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Dielectric constants and the dielectric loss in the frequency range from 0.1–12 MHz were measured in the binary systems of 4-n-heptylamino benzoic acid with 4-cyano benzoic acid and 4-fluoro benzoic acid in the nematic phase. Not only the strong increase of dielectric anisotropy, but also the appearance of a Debye relaxation in the MHz range in both the mixtures proves the existence of the mixed associates. This model was proved by the temperature dependence of relaxation times and on chemical structure of the mixed associates, as well as, by the comparison with the measurements of one more binary system of acids. 相似文献
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Crystal etching, though a simple and widely adopted technique for the study of imperfections in a wide variety of materials, the process is not very well understood. The etch pit shapes are controlled by a number of factors, such as, the composition of etchant, the period of etching, the temperature of etching and the symmetry of plane under study. This communication reports observations of etching the (001) cleavage planes of anthracene in sulphuric acid — formic acid mixtures. 相似文献
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Manuela Ramos Silva Claudia Cardoso Ana Matos Beja Jose A. Paixão Sergio R. Domingos 《Journal of chemical crystallography》2008,38(6):403-406
Abstract Crystal structure of diphenylacetic acid has been solved by X-ray diffraction. The crystals are monoclinic, space group P21/c, with a = 12.254(4) ?, b = 7.2260(8) ?, c = 17.521(4) ?, β = 133.38(1)°, Mr = 212.24, V = 1127.6(5) ?3, Z = 4 and R = 0.045. A strong hydrogen bond links the molecules in dimers. The dimers are connected by weaker C–H···π and π···π interactions.
A calculation was performed for the isolated molecule and for the dimer within the Hartree-Fock (HF) level with a 6-311G(d)
basis set. In both calculations, the minimum of the energy is achieved with the phenyl rings assuming a more symmetric arrangement
around the central carboxylic plane than is experimentally observed.
Graphical Abstract In diphenylacetic acid the molecules are coupled in dimers by a strong hydrogen bonds. Weaker intermolecular interactions
involving the aromatic ring π systems join the dimers together.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Kusum Bania Nilotpal Barooah Rupam Sarma Jubaraj Bikash Baruah 《Journal of chemical crystallography》2008,38(1):57-60
Abstract The crystal structure of a metallohybrid carboxylic acid obtained from the reaction of 1,3,5-benzenetricarboxylic acid (TCAH3)
with copper(II)acetate monohydrate in the presence of pyridine (py) having composition Cu(py)2(TCAH2)2(H2O)2 [1] is reported. It crystallizes in triclinic space group P-1 and with a = 7.0110(3)?, b = 8.9523(5)?, c = 11.5370(5) ?,
α = 79.776(3) °, β = 82.881(3)°, γ = 83.628(3)°, and V = 704.18(6)?3. The hydrogen bond in 1 is compared with the hydrogen bond pattern in the structure of 1,3-dicarbomethoxy 4,6-benzenedicarboxylic
acid, which crystallizes in mononclinic space group P21/c and has unit cell parameters of a = 6.9549(16)?, b = 8.7676(15)?,
c = 20.111(4)?; β = 92.585(17) ° and V = 1225.1(4) ?3.
Index Abstract Crystal structure of a metallohybrid carboxylic acid obtained from the reaction of 1,3,5-benzenetricarboxylic acid with copper(II)acetate
monohydrate in the presence of pyridine is determined and compared with hydrogen bond pattern present in the structure of
1,3-dicarbomethoxy 4,6-benzenedicarboxylic acid.
Crystal structure of a metallohybrid acid of 1,3,5-benzenetricarboxylic acid of copper(II).
Kusum Bania, Nilotpal Barooah, Rupam Sarma, Jubaraj B. Baruah 相似文献
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Alabada R. Avramenko O. V. Strashnova S. B. Sergienko V. S. Absalan Ya. Kovalchukova O. V. 《Crystallography Reports》2021,66(3):429-432
Crystallography Reports - The crystal and molecular structure of 2-hydrazinobenzoic acid was determined. In solution in the presence of copper(II) chloride, 2-hydrazinobenzoic acid is transformed... 相似文献
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P. B. V. Prasad 《Crystal Research and Technology》1991,26(4):501-509
The formation of heat induced fracture-like patterns, slip-twin promoted deformation, some epitaxial relations are discussed in case of n-pentadecanoic acid crystals, grown from solutions, by solvent evaporation methods. 相似文献
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Journal of Chemical Crystallography - A second polymorph of an anhydrous 1:1 caffeine citric acid cocrystal (C8H10N4O2, C6H8O7) is reported. Crystals were analyzed using single crystal X-ray... 相似文献
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The results on the phase transitions in p-n-heptyloxybenzylidene-p-aminobenzoic acid are reported. The microscopic and X-ray studies show that the compound goes over from smectic C to nematic phase directly. The transition entropies and specific heat are determined using differential scanning calorimetry. The translational order parameter is determined using low angle X-ray intensity measurements. The tilt angle in smectic C phase is found to be 56° and is independent of temperature. The X-ray data also lead to the conclusion that the compound exists as a dimer. 相似文献
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The crystal structures of three salts and two solvated multicomponent crystals of lamotrigine with 4-fluorobenzoic acid, nicotinic acid, 2-thiobarbituric acid, 3-picoline and butyl alcohol are reported. Compound 1a crystallizes in monoclinc system, space group P21 with a = 13.3860(5) ?, b = 8.3420(3) ?, c = 15.5200(6) ?, β = 93.524(1)°, V = 1729.78(11) ?3, and Z = 2. Compound 1b crystallizes in monoclinic system, space group P21/c with a = 10.6625(7) ?, b = 16.2575(11) ?, c = 13.6346(9) ?, β = 100.904(1)°, V = 2320.8(3) ?3, and Z = 4. Compound 1c crystallizes in triclinic system, space group P[`1] \overline{1} , with a = 10.1309(7) ?, b = 12.0260(8) ?, c = 14.0826(10) ?, α = 71.783(1)°, β = 86.451(1)°, γ = 80.902(1)°, V = 1609.10(19) ?3, and Z = 1. Compound 1d crystallizes in monoclinic system, space group P21/c with a = 14.9570(10) ?, b = 8.0230(6) ?, c = 13.8162(10) ?, β = 102.884(1)°, V = 1616.2(2) ?3, and Z = 4. Compound 1e crystallizes in triclinic system, space group P[`1] \overline{1} , with a = 7.5710(6) ?, b = 8.5721(7) ?, c = 13.5532(11) ?, α = 85.364(1)°, β = 79.632(1) (1)°, γ = 86.188(1)°, V = 861.19(12) ?3, and Z = 2. Characteristic R22(8) dimer is observed in all five structures. A complete hydrogen bonded motif analysis is described. Lamotrigine-lamotrigine base pair is observed in all the structures, except in (1b). In (1c), the R22(7) dimer is noticed while, in all other structures R22(8) dimer exist between the lamotrigine-lamotrigine base pair. In all the six structures, chlorine atoms of the lamotrigine molecules are not involved in any interactions. 相似文献13.
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R. Somashekar 《Molecular Crystals and Liquid Crystals》2013,570(3-4):341-344
The order parameters of a number of novel 2-aryl-l,4-naphthoquinone dyes dissolved in a mixed cyanobiphenyl-terphenyl nematic liquid crystal system (Type E43, B.D.H. Chemicals Ltd.) have been determined. Observed values range from 0.80 to 0.09, and can be interpreted qualitatively by consideration of the w-dipole moment and transition moment directions of the dyes calculated by the PPP-SCF-CI MO method. 相似文献
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Saikat Santra Babulal Das Jubaraj B. Baruah 《Journal of chemical crystallography》2011,41(12):1981-1987
Abstract
Different types of structures of hydrogen-bond assemblies derived from partially deprotonated dipicolinic acid (LH2) molecules having alkali metal cation such as sodium, potassium and cesium are structurally characterised. These self assembled complexes have general formula [M(LH)(LH2)(H2O) m ] n xH2O {m = 2, 3, n = 1, 2, n, and x = 0, 0.5 M = Na (1); K (2) and Cs(3)}. Sodium complex is a hepta-coordinate mononuclear complex; potassium complex is octa-coordinate complex with dinuclear K2O2 type of carboxylate core; whereas the cesium complex is nona-coordinate polymeric complex. All these complexes crystallises in Triclinic, P-1 space group. Sodium complex has a = 6.9003(4) ?; b = 11.1440(6)?; c = 11.2059(5)?; α = 85.695(4)o; β = 82.103(3)o; γ = 87.432(4)o and volume = 850.60(8) ?3 Z = 2; Potassium complex has a = 7.0937(4)?; b = 11.0034(5)?; c = 11.2732(6)?; α = 91.603(3)o; β = 96.088(3)o; γ = 97.207(4)o; volume = 867.29(8) ?3; Z = 1 and cesium complex has a = 7.1410(6)?; b = 11.0625(8)?; c = 12.0667(9)?; α = 96.849(4)o; β = 93.850(4)o; γ = 105.495(4)o; volume = 907.14(12) ?3; Z = 2. 相似文献17.
Jerry P. Jasinski Ray J. Butcher H. S. Yathirajan B. Narayana L. Mallesha K. N. Mohana 《Journal of chemical crystallography》2009,39(6):453-457
Abstract The title compound, C9H8O4, (I), crystallizes in the monoclinic space group P 21/c with unit cell parameters a = 7.3380(5) ?, b = 9.3790(7) ?, c = 12.3172(9) ?, β = 90.687(7)°, Z = 4. The molecule consists of a benzene ring fused to a 1,4 dioxane ring in a half-chair conformation with a carboxylic acid
group bonded at the dioxane 2-position. The carboxylic acid group forms a classic O–H···O hydrogen bonded dimer with an O···O
distance of 2.6292(12) ? in a R22 (8) graph-set motif which links the molecules into pairs around inversion centers in a supramolecular assembly in the unit
cell. The dihedral angle between the mean planes of the R22 (8) graph-set motif’s of two adjacent dimers in the unit cell is 75.7(5)°. The mean plane of an R22 (8) graph-set motif makes an angle of 88.4(5)° with the mean plane of the benzene ring in the same dimer and 13.1(2)° or
13.4(7)° with the mean plane of a benzene ring from an adjacent dimer. Additional weak Cg π-ring intermolecular interactions significantly influence the bond distances, bond angles and torsion angles of the dioxane
ring and attached carboxyl group. Comparison to a MOPAC AM1computational calculation provides support to these observations.
Graphical Abstract The association of carboxylic acid dimers in the supramolecular assembly of (R)-1,4-benzodioxane 2-carboxylic acid is investigated
by examination of its crystal structure. Its geometric and packing parameters are described and compared to a MOPAC AM1 computational
calculation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Chang-chun Ai Yong Xiao Shuo-ping Chen Qiao-yun Liu Ling-ling Pan Yi-xuan Yuan Liang-jie Yuan 《Journal of chemical crystallography》2011,41(8):1202-1207
Abstract
The 1-aminoethylidenediphosphonic acid (AEDPH4) is anhydrous when it is synthesized according to the U.S. Patent 4239695. It crystallizes in water to form hydrous crystal AEDPH3·H3O (1). With the help of a simple low-temperature, low-pressure hydrothermal method and template 2,2′-bidpyridyl (2,2′-bipy), single crystals with the same structure of the anhydrous AEDPH4 (2) is obtained. Compound 2 were characterized by elemental analysis (EA), infrared spectrometry (IR), thermogravimetric analysis (TGA) and X-ray single crystal diffraction. In compounds 2, the AEDPH4 molecules are linked into 3D supramolecules by various hydrogen bonds. 相似文献20.
以改进的氧化还原法(Hummers法)制备的氧化石墨烯为原料,采用乙醇萃取法过滤酸性氧化石墨烯溶液使其恢复至中性.对比分析了与以往采用水剂法进行清洗的效果,并且进一步考察了乙醇浓度以及温度对萃取过程的影响.采用Zeta电位、场发射扫描电镜、X射线衍射仪以及pH值检测和重溶情况对萃取效果进行了表征和判断.试验结果表明:乙醇萃取法可以大大缩短酸性氧化石墨烯溶液恢复至中性的时间并且不改变其本身性能;当氧化石墨烯溶液浓度为1 mg·mL-1和0.5 mg·mL-1时,分别加入浓度为40; v/v和95; v/v乙醇,温度为60℃是最佳的萃取选择. 相似文献