Photophysics of barrelene: The Jahn-Teller and pseudo-Jahn-Teller effects

• The static and dynamic aspects of (E ⊗ e) – Jahn-Teller (JT) and (E + A) ⊗ e   Pseudo Jahn-Teller (PJT) interactions in the X˜ -A˜ -B˜ -C˜ electronic states of the barrelene radical cation (BL+) are investigated with the aid of an ab initio based quantum dynamical approach.
• Nonadiabatic nuclear motion on the coupled manifold of X˜ -A˜ -B˜ -C˜ electronic states are simulated both by time-independent and time-dependent quantal methods.
• The JT stabilization energy is ∼ 0.25 eV in the electronic state A˜ of BL+ and the PJT interactions between B˜ -C˜ coupled electronic states of BL+ is stronger.
• The internal conversion rate for the A˜, B˜ and C˜ electronic states are ∼ 50 fs, ∼ 20 fs and 7 fs, respectively.
• The theoretical results are found to be in very good accord with the experimental data.

The static and dynamic aspects of Jahn-Teller(JT) and pseudo-Jahn-Teller(PJT) interactions between ground (X˜2A2′) and first three excited electronic states (A˜2E′, B˜2E″ and C˜2A′1 ) of bicyclo- [2,2,2]-octa-2,5,7-triene (barrelene) radical cation (Bl+) are theoretically investigated here. This belongs to the (E + E) ⊗ e and (E + A) ⊗ e   JT-PJT class of compounds as described by the symmetry of the electronic states and the molecular point group. The complex vibronic dynamics on the coupled electronic states of the cation is simulated by both time-independent and time-dependent wave packet propagation method using multi configuration time-dependent Hartree scheme. The JT effects in the A˜ and B˜ electronic states and the PJT coupling between the B˜ and C˜ electronic states of Bl+ are found very strong. The final theoretical results are compared with the experimental results.