Computational Investigation of the Pseudo Jahn–Teller Effect on the Structure and Chemical Properties of Perhaloethene Anions

Abstract

The instability of planar structures in [C₂X₄]⁻ (X = H, F, Cl, Br) molecules due to the pseudo Jahn-Teller effect (PJTE) is investigated as an original PJTE study. Optimization and the following frequency calculations in these molecules illustrate that all of these compounds are unstable in high symmetry planar (with D_2h symmetry) geometry and their structures are distorted to a lower C_2h symmetry stable geometry. Moreover, the vibronic coupling interaction between ²B_2g ground and ²A_g excited states via the (²B_2g + ²A_g) ⊗B_2g PJTE problem is the reason for the symmetry breaking phenomenon and non-planarity in those series. Natural bond analysis (NBO) is used for illustrating the strongest interaction and natural atomic charges of these structures.