Estimating the energy of intramolecular hydrogen bonds from¹H NMR and QTAIM calculations

Abstract

The values of the downfield chemical shift of the bridge hydrogen atom were estimated for a series of compounds containing an intramolecular hydrogen bond O-HO, O-HN, O-HHal, N-HO, N-HN, C-HO, C-HN and C-HHal. Based on these values, the empirical estimation of the hydrogen bond energy was obtained by using known relationships. For the compounds containing an intramolecular hydrogen bond, the DFT B3LYP/6-311++G(d,p) method was used both for geometry optimization and for QTAIM calculations of the topological parameters (electron density ρ and the density of potential energy V in the critical point of the hydrogen bond). The calculated geometric and topological parameters of hydrogen bonds were also used to evaluate the energy of the hydrogen bond based on the equations from the literature. Comparison of calibrating energies from the H NMR data with the energies predicted by calculations showed that the most reliable are the linear dependence on the topological ρ and V parameters. However, the correct prediction of the hydrogen bond energy is determined by proper fitting of the linear regression coefficients. To obtain them, new linear relationships were found between the calculated ρ and V parameters and the hydrogen bond energies obtained from empirical H NMR data. These relationships allow the comparison of the energies of different types of hydrogen bonds for various molecules and biological ensembles.

Hybrid organic–inorganic CH3NH3PbI3perovskite building blocks: Revealing ultra‐strong hydrogen bonding and mulliken inner complexes and their implications in materials design

“…The theoretical details of QTAIM have numerously been discussed [27a,84,114,118,122–124] . Its application to the CH 3 NH 3 PbI 3 molecular blocks have resulted in molecular graphs that are illustrated in Figure .…”

Intramolecular hydrogen bond directed stable conformations of benzoyl phenyl oxalamides: unambiguous evidence from extensive NMR studies and DFT-based computations

“…The energies of the HBs (E HB ) for all of the studied molecules were calculated using an empirical relationship E HB ¼Dd + (0.4 AE 0.2) (kcal mol À1 ), [63][64][65] where Dd is the difference in the chemical shis of the hydrogen bonded and free proton. Dd in the present work was derived by subtracting the resonance frequency of the NH proton of molecule 1 from the NH resonance frequencies of the molecules, 2-6, and the E HB values, calculated using the above relationship, are compiled in Table 3.…”

Exploring Nature and Predicting Strength of Hydrogen Bonds: A Correlation Analysis Between Atoms‐in‐Molecules Descriptors, Binding Energies, and Energy Components of Symmetry‐Adapted Perturbation Theory

“…One of the most well‐known theoretical tools to reveal inter‐ and intramolecular interactions together with their strengths is Bader's quantum theory of atoms in molecules (QTAIM) . Within QTAIM, the electron density as well as other real space functions such as energy density and the Laplacian of electron density at the so‐called bond critical point (BCP) of the HB interaction of interest can be comprehensively analyzed . For fully characterizing HB interactions, many other indices or descriptors have also been proposed, for instance, the core‐valence bifurcation (CVB) index defined based on the electron localization function (ELF) and the ΔΔ V n index defined by the molecular electrostatic potential (MEP) at nuclear positions …”