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1.
D. Joachimi G. Latterman M. Schellhorn C. Tschierske P. Zugenmaier 《Liquid crystals》1995,18(2):303-307
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. 相似文献
2.
《Journal of Coordination Chemistry》2012,65(23):4224-4241
Six transition metal coordination compounds with H2mand and different N-donor ligands, [Co(Hmand)2(2,2′-bipy)]·H2O (1), [Ni(Hmand)2(2,2′-bipy)]·H2O (2), [Ni(Hmand)2(bpe)] (3), [Zn(Hmand)2(2,4′-bipy)(H2O)]·2H2O (4), [Zn(Hmand)(bpe)(H2O)]n[(ClO4)]n·nH2O (5), and [Zn(Hmand)(4,4′-bipy)(H2O)]n[(ClO4)]n (6), were synthesized under different conditions (H2mand = (S)-(+)-mandelic acid, bpe = 1,2-di(4-pyridyl)ethane, 4,4′-bipy = 4,4′-bipyridine, 2,4′-bipy = 2,4′-bipyridine, 2,2′-bipy = 2,2′-bipyridine). Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, infrared spectra, thermogravimetric analysis, powder X-ray diffraction, and circular dichroism. Compounds 1 and 2 are isostructural (0-D structures), which are extended to supramolecular 1-D chains by hydrogen bonding. Compound 3 exhibits 1-D straight chain structures, which are further linked via hydrogen bond interactions to generate a 3-D supramolecular architecture. Compound 4 displays a discrete molecular unit. Neighboring units are further linked by hydrogen bonds and π–π interactions to form a 3-D supramolecular architecture. Compound 5 displays a 2-D undulated network, further extended into a 3-D supramolecular architecture through hydrogen bond interactions. Compound 6 possesses a 2-D sheet structure. Auxiliary ligands and counteranions play an important role in the formation of final frameworks, and the hydrogen-bonding interactions and π–π stacking interactions contributed to the formation of the diverse supramolecular architectures. Compounds 1, 2, 4, 5, and 6 crystallize in chiral space groups, with the circular dichroism spectra exhibiting positive cotton effects. Furthermore, the luminescent properties of 4–6 have been examined in the solid state at room temperature, and the different crystal structures influence emission spectra significantly. 相似文献
3.
L. M. Babkov T. V. Bezrodnaya G. A. Puchkovskaya K. E. Uspenskii V. V. Shimanovaskaya 《Journal of Structural Chemistry》2008,49(3):517-523
This contribution provides the theoretical background for the structure-determining role of hydrogen bonding in the formation of a near-surface layer of titania nanocrystallites, previously revealed by the authors in the investigation of IR experimental spectra of two-component solid mixtures of nanocrystalline titanium dioxide with benzophenone or 4-pentyl-4′-cyanobiphenyl. DFT calculations (B3LYP) in 6-31+G(d) basis set is used to simulate the structure and IR spectra of free molecules of water, 4-pentyl-4′-cyanobiphenyl, benzophenone and their H-complexes formed in the near-surface layers of titania nanocrystallites due to presence of water adsorbed on their surfaces. Using the results of simulation and analysis of IR spectrum bands corresponding to stretching vibrations of polar bonds O-H, C=O, C≡N, the formation mechanism of near-surface layers of titania nanocrystallites in the considered heterogeneous two-component systems is theoretically substantiated: they are formed by hydrogen-bonded complexes involving components of the mixture and water. 相似文献
4.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(5):542-547
The structural chemistry of 2‐[4,7,10‐tris(carbamoylmethyl)‐1,4,7,10‐tetraazacyclododecan‐1‐yl]acetic acid dihydrate, C16H31N7O5·2H2O, is described. The macrocyclic compound, also known by the abbreviation DOTAM‐mono‐acid, crystallized at room temperature and was isolated concomitantly as two polymorphic forms. The structures of both polymorphs were determined at 90 K. The first polymorph crystallized as a zwitterionic dihydrate [systematic name: 4,7,10‐tris(carbamoylmethyl)‐1‐(carboxylatomethyl)‐1,4,7,10‐tetraazacyclododecan‐1‐ium dihydrate] in the space group P21/n, with Z′ = 1. The second polymorph crystallized as a zwitterionic dihydrate in the space group P21 at 90 K, with Z′ = 2. The two independent molecules are related by a local center. In each polymorph, the zwitterion is formed between the negatively‐charged carboxylate group and the ring N atom that bears the acetate pendant arm. Extensive inter‐ and intramolecular hydrogen bonding exists in both polymorphic structures. In polymorph 1, an intermolecular hydrogen‐bonding network propagating parallel to the a direction creates an infinite chain. A second hydrogen‐bonding network is observed through a water molecule of hydration in the b direction. Polymorph 2 also has two intermolecular hydrogen‐bonding networks. One propagates parallel to the a direction, while the other propagates in the [10] direction. Increasing the temperature of polymorph 2 yields the same structure at T = 180 K, but the pseudocenter becomes exact at 299 K. The higher‐temperature structure has Z′ = 1 in the space group P21/c. 相似文献
5.
Two series of new hydroxy tail-terminated cyanobiphenyl compounds are described. The 4′-ω-hydroxyalkynyl-4-cyanobiphenyl compounds (1a–1g) were synthesised as the key intermediates to the 4′-?ω-hydroxyalkyl-4-cyanobiphenyl compounds (2a–2g) obtained upon reduction of the acetylenes. Many of these ω-hydroxyalkynyl and ω-hydroxyalkyl cyanobiphenyl compounds exhibit nematic mesophases and they also serve as precursors for the synthesis of other interesting materials. Using density functional theory, we calculate the dipole moment of all relevant ω-hydroxyalkynyl and ω-hydroxyalkyl cyanobiphenyl compounds and find a correlation between the calculated dipole moments and measured crystalline to nematic or isotropic liquid transition temperatures. 相似文献
6.
Wendy A. Reed Allen G. Oliver Linfeng Rao 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(9):m301-m303
The environment of the U atom in the title compound, (C4H12N)4[UO2(CO3)3]·8H2O, presents a typical hexagonal bipyramidal geometry found in many actinide complexes. It is a model for actinide species and consists of common environmental moieties (carbonate, water and ammonia species). The structure displays a sheet‐like hydrogen‐bonding network formed from crystallization water molecules and carbonate ligands. The compound is isomorphous with a previously described Np isolog [Grigorev et al. (1997). Radiokhimiya (Russ. Radiochem.), 39 , 325–329]. 相似文献
7.
A series of 2-(2-oxoalkylidene)-4(1H)-pyrimidinone nucleoside analogs were synthesized by the addition of the lithium enolates of methylketones to 2,5′- and 2,2′-anhydrouridines and to 2,5′-anhydrothymidines. Alternatively, 2-thiouridine was alkylated with bromomethyl ketones to yield 2-(2-oxoalkyl)thio-4(1H)-pyrimidinone ribofuranosides in good yields. These intermediates were subsequently transformed into the title compounds via an Eschenmoser sulfur extrusion reaction. The 2-(2-oxoalkylidene)-4-(1H)-pyrimidinone nucleoside analogs exhibit enol proton signals in their 1H nmr spectra indicative of hydrogen bonding between N-3 and keto oxygen. These structures offer functional groups with potential for Watson-Crick hydrogen bonding. 相似文献
8.
G. L. Hoatson A. L. Bailey A. J. van der Est G. S. Bates E. E. Burnell 《Liquid crystals》2013,40(6-7):683-694
Abstract Deuteron magnetic resonance spectroscopy (2H-N.M.R.) has been used to investigate the effect of the nematic environment on the flexibility and orientational order of two perdeuteriated cyanobiphenyl homologues: 4-methyl-4′-cyanobiphenyl (1CB-d 11) and 4-n-pentyl-4′-cyanobiphenyl (5CB-d 19). The systems studied were low concentrations of 1CB-d 11 and 5CB-d 19 dissolved in the nematic phases of 5CB, N-(-4-ethoxybenzylidene)-4′-n-butylaniline (EBBA), Merck ZLI-1132 (1132) and a 55wt% mixture of 1132: EBBA. The spectra are dramatically different in these environments. Previous studies on small solutes have suggested that in the 55wt% 1132: EBBA mixture (at 301.4 K) the dominant orienting mechanism depends on the size and shape of the molecule which suggests that it is a short range repulsive interaction. This interaction has been modelled by treating the liquid crystal as an elastic continuum and the solute as a collection of van der Waals spheres which stretch the liquid crystal in the two dimensions perpendicular to the director. The distortion of the liquid crystal depends on the dimensions of the solute, and the elastic energy is described in terms of a Hooke's law force constant, k. The model is extended to include flexible liquid crystal molecules and quadrupolar couplings are calculated for each conformation of the 5CB chain. Statistical averaging over all conformations gives an excellent fit to the experimental spectrum. The results for 1CB and 5CB show that in the other nematic phases contributions from additional mechanisms must be included. Previous studies of 2H2 and other solutes indicate that the additional mechanism is the interaction between the solute molecular quadrupole moment and the mean electric field gradient of the liquid crystal. 相似文献
9.
《Journal of Coordination Chemistry》2012,65(3):398-408
Two supramolecular compounds based on Keggin polyoxotungstates, (4,4′-H2bpy){[Cu(4,4′-bpy)]2[SiW12O40]} (1) and (4,4′-H2bpy)2[SiW12O40]·2H2O (2) have been synthesized and characterized by elemental analyses, IR, UV, XPS spectra, TG analyses, and single crystal X-ray diffraction analyses. Compound 1 exhibits an infinite 1-D ladder like structure, which is further interconnected into a 3-D supramolecular framework via hydrogen bonding interactions. Compound 2 contains 4,4′-bipyridine (4,4′-bpy), pseudo-Keggin polyoxoanions [SiW12O40]4?, and water molecules. Polyoxoanions together with water molecules in 2 construct a 3-D inorganic supramolecular network through O···O and O···Ow(1) interactions. The electrochemical behaviors and photocatalytic properties of 1 and 2 have been investigated. 相似文献
10.
Abstract Dielectric studies of 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzene (6CHBT) were performed in the pressure range 0·1–150 MPa, the frequency range 1 kHz–13 MHz and the temperature range 295–325 K. The temperature and pressure dependencies of the static permittivity ?0∥ and of the relaxation time τ∥ are analysed and compared with the analogous data obtained recently for 4-n-pentyl-4′-cyanobiphenyl (5CB) (Parts I and II of this series). Marked differences in the dielectric properties of the nematic phases of the two substances are observed. They are interpreted as a result of varying degrees of molecular association in particular compounds. It is concluded that in the nematic phase of 6CHBT dipole–dipole correlations do not exist or are very weak, whereas for 5CB they are easily broken by a relatively low pressure. 相似文献
11.
Takashi Kato Toshiyuki Uryu Fumiko Kaneuchi Chihiro Jin Jean M. J. Fréchet 《Liquid crystals》2013,40(5):1311-1317
Abstract The stability of a hydrogen-bonded complex built through inter-molecular hydrogen bonding between carboxylic acid and pyridine fragments has been examined using infrared spectroscopy. Infrared spectra as a function of temperature have been recorded for the 1:1 complex of 4-hexyloxybenzoic acid and trans-4-propoxy-4′-stilbazole from the crystalline state to the isotropic state. A dependence of the stability of the hydrogen bond on molecular orientation is observed clearly in the infrared spectra. The spectra also suggest that the hydrogen bond is an unionized type with a double minimum potential energy. 相似文献
12.
B. M. Heskamp G. A. van der Marel J. H. van Boom 《Journal of carbohydrate chemistry》2013,32(9):1265-1277
Abstract The synthesis of cyclohexyl 2-acetamido-2-deoxy-3-O-{2-O-[2-(guanosine 5′-O-phosphate)ethyl]-α-L-fucopyranosyl}-β-D-glucopyranoside (1), a potential inhibitor of α(1→3)fucosyltransferases, is described. Target compound 1 was assembled via fucosylation of cyclohexyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-β-D-glucopyranoside (6) with ethyl 2-O-[2-(benzoylhydroxy)ethyl]-3,4-O-isopropylidene-1-thio-β-L-fucopyranoside (5) followed by debenzoylation, subsequent condensation of the resulting compound with 3′,4′ -di-O-benzoyl-5′ -O-(2-cyanoethyl-N,N-diisopropylphosphoramidite)-2-N-diphenylacetylguanosine (10) and deprotection. 相似文献
13.
Dawei Jiang Simone Budow Virginie Glaon Henning Eickmeier Hans Reuter Yang He Frank Seela 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(4):o194-o197
The title compound, C10H12FN5O4·H2O, shows an anti glycosyl orientation [χ = −123.1 (2)°]. The 2‐deoxy‐2‐fluoroarabinofuranosyl moiety exhibits a major C2′‐endo sugar puckering (S‐type, C2′‐endo–C1′‐exo, 2T1), with P = 156.9 (2)° and τm = 36.8 (1)°, while in solution a predominantly N conformation of the sugar moiety is observed. The conformation around the exocyclic C4′—C5′ bond is −sc (trans, gauche), with γ = −78.3 (2)°. Both nucleoside and solvent molecules participate in the formation of a three‐dimensional hydrogen‐bonding pattern via intermolecular N—H...O and O—H...O hydrogen bonds; the N atoms of the heterocyclic moiety and the F substituent do not take part in hydrogen bonding. 相似文献
14.
‘Slipped’ π?π stacking between flexible macrocycle 14+ (cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylene benzene)) and neutral small molecules induce one-dimensional (1D) ‘sandwich’ chain self-assembly. Unlike most of the reported π?π stacking system, the 1D “sandwich” chain expands with the direction parallel to stacking π surfaces on 14+ and that on molecule 2, 3, 4 or 5 (2 = p-xylene, 3 = benzene-1,4-diamine, 4 = 4,4′-bipyridine, 5 = [1,1′-biphenyl]-4,4′-diol). Moreover, the π?π stacking modes of 1D self-assembly are seriously small molecule adduct dependent. Combined with the other weak interactions (e.g. intermolecular hydrogen bonding), the new substrate design and control strategy can expand the 1D ‘sandwich’ chain (e.g. [14+·4]n) into higher order structure (e.g. two-dimensional (2D) network [14+·4·6]n, 6 = hydroquinone) even in large scale (~280 mg). This 2D network structure, which keeps stable under 423 K, shows highly selective gas absorption of CO2 over N2. 相似文献
15.
Patanair Bindu Babu Varghese Madhugiri N. Sudheendra Rao 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2373-2386
Synthesis of the hypervalent tris(catecholato)silicate ion, [(C6H4O2)3-Si]2? having five different primary ammonium cations viz. n-propylammonium (1), isopropylammonium (2) n-butylammonium (3), cyclohexylammonium (4), benzylammonium (5), and a bulky secondary ammonium cation, namely diisobutylammonium (6), have been achieved by the reaction of catechol and tetraethoxysilane (TEOS) in presence of the corresponding amine. Elemental analysis, IR, NMR (1H, 13C, and 29Si), and mass spectral data have been used for their characterization. Single crystal x-ray structures of 1 and 6 indicate nearly same distortion of the “SiO6” octahedron but interesting differences in the hydrogen bonding interactions arising from the catecholato oxygens and the N—H bonds of the ammonium cations. While compound 1 exhibits hydrogen bonding more discretely and by revealing strong interaction between the n-propylammonium ions, compound 6 shows an extended intermolecular hydrogen bonding aided by a water molecule present in the lattice to lead to infinite one dimensional chain arrangement. TG and EG analyses of compounds, 1–5 indicate 1) the formation of the previously observed spirosilane intermediate, [Si(C6H4O2)2] and 2) their less thermal stability compared to those having secondary or tertiary ammonium cations. 相似文献
16.
Abstract A radial hydrodynamic flow in the nematic phase of free, suspended cylindrical films of 4-n-heptyl- and decyloxybenzoic acid and in 4,4′-di-n-heptyl-oxyazoxybenzene has been observed. The flow starts about 7°C before the phase transition into the smectic C phase. Under the same experimental conditions such a hydrodynamic flow is not established in free nematic films of 4-n-heptyl-and octyloxy-4′-cyanobiphenyl, 4,4′-dimethoxyazoxybenzene and N-(4-ethoxybenzylidene)-4′-n-butylaniline after the completion of the transition from the isotropic liquid to the nematic phase. The observed hydrodynamic flow is explained by a non-linear temperature dependence of the surface tension. 相似文献
17.
The transitional behaviour of binary mixtures, each containing a non-mesomorphic quasi-spherical solute at a low mole fraction in a nematogenic solvent, has been investigated by E.S.R. spectroscopy using 4-oxo-2,2,6,6-tetramethyl-4-piperidinyl-1-oxy (tempone) as a spin probe. This approach makes use of the smaller coupling constant obtained for the spin probe in the orientationally ordered nematic phase relative to that obtained in the isotropic phase. The solutes included Et4C (tetraethylmethane) and R 4Sn (R = Cb2bH5, n-C3 H 7 and nCb4H9). The solvents were 4-n-pentyl-4′-cyanobiphenyl (5CB) 4-n-hexyl-4′-cyanobiphenyl (6CB) and 4-n-heptyl-4′-cyanobiphenyl (7CB). This fast approach compares favourably with other studies. In addition it provides the tempone spectral parameter, f, which is a relative measure of the fraction of the nematic phase at different temperatures within the two phase region. 相似文献
18.
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. 相似文献
19.
Isolation and characterisation of compounds, 1-(2′-hydroxy-4′-methoxyphenyl)-3-(4″-methoxyphenyl)-2-hydroxypropane-1,3-dione (1), 5-hydroxyflavone (2), 3,5,7,3′,4′-pentahydroxyflavone (3), 3,5,7,2′,4′-pentahydroxyflavone (4) and 5,7,3′,4′-tetrahydroxyflavone-3-O-rhamnoside (5) are reported from the air dried flowering buds of Bauhinia tomentosa Linn. Their structures are determined on the basis of extensive chemical and spectral evidences. Compound (1) is reported for the first time from the plant source. While compounds (2) and (4) are reported for the first time from this genus, compound (2) is reported for the second time from the natural source. 相似文献
20.
Bing-Fan Long Qin Huang Shu-Long Wang Yan Mi Meng-Fan Wang Ting Xiong 《Journal of Coordination Chemistry》2019,72(4):645-663
Five cobalt(II) complexes based on 1H-indazole-3-carboxylic acid (H2L), [Co(phen)(HL)2]·2H2O (1), [Co(5,5′-dimethyl-2,2′-bipy)(HL)2] (2), [Co(2,2′-bipy)2(HL)2]·5H2O (3), [Co2(2,9-dimethyl-1,10-phen)2(L)2] (4) and [Co2(6,6′-dimethyl-2,2′-bipy)2(L)2]·H2O (5) (2,2'-bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and structurally characterized by elemental analyses, IR and UV-vis spectroscopies and single-crystal X-ray crystallography. The results indicate that 1–3 possess mononuclear Co(II) structures, while 4 and 5 exhibit binuclear structure. 1D water tape which is linked by the multiple hydrogen bonds was embedded in the 3D motif of complex 3. Complexes 4 and 5 show two orthogonal planes of motif that was constituted by phen/2,2′-bipy and indazole acid, respectively. The intermolecular interactions including hydrogen bonding and π-π stacking interactions are stabilizing these complexes. The interactions of the synthesized complexes with calf-thymus DNA (CT-DNA) have been investigated by UV-vis absorption titration, ethidium bromide displacement assay and viscosity measurements. The results reveal that the complexes could interact with CT-DNA via a groove binding mode. Their behavior rationalization was further theoretically studied by molecular docking. 相似文献