Turn-on circularly polarized luminescence for dynamical-racemic and large-hollow AIE macrocycle based on selective recognition for ursolic acid

The macrocycles with the features of large cavity, optical property and CPL response to guest simultaneously are rarely reported but very attractive based on their potential application. Herein, a macrocycle (BiCDB-MC) with dynamically racemic feature, inwardly directed functional groups, a large hollow with size of 1.3 nm and fluorescent property was designed and synthesized. BiCDB-MC was found to have two equally chiral conformations and was dynamically racemic in solution based on their rapidly interconvertion via macrocycle flipping. It was interesting that BiCDB-MC exhibited a selective turn-on CPL response with glum = 0.00248 toward ursolic acid since one of the stable chiral conformations could form a more stable inclusion complex. This kind of turn-on CPL emission for dynamical-racemic macrocycle with CPL recognition for complicated natural chiral compound was described for the first time.