Influence of α-Bi2O3 chemical prehistory on the morphology of the obtaining basic bismuth succinate

The antibacterial drug, basic bismuth succinate of the composition Ñ2Í4(ÑÎÎBiO)2 is shown to obtain expediently by the interaction of bismuth oxide α-Bi2O3 with a succinic acid solution. Using the method of electron microscopy the influence of the chemical prehistory of obtaining the precursor, monoclinic modification of α-Bi2O3, on the morphological features of basic bismuth succinate synthesized from it has been investigated. The composition of Ñ2Í4(ÑÎÎBiO)2 was confirmed by the data of X-ray phase and chemical analyses. Based on the data of grain size analysis, the particle size of the obtained samples of basic bismuth succinate was estimated and the conditions for the synthesis of fine-crystalline C2H4(COOBiO)2, which is necessary for medical applications, were selected.

Preparation of metallic bismuth by reduction of bismuth formates in ethylene glycol medium

Nano -and microcrystalline bismuth metal powders consisting of spherical particles with a size of 150-250 nm were obtained by reducing bismuth formates in an ethylene glycol medium. The phase composition and morphology of the obtained reaction products were studied by X-ray phase and thermal analysis, differential scanning calorimetry, scanning and transmission electron microscopy. Using Uv-vis, it was shown that a bismuth-ethylene glycol complex is formed with an absorption maximum at 249 nm and an extinction coefficient of 5.7×103 (L mol-1 cm-1) in a solution of chloric acid at 23°C. The concentration of bismuth enhances to 0.018 g L-1 in the ethylene glycol medium with a gradual increase in the temperature to 60°C of the reaction mixture. Thermolysis of bismuth glycolate with a composition of Bi2(OCH2CH2O)3 is accompanied by the formation of metallic bismuth at 190°C, which is oxidized to a monoclinic modification of bismuth oxide when the temperature increases in the air.

The crystal structure of ZrCr2D≈4 at 50 K ≤ T ≤ 200 K

Many Laves phases take up considerable amounts of hydrogen to form metallic Laves phase hydrides. They frequently undergo phase transitions driven by ordering phenomena for the hydrogen atom distribution. The cubic Laves phase ZrCr2 takes up hydrogen to form a hydride with almost four hydrogen atoms per formula unit, which undergoes a phase transition to a monoclinic modification at a critical temperature Tc = 250.2 K. Its crystal structure was refined based on neutron powder diffraction data on the deuteride (ZrCr2D3.8 type [T = 1.6 K, C2/c]) at four temperatures in the range 50 K ≤ T ≤ 200 K. The monoclinic low-temperature modification features a strongly distorted square anti-prism ZrD8 and three CrD4 polyhedra with almost fully occupied deuterium sites in saddle-like, distorted tetrahedral and planar configurations. Zr–D distances are in the range 201.4(7) pm ≤ d(Zr–D) ≤ 208.5(8) pm and Cr–D distances in the range 172.9(7) pm ≤ d(Cr–D) ≤ 182.4(8) pm.

A monoclinic modification of (4Z)-1-benzyl-4-(2-oxopropylidene)-2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-2-one

In the title molecule, C19H18N2O2, the orientation of the oxopropylidene substituent is largely determined by an intramolecular N—H...O hydrogen bond. In the crystal, C—H...O hydrogen bonds form zigzag chains, which are elaborated into sheets lying parallel to (101) by complementary C—H...π interactions. Comparisons to the structure of the triclinic modification are made.

Lithium tetrachloridoaluminate, LiAlCl4: a new polymorph (oP12,Pmn21) with Li+in tetrahedral interstices

Dissolving lithium chloride and aluminium chloride in boilingpara- ormeta-xylene and keeping the colourless solution at room temperature led to crystal growth of a new modification of lithium tetrachloridoaluminate, LiAlCl4, which represents a second modification (oP12,Pmn21) of the ternary salt besides the long known monoclinic form [LiAlCl4(mP24,P21/c); Mairesseet al.(1977).Cryst. Struct. Commun.6, 15–18]. The crystal structures of both modifications can be described as slightly distorted hexagonal closest packings of chloride anions. While the lithium cations in LiAlCl4(mP24) are in octahedral coordination and the aluminium and lithium ions in the solid of orthorhombic LiAlCl4occupy tetrahedral interstices with site symmetriesmand 1, respectively, the lithium cation site being half-occupied (defect wurtz-stannite-type structure). From differential scanning calorimetry (DSC) measurements, no evidence for a phase transition of the orthorhombic modification is found until the material melts at 148 °C (Tpeak= 152 °C). The melting point is nearly identical to the literature data for LiAlCl4(mP24) [146 °C; Weppner & Huggins (1976).J. Electrochem. Soc.124, 35–38]. From the melts of both polymorphs, the monoclinic modification recrystallizes.

Low temperature phase transition and structure of CsMgPO4

CsMgPO4 doped in radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at the temperatures close to ambient conditions (-370C) was observed. Information about structural changes is important in order to understand whether it can cause any problem for medical use of this compound. Structural changes have been investigated in detail using synchrotron powder diffraction methods, Raman spectroscopy and DFT calculations. The structure undergoes transformation from orthorhombic modification, sp. gr. Pnma (RT phase) to monoclinic modification, sp.gr P21/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2)Å, b=8.95501(1) Å, c=5.50344(2)Å, β=90.68583(1)0, V=472.198(3) Å3. The framework is made up of alternating magnesia and phosphate tetrahedra sharing vertices with caesium counter cations located in the channels formed. Upon the transformation a combined rotation of PO4 and MgO4 tetrahedral takes place. A comparison with other phase transition in ABW-type framework class compounds is given.