Novel chiral 1,4-bis(p-cyanostyryl)benzene liquid crystals with high circularly polarized luminescence tuned by length of alkyl chains

Although some AIE-based CPL materials had been presented, the design and synthesis novel AIE-based CPL materials and studies on the relationship of structure-property were still a challenging work. Herein, series of novel 1,4-bis(p-cyanostyryl)benzene derivatives 2a, 2b and 2c bearing chiral alkyl chains were prepared, and the influence of length of alkyl chains on CPL properties were investigated for the first time. Samples 2a, 2b and 2c were synthesized by simple procedure with 83-88 % yields. Samples 2b and 2c with longer chains displayed the typical liquid crystalline properties. All of them showed strong fluorescence in both solution and aggregated states. Their chiroptical properties of CD and CPL signals were influenced strongly by the molecular stacking in various states. The self-assembly in mesophase resulted in the best chiroptical properties. The longer alkyl chains contributed to stronger CD and CPL signals. The highest glum value attained 1.6 x 10-2 for sample 2c based on the effective chirality transfer and amplification of liquid-crystalline mesophase.