Substitution effect on the intermolecular halogen and hydrogen bonds of the σ‐bonded fluorinated pyridine···XY/HX complexes (XY = F₂, Cl₂, ClF; HX = HF, HCl)

Abstract

Optimal structures, electronic and thermodynamic properties of the title complexes are presented. The stability of the hydrogen bonded systems is enhanced by the increasing dipole moments whereas in the halogen bonded systems it is also affected by the atom size in the diatomics. The consecutive addition of fluorine atoms to the pyridine moiety results in the decrease of the interaction energy for both types of the investigated bonds. The substitution on the meta sites in pyridine leads to more stable complexes than the substitution in the ortho position.The role of substitution on electric polarization and electrostatic forces is estimated by the symmetry-adapted perturbation theory energy decomposition. The predicted Gibbs free energies of the complexes of mono fluorinated pyridines with HCl, HF, and ClF are from 212 to 222 kJ mol 21 at 200 K. The possible experimental identification of the complexes with respect to the vibrational modes is discussed.

σ-Hole Bond vs π-Hole Bond: A Comparison Based on Halogen Bond

“…It is therefore the least likely to function as a halogen-bond donor. However, some theoretical calculations and experimental results indicate that F atoms can indeed work as halogen-bond donors and interact with electron-rich elements to form halogen-bond complexes under specific circumstances including F 2 or CN–F, ,− although their strengths are much weaker than other halogens.…”

Molecular Design of Ionization-Induced Proton Switching Element Based on Fluorinated DNA Base Pair

“…Recently, it has been shown that the halogen substitution changes drastically the structure and electronic states of molecules. − Development of high performance switching device may be possible using the halogen substitution in the DNA base pair.…”

“…The aminopyridine and pyrimidine dimers are known as mimic models of DNA base pair with two hydrogen bonds between AP molecules. − Ionization of (AP) 2 causes a proton transfer along the hydrogen bonds, and it forms a defect of hydrogen bond in DNA. Time scale of PT process was estimated to be 100–200 fs, which is a very fast process as a chemical reaction .…”