(Z)-3-(Quinolin-2-ylmethylene)-3,4-dihydroquinoxalin-2(1H)-one derivatives: AIE-active compounds with pronounced effects of ESIPT and TICT

Abstract

A new family of (Z)-3-(quinolin-2-ylmethylene)-3,4-dihydroquinoxalin-2(1H)-one derivatives, which exhibit aggregation-induced emission (AIE) activity, is synthesized and characterized. The qualitative structure property analysis reveals that the emission behaviors of these compounds are closely related to the locations of substituents on the molecules. The density functional theory (DFT) calculations elucidate that excited state intramolecular proton transfer (ESIPT) can smoothly occur in these compounds and a following twisted intramolecular charge transfer (TICT) in the lowest excited singlet state should account for their fluorescence quenching in solution. The restriction of such a TICT process in the aggregated state is assumed as the mechanism for their AIE behaviors.