Crystal structure of the Na-, Ca-, Be-cordierite and crystallochemical regularities in the cordierite—sekaninaite series

The crystal structure of the beryllium-rich cordierite [(Na_0.28Ca_0.19)(H₂O)_0.92](Mg_1.86Fe _0.14 ^22? ) · { Al_3.39Be_0.61Si₅O₁₈} was established by X-ray diffraction analysis (IPDS Stoe diffractometer, λMoKα radiation, graphite monochromator, 2θ_max = 65°, R = 0.0186 for 1378 reflections): a = 16.850(3), b = 9.729(2), and c = 9.298(2) Å; V = 1524.3(4) ų, sp. gr. Cccm, Z = 4, and ρ_calcd = 2.655 g/cm³. The numbers of Mg and Fe atoms isomorphously occupying the octahedral positions, Al and Be atoms in tetrahedra, and Na and Ca atoms and H₂O molecules in the framework cavities are refined. The hydrogen atom is localized and its coordinates and thermal displacement parameters are refined. Based on the comparative crystallochemical analysis of cordierites from different locations and origins, the regularities relating the unit-cell parameters b and c and the distortion index to the features of the chemical composition of the minerals under study are shown.     

Preparation,crystallization behavior and magnetic properties of nanoparticles magnetic glass–ceramics in the systems Fe2O3 CoO MnO2, Fe2O3 NiO MoO3 and Fe2O3 CoO V2O5

Ferrimagnetic glass–ceramics were prepared in the systems Fe₂O₃ CoO MnO₂ (S1), Fe₂O₃ NiO MoO₃ (S2) and Fe₂O₃ CoO V₂O₅ (S3). Small amount of H₃BO₄ was added to make the melting process easier. The samples were characterized using DTA, XRD, TEM and EDX. Sequence of crystallization was studied by applying heat-treatment at 800 and 1000 °C for 4 h. CoFe₂O₄ with crystallite sizes of ≈ 14–20 nm was successfully prepared beside FeCoOBO₃ and Co₃BO₅ in S1. NiMoO₄, (FeNi₂)O₂(BO₃) and NiO with crystallite size ≈ 56–79 nm were crystallized in S2. CoFe₂O₄, FeCoOBO₃ and Co₃BO₅ with crystallite size ≈ 6–8 nm were crystallized in S3. Magnetic hysteresis cycles were analyzed with a maximum applied field of 20 kOe at room temperature. From the obtained hysteresis loops Ms records higher values for S1 and S3 and lower value for S2, while coercivity reach maximum for S2. The variable, magnetic, data range gives a wide range for different applications.     

Oxygen potentials,stoichiometry, superconducting,and magnetic properties in the Y?Ba?Cu?O system

The relationship between stoichiometry in YBa₂Cu₃O_x and oxygen potential was investigated by barometry and compared with in-situ X-ray diffraction experiments between 300 and 1000 °C (6 < x < 7). The physical properties are influenced even by small deviations in x. Y₂BaCuO₅ was included in the investigations and found to be antiferromagnetic with T_N ≈ 30 K.     

Na0.5Pb2[B5O9]Cl(OH)0.5, a new polar variety of hilgardite containing Na+ cations in the cavities of the framework. The OD-family of the 5: 2Δ 3⧄ pentaborates: Hilgardites, heidornite, probertite, and ulexite

A new orthorhombic polar variety of Pb-hilgardite containing Na⁺ and HOCl^2? ions in the cavities of the framework has been prepared by hydrothermal synthesis. A correlation between the structural features and nonlinear-optical properties of the crystals is discussed. Similar to the hexaborate group, pentaborates with different degrees of condensation of the boron—oxygen radical are characterized by close structural similarity, which is described within the _OD theory with distinguishing structural units (blocks or modules) of different dimensionality—bricks, rods, and layers. Consideration of the variants of their connection allows us to describe the diversity of the pentaborate family including hypothetical structures.     

Crystal structures of strontium and barium ethylenediaminetetraacetato cobaltates(III), Sr[CoEdta]2·9H2O and Ba[CoEdta]2·8H2O: Comparison of the structures of complexes in the series M’[CoEdta]2·nH2O (M’ = Mg, Ca, Sr, Ba; n = 7–10)

Cobalt(III) complexes, namely, Sr[CoEdta]₂·9H₂O (I) and Ba[CoEdta]₂·8H₂O (II) (where Edta ^4- is the ethylenediaminetetraacetate ion), are synthesized. The crystal structures of these compounds are determined using X-ray diffraction. Crystals of compound I are triclinic, a = 6.514(1) Å, b = 11.410(2) Å, c = 12.317(2) Å, α = 67.87(1)°, β = 88.73(2)°, γ = 84.22(2)°, V = 843.63(3) ų, Z = 1, space group P1, and R = 0.0295 for 4130 reflections with I > 2σ(I). Crystals of compound II are monoclinic, a = 6.543(2) Å, b = 12.895(3) Å, c = 19.489(4) Å, β = 95.24(3)°, V = 1637.5(5) ų, Z = 2, space group P2₁, and R = 0.050 for 3016 reflections with |F| > 3σ(|F|). The structures of compounds I and II are compared with those of the previously studied complexes Mg[CoEdta]₂·10H₂O (III) and Ca[CoEdta]₂·7H₂O (IV). The crystal structure of the cobalt(III) complex with the strontium cation (I) is topologically similar to the crystal structure of cobalt(III) complex with the calcium cation (IV). The former structure is built up of the two symmetrically independent homochiral anionic complexes [CoEdta]^? (A _I and B _I), the aqua cations [Sr(H₂O)₈]²⁺, and the molecules of crystalization water w _cr. The structure of compound II involves two independent anions [CoEdta]^? (A _II and B _II) with different chiralities (i.e., they are kryptoracemates). The A _II anions are linked via the barium cations into {Ba(H₂O)₇[CoEdta]} _1∞ ⁺ chain agglomerates due to the incorporation of two terminal oxygen atoms O_u of the anions neighboring in the chain into the coordination sphere of the barium atom. All four structures (I–IV) contain stacks composed of the [CoEdta]^? homochiral anions forming layers aligned parallel to the (001) plane. The aqua cations [Sr(H₂O)₈]²⁺, [Mg(H₂O)₆]²⁺, and [Ca(H₂O)₇]²⁺ or the partially hydrated barium cations [Ba(H₂O)₇(O_u)₂]²⁺ (in structure II), as well as water molecules w _cr, are located between the anion layers. The octahedral environment of the cobalt(III) atoms consists of donor atoms (2N and 4O) of the Edta ^4? ligand. The Co-N bonds in the A _I, B _I, A _II, and B _II anions [the mean bond lengths are 1.927(4), 1.921(4), 1.910(6), and 1.921(6) Å, respectively] are considerably longer than the Co-O bonds [the mean bond lengths are 1.908(5), 1.902(5), 1.904(6), and 1.908(6) Å, respectively]. The mean distances Sr-O_w and Ba-O_w in the strontium and barium polyhedra are 2.609(4) and 2.834(8) Å, respectively. The mean distance Ba-O_u is 2.814(7) Å.     

Intramolecular N−H...O hydrogen bonding,quinoid effect,and partial π-electron delocalization in N-aryl Schiff bases of 2-hydroxy-1-naphthaldehyde: the crystal structures of planar N-(α-naphthyl)- and N-(β-naphthyl)-2-oxy-1-naphthaldimine

The structures of N-(-naphthyl)-2-oxy-1-naphthaldimine1 and N-(-naphthyl)-2-oxy-1-naphthaldimine2 have been investigated by X-ray analysis and by spectroscopic methods. Crystals of1 are monoclinic, space groupPn, with cell dimensionsa=10.823(3),b=5.826(2),c=11.899 (3) Å, and =99.66(3)°. Compound2 crystallizes in the orthorhombic space groupPca2₁ witha=17.564(3),b=6.314(2), andc=13.663(4) Å. The IR spectra exhibited neither N–H nor O–H stretching frequencies. The existence of theintramolecular hydrogen bonding of N–H...O type was predicted by spectroscopic experiment but unequivocally established by diffraction experiment in both cases1 and2. The molecules1 and2 are significantly planar with considerable quinoid effect at the 2-oxy-naphthaldimine moiety. Although essentially planar, both molecules1 and2 show the delocalization of -electrons only in the central part of the molecules including C=N imino group with pendent ring carbon atoms.Intermolecular attractions in the crystals belong to weak van der Waals interactions-between discrete planar molecules spatially arranged into the expectedherringbone motif in the solid state.     

Synthesis and supramolecular interactions involved in the crystal structure of (2,4,10,12-tetrabromo-6,7,14,15-tetrahydro-6, 14-thiacycloocta[1,2-b:5,6-b’]diquinoline)2·(1,1,2,2-tetrachloroethane) inclusion compound

The tetrahalo aryl inclusion host 2,4,10,12-tetrabromo-6,7,14,15-tetrahydro-6,14-thiacycloocta[1,2-b:5,6-b’]diquinoline 3 was re-synthesized to explore its ability to trap toxic polychlorinated hydrocarbons such as 1,1,2,2-tetrachloroethane (TCE) in the form of host–guest compound. Host 3 crystallizes from a fresh sample of TCE to form an inclusion compound of the formula (3)₂·(TCE) in triclinic system, space group P-1, with a = 7.7732(16) Å, b = 10.739(2) Å, c = 14.816(3) Å, α = 97.329(4)°, β = 98.619(4)°, γ = 103.359(4)°, V = 1172.7(4) ų, and Z = 2. The X-ray crystal structure of the (3)₂·(1,1,2,2-TCE) is described and analyzed in terms of crystal engineering and supramolecular chemistry. The hosts assemble by means of different types of packing motifs. The included TCE molecules are enclosed within host molecular pens. Novel halogen···halogen intermolecular interactions as well as other non-covalent intermolecular interactions involved in the crystal structure are presented and proved to play an important role in linking these host–host, host–guest, and guest–guest building blocks.     

Square-wave voltammetry and impedance spectroscopy in tin doped melts with the compositions xNa2O · 15Al2O3 · (85 − x)SiO2 (x = 8.5, 11 and 16)

Glasses with the base compositions xNa₂O · 15Al₂O₃ · (85 ? x)SiO₂ (x = 8.5, 11 and 16) doped with 0.5 mol% SnO₂ were investigated by both square-wave voltammetry and impedance spectroscopy in the temperature range from 1300 to 1600 °C. Each recorded square-wave voltammogram exhibits a well pronounced peak attributed to the Sn²⁺/Sn⁴⁺-redox pair. Impedance spectra were measured in a frequency range from 0.1 to 10⁵ s^?1 as a function of the superimposed dc-potential and were simulated using an equivalent circuit taking into account the resistivity of the melt, the electrochemical double layer, a resistor attributed to a kinetically hindered electron transfer and a Warburg parameter which accounts for the diffusion process of Sn⁴⁺ and Sn²⁺ to and from the electrode. Additionally, two impedance elements, a resistor and a capacitance both attributed to adsorption processes were necessary to fit the impedance spectra.     

Unclassical hydrogen bonds of C—H⋅<Emphasis Type="Italic">s</Emphasis>O and C—H⋅<Emphasis Type="Italic">s</Emphasis>N in the crystals of 2-amino-3-cyano-4-(3,4-dichlorophenyl)-5-oxo-1,4,5,6-tetrahydro-4H-pyrano[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine

The 2-amino-3-cyano-4-(3,4-dichlorophenyl)-5-oxo-1,4,5,6-tetrahydro-4H-pyrano[2,3-d] pyrimidine (1, C₁₇H₁₅Cl₂N₅O₃) was synthesized and characterized by IR,¹H NMR and elemental analysis. The molecular structure of1 was further studied by using X-ray crystallography. The crystals of compound1 are triclinic, space groupP-1,a = 6.0090(4) Å,b = 10.4056(7) Å,c = 15.6021(11) Å, α = 70.983(4), β = 84.056(6), γ = 84.611(6),Z = 2,V = 915.47(11) ų. Two types of unclassical hydrogen bonds C–H?sO and C–H?sN were presented in the crystals. In addition, there were classical hydrogen bonds in the crystal structure.