CO₂) were shown to make an insignificant contribution to the current generation processes in Ni cermet electrode. It was suggested that strong degradation of Ni cermet electrode was caused by poisoning its reaction sites with strongly linked adsorption forms of water (hydroxyls) at the positive charge of electrode.     

Computer-assisted study of characteristics of water clusters in the presence of nitrogen dioxide

The interaction of IR radiation with water clusters that have absorbed NO₂ molecules is studied by the molecular dynamics method in terms of the polarizable model. Induced dipole moments of H₂O and NO₂ molecules diminish during the addition of one to six NO₂ molecules to (H₂O)₅₀ cluster. The integral intensity of IR absorption by a system consisting of (NO₂) _i (H₂O)₅₀ heteroclusters with 1 ≤ i ≤ 6 decreases, whereas the power of heat emission rises as compared with an (H₂O) _n system. The decrease in the IR absorption and the increase in the IR emission by water clusters with the capture of NO₂ molecules are nonmonotonic. The absorption of NO₂ molecules by water clusters causes a noticeable reduction in the intensity of the first peak and the confluence of the fourth and fifth peaks in the Raman spectrum.     

Formation of Composites Based on CsHSO<Subscript>4</Subscript> and Cs<Subscript>5</Subscript>H<Subscript>3</Subscript>(SO<Subscript>4</Subscript>)<Subscript>4</Subscript> and Mechanism of Their Protonic Conduction

Vibrational spectra of finely divided amorphous CsHSO₄,Cs₅H₃(SO₄)₄ · H₂O, and composites based on these are measured and analyzed. An analysis of the spectra indicates the occurrence of substantial changes in the system of hydrogen bonds and in the spectral range of the sulfate group of acid sulfates in the composites. Structural dynamics of the SO₄ tetrahedrons is in full conformance with protonic conduction and the data of x-ray diffraction analyses accompanied by differential scanning calorimetry. It is shown that mobility of protons in the composites increases. A mechanism of the formation of the composites and their conduction is proposed.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 640–645.Original Russian Text Copyright © 2005 by Ponomareva, Lavrova, Burgina.     

Dielectric properties of water clusters containing CO and NO molecules. Computational experiment

The absorption of CO and NO molecules by (H₂O)₂₀ clusters was studied by the method of molecular dynamics. In general, the clusters containing CO molecules are more stable mechanically, while the clusters with NO molecules are more stable against heating. The mobility of NO molecules in such clusters is higher than that of CO molecules. The total dipole moment, the static dielectric permeability, the number of active electrons in the clusters, and the specific number of hydrogen bonds between water molecules possess peak values when the number of doping molecules i = 6. IR absorption spectra mostly acquire a smooth shape at i > 6. Capture of CO and NO molecules by water cluster operates as anti-greenhouse effect.     

Gas phase structure of micro-hydrated [Mn(ClO<Subscript>4</Subscript>)]<Superscript>+</Superscript> and [Mn<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>3</Subscript>]<Superscript>+</Superscript> ions probed by infrared spectroscopy

Gas-phase infrared photodissociation spectroscopy is reported for the microsolvated [Mn(ClO₄)(H₂O) _n ]⁺ and [Mn₂(ClO₄)₃(H₂O) _n ]⁺ complexes from n = 2 to 5. Electrosprayed ions are isolated in an ion-trap where they are photodissociated. The 2600–3800 cm⁻¹ spectral region associated with the OH stretching mode is scanned with a relatively low-power infrared table-top laser, which is used in combination with a CO₂ laser to enhance the photofragmentation yield of these strongly bound ions. Hydrogen bonding is evidenced by a relatively broad band red-shifted from the free OH region. Band assignment based on quantum chemical calculations suggest that there is formation of water—perchlorate hydrogen bond within the first coordination shell of high-spin Mn(II). Although the observed spectral features are also compatible with the formation of structures with double-acceptor water in the second shell, these structures are found relatively high in energy compared with structures with all water directly bound to manganese. Using the highly intense IR beam of the free electron laser CLIO in the 800–1700 cm⁻¹, we were also able to characterize the coordination mode (η²) of perchlorate for two clusters. The comparison of experimental and calculated spectra suggests that the perchlorate Cl—O stretches are unexpectedly underestimated at the B3LYP level, while they are correctly described at the MP2 level allowing for spectral assignment.     

New uranyl complex with imidazolidine-2-one [UO<Subscript>2</Subscript>(Imon)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>: Structure and some properties

A complex of uranyl perchlorate with imidazolidine-2-one as the molecular ligand, [UO₂(Imon)₄(H₂O)](ClO₄)₂ (I), was synthesized and structurally characterized by X-ray diffraction analysis. The coordination number of the uranium atom is 7. The nearest environment of the uranyl ion includes four O atoms of the imidazolidine-2-one molecules and one O atom of the water molecule. The perchlorate anions are outer-sphere ligands. The crystals are monoclinic: space group P2₁/c; a = 16.294(3) Å, b = 16.135(3) Å, c = 9.987(2) Å, = 97.69 (3)°, V = 2603.0 (9) ų, (calcd) = 2.117 g/cm³, Z = 4. The IR and luminescence spectra of the complex were recorded.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 919–924.Original Russian Text Copyright © 2004 by Andreev, Antipin, Budantseva, Tuchina, Serezhkina, Fedoseev, Yusov.     

Synthesis of the mixed oxide catalysts based upon the nickel-copper hydrotalcites of the type Ni<Subscript>x</Subscript>Cu<Subscript>6-x</Subscript>Cr<Subscript>2</Subscript>(OH)<Subscript>16</Subscript>(CO<Subscript>3</Subscript>)×4H<Subscript>2</Subscript>O

Summary High resolution TG coupled to a gas evolution mass spectrometer has been used to study the thermal properties of a chromium based series of Ni/Cu hydrotalcites of formulae Ni_xCu_6-xCr₂(OH)₁₆(CO₃)×4H₂O where x varied from 6 to 0. The effect of increased Cu composition results in the increase of the endotherms and mass loss steps to higher temperatures. Evolved gas mass spectrometry shows that water is lost in a number of steps and that the interlayer carbonate anion is lost simultaneously with hydroxyl units. Differential scanning calorimetry was used to determine the heat flow steps for the thermal decomposition of the synthetic hydrotalcites. Hydrotalcites in which M²⁺ consist of Cu, Ni or Co form important precursors for mixed metal-oxide catalysts. The application of these mixed metal oxides is in the wet catalytic oxidation of low concentrations of retractable organics in water. Therefore, the thermal behaviour of synthetic hydrotalcites, Ni_xCu_6-xCr₂(OH)₁₆CO₃×nH₂O was studied by thermal analysis techniques in order to determine the correct temperatures for the synthesis of the mixed metal oxides.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-Sulfinyltrifluoromethanesulfonamide CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>N=S=O with Carbonyl Compounds

N-Sulfinyltrifluoromethanesulfonamide CF₃SO₂N=S=O reacts with salicylaldehyde, 2-furaldehyde, 2-thiophenecarbaldehyde, 3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, and 2-phenyl-2H-1,2,3-triazole-4-carbaldehyde to afford the corresponding N-aryl(hetaryl)methylidenetrifluoromethanesulfonamides in high yields. Reactions of the latter with aniline give no adducts at the C=N bond but transamination products. The reaction of trifluoromethanesulfonamide with phenyl isocyanate led to formation of N,N′-diphenylurea instead of expected N-phenyl-N′-(trifluoromethylsulfonyl)urea.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1006–1010.Original Russian Text Copyright © 2005 by Shainyan, Tolstikova.     

The stability and structure of (N<Subscript>2</Subscript>)<Subscript>j</Subscript>(H<Subscript>2</Subscript>O)<Subscript>i</Subscript> and (Ar)<Subscript>j</Subscript>(H<Subscript>2</Subscript>O)<Subscript>i</Subscript> clusters

The stability and structure of water clusters absorbing nitrogen molecules or argon atoms was analyzed by molecular dynamics simulation at 233 K. The (?μ/?i)_{V, T} derivative of the chemical potential, a value characterizing the stability of a cluster with respect to its size, depends linearly on the number of molecules i. According to this criterion, the clusters under study become stable near i = 40. The average length of H-bonds increases monotonically in the growing cluster of pure water and exhibits oscillatory behavior if the growing cluster contains N₂ molecules or Ar atoms. The number of H-bonds per molecule oscillates between one and six as the cluster size changes. These oscillations are damped in pure water and sustained for clusters containing impurities, especially argon.     

Crystal Structure of Sodium Perchloratotriacetatoneptunate(V) Monohydrate Na<Subscript>3</Subscript>NpO<Subscript>2</Subscript>(OOCCH<Subscript>3</Subscript>)<Subscript>3</Subscript>ClO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

The crystal structure of Na₃NpO₂(OOCCH₃)₃ClO₄ · H₂O was studied by single-crystal X-ray diffraction method. The structure is composed of the complex anions NpO₂(OOCCH₃)₃]²⁻, perchlorate anions, Na cations, and water molecules. The oxygen environment of Np(V) is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of three acetate ions. In addition to the acetate anions, the structure contains the perchlorate ion whose oxygen atoms, except for one, are included in the coordination environment of Na⁺ cations.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 636–640.Original Russian Text Copyright © 2005 by Charushnikova, Fedoseev, Starikova.     

Mechanism of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-catalyzed olefin hydroalumination by alkylalanes

The composition of intermediates of the Cp₂ZrCl₂-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBuⁱ ₂, AlBuⁱ ₃, ClAlBuⁱ ₂) was studied by dynamic ¹H and ¹³C NMR pectroscopy. The reaction of Cp₂ZrCl₂ with isobutylalanes affords the complex (Cp₂ZrHCl·HAlBuⁱ ₂)₂ responsible for α-olefin hydroalumination.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 311–322, February, 2005.