Do surfaces of positive electrostatic potential on different halogen derivatives in molecules attract? like attracting like!

Abstract

Coulomb's law states that like charges repel, and unlike charges attract. However, it has recently been theoretically revealed that two similarly charged conducting spheres will almost always attract each other when both are in close proximity. Using multiscale first principles calculations, we illustrate practical examples of several intermolecular complexes that are formed by the consequences of attraction between positive atomic sites of similar or dissimilar electrostatic surface potential on interacting molecules. The results of the quantum theory of atoms in molecules and symmetry adapted perturbation theory support the attraction between the positive sites, characterizing the F•••X (X = F, Cl, Br) intermolecular interactions in a series of 20 binary complexes as closed-shell type, although the molecular electrostatic surface potential approach does not (a failure!). Dispersion that has an r dependence, where r is the equilibrium distance of separation, is found to be the sole driving force pushing the two positive sites to attract. © 2017 Wiley Periodicals, Inc.

Nature of halogen‐centered intermolecular interactions in crystal growth and design: Fluorine‐centered interactions in dimers in crystalline hexafluoropropylene as a prototype

“…The M06‐2X binding energies Δ E for the dimers range from −2.30 to −27.45 kJ mol −1 (Table ). This range of Δ E values suggests that the intermolecular interactions between the monomers in (C 3 F 6 ) 2 are both of weak‐to‐moderate strength and of van der Waals type . Weak‐to‐moderate interactions have been known to have binding energies in the 15–60 kJ mol −1 range, whereas van der Waals interactions are very weak with Δ E ~4 kJ mol −1 …”

“…There is an on‐going debate as to whether the presence of (3,−1) bcps, as revealed by QTAIM, are always indicative of bonding interactions especially pertaining to attraction between atomic sites. As such, the reliability of QTAIM signatures has been criticized, even though bcps, together with other descriptors, do indeed describe chemical bonding in many counterintuitive instances . Chemical bonding mainly emerges from a pair of atoms that are linked with each other, and ring and cage critical points only provide insight into the nature and possibility of ring opening and closing, and the compactness of the entire molecular graph and the stability.…”

“…This is the case in cases such as H 3 CF, C 6 H 5 F, and H 3 COF, in which V s,max on F were found to be −25, −16, and −10 kcal mol −1 , respectively. Accordingly, these fluorines do have σ‐holes.” So, the negative indicator of the potential V s,max on F means the fluorine atoms in these systems do have negative σ‐holes; this is analogous to the way they have positive σ‐holes in other molecules …”

“…This does not, however, require that an electron density deficient region is/would be always positive. In fact, it could be negative as well …”

“…Interactions involving a type‐II (geometric) topology of bonding, but do/do not involve a positive site, could be referred to as type‐III halogen–halogen bonding . In fact, this terminology is specifically applicable to interactions formed between two atomic sites of similar or dissimilar electrostatic potential in interacting monomer molecules in which the interacting sites conceive σ‐holes that are either both positive or both negative . Also, the angle θ 2 is close to that of type‐II (as in the (C 6 F 6 ) 2 dimer) …”