Noncovalent Interactions in Crystalline Picolinic Acid N‑Oxide: Insights from Experimental and Theoretical Charge Density Analysis

This study provides a detailed description of noncovalent
interactions
of different types and strengths in the title crystal using a combined
experimental and theoretical study of the charge density distribution.
The nature of the noncovalent interactions is visualized using information
theory and through the superposition of the gradient fields in the
electron density and electrostatic potential. The energy of the intramolecular
O–H···O bond, intermolecular C–H···O
bonds, and π-stacking interactions, Eint, are evaluated from empirical correlations between Eint and geometrical and electron-density bond critical
point parameters. The complete set of noncovalent interactions including
the strong intramolecular O–H···O (Eint > 90 kJ/mol) and weak C–H···O
(Eint < 10 kJ/mol) hydrogen bonds,
and π-stacking interactions (Eint < 4 kJ/mol) is quantitatively described. The results from the
experimental charge density analysis are compared with periodic quantum
calculations using density functional theory with the Grimme dispersion
correction. It was found that the Grimme dispersion correction did
not provide a good simultaneous description of both weak and strong
noncovalent interactions in the studied crystal. It is shown that
the obtained energies of noncovalent interactions lead to a reasonable
value of the lattice energy. The latter is treated as the total intermolecular
interaction energy.