Synthesis of chiral nopinane annelated 3-methyl-1-aryl-1H-pyrazolo[3,4-b]pyridines by condensation of pinocarvone oxime with 1-aryl-1H-pyrazol-5-amines

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One-pot two-step stannylation/Stille homocoupling of aryl bromides and iodides under solvent-free conditions

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Chiral recognition capabilities of melamine and cyanuric acid supramolecular structures

Currently, there are numerous papers that discuss local chiral domains in supramolecular structures of achiral molecules established using the STM method, and by using DFT calculations. However, there are no data regarding the obtainment of macroscopically chiral 2D-supramolecular structures from achiral molecules. In this study, melamine and cyanuric acid supramolecular structures were self-assembled on a graphitized carbon black surface, which had a surface structure that was identical to HOPG, and also on the surface of an inert solid support for chromatography. Chirality induction according to the Kondepudi effect was used. For the supramolecular structures, MD calculations showed the possibility of obtaining a chiral structure. To establish macroscopic chirality, we proposed the use of the difference in enantiomer adsorption on the modified adsorbents. For this, two indirect methods were used: static adsorption with a polarimetric control and gas chromatography. Both methods indicated the chiral recognition ability of the adsorbents used.     

Synthesis and characterization of the new high pressure phases ACu3 V4O12(A=Gd,Tb, Er)

New ACu₃V₄O₁₂ (A=Gd, Tb, Er) phases have been prepared at high pressure and high-temperature conditions (P～8–9 GPa, T～1000°C) in a toroid-type high pressure cell. These compounds crystallize in the cubic symmetry with a perovskite-like structure. At ambient pressure, they are paramagnetic and have activation-type conductivity. The effect of high pressure (10–50 GPa) on the electrical properties of the materials was analyzed in the temperature range from 78 to 300 K. Pressure ranges of the transition from activation type to metallic conductivity have been determined. The crystal structure of ACu₃V₄O₁₂ (A=Gd, Tb, Er) was found to be stable up to 50 GPa.     

Influence of atmospheric humidity on the symmetry and phase transitions of layered potassium oxyfluorides K2NbOF5 · H2O

Crystals of K₂NbOF₅ · H₂O have been grown, polarization optical investigations have been performed, and the birefringence and rotation angle of the optical indicatrix have been measured in the temperature range 100–400 K. It has been found that, depending on the degree of atmospheric humidity, the layered K₂NbOF₅ · H₂O crystal at room temperature can be in three states, namely, A, B, and C, which differ in symmetry and properties of the crystal. The K₂NbOF₅ · H₂O crystal in the A state exists at a relative humidity RH = 90–100% and undergoes a first-order improper ferroelastic phase transition P $\bar 1$ ? C2/m, which is accompanied by strong anomalies of the optical characteristics, twinning, and shear strain x ₆ at temperatures T ₂ ^↓ = 308 K and T ₂ ^↑ = 313 K. The most stable state of the K₂NbOF₅ sdH₂O crystal is the B state (RH = 20–90%), which retains the monoclinic symmetry C2/m in the temperature range 100–370 K. In a dry atmosphere (RH = 0–20%) or at T ₁ ≈ 370 K, the crystal becomes anhydrous (K₂NbOF₅) with the symmetry P4/nmm (the C state). The difference between the crystals in the states A and B is explained by the presence or absence of water molecules in interlayer spaces.     

Ferroelastic phase transition in elpasolite Tl2KInF6

A new elpasolite Tl₂KInF₆ has been synthesized. This compound undergoes at 228 K a ferroelastic phase transition from a room-temperature Fm3m variety to a monoclinic variety. X-ray, optical, calorimetric and DTA studies under hydrostatic pressure have been performed and compared with other elpasolite-type fluorides.     

Nontargeted NMR Analysis To Rapidly Detect Hazardous Substances in Alcoholic Beverages

Nuclear magnetic resonance spectroscopy is introduced for the analysis of alcoholic beverages in the context of governmental health and safety control. For sample preparation of all types of alcoholic beverages, only addition of buffer is required as single step. To detect potentially unsafe samples especially in the context of unrecorded alcohol (i.e., illegally or informally produced alcohol), a nontargeted approach based on principal component analysis (PCA) was applied. The PCA scores plot of 304 samples clearly shows seven conspicuous samples with highly divergent scores from the rest of the samples. These samples contained hazardous substances such as diethyl phthalate or polyhexamethyleneguanidine, as well as extremely high concentrations of methanol or ethyl carbamate. In addition to the nontargeted approach, partial least squares regression allowed us to quantify several parameters such as methanol, higher alcohols, 2-phenyl alcohol and ethyl acetate with high correlation to gas chromatographic reference analysis (R ² = 0.92−0.98).