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[en] Analysis of the parameters of anisotropic atomic displacements in various chemical compounds reveals a feature characteristic of a donor-acceptor bond: the ellipsoids of anisotropic displacements of the atoms involved in this bond are elongated in the direction of the bond. The explanation of the effect observed is proposed

[en] The molecular and crystal structures of 1-methyl-2-oxo-3-acetoxy-4-hydroxy-4-(phenyl)hydropyridine, 1-ethyl-2-oxo-3,4-dihydroxy-4-(pyridyl)piperidine, and 1-benzyl-2-oxo-3,4-dihydroxy-4-(pyridyl)piperidine are determined by X-ray diffraction analysis. These three hydroxy derivatives of hydropyridine are the convenient model compounds in studies of the influence of intramolecular and intermolecular hydrogen bonds on the conformation and packing of molecules in crystals. The molecules of hydroxy derivatives possess a considerable conformational flexibility and can form an extended network of intramolecular and intermolecular hydrogen bonds. It is shown that these compounds more often than others form noncentrosymmetric and polysystem crystals. The role of the molecular association and the type of hydrogen-bonded associates (syntons) in crystal packing are discussed

[en] The crystal structures of two compounds--3-benzoyl-4-hydroxy-4-phenyl-(N-methyl)piperidine (I) [orthorhombic crystals, space group P2₁2₁2₁, Z = 4] and 5-hydroxymethylene-4-phenyl-(N-methyl)-1,2,5,6-tetrahydropyridine (II) [monoclinic crystals, space group P2₁/n, Z = 4]--are determined by X-ray diffraction. In I, the weak intermolecular OH···N hydrogen bonds link the molecules related by the a translation into homochiral chains. In II, the OH···N hydrogen bonds link the molecules into infinite homochiral chains twisting about the crystallographic screw axes 2₁(y). The helices are additionally strengthened by the short CH···O contacts

[en] Yb(ReO₄)₃ prepared in the course of slow crystallization of the melt in the air was studied by X-ray diffraction analysis 298 K, 329 reflections, R=0.083, R₂=0.102). The crystals are hexagonal, a=9.999 (4), c=6.070 (2) A, Z=2, sp.gr. P6₃/m. The structure is similar to CdTh(MoO₄)₃ type and it is built of columns formed by Y atom (three vertex trigonal prism) and Re atom (tetrahedron) polyhedrons. Interrelation of Yb(ReO₄)₃ and apatite structures is discussed

[en] Crystallization of aqueous solutions of equimolar quantities of NH₄ReO₄ and M(ReO₄)₃ with M = Sc and In at room temperature was used to prepare isostructural binary NH₄M(ReO₄)₄ · 4H₂O perrhenates. X-ray diffraction study was conducted for them. Tetragonal (sp.gr. P4n2) crystals NH₄M(ReO₄)₄ · 4H₂O (M = Sc, In) are characterized respectively by a = 12.439, 12.460, c = 6.114, 6.123 A, Z = 2, d_clc = 3.997, 4.199 g/cm³. M³⁺ and NH₄⁺ ions, forming the ordered motive of white tin and characterized by eightfold coordination by oxygen, are bonded into frame through bridge ReO₄ tetrahedrons and water molecules. 11 refs.; 2 figs.; 4 tabs

[en] The structure of Ba(ReO₄)₂·4H₂O crystals of monoclinic modification (a=7.371, b=12.572, c=12.156 A, β=90.09 deg, Z=4, sp.gr. P2₁/n) prepared at room temperature from aqueous solution was studied by the method of X-ray diffraction analysis

[en] The structure of monoclinic sesquihydrate of lithium perrhenate LiReO₄x1.5H₂O (a = 10.853(2), b = 13.094(3), c = 13.583(2) A, β 90.44 (2), Z = 16, d_calcld. = 3.870 g/cm³, space group is P2₁/c) has been studied by X-ray diffraction method. The structure is built of infinite columns along [100] formed by Li(H₂O)₃O₃ octahedrons bonded by common edges or faces. The condensation of the columns into the frame is realized via isolated bridge tetrahedrons of ReO₄. Mean Li-O distances equal 2.15(3), Re-O distances being 1.72(1) A. 14 refs.; 4 tabs

[en] Mechanical mixtures of monocrystals of two polymorphous modifications of lutetium perrhenate tetrahydrate Lu(ReO₄)₃·2H₂O: the earlier described triclinic one and a monoclinic modification, isolated for the first time and belonging to a certain new structural type, are obtained by crystallization of Lu(ReO₄)₃ aqueous solution at 15-20 deg C above H₂SO₄. For monoclinic Lu(ReO₄)₃·4H₂O crystal structure is studied by the X-ray structural analysis method. The crystal lattice parameters are as follows: a = 7.273(1), b = 14.786(3), c = 13.093(2) A, β = 93.63(1) deg, Z = 4, sp. gr. P2₁/n. The structure consist of endless chains along [100], formed by interconnected LuO₈ polyhedrons and ReO₄ tetrahedrons. Chains are linked by hydrogen bond. (author)

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