Influence of the steric effect on the spectral properties of benzoylacetonatoboron difluorides

The structures and spectral luminescence properties of two similar in structure β-diketonatoboron difluorides were studied in comparison. One of them (1-(2,4,6-trimethyl-phenyl)butane-1,3-dionatoboron difluoride (1)) contains two methyl groups in the both ortho-positions of the phenyl ring, which excludes the formation of rotamers with the planar configuration. In the second compound, 1-phenylbutane-1,3-dionatoboron difluoride (2), the α-phenyl substituent can rotate freely. The steric factor exerts no effect on monomer fluorescence but substantially affects the ability of benzoylacetonatoboron difluorides to undergo intermolecular interactions, which leads to considerable differences in the luminescence properties of concentrated solutions and crystals of compounds 1 and 2.     

Mechanical properties of ZnSe : Cr2+ single crystals

The microhardness of single-crystal samples of ZnSe: Cr²⁺ with a chromium concentration in the range from 3.3 × 10¹⁷ to 4.0 × 10¹⁹ cm^?3 has been studied. The microhardness as a function of the load on the indenter on the faces (111), (1 $\bar 1$ 0), and (001) of the ZnSe: Cr²⁺ and ZnSe samples has been measured. It has been established that doping of zinc selenide with chromium leads to a decrease in the anisotropy of the mechanical properties and stabilization of the cubic sphalerite structure.     

Physicomechanical Properties of Photocured Composites as Influenced by the Degree of Filling with Silica of Various Particle Sizes

The strength of photocured composites as influenced by the concentration and specific surface area of a silica filler was studied.     

Hydrodynamic test bench

Technical Physics - Methods of laboratory modeling of 2D water flows in a rectangular channel are developed. The flow is produced in a vertical tube of a rectangular cross section when water flows...     

Coordination polymer of uranyl nitrate with 4,4,10,10-Tetramethyl-1,3,7,9-Tetraazaspiro[5.5]undecane-2,8-dione (Spirocarbone, Sk): Synthesis and study of molecular and crystal structures

The coordination polymer {[UO₂(NO₃)₂(C₁₁H₂₀N₄O₂)] · 2H₂O} _n (I) was obtained and examined by X-ray diffraction. The crystals are monoclinic, space group C2/c; a = 23.1386(13), b = 5.41575(15), c = 19.7769(11) Å, β = 125.285(8)°, V = 2023.01(17) ų, ρ_calcd = 2.20 g/cm³, Z = 4. The U atom occupies a special position in the center of inversion. Its coordination polyhedron is a distorted hexagonal bipyramid with axial oxo ligands. In the equatorial plane, the U(1) atom is coordinated by four O atoms of two bidentate nitrate anions and two O atoms of two carbonyl groups of organic spirocarbone (Sk) molecules, which are related by the symmetry operation (0.5 ? x, 0.5 ? y, ?z). In the crystal, polymer chains are parallel to the direction (101). Water molecules are hydrogen-bonded to the N(1) atom of ligand Sk; in addition, they are linked together by the intermolecular hydrogen bonds O(6)-H(6d)…O(6)ⁱ(ⁱ1/2 ? x, ?1/2 + y, 1/2 ? z); H…O 2.11 Å angle O-H…O 160°) and to the nitrate anions by the hydrogen bonds O(6)-H(6e)…O(3)ⁱ; H…O 2.29 Å; the angle O-H…O 149°). In the crystal, hydrogen-bonded water molecules form chains along the axis y that are perpendicular to the coordination polymers. To verify the purity of complex I, the Rietveld refinement of its X-ray powder diffraction pattern was performed. At room temperature, the unit cell parameters are a = 23.2965(6), b = 5.51225(15), c = 19.8588(6) Å, β = 125.6063(17)°, V = 2073.40(10) ų.     

Hydrogenative Depolymerization of End-of-Life Polycarbonates by an Iron Pincer Complex

Chemical recycling processes can contribute to a resource-efficient plastic economy. Herein, a procedure for the iron-catalyzed hydrogenation of the carbonate function of end-of-life polycarbonates under simultaneous depolymerization is presented. The use of a straightforward iron pincer complex leads to high rate of depolymerization of poly(bisphenol A carbonate) and poly(propylene carbonate) yielding the monomers bisphenol A and 1,2-propanediol, respectively, as products under mild reaction conditions. Furthermore, the iron complex was able to depolymerize polycarbonates containing goods and mixture of plastics containing polycarbonates.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.