Tetracyanonickelate compounds as sorptive materials and the substitution of their H2O content by D2O

The compounds NiNi(CN)₄·3,5H₂O and Ni(NH₃)₂Ni(CN)₄·H₂O have been studied to examine the possibility of substituting their H₂O or NH₃ content by D₂O. Contact with D₂O was performed after heating the compounds to several temperatures. Depending on the degree of decomposition of the original compounds different ranges of substitution were possible. In such manner the compounds NiNi(CN)₄·3,5D₂O, NiNi(CN)₄·5D₂O, Ni(NH₃)₂Ni(CN)₄·D₂O, and Ni(D₂O)₂Ni(CN)₄·D₂O were prepared and thermally they were less stable than the original ones. The substitution by D₂O is in agreement with the sorptive properties of the original tetracyanonickelate against different organic compounds using GC, since these could substitute the guest component and sometimes also the ligands during their decomposition.     

Comparison of Phenolic Profile of Balsamic Vinegars Determined Using Liquid and Gas Chromatography Coupled with Mass Spectrometry

Balsamic vinegar is one of the best known and most popular types of vinegar, and it is a rich source of polyphenolic compounds. The quality of balsamic vinegar as well as the content of phenolic substances vary depending on the production method. In the present work, we have developed a method for comprehensive characterization of the content of phenolic compounds in balsamic vinegars based on the combination of gas chromatography (GC) and high-performance liquid chromatography (HPLC) coupled with mass spectrometric detection in single mode (MS) and tandem mode (MS/MS). In total, 14 samples of different types of balsamic vinegar were analyzed without difficulty in sample preparation. The separation conditions and detection parameters of HPLC-MS/MS were optimized and used for the determination of 29 phenolic compounds and 6 phenolic acids. The profile of phenolic compounds was completed by semi-quantitative analysis of volatile organic compounds using GC-MS after optimized headspace solid-phase microextraction. Gallic acid, protocatechuic acid, caffeic acid, and p-coumaric acid have been identified as the major phenolic compounds in balsamic vinegars.     

Kirkwood-Buff integrals and density fluctuations in aqueous solution of caffeine

The Kirkwood-Buff theory is applied to caffeine aqueous solution. The integrals of radial distribution functions are calculated from the osmotic coefficient, density and sound velocity data at 25°C. The results are discussed in terms of density fluctuations of two components and the correlation between them. It is found that the concentration dependence of Kirkwood-Buff integrals reflects the association tendency of caffeine and its strong influence on the properties of the solvent.     

A new supramolecular zinc(II) complex containing 4‐biphenylcarbaldehyde isonicotinoylhydrazone ligand: Nanostructure synthesis,catalytic activities and Hirshfeld surface analysis

A new potentially tridentate hydrazone ligand, 4‐biphenylcarbaldehyde isonicotinoylhydrazone (4‐bpinh), was prepared by the condensation of biphenyl‐4‐carboxaldehyde with isonicotinic acid hydrazide. Then, its nano‐sized and single crystal of zinc complex were synthesized using sonochemical and heat gradient methods, respectively. The structure of complex, [Zn(4‐bpinh)₂ Br₂] (1), was determined by single‐crystal X‐ray diffraction, FT‐IR, and elemental analysis, and the nano‐structure of complex was characterized by FT‐IR, XRD, and SEM. The single crystal X‐ray structure of complex showed that the metal center has a distorted tetrahedral geometry and the hydrazone ligand acts as monodentate trough the pyridyl N atom. Moreover, the analysis of crystal structures indicates the existence of intermolecular interactions such as N/C–H?Br/O, N/C–H?π, and π?π stacking in the stabilization of complex structure which finally led to the formation of the three‐dimensional supramolecular structure. Also, the impact of this interactions was more studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Furthermore, the catalytic activity of 1 was studied in the selective oxidation of various sulfides to corresponding sulfoxides using hydrogen peroxide as the oxidative agent.     

O-17 NMR spectra of ring compounds. Correlation of 17O and 13C methyl substitution parameters

The ¹⁷O NMR spectra of 22 1,3-dioxanes, four exanes, four 4-heterooxanes, four tetrahydrofurans and four 1,3-dioxolanes have been recorded and methyl substitution parameters determined for the 1,3-dioxanes. The parameters, including γ_a, correlate linearly with corresponding ₁₃C parameters for methyloxanes.     

Differential geometry of ray surfaces in anisotropic solids and its contribution to NDE: modelling and experiment

Point-source/point-receiver techniques are one of the most widely used methods for nondestructive evaluation of anisotropic materials. The group velocities resulting from these techniques must be, for further inverse evaluation of elastic coefficients, geometrically converted into corresponding phase velocities. On the other hand, the phase velocities can be determined from a material's response to a line source. But, due to the anisotropy, the short line sources generated by cylindrical lenses are insufficient for reliable determination of the phase velocity. In this paper, a long line source is approximated by a set of linearly arranged point sources. As it follows from the differential geometry of ray surfaces, information obtained from such set of sources is sufficient for determination of phase velocities of both the quasi-transverse and the quasi-longitudinal modes of propagation. Moreover, this approach can be generalized for any arbitrary set of point sources only by employing a proper time-base transformation. The applicability of the presented approaches is illustrated on transversely isotropic and tetragonal fibrous composite materials.     

Coherent "metallic" resistance and medium localization in a disordered one-dimensional insulator

It is believed that a disordered one-dimensional (1D) wire with coherent electronic conduction is an insulator with the mean resistance approximately equal e(2L/xi) and resistance dispersion Delta(rho) approximately equal e(L/xi), where L is the wire length and xi is the electron localization length. Here we show that this 1D insulator undergoes at full coherence the crossover to a 1D "metal," caused by thermal smearing and resonant tunneling. As a result, Delta(rho) is smaller than unity and tends to be L/xi independent, while grows with L/xi first nearly linearly and then polynomially, manifesting the so-called medium localization.