Intermolecular hydrogen bond energies in crystals evaluated using electron density properties: DFT computations with periodic boundary conditions

The hydrogen bond (H‐bond) energies are evaluated for 18 molecular crystals with 28 moderate and strong O? H···O bonds using the approaches based on the electron density properties, which are derived from the B3LYP/6‐311G** calculations with periodic boundary conditions. The approaches considered explore linear relationships between the local electronic kinetic G_b and potential V_b densities at the H···O bond critical point and the H‐bond energy E_HB. Comparison of the computed E_HB values with the experimental data and enthalpies evaluated using the empirical correlation of spectral and thermodynamic parameters (Iogansen, Spectrochim. Acta Part A 1999 , 55, 1585) enables to estimate the accuracy and applicability limits of the approaches used. The V_b?E_HB approach overestimates the energy of moderate H‐bonds (E_HB < 60 kJ/mol) by ～20% and gives unreliably high energies for crystals with strong H‐bonds. On the other hand, the G_b?E_HB approach affords reliable results for the crystals under consideration. The linear relationship between G_b and E_HB is basis set superposition error (BSSE) free and allows to estimate the H‐bond energy without computing it by means of the supramolecular approach. Therefore, for the evaluation of H‐bond energies in molecular crystals, the G_b value can be recommended to be obtained from both density functional theory (DFT) computations with periodic boundary conditions and precise X‐ray diffraction experiments. © 2012 Wiley Periodicals, Inc.