Nonadiabatic Molecular Dynamics Study of the Relaxation Pathways of Photoexcited Cyclooctatetraene

Huajing Song; Yeonsig Nam; Daniel Keefer; Marco Garavelli; Shaul Mukamel; Sergei Tretiak

doi:10.1021/acs.jpclett.1c01397

Nonadiabatic Molecular Dynamics Study of the Relaxation Pathways of Photoexcited Cyclooctatetraene

J Phys Chem Lett. 2021 Jun 24;12(24):5716-5722. doi: 10.1021/acs.jpclett.1c01397. Epub 2021 Jun 15.

Authors

Huajing Song¹, Yeonsig Nam², Daniel Keefer², Marco Garavelli³, Shaul Mukamel^{2

4}, Sergei Tretiak^{1

5}

Affiliations

¹ Physics and Chemistry of Materials, Theoretical Division, Los Alamos National Laboratory, Los Alamos 87545, New Mexico, United States.
² Department of Chemistry, University of California, Irvine 92697, California, United States.
³ Department of Industrial Chemistry, "T. Montanari", Università degli Studi di Bologna, Viale del Risorgimento, 4, Bologna 40136, Italy.
⁴ Department of Physics and Astronomy, University of California, Irvine 92697, California, United States.
⁵ Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos 87545, New Mexico, United States.

PMID: 34128675
DOI: 10.1021/acs.jpclett.1c01397

Abstract

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 S₂/S₃(D_2d) → S₁(D_8h) → S₀(D_4h) → S₀(D_2d) double-bond shifting mechanism. The simulated excitation lifetime is in good agreement with experiment. The first excited singlet state S₁ 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.