Axially chiral materials exhibiting blue-emissive ultralong organic phosphorescence and intense circularly polarized luminescence

In this work, one type of axially chiral materials with both blue-emissive ultralong organic phosphorescence (UOP) and intense circularly polarized luminescence (CPL) is reported. Such materials not only exhibit extremely small energy gap between the S1 and T1 states (?E-ST, 0.03 eV), greatly promoting the intersystem crossing process for more triplet excitons, but also show ultralong phosphorescent lifetime (5.5 s). As a result, a bright blue afterglow of up to 60 s is achieved in 2-methyltetrahydrofuran at 77 K. The exciton hourglass model is further proposed to describe the internal photophysical processes. Moreover, such UOP materials also exhibit intense CPL because of the rigid axially chiral skeleton. Impressively, the luminescence asymmetry factor (glum) value of up to 0.34 can be achieved by applying them as the chiral inducers for liquid crystal materials. This work can provide a guideline and perspective for further designing novel pure organic molecules with both UOP and intense CPL.

Automated summary

This work reports on axially chiral materials that exhibit both blue-emissive ultralong organic phosphorescence (UOP) and intense circularly polarized luminescence (CPL). The materials have a small energy gap between the S1 and T1 states, promoting the intersystem crossing process and leading to a long phosphorescent lifetime. In addition, the materials show intense CPL and can be used as chiral inducers for liquid crystal materials, achieving a high luminescence asymmetry factor.