Aggregation-induced luminescence enhancement, anion sensing, solvent-selective fluorescence quenching of arylpyrazoline fluorescent probe

28 Novel pyrazoline compounds containing pyrazole units have been synthesized and characterized. The crystal structures of C1 and B6 showed that these pyrazoline derivatives could form 3D layered structures through face-to-face stacking of aromatic rings, and they were more inclined to form H-type aggregation in poor solvent. Compound C4 was selected as the standard sample to study their properties of aggregation-induced emission enhancement (AIEE) and reversible mechanical chromoluminescence (MFC) behaviors in THF/cyclohexane. And the results suggested the formation of H-type aggregation, and the RIR and RIV phenomenon in the aggregated state led to strong fluorescence emission behavior in high fc solvent. The analysis of fluorescence emission spectroscopy indicated that the fluorescence emission of C4 could be selectively quenched by chloroform. Meanwhile, compound C4 can selectively recognize NO3− in CH2Cl2. The studies of fluorescence quenching mechanism showed that compound C4 could be oxidized by oxygen in the air to form a new compound C4-1 in CHCl3 solvent or in the presence of NO3−, leading to the fluorescence quenching of C4. Density functional theory calculations also confirmed the results.