A near-infrared AIEE fluorescent chemosensor for Cu2+ through an IPT process

A near-infrared AIEE fluorescent chemosensor 2-(2-(4-(((3-methyl-5-oxo-1- phenyl-4,5-dihydro-1H-pyrazol-4-yl) methylene)amino)styryl)-4H-chromen-4-ylidene)malono- nitrile (HL1) was synthesized. In DMSO solution, HL1 showed fluorescence emission at 570 nm, and the fluorescence emission peak red shifted to 675 nm with the addition of H2O, which was attributed to the tautomerism of ketone (K) and enol (E) caused by intramolecular proton transfer (IPT) and aggregation-induced emission enhancement (AIEE). For comparison, 2-(2-(4-(((1phenyl-1H-pyrazol-4-yl)methylene)amino)styryl)-4H-chromen-4-ylidene)malononitrile (HL) without C--O was synthesized. The results show that HL cannot coordinate with metal ions due to the absence of C--O, but AIEE effect also exists. The sensor HL1 can coordinate with Cu2+ to cause fluorescence quenching in the near-infrared region, and the fluorescence intensity recovered after the addition of Na(2)EDTA, indicating that the probe HL1 can reversibly recognize Cu2+. Job's curve showed that the stoichiometric ratio of HL1 to Cu2+ was 1:1, and the detection limit for Cu2+ could reach at 4.68 x 10(-8)center dot mol center dot L-1 level. The experimental results are verified by theoretical calculation. In addition, the probe HL1 can be used to detect Cu2+ in actual drinking water.