X-ray structure and 1H NMR assignment of 1-methyl-1,4-dihydro-4-oxo-4′-methylthio-3,3′-diquinolinyl sulfide

The title compound (C₂₀H₁₆N₂OS₂) is orthorhombic, with a = 9.290(2), b = 11.874(3), c = 15.971(4) Å and space group P2₁2₁2₁. Two quinoline moieties are nearly perpendicular to each other (103.5(2)°). Two pairs of heteroatoms in ortho-positions are in very close contact. The 4-oxo and 4-methylthio groups are trans-orientated to the central sulfur bridge. The sulfide preserves a skew conformation. The unusual H-2 proton upfield shift is induced by the ring current effect.     

1-Ethyl-3-methylthio-4-thioxo-1,4-dihydroquinoline or 1-ethyl-3-(methylthio)quinolinium-4-thiolate?

The title compound 1 crystallizes in the monoclinic space group C2/c with a = 16.720(4), b = 8.577(1), c = 15.855(4) Å, and = 98.37(1)°. The thiocarbonyl group C – S bond (1.697(4) Å) is longer than those of typical carbon–sulfur double bonds in thiones. Bond lengths and bond angles in the pyridine ring of the title compound are close to the values found for pyridinium salts.     

Continua of interactions between pairs of atoms in molecular crystals

The electron density distributions in crystals of five previously studied DMAN complexes and five Schiff bases (two new ones) have been analysed in terms of various properties of bond critical points (BCPs) found in the pair-wise interactions in their lattices. We analysed the continua of interactions including covalent/ionic bonds as well as hydrogen bonds and all other types of weak interactions for all pairs of interacting atoms. The charge density at BCPs and local kinetic and potential energy densities vary exponentially with internuclear distance (or other measures of separation). The parameters of the dependences appear to be characteristics of particular pairs of atom types. The Laplacian and the total (sum of kinetic and potential) energy density at BCPs show similar behaviour with the dependence being of the Morse type. The components lambda1, lambda2, lambda3 of the Laplacian at BCPs vary systematically with internuclear distance according to the type of atom pair. For lambda1 and lambda2 the distribution is of the exponential type, whereas lambda3 does not seem to follow any simple functional form, consistent with previous theoretical findings. Analytical nonlinear dependences of Laplacian on charge density have been found. They agree reasonably well with those obtained by least square fit of the Laplacian to charge density data. There are four distinct regions of the [symbol: see text]2rho(BCP)/rho(BCP) space, generated by E(BCP) = 0 and G(BCP)/rho(BCP) = 1 conditions. Two regions clearly correspond to the shared-shell and closed-shell interactions and the other two to some intermediate situation.     

Effectiveness of nitric oxide ozonation

Attempts to develop new technologies of NO _x (NO + NO₂) emission reduction are still carried out all around the world. One of the relatively new approaches is the application of ozone injection into the exhaust gas stream followed by the absorption process. Ozone is used to transform NO _x to higher nitrogen oxides which yield nitric acid with better effectiveness. The main objective of this paper was to study the influence of mole ratio (MR) O₃/NO used in the ozonation process of NO _x on the effectiveness of NO _x oxidation to higher oxides. The ozonation process was carried out in a flow reactor for concentrations of nitric oxide in the range of 1.5 × 10⁻⁵−7.7 × 10⁻⁵ mol dm⁻³ and varying O₃/NO mole ratios. Measurements were conducted with the use of a FTIR spectrometer. The results obtained prove that for MR higher than 1, the oxidation effectiveness of nitric oxides generally reaches 95 %, whereas for MR higher than 2, oxidation of NO _x to higher nitrogen oxides is completed.     

Electronic structure and oxygen vacancies in PdO and ZnO: validation of DFT models

PdO is one of the most important catalytic materials currently used in the industry. In redox catalytic reactions involving PdO, the bulk phase is an additional source of oxygen. This leads to strong transformations not only at the surface of PdO but also in the near sub-surface and bulk regions. The redox process is, therefore, governed not only by the extent of PdO d-band filling, but also depends on the material properties of the PdO crystal--the ease with which its structure can be deformed. Methane oxidation is of key industrial interest, and therein the rate of CH(4) conversion depends strongly on the reversible oxygen defects formation on the surface and in the bulk of the catalyst. The present study gives a first insight into these complex phenomena at the atomistic level. Comparison of different density functional theory (DFT) approaches and their capacity to reproduce experimental values of the heat of formation as well as the band gap of the PdO are discussed in detail. Results from DFT calculations for an oxygen vacancy creation in the bulk and on the surface of PdO are presented and compared at the level of accuracy of the implemented approaches with defect calculations for ZnO. Many different modeling approaches based on functionals and pseudopotentials (non-modified PP and empirically tuned) have been evaluated in their aptness to capture key PdO properties. It was shown that simulations with the PP-115 pseudopotential gave the closest possible agreement to the relevant PdO thermodynamic data and energy of oxygen vacancy formation.     

Role of manganese oxide octahedral molecular sieves in styrene epoxidation

Manganese oxide octahedral molecular sieves having 2 x 2 tunnel structure (OMS-2) and synthesized by different methods were used for studying styrene oxidation with tert-butyl hydroperoxide (TBHP) as the oxidant. The catalytic activity of the as-synthesized OMS-2 materials was investigated. The physical and chemical properties of the OMS-2 materials are related to their activity in styrene oxidation. This particular study emphasizes the acid-base properties and the porous nature of these materials, and their role in styrene oxidation. Results of styrene oxidation reveal that acidity coupled with high porosity play a crucial role in these catalytic reactions. A desired acidity coupled with pore volume found in OMS-2 synthesized by reflux methods (OMS-2(R)) and high-temperature methods (OMS-2(HT)) produces materials with higher styrene conversion and styrene oxide selectivity when compared with OMS-2 synthesized by solvent free (OMS-2(S)), microwave (OMS-2(MW)), or hydrothermal methods (OMS-2(HY)). Transition metal doped OMS-2 catalysts show better selectivity of styrene oxide when compared to their undoped catalysts.     

Assembly of a novel supramolecular synthon of calix[4]arene presenting four carboxylic acids

An extremely complex solid state structure described by two virtual channels and a 2-D square grid of hydrogen bonds is generated by four carboxylic acids groups of calix[4]arene tetrabutyroxycarboxylic acid.     

Non-symmetrical bent-shaped compounds containing a chiral moiety

The synthesis and mesomorphic properties of new non-symmetrical bent-shaped compounds containing a chiral moiety are reported. These materials were built up from 3-hydroxybenzoic acid as a central unit with a chiral terminal group derived from lactic acid. A columnar phase of the B_1REV type with tilted molecules was observed in a wide temperature range down to room temperature. The ferroelectric-like character of switching with one peak in a half-period of the triangular electric field was observed and supported by texture observations and electro-optical changes. A longer terminal group ending with a double bond makes the compounds ready for polymerisation.