Photorelease Reaction Mechanism Study of a Diarylethene Caged Dual Functions Compound

Femtosecond transient absorption, nanosecond transient absorption, and nanosecond resonance Raman spectroscopy techniques coupled with density functional theory calculations were performed to unravel the photocyclization and photorelease mechanisms of a diarylethene based compound (1o) containing two caged groups (OMe and OAc). Since the ground state parallel (P) conformer of 1o with a large dipole moment is stable in DMSO, the fs-TA transformations observed for 1o in DMSO mainly have contributions from the P conformer, which undergoes an intersystem crossing to generate a corresponding triplet state species. In a less polar solvent like 1,4-dioxane, in addition to the P path behavior of 1o, an antiparallel (AP) conformer can also take place to give a photocyclization reaction from the Franck-Condon state and finally give a deprotection via this pathway. This work provides a deeper understanding for these reactions, which not only facilitate the applications of diarylethene compounds but also help for the future design of functionalized diarylethene derivatives for particular applications.