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Nonconventional luminophores without significant conjugations generally possess excitation-dependent photoluminescence (PL) owing to the coexistence of diverse clustered chromophores, which strongly implies the possibility of achieving color-tunable PL and/or persistent room temperature phosphorescence (p-RTP) from their crystals assisted by effective intermolecular interactions. Compared with traditional luminogens, however, nonconventional luminophores generally suffer from poor PL efficiencies. Here, inspired by the highly stable double-helix structure and multiple hydrogen bonds in DNA, we report a series of planar or twisted nonconventional luminophores based on hydantoin (HA), demonstrating unprecedentedly high PL/p-RTP efficiencies and p-RTP lifetimes of up to 87.5%/21.8% and 1.74 s, respectively, accompanying color-tunable p-RTP from sky-blue to yellowish-green. These findings will advance the exploitation of efficient nonconventional luminophores and provide deeper mechanistic insights into the origin of color-tunable p-RTP.

Pure organic luminogens with long-persistent luminescence have been extensively studied, on account of their fundamental research significance and diverse utilizations in anticounterfeiting, bioimaging, encryption, organic light-emitting diodes, chemo-sensing, etc. However, time-dependent color-tunable afterglow is rarely reported, especially for single-component materials. In this work, we reported an organic luminogen with time-dependent afterglow, namely, benzoyleneurea (BEU), with multiple persistent room-temperature phosphorescence (p-RTP) and thermally activated delayed fluorescence (TADF) in single crystals. While the lifetime of TADF is relatively short (~1.2 ms), those for p-RTP are as long as around 369~754 ms. The comparable but different decay rates of diversified p-RTP emissions endow BEU crystals with obvious time-dependent afterglow. The existence of multiple emissions can be reasonably illustrated by the clustering-triggered emission (CTE) mechanism. Single-crystal structure illustrates that the combination of benzene ring and nonconventional chromophores of ureide helps facilitate divergent intermolecular interactions, which contribute to the formation of varying emissive species. Moreover, its methyl- and chloro-substituted derivatives show similar multiple p-RTP emissions. However, no time-dependent afterglows are observed in their crystals, due to the highly approaching lifetimes. The afterglow color variation of BEU crystals grants its applications in advanced anticounterfeiting field and information encryption.

Persistent room-temperature phosphorescence (p-RTP) from pure organics is attractive due to its fundamental importance and potential applications in molecular imaging, sensing, encryption, anticounterfeiting, etc.1-4 Recently, efforts have been also made in obtaining color-tunable p-RTP in aromatic phosphors5 and nonconjugated polymers6,7. The origin of color-tunable p-RTP and the rational design of such luminogens, particularly those with explicit structure and molecular packing, remain challenging. Noteworthily, nonconventional luminophores without significant conjugations generally possess excitation-dependent photoluminescence (PL) because of the coexistence of diverse clustered chromophores6,8, which strongly implicates the possibility to achieve color-tunable p-RTP from their molecular crystals assisted by effective intermolecular interactions. Here, inspirited by the highly stable double-helix structure and multiple hydrogen bonds in DNA, we reported a series of nonconventional luminophores based on hydantoin (HA), which demonstrate excitation-dependent PL and color-tunable p-RTP from sky-blue to yellowish-green, accompanying unprecedentedly high PL and p-RTP efficiencies of up to 87.5% and 21.8%, respectively. Meanwhile, the p-RTP emissions are resistant to vigorous mechanical grinding, with lifetimes of up to 1.74 s. Such robust, color-tunable and highly efficient p-RTP render the luminophores promising for varying applications. These findings provide mechanism insights into the origin of color-tunable p-RTP, and surely advance the exploitation of efficient nonconventional luminophores.