Nonadiabatic Molecular Dynamics Study of the Relaxation Pathways of Photoexcited Cyclooctatetraene

In the current study, we present nonadiabatic (NAMD) and adiabatic molecular dynamics simulations of the transition-state dynamics of photoexcited cyclooctatetraene (COT). The equilibrium-state structure and absorption spectra are analyzed using the semiempirical Austin Model 1 potential. The NAMD simulations are obtained by a surface-hopping algorithm. We analyzed in detail an active excited to ground state relaxation pathway accompanied by an S-2/S-3(D-2d) -> S-1(D-8h) -> S-0(D-4h) -> S-0(D-2d) double-bond shifting mechanism. The simulated excitation lifetime is in good agreement with experiment. The first excited singlet state S-1 plays a crucial role in the photochemistry. The obtained critical molecular conformations, energy barrier, and transition-state lifetime results will provide a basis for further investigations of the bond-order inversion and photoswitching process of COT.

Automated summary

In this study, nonadiabatic and adiabatic molecular dynamics simulations were used to investigate the transition-state dynamics of photoexcited cyclooctatetraene (COT). The simulations revealed an active excited to ground state relaxation pathway and a double-bond shifting mechanism, with results in good agreement with experimental data. These findings provide valuable insights into the photochemistry of COT and lay a foundation for further research on bond-order inversion and photoswitching processes.