Tunable AI-CPL behavior by regulation of microstructure of AIE-active isomers through chiral emissive liquid crystals

Abstract

Circularly polarized luminescence (CPL) emission materials with high luminescence dissymmetry factor (glum) and high quantum yield (QY) are currently in urgent demand for real applications. Three D-A type enantiomers (R-/S-1, 2 and 3) were designed and synthesized that combine a phenanthro [9,10-d]imidazole (PIP) unit to a naphthalimide (NI) at the p-, m-, o-positions. These AIE-active enantiomers were chosen as CPL emitters doped into nematic liquid crystals (E7, N-LCs) to form three chiral nematic liquid crystals (N*-LCs-1, 2 and 3). Interestingly, N*-LCs-1 shows higher glum (+0.91/-0.98) and QY (18.5%) than N*-LCs-2 (glum = +0.86/-0.89, QY = 1.3%) and N*-LCs-3 (glum = +0.010/-0.013, QY = 4.7%) due to effective chirality transfer and intramolecular electronic coupling from microstructure change of AIE-active isomers. This paper revealed that AI-CD and AI-CPL enhancement behavior of N*-LCs could be regulated not only by the chirality transfer via supramolecular self-assembly but also by the electronic coupling strength through microstructure change of AIE-active isomers of donor units in the chiral emitters. This work can provide a new strategy for the development of CPL LCs materials.