The Nature of -Cl.cntdot..cntdot..cntdot.Cl- Intermolecular Interactions

Abstract

The controversy as to whether there is a specific attractive intermolecular force between chlorine atoms, of the charge-transfer or donor-acceptor type, is resolved using various analyses of experimental crystal structure data and theoretical calculations. The occurrence of Cl-Cl intermolecular contacts which are shorter than would be expected from the conventional isotropic van der Waals radius is shown to be most common in the crystal structures of fully or highly chlorinated hydrocarbons, and thus a consequence of close packing of anisotropic atoms, rather than evidence for a specific attractive force. Intermolecular perturbation theory calculations on the Cl-Cl interactions within the chloromethane dimer show that the charge-transfer contribution to the intermolecular energy is negligible, the electrostatic forces are weak, and the repulsive wall is anisotropic. Calculations on the electrostatic interactions between other chlorinated hydrocarbons show that these results will also apply to other Cl-Cl interactions. Thus a realistic anisotropic model for the repulsion, dispersion, and electrostatic forces between chlorinated hydrocarbons should be capable of predicting the observed crystal structures with "short" Cl-Cl intermolecular separations.

The shape of the halogen atom—anisotropy of electron distribution and its dependence on basis set and method used

“…Such a conclusion was drawn after the analysis of interatomic distances in crystals. Later, in 1994, Price et al [33] were investigating the nature of R1-ClÁÁÁCl-R2 interactions; on the basis of the analysis of ClÁÁÁCl distances in crystals and also on the basis of quantum-chemical calculations they concluded that such interactions were stabilizing, but what is particularly important, for the first time the phenomenon of anisotropic charge distribution around halogen nuclei was directly linked with the phenomenon of the ClÁÁÁCl noncovalent bonding. (Note that due to the same mechanism of formation, the ClÁÁÁCl interaction can be considered as a specific type of X-bonding; however, the term ''dihalogen bond'' is also often used for such type of interactions to distinguish them from typical X-bonds (e.g., R-XÁÁÁN,O) [34].…”

The Effects of Noncovalent Interactions on Surface Structures Formed by Diketopyrrolopyrrole Pigment and Its Alkyl-Derivatives on HOPG Substrate

“…32 The coadsorption model in this study is shown in Figure 3c. As a result of the coadsorption, weak solventsolute electrostatic interactions (CH arom £Cl) 33 function to stabilize the adsorbed structure in Type 2. Adsorption of the solvent molecules which occupy smaller surface area is estimated to be weaker than that of the pigment molecules.…”

Control of a two-dimensional molecular structure by cooperative halogen and hydrogen bonds

“…These polarizations are referred to as -hole and gives origin to halogen bonds. [9][10][11][12] On the other hand, two oxygen atoms in carboxyl group have negative electrostatic potential. Thus, positive regions of bromine atoms are able to electrostatically interact with the negative part of the oxygen atoms in carboxyl groups of neighbouring molecules, indicating the halogen bonds formation of Br … O=C and Br … OH.…”

“…[9][10][11][12] Typical bonding energies of hydrogen bonds are from 1 to 167 kJ/mol depending on their environment, 15 while halogen bonds are from 6 to 180 kJ/mol. [9][10][11][12][13][14] Although typical halogen bonds are relatively weak compared with hydrogen bonds, it has shown that, in some cases, the strength of halogen bonds can surpass classical hydrogen bonds, resulting in halogen bonds being the dominant driving force in the three-dimensional crystallization of organic molecules and the association of biological molecules. 16,17 From this viewpoint, using halogen bonds for assembling 2D molecular structures has advanced in recent years.…”