Abstract
The quantum-chemical semiempirical PM3 method was used for the calculation of the energies of formation of 37 inclusion complexes of cyclodextrins (CDs) with arenes and other substrates of the composition 1 : 1, for which the experimental thermochemical data are known. The linear correlation was found between the energies of formation of the complexes of monosubstituted naphthalenes with CDs and the experimental values of the change in the Gibbs energy. In the analysis of the geometries of all optimized complexes, short contacts with a length of 1.75 ± 0.08 Å were found between the intracavity hydrogen atoms of CDs and the hydrogen atoms of the guest molecules. It was found that in all 37 cases the most energetically favorable structures of the complexes were those with the maximum number of these contacts. Comparison of the structures optimized by PM3 calculations with the data of X-ray diffraction analysis and results of DFT calculations demonstrated that such short distances between the covalently nonbonded hydrogen atoms are due to drawbacks in the PM3 parametrization; in the native structures and complexes calculated by the DFT method, the lengths of the H⋯H contacts are 2.3-2.4 Å.
Original language | English |
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Pages (from-to) | S28-S32 |
Journal | Russian Journal of Physical Chemistry A |
Volume | 79 |
Issue number | SUPPL.1 |
State | Published - 2005 |
Externally published | Yes |