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  • 2000-2004  (4)
  • 1
    Electronic Resource
    Electronic Resource
    The calculation of 13C chemical shielding tensors in ionic compounds utilizing point charge arrays obtained from Ewald lattice sums (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 9236-9243 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An embedded ion method is proposed for accurately calculating the 13C chemical shift tensors in ionic compounds. The method models an ionic crystal by embedding an ion of interest inside an array of point charges. The potential, produced by an infinite ionic lattice, at the location of the ion of interest can be simulated accurately utilizing a point charge array obtained by the Ewald summation method. The Ewald summation method, as implemented in the computer program EWALD, in conjunction with the quantum-mechanics program GAUSSIAN 98 is used to generate a self-consistent point charge array that simulates the Ewald potential in a defined region at the center of the array. Subsequently, the chemical shift tensor calculation is performed using GAUSSIAN 98 on the ion of interest positioned in the region inside the point charge array in which the Ewald potential is established. The embedded ion method was tested on potassium methyl-trithiocarbonate (KS2CSCH3) whose crystal lattice is composed of potassium cations and molecular S2CSCH3− anions. The principal values of the 13C chemical shift tensors in KS2CSCH3 were measured in a stationary cross polarization nuclear magnetic resonance experiment. It is shown that the correlation between experimental and calculated principal values improves significantly when the C–H bond distances are optimized from their x-ray values. It is further demonstrated that a substantial improvement in the correlation is obtained when the chemical shielding tensor calculation is performed on an S2CSCH3− anion embedded inside a point charge array obtained by the Ewald summation method. The embedded ion method was completed applying the B3P86/cc-pVTZ, B3LYP/cc-pVTZ, and MP2/cc-pVDZ quantum-mechanical computations and the various results are compared and analyzed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356016
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  • 2
    Electronic Resource
    Electronic Resource
    cis-Verbenol (2000)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 451-452 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: cis-Verbenol (alternative name: 4,6,6-trimethylbicyclo[3.1.1]hept-3-en-2-ol), C10H16O, forms an orthorhombic P212121 crystal that contains three molecules per asymmetric unit. These three molecules form hydrogen-bonded helices parallel to the shortest axis of the lattice. The O...O distances associated with the hydrogen bonds are 2.760 (3), 2.760 (3) and 2.766 (3) Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010827019901570X
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  • 3
    Electronic Resource
    Electronic Resource
    10-Deacetyl baccatin III dimethyl sulfoxide disolvate (2001)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 64-65 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The title compound, C29H36O10·2C2H6OS, forms a monoclinic crystal containing two hydrogen-bonded dimethyl sulfoxide molecules per 10-deacetyl baccatin III. The lattice is further stabilized by two additional hydrogen bonds and a dipole–dipole interaction. A comparison of 10-deacetyl baccatin III with the structurally similar docetaxel reveals differences primarily in the benzoyl moiety, while comparisons to baccatin III identify relative differences principally in the cyclooctane- and cyclohexane-ring conformations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270100011781
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  • 4
    Electronic Resource
    Electronic Resource
    Terrein (2000)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. e570-e571 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The fungal metabolite terrein (alternative name: trans-2,3-dihydroxy-4-propenylcyclopent-4-enone), C8H10O3, forms monoclinic (P21) crystals. The molecules form hydrogen-bonded chains, with O...O distances of 2.7115 (16) and 2.8155 (15) Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270100014803
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