Oxygen-Acceptor-Driven High Photochromic Contrast Solid-State Excited-State Intramolecular Proton Transfer Photoswitches

Developing high photochromic contrast photoswitches in the solid state remains a significant challenge in organic smart materials. We here provide an oxygen-acceptor strategy for constructing an excited-state intramolecular proton transfer (ESIPT)-inspired organic photoswitch, namely tpmSA. By introducing a bulky triphenylmethane into the salicylaldehyde skeleton, tpmSA can achieve photochromic behavior in the solid state. Upon exposure to ultraviolet (UV) light, tpmSA displays distinct color variation from white to yellow, yielding a high photochromic contrast (ΔE*_Lab>74). Kinetic studies suggest that tpmSA can undergo rapid photoisomerization and is capable of reversible switching for over 20 cycles, demonstrating superior fatigue resistance. Mechanistic studies reveal that the weakly alkaline oxygen-acceptor in tpmSA significantly enhances photochromic contrast by suppressing the ground-state intramolecular proton transfer (GSIPT) pathway. The photopatterning and high-level information encryption were successfully developed by tpmSA. This study proposes an oxygen−acceptor strategy for developing solid-state photoswitches with high photochromic contrast, demonstrating great potential for advanced information encryption materials.