title: Photodynamics of oxybenzone sunscreen: Nonadiabatic dynamics simulations.
abstract: Herein we have used combined static electronic structure calculations and "on-the-fly" global-switching trajectory surface-hopping dynamics simulations to explore the photochemical mechanism of oxybenzone sunscreen. We have first employed the multi-configurational CASSCF method to optimize minima, conical intersections, and minimum-energy reaction paths related to excited-state intramolecular proton transfer (ESIPT) and excited-state decays in the (1)ππ(∗), (1)nπ(∗), and S0 states (energies are refined at the higher MS-CASPT2 level). According to the mapped potential energy profiles, we have identified two ultrafast excited-state deactivation pathways for the initially populated (1)ππ(∗) system. The first is the diabatic ESIPT process along the (1)ππ(∗) potential energy profile. The generated (1)ππ(∗) keto species then decays to the S0 state via the keto (1)ππ(∗)/gs conical intersection. The second is internal conversion to the dark (1)nπ(∗) state near the (1)ππ(∗) /(1)nπ(∗) crossing point in the course of the diabatic (1)ππ(∗) ESIPT process. Our following dynamics simulations have shown that the ESIPT and (1)ππ(∗) → S0 internal conversion times are 104 and 286 fs, respectively. Finally, our present work demonstrates that in addition to the ESIPT process and the (1)ππ(∗) → S0 internal conversion in the keto region, the (1)ππ(∗) → (1)nπ(∗) internal conversion in the enol region plays as well an important role for the excited-state relaxation dynamics of oxybenzone.
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Chun-Xiang
authors.initials: CX
authors.lastname: Li
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Guo
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Xie
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Ganglong
authors.initials: G
authors.lastname: Cui
mesh_terms: D001577:Benzophenones / Q000737:chemistry*; D008027:Light; D011789:Quantum Theory; D013473:Sunscreening Agents / Q000737:chemistry*
chemical_list: D001577:Benzophenones; D013473:Sunscreening Agents; C005290:oxybenzone