D–π–A type AIE molecules exhibiting persistent room temperature phosphorescence and delayed fluorescence through structural regulation

Abstract

Three donor–π–acceptor (D–π–A) type pure organic luminescent molecules (CzBI-OBN, CzBI-OBIN, and CzBI-ONAN) exhibiting notable aggregation-induced emission (AIE) characteristics and multiple emissions of prompt fluorescence (PF), delayed fluorescence (DF), and room temperature phosphorescence (RTP) were designed and synthesized. Surprisingly, CzBI-OBN and CzBI-OBIN showed ultralong RTP lifetimes of 476.34 ms and 547.31 ms, respectively. CzBI-OBIN exhibited distinct dual-mode mechanochromic luminescence (MCL) properties due to the transition of the crystalline–amorphous state under external forces. Quantum-chemical calculations were used to explain different luminescence behaviors of the molecules, and further analysis via single-crystal X-ray diffraction revealed that strong intermolecular interactions and compact π–π stacking are crucial for phosphorescence emission. This study explores the luminescence mechanism of RTP through precise molecular structure control and demonstrates the potential applications of these diverse emission behaviors in fields such as anti-counterfeiting and information encryption.