Design and Luminescence Property of Liquid Crystalline Materials Based on Excited-State Intramolecular Proton Transfer Molecules

Abstract

Rod-shaped molecules based on 2-(2-hydroxyphenyl)benzothiazole (HBT) were synthesized and their liquid crystalline (LC) behavior as well as luminescent property were investigated. Due to the established four-level photo cycle of HBT accompanied with the excited-state intramolecular proton transfer, the synthesized molecules, C6Ph-HBT and C4-C≡C-HBT, show a large Stokes shift, avoiding the self-absorption and resulting in the transparency in the visible range. These compounds are extremely miscible to a conventional room-temperature nematic LC, 4-pentyl-4’-cyano biphenyl (5CB), up to 6 and 14 wt%, respectively, and the resultant mixtures exhibit a large photoluminescent quantum yield of 0.26 and 0.32, respectively, all of which is achieved by the introduction of 4-hexylphenyl/hexynyl groups that suppress the nonradiative decay pathways in the dispersed state.