Photoluminescence properties of ESIPT emitters in liquid crystals: Molecular design strategy for enhancing fluorescence quantum yields

Abstract

One of the typical luminophores that exhibit fluorescence via excited-state intramolecular proton transfer (ESIPT) mechanism is 2-(2-hydroxyphenyl)benzothiazole (HBT) that shows efficient fluorescence in the solid state. However, HBT has a drawback of low fluorescence quantum yield (ΦFL) in solutions and LCs (e.g. 0.01 in CH2Cl2 and 0.07 in 5CB). Here we report that the introduction of a cyano group at 4-position of the hydroxyphenyl group serves as an effective strategy for the remarkable increase of ΦFL in solution and LCs (e.g. 0.49 in CH2Cl2 and 0.57 in 5CB).