Site-selective bromination of anthracene–maleimide Diels–Alder crystals for tunable afterglow and white light emission

Abstract

Efficient and color-tunable organic persistent room-temperature phosphorescence (p-RTP) is highly attractive for applications in colorful displays, advanced information encryption, and sensing. However, achieving such p-RTP remains challenging due to the lack of effective design strategies. Here, we introduce a synergistic chromophore-engineering approach that couples conventional and nonconventional luminophores to construct donor–acceptor adducts. These adducts exhibit dual fluorescence/p-RTP with pronounced excitation-dependent color tunability, even in crystals. Anthracene bromination (BAN/DBAN-MI) enhances SOC via the heavy-atom effect and increases Φ_p to 21.5% (DBAN-MI). By contrast, maleimide bromination (AN-BMI/AN-DBMI) reorganizes packing and redistributes through-space conjugation (TSC), enabling single-component white emission. Single-crystal analysis, femtosecond transient absorption spectroscopy, and theoretical calculations reveal how site-specific halogenation governs ISC and clustering-triggered emission (CTE) behaviors. This work establishes a general design principle for efficient and color-tunable organic p-RTP materials combining both aromatic and nonaromatic moieties through the CTE mechanism, highlighting their potential in multicolor displays and white-light illumination.