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-π and intermolecular electronic coupling interactions in water. Specifically, the rarely reported stabilization of anion-π interactions in water between Cl- and the 2Br-NDI core was experimentally evidenced by an anion-π induced long-lived emission (λ Anion-π) of 2Br-NDI, acting as a competitive decay pathway against the intrinsic red aRTP emission (λ 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 nπ* orbit on the carbonyl rims of CB[8] and the ππ* orbit on 2Br-NDI in water. It is anticipated that these intriguing findings may inspire and expand the exploration of aqueous anion-π recognition and CB[n]-based aRTP materials.
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