Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China.
Chemistry. 2019 Sep 25;25(54):12497-12501. doi: 10.1002/chem.201902882. Epub 2019 Sep 2.
N-Substituted naphthalimides (NNIs) have been shown to exhibit highly efficient and persistent room-temperature phosphorescence from an NNI-localized triplet excited state, when the N-substitution is a sufficiently strong donor and mediates an intramolecular charge-transfer (ICT) state upon photo-excitation. This work shows that, when the electron-donating ability of the N-substitution is further increased in the presence of a carbanion or phenoxide, spontaneous electron transfer (ET) occurs and results in radical anions, verified with electron-paramagnetic resonance (EPR) spectroscopy. However, the EPR-active anion is surprisingly persistent and impervious to nucleophilic and radical reactions under anionic conditions. The stability is thought to originate from an intramolecular spin pairing between the N-donor and the NI acceptor post ET, which is demonstrated in supramolecular chemistry.
N-取代萘酰亚胺（NNI）已被证明在 NNI 局域三重态激发态下表现出高效且持久的室温磷光，当 N 取代基是足够强的供体并在光激发时介导分子内电荷转移（ICT）态时。这项工作表明，当存在碳负离子或酚盐时，进一步增加 N 取代基的给电子能力，会发生自发电子转移（ET），并导致自由基阴离子，这可以通过电子顺磁共振（EPR）光谱来验证。然而，EPR 活性阴离子在阴离子条件下出人意料地稳定且不受亲核和自由基反应的影响。这种稳定性被认为源自 ET 后 N-供体和 NI 受体之间的分子内自旋配对，这在超分子化学中得到了证明。
