Dielectric relaxation of liquid crystal molecules in anisotropic confinements

Abstract

The dielectric relaxation of the liquid crystal 4-n-pentyl-4′-cyanobiphenyl (K15) in the presence of an anisotropic network has been studied. Anisotropic networks containing K15 molecules were prepared by in situ polymerisation of liquid-crystalline diacrylate molecules in a mixture containing K15. By changing the network concentration, the effect of the network molecules on the behaviour of the K15 molecules, which were not chemically attached to the network, was investigated. With increasing network concentration it was found that the mean relaxation times of K15 molecules shifted to lower temperatures and that their distribution became broader. The activation energy associated with the relaxation, however, remained almost constant before showing some increase at high network concentrations.     

Thiocarbamide derivatives of europium,holmium, and erbium iodides: Synthesis and structures

Data on the synthesis, IR spectra, and X-ray diffraction analysis of the thiocarbamide complexes of europium, holmium, and erbium iodides, [Ln(H₂O)₉]I₃ · 2CS(NH₂)₂ (Ln = Eu (I), Ho(II), Er (III)), are presented. The crystal structures of the complexes contain nonaaqualanthanide cations (the polyhedron shape is a monocapped tetragonal antiprism), outer-sphere thiocarbamide molecules, and uncoordinated iodide ions. The thiocarbamide molecules form hydrogen bonds with the aqua cations and join them into continuous layers or network ensembles. The thiocarbamide molecules are disordered in the crystal structures of complexes II and III.     

Investigation of the crystal structure of two amphiphilic diols

Abstract

The crystal and molecular structures of (R)-4′-(2,3-dihydroxypropyloxy)-4-cyanobiphenyl, 1 and 4′-(cis-cis-3,5-dihydroxycyclohexyloxy)-4-cyanobiphenyl, 5 have been determined. The packing of compound 1 occurs in sheets, with a dense hydrogen bonding network within the layer of one sheet and to the next sheet, whereby the cyano groups are incorporated into the hydrogen bonding network. The hydrogen bonding scheme of compound 5 involves a water molecule; there is some disorder with regard to the hydrogen atoms bound to the water molecules.     

单核Zn(Ⅱ)/Ni(Ⅱ)含氮配体配合物的合成、晶体结构及性质

合成了2个新的配合物[Zn(BPP)2(H2O)4](2,6-NDS)·0.5H2O(1)和[Ni(phen)2(H2O)2](A-2,5-DSA)·3H2O(2)(2,6-NDS=2,6-萘二磺酸根,A-2,5-DSA=苯氨-2,5-二磺酸根,BPP=1,3-二(4-吡啶基)丙烷,phen=1,10-邻菲咯啉),用X-射线单晶衍射结构分析方法测定了配合物的晶体结构。配合物1是单核分子,Zn2+离子与2个1,3-二(4-吡啶基)丙烷的2个N原子及4个水分子配位,形成单核配位阳离子。相邻配位阳离子通过配位水分子与氮原子的氢键作用联接成一维双螺旋阳离子链。双螺旋阳离子链与未配位的2,6-萘二磺酸根阴离子通过氢键作用形成二维超分子网。配合物2是单核分子,Ni2+离子与2个1,10-邻菲咯啉分子中的4个N原子及2个水分子配位,形成单核配位阳离子。配位阳离子与游离的水分子及苯氨-2,5-二磺酸根阴离子通过氢键作用构筑成二维超分子网。     

Structure of D-Fructosamine Hydrochloride and D-Fructosamine Hydroacetate

D-Fructosamine derivatives are key intermediates of the early Maillard reaction and have been a subject of numerous studies in food and health sciences due to their implication in the nutritional and organoleptic quality of foods, as well as to complications in diabetes and renal disease. We report the crystal structure analyses of 1-deoxy-β -D-fructopyranos-1-ylamine hydrochloride (1) and -hydroacetate (2) salts. The carbohydrate rings adopt the normal ²C₅ pyranose chair conformation in 1 and 2. Bond lengths and valence angles in 1 and 2 compare well with the average values from related pyranose structures. There are two conformationally nonequivalent molecules in the asymmetric unit in 1. All hydroxyl and ring oxygen atoms, ammonium groups, and chloride ions in 1 are involved in an extensive three-dimensional hydrogen bonding network. The hydrogen bonding network in 2 is formed by one type of infinite chain with attached antidromic cycles.     

A Noncongeneric Model for Predicting Toxicity of Organic Molecules to Vibrio Fischeri

Abstract

A general Quantitative Structure-Activity Relationship (QSAR) model on Vibrio fischeri (Microtox^? test) was derived using the autocorrelation method for describing the molecules and a neural network as statistical tool. From a training set of 1068 organic chemicals described by means of four different autocorrelation vectors, it was possible to obtain valuable models but presenting some large outliers. Addition of the time of exposure as variable allowed us to derive a more powerful model from 2795 toxicity results. The predictive power of this 36/26/1 neural network model was tested on an external testing set of 385 toxicity data and compared with the performances of linear models designed for polar narcotic amines and for weak acid respiratory uncouplers.     

以吡啶-2,5-二羧酸或噻吩-2,5-二羧酸为配体的过渡金属配合物的合成、晶体结构及性质

以吡啶-2,5-二羧酸(2,5-pyridinedicarboxylic acid,H_2L_1)、噻吩-2,5-二羧酸(Thiophene 2,5-dicarboxylic acid,H_2L_2)为主要配体,4,4′-联吡啶(4,4′-bipy)、菲咯啉(phen)为辅助配体,采用溶剂热法成功合成了3个过渡金属配合物:[Co_2(L_1)_2(bipy)(H_2O)_6]·bipy·H_2O (1)、[Cu(L_2)_2(bipy)_2]n(2)、[Ni_2(L_2)(phen)_2(H_2O)_4](3),并利用X射线单晶衍射法、红外光谱(IR)、荧光光谱(FL)和热重分析(TG/DTG)等测试手段对其进行了表征。单晶结构分析表明:配合物1、配合物2为P1空间群,配合物3为P2/n空间群;配合物1和配合物3为零维双核小分子结构,配合物2为二维层状结构。     

Development of a new sensor material based on crystalline colloidal arrays embedded into polymer network

This study reports the development of a novel sensing material that reports on analyte concentrations via diffraction of visible light from polymerized crystalline colloidal arrays (PCCA). The PCCA contains periodic crystalline colloidal array (CCA) of spherical polystyrene colloids. This new method permanently locks the order of the CCA by embedding the CCA into a polymer network. These materials are mostly used in the development of novel materials which are basically called sensors for metal ions and all kinds of organic molecules. The polymer around the crystalline colloid can be functionalized with some recognition molecule, making these materials useful as optical sensors. We developed a sensor, utilizing crown ether, 2-aminomethyl-18-crown-6 (2A18C6) as the recognition agent, that detects K⁺ in the concentration range from 5 to 160 ppm.     

以3, 5-二甲基-1-羧甲基-4-吡唑甲酸为配体的两个锌的配合物的合成、晶体结构和荧光性能

以3, 5-二甲基-1-羧甲基-4-吡唑甲酸和4, 4'-联吡啶为配体, 合成了1个单核锌(II)配合物[Zn(4,4'-bpy)(Hcmdpca)₂(H₂O)₃]·2H₂O (1)和1个锌(II)的一维配位聚合物[Zn(4, 4'-bpy)(Hcmdpca)₂(H₂O)]·3H₂O (2)(H₂cmdpca=3, 5-二甲基-1-羧甲基-4-吡唑甲酸;4, 4'-bpy=4, 4'-联吡啶), 并用元素分析、红外光谱、X-射线单晶衍射结构分析、热重分析等对其进行了表征。配合物1和2都属于单斜晶系, 空间群为P2₁/c。配合物1的锌离子都位于一个畸变的八面体构型中。配合物1中的独立结构单元间通过分子间氢键作用构成一个三维的超分子结构。而在2中, 锌离子位于一个畸变的四方锥构型中, 每个4, 4'-联吡啶分子桥联2个相邻的 锌(II)离子, 形成一个一维链;这些一维链和水分子通过分子间氢键进一步形成一个三维的结构。此外还考察了1和2的热稳定性和固体荧光性质。     

Synthesis,crystal structures,and properties of two novel compounds containing triphosphonate groups

Two novel phosphonate compounds (H₂L)·Hphen (1) and [Ca(HL)(H₂O)]_n·3.5nH₂O (2) (L = N(CH₂PO₃H)₃^3?) were synthesized under hydrothermal conditions. Compound 1 features a chain structure in the ac plane, where HL^2? anions are interconnected through sharing hydrogen ions to form a 1D zigzag type. Compound 2 features a layered structure in the ab plane, which has inorganic calcium cores with the organic part of the phosphonate anions being encircling the cores through coordination actions. The free water molecules can form hydrogen bonds with the coordinated water molecules and phosphonate oxygen atoms, which are able to link the adjacent layers to generate a 3D network structure. In addition, the thermal stability and photoluminescence properties were also studied.     

Self-assembled tetrameric H2O clusters in the crystal lattice of [Cu(μ2-OH){Ph2P(O)NP(O)Ph2-κ1O,O′}(1,10-phen-κ2N,N′)]2·2H2O

Abstract

The synthesis and characterization of the dinuclear Cu(II) complex [Cu(μ²-OH){Ph₂P(O)NP(O)Ph₂-κ¹O,O′}(1,10-phen-κ²N,N′)]₂·2H₂O (1), 1,10-phen?=?1,10-phenanthroline, is described. X-ray crystallographic studies reveal that the Cu(II) centers of 1 are bridged by two OH^? groups and are coordinated by the (O,O)?= Ph₂P(O)NP(O)Ph₂^? ligand in a monodentate fashion, unprecedented for Cu(II). The crystal lattice of 1 also contains H₂O molecules, which are involved in the formation of a hydrogen bonding network with bridging OH^? groups and noncoordinated O atoms of the (O,O) ligand. These H₂O molecules are arranged in the crystal lattice of 1 as tetrameric clusters. The packing of molecules in the structure of 1 was investigated by Hirshfeld Surface analysis.     

PREPARATION AND CRYSTAL STRUCTURE OF THE HOST-GUEST TYPE COMPLEX OF TRIS(BIPYRIDINE)NICKEL(II)-TETRAKIS(CYANO) NICKELLATE (II))-HEXAHYDRATE-HEMI (BIPYRIDINE)

Abstract

The title complex is built up of [Ni(bpy)₃]²⁺ cations, [Ni(CN)₄]^2? anions and non-coordinated bpy and water molecules. The water molecules along with one of the two crystallographically independent tetracyanonickellate anions form layers, in which H-bonds (HB's) of the types O-H ‥ O and O-H ‥ N are important. The remaining tetracyanonickellate anions bound by H-bonds to water molecules in the layers are placed approximately perpendicular to the layers making interconnection between them. So by HBs a 3D network is formed (hydrophilic host part of the structure). The cations and non-coordinated bpy molecules (hydrophobic guest part of the structure) are placed in cavities formed by HBs. The Ni-N distances in the cation are within the range 2.078(3)-2.100(3) Å and the Ni-C distances in the anion are within the range 1.854(5)-1.873(4) Å.     

Crystal and Molecular Structure of (trans-3,4-Diamino-2,2,6,6-tetramethylpiperidine-1-oxyl-N3, N4)(oxalato-O,O′)platinum(II) Dihydrate

The crystal and molecular structure of (trans-3,4-diamino-2,2,6,6-tetramethylpiperidine-1-oxyl-N ³, N ⁴)(oxalato-O,O′)platinum(II) dihydrate was studied by single crystal X-ray diffraction. The crystals belong to the monoclinic system; a 8.261, b 13.129, c 15.224 Å; β 104.29°, Z 4, space group P2₁/n. The structure was solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R 0.026 for all the 3660 measured unique reflections. The structure consists of individual mononuclear bischelate molecules containing two different bidentate ligands. The Pt²⁺ coordination is distorted square-planar. The complex molecules and water molecules in the crystal of I are linked by hydrogen bonds forming an infinite 3D network. __________ Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 11, 2005, pp. 1893–1897. Original Russian Text Copyright ? 2005 by Chekhlov.     

The Crystal Structures of Pyrazine-2,6-Dicarboxylic Acid DihydRAte and Hexaaquamagnesium(II) Pyrazine-2,6-Dicarboxylate

The crystals of the pyrazine-2,6-dicarboxylic acid dihydrate [C 4 H 2 N 2 (COOH) 2 ]·2H 2 O or H 2 (2,6-PZDC)] crystallize in the monoclinic system, space group C2/m. Their structure is composed of planar layers in which the acid and the water molecules interact via a network of hydrogen bonds. The layers are also hydrogen bonded. Hexaaquamagnesium(II) pyrazine-2,6-dicarboxylate [Mg(H 2 O) 6 ] 2+ [C 4 H 2 N 2 (COO) 2 ] 2 m crystallizes in the monoclinic system, space group P2 1 / n . The magnesium(II) cation is surrounded by six water molecules located at the apices of an almost regular octahedron with the mean Mg-O bond distance of 2.068 Å. The 2,6-PZDC anions are planar and are acceptors in a network of hydrogen bonds donated by the coordinated water molecules.     

Functional self-assembly of hydrogen-bonded 3D coordination networks constructed from 1,2,4,5-benzenetetracarboxylic acid

Hydrothermal synthesis, characterization (IR, TG/DTA, element analysis, inductively coupled plasma (ICP)) and single-crystal X-ray structures of H₄Btec hydrate and its two cobalt complexes, colorless [H₄Btec · 2H₂O] _n (I), pink [Co(H₂O)₆(H₂Btec)] _n (II), and nacarat {[Co(H₂O)₃(H₂Btec)(Phen)] · H₂O} _n (III) (H₄Btec = 1,2,4,5-benzenetetracarboxylic acid, Phen = 1,10-phenanthroline) have been solved. The results showed that I forms a 3D O-H⋯O hydrogen-bonded network generated from H₄Btec and water molecules, II presents a 3D network constructed by mononuclear [Co(H₂O)₆]²⁺ cations and H₂Btec²⁻ dianions through extensive hydrogen-bonding interactions, and III gives rise to a pseudo-octahedral coordination geometry. Extensive hydrogen-bonding interactions have significant effects in configuring a 3D network constructed by mononuclear [Co(H₂Btec)(Phen)(H₂O)₃] neutral molecules and a water molecules. The article was submitted by the authors in English.     

Syntheses and crystal structures of cobalt(II) and zinc(II) complexes with 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate

Abstract Sodium 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate (1) is synthesized by the sulfonation of 6-hydroxybiochanin A and its structure is characterized by elemental analysis, ¹H-NMR, and IR spectroscopy. It is assembled with cobalt(II) or zinc(II), hexaquacobalt(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (2) and hexaquazinc(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (3) are obtained and characterized by IR spectroscopy. Simultaneously, their three-dimensional structures are determined by single-crystal X-ray analysis. It turns out that 2 and 3 are isomorphous and crystallize in the triclinic crystal system, space group P-1. Hydrophilic regions are defined by O–H···O hydrogen bonds involving the coordinated water molecules, the included water molecules, and sulfonate groups. Aromatic π...π stacking interactions assemble the isoflavone skeletons into columns and these columns formed hydrophobic regions. The sulfonate group is an important bridge as a structural link between the hydrophilic regions and the hydrophobic regions. Hydrogen bonds, π...π stacking interactions and the electrostatic interactions assemble 2 and 3 into three-dimensional network structures. Graphical abstract Sodium 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate (1) is synthesized and assembled with cobalt(II) or zinc(II). Hexaquacobalt(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (2) and hexaquazinc(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (3) are obtained and determined by single-crystal X-ray analysis. It turns out that 2 and 3 are isomorphous and assembled into three-dimensional network structures, characterized by hydrophilic regions defined by hydrogen bonds involving the coordinated water molecules, the included water molecules, and the sulfonate groups and by hydrophobic columns, formed by the isoflavone skeletons, interacting through π...π stacking interactions.