Gel growth of α and γ glycine and their characterization

The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals.     

Synthesis and crystal and molecular structure of newN-substituted γ-hydroxybutyramides

TheN-(2-phenylethyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (II) and theN-(p-methoxybenzyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (III) have been synthesized and the crystal structure ofIII has been solved. CompoundIII, C₁₆H₂₃O₅N, crystallizes in the monoclinic space groupP2₁/c witha=12.572(2),b=11.149(2),c=12.317(2) Å and=106.53(1)°. The structure was solved by direct methods, and refined by full-matrix least squares to giveR=0.040 (R _w =0.047) for 2004 intensities. The dioxolane ring has a deformed half-chair conformation.     

Structural and magnetic properties of ZnO and Zn1−xMnxO nanocrystals

Chemical precipitation of metal-ions from aqueous solution has been successfully used to produce Zn_1?xMn_xO nanocrystals, in the form of nano-powder. X-ray diffraction (XRD) measurements reveal that the as-prepared samples are single-phase materials and their lattice constant changes with the variation of Mn-concentration, which indicates the incorporation of Mn²⁺ into the hosting ZnO. These findings are corroborated by the observation of the well defined six hyperfine lines of Mn²⁺ ion in the electron paramagnetic resonance (EPR) spectra of the samples with a low Mn-concentration, and of a broad EPR line, which manifests the onset of Mn–Mn exchange interaction, in the samples with an elevated value of x.     

Synthesis of spinacine and spinacine derivatives: crystal and molecular structures of Nπ-hydroxymethyl spinacine and Nα-methyl spinaceamine

The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, N^π-hydroxymethyl-spinacine, and a spinacine derivative, N^α-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H₂O, monoclinicP2 _i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)^o. Spm(αMe)·2HCl·H₂O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)^o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl^? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl^? anions and two water molecules linked together by hydrogen bonds.     

11th Conference on Solid and Liquid Crystals—Material Science and Applications

Abstract

The eleventh conference in a series of biennial meetings was organized by Professor Jozef Zmija group from the Institute of Technical Physics WAT, Warsaw, Poland. It was supported by the State Committee of Scientific Research (KBN), the Polish chapter of the International Society for Optical Engineering (SPIE) and the Committee of Crystallography, Polish Academy of Sciences. These conferences have become more international, and this meeting, organized just outside Zakopana, in the Tatra mountains attracted more than 210 scientists, 51 from abroad.     

Synthesis, X-ray and neutron diffraction and Mössbauer studies of SrFeOx crystals

Tetragonal single crystals of the nonstoichiometric strontium ferrate with the lattice parameters a = 3.8525(3) and c = 3.8781 (3) Å have been synthesized for the first time by the method of floating-zone melting in the SrFeO_x system. The neutron diffraction patterns of the crystals showed weak additional reflections indicating the formation of the superstructure with double spacing along the [hh0] direction. The Mössbauer spectra of the crystals were obtained and measured in the temperature range 80–300 K. It was established that below the temperature T _N = 232(1) K, the crystals are in the magnetically ordered state with 3/5 of iron ions being in the trivalent state and all the remaining iron ions in the tetravalent state. This leads to the crystal composition SrFeO_2.71. The electric resistivity of the crystals equal to 100 ω cm at room temperature drastically decreases at temperatures exceeding 470 K.     

Synthesis,characterization, and mesomorphic investigation of vinyl ester-substituted chalcones and effect of lateral ‒NO2 and ‒OCH3 group

A novel homologous series of α-4-(4′-n-alkoxy cinnamoyloxy) phenyl β-2″-nitro, 3″–4″ di methoxy benzoyl ethylenes, H_2n+1CnO?C₆H₄?CH?CH?COO?C₆H₄?CO?CH?CH?C₆H₂(NO₂) (OCH₃)₂ (n = 1–8, 10, 12, 14, 16, 18) has been synthesized. All these compounds have been characterized by suitable spectroscopic techniques. C₁ homologue is nonmesogenic, while C₂ homologue shows enantiotropic nematogenic property and the rest of the homologous (C₃?C₁₈) displayed enantiotropically smectogenic plus nematogenic phase. Phase transition temperatures and textures of the LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. The mesomorphic properties of these compounds were confirmed by differential scanning calorimetry (DSC) analysis.     

Molecular and crystal structures of a tricyclic γ-lactam ketone and its Mannich base

A tricyclic -lactam ketone, 1,10a-Dihydropyrrolo[1,2]isoquinoline-3,10(2H,5H)-dione, and its corresponding Mannich base, 10a-(Dimethylaminomethyl)-1,10a-dihydropyrrolo[1,2b]isoquinoline-3,10(2H,5H)-dione hydrochloride, have been synthesized. The molecular and crystal structures of both compounds were studied by NMR-spectroscopy and X-ray crystallography. Unit cell parameters are:a=8.799(7),b=7.137(6),c=16.156(8)Å,=76.28(5)°, space groupP2₁/c forthe first compound, anda=15.343(9),b=7.490(6),c=13.465(8) Å,=110.98(3)°, space groupP2₁/c for the second. The structures were refined to discrepancy factorsR=0.068 for 1261 andR=0.047 for 2138 observed CuK data, respectively. The conversion of the tricyclic -lactam ketone to its corresponding Mannich base does not affect thecis configuration between the fused tetrahydropyridine and -lactam rings, but does result in conformational changes in both rings.     

“Bands” and “Torsads” Textures in Films and Threads of Hydroxypropyl Cellulose

The present paper deals with films and threads of a mesomorphic cholesteric polymer: the hydroxypropyl cellulose. The steady flow behaviour and the shear induced textures (observed by optical microscopy under crossed polars) of films of lyotropic solutions of this polymer have been studied. A detailed analysis of the banded structures, of either the sheared solutions or the dried films obtained by solvent evaporation, is reported. We point out the existence of transverse striated patterns—“torsads”—superposed on the main banded structures, which are associated with the rewinding of the cholesteric structure following the cessation of the shear stress. The torsads, also observed in some threads, originate from the same relaxation phenomena and are discussed in the last part of the paper.     

Enthalpy relaxation of hyperquenched glasses and its possible link to α- and β-relaxations

The enthalpy relaxation of glass fibers of different chemical compositions and thereby of different fragility steepness indices is investigated by means of the hyperquenching–annealing–DSC scanning method. Results show that the pattern of the enthalpy relaxation spectra of the glass depends on its composition, and, hence, on its fragility steepness index. The present paper suggests that the enthalpy relaxation pattern could be linked to the α- and β-relaxations that are normally used to describe relaxation spectra of supercooled liquids near the glass transition. Three observations are shown to support the suggestion.     

New Metal–Organic Framework Solids Built from Barium and Isoelectronic Chelidamic and Chelidonic Acids

Abstract  

Two new Ba(II) metal–organic framework solids bearing the chelidamate [Ba₂(C₇H₃NO₅)₂(μ-H₂O)(H₂O)₆]·2H₂O (1) and chelidonate [Ba(C₇H₂O₆)(H₂O)] (2) ligands were synthesized and characterized by IR, elemental, thermal, photoluminescent and X-ray diffraction analyses. In complex 1 the chelidamate dianion exists in two tautomeric forms, in which the enol form exhibits unprecedented (К¹, К¹) (К¹) (К², К², μ₂, μ₂)-μ₇ heptadentate coordination while the keto form with (К¹, К¹)(К²)-μ₄ tetradentate mode. It is a 2D polymer in which the first and second dimensions are satisfied by carboxylate oxygens while the third is by the combination of hydrogen bonds and π–π stacking of aromatic rings. There are two independent barium ions (Ba1, Ba2) in complex 1 that are nine coordinated, but their coordination environment is different. Complex 2 is a 3D polymer and the organic linker, 4-oxo-pyran-2,6-dicarboxylate (chelidonate) anion exhibits denticity as seven with barium having the similar nine coordination.     

Syntheses and Crystal Structures of Two New Cadmium(II) and Nickel(II) Complexes with 1,4-Phenylenediacetate and 2,2′-Bipyridyl-Like Ligands

Abstract  

Two new complexes, namely [Cd(PDA)_0.5(2,2′-bpy)Cl](H₂PDA) (1) and [Ni(PDA)(phen)(H₂O)]₂ (2) (H₂PDA = 1,4-phenylenediacetic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized by elemental analysis, IR spectra and X-ray crystal diffraction. Single-crystal X-ray diffraction analysis shows that complex 1 crystallizes in the triclinic space group P-1 with unit cell dimensions a = 8.760 (4) ?, b = 11.190 (5) ?, c = 13.917 (7) ?, α = 110.383 (5)°, β = 101.736 (5)°, γ = 100.612 (5)°, V = 1202.8 (10) ?³, Z = 2, R ₁ = 0.0314 and wR ₂ = 0.0898. Complex 2 crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 9.911 (3) ?, b = 17.924 (6) ?, c = 10.638 (4) ?, β = 94.998 (5)°, V = 1882.7 (11) ?³, Z = 2, R ₁ = 0.0397 and wR ₂ = 0.1150. In complex 1, Cd(II) ions are alternately bridged by PDA ligands and chloride ions into 1D chains and the PDA ligands display trans-configuration. Complex 2 is a dimer and two Ni(II) ions are linked by two PDA ligands with cis-configuration, resulting in a cyclic structure. In spite of these differences, both in complexes 1 and 2 there are π–π stacking interactions and hydrogen bonding to make them 3D supramolecular frameworks.     

Hydrogen bonds and π–π stacking interaction in 4′, 7-dimethoxylisoflavone and 4′,7-diacetyl-O-isoflavone

4′,7-dimethoxylisoflavone, C₁₇H₁₄O₄, (I), is linked into a supramolecular structure by a variety of weak but direction-specific intermolecular forces, the molecules are linked into chains through C–H⋅sO hydrogen bonds, these chains are further linked by face-to-face (F-tape) π–π stacking into a one-dimensional bi-chain, another type π–π stacking, edge-to-face (T-tape), assemble the bi-chain into framework together with C–H⋅sO hydrogen bonds. 4′,7-diacetyl-O-isoflavone, C₁₉H₁₅O₆, (II), shows some discrepancies with I and the molecules are assembled into framework all by C–H⋅sO hydrogen bonds. The molecules are linked into centrosymmetric dimers built from classic R₂² (8) rings by pairs of C–H⋅sO hydrogen bonds, the dimers are linked into (011) sheets by combination of the R₂² (8) ring and C–H⋅sO hydrogen bonds, another C–H⋅sO hydrogen bond assemble the sheets into three-dimensional network.     

Multilayer planar structures prepared from chalcogenide thin films of As–Se and Ge–Se systems and polymer thin films using thermal evaporation and spin-coating techniques

We report the preparation of multilayers based on polyamide–imide polymer and As–Se or Ge–Se chalcogenide thin films. Chalcogenide films of As–Se and Ge–Se systems were deposited using a thermal evaporation method periodically alternating with spin-coated Polyamide–imide films. Fifteen layers of PAI + As–Se system and nineteen layers of PAI + Ge–Se system were coated. Optical properties of prepared multilayers have been established using UV–vis–NIR and Ellipsometric spectroscopy. Both, PAI + As–Se and PAI + Ge–Se multilayer systems, exhibited the high-reflection bands centered around 830 nm and 1350 nm, respectively. The shift of the band position of PAI + Ge–Se multilayers to lower energies was caused by higher thickness of Ge–Se films. The bandwidth of reflection band of 8 PAI + 7 As–Se multilayer was ～90 nm while bandwidth of PAI + Ge–Se system decreased to ～70 nm because Ge–Se films have 0.1 lower refractive index against As–Se films. Design of 1D-photonic crystals based on alternating chalcogenide and polymer films is a new opportunity for application of chalcogenide thin films as optical materials for near-infrared region.     

Spectroscopic properties and ab initio calculations on the structure of erbium–zinc-borate glasses and glass ceramics

Glasses in the (Er₂O₃)_x·(B₂O₃)_(60 ? x)·(ZnO)₄₀ system (0 ≤ x ≤ 15 mol%) have been prepared by the melt quenching technique. X-ray diffraction, FTIR spectroscopy, UV-VIS spectroscopy and ab initio calculations studies have been employed to study the role of Er₂O₃ content on the structure of the investigated glass system.X-ray diffraction and infrared spectra of the glasses reveal that the B–O–B bonds may be broken with the creation of new non-bridging oxygen ions facilitating the formation of Er–O–B linkages. The excess of oxygen can be accommodated in the network by the conversion of sp² planar [BO₃] units to the more stable sp³ [BO₄] tetrahedral structural units. The linkages of the [BO₄] structural units can polymerize in [B₃O₉]^? 9 cyclic trimeric ions which will produce the ErBO₃ crystalline phase. An increase of the efficiency corresponding to the ⁴I_15/2 state to ⁴I_11/2 state (4f–4f) transitions of Er^+ 3 ions was observed for the erbium oxide richest glasses.Ab initio calculations on the structure of the matrix network show the thermodynamic instability of the [BO₄], [ZnO₄] and [Zn₄O] structural units. Formation of three-coordination oxygens was necessary to compensate shortage of oxygens from zinc ions.     

Silica Λ-shape wedge arrays fabrication and interspace tuning via hot embossing and sol–gel replication

New-type silica Λ-shape wedge arrays (SWAs) were fabricated by a combined process of template fabrication, hot embossing and sol–gel replication. Using silica needle arrays (SNAs) as template, the configuration of Λ-shape was transferred from SNAs to PMMA/PC molds by hot-pressing process. Then they were casted to form silica Λ-shape wedge arrays by sol–gel process. Using this procedure, high quality silica Λ-shape wedge arrays can be obtained with designed sizes and shapes over a large area. The taper height and interspace of SWAs can be tuned by the imprint depth during the hot-embossing process. This technology provides a cost-effective method to fabricate Λ-shape silica wedges. By changing the primal template, other patterned silica substrate can also be fabricated, such as grating, pillar and spherical structures. These silica based microstructure can find many applications in semiconductor devices, solar cells and optics etc.     

Precision X-ray diffraction and Mössbauer studies and computer simulation of the structure and properties of malayaite CaSnOSiO<Subscript>4</Subscript>

The structure and some physical properties of malayaite CaSnOSiO₄ have been studied by the precision X-ray diffraction, Mössbauer spectroscopy, and computer simulation of the structure. The unit-cell parameters a = 7.152(2) Å, b = 8.888(2) Å, c = 6.667(2) Å, β = 113.37(2)°, V = 389.0(3) ų, and μr = 0.68 are refined on a synthetic impurity-free sample. The distribution of the deformation electron density is analyzed in the basic fragments of the crystal structure forming an anionic framework. The constructed potentials of pair and three-particle interaction reproduced quite well the elastic, dielectric, and energy characteristics and allowed us to predict their numerical values, which are in good agreement with the limited available experimental data.     

Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid

Abstract  The Ni(II) complex, [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O, H₂biim being 2,2′-biimidazole, PABA being 4-aminobenzoic acid has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P − 1 with unit cell parameters a = 8.3920(9) ?, b = 9.8436(11) ?, c = 9.8874(11) ?, α = 94.862(2)°, β = 109.142(2)°, γ = 90.992(2)°, V = 767.95(15) ?³ and Z = 1. The molecules of the complex in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure. Index Abstract  Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid Yanping Li and Pin Yang* The molecules of the title complex [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure.