Photo- and Thermo-Driven Azoarene-Based Circularly Polarized Luminescence Molecular Switch in Liquid Crystal Host.

The development of chiral optical active materials with switchable circularly polarized luminescence (CPL) signals remains a challenge. Here an azoarene-based circularly polarized luminescence molecular switch, (S, R, S)-switch 1 and its contrast (R, R, R)-switch 2, are designed and prepared with (R)-binaphthyl azo group as a chiral photosensitive moiety and two (S) or (R)-binaphthyl fluorescent molecules with opposite or same handedness as chiral fluorescent moieties. Both two switches exhibit reversible trans/cis isomerization irradiated by 365 nm UV light and 520 nm green light in solvent and liquid crystal (LC) media. In contrast with the control (R, R, R)-switch 2, when switch 1 is doped into nematic LCs, the polarization inversion and switching-off of the CPL signals are achieved in the resultant helical superstructure upon the irradiations of 365 nm UV and 520 nm green light, respectively. Meanwhile, the fluorescence intensity of the system is basically unchanged during this switching process. In particular, these variations of the CPL signals could be recovered after heating, realizing the true sense of CPL reversible switching. Taking advantage of the unique CPL switching, the proof-of-concept for "a dual-optical information encryption system" based on the above CPL active material is demonstrated.