Change with the Intermolecular Distance of Electron Properties of Hydrogen Bond Dimers at Equilibrium and Non-equilibrium Geometries

Abstract

The change with the intermolecular distance R of a number of electron properties obtained from the electron density ρ(r) and the electron localization function η(r) along with some selected structural features is investigated for seven dimers linked by conventional hydrogen bonds (HBs). Five nonequilibrium geometries apart from the equilibrium one are optimized in MP2/6-311++G(d,p) ab initio calculations for every dimer. The variation with R of topological descriptors and integrated properties computed from ρ(r) and η(r) reveals that not only features characteristics of hydrogen bonding are still noticed inside the equilibrium distance R eq but the sign and magnitude of HB trends are kept at R < R eq . Only at the shortest intermolecular distances where dramatic structural changes occur, these trends revert their direction although in most cases HB characteristics are still noticed.

F–H⋯F–C hydrogen bonds – The influence of hybridization of carbon atom connected with F-acceptor on their properties

“…This dependence is similar to the geometrical one between the D-H bond length and HÁ Á ÁA distance, however, the correlation is slightly better for topological parameters. The latter finding is in agreement with the previous studies since it was found that the topological parameters better correlate among themselves and with H-bond energy than the geometrical ones [29,32,33].…”

“…The characteristics of HÁ Á ÁA bond critical points (BCPs) are the most often applied topological parameters [33]. It was found that the electron density at HÁ Á ÁA BCP (q HÁ Á ÁA ) and also its Laplacian ($ 2 q HÁ Á ÁA ) often well correlate with H-bond energy [17,29].…”

Relationships between Interaction Energy and Electron Density Properties for Homo Halogen Bonds of the [(A)nY–X···X–Z(B)m] Type (X = Cl, Br, I)

“…Experimental determination of E XB is usually associated with significant technical issues [38,39], while its direct theoretical calculations are not always possible or reliable (e.g., for the intramolecular XBs or molecular associates involving several non-covalent interactions, Watson-Crick base pairs being among them). One of the most attractive and sometimes the only possible methods of the approximate express estimate of the bond energy for weak interactions is the application of appropriate E XB (property) correlations [40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87]. This method has got an impulse after the publication of an article by Espinosa, Molins, and Lecomte [88].…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 16, 2005) and the discipline

“…Pacios [82] investigated the change with the intermolecular distance R of electron properties obtained from the electron density and the electron localization function along with some selected structural features for seven dimers linked by conventional hydrogen bonds at equilibrium and non-equilibrium geometries. The variation with the intermolecular distance R of electron properties of topological descriptors and integrated properties reveals that not only features characteristics of hydrogen bonding are still noticed inside the equilibrium distance R eq but the sign and magnitude of hydrogen bonds trends are kept at R \ R eq .…”