Saccharin-derived multifunctional emitters featuring concurrently room temperature phosphorescence, thermally activated delayed fluorescence and aggregation-induced enhanced emission

Multifunctional luminescent materials simultaneously imparted with various emission properties are of great significance. To develop multifunctional luminescent materials, saccharin was introduced as a novel electron acceptor for the first time, resulting in three new luminogens, namely 6-Cz-Sac, 5-Cz-Sac, and DiCz-Sac. All the three luminogens exhibited aggregation-induced enhanced emission (AIEE) and ultralong room temperature phosphorescence (RTP) properties. An in-depth analysis on their stacking arrangements in single crystals reveals the abundant supramolecular interactions, with intermolecular hydrogen bonds resulting from the carbonyl and sulfone groups of saccharin unit. These close-distance intermolecular non-covalent interactions can effectively suppress the intramolecular motions and impede non-radiative decay channels, thus resulting in intense emission in aggregated states. Among the three emitters, the 5-Cz-Sac crystal showed more intermolecular non-covalent interactions through the planar carbazole units, compared with DiCz-Sac and 6-Cz-Sac, which leads to its excellent RTP properties with an ultralong lifetime of 664 ms. DiCz-Sac, with a multi-donor structure and the largest donor-acceptor twisted angles among the three emitters, exhibited thermally activated delayed fluorescence (TADF) characteristics in addition to AIEE and RTP. DiCz-Sac represents the first reported saccharinbased multifunctional luminogen concurrently exhibiting AIEE, RTP, and TADF. This work reveals that such a molecular design strategy is a promising platform for constructing multifunctional luminescent materials.