Triphenylene-Fluorescein-Triphenylene Trimers: Novel Columnar Liquid Crystals With Solid Fluorescence

This paper reported the first triphenylene-fluorescein-triphenylene trimers (3a and 3b), which exhibited stable hexagonal columnar mesophase and good fluorescence in comparison with the similar triphenylene-fluorescein dimers. The trimers 3a and 3b bridged by -C3H6- and -C6H12- group were conveniently prepared in yields of 67% and 73%. They exhibited the stable hexagonal columnar mesophase, high fluorescence quantum yields, and the large Stokes shifts due to the influence of two triphenylene units. The highest fluorescence quantum yield attained 0.91 for 3b and the largest Stokes shift reached 105 nm for 3a. This work revealed that trimers were a good strategy to construct novel columnar liquid crystals with stable columnar mesophase and high fluorescence.