Structure of the hexafluorobenzene anion

Abstract

The D 6 h , D 2 h (two), C 2 v , and D 2 structures of the hexafluorobenzene radical anion (C 6F 6 −) were studied by using density functional B3LYP method in conjunction with 6-31+G(d) and 6-311+G(d) basis sets. The B3LYP geometry optimization and frequency analysis calculations indicate that the C 2v( 2 A 1) structure has the lowest energy and represents an energy minimum. Adiabatic electron affinity value of the C 6F 6 molecule with respect to the anionic ground state (C 2v( 2 A 1)) is predicted to be 0.72–0.76 eV, in good agreement with the experimental data. Isotropic hyperfine coupling constants on the F- and 13C-centers ( a(F) and a(C)) in the C 2v( 2 A 1) structure were calculated by using ab initio MP2 as well as B3LYP methods, and averages of the calculated a(F) and a(C) values are in good agreement with the experimental coupling values. All these results indicate that the C 6F 6 − anion has a C 2 v structure and is in the 2A 1 ground state. The B3LYP calculations confirm that the D 2( 2 A) structure be the transition state for the pseudo-rotation process of the C 2v( 2 A 1) structure.