Spatial structure of molecular complexes of zinc(II)tetraphenylporphyrin with pyridine and aniline derivatives

Structure of molecular complexes of zinc(II)tetraphenylporphyrin with 4-dimethylaminopyridine and 4-methoxyaniline has been studied by X-ray diffraction analysis. 4-Dimethylaminopyridine is coordinated almost perpendicular to the porphyrin cycle plane, whereas 4-methoxyaniline is coordinated at lower dihedral angle. The hybridization of aniline nitrogen atom in the crystal depends on donor-acceptor properties and the volume of the substituents in the aromatic ring.     

Ordering of tysonite structure in an as-grown Er0.715Ca0.285F2.715 crystal and in a component of annealed two-phase crystal of the Er0.67Ca0.33F2.67 composition

The structures of the as-grown tysonite phase (TP) Er_0.715Ca_0.285F_2.715 as grown and the tysonite component in a crystal of the Er0.67Ca0.33F2.67 composition annealed at 760°C have been determined by X-ray diffraction methods from the main reflections in the sp. gr. P6₃/mmc, Z = 2. Ca²⁺ cations in the Er_0.715Ca_0.285F_2.715 structure occupy the 2c site on the 6₃ axis, thus confirming the conclusion about the symmetrizing effect of alkaline earth cation, which was made previously for the Y_0.715Ca_0.285F_2.715 compound. Er³⁺ cations are disordered over 6h sites around this axis. The Er_0.67Ca_0.33F_2.67 composition contains Er_0.67+δCa_0.33?δF_2.67+δ TP and inclusions of distorted fluorite phase rhβ-Ca₈Er₅F₃₁. The tysonite and two fluorite lattices have no “correct” relationship. Ca²⁺ cations and a half of TP Er³⁺ cations are fixed in the 2c sites, while the other Er³⁺ cations are disordered over the 6h sites. Superstructural ordering occurs in Er_0.715Ca_0.285F_2.715 crystals; however, the process is not completed, as follows from the character of the diffraction pattern. Weak satellite reflections in the diffraction pattern of the Er_0.67Ca_0.33F_2.67 composition are indicative of the development of TP ordering processes but remain unfit for structural calculations.     

Turbulent structure in supersonic jets with a high Reynolds number

The turbulent properties of a supersonic jet were studied related to a high level of pressure pulsation found in model jets of a reentry flight vehicle approaching the landing ground. This study comprised measurements of total pressure at a small-size target using a dynamic pressure probe placed in a free jet. The most comprehensive data about jet turbulence can be obtained by direct transformation of the pressure reading at the stagnation point near the target into the normalized velocity. The oscillogram of normalized velocity produces the velocity average value, root-mean-square value as well as turbulence intensity and turbulence spectrum. It was demonstrated that a high level of turbulence for a high-head jet retains along the supersonic core length and at the beginning of subsonic interval.     

Effect of the Solvent on the Coordination of Pyridine Derivatives with Zn Tetraphenylporphine

The coordination of zinc(II) tetraphenylporphine with pyridines was studied by electronic spectroscopy. Linear correlations were found between the thermodynamic and kinetic parameters of coordination in different solvents. The effect of the solvent on the stability constants of the complexes and the thermodynamics of complex formation are discussed.     

The Intrinsic Fluorine-Ion Conductivity of Crystalline Matrices of Fluoride Superionics: BaF2 (Fluorite Type) and LaF3 (Tysonite Type)

Physics of the Solid State - The intrinsic fluorine-ion conductivity σlat of BaF2 (CaF2 fluorite type) and LaF3 (tysonite type) crystals is studied by the impedance spectroscopy method. These...     

Online resource for theoretical study of hydration of biopolymers

An online resource has been developed for the theoretical study of hydration of biopolymers by the RISM (Reference Interaction Site Model) method, deriving from the integral equation theory of liquids. The online resource is based upon original software developed by the authors and includes all steps in studying a biopolymer with a given spatial structure and force field. It prepares the input data and carries out the RISM calculation yielding the atom-atom correlation functions of the biopolymer with water as solvent. From these functions the algorithm finds atomic partial contributions to the hydration free energy using various free energy expressions from integral equation theory. The calculated results are automatically recorded in a database, and become available on the website as tables of partial thermodynamic quantities. In addition, the website displays an interactive 3D model of a given molecule, the atoms of which can be painted in different colors in accordance with their partial contributions to the thermodynamic quantity chosen by the user. The user can interactively choose atoms on this molecule and their correlation functions will be displayed. The aim of our work was to develop and present a publicly-accessible resource on the basis of original software which could be used for scientific and educational purposes.     

Hydrated Rare Earth Structural Networks containing the Phenylene‐1, 2‐dioxydiacetate (PDDA) Ligand

Reaction of LnCl₃ with Na₂(PDDA) (PDDA = phenylene‐1, 2‐dioxydiacetate) in a 1 to 2 mol ratio in aqueous solution yielded [Ln₂(PDDA)₃(H₂O)₆] · 2H₂O, structurally characterized for Ln = Ce ( 1 ), Sm ( 2 ) (redetermination), Tb ( 3 ) and Y ( 4 ) in a monoclinic C2/c array, a second related structural form [orthorhombic, Pbcn] being obtained for Tb ( 5 ), Ho ( 6 ) and Er ( 7 ). The ‘domains of existence' of these two previously described forms are now extended to Ce–Dy, Y, and Eu–Er, respectively. Reaction under the same conditions for the heavier Yb³⁺ ion yielded [Yb₂(PDDA)₃(H₂O)₆]_(∞|∞) · 4H₂O ( 8 ), orthorhombic, Pbca. In the case of Ln = La the bimetallic species [NaLa(PDDA)₂(H₂O)₂]_(∞|∞) · 4H₂O ( 9 ) was obtained, while reaction of LnCl₃ with Na₂(PDDA) in a 1 to 3 mol ratio led to the isolation of the isotypic (monoclinic, P2₁/c) [NaLn(PDDA)₂(H₂O)₂]_(∞|∞) · 4H₂O) for Ln = Ce ( 10 ) and Sm ( 12 ). With the smaller Ln = Yb, the more definitively bimetallic [NaYb(PDDA)₂(H₂O)₂]_(∞|∞) · 3H₂O ( 13 ) (triclinic, P$\bar{1}$ )) was obtained, the trihydrate solvation ascribed differing from that recorded (dihydrate) in a cosynchronous report.     

Synthesis and Evaluation of Thymol-Based Synthetic Derivatives as Dual-Action Inhibitors against Different Strains of H. pylori and AGS Cell Line

Following a similar approach on carvacrol-based derivatives, we investigated the synthesis and the microbiological screening against eight strains of H. pylori, and the cytotoxic activity against human gastric adenocarcinoma (AGS) cells of a new series of ether compounds based on the structure of thymol. Structural analysis comprehended elemental analysis and ¹H/¹³C/¹⁹F NMR spectra. The analysis of structure–activity relationships within this molecular library of 38 structurally-related compounds reported that some chemical modifications of the OH group of thymol led to broad-spectrum growth inhibition on all isolates. Preferred substitutions were benzyl groups compared to alkyl chains, and the specific presence of functional groups at para position of the benzyl moiety such as 4-CN and 4-Ph endowed the most anti-H. pylori activity toward all the strains with minimum inhibitory concentration (MIC) values up to 4 µg/mL. Poly-substitution on the benzyl ring was not essential. Moreover, several compounds characterized by the lowest minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values against H. pylori were also tested in order to verify a cytotoxic effect against AGS cells with respect to 5-fluorouracil and carvacrol. Three derivatives can be considered as new lead compounds alternative to current therapy to manage H. pylori infection, preventing the occurrence of severe gastric diseases. The present work confirms the possibility to use natural compounds as templates for the medicinal semi-synthesis.     

Optimization of the Compositions of Solid Electrolytes Pb1 – xRxF2 + x with Fluorite-Type Structure in Conductivity and Thermal Stability

Crystallography Reports - The compositions of nonstoichiometric phases Pb1 – xRxF2 + x (CaF2 type, R is a rare-earth element) have been optimized with...