On the Uselessness of Bond Paths Linking Distant Atoms and on the Violation of the Concept of Privileged Exchange Channels

Abstract

We refer to frequently used determinants suggesting dominant interactions between distant atoms in various dimers. First of all, we show, against the still-prevailling opinion, that, in general, bond paths have nothing in common with dominant intermolecular interactions and therefore they are useless in such cases. Quite the contrary, reliable information about dominant intermolecular interactions can be obtained by means of electrostatic potential maps, which very convincingly explain mutual orientation of molecules in a dimer. For the first time, numerous examples of interactions that violate both the concept of privileged exchange channels proposed by Pendás and his collaborators as well as inequalities obtained by Tognetti and Joubert for the β parameter related to secondary interactions are presented. The possible cause of this violation is suggested. We also show that the so-called counterintuitive bond paths result from quite natural behavior of the electron density gradient vector, i. e. searching for those areas of space that are characterized by large values of electron density or the most expanded its distributions.[a] Dr.

Nature of the Interaction of Pyridines with OCS. A Theoretical Investigation

“…Table 3 reports the different parameters obtained from an AIM analysis. Let us observe that the AIM results have been questioned for weak interactions [52]. The results of the present work show that the AIM parameters are well correlated with other parameters describing the nature of the interaction (see further discussion).…”

Cooperativity in alkane‐1,2‐ and 1,3‐polyols: NMR, QTAIM, and IQA study of O─H…OH and C─H…OH bonding interactions

“…There is an ongoing controversy about the use of the word “bond” in the context of QTAIM analysis, with particular reference to the terms “bond path” and “bond critical point.” 64, 79, 85–87 It has been proposed that a more equivocal expression such as “line path” be used to avoid the suggestion that a BP represents a bond 85, 86 . Bader affirms that a BP is not to be understood as representing a chemical bond between the two atoms concerned: BCPs and BPs evidence “hydrogen bonding” rather than “hydrogen bonds.” 79 However, the subtle theoretical and grammatical distinction between these two expressions is not generally respected and even the International Union of Pure and Applied Chemistry Technical Report, “Defining the hydrogen bond,” uses them synonymously 88 .…”

“…There is an empirical relationship between the existence of a BCP and the relative interaction energies of competing exchange channels 54, 62, 63 . Although ethane‐1,2‐diol fails to meet the criterion for a BCP, 56, 61 it is still interesting to see how this approach applies to 1,2‐diol motifs in general, despite recent criticism 64 . Our idea, therefore, was to compare alkane‐1,2‐ and 1,3‐polyols, based on a single repeated conformer unit, to establish the main features of cooperativity in the latter and to examine the differences between hydrogen bonding interactions in these two systems.…”

Metal–Halogen Bonding Seen through the Eyes of Vibrational Spectroscopy

“…Considering the problem of finding bond paths connecting electron-rich regions instead of reflecting dominant interactions [53,54], the topological electron density analysis was complemented by electron difference densities. To distinguish an atom-atom interaction from a dispersive/electrostatic interaction involving multiple atoms, termed here nonspecific (NS), we calculated and analyzed reduced density gradient (RDG) iso-surfaces of 0.45 a.u., colored according to the value of the second largest eigenvalue of the electron density Hessian, also termed non-covalent index (NCI) [104].…”

“…However, the sole existence of a bond path and a BCP does not necessarily imply the existence of a chemical bond [52]. For distant atoms, bond paths may favor a connection between electron-rich regions instead of reflecting dominant interactions, making the interpretation of bond paths as bond indicators and the use of the density at the BCP as bond strength measure problematic [52][53][54]. The same holds for bond strength measures derived from dissociation energies (BDE)s [55][56][57][58][59][60] and molecular geometries.…”