Impact of Substitution Positions and Solvents on ESIPT Mechanisms and Photophysical Properties of TFAQ and Its Derivatives: A Theory Perspective

ABSTRACT The excited state intramolecular proton transfer (ESIPT) process and fluorescent properties of trifluoroanthraquinone (TFAQ) derivatives are investigated by introducing 1’‐methyl‐2’, 3’, 4’‐trihydropyridine or 3’‐hydroxylpyridine to the 2, 3‐positions or 7, 8‐positions with time‐dependent density functional theory (TD‐DFT) methods. Through the analysis of geometric parameters and infrared (IR) vibrational spectra, it is evident that the hydrogen bonds (HBs) are strengthened in the S1 state, providing the driving force for the ESIPT behavior. Next, frontier molecular orbitals (FMOs) and hole‐electron analyses reveal dynamically distinct intramolecular charge transfer characteristics (ICTC). Furthermore, scanning of the potential energy curves (PECs) reveals that TFAQ‐C more readily exists in a stable enol form in the S1 state. Finally, the photophysical properties demonstrate that TFAQ and TFAQ‐C have dual fluorescent emission, and TFAQ‐C‐enol can act as a promising ambipolar material. This work provides robust insights for the design and development of novel TFAQ‐derived WOLED materials.