Oxythiamine hexafluorophosphate monohydrate,a thiamine antagonist with the same conformation as ­thiamine

In the title compound, 3‐[(3,4‐di­hydro‐2‐methyl‐4‐oxopyrimidin‐5‐yl)­methyl]‐5‐(2‐hydroxy­ethyl)‐4‐methyl­thia­zolium hexa­fluoro­phosphate monohydrate, C₁₂H₁₆N₃O₂S⁺·PF₆^?·H₂O, oxy­thi­amine is a monovalent cation with a neutral oxo­pyrimidine ring. The mol­ecule assumes the F conformation, which is a common form for thi­amine but which is substantially different from the unusual V conformation found in the chloride and hydro­chloride salts of oxy­thi­amine. The anion‐bridging interaction, C—H?anion?pyrimidine, is emphasized as being important for stabilization of the F conformation.     

Structure Determination of an AgI‐Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1H/15N/109Ag NMR Spectroscopy

The structure of an Ag^I‐mediated cytosine–cytosine base pair, C–Ag^I–C, was determined with NMR spectroscopy in solution. The observation of 1‐bond ¹⁵N‐¹⁰⁹Ag J‐coupling (¹J(¹⁵N,¹⁰⁹Ag): 83 and 84 Hz) recorded within the C–Ag^I–C base pair evidenced the N3–Ag^I–N3 linkage in C–Ag^I–C. The triplet resonances of the N4 atoms in C–Ag^I–C demonstrated that each exocyclic N4 atom exists as an amino group (?NH₂), and any isomerization and/or N4–Ag^I bonding can be excluded. The 3D structure of Ag^I–DNA complex determined with NOEs was classified as a B‐form conformation with a notable propeller twist of C–Ag^I–C (?18.3±3.0°). The ¹⁰⁹Ag NMR chemical shift of C‐Ag^I‐C was recorded for cytidine/Ag^I complex (δ(¹⁰⁹Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C–Ag^I–C base pair.     

Weyl modules,Demazure modules and finite crystals for non-simply laced type

We show that every Weyl module for a current algebra has a filtration whose successive quotients are isomorphic to Demazure modules, and that the path model for a tensor product of level zero fundamental representations is isomorphic to a disjoint union of Demazure crystals. Moreover, we show that the Demazure modules appearing in these two objects coincide exactly. Though these results have been previously known in the simply laced case, they are new in the non-simply laced case.     

Mesomorphic properties of 2-acyloxy5-(4-alkoxyphenylazo)tropones, 2-acyloxy-5-(4-alkylphenylazo)tropones,and 2-acyloxy-5-(4-alkoxycarbonylphenylazo)tropones

Three series of mesomorphic 2-acyloxy-5-phenylazotropones with alkoxy, alkyl, and alkoxycarbonyl groups at C-4 on the phenyl ring were prepared. It was known that the corresponding 5-phenylazotropolone derivatives and their methyl ethers were not mesomorphic. 2-Acetyl-5-(4-hexyloxyphenylazo)tropone, however, shows a monotropic smectic A phase. Even an acetyl group is therefore able to induce a mesophase. The effects of terminal substitution of the tropone ring by groups such as alkoxy, alkoxycarbonyl, and alkyl on the clearing points are discussed.     

Effect of polymer addition amount and type on thermal decomposition behavior of spray-dried particles comprising ammonium nitrate,potassium nitrate,and polymer

Certain properties of ammonium nitrate (AN), such as high hygroscopicity and the thermal transformation of the crystal structure accompanied by volume changes, pose problems for industrial applications of AN. To solve these problems, we previously prepared AN-based particles by spray-drying. The particles contained potassium nitrate (PN) as a phase stabilizer and a polymer (e.g., PVA, CMCs, and Latex) to produce a moisture-resistant material. Herein, we investigate the thermal decomposition of spray-dried AN/PN/polymer particles by differential scanning calorimetry and Thermogravimetry–Differential thermal analysis. Comparison of the thermal decomposition of AN/PN/polymer materials with different amounts and types of polymers suggested that thermal decomposition at lower temperatures resulted from the reaction of AN with the molten polymer or decomposition products derived from the polymer. Therefore, it can be concluded that the thermal stability of the AN/PN/polymer was exclusively determined by the thermal properties of the polymer components.     

Molecular dynamics simulation of the mixed anion glasses Li4SiO4---Li3BO3

The structure and the mixed anion effect in the conductivity have been examined for the mixed anion glasses Li₄SiO₄---Li₃BO₃ by molecular dynamics (MD) simulation and X-ray diffraction (XRD) analysis. Structure factors derived from the MD simulation are in good agreement with those from derived from the XRD analysis of the actual glasses, showing that the MD simulation successfully reproduces the actual glass structure. Moreover, the enhancement of the diffusion coefficients of the Li⁺ ions in the middle of the composition range in the system Li₄SiO₄---Li₃BO₃ is simulated by the MD calculation. Structural analysis of the glasses derived from the MD simulation revealed that the increase in the halfwidth of the modified radial distribution function of the Li---O pairs due to the mixing of two ortho-oxoanions is one of the factors in the origin of the mixed anion effect in the conductivity.     

Thermal behavior of amide substituted diacetylenes

Diacetylenes substituted with various amide groups were prepared and their solid-state polymerization behavior was studied. A calorimetric study of the isothermal polymerization of 1,6-diacetylamino-2,4-hexadiyne was performed in detail. This compound has an extremely high reactivity. The reaction proceeded very quickly and the ultimate conversion reached over 40% slightly above room temperature. The feature of the reaction resembles those observed in the solid-state polymerization of other diacetylene compounds, i.e., the reaction proceeds slowly in the initial stage, but the rate of reaction increases drastically at about 5% conversion to polymer. Quantitative conversion, however, was not attained at any temperature, and the reaction leveled off within 1.5 h. It is assumed that the reaction cannot continue owing to the distortions generated in the crystals during the polymerization process. The crystalline state of the polymer obtained was highly disordered.     

Mesomorphic properties of monocyclic troponoids with a semi-fluorinated side group

Eight types of monocyclic troponoids with alkoxy, acyloxy, and semi-fluorinated side chains were synthesized to investigate their thermal behaviour. They showed smectic A phases. The troponoids with a fluorinated side chain had higher transition temperatures than the corresponding non-fluorinated compounds.     

立体拥挤二苯基卡宾分子结构的电子效应

通过对二苯基重氮甲烷的光照射产生了一系列具有对称对位取代基的三线态二 (2 ,6 二甲苯基 )卡宾 .用电子顺磁共振波谱对其进行了研究 .通过对不同粘度的基质 (matrix)中零磁场分裂参数D和E的测定 ,依据电子自旋离域取代基常数σ 对三线态二苯基卡宾的分子结构的取代基效应进行了分析 .并通过对卡宾的热消失温度及其室温脱气苯溶液中寿命的测定 ,对三线态二 (2 ,6 二甲苯基 )卡宾的稳定性进行了定量考察 .结果表明 ,对卡宾中心的自旋电子具有离域效应的取代基使三线态二 (2 ,6 二甲苯基 )卡宾采取低能稳定的直线型结构 ,且显示了更好的热稳定性和更长的寿命 .     

Development of a finite-temperature density functional approach to electrochemical reactions

We present a computational method to calculate the electronic states of a molecule in an electrochemical environment. The method is based on our recently developed finite-temperature density functional theory approach to calculate the electronic structures at a constant chemical potential. A solvent effect is treated at the level of the extended self-consistent reaction field model, which allows considering a nonequilibrium solvation effect. An exchange-correlation functional with a long-range correction is employed in this calculation, because the functional is adjusted so that the derivative discontinuity of energy with respect to a number of electrons could be satisfied. It has been found that the derivative discontinuity condition plays a crucial role in an electrochemical system. The computational results are presented for a reaction of NO(+) + e(-) <==> NO in chemical equilibrium. Owing to the improvement in the solvation effect and the exchange-correlation functional, the calculated activation free energy is in good agreement with experimental results.