Aggregation-Dependent Circularly Polarized Luminescence and Thermally Activated Delayed Fluorescence from Chiral Carbene-CuI-Amide Enantiomers

The field of luminescent carbene-metal-amide (CMA) complexes and chiroptical-active materials has been blossoming in recent years, although chiroptical-active CMA complexes have not been reported so far. For the first time, a pair of chiral Cu-I-based CMA enantiomers, (R,R)-PSIPr*-Cu-DMAC and (S,S)-PSIPr*-Cu-DMAC, have been developed by using chiral phenyl-substituted N-heterocyclic carbenes as acceptor ligands in the CMA motif. The Cu-I-based CMA enantiomers exhibited aggregation-induced circularly polarized luminescence with a large luminescence dissymmetry factor of up to +0.027, the first reported for CMA complexes. This success originates from the limited ligand-ligand rotation freedom and asymmetrical packing pattern (helical structure) of the CMA enantiomers in the crystals. Moreover, these Cu-I enantiomers displayed inspiring aggregation-dependent thermally activated delayed fluorescence properties. These findings bring new insights into the optical properties of chiral CMA complexes from the perspective of aggregation states.