Nonadiabatic Dynamics Simulations on Early-Time Photochemistry of Spirobenzopyran

Abstract

Photoinduced ring-opening, decay, and isomerization of spirobenzopyran have been explored by the OM2/MRCI nonadiabatic dynamics simulations based on Tully’s fewest-switches surface hopping scheme. The efficient S1 to S0 internal conversion as observed in experiments is attributed to the existence of two efficient excited-state decay pathways. The first one is related to the C–N dissociation, and the second one is done to the C–O dissociation. The C–O dissociation pathway is dominant, and more than 90% trajectories decay to the S0 state via the C–O bond-fission related S1/S0 conical intersections. Near these regions in the S0 state, trajectories can either return to spirobenzopyran or proceed to various intermediates including merocyanine via a series of bond rotations. Our nonadiabatic dynamics simulations also demonstrate that the hydrogen-out-of-plane (HOOP) motion is important for efficient and ultrafast excited-state deactivation. On the other hand, we have also found that the replacement of methyl groups by hydrogen atoms in spirobenzopyran can artificially introduce different intramolecular hydrogen transfers leading to hydrogen-transferred intermediates. This finding is important for the community and demonstrates that such a kind of structural truncation, sometimes, could be problematic, leading to incorrect photodynamics. Our present work provides valuable insights into the photodynamics of spirobenzopyran, which could be helpful for the design of spiropyran-based photochromic materials.

Nonadiabatic Exciton and Charge Separation Dynamics at Interfaces of Zinc Phthalocyanine and Fullerene: Orientation Does Matter

“…This method has been implemented and widely used to simulation photoinduced ultrafast processes of organic and organometallic systems in gas and solution phases and biological surroundings. − …”

Design and Nonadiabatic Photoisomerization Dynamics Study of a Three-Stroke Light-Driven Molecular Rotary Motor

“…All semi-empirical calculations were performed with the OM2/MRCI method as implemented in the development version of the MNDO program [ 30 ]. This method can balance the computational cost and accuracy well, as shown by many benchmark calculations [ 31 , 32 , 33 ], and has been used successfully in many calculations of photoinduced processes [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. The required energies, gradients, and nonadiabatic coupling elements were calculated analytically in the geometry optimizations and dynamics simulations.…”

Photoisomerization dynamics of spiropyran: A surface-hopping investigation

“…1 and in the following, which is also the system considered in the present work. Very recently, Zhang et al performed 19 a theoretical investigation of the photodynamics of SP and BIPS, using a methodological approach very similar to the one considered here. Taking into account only the S 1 excited state, they found a photoisomerization quantum yield of about 0.8 and a relaxation time to S 0 well below 0.5 ps.…”