Crystal Structure of A Molecular Complex Compound of Antimony(III) Fluoride with L-Leucine

Single crystal X-ray diffraction analysis is used to determine the crystal structure of a newly synthesized molecular complex compound of antimony(III) fluoride with L-leucine of the composition SbF₃(C6H₁₃NO₂) (orthohombic crystal system: a = 5.7948(8) ?, b = 6.2433(9) ?, c = 28.594(4) ?, Z = 4, P2₁2₁2₁ space group). The structure consists of SbF₃ molecules and L-leucine bound into polymer chains by bidentate bridging carboxyl groups of amino acid molecules. Weak Sb…F(1)^b bonds combine the adjacent chains into polymer ribbons organized by N-H…. F and N-H…. O hydrogen bonds into a framework.     

On clique relaxation models in network analysis

Increasing interest in studying community structures, or clusters in complex networks arising in various applications has led to a large and diverse body of literature introducing numerous graph-theoretic models relaxing certain characteristics of the classical clique concept. This paper analyzes the elementary clique-defining properties implicitly exploited in the available clique relaxation models and proposes a taxonomic framework that not only allows to classify the existing models in a systematic fashion, but also yields new clique relaxations of potential practical interest. Some basic structural properties of several of the considered models are identified that may facilitate the choice of methods for solving the corresponding optimization problems. In addition, bounds describing the cohesiveness properties of different clique relaxation structures are established, and practical implications of choosing one model over another are discussed.     

Effect of Temperature on the Electrorheological Behavior of Porous Chitosan Particles in Polydimethylsiloxane

Doklady Physical Chemistry - The rheological behavior of a 1 wt % suspension of highly porous chitosan particles in polydimethylsiloxane in a high electric field has been studied as a function of...     

Reaction of diphenylphosphinoylallene derivatives of cytisine

Diphenylphosphinoylallenes containing a ClCH₂ group were synthesized, and their reaction with cytisine was studied. It was shown that the reaction involves exclusives as nucleophilic substitution of chlorine in the chloromethyl group. The synthesized conjugates of cytisine with diphenylphosphinoylallene derivatives are of interest as potential agonists of nicotinic acetylcholine neuroreceptors (nAChRs).     

Crystal structure of L-leucinium tetrafluoroantimonate(III)

The crystal structure of L-leucinium tetrafluoroantimonate(III) of the composition (C₆H₁₄NO₂)SbF₄ (orthorhombic symmetry: a = 6.1459(6) Å, b = 14.994(1) Å, c = 24.789(2) Å, Z = 8, P 2₁2₁2₁ space group) synthesized for the first time is determined. The (C₆H₁₄NO₂)SbF₄ structure represents a new structure type of tetrafluoroantimonate(III). It is formed by (C₆H₁₄NO₂)+ cations and chain complex [Sb₂F₈]_n ²ⁿ anions composed of Sb₂F₈ dimers linked into chains by bridging F atoms. The Sb₂F₈ dimers consist of SbF₃ and SbF₅ groups bound by bridging fluoride atoms of the SbF₅ group. Chains in the structure are linked by N-H…F, N-H…O, and O-H…F hydrogen bonds into a three-dimensional framework.     

Determination of the nature and concentration of solutes using the swelling granule method

A procedure and instrument for the determination of dissolved electrolytes and nonelectrolytes in solutions are described. The analysis was performed by measuring the size of a polymer granule placed in the test solution. It was found that various polymers can be used for the determination of the nature or concentration of a solute. This allows one to perform the analysis in various solvents. The use of small granules allows one to decrease the sample volume to tenths fractions of a microliter.     

Spin probe study of acidity of inorganic materials

Acidic characteristics of various inorganic materials, such as silica gel, aluminum, and titanium(IV) oxides, original and modified with F^? and SO ₄ ^2? ions, in the form of hydrogels and nanostructured powders doped by copper(II) ions, are studied. It is shown that pH values inside pores of the studied sorbents (pH_intr) differ from the pH of external solutions by 0.5–1.1 units. In the pores of original γ-Al₂O₃, the pH_intr values are higher, while, in pores of γ-Al₂O₃ samples modified with F^? и SO ₄ ^2? , as well as nonmodified α-Al₂O₃, SiO₂ gel, and TiO₂ hydrogels, pH_intr are lower compared to the pH of the external solution. It is found that pH_intr decreases, as the content of Cu²⁺ ions in the TiO₂ phase grows, and, beginning with a certain moment, it coincides with pH of an equilibrium solution. The pK _a values of functional group dissociation in some materials are determined. It is shown that, using spin probes, that is, pH-sensitive nitroxyl radicals, the electrostatic potential of the surface of nanostructured TiO₂ can be estimated.