Ultrafast Photoisomerization of N-(2-Methoxybenzylidene)aniline: Nonadiabatic Surface-Hopping Study

We investigated the ultrafast photoisomerization of N-(2-methoxybenzylidene)aniline in the gas phase excited into the second singlet (S-2) state by nonadiabatic surface-hopping dynamics calculations. Two trans isomers (1E and 1E') were taken into consideration in our dynamics simulation. Three conical intersections (CIs) were characterized in the optimization. The CI between S-2 and the first singlet (S-1) states presents a nearly planar structure, while the other two CIs (CItwist-I and CItwist-II) between S-1 and the ground (S-0) states show nearly perpendicular geometries. After two trans isomers excited to the S-2 state, the torsion of the C-N bond connected the phenyl group and the stretch of the central bridging bond make the molecule reach CIplanar, and the S-2/S-1 hopping occurs. During the S-1-state dynamics, the molecule moves to a S-1/S-0 CI (CItwist-I or CItwist-II) by the rotation of the central bridging bond. The cis isomer is obtained through a barrierless pathway in the S-0 state with the torsion of the three bridging bonds. There is a main channel and an alternative one for the photoisomerization process of both trans isomers. CItwist-I and CItwist-II act as S-1/S-0 decay funnels in the main isomerization channels of 1E and 1E' isomers, respectively, and the photochemical processes of 1E and 1E' lead to different cis isomers.

Automated summary

The ultrafast photoisomerization of N-(2-methoxybenzylidene)aniline in the gas phase excited into the second singlet state was investigated via nonadiabatic surface-hopping dynamics calculations. Two trans isomers were considered with three conical intersections playing key roles in the isomerization process, leading to the formation of different cis isomers.