An o-phthalimide-based multistimuli-responsive aggregation-induced emission (AIE) system

Aggregation-induced emission luminogens (AIEgens) have been widely used in the development of functional materials due to their excellent luminescence properties in the solid state. The development of new AIEgens is of great significance. In this work, a novel o-phthalimide-based AIEgen of 2,3-diphenylquinoxaline-6,7-dicarboimide (2) is reported, which exhibited multifunctional sensing applications. Interestingly, compound 2 exhibited ultrafast photo-response properties upon UV light irradiation in both the dissolved state and solid state, which was attributed to a unique photo-induced rearrangement reaction. This property of 2 makes it suitable for UV sensing and photo-patterning materials with a significant fluorescence change. Meanwhile, based on the highly specific interaction between Hg(ii) and the o-phthalimide moiety of 2, a complex of 2-Hg-2 formed in the presence of 0.5 equiv. Hg(ii), resulting in a strong fluorescence change of 2. The active hydrogen in the o-phthalimide moiety also makes the fluorescence of 2 sensitive to the pH of aqueous solutions. Due to these characteristics, 2 was successfully used in the detection of UV light, Hg(ii) and the pH of aqueous solutions, in which 2 exhibited satisfactory detection performance.