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  • 1
    Electronic Resource
    Electronic Resource
    Modeling in Structure Analysis of Vanadyl Phosphate Intercalated with 1-Alkanols (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 9-15 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Vanadyl phosphate-alkanol intercalates, Molecular mechanics, Structure analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulations supported by X-ray powder diffraction measurements have been used to investigate the structure of vanadyl phosphate intercalated with 1-alkanols CnH2n+1OH for n = 2, 3, 4. Modeling revealed the specific features and differences in arrangement of alkanol molecules with different chain length, depending on the relation between the parameters of active sites network and size of guest molecules. This result enabled us to explain the irregularities in dependence of basal spacing on the chain length. The comparison of experimental dexp and calculated dcalc values of basal spacing showed the good agreement of modeling with x-ray powder diffraction. While we obtained dcalc(Univ) = 13.05 Å for vanadyl phosphate-ethanol using the Universal force field (dexp=13.17 Å), for vanadyl phosphate-propanol and vanadyl phosphate-butanol better agreement with experiment was obtained using the Tripos force field. In the case of vanadyl phosphate-propanol the calculated basal spacing dcalc(Tripos) = 14.49 Å, compared with an experimental value of dexp=14.36 Å. For vanadyl phosphate-butanol dcalc(Tripos) = 17.71 Å and dexp=17.90 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010722
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  • 2
    Electronic Resource
    Electronic Resource
    Montmorillonite and Beidellite Intercalated with Tetramethylammonium Cations (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 600-607 
    Details
    ISSN: 0948-5023
    Keywords: Intercalated clays ; Tetramethylammonium-clays ; Modeling ; Molecular mechanics ; Montmorillonite ; Beidellite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulations, combined with X-ray powder diffraction and infrared spectroscopy, have been used in structure analysis of montmorillonite and beidellite intercalated with tetramethylammonium cations. A complex structure analysis provided us with the detailed structure model, including characterization of the disorder, the total sublimation energy and a charge distribution in the structure of intercalates. The calculated basal spacings (14.36 Å for TMA-montmorillonite and 14.12 Å for TMA-beidellite) are in good agreement with the experimental values (14.31 Å for TMA-montmorillonite and 14.147 Å for TMA-beidellite). Both intercalated structures exhibit positional and orientational disorder in the arrangement of TMA cations, and consequently disorder in layer-stacking. In the present work we analyse the effect of octahedral and tetrahedral substitutions in a 2:1 silicate layer on the arrangement of tetramethylammonium (TMA) cations in the interlayer space of montmorillonite and beidellite. The most significant difference between TMA-montmorillonite and TMA-beidellite is in the charge distribution on the TMA cations and silicate layer. The TMA-beidellite structure is highly polarized, the total charge on one TMA cation is +0.167 e−, while the total charge on the TMA cation in montmorillonite is +0.050 e−.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089400060600
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  • 3
    Electronic Resource
    Electronic Resource
    Structure determination of two intercalated compounds VOPO4·(CH2)4O and VOPO4·OH—(CH2)2—O—(CH2)2—OH; synchrotron powder diffraction and molecular modelling (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 178-183 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: 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, VOPO4·(CH2)4O, and (2) vanadyl phosphate intercalated with diethylene glycol, VOPO4·HO(CH2)2O(CH2)2OH. Both intercalates preserve the tetragonal space group P4/n, as found in the host structure VOPO4·2H2O. (1): a = 6.208, c = 8.930 Å, Z = 2, Dx = 2.51 g cm−3; (2): a = 6.223, c = 11.417 Å, Z = 2, Dx = 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768100015603
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of aromatic sulfonation on the geometry of [2.2]paracyclophane: crystal structures of one sulfonate, one disulfonic anhydride and five disulfonimides (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 780-790 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: 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[8.2.2.24,7]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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768101013817
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