Red aqueous room-temperature phosphorescence modulated by anion-π and intermolecular electronic coupling interactions

作者：Liu, Fengbo; Yang, Hai; Sun, Dongdong; Gao, Fang; Zhang, Xiongzhi; Zhao, Zhiyong; Han, Xie; Liu, Simin^*

来源：Chemical Science, 2022, 13(24): 7247-7255.

DOI：10.1039/d1sc06503c

• RECOGNITION
• PERSISTENT

Aqueous room temperature phosphorescence (aRTP) from purely organic materials has been intriguing but challenging. In this article, we demonstrated that the red aRTP emission of 2Br-NDI, a water-soluble 4,9-dibromonaphthalene diimide derivative as a chloride salt, could be modulated by anion-pi and intermolecular electronic coupling interactions in water. Specifically, the rarely reported stabilization of anion-pi interactions in water between Cl- and the 2Br-NDI core was experimentally evidenced by an anion-pi induced long-lived emission (lambda(Anion-pi)) of 2Br-NDI, acting as a competitive decay pathway against the intrinsic red aRTP emission (lambda(Phos)) of 2Br-NDI. In the initial expectation of enhancing the aRTP of 2Br-NDI by inclusion complexation with macrocyclic cucurbit[n]urils (CB[n]s, n = 7, 8, 10), we surprisingly found that the exclusion complexation between CB[8] and 2Br-NDI unconventionally endowed the complex with the strongest and longest-lived aRTP due to the strong intermolecular electronic coupling between the n pi* orbit on the carbonyl rims of CB[8] and the pi pi* orbit on 2Br-NDI in water. It is anticipated that these intriguing findings may inspire and expand the exploration of aqueous anion-pi recognition and CB[n]-based aRTP materials.