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

• Published in: Journal of computational chemistry Vol. 33; no. 29; pp. 2303 - 2309
• Main Authors: Vener, M. V., Egorova, A. N., Churakov, A. V., Tsirelson, V. G.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05.11.2012; Wiley Subscription Services, Inc
• Subjects: Analytical chemistry; Boundary conditions; Crystallization; Diffraction; electron-density analysis; Electrons; H-bond enthalpies/energies; harmonic frequencies and IR intensities; Hydrogen Bonding; Hydrogen bonds; Molecular chemistry; molecular crystals; Quantum Theory; Thermodynamics
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.23062

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 Gb and potential Vb densities at the H···O bond critical point and the H‐bond energy EHB. Comparison of the computed EHB 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 Vb−EHB approach overestimates the energy of moderate H‐bonds (EHB < 60 kJ/mol) by ∼20% and gives unreliably high energies for crystals with strong H‐bonds. On the other hand, the Gb−EHB approach affords reliable results for the crystals under consideration. The linear relationship between Gb and EHB 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 Gb 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. The absolute values of the local electronic kinetic Gb and potential Vb densities at the H···O bond critical point are essentially different for molecular crystals with R(H···O) < 1.70 Å. The EHB = −0.5Vb equation, where EHB is the H‐bond energy, gives unreliably high energies for strong H‐bonded crystals. The EHB = 0.429 Gb equation affords reliable results for molecular crystals with moderate and strong H‐bonds.