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Red Room-Temperature Phosphorescent Diimides: Molecular Design and Application

preprint
submitted on 09.09.2019, 08:49 and posted on 10.09.2019, 15:58 by Jiajun Du, Fan Liao, Ziye Wu, Wenhuan Huang, Fei Li, Jiaxiang Dou, Hui Miao, Xiaofeng Chen, Xuepeng Zhang, Jun Jiang, Guoqing Zhang
N-Substituted naphthalene diimides (NDIs) were explored as purely organic room temperature phosphorescence (RTP) materials based on the strategy of intramolecular charge-transfer (ICT) mediation. A series of NDIs were designed and investigated for their luminescence properties. All emissive NDIs exhibited similar red RTP (emission range from ~600 to ~800 nm) in solid state media; the quantum yield (QY) of the obtained RTP relies heavily on the N-substitution. From poor to moderate to strong donor moieties, the QY increases but suddenly disappears. First-principle calculations reveal that a “sweet spot” for strong NDI RTP exists: while a suitable charge-transfer state can enhance RTP, a strong donor may cause total triplet quenching through the photo-induced electron transfer (PET) mechanism. Furthermore, combining NDI aggregation effects, we realized the reddest RTP ever reported for purely organic materials (Max emission = 675 nm, QY = 21.7%). Given the red emission, respectable QY and oxygen sensitive properties for some of the NDIs, they were tested as imaging agents for in vivo imaging studies.

History

Email Address of Submitting Author

jddu@caltech.edu

Institution

University of Science and Technology of China

Country

China

ORCID For Submitting Author

0000-0003-2693-834X

Declaration of Conflict of Interest

No conflict of interest

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