Circularly Polarized Room Temperature Phosphorescence of Chiral Bromoxanthone Using a Chiral Self-Assembled Liquid Crystal Polymer Frameworks

Chiral self-assembly has often been found to be an efficient strategy for the development of high-performance circularly polarized luminescent (CPL) materials, through the regulation of the ordered helical superstructure blocks in liquid crystal media. Here, the design and synthesis of two pairs of axially chiral emitters (BBXT-3-Br and BOHXT-3-Br) are reported based on bromoxanthone. And the chiral self-assembled liquid crystal polymer (LCP) framework (PRM257) is demonstrated by mixing of the emitters with liquid crystal monomer (RM257) through thermal annealing and photoinitiated polymerization. Both BBXT-3-Br@PRM257 and BOHXT-3-Br@PRM257 exhibited excellent room temperature phosphorescence (RTP) properties. In addition, BBXT-3-Br@PRM257 enantiomers showed afterglow with an average lifetime (tau) of 162.41 ms and emitted blue CPL (lambda(em) = 450 nm, Phi(FL) = 1.3%, |g(FL)| = 0.071), although weak circularly polarized RTP (CP-RTP) is observed. Interestingly, BOHXT-3-Br@PRM257 with a less conjugated system emits red RTP (tau = 98.83 ms) and also intense CP-RTP (lambda(em) = 612 nm, Phi(Phos) = 0.45%, |g(RTP)| = 0.057).