Stereoselective Excited-State Isomerization and Decay Paths in cis-Cyclobiazobenzene

Abstract

Herein we have employed OM2/MRCI-based full-dimensional nonadiabatic dynamics simulations to explore the photoisomerization and subsequent excited-state decay of a macrocyclic cyclobiazobenzene (CBA) molecule. Two S1/S0 conical intersection structures are found to be responsible for the excited-state decay. Related to these two conical intersections, we found two stereoselective photoisomerization and excited-state decay pathways, which correspond to the clockwise and counterclockwise rotation motions with respect to the N=N bond of the azo group. In both pathways the excited-state isomerization is ultrafast and finishes within ca. 69 fs; but, the clockwise isomerization channel is much more favorable than the counterclockwise one with a ratio of 74% vs. 26%. Importantly, the present work demonstrates that stereoselective pathways exist not only in the photoisomerization of isolated azobenzene-like systems but also in macrocyclic systems with multiple azobenzenes (ABs). This finding could provide useful insights for understanding and controlling the photodynamics of macrocyclic nanostructures with AB units as the main building units.

Nonadiabatic Dynamics Simulations on Early-Time Photochemistry of Spirobenzopyran

“…This is ascribed to the fact that S1S0_SPc [S1S0_SPt] is structurally much closer to S0_SPc [S0_SPt]. This exclusive stereospecific excited-state relaxation is seen in previous studies. ,, The right panel of Figure depicts time distribution of all hopping events from S 1 to S 0 . Almost all hopping events take place within 150 fs with a maximum peak at about 60 fs, in good agreement with experimental studies. ,, Moreover, it can be found that SPc and SPt have similar distribution for the S 1 → S 0 hopping times (see red vs blue in the right panel of Figure ).…”

“…This exclusive stereospecific excited-state relaxation is seen in previous studies. 43,58,69 The right panel of Figure 5 depicts time distribution of all hopping events from S 1 to S 0 . Almost all hopping events take place within 150 fs with a maximum peak at about 60 fs, in good agreement with experimental studies.…”

“…Excited-state nonadiabatic dynamics are studied by performing 500 fs trajectory-based surface-hopping simulations at the OM2/MRCI level. These simulations are carried out under the NVE ensemble to keep total energy conserved as done in previous studies by our and other groups; − however, their initial geometries and velocities are obtained using the Wigner sampling technique as implemented in the Newton-X package . The Wigner sampling is carried out at 300 K because the finite temperature can give better phase-space sampling, which has also seen in recent work .…”

Significant Impact of Deprotonated Status on the Photoisomerization Dynamics of Bacteriophytochrome Chromophore

“…42,43 Many studied have verified that the nonadiabatic dynamics at the OM2/MRCI level is a powerful simulation tool in the description of excitedstate processes for media-sized and large polyatomic systems with the balance of computational accuracy and efficiency. [44][45][46][47][48][49] By following the excited-state molecular motions, we found that the protonation/deprotonation states of the pyrrole ring show the strong impact on the excited-state lifetime and reaction pathways. The underline reason is that the hydrogen bond network deeply modules the intramolecular motion, leading to different profiles of excited-state potential energy surfaces.…”

Unexplored Isomerization Pathways of Azobis(benzo-15-crown-5): Computational Studies on a Butterfly Crown Ether

“…The photochemical isomerization of azobenzene and its derivatives has been reported in numerous experimental − and computational − papers in the past and in recent times. Some of these papers have reported combined experimental and theoretical results, as well.…”