Vibronic coupling in benzene cation and anion: Vibronic coupling and frontier electron density in Jahn-Teller molecules

Abstract

Vibronic coupling constants of Jahn-Teller molecules, benzene radical cation and anion, are computed as matrix elements of the electronic part of the vibronic coupling operator using the electronic wave functions calculated by generalized restricted Hartree-Fock and state-averaged complete active space self-consistent-field methods. The calculated vibronic coupling constants for benzene cation agree well with the experimental and theoretical values. Vibronic coupling density analysis, which illustrates the local properties of the coupling, is performed in order to explain the order of magnitude of the coupling constant from view of the electronic and vibrational structures. This analysis reveals that the couplings of the e2g2 and e2g3 modes in which the large displacements locate on C-C bonds are strong in the cation. On the other hand, they are greatly weakened in the anion because of the decrease of electron density in the region of the C-C bonds, which originates from the antibonding nature of the singly occupied molecular orbital of the anion. However, the difference of the electronic structure has a little influence on the vibronic coupling of the e2g4 mode. These results indicate that the vibronic coupling depends not only on the direction of the nuclear displacement but also on the frontier electron density.

Density Functional Theory Study of the Multimode Jahn-Teller Effect – Ground State Distortion of Benzene Cation

“…Thus, in D 2h symmetry there are . This is in agreement with previous studies [48,53,54]. These three vibrations are illustrated on the Fig.…”

“…experimental value of Lindner et al is 266 cm −1 [46]. Recent calculations based on complete active space or DFT, including this study, are much more consistent and in general agreement that E JT falls in range between 700 and 1,000 cm −1 [48,53,54]. Even more inconsistency is found for the value of Δ , and alternately both states are reported to be a global minimum [47,48].…”

“…Small energy difference between the 2 B 2g and 2 B 3g states suggests that the second order JT effects and anharmonicity are small and that JT effect in benzene cation is dynamic. Benzene cation has been thoroughly studied over the years [45][46][47][48][49][50][51][52][53][54][55]. The values of the JT parameters largely depend on the used method and model employed.…”

Charge and Magnetic Orderings in the Triangular-Lattice Antiferromagnet InFe2O4

“…Vibronic coupling density analysis is shown to be intuitive and useful for the explanation of the order of magnitude of the coupling constant of C 5 H 5 [3], C 6 H 6 + , and C 6 H 6 - [4]. Moreover, this analysis is applied to the explanation of the effect of deuterium substitution and halogen substitution on the vibronic coupling.…”

Hydrogenation of Fullerene C60: Material Design of Organic Semiconductors by Computation

“…The reorganization energy is a stabilization energy by geometrical relaxation originating from the change in electronic structure [64][65][66]. The strong forces on the nuclei generally result in large λ and geometrical relaxation.…”