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ABSTRACT: Crystals of cyanocyclopropane have been grown from liquid. At −85°C, cell parameters are a = 7.244(5), b = 7.821(2), c = 6.916(3) Å in the orthorhombic space group Pnma with Z = 4. Intensity data were collected in three different ways, viz. photographically using rotation and Weissenberg techniques and electronically by means of a diffractometer. Within the limits of accuracy, the three data sets result in equal bond lengths and angles. The most important result from the structure determination is the difference of 0.033 Å between the lengths of the distal and vicinal ring bonds, which had not previously been measured directly from X-ray experiments.
Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 104(1):7 - 9.
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ABSTRACT: Crystals of N,N-dimethyl-p-bromocinnamamide are triclinic of space group P1p̄, Z = 2, cell constants a = 7.686, b = 12.325, c = 5.850 Å, α = 83.98, β = 81.27 and γ = 94.23°.The plane of the CO-N(CH3)2-group is rotated 15° out of the s-cis conformation with respect to the rest of the conjugated system.
Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 90(5):508 - 512.
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ABSTRACT: Intercalated layered structures are analyzed in order to estimate the rules governing their crystal packing. An overview is given on structural types of layered intercalates based on various types of host structures and guest species. The factors describing the host–guest complementarity in intercalated layered structures like: the character of active sites, the host–guest and guest–guest interactions, the size of guests and topology of layers are investigated and their effect on crystal packing is illustrated on examples. Special attention will be paid to the conditions for the regular ordering of guests in the interlayer space, as the requirement of structure ordering is of great importance in design of intercalates for special applications, where one has to control the interlayer porosity or electronic properties of guest molecules etc. A method of structure analysis based on a combination of molecular modeling and experiments has been worked out for intercalates. Molecular modeling (force field calculations) in conjunction with experiments (diffraction methods and vibration spectroscopy) enables us to analyze the disordered intercalated structures, where the conventional diffraction analysis fails.
Journal of Inclusion Phenomena 09/2003; 47(1):1-10. · 1.89 Impact Factor
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ABSTRACT: Molecular mechanics simulations using the Cerius2 modeling environment have been applied to study the structures of dioctahedral smectites intercalated with the zirconium cation [Zr4(OH)12(H2O)12]4+. The substitutions in the silicate layers influence the sublimation energy in these types of intercalated layer structures. Charge distribution in the smectite layer was analyzed in relation to the interlayer structure. Tetrahedral substitutions in the smectite layer create preferential interlayer positions of the [Zr4(OH)12(H2O)12]4+ ion. A regular distribution of the tetrahedral substitutions in the smectite layer results in a better intercalant ordering in the interlayer space. Such a more homogeneous intercalant distribution results in a better interlayer pore size control.
Journal of Colloid and Interface Science 09/2003; 264(2):474-80. · 3.07 Impact Factor
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ABSTRACT: The title compound was synthesized and isolated in two crystal modifications. The structure of the orthorhombic modification was determined by the X-ray powder diffraction method and the structure of the monoclinic modification was determined using the X-ray single-crystal diffraction technique. The molecules in both polymorphs are E,E isomers. Intermolecular H(3)C....NO(2) contacts and their role in the formation of the polymorphic modifications are analyzed.
Acta Crystallographica Section B Structural Science 09/2003; 59(Pt 4):492-7. · 2.29 Impact Factor
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Acta Crystallographica Section E. 01/2003; 59(5):o591-o593.
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Acta Crystallographica Section E. 01/2003; 59(3):o266-o268.
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ABSTRACT: The crystal structures of 8-hydroxy-5-nitroquinoline, C9H6N2O3, (I), and 8-hydroxy-5-nitroquinolinium chloride, C9H7N2O3+*Cl-, (II), have been determined from X-ray powder data. In (I), the molecules are linked via moderately strong hydrogen bonds to form dimers. Such a packing motif is likely to be responsible for the low solubility of (I) in water. In (II), the inversion-related cations form stacks, and anions fill the interstack channels.
Acta Crystallographica Section C Crystal Structure Communications 02/2002; 58(Pt 1):o19-21. · 0.52 Impact Factor
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ABSTRACT: The crystal structures of [1,2-bis(2,6-diisopropylphenylimino)acenaphthene-N,N']carbonylchlororhodium(I) (1) and [N,N'-ethylene-bis(3-methylsalicylideneiminato)-O,N,N',O'](tetrahydrofurfuryl)-cobalt(II) (2) have been determined from high-resolution synchrotron X-ray powder diffraction data. Compound 1 is the first neutral Rh complex, in contrast with findings in the literature, containing a bidentate nitrogen ligand, and compound 2 is the first three-dimensional structure of a (five-coordinated) tetrahydrofurfurylcobalt(III) complex. Grid-search and Rietveld refinement have been used to determine and refine the structures, respectively. Crystals of 1 are orthorhombic, space group Pbca, Z = 8, with cell parameters a = 21.729 (2), b = 27.376 (3), c = 11.580 (1) A. Crystals of 2 are monoclinic, space group P2(1)/n, Z = 4, a = 16.6701 (6), b = 9.4170 (4), c = 13.7088 (7) A and beta = 96.520 (3) degrees. Chemical diagrams for the two compounds are given. Soft restraints were applied during Rietveld refinement; for 1 converging to R(p) = 8.4%, R(w) = 11.0%, GoF = 2.3, and for 2 converging to R(p) = 8.5%, R(w) = 11.4%, GoF = 7.6.
Journal of Synchrotron Radiation 12/2001; 8(Pt 6):1186-90. · 2.73 Impact Factor
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ABSTRACT: The crystal structures of potassium [2.2]paracyclophane-4-sulfonate (1), [2.2]paracyclophane-4,15-disulfonic anhydride (2), [2.2]paracyclophane-4,15-disulfonimide (3), N-n-propyl-[2.2]paracyclophane-4,15-disulfonimide (4), N-isopropyl-[2.2]paracyclophane-4,15-disulfonimide (5), N-cyclopropyl-[2.2]paracyclophane-4,15-disulfonimide (6) and N-phenyl-[2.2]paracyclophane-4,15-disulfonimide (7) were established by single-crystal X-ray diffraction. The structural changes caused by sulfonation are discussed with respect to the parent [2.2]paracyclophane (tricyclo[8.2.2.2(4,7)]hexadeca-4,6,10,12,13,15-hexaene). The main features are a change in the non-bonding distances between the para-phenylene rings and a rotation of these rings with respect to the molecular symmetry plane. The rings are rotated away from each other in the case of monosulfonation (1), but are rotated in the opposite way in the case of the disulfonic anhydride (2) or the disulfonimide compounds (3)-(7). The results are also discussed in terms of the parameters proposed by Keehn [(1983), Organic Chemistry, A Series of Monographs 45, edited by P. H. Keehn & S. M. Rosenfeld, Vol. 1, pp. 69-238. New York: Academic Press] showing that (bonded and non-bonded) angles involving the para-phenylene rings are mainly affected.
Acta Crystallographica Section B Structural Science 12/2001; 57(Pt 6):780-90. · 2.29 Impact Factor
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ABSTRACT: The evidence for thermal isomerization of the title compound, C(24)H(15)N(5)O(2), into 2-[(4-nitrophenyl)phenylamino]-5H-pyrido[3,2-b]indole-3-carbonitrile has been obtained as a consequence of crystal structure determinations from laboratory powder data.
Acta Crystallographica Section C Crystal Structure Communications 09/2001; 57(Pt 8):982-4. · 0.52 Impact Factor
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ABSTRACT: The structure of the coordination compound [Fe(teec)(6)](BF(4))(2), hexa[1-(2-chloroethyl)tetrazole]iron(II) di(borotetrafluoride), has been determined using the grid-search techniques of the program suite MRIA. A Guinier-camera data set was used to determine the unit cell, the space group and to position the initial model. A high-resolution synchrotron powder data set was used to position a more detailed model using torsion-angle variation and to refine the structure leading to Rp = 0.0689, Rw = 0.0805 and GoF = 1.38. The crystal structure at room temperature shows the existence of two symmetry-equivalent iron(II) ions in the high-spin state.
Acta Crystallographica Section B Structural Science 09/2001; 57(Pt 4):531-8. · 2.29 Impact Factor
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ABSTRACT: The crystal structures of beta-1,2,3-tritetradecanoylglycerol (beta-trimyristin or beta-MMM) and beta-1,2,3-trioctadecanoylglycerol (beta-tristearin or beta-SSS) have been determined from high-resolution synchrotron X-ray powder diffraction data. Grid search and Rietveld refinement have been used to determine and refine the structure, respectively. Both substances crystallize in space group P1; with Z = 2. The unit-cell parameters for beta-MMM are a = 12.0626 (6), b = 41.714 (1), c = 5.4588 (3) A, alpha = 73.388 (4), beta = 100.408 (5) and gamma = 118.274 (4) degrees. For beta-SSS the unit-cell parameters are a = 12.0053 (7), b = 51.902 (2), c = 5.4450 (3) A, alpha = 73.752 (5), beta = 100.256 (6) and gamma = 117.691 (5) degrees. Soft-distance restraints have been applied to the molecules during refinement. For beta-MMM the final R(p) value obtained is 0.053 and for beta-SSS the final R(p) value is 0.041.
Acta Crystallographica Section B Structural Science 07/2001; 57(Pt 3):372-7. · 2.29 Impact Factor
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ABSTRACT: The crystal structures of two dyestuffs, Na(+).C(11)H(8)N(3)O(2)(-).H(2)O, (I), and NH(4)(+).C(10)H(5)N(2)O(5)(-), (II), were determined from X-ray powder diffraction data. In both structures, translationally related anions form stacks, and cations fill interstack channels. A comparison of the diffuse reflectance spectra of crystalline (I) and (II) with the absorption spectra of their aqueous solutions demonstrates that the geometry of their anions does not change significantly upon transfer from the crystalline to the solution state.
Acta Crystallographica Section C Crystal Structure Communications 05/2001; 57(Pt 4):397-9. · 0.52 Impact Factor
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ABSTRACT: The crystal structures of two intercalated compounds have been determined using a combination of synchrotron powder diffraction and molecular mechanics simulations: (1) vanadyl phosphate intercalated with tetrahydrofuran, VOPO(4).(CH(2))(4)O, and (2) vanadyl phosphate intercalated with diethylene glycol, VOPO(4).HO(CH(2))(2)O(CH(2))(2)OH. Both intercalates preserve the tetragonal space group P4/n, as found in the host structure VOPO(4).2H(2)O. (1): a = 6.208, c = 8.930 A, Z = 2, D(x) = 2.51 g cm(-3); (2): a = 6.223, c = 11.417 A, Z = 2, D(x) = 2.66 g cm(-3). Both intercalates exhibit the same type of orientational disorder in the arrangement of guest molecules, as observed in the same host compound intercalated with water. These two intercalates also exhibit, rather surprisingly, perfect ordering in layer stacking without the displacement disorder, characteristic of many intercalated layered structures. Thanks to this regularity in the arrangement of guests and layers, synchrotron powder diffraction could be used in the present structure determination. The present results also enabled the analysis of the effect of geometrical parameters characterizing the mutual host-guest complementarity and the effect of host-guest and guest-guest interaction on the crystal packing of intercalates.
Acta Crystallographica Section B Structural Science 05/2001; 57(Pt 2):178-83. · 2.29 Impact Factor
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ABSTRACT: The crystal structures of 4-(phenyldiazenyl)naphthalen-1-amine, C(16)H(13)N(3), (I), and its hydrochloride, (4-aminonaphthalen-1-yl)phenyldiazenium chloride, C(16)H(14)N(3)(+) x Cl(-), (II), have been determined from X-ray single-crystal and powder data, respectively. The effect of the crystal environment on the molecular electronic structure was analysed on the AM1 level. One of the two symmetry-independent molecules in (I) is involved in intermolecular hydrogen bonding, so that its dipole moment is twice as large as that of the other molecule. The cations in (II) form stacks along [100], with the Cl(-) anions forming hydrogen bonds to all three H atoms attached to N atoms.
Acta Crystallographica Section C Crystal Structure Communications 04/2001; 57(Pt 3):295-7. · 0.52 Impact Factor
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ABSTRACT: A synthesis of the bicyclo[2.1.1]hexane substructure of solanoeclepin A (1), the most active natural hatching agent of potato cyst nematodes, was approached via an intramolecular [2 + 2] photocycloaddition. Aldehyde 12 containing the dioxenone chromophore served as a useful starting material, allowing the synthesis of a variety of photocycloaddition substrates via Grignard addition or via a Nozaki-Hiyama-Kishi reaction. Photolysis of the unsubstituted alkene 14 led to the expected crossed cycloadduct bicyclo[2.1.1]hexane 15 according to the so-called rule of five. However, several functionalized alkenes 18, 20, and 31 exhibited a complete reversal of cycloaddition regioselectivity, providing straight cycloadducts bicyclo[2.2.0]hexanes 21-26 and 4, respectively. Their structures were proved by a combination of extensive NMR measurements, X-ray analyses, and subsequent retro-aldol reactions. The latter de Mayo process allowed the formation of spiro-[3.5]nonane 35 and spiro[3.4]octane 36 as well as the cyclobutanes 37 and 38. Finally, the cyclization of the more rigid lactone precursor 28 occurred in high yield in the desired fashion with complete regio- and stereoselectivity to give 3 containing the core bicyclo[2.1.1]hexane skeleton of the natural product.
The Journal of Organic Chemistry 02/2001; 66(1):233-42. · 4.45 Impact Factor
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ABSTRACT: In order to correlate the reactivity and molecular structures of dithiocarbamates, the crystal structures of 6-dimethylamino-5-nitropyrimidin-4-yl N,N-diethyldithiocarbamate, C11H17N5O2S2, (Ia), and 6-methylamino-5-nitropyrimidin-4-yl N,N-diethyldithiocarbamate, C10H15N5O2S2, (Ib), and of the product of thermolysis of (Ib), namely 4-diethylamino-6-methylamino-5-nitropyrimidinium chloride monohydrate, C9H16N5(O2)(+).Cl(-).H2O, (II), have been determined from X-ray laboratory powder diffraction data. Conformational preferences in (Ia) and (Ib) were studied on the density functional theory (DFT) level. Deviation of the reaction centre of the molecule from planarity and breakage of the secondary S...O contact cause switching between two alternative pathways of thermolysis.
Acta Crystallographica Section C Crystal Structure Communications 02/2001; 57(Pt 1):72-5. · 0.52 Impact Factor
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ABSTRACT: The crystal structures of the beta' phase of CLC (1, 3-didecanoyl-2-dodecanoylglycerol) and MPM (1, 3-ditetradecanoyl-2-hexadecanoylglycerol) have been determined from single-crystal X-ray diffraction and high-resolution X-ray powder diffraction data, respectively. Both these crystals are orthorhombic with space group Iba2 and Z = 8. The unit-cell parameters of beta'-CLC are a = 57.368 (6), b = 22.783 (2) and c = 5.6945 (6) A and the final R value is 0.175. The unit-cell parameters of beta'-MPM are a = 76.21 (4), b = 22.63 (1) and c = 5.673 (2) A and the final R(p) value is 0.057. Both the beta'-CLC and beta'-MPM molecules are crystallized in a chair conformation, having a bend at the glycerol moiety. The zigzag planes of the acyl chains are orthogonally packed, as is typical for a beta' phase. Furthermore, unit-cell parameters of some other members of the C(n)C(n+2)C(n)-type triacylglycerol series have been refined on their high-resolution X-ray powder diffraction pattern. Finally, the crystal structures are compared with the currently known structures and models of triacylglycerols.
Acta Crystallographica Section B Structural Science 01/2001; 56 ( Pt 6):1103-11. · 2.29 Impact Factor
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I J De Esch,
R C Vollinga,
K Goubitz, H Schenk,
U Appelberg,
U Hacksell,
S Lemstra,
O P Zuiderveld,
M Hoffmann,
R Leurs,
W M Menge,
H Timmerman
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ABSTRACT: Various approaches to the synthesis of all four stereoisomers of 2-(1H-imidazol-4-yl)cyclopropylamine (cyclopropylhistamine) are described. The rapid and convenient synthesis and resolution of trans-cyclopropylhistamine is reported. The absolute configuration of its enantiomers was determined by single-crystal X-ray crystallographic analysis. The distinct trans-cyclopropylhistamine enantiomers were tested for their activity and affinity on the histamine H3 receptor. (1S,2S)-Cyclopropylhistamine (VUF 5297) acts as an agonist both on the rat cortex (pD2 = 7.1; alpha = 0.75) and on guinea pig jejunum (pD2 = 6.6; alpha = 0.75). Its enantiomer, (1R, 2R)-cyclopropylhistamine (VUF 5296), is about 1 order of magnitude less active. Both enantiomers show weak activity on H1 and H2 receptors. All synthetic attempts to cis-cyclopropylhistamine were unsuccessful. Nevertheless, the results of this study provide an ideal template for molecular modeling studies of histamine H3 receptor ligands.
Journal of Medicinal Chemistry 05/1999; 42(7):1115-22. · 5.25 Impact Factor
