Tunable Anti‐Stokes‐Shift Behaviors Based on Intramolecular Charge Transfer Characteristics of Diarylethene Derivatives

Abstract Understanding the rules for designing anti‐Stokes emission induced by hot‐band absorption is crucial for developing novel materials for optical devices and biology. However, there are very few published reports on hot‐band‐absorption‐based single‐photon upconversion (HBA‐UC) materials, mainly because the rules for designing these molecules are poorly understood. Herein, HBA‐UC is investigated in a series of diarylethene derivatives (DAEs), namely benzothiophene S, S‐dioxide derivatives, which possess photochromic and photofluorochromic properties. All these DAEs show photoswitchable Stokes emission and HBA‐UC emission. Regulating the substituent groups enables flexibly adjustment of the HBA‐UC properties. Density functional theory (DFT) calculations reveal that the intramolecular charge transfer (ICT) between benzothiophene 1,1‐dioxide core and substituent groups is responsible for the emission properties of HBA‐UC. Furthermore, it is confirmed that the strong intensity of the ICT in DAEs can improve the scale of the anti‐Stokes shift. These findings provide a new direction for exploiting ICT feature in the design of HBA‐UC materials.