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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 75 (1989), S. 233-245 
    ISSN: 1432-2234
    Keywords: p-t- Butylcalix(4)arene ; Conformation ; Complex ; Inclusion ; MO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Theoretical investigation of the conformations of p-t-butylcalix(4)arene and its toluene complex were carried out. The hydrogen bonding potential function suitable for the cyclic hydrogen bonds of calix(4)arene was obtained by least-squares fitting to the ab initio MO calculation results. It was found that the calix(4)arene has an enough flexibility for the complexation with molecules a little larger than the pore composed of the t-butyl groups; the complex formation does not need any activation energy. During the complex formation, the conformational changes of the calix(4)arene are small. Contribution of the dispersion interaction to the complexation energy is predominant. The cyclic hydrogen bond may not induce the allosteric effect at the binding site.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The parameters for an empirical point charge calculation method, Mulliken Population Constrained Potential Derived-Modified Partial Equalization of Orbital Electronegativity (MPCPD-MPEOE) method, for hypervalent sulfur, phosphorus, and the atoms bonded to these atoms, were determined. A new empirical method, MPCPD, which has inherent advantages over both the Mulliken population and potential derived methods, is proposed here. The MPCPD net atomic charges are transferable and reproduce the electrostatic potential. The electrical properties were calculated with the MPCPD and MPCPD-MPEOE charges. These properties agreed well with experimental results and with 6-31G** ab initio results. The MPEOE parameters for the sulfur atom in aromatic molecules and trivalent phosphorus in phosphite molecules were also determined. The dipole moments calculated with the MPCPD-MPEOE point charges agreed well with experimental results. All the parameters obtained in this work are consistent with those obtained in our previous work. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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