Calculations on the Jahn–Teller configurations of the benzene cation

Abstract

The analysis of the zero-electron-kinetic-energy photoelectron spectra of benzene has led to a reinvestigation by ab initio methods of the electronic states of the C6H6+ cation resulting from Jahn–Teller distortions on ionization. The calculations involving a range of currently used methodologies all verify that the two cation configurations, B2g2 and B3g2 of D2h symmetry, resulting from removal of an electron from the e1g(π) degenerate MOs of C6H6, comprise a true minimum and a transition state, differing only slightly in energy. These are linked through the in-plane b1g vibration, confirming that b1g is actually a pseudorotational coordinate. Hence C6H6+ exhibits similar structural floppiness to the cations of methane and cyclopropane although with a much smaller barrier to pseudorotation than for these smaller species. These results support the general proposition that such Jahn–Teller distortions associated with molecular ionization (of stable closed-shell hydrocarbon molecules of high symmetry) generally involve a quadratic contribution which leads to a single global minimum cation structure, with all other derived stationary states being transition states each characterized by a single imaginary vibration frequency.

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

“…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]. This is due to the small value of Δ which is in the range of errors of the calculations.…”

“…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.…”

Infrared photodissociation spectroscopy of benzene–Ne,Ar complex cations

“…2 the results obtained earlier by Mu¨ller-Dethlefs and Peel were reproduced; 21 for a more detailed discussion on the methods used and the interpretation of the D 2h calculations the reader is referred to ref. 21.…”

Calculation of the Jahn-Teller effect in benzene cation: Application to spectral analysis

“…[13][14][15][16][17][18][19][20] This interest originates not only from its relationship to the parent neutral benzene molecule but also from the unique properties which the benzene cation possesses. Neutral benzene has the dominant electronic configuration of…”