Hybrid materials based on polymethylsilsesquioxanes containing Fe,Pt, and Fe–Pt metallic nanoparticles

New hybrid materials based on Pt, Fe, and Pt–Fe nanoparticles stabilized in a matrix of polymethylsilsesquioxane nanogel and ultrahigh molecular weight polyethylene (UHMWPE) were prepared. Metal vapor synthesis was used to produce mono- and bimetallic nanoparticles. It was shown that organosilicon nanogel effectively stabilizes Pt nanoparticles with an average size of 0.9 nm. Using the nanogel results in the formation of superparamagnetic Fe particles 3–5 nm in size that consist of ferromagnetic Fe⁰ core and antiferromagnetic shells of Fe oxides. It is established that using an organosilicon matrix in the formation of Pt-Fe/UHMWPE systems helps reduce the average particle size of Fe in the material from 6.5 to 4.5 nm and narrow their particle size distribution. The composition, magnetic and electronic characteristics of the nanocomposites are studied via transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, XANES, and EXAFS.     

Studying the local structure of liquid in chloro- and alkyl-substituted benzene derivatives via the molecular scattering of light

The coefficients of scattering and the depolarization of scattered light are measured in liquid benzene, chlorobenzene, o-dichlorobenzene, o-chlorotoluene, toluene, and o-xylene in the temperature range of 293?368 K at a wavelength of 546 nm. Isothermic compressibility, internal pressure, and the functions of radial and orientational correlation are calculated for these liquids in the indicated temperature range, using the classical theory of molecular light scattering. We show that the local structure of these liquids is determined by orthogonal contacts between benzene rings (the T-configuration) and stacked (S-type) configurations. T-configurations predominate in benzene, chlorobenzene, and o-chlorotoluene, while toluene, o-xylene, and o-dichlorobenzene are characterized by S-configurations. It is also shown that the local structures of these liquids are reorganized in a certain temperature range.     

Oxidation of white phosphorus by peroxides in water

A mixture of hypophosphorous, phosphorous, and phosphoric acids is formed during the anaerobic oxidation of white phosphorus by peroxides [ROOН; R = Н, 3-ClC₆H₄CO, (СН₃)₃С] in water. The rate of reactions grows considerably upon adding nonpolar organic solvents. The activity series of peroxides and solvents are determined experimentally. NMR spectroscopy shows that the main product of the reaction is phosphorous acid, regardless of the nature of the peroxide and solvent. A radical mechanism of oxidation of white phosphorus by peroxides in water is proposed. It is initiated by the homolysis of peroxide with the formation of НO^? radicals that are responsible for the homolytic opening of phosphoric tetrahedrons. Further oxidation and stages of the hydrolysis of intermediate phosphorus-containing compounds yield products of the reaction.     

Photochemical oxidation of persistent cyanide-related compounds

Russian Journal of Physical Chemistry A - Kinetic regularities of the photolysis of thiocyanate solutions using of mono- and polychromatic UV radiation sources with different spectral ranges are...     

Local atomic and electronic structure of quantum dots based on Mn- and Co-doped ZnS

Solid solutions of zinc sulfide with manganese and cobalt are synthesized. Based on the analysis of X-ray diffraction profiles the conclusion is drawn about the formation of a hexagonal wurtzite type structure in the synthesized quantum dot (QD) solutions. The average crystallite sizes are 8 nm and 22 nm for the samples with manganese and cobalt respectively. Results of IR and optical spectroscopy are consistent with the powder X-ray diffraction and X-ray fluorescence data. The question about particle aggregation in isopropanol and DMF solutions is considered. The QD structures based on ZnS particles doped with Mn and Co transition metal atoms are modeled. The possibility to apply X-ray absorption near edge structure (XANES) spectroscopy to verify the atomic structure parameters around the positions of doping transition metal atoms in QDs of the ZnS family is shown. Partial densities of ZnS:Mn and ZnS:Co electronic states are calculated.     

Structure–reactivity relationship in Diels–Alder reactions obtained using the condensed reaction graph approach

By the structural representation of a chemical reaction in the form of a condensed graph a model allowing the prediction of rate constants (logk) of Diels–Alder reactions performed in different solvents and at different temperatures is constructed for the first time. The model demonstrates good agreement between the predicted and experimental logk values: the mean squared error is less than 0.75 log units. Erroneous predictions correspond to reactions in which reagents contain rarely occurring structural fragments. The model is available for users at https://cimm.kpfu.ru/predictor/.     

Palladium-containing composite nanomaterials based on polycaprolactam: Formation and structure

Novel Pd(0) nanocomposites using polycaprolactam as a reducing and stabilizing matrix are synthesized. Data on the nanoparticle formation mechanism in a polycaprolactam matrix under the conditions of changing pH of the medium and reagent concentration ratios are obtained. The nanocomposite structure is studied by electron and infrared spectroscopy, X-ray diffraction analysis, atomic force and transmission electron microscopy. The size of metal-containing particles in the composite composition and their size distribution are determined. The obtained nanocomposites can serve as heterogeneous catalysts.     

Crystal structures of binuclear Bi(III) chloride and bromide complexes with some cations — Alkylated pyridine derivatives

By a reaction of [BiX₆]^3– with salts of various N-alkylated pyridine derivatives in 2M HX (X = Cl, Br), (N-BzPy)₄[Bi₂X₁₀] complexes (X = Cl (1), Br (2), (4-MePyH)₄[Bi₂Cl₁₀] (3)) are obtained and structurally characterized.     

Short-time isoprene polymerization under the action of a titanium–magnesium catalyst

The short-time polymerization of isoprene under the action of a TiCl₄/MgCl2?i-Bu₃Al heterogeneous catalyst has been investigated. Pulse mixing of the catalyst and monomer in a cylindrical tubular reactor with a certain length followed by ethanol injection has made it possible to carry out polymerization for 0.1?0.7 s. In the first 0.3 s, when there is a considerable rise in the activity of the catalyst, living polymerization of isoprene takes place. In this period, polyisoprene has up to 95% trans-1,4 units. Extending the polymerization time to 0.7 s diminishes the average molar mass of polyisoprene, broadens its molar mass distribution, and decreases the concentration of trans-1,4 units to 83%. The data of this study have been analyzed on the basis of the kinetic continuity of the polymer chain initiation and growth.     

Theoretical investigation of the molecular structure and spectroscopic properties of oxicams

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently prescribed drugs and have multiple therapeutic uses. These drugs are predominantly used for the treatment of musculoskeletal diseases because of their analgesic, antipyretic, and antiplatelet activities. Oxicams constitute an interesting class of organic compounds and have been investigated in the search for new analgesic and anti-inflammatory drugs. In the present work, a theoretical investigation of the molecular structure and spectroscopic properties of a series of five oxicams in different solvents was performed using density functional theory (DFT) methods. The geometric optimizations of the oxicams were carried out using the M06 density functional and the CBSB7 basis set. The infrared data were all obtained at the same theoretical level. The UV-Vis absorption and NMR data of some oxicams were calculated using the DFT and CBSB3 basis sets. The analysis of structural parameters, particularly the bond length and spectroscopic data, indicated that interactions occurred between the hydrogen bond types for 4-meloxicam, isoxicam, and normeloxicam. Stereoelectronic interactions caused by the substitution of alkyl groups caused the bond lengths to elongate. Similarly, the substitution of heteroatoms, such as nitrogen, sulfur, or oxygen, increased the bond lengths and angular stresses.