IQA-embedded fragment attributed molecular system energy change in exploring intramolecular interactions

Abstract

hydrogens, they (i) do not conform to steric clash, (ii) resemble stabilizing interactions in Henand Hea and (iii) follow changes in physical properties (on interaction formation) found for heteroatoms in Hen and Hea (opposite was found for O-atoms in gc). Moreover, the mol-FAMSEC term (i) accounts to some extent, although indirectly, for the geometric deformation energy of all atoms not involved in the intramolecular interaction, (ii) equally applies to any kind of (de)stabilizing or QTAIM (non)bonded interaction, and (iii) can equally be used for any size of a molecular fragment (e.g. functional groups) as well as for intermolecular interactions.

Origin of Hydrocarbons Stability from a Computational Perspective: A Case Study of Ortho‐Xylene Isomers

“…The H11/H12 molecular fragment has made an energy contribution of stabilizing nature to the in‐in conformer with mol ‐FAMSEC=−3.8 kcal/mol (Figure a) and this is the largest (most negative) contribution made among all unique (153) 2‐atom fragments. It must be finally noticed, in line with the above observations, that at present time intra‐molecular CH⋅⋅⋅HC in planar biphenyl are also found attractive in the recent works based on the powerful methods IQA, FAMSEC, IQA/REG and pioneering QTAIM as opposed to the repulsive text‐book interpretation favoured till now only in Ref [15d].…”

“…An intriguing and of general importance a fundamental question arises at this point – namely, are intra‐molecular CH⋅⋅⋅HC dihydrogen interactions attractive in relatively small organic molecules? It has been recently demonstrated, using various bonding descriptors, that the lower stability of the cis ‐2‐buthene vs. trans ‐2‐buthene is rooted in the destabilization of the ‘bottom’ ethylenic CH=CH fragment, contrary to the classical intuitive interpretation based on the ‘top’ CH⋅⋅⋅HC steric‐repulsion . Remarkably, we have also discovered the CH⋅⋅⋅HC stabilization in trans ‐2‐butene, which is formed between C−H bonds of the methyl and ethylenic units.…”

Non-Covalent Interactions in Hydrogen Storage Materials LiN(CH3)2BH3 and KN(CH3)2BH3

“…Further Valence Bond studies have revealed [78], in line with our conclusions, that, apart from the crucial dispersion term, also the σ/σ*(C-H) polarization/charge transfer and electrostatic contributions are important. Recently, numerous reports are present in the literature on the stabilizing nature of CH¨¨¨HC interactions in various types of hydrocarbons [37,38,[79][80][81][82][83][84][85], as well as their importance in catalysis [42,43,86].…”

“…It is noteworthy that these types of connections are intuitively considered as destabilizing due to the lack of electrostatic attraction between hydrogen atoms-homopolar dihydrogen interactions (especially the intramolecular ones) are still a matter of debate in the literature [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Very recently more and more evidence has been reported in the literature that highlight the stabilizing nature of homopolar dihydrogen interactions [17,21,29,[36][37][38][39][40][41][42][43][44][45][46]. Accordingly, in this work we provide complementary results which shed light on energetic, quantitative and qualitative characteristics of non-covalent interactions that contribute to the stability of LiN(CH3)2BH3 and KN(CH3)2BH3 crystals.…”

Toward deformation densities for intramolecular interactions without radical reference states using the fragment, atom, localized, delocalized, and interatomic (FALDI) charge density decomposition scheme

“…[9][10][11][12][13] Conversely, investigations into the nature of known interactions have also led to the discovery of new interactions which might be of interest to chemists, such as halogen bonding, [14][15][16] anion-anion interactions, [17] and chalcogen bonds. Many of these can be classified as decomposition and transformation of (i) the molecular energy, including FAMSEC, [29] EDA, [30] ETS, [31] IQA, [32] and SAPT, [33] or (ii) the molecular charge density distribution, including QTAIM, [34] FMO, [35] NBO, [36] NCI, [37] and NOCV. Specifically, despite many excellent treatises on the physical events on bond formation, [28] there is still a scientific need to shed more light on the nature of many intramolecular interactions commonly found in experimental conditions, and how a network of intramolecular interactions contributes to the chemical properties and reactivity of a molecular system.…”