title: New insights into mechanistic photoisomerization of ethylene-bridged azobenzene from ab initio multiple spawning simulation.
abstract: Ethylene-bridged azobenzene (br-AB) has aroused broad interests due to its unique photoswitching properties. Numerous dynamical simulations have been performed for the br-AB photoisomerization, which focused mainly on the conformational effect and the funnel role of minimum-energy conical intersection (MECI) on the mechanism. In the present work, we use the "full quantum" ab initio multiple spawning method to simulate the br-AB photoisomerization, which provides new insights into the mechanism. Upon irradiation of br-AB to the first excited singlet state (S1), most of the excess energies are trapped in the azo-moiety. Since the intramolecular vibrational energy redistribution is slower than the S1relaxation processes, the nonadiabatic transition from S1to the ground state (S0) occurs in the vicinity of high-energy crossing seam and even the largest probabilities of the S1→ S0transition are not distributed in the MECI regions. Once decaying to the S0state through the high-energy region, the subsequent isomerization and re-formation of the initial isomer are ultrafast processes in the S0state. It is the nonergodic behavior of the S1and S0dynamics that is mainly responsible for the unique photoswitching properties of the ethylene-bridged azobenzene, which will be discussed in detail.
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Liu
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Yating
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Qiu
authors.initials: Q
authors.lastname: Fang