Cl···Cl interactions in molecular crystals: Insights from the theoretical charge density analysis. Journal of Physical Chemistry A Volume 117, Issue 35, 5 September 2013, Pages 8459-8467

The structure, IR harmonic frequencies and intensities of normal vibrations of 20 molecular crystals with the X-Cl···Cl-X contacts of different types, where X = C, Cl, and F and the Cl···Cl distance varying from ∼3.0 to ∼4.0 Å, are computed using the solid-state DFT method. The obtained crystalline wave functions have been further used to define and describe quantitatively the Cl·· ·Cl interactions via the electron-density features at the Cl···Cl bond critical points. We found that the electron-density at the bond critical point is almost independent of the particular type of the contact or hybridization of the ipso carbon atom. The energy of Cl···Cl interactions, Eint, is evaluated from the linking Eint and local electronic kinetic energy density at the Cl···Cl bond critical points. E int varies from 2 to 12 kJ/mol. The applicability of the geometrical criterion for the detection of the Cl···Cl interactions in crystals with two or more intermolecular Cl···Cl contacts for the unique chlorine atom is not straightforward. The detection of these interactions in such crystals may be done by the quantum-topological analysis of the periodic electron density.
Indexed keywords
Bond critical points; Carbon atoms; Charge-density analysis; Chlorine atom; DFT method; Electronic kinetic energy; Harmonic frequency; Normal vibrations