Boosting Solid-State Luminescence of Thiazolothiazole Viologen by Incorporating Metal Halide Clusters to Hinder π-Stacking.

A new strategy is developed herein to improve the solid fluorescence of thiazolothiazole viologen by using the ZnCl 4 2- cluster as a scaffold to hinder π-stacking. Importantly, the Cl···H bonds are formed in the solid state to sustain the framework and can be automatically dissociated when dissolved in H 2 O, thus having no impact on the strong emission in aqueous solution. As such, the first case of organic-inorganic viologen-zinc halide named 4PV·ZnCl 4 was designed and synthesized, and a significant increase in photoluminescence quantum yield (Φ F ) is realized from 4PV·2Br (Φ F = 0%) to 4PV·ZnCl 4 (Φ F = 27.0%) in solid and from 97% to 98% in H 2 O. 4PV·ZnCl 4 also displays pH stimuli-responsive naked-eye chromic behavior and photoluminescence with different coloring states and intensities. The multifunctional performance of 4PV·ZnCl 4 provides a prerequisite for carrying different information, expanding their promising application in multilevel information encryption.