Detailed dynamics of a complex photochemical reaction: Cis–trans photoisomerization of stilbene

Abstract

Detailed simulations are reported for the dynamics of electrons and nuclei during the cis to trans photoisomerization of stilbene. Our method, which employs a semiclassical description of both the nuclear motion and the radiation field, is described in the text. After excitation of electrons from the HOMO to the LUMO by a femtosecond-scale laser pulse, two principal avoided crossings are observed between the HOMO and LUMO levels, each of which leads to substantial depopulation of the LUMO. Based on our results and those of other groups, we propose that the first such HOMO-LUMO coupling can lead to the formation of 4a,4b-dihydrophenanthrene (DHP). The second coupling, on the other hand, leads to the formation of trans-stilbene. It is found that pyramidalization of the two carbon atoms of the vinyl group is involved significantly in both couplings, and that rotation of the two phenyl rings, together with their interaction, plays an important role in the first coupling. The occurrence along the same trajectory of two couplings, one leading to DHP and the other leading to isomerization, is a significant observation, and one which indicates that further theoretical and experimental investigations would be of considerable interest.

Nonadiabatic simulation study of photoisomerization of azobenzene: Detailed mechanism and load-resisting capacity

“…The method used here is the so-called semiclassical electron-radiation-ion dynamics to emphasize both its strengths and its limitations [32][33][34][35] . The valence electrons are treated quantum-mechanically, while both the radiation field and the motion of the ion cores are treated classically.…”

“…37 The electronic states were calculated with a density-functional-based method 36,38 , which has similar strengths and limitations as TDDFT. Reliability of our simulation method for light-driven molecular dynamics has been calibrated and verified systematically for a series of light-responding molecules [33][34][35]39,40 .…”

Dynamics of the photocyclization ofcis-stilbene to dihydrophenanthrene

“…Very recently, we have performed a series of simulation studies on the molecular response to ultrashort laser irradiation [9][10][11][12]. These include the photo-isomerization of cis-and trans-butadiene [9,10], and cis-stilbene [11,12] using a semiclassical approach.…”

“…These include the photo-isomerization of cis-and trans-butadiene [9,10], and cis-stilbene [11,12] using a semiclassical approach. The simulation results provide insights into the dynamics of these complicated photoreactions.…”

Photoisomerization of Stilbene: A Spin-Flip Density Functional Theory Approach

“…Another possibility is that cis-stilbene approaches both the (S 0 /S 1 ) coop and (S 0 /S 1 ) pyr CI points. Dou and Allen 61 have performed direct dynamics simulations for cis-stilbene on the S 1 state by using Hamiltonian matrix elements fitted to tightbinding local-density approximation DFT calculations. The authors found two principal avoided crossings along the single trajectory and proposed that the first crossing point leads to DHP formation and the second to the trans-stilbene product.…”