Investigation of the photophysical behavior for the excited state intramolecular proton transfer compound based on 2-(2'-hydroxyphenyl)benzothiazole

By spectrum analysis and theoretical calculation, the photophysics of the excited state for the excited state intramolecular proton transfer (ESIPT) compound, DHBIA {N, N'-di[3-hydroxy-4- (2'-benzothiazole)phenyl]5-tert-butyl-isophthalic amide}, was thoroughly investigated. It was revealed that the vertical normal enol excited state favored an extremely fast twisted intramolecular charge transfer (TICT) deactivation via rotation of C-N bond, resulting in a greatly twisted configuration of the enol excited state. The nonradiative decay of this TICT geometry relaxation prevailed against the ESIPT deactivation to the keto excited state, leading to the weak luminescence of the dilute solution, which was essential to the enhanced emission of its aggregates.