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 kineticG_band potentialV_bdensities at the H···O bond critical point and the H‐bond energyE_HB. Comparison of the computedE_HBvalues with the experimental data and enthalpies evaluated using the empirical correlation of spectral and thermodynamic parameters (Iogansen, Spectrochim. Acta Part A1999,55, 1585) enables to estimate the accuracy and applicability limits of the approaches used. TheV_b−E_HBapproach 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, theG_b−E_HBapproach affords reliable results for the crystals under consideration. The linear relationship betweenG_bandE_HBis 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, theG_bvalue 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.