A theoretical study on excited state proton transfer in 2‐(2′‐dihydroxyphenyl) benzoxazole

Abstract

AbstractThis research investigates the dynamic excited state process for a novel system 2‐(2′‐dihydroxyphenyl) benzoxazole (DHBO) for excited state proton transfer (ESPT) process based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Because 2 intramolecular hydrogen bonds (O1―H2···N3 and O4―H5···O6) in DHBO molecules may trigger proton transfer process in the S1 state, we focus on these 2 hydrogen bonds. Our results show that only the O1―H2···N3 bond has obvious changes in both bond length and bond angle upon photoexcitation. Charge redistribution also confirms that hydrogen bond wire (O1―H2···N3) is the best way to achieve the ESPT process in the S1 state. Considering the ESPT mechanism, our theoretical potential energy curves of DHBO indicate that only the excited state single‐proton transfer process occurs via O1―H2···N3 rather than O4―H5···O6. We believe that our work not only clarifies the excited state dynamical behavior of DHBO but also promotes the investigations about ESPT reactions in intramolecular or intermolecular hydrogen bonded chemical systems.