Clustering and Halogen Effects Enabled Red/Near-Infrared Room Temperature Phosphorescence from Aliphatic Cyclic Imides

Pure organics with room temperature phosphorescence (RTP) are urgently demanded in advanced optoelectronic and bioelectronic applications. However, currently reported phosphors are mostly aromatics and restricted to blue to orange colors. It remains an enormous challenge to achieve red and near-infrared (NIR) RTP, particularly for those from nonaromatics. Here we demonstrate a series of cyclic imides derived from succinimide, which can emit red (665, 690 nm) and even NIR (745 nm) RTP with outstanding efficiencies of up to 9.2%, despite their rather limited molecular conjugations. Such unique emission should be ascribed to the presence of the imide unit and heavy atoms, effective molecular clustering, and the electron delocalization of halogens, which not only greatly facilitate intersystem crossing, but also afford significantly extended through-space conjugation and rigidified conformations. These results pave the way to the rational construction of red and NIR nonconventional luminophores through synergistic clustering and halogen effects.