TDDFT investigation on electronically excited-state hydrogen-bonding properties and ESIPT mechanism for the 2-(1H-imidazol-2-yl)-phenol compound

Abstract

In this work, DFT and TDDFT approaches have been executed to make a detailed exploration about the excited state luminescent properties as well as excited state intramolecular proton transfer (ESIPT) mechanism for the novel 2-(1H-imidazol-2-yl)-phenol (PI) compound. Optimized geometrical parameters of primary chemical bonds and infrared (IR) spectra prove that the O37-H38···N26 hydrogen bond of PI should be strengthened in the S1 state. Insights into frontier molecular orbitals (MOs), we infer charge redistribution and charge transfer (ICT) phenomena motivate ESIPT trend. Via probing into potential energy curves (PECs) in related electronic states, we come up with the ultrafast ESIPT behavior due to low potential barrier. Furthermore, we search the reaction transition state (TS) and simulate intrinsic reaction coordinate (IRC) path; the ultrafast ESIPT behavior and mechanism of PI compound can be re-confirmed. We sincerely wish that this work could play roles in further developing novel applications based on PI compound and in promoting new ratiometric fluorescence probes in the future.