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

Abstract

A search through Crystal Structure Database was performed and the distances in contacts of XÁÁÁN,O, XÁÁÁH(N,O), and XÁÁÁC type were collected together with the information on spatial arrangement of the interacting fragments. A detailed statistical analysis showed that the shape of the halogen atom cannot be simply concluded on the basis of interatomic distances in crystal state although originally the concept of anisotropic charge distribution around halogen nuclei was postulated on the basis of such an analysis. It was proven that the conclusions in that case strongly depend on the type of center interacting with the halogen atom. Therefore, it was postulated that the shape of the halogen atom can be estimated for the unperturbed (due to intermolecular interactions) halogen atom. For this purpose, a method was provided to make possible a numerical quantification of the anisotropy of the halogen atom on the basis of electron density measurements performed within the framework of Atoms in Molecules Quantum Theory. The anisotropy of Cl and Br atoms in H 3 C-X and F 3 C-X (X=Cl, Br) was estimated for MP2 and DFT-B3LYP methods and several different basis sets. The influence of the method and the basis set on the degree of anisotropic distribution of electron density around halogen nuclei was discussed.Keywords Halogen bond Á The shape of the atom Á QTAIM Á DFT Á MP2 Á Basis set

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

“…Except for Br in BrCN, the equatorial portions on all the other halogens in the remaining seven molecules have negative electrostatic potential. These results signify that the electron density profile on the surface of the covalently bonded halogens is anisotropic in these molecules, in consistent with the profile that can be expected of the halogen in analogous molecules …”

“…These results signify that the electron density profile on the surface of the covalently bonded halogens is anisotropic in these molecules, in consistent with the profile that can be expected of the halogen in analogous molecules. [35] Table 1 lists the 0.001 a.u. isodensity mapped V s,max on the outer surfaces of the halogen derivatives along the RAX (X 5 F, Cl, Br) bonds in all the 18 monomers.…”

Theoretical study of the interaction of fluorinated dimethyl ethers and the ClF and HF molecules. Comparison between halogen and hydrogen bonds

“…The dispersion correction is estimated using the original “D2” method where dispersion energy is calculated from a pair wise r −6 potential between all the atoms. The reliability of the wB97XD functional for studying halogen bonding has been established by Kozuch and Martin and also in many recent works on halogen and hydrogen bonding . The geometries were also optimized by using the ab initio MP2/aug‐cc‐pVDZ method.…”

Interplay of thermochemistry and structural chemistry, the journal (volume 24, 2013, issues 3–4) and the discipline

“…The anisotropy of the halogen atom was studied in XÁÁÁN, O, XÁÁÁH(N, O) and XÁÁÁC type contacts by Bankiewicz and Palusiak [150]. The data on the distances in contacts and the information on the spatial arrangement of the interacting fragments were collected from the Crystal Structure Database.…”