New binuclear complex of bis(2,4,6,8-tetramethyl-2,4,6,8- tetraazabicyclo(3.3.0)octane-3,7-dione-<Emphasis Type="Italic">O,O</Emphasis>')-diaquatetrakis(nitrato-<Emphasis Type="Italic">O,O</Emphasis>')-dimanganese(II) monohydrate: Synthesis and crystal structure

The centrosymmetric binuclear manganese(II) nitrate complex with a bicyclic bis-carbamide, namely, 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar (Mk) [Mn(C₈H₁₄N₄O₂)(H₂O)(NO₃)₂]₂ · H₂O (I), has been synthesized for the first time. The structure of complex I has been solved (CCDC no. 1435139). Crystals of complex I are monoclinic, space group P2₁/c, a = 12.8108(11) Å, _b = 10.0662(2) Å, c = 18.6367(17) Å, β = 136.512(16)°, V = 1654.0(4) ų, ρcalcd = 1.659 g/cm³, Z = 2. Each manganese atom is coordinated to the two oxygen atoms of two Mk molecules related by the symmetry codes (1–x, 2–y, 1–z) and to two bidentate nitrate anions and one water molecule. The coordination polyhedron of the manganese atom is a strongly distorted pentagonal bipyramid. The Mn···Mn distance in the complex is 8.7261(9) Å.     

Kinetics and Mechanism of the Reaction of Triphenylphosphine with Methyl Vinyl Ketone

Russian Journal of General Chemistry - Kinetics of the reaction of triphenylphosphine with methyl vinyl ketone has been studied using the stopped flow technique. The experimental data have...     

New binuclear <Emphasis Type="Italic">bis</Emphasis>(2,4,6,8-tetramethyl-2,4,6,8-tetraazobicyclo(3.3.0)octane-3,7-dione-<Emphasis Type="Italic">O,O</Emphasis>')-tetraaqua-hexakis(nitrato-<Emphasis Type="Italic">O,O</Emphasis>')-disamarium(III) complex: Synthesis and crystal structure

The centrosymmetric binuclear complex of samarium(III) nitrate with bicyclic biscarbamide 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar (Mk) namely, [Sm(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) has been synthesized. Its crystal structure has been characterized (CIF file CCDC no. 1451436). Crystals of complex I are triclinic, space group P1 a = 9.8661(2) Å, b = 10.2913(3) Å, c = 10.9629(3) Å, α = 74.475(2)°, β = 67.802(2)°, γ = 67.570(2)°, V = 942.68(5) ų, ρcalcd = 2.01028 g/cm³, and Z = 1. The samarium atom is coordinated by the two oxygen atoms of two Mk molecules bonded via the symmetry center, three bidentate nitrate anions, and two water molecules. The coordination number of the samarium atom is 10, the coordination polyhedron of the metal atom is a decahedron and the Sm…Sm distance is 9.7904(4) Å.     

Mixed crystals of p-dichlorobenzene with p-bromchlorobenzene in the presence of vacancies in the structure

Polarization studies of low-frequency Raman spectra of solid solutions of p-dichlorobenzene with p-bromchlorobenzene (50% p-dichlorobenzene) were carried out. Analysis of the lattice vibration spectra of these mixed crystals shows that vacancies can be present in their structure. The presence of vacancies is responsible for the emergence of additional lines, including those in the 70 cm^?1 region. The calculation of the diffusion activation energy in a mixed crystal proves that its magnitude is determined by the spatial arrangement of p-bromchlorobenzene molecules in the lattice, their orientation relative to parahalides, and (to a lesser extent) temperature variations.     

Ion Conductivity and Vibrational Spectra of LiNO3–KNO3 + Al2O3 Composites

Russian Journal of Electrochemistry - Composite solid electrolytes are synthesized on the basis of the eutectic nitrate mixture of 0.42LiNO3–0.58KNO3 doped by aluminum oxide nanosized powder....     

Wien effect in CuCl,CuBr and CuI superionic crystals and their melts

The dependence of conductivity of copper (I) halides (CuCl, CuBr, and CuI) and their melts on the electric field strength is studied. Conductivity of superconducting phases and their melts reaches limiting high-voltage values exceeding the usual values by up to 100% even at ∼0.5 MV/m.     

Dielectric anisotropy of 5CB liquid crystal in a decimeter wavelength range

Parallel and perpendicular components of the dielectric constant for 5CB nematic liquid crystal are measured in a relaxation region. Two frequencies f ₁≈30 and f ₂≈350 MHz are determined at which the inversion of the dielectric anisotropy sign is observed. It is shown that the observed sizable high-frequency shift of f ₂ with respect to the value calculated according the Debye theory is caused by the dielectric resonance near the relaxation region.     

Migration of molecules in p-bromochlorobenzene with vacancies in its structure

Based on polarization measurements of the low-frequency Raman spectra of p-bromochlorobenzene and calculations of the frequency spectra of lattice vibrations by the Dean method it is shown that the structure may contain vacancies. Their presence affects the appearance of additional lines in the low-frequency spectrum, particularly in the vicinity of 70 cm⁻¹, and their positions depend weakly on the orientational disorder of the molecules with respect to the para substituents. The activation energies for diffusion in a randomly disordered p-bromochlorobenzene crystal with vacancies in the structure is calculated from atom-atom potentials. It is shown that the value of the activation energy varies along a selected direction and depends on the arrangement of the p-bromochlorobenzene molecules with respect to the para substituents, in contrast to the results for ordered p-dibromobenzene and p-dichlorobenzene. Fiz. Tverd. Tela (St. Petersburg) 40, 1835–1838 (October 1998)     

Study of a Composite Consisting of Metal Nanoparticles in a Dielectric Matrix and Multilayer Bandpass Filters Based on It

Doklady Physics - The frequency and concentration dependences of the effective complex permittivity of a composite consisting of silver nanoparticles in a polystyrene dielectric matrix have been...