Polymorphism-dependent fluorescent emission, acid/base response and selective fluorescent sensor for Cu2+ ions based on single-benzene framework

In this work, polymorphic manipulation is applied to regulate the fluorescence emission of multi-function crystalline materials, which provides an efficient strategy for regulating photophysical properties of luminescent materials. The tetrasubstituted dimethyl 2,5-bis((3-chloropropyl)amino)-terephthalate was designed and synthesized and two polymorphs of it were discovered. The inherent mechanism of polymorphism-dependent emission of Form 1 (597 nm) and Form 2 (630 nm) was investigated by the combination of XPS and crystal structure analysis. Furthermore, the optical properties and acid/base vapor stimulus responsive properties were carefully investigated in both solution and solid state. And it exhibits significant selective fluorescence quenching in the presence of Cu2+ ions and displays good linear correlation with the concentration of Cu2+, which can be utilized for the detection and measurement of Cu2+.