The synthesis and molecular structures of 2,5-diarylpyrroles, [{\text{pyr}}^{{\text{Ar}}_{\text{2}} } ]H (Ar = Ph, 2,4-Xyl)

2,5-Di(2,4-xylyl)pyrrole, H, has been synthesized by reaction of the diketone [XylC(O)CH₂]₂ with NH₄OAc in AcOH; the diketone itself is obtained by condensation of XylC(O)Me with XylC(O)CH₂Br in the presence of Ti(OPrⁱ)₄. The molecular structures of both H and H have been determined by single crystal X-ray diffraction, thereby demonstrating that an ortho methyl substituent increases the dihedral angle between the aryl and pyrrolyl groups from 14.5° in H to 24.1° in H.     

Crystallization of the $${\text{Mn}}^{{\text{II}}}[12{\text{-MC}}_{{\text{Mn}}^{{\text{III}}}{\text{(N)shi}}}{\text{-}}4]^{2+}$$ Mn II [ 12 -MC Mn III (N)shi - 4 ] 2 + Structure with 1,2,4-Triazolate from Methanol

Journal of Chemical Crystallography - The metallacrown (MC) dimer complex {MnII(OAc)(1,2,4-trz) $$[12{\text{-MC}}_{{\text{Mn}}^{{\text{III}}}{\text{(N)shi}}}{\text{-}}4]$$...     

CO substitution in Ru3(CO)12 by 2,3-bis(diphenylphosphino)-N-phenyl-maleimide (bppm). X-ray diffraction structure of Ru2(CO)6(bppm)

The cluster Ru₃(CO)₁₂ reacts with the diphosphine ligand 2,3-bis(diphenylphosphino)-N-phenyl-maleimide (bppm) in toluene solution at 100C by fragmentation to give a 2:1 mixture of the donor–acceptor complex Ru₂(CO)₆(-bppm) and the phosphido-bridged species Ru₂(CO)₆ , respectively. The new diruthenium compounds have been isolated by chromatography and characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies, in addition to X-ray diffraction analysis in the case of Ru₂(CO)₆( ₂ -bppm). Ru₂(CO)₆( ₂ -bppm), which exists as two crystallographically independent molecules in the unit cell, crystallizes in the orthorhombic space group Pbca, a = 18.8441(9), b = 21.352(2), c = 36.510(2) Å, V = 14,690(1) ų, z = 16, D _calc = 1.649 g/cm³; R = 0.0356, and R _w = 0.0812 for 17732 observed reflections. The reactivity of the bis(diphenylphosphino)-N-phenyl-maleimide ligand with Ru₃(CO)₁₂ under thermolysis conditions is contrasted with the related diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd).     

Program for calculating the scattering parameters used in the X-ray standing wave method

A computer program for calculating the complex kinematic scattering parameters χ₀, χ_h, and $\chi _{\bar h} $ of X rays, which are Fourier components of the crystal complex susceptibility, as well as some of their combinations, is presented. The values calculated by the program can be used for computer simulation of experimental results obtained by the X-ray standing-wave method. Methods for calculating these parameters on the basis of well-known tables are described in detail. For crystals of complex structure, it is necessary to know their structure and the Debye temperature or specific heat capacity in order to calculate χ_h and $\chi _{\bar h} $ . To calculate χ₀, it is sufficient to know the chemical formula and the density of a material.     

Kinetics of hydrothermal crystallization of quartz in Na2CO3 solutions

The kinetics of crystallization of the {0001}c, {01 $\bar 1$ 1}r, and {10 $\bar 1$ 1}R faces of quartz in 0.5 M Na₂CO₃ (M is molarity) aqueous solutions has been studied in the temperature range 200–450°C. It is established that the dependence of the crystal growth rate on temperature in the logV-1/T, K coordinates is of a parabolic nature. It is most probable that the nonlinearity of this dependence is associated with a deficiency in the solution of silica monomers, taking part in the elementary event of quartz crystallization. The causes of a jumpwise decrease in the activation energy of the growth of the c, r, and R faces at t > 280–325°C are considered.     

Flexoelectric effect and statistical properties in polar liquid crystals

The structural properties and flexoelectric coefficients e ₁ and e ₃ of polar liquid crystals (LCs) such as 4-n-pentyl-4′-cyanobiphenyl (5CB) are studied in the nematic phase by the molecular-dynamics and statistical-mechanics methods. A number of order parameters, $\bar P_{2L} (L = 1,2,3)$ and $\bar P_2 (r)$ , and orientational correlations ξ_λ for the nearest and next-nearest neighbors were investigated. The calculations show the absence of spontaneous polarization $(\bar P_1 \simeq 0)$ in the nondeformed polar 5CB liquid crystal over the entire range of temperatures corresponding to the nematic phase. The origination of spontaneous polarization (characterized by two independent flexoelectric coefficients e ₁ and e ₃) in response to an external deformation of a 5CB sample is studied. The calculated e ₁ and e ₃ coefficients agree well with the experimental data for 5CB obtained by the pyroelectric method.     

On the problem of transient hydrodynamic instability of nematics in magnetic field: I. Instability at splay deformation

A dependence of the square of dimensionless magnetic-field (MF) strength on the square of dimensionless wave vector of the domain structure, $h^2 \left( {\tilde q^2 } \right)$ , is analytically derived for the transient hydrodynamic instability arising at splay deformation under a MF. The domain formation is related to the fold catastrophe; the square of the critical field of domain formation, h _D ² , is determined from the condition ${{\partial \left[ {h^2 \left( {\tilde q^2 } \right)} \right]} \mathord{\left/ {\vphantom {{\partial \left[ {h^2 \left( {\tilde q^2 } \right)} \right]} \partial }} \right. \kern-0em} \partial }\left( {\tilde q^2 } \right) = 0$ . In the general case, the function $h^2 \left( {\tilde q^2 } \right)$ is a ratio of two polynomials whose coefficients for calamitics are determined by combinations of four dimensionless viscosities ν₂/ν₁, ν₆/ν₁, ν₇/ν₁, and ν₈/ν₁. Under some assumptions, the quotient of the polynomials at large $\tilde q^2$ is a quadratic function which allows one to experimentally determine the dimensionless viscosities ν₂/ν₁, ν₆/ν₁, ν₇/ν₁, and α₂/ν₁.     

Synthesis and crystal structure of new carbonate NaPb2(CO3)2(OH)

Crystals of a new lead carbonate, NaPb₂(CO₃)₂(OH), sp. gr. P31c, were prepared by hydrothermal synthesis. The crystal structure was established by the heavy-atom method without knowing the exact chemical formula of the compound. The polar structure of the carbonate and the distortion of the pseudosymmetry described by the supergroup P $\bar 3$ 1c are caused by the acentric arrangement of the oxygen atoms providing the satisfactory coordination of Pb and Na atoms. The bonds between a hydroxyl group and two crystallographically independent Pb atoms are directed along the c-axis and have different lengths. The study of the carbonate by the second harmonic generation method in a temperature range of 20–250°C revealed the nonlinear optical properties comparable with the similar properties of quartz. The comparison of the structure of the new carbonate with a number of carbonates demonstrated that the new compound is structurally similar to ewaldite BaCa(CO₃)₂, diorthosilicate NaBa₃[Si₂O₇](OH), and Ba[AlSiO₄]₂ containing a double silicon—oxygen layer.     

Carbon–hydrogen and carbon–phosphorus bond cleavage in a triruthenium cluster complex containing dppm: The crystal and molecular structures of Ru3(CO)6{μ 3-OPPh2 C2H(C6H4)PPhCH2PPh}(μ 3-OPPh2)Ph and Ru3(CO)6 {μ-OPPh2C2H(C6H4)PPhO}(μ-PPh2)(μ-PPh2O)

The crystal and molecular structures of Ru₃(CO)₆{μ ₃-OPPh₂C₂H(C₆H₄)PPhCH₂PPh}-(μ ₃-OPPh₂)Ph (1) and Ru₃(CO)₆{μ-OPPh₂C₂H(C₆H₄)PPhO}(μ-PPh₂)(μ-PPh₂O) (2) have been determined by single crystal X-ray diffraction. Both complexes contain oxygen atoms oxidatively inserted into phosphorus–ruthenium bonds, and unique σ/π multidentate ligands formed from C $---{\text{H}}$ H and C $--$ P bond cleavage in bis(diphenylphosphino)acetylene and bis(diphenylphosphino)methane. Complex 1 crystallized in the triclinic space group ${\bar 1}$ , with lattice parameters a = 11.642(4) Å, b = 15.018(5) Å, c =16.587(5) Å, α = 2.48(3)°, β = 76.47(2)°, γ = 70.35(3)°, V = 2651.1(15) ų, Z = 2. Complex 2 crystallized in the centered monoclinic space group, C2/c, with lattice parameters a = 34.467(4) Å, b = 14.274(2) Å, c = 23.258(3) Å, β = 5.29(1)°, V = 11394(3) ų, Z = 8.     

Synthesis and Crystal Structure of La(NO<Subscript>2</Subscript>)(SO<Subscript>4</Subscript>)(H<Subscript>2</Subscript>O)

Abstract Single crystals of new open-framework lanthanide sulphate nitrite La(NO₂)(SO₄)(H₂O) has been synthesized, in the presence of 2,6-diformyl-4-chlorophenol. His structure has been determined by X-ray diffraction data: the complex crystallizes in the tetragonal system, space group P4₃, with a = 7.0028(2) (?), b = 7.0028(2) (?), c = 11.8341(4) ?, V = 580.34(3) ?³, Z = 4, D _c = 3.582 Mg m⁻³. The three-dimensional (3D) framework of this compound is built up by the linkages of lanthanide atoms and the oxygen atoms of the sulphate and nitrite groups. The lanthanum atom is 9-fold coordinated. The structure is unfamiliar in lanthanide chemistry and this compound represents the first example of nitrite lanthanide sulphate complex. Graphical Abstract An unfamiliar structure in lanthanide chemistry represented by the first example of nitrite lanthanide sulphate complex is described.      

Crystallographic investigations of 1,4-benzothiazin-2(1H)one and 3-methyl-1,4-benzothiazin-2(1H)one

The crystal structures of 1,4-benzothiazin-2(1H)one (C₈H₇SNO) (I) and 3-methyl-1,4-benzothiazin-2(1H)one (C₉H₉SNO) (II) have been determined by X-ray diffraction methods. I crystallizes in the monoclinic system with space group P2₁/n, while II crystallizes in triclinic with space group P $\bar 1$ . The molecular features in both the structures are almost similar; however, there exists an intermolecular interaction in (II) that could be due to the methyl group.     

Alkali-metal hydrogen selenate-phosphates M 2 H 3(SeO4)(PO4) (M = Rb or K) and M 4H5(SeO4)3(PO4)(M = K or Na)

Crystalline hydrogen selenate-phosphates M ₂H₃(SeO₄)(PO₄) [M = Rb (I) or K (II)] and M ₄H₅(SeO₄)₃(PO₄) [M = K (III) or Na (IV)] were obtained by reactions of Rb, K, and Na carbonates with mixtures of selenic and phosphoric acid solutions. The X-ray structure study of single crystals revealed that I and II are isostructural (sp. gr. Pn). In these structures, SeO₄ and H₃PO₄ tetrahedra are linked by hydrogen bonds to form corrugated layers. Structures III and IV (sp. gr. $P\bar 1$ ) have similar arrangements of non-hydrogen atoms but different hydrogen-bond systems. In III = K₄(HSeO₄)₂{H[H(Se,P)O₄]₂}, the HSeO₄ groups branch from the infinite anionic {H[H(Se,P)O₄]₂} chains. In IV = Na₄[H(SeO₄)₂]{H[H_1.5(Se, P)O₄]₂}, the anionic {H[H_1.5(Se,P)O₄]₂} chains are crosslinked by hydrogen bonds formed by the [H(SeO₄)₂] dimers.     

Formation of zinc oxide quasibicrystal structures

Quasibicrystal structures with interblock boundaries of epitaxial zinc oxide layers on a sapphire substrate along a given direction have been obtained for producing submicron electronic devices. It is shown that the use of the buffer technique allows one to grow on one (10 $\bar 1$ 2) α-Al₂O₃ substrate ZnO layers oriented in the (11 $\bar 2$ 0)and (0001) planes with clearly pronounced interlayer boundaries. The morphology and structural characteristics of these layers are studied.     

Ba1−x R x F2 + x Phases (R = Gd-Lu) with distorted fluorite-type structures—products of crystallization of incongruent melts in the BaF2-RF3 Systems (R = Gd-Lu). III. Defect Ba0.75Lu0.25F2.25 structure. A new {Lu8[Ba6F71]} supercluster of defects

The structure of Ba_0.75Lu_0.25F_2.25 crystals grown from melt has been studied by X-ray diffraction analysis (4729 measured reflections, 269 independent reflections with I > σ (I), R = 1.1%, R _w = 0.7%). The crystals are crystallized in the cubic system, sp. gr. Pm $\bar 3$ m, with the lattice parameter a = 5.9870(9) Å. A new complex of defects is singled out—a supercluster of the composition {R ₈[Ba₆F₇₁]}. This supercluster differs from the well-known rare earth octahedral supercluster of the composition {Ba₈[R ₆F_68-69]} because its nucleus is formed not by RE cations but by an alkali earth cation, Ba. The {R ₈[Ba₆F₇₁]} supercluster has a configuration close to that of the [B₁₄F₆₄] fragment of the fluorite structure and can replace the latter isomorphously. The model of the Ba_0.75Lu_0.25F_2.25 crystals consisting of coherently intergrown isostructural microphases having different chemical compositions is characterized by the good agreement of the calculated and experimentally determined occupancies of the F^1? positions. The comparison of the Ba_0.8Yb_0.2F_2.2 (phase studied earlier) and Ba_0.75Lu_0.25F_2.25 structures demonstrates the evolution of the defect structure along the series of rare earths with the corresponding change of the sp. gr. Fm $\bar 3$ m by the sp. gr. Pm $\bar 3$ m.     

Crystal structure of tisinalite Na2(Mn,Ca)1 − x (Ti,Zr,Nb,Fe3+)[Si6O8(O,OH)10]

Crystal structure of tisinalite from the Lovozero alkaline massif (the Kola Peninsula) was established by single-crystal X-ray diffraction analysis (SYNTEX $\bar P1$ diffractometer, λMoK_α radiation, 2θ/θ scanning mode). The structure solution (SHELX97 program package, R _hkl = 0.0565, 951 independent reflections, anisotropic refinement of thermal atomic displacements) confirmed that tisinalite belongs to the lovozerite structure type (sp. gr., $\bar P1$ , a = 10.036(5) Å, c = 12.876(9) Å, Z = 3). The difference between the structure of tisinalite and the structures of the minerals of the lovozerite group established earlier consists in the nature of the occupancy of both cation and anion positions.     

Synthesis and crystal structure of new phosphate NaFe 4 2+ Fe 3 3+ [PO4]6

New sodium iron orthophosphate NaFe ₄ ²⁺ Fe ₃ ³⁺ [PO₄]₆ was synthesized by the hydrothermal method. The crystal structure (sp. gr. $P\bar 1$ ) was established by the heavy-atom method, with the exact chemical formula of the compound being unknown; R _hkl = 0.0492, R _whkl = 0.0544, S = 0.52. The new compound is analogous to iron phosphate Fe ₃ ²⁺ Fe ₄ ³⁺ [PO₄]₆ studied earlier. However, these two compounds differ in the Fe²⁺ and Fe³⁺ contents, because Na⁺ ions in the new compound are located at the centers of symmetry not occupied earlier.     

Refinement of the crystal structure of sanidine-like feldspar

The crystal structure of sanidine-like feldspar of the composition KAlSi₃O₈ from the Khibiny alkaline massif (the Kola Peninsula) has been refined (X-ray diffraction analysis; automated Syntex $P\bar 1$ diffractometer; 2θ: θ scanning technique; 2320 reflections; R _(hkl) = 0.0409; anisotropic refinement; AREN program package). The data obtained for KAlSi₃O₈ are: a = 8.615(9), b = 13.030(7), c = 7.200(5) Å, α = 89.99(5)°, β = 116.01(6)°, γ = 89.98(7)°, Z = 4, sp. gr. $C\bar 1$ . Microtwinning revealed in the crystal structure of the mineral explains the simultaneous existence of two structural-optical types in one sample—“high” and “low” sanidines.     

Anisotropy of microhardness of β-BaB2O4 single crystals

The anisotropy of microhardness of β-barium borate single crystals β-BaB₂O₄ (BBO) is studied by the sclerometry method on the (0001) basal plane, the $(10\bar 10)$ plane of the hexagonal prism, and the $(11\bar 20)$ plane of the trigonal prism. It is shown that the anisotropy observed in the crystal is determined by the directions of covalent B-O bonds. It is established that the anisotropy of microhardness correlates with the system of cleavage planes.     

Three-layer monoclinic 3M 2 polytype of muscovite revealed from oblique-texture electron diffraction patterns

The inhomogeneous (complex) polytype 3M ₂ of finely dispersed muscovite with the structure formed by layers with different parity of azimuthal orientations (561) or relative rotations $[11\bar 2]$ was identified for the first time using the oblique-texture electron diffraction patterns. The specimen had no rigorous order in layer alternation, which is reflected in the distortion of the reflection positions and intensities. It is shown that the most probable defects reduce to the replacement of the layer orientations characteristic of the 3M ₂ polytype by layer orientation characteristic of the 2M ₂ polytype. This fact indicates that, under certain conditions, the prismatic coordination of interlayer cations in micas is preferable.     

X-Ray diffraction and IR-spectroscopic studies of UO2(n-C3H7COO)2(H2O)2 and Mg(H2O)6[UO2(n-C3H7COO)3]2

Single crystals of UO₂(n-C₃H₇COO)₂(H₂O)₂ (I) and Mg(H₂O)₆[UO₂(n-C₃H₇COO)₃]₂ (II) are synthesized. Their IR-spectroscopic and X-ray diffraction studies are performed. Crystals I are monoclinic, a = 9.8124(7) Å, b = 19.2394(14) Å, c = 12.9251(11) Å, β = 122.423(1)°, space group P2₁/c, Z = 6, and R = 0.0268. Crystals II are cubic, a = 15.6935(6) Å, space group $Pa\bar 3$ , Z = 4, and R = 0.0173. The main structural units of I and II are [UO₂(C₃H₇COO)₂(H₂O)₂] molecules and [UO₂(C₃H₇COO)₃]^? anionic complexes, respectively, which belong to AB ₂ ⁰¹ M ₂ ¹ (I) and AB ₃ ⁰¹ (II) crystal chemical groups of uranyl complexes (A = UO ₂ ²⁺ , B ⁰¹ = C₃H₇COO^?, and M ¹ = H₂O). A crystal chemical analysis of UO₂ L ₂ · nH₂O compounds, where L is a carboxylate ion, is performed.