Stability of 3<Emphasis Type="Italic">d</Emphasis>-element cyclotetraphosphates in water

The hydrolysis kinetics of the anion in 3d-element cyclotetraphosphates is considered. The thermodynamic functions of formation (Δ _f H ⁰, Δ _f G ⁰, and Δ _f ? _at ⁰ ) of the cyclotetraphosphates are calculated using the ion increment method. A linear correlation is established between and log K Δ _f ? _at ⁰ for these compounds.     

Solution Thermodynamics of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Superscript>/</Superscript>-Ethylenebis-(salicylideneiminato)-diaquochromium(III) Chloride in Aqueous Dimethylsulphoxide

The densities, viscosities and refractive indices of N,N ^/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H₂O)₂]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w ₂ = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V _φ ), standard partial molar volume (V _φ ⁰ ), the slope (S _V ^* ), standard isobaric partial molar expansibility (φ _E ⁰ ) and its temperature dependence (?φ _E ⁰ /?T) _p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S _n ) and apparent molar refractivity (R _D ^φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.     

Electronic Structure and Relative Stabilities of 10- and 12-Vertex. <Emphasis Type="Italic">Closo</Emphasis>and <Emphasis Type="Italic">Nido</Emphasis>-Heteroborane Clusters of Ga,Ge, and As Elements

A DFT method with the B3LYP functional and the 6-311++G(d,p) diffuse basis set is used to predict geometries, relative stabilities, electronic structures, and the bonding of closo- and nido-Ga_mB_n–mH _n ^2? , Ge_mB_n–mH _n ^m?2 , and As_mB_n–mH _n ^{2 m?2} (n = 10, 12 and m = 1, 2) Clusters are obtained by replacing BH with isolobal GaH, GeH⁺, and AsH²⁺ fragments, keeping the same skeleton electron pairs (SEP). Based on the polyhedral skeletal electron pairs theory (PSEPT), closo and nido structures are predicted and can be of significant interest for experimentalists working in the field of heteroboranes. Different cluster stabilities are studied according to Gimarc′s and Williams′ rules, where our calculations show that the monosubstituted clusters deviate from these rules, giving rise to open structures. As₂B₈H _n ²⁺ as 10-vertex structures lead to nido-type clusters, however, Ge_mB_n–mH _n ^m?2 (n = 10, 12 and m = 1, 2) give rise to closo isomers with close energies. All optimized structures exhibit large HOMO–LUMO gaps suggesting a good kinetic stability, thus predicting their isolation and characterization.     

The dynamics of nonadiabatic transitions in collisions between the I<Subscript>2</Subscript>(<Emphasis Type="Italic">E</Emphasis>) and I<Subscript>2</Subscript>(<Emphasis Type="Italic">X</Emphasis>) molecules

The paper presents the results of a theoretical study of the dynamics of nonadiabatic transitions between the ion-pair states E0 _g ⁺ and D0 _u ⁺ of the I₂ molecule induced by collisions with the I₂ molecule in the ground electronic state X0 _g ⁺ . The potential energy surfaces and diabatic coupling matrix elements of electronic states were obtained using a model based on the diatomics-in-molecule approximation. Special perturbation theory for intermolecular interaction was used to show that the large transition dipole moment between the E0 _g ⁺ and D0 _u ⁺ states caused the appearance of additional long-range corrections, an electrostatic dipole-quadrupole correction to the diabatic coupling matrix elements and induction dipole-dipole correction to the potential energy surface. The influence of these corrections on nonadiabatic dynamics was studied at the level of the semiclassical approximation. The electrostatic correction was found to sharply increase the contribution of resonance (accompanied by minimum kinetic energy changes) vibronic transitions at large distances between the colliding molecules. The induction correction had the opposite effect because of the high transition probability at short distances. The results obtained were in qualitative agreement with experimental data. The conclusion was drawn that obtaining quantitative agreement required a more balanced inclusion of interactions at short and long distances.     

Vapor pressure and heat capacities of perfluoro-<Emphasis Type="Italic">N</Emphasis>-(4-methylcyclohexyl)piperidine

Heat capacities of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) have been measured by low-temperature adiabatic calorimetry. The purity of the compound, its triple-point temperature, and its enthalpy and entropy of fusion have been determined. The saturated vapor pressure was determined by comparative ebulliometry as a function of temperature in the 6.2–101.6 kPa pressure range and 374.2–460.9 K temperature range. The calorimetric enthalpy of vaporization at T = 298.15 K has been measured. The following thermodynamic properties were calculated for PMCP: normal boiling temperature, enthalpy of vaporization Δ_vap H _m ⁰ (T) as a function of temperature, and critical parameters. The enthalpies of vaporization at 298.15 K obtained experimentally and by calculation methods match within their error limits, which validates their adequacy and the adequacy of the Δ_vap H _m ⁰ = f(T) equation as an extrapolation.     

Synthesis and crystal structure of 18-crown-6 <Emphasis Type="Italic">E</Emphasis>-2-phenylethenylphosphonic acid diaqua(18-crown-6)sodium <Emphasis Type="Italic">E</Emphasis>-2-phenylethenylphosphonate

New complex compound, diaqua(18-crown-6)sodium E-2-phenylethenylphosphonate 18-crown-6 E-2-phenylethenylphosphonic acid, [Na(18-crown-6)(H₂O)₂]⁺·HO ₃ ^? PCH=CHPh·18-crown-6·H₂O₃PCH=CHPh, was obtained and its crystal and molecular structures were studied by the X-ray structural analysis. In this structure the complex cation [Na(18-crown-6)(H₂O)₂]⁺ is of guest-host type. The coordination polyhedron of its Na⁺ cation is a slightly screwed hexagonal bipyramid with the base consisting of all 6 O atoms of 18-crown-6 ligand and with two opposite apexes at two O atoms of two ligand water molecules. In the studied crystal structure the alternating complex cations and 18-crown-6 molecules as well as the molecules of acid and its anion HO ₃ ^? PCH=CHPh form by means of hydrogen bonds the infinite chains of two different types.     

Inactivation of <Emphasis Type="Italic">Shewanella putrefaciens</Emphasis> by Plasma Activated Water

Plasma activated water (PAW) generated by atmospheric-pressure air microplasma arrays is a solution containing a variety of reactive species. Here we investigate the effects of different applied voltage and water-activated time on bactericidal activities against Shewanella putrefaciens (S. putrefaciens). Our measurements showed that the sterilization efficiency of S. putrefaciens by PAW could be up to 2.0 Log Reduction. Scanning electron microscopy image and DNA concentration measurement showed that the S. putrefaciens cells were damaged and deformed due to the PAW treatment. The physicochemical properties of PAW treated by different applied voltage and water-activated time were evaluated, including pH value, initial PAW temperature, and the concentrations of plasma-activated species, such as H₂O₂, NO ₃ ^? , NO ₂ ^? , and O₃. Analysis indicates that the sterilization efficiency of S. putrefaciens treated by PAW was mainly determined by H₂O₂ concentration and pH value of PAW. This study provides a basis for the PAW potential applications in the disinfection of rotten food.     

Crystal structure of <Emphasis Type="Italic">ortho</Emphasis>-toluidinium hexafluorosilicate

The structure of the complex (o-CH₃C₆H₄NH₃)₂SiF₆ was determined by X-ray diffraction. In the ionic structure of the complex, the SiF ₆ ^2? anions (Si-F, 1.595(9)-1.683(17)Å) and the o-CH₃C₆H₄NH ₃ ⁺ cations are combined by NH?F hydrogen bonds (N?F 2.757(10)-3.25(2) Å). The components of the structure are combined into a layer whose central part is formed by the SiF ₆ ^2? anions and the outer hydrophobic surfaces are formed by the aromatic rings of the cations.     

<Emphasis Type="Italic">Ab initio</Emphasis> study of scandium fluoride molecules: ScF,ScF<Subscript>2</Subscript>, AND ScF<Subscript>3</Subscript>

Equilibrium geometric parameters, normal mode frequencies and intensities in IR spectra, atomization enthalpy, and relative energies of low-lying electronic states of scandium fluoride molecules (ScF, ScF₂, and ScF₃) are calculated by the coupled-cluster method (CCSD(T)) in triple-, quadruple, and quintuple-zeta basis sets with the subsequent extrapolation of the calculation results to the complete basis set limit. The ScF molecule is also studied by the CCSDT technique. The error in the approximate calculation of triple excitations in the CCSD(T) method does not exceed 0.002 Å for the equilibrium internuclear distance R _e, 4 cm^?1 for the vibrational frequency, and 0.2 kcal/mol for the dissociation energy of the molecule. In the ground electronic state \(\tilde X^2 \) A ₁(C _2ν ) of ScF₂ molecules, R _e(Sc-F) = 1.827 Å and α_e(F-Sc-F) = 124.2°; the energy barrier to bending (linearization) h = E _min(D _g8h ) ? E _min(C_2ν) = 1652 cm^?1. The relative energies of Ã²Δ _g and \(\tilde B^2 \)Π _g electronic states are 3522 cm^?1 and 14633 cm^?1 respectively. The bond distance in the ScF₃ molecule (\(\tilde X^1 \) A′₁, D _3h ) is refined: R _e(Sc-F) = 1.842 Å. The atomization enthalpies Δ_at H ₂₉₈ ⁰ of ScF _k molecules are 139.9 kcal/mol, 289.0 kcal/mol, and 444.8 kcal/mol for k = 1, 2, 3 respectively.     

Structure and dynamics of eight-membered <Emphasis Type="Italic">P,N</Emphasis>-heterocycles in solution

Conformational analysis of eight-membered P,N-heterocycles (P₂^NR₂^R') in the solution has been performed by means of NMR spectroscopy and quantum chemical calculations. The equilibrium of the С₂-symmetrical (crown, major) and С_s-symmetrical (chair-boat, minor) forms of the compounds has been revealed, the transition barriers being of about 12 kcal/mol. The presence of an aromatic substituent at the nitrogen atom significantly shifts the equilibrium towards the dominating form.     

The relation between the potential of zero charge and work function for <Emphasis Type="Italic">sp</Emphasis>-metals

It is shown that for numerous sp-metals there exists no unified work function (W _e) dependence of the potential of zero charge E _{q = 0} and the potential drop characterizing the metal lyophilic behavior Δ _M ^Hg E _chem) _{q = 0}. The reason is that the metal work function is by no means the only factor affecting the value of E _{q = 0}. The quantities E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} depend also on the distance of the solvent dipoles’ closest approach to metal surfaces (d _ms) in the absence of the metal-solvent chemisorption interaction. When the metal-solvent chemisorption interaction is involved, this distance affects the degree of overlapping of the metal’s acceptor levels and the upper occupied donor levels in the solvent molecules. To reliably investigate the effect of any of these factors on E _{q = 0}, the other one should be fixed up. It is shown, by example of Ga-, Bi-Gaand Sn-Ga-electrodes, as well as Pb-Ga-, In-Ga-, and Cd-Ga-electrodes demonstrating very close values of the “electrochemical work function” that the metal-solvent chemisorption interaction becomes stronger with the decreasing of d _ms. The influence of this factor is intensified with the increasing of the solvent’s donor number DN. The W _e dependence of E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} can be traced by example of metals with nearly equal d _ms values, e.g., Tl-Ga, In-Ga, and Ga. In all studied solvents, the deviation of E _{q = 0} from W _e increased in the series Tl-Ga < In-Ga < Ga, that is, with the increasing of the metal’s work function in vacuum. The effect is intensified with the increasing of the solvent’s DN. The obtained results agree with the concept of donor-acceptor nature of the metal-solvent chemisorption interaction.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

Synthesis and physicochemical properties of <Emphasis Type="Italic">N</Emphasis>-decylpyridinium salts with inorganic anions

Ionic liquids with N-decylpyridinium cation and inorganic anions SO ₄ ^2– , NO ₃ ^– , SCN^–, NO ₂ ^– , BF ₄ ^– were synthesized. The structure and composition of the synthesized compounds was proved by elemental analysis and IR spectroscopy. Electroconductivity of aqueous solutions of new ionic liquids was studied, critical concentrations of micelle formation was determined, and thermal stability in air in the temperature range 25–500°С was investigated.     

Quantum-chemical simulation of structure and conformational flexibility of 5,7-di(<Emphasis Type="Italic">tert</Emphasis>-butyl)-2-(8-hydroxyquinolin-2-yl)-1,3-tropolone

Density functional theory [DFT B3LYP/6-311++G(d,p)] simulation has revealed stable tautomers and conformers of polydentate ligand system based on 5,7-di(tert-butyl)-2-(8-hydroxyquinolin-2-yl)-1,3-tropolone with different structures of the coordination nodes, capable of formation of metal chelates. It has been shown that the tautomeric NH- and OH- forms with exo and endo location of the hydroxy group in the quinoline fragments (close in energy, ΔE_ZPE = 0.2–2.4 kcal/mol) are stabilized by intramolecular hydrogen bonds. Energy barriers of the interconversion of these forms via rotation about the C–OH bond of the phenolic fragment are of ΔE_ZPE^≠ = 2.1–4.2 kcal/mol, whereas the barrier of rotation about the bond between the quinoline and tropolone fragments is higher (ΔE_ZPE^≠ = 18.2 and 19.6 kcal/mol).     

Phenomenon of isoparametricity in reactions of <Emphasis Type="Italic">trans</Emphasis>-2,3-diaryloxiranes with arenesulfonic acids. Mechanistic interpretation

Nonadditive effects of substituents X and Y are manifested in reactions of symmetrically X-substituted trans-2,3-diaryloxiranes with Y-substituted arenesulfonic acids. The isoparametric point is reached experimentally: close to the point τ _X ^IP = 4.73 on substituent Х the rate of the oxirane ring opening of trans-2,3-bis(3-bromo-5-nitrophenyl)oxirane (τ_X = 4.38) practically does not depend on substituent Y (ρ _Y ^X = 0.10±0.05). The results of cross correlation analysis of the kinetic data are applied to interpretation of the mechanism of the studied reactions.     

Bis[1,3]thiazolo[4,5-<Emphasis Type="Italic">f</Emphasis>:5',4'-<Emphasis Type="Italic">h</Emphasis>]thieno[3,4-<Emphasis Type="Italic">b</Emphasis>]quinoxaline Derivatives as New Building Blocks of Polymers for Organic Electronics

New derivatives of bis[1,3]thiazolo[4,5-f:5',4'-h]thieno[3,4-b]quinoxaline containing the fused thiadiazoloquinoxaline moiety have been prepared. Monomer M1 shows strong light absorption within 600–800 nm due to intramolecular charge transfer. The optical bandgap E _g ^opt determined from the absorption edge in a film is 1.44 eV. The HOMO and LUMO levels are–5.44 and–3.12 eV, respectively. The new structural fragment has a rather low frontier molecular orbital energies and a small bandgap; therefore, it is a promising building block for the synthesis of polymers for organic electronics.     

Dodecahydro-<Emphasis Type="Italic">closo</Emphasis>-dodecaborate anion intercalation into graphite oxide

It is demonstrated by X-ray diffraction that, in the case of dodecahydro-closo-dodecaborates with small cations (H⁺, Li⁺, Na⁺, K⁺, NH ₄ ⁺ ), the intercalation of the B₁₂H ₁₂ ^2? anion into the interlayer space of graphite oxide is more favorable than the crystallization of a free salt. In the case of large cations commensurable with B₁₂H ₁₂ ^2? (e.g., Cs⁺), no intercalation takes place because these cations and the dodecaborate-closo-dodecaborate anion form stable cubic crystals as a separate phase outside the graphite oxide structure.     

A comparison of energy changes accompanying growth processes by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Calculations are made using the equations Δ_r G = Δ_r H ? TΔ_r S and Δ_r X = Δ_r H ? Δ_r Q where Δ_r X represents the free energy change when the exchange of absorbed thermal energy with the environment is represented by Δ_r Q. The symbol Q has traditionally represented absorbed heat. However, here it is used specifically to represent the enthalpy listed in tabulations of thermodynamic properties as (H _T  ? H ₀) at T = 298.15 K, the reason being that for a given substance TS equals 2.0 Q for solid substances, with the difference being greater for liquids, and especially gases. Since Δ_r H can be measured, and is tangibly the same no matter what thermodynamics are used to describe a reaction equation, a change in the absorbed heat of a biochemical growth process system as represented by either Δ_r Q or TΔ_r S would be expected to result in a different calculated value for the free energy change. Calculations of changes in thermodynamic properties are made which accompany anabolism; the formation of anabolic, organic by-products; catabolism; metabolism; and their respective non-conservative reactions; for the growth of Saccharomyces cerevisiae using four growth process systems. The result is that there is only about a 1% difference in the average quantity of free energy conserved during growth using either Eq. 1 or 2. This is because although values of TΔ_r S and Δ_r Q can be markedly different when compared to one another, these differences are small when compared to the value for Δ_r G or Δ_r X.     

Catalytic Properties of Two <Emphasis Type="Italic">Rhizopus oryzae</Emphasis> 99-880 Glucoamylase Enzymes Without Starch Binding Domains Expressed in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Catalytic properties of two glucoamylases, AmyC and AmyD, without starch binding domains from Rhizopus oryzae strain 99-880 are determined using heterologously expressed enzyme purified to homogeneity. AmyC and AmyD demonstrate pH optima of 5.5 and 6.0, respectively, nearly one unit higher than the Rhizopus AmyA glucoamylase enzyme. Optimal initial activities are at 60 and 50 °C for AmyC and AmyD, respectively. Inactivation of both enzymes occurs at 50 °C following 30 min pre-incubation. The two enzymes demonstrate substantially slower catalytic rates toward soluble starch relative to AmyA. AmyC has similar k _cat and K _m for oligosaccharides to other Rhizopus and Aspergillus glucoamylases; however, the enzyme has a 2-fold lower K _m ^maltose . AmyD has a 3-fold higher K _m and lower k _cat for maltooligosaccharides than AmyC and other glucoamylases. AmyC (but not AmyD) exhibits substrate inhibition. K _i for substrate inhibition decreases with increasing length of the oligosaccharides. Data from pre-steady-state binding of AmyC to maltose and maltotriose and pre-steady-state to steady-state catalytic turnover experiments of AmyC acting on maltotriose were used to interrogate models of substrate inhibition. In the preferred model, AmyC accumulates an enzyme-maltose-maltotriose dead-end complex in the steady state.     

Synthesis and crystal structure of <Emphasis Type="Italic">N,N</Emphasis>-dimethylbiguanidinium hexafluorosilicate

The complex [(CH₃)₂NC(NH₂)NHC(NH₂)NH₂]SiF₆ (I) was synthesized and its structure was determined by X-ray crystallography. The crystals are monoclinic: a = 7.4346(10) Å, b = 12.7628(10) Å, c = 11.0828(10) Å, β 104.080(10)°, V = 1020.01(18) ų, ρ_calc = 1.780 g/cm³, μ(MoK _α) = 0.302 mm^?1, Z = 4, space group P2₁/c. The crystals of I are composed of SiF ₆ ^2? anions (Si-F, 1.657(2)–1.699(2) Å) and N,N-dimethylbiguanidinium (H₂L²⁺) cations combined in a framework by interionic H-bonds NH···F. In the cations, protonation sites are the terminal imide groups.