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Polymorphic Pure Organic Luminogens with Through Space Conjugation and Persistent Room Temperature Phosphorescence
摘要： Pure organic luminogens with persistent room temperature phosphorescence (p-RTP) have attracted increasing attention owing to their fundamental significance and potential applications in security inks, bioimaging, and photodynamic therapy. Previous p-RTP luminogens are normally with through bond conjugation. In this work, we report a pure organic luminogen, AN-MA, the Diels-Alder cycloaddition adduct of anthracene (AN) and maleic anhydride (MA), which possesses isolated phenyls and anhydride moiety. AN-MA exhibits aggregation-enhanced emission (AEE) characteristics, with efficiency of ~2% and up to 8.5% in solution and crystals, respectively. Two polymorphs of AN-MA are readily obtained, which can generate UV emission from individual phenyl rings together with bright blue emission owing to the effective through space conjugation. Moreover, p-RTP with lifetime of up to ~1.6 s is obtained in crystals. These results not only disclose a new system with both fluorescence and RTP dual emission, but also suggest an alternative through space conjugation strategy towards pure organic p-RTP luminogens with tunable emissions.
关键词： anticounterfeiting,pure organic luminogens,persistent room temperature phosphorescence,through space conjugation,polymorphism
更新于2025-09-23 15:23:52
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Suppressed Triplet Exciton Diffusion Due to Small Orbital Overlap as a Key Design Factor for Ultralong-Lived Room-Temperature Phosphorescence in Molecular Crystals
摘要： Persistent room-temperature phosphorescence (RTP) under ambient conditions is attracting attention due to its strong potential for applications in bioimaging, sensing, or optical recording. Molecular packing leading to a rigid crystalline structure that minimizes nonradiative pathways from triplet state is often investigated for efficient RTP. However, for complex conjugated systems a key strategy to suppress the nonradiative deactivation is not found yet. Here, the origin of small rates of a nonradiative decay process from triplet states of conjugated molecular crystals showing RTP is reported. Optical microscopy analysis showed that, despite a favorable molecular stacking, an aromatic crystal with strong RTP is characterized by small diffusion length and small values of the diffusion coefficient of triplet excitons. Quantum chemical calculations reveal a large overlap between the lowest unoccupied molecular orbitals but very small overlap between the highest occupied molecular orbitals (HOMOs). Inefficient electron exchange caused by the small overlap of HOMOs prevents triplet excitons from diffusing over long distances and consequently from quenching at defect sites inside the crystal or at the crystal surface. These results will allow design of comprehensive molecular structures to obtain molecular solids with more efficient RTP.
关键词： suppressed nonradiative rate,persistent room-temperature phosphorescence,triplet exciton diffusion,molecular orbital overlap,fluorescence microscopy
更新于2025-09-23 15:23:52