Multiresponsive Tetra-Arylethene-Based Fluorescent Switch with Multicolored Changes: Single-Crystal Photochromism, Mechanochromism, and Acidichromism

In this article, we report a simple tetra-arylethenebased fluorescent switch TPS=C4 modified with a flexible alkyl chain by the Schiff base structure. The incorporation of C=N retains the excellent photochromic property of tetra-arylethene and endows TPS=C4 with new multiresponsiveness of mechanochromism and acidichromism and multicolor changes. TPS=C4 shows remarkable mechanochromism from a deep blue emission at 420 nm to bright blue with a new shoulder band at 450 nm, which arises from the force-induced phase transition from the crystal state to an amorphous form. Both the original crystalline powder and the ground amorphous sample exhibit interesting acidichromism, and their emission colors turn yellow (530 nm), due to the protonation of C=N. More interestingly, TPS=C4 displays fascinating photochromism in multiple states, especially in the single-crystal state. The flexible alkyl chain offers enough free space for molecular motion and facilitates single-crystal photochromism. Due to the multiresponsiveness and multicolor switch, TPS=C4 can be satisfactorily used for the multidimensional anticounterfeiting application. To the best of our knowledge, TPS=C4 is a rare multifunctional molecule with a simple structure but featuring multiresponsiveness and multicolor switch.

Automated summary

In this article, a simple fluorescent switch TPS=C4 based on tetra-arylethene modified with a flexible alkyl chain by the Schiff base structure was reported. TPS=C4 exhibits remarkable mechanochromism and acidichromism, along with multiple photochromic states, especially in the single-crystal state. The multifunctional molecule TPS=C4 with multiresponsiveness and multicolor switch is suitable for multidimensional anticounterfeiting applications.