An anatomy of intramolecular atomic interactions in halogen-substituted trinitromethanes

Abstract

The intramolecular interactions in substituted trinitromethanes, XC(NO2)3 (X = F, Cl, I, H) are studied and clarified by using a combination of the Quantum Theory of Atoms in Molecules (QTAIM), the non-covalent interaction analysis and the Interacting Quantum Atoms (IQA) methods. The stretching vibration modes are formed by the concerted displacements of atoms involved in the covalent bonds showing the significant multiatomic influence in substituted trinitromethanes. In agreement with that, the arrangement of the local reduced density gradient minima indicates that the electron density favors the non-covalent intramolecular interactions X···O and N···O. However, the corresponding QTAIM bond paths are not formed; instead, contacts, which we call uncompleted links in this context, are accompanied by "quasi-bonding channels" corresponding to the λ2() ≤ 0 regions on the sign[λ2(r)]ρ(r) contour maps. The intramolecular IQA energy contributions signal the appreciable electron exchange between the pairs of atoms associated with potential atomic interactions or the bond-path-free non-covalent links. The IQA analysis shows that the electrostatic term destabilizes FC(NO2)3 and distinctly stabilizes IC(NO2)3, whereas it is close to neutral in ClC(NO2)3. The exchange energy between the X atom and the NO2 groups, in contrast, stabilizes all the molecules.

Pentafluoroethyl-substituted α-silanes: model compounds for new insights

“…The RDG (s = 1/(2(3π 2 ) 1/3 )|∇ρ|/ρ 4/3 ) together with its derivative is one of essential quantities in DFT theory. 40 The RDG analysis has been applied to compounds 1-4. 35,37 Regions of low RDG values are associated with either attractive or repulsive interactions depending on the sign of the second eigenvalue λ 2 of the electron-density Hessian (matrix of second derivatives).…”

Interplay between non-covalent interactions in complexes and crystals with halogen bonds

“…This compound has a very short carbon7chlorine bond in the crystal [1.694(1) # A], its nature was studied 238 from the standpoint of specific features of the electrostatic potential. An analysis 239 of the regions of localization of the NCI isosurfaces and RDG(r)7sign[l 2 (r)]r (r) plots revealed the following (Fig. 17).…”

“…Structure of chlorotrinitromethane dimer with the NCI minima regions specified to a contour corresponding to RDG(r) = 0.6 (a), RDG(r)7sign[l2(r)]r(r) plot (b) and a superposition of the electron density map and regions corresponding to minima of the RDG(r) function (c). 239 The letters A, B and C denote the spikes obtained in different representations.…”

A multipolar approach to the interatomic covalent interaction energy

“…16,17 For instance, it has been shown to be intimately related to the appearance of the bond critical points of the QTAIM, leading to the concept of priviledged exchange-correlation channels. 18 It has also been used to reconstruct molecular graphs from purely energetic quantities, 19 to shed light on new concepts like halogen bonding, 20,21 to recover stereolectronic effects, 22 or to find new longrange electronic anomalies. 23 Interatomic V xc energies are intimately linked to the delocalization or shared electron delocalization indices (DIs) used in the QTAIM, defined almost 40 years ago by Bader and Stephens.…”