Tailorable Multi-Photoresponsive Behavior Triggered by Different Sulfur Oxidation States

Photoresponsive materials are considered as promising systems for intelligent technology applications owing to the contactless spatial and temporal control.Herein, controllable multi-photoresponsive behaviors are realized in benzo[b]thiophene derivatives (o-DMP-S, o-DMP-SO, and o-DMP-SO₂) by modulating the sulfur oxidation state.Among them, o-DMP-S is photo-unreactive but possesses denser molecular packing upon ultraviolet (UV) light irradiation, exhibiting photoenhanced room-temperature phosphorescence properties.Through stoichiometric oxidation of the sulfur atom in o-DMP-S, the resulting sulfoxide compound o-DMP-SO undergoes a radical photolysis reaction involving photodeoxygenation and photochemical rearrangement, thereby leading to the photomechanical effect.The sulfone compound o-DMP-SO₂ displays prominent reversible photochromism, resulting from the radical photocyclization under 365 nm UV light irradiation.Based on comprehensive experimental and computational investigations, the diverse photoresponsive behaviors of these benzo[b]thiophene derivatives are demonstrated to depend on the intersystem crossing efficiency and radical-mediated photochemical reaction activity in excited states due to the different sulfur oxidation states.This work provides an insightful understanding of the relationship between molecular structure and photoresponsive behavior and opens up the opportunity for the development of photoresponsive materials with potential applications.