The regulation of π-linker aromaticity of thiophene derivatives on cyclization and ESPT reaction

Abstract

Recently, researchers studied how the aromaticity of π-linker affects cyclization reactions and found that varying aromaticity can regulate these reactions. Inspired by this, the different aromatic π-linker with proton donor-acceptor blocks will be investigated to explore the influence of aromaticity on cyclization and proton transfer reactions. In this work, the quantum chemical calculation combined with density functional theory (DFT) and the multi-configurational self-consistent field (MCSCF) methods are employed to unveil the photophysical and photochemical processes. The established potential energy curves (PECs) and the calculated minimum energy pathways (MEPs) indicate that the excited state proton transfer (ESPT) and photocyclization processes vary with different π-linker. The complete-active-space self-consistent-field (CASSCF) calculations reveal that a nonradiative channel will be opened via the conical intersection (CI) between the ground and the first excited states during photocyclization. The time evolved excited state nonadiabatic dynamics are simulated to demonstrate the ultrafast photocyclization reactions impede the ESPT. Finally, the aromaticity of various π-linker is evaluated using nucleus-independent chemical shifts (NICS) aromaticity indices. The study concludes that excited-state antiaromaticity relief facilitates the cyclization reaction and ESPT process.