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

Abstract

A new strategy is developed herein to improve the solid fluorescence of thiazolothiazole viologen by using the ZnCl₄^2- 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 H₂O, thus having no impact on the strong emission in aqueous solution. As such, the first case of organic-inorganic viologen-zinc halide named <b>4PV·ZnCl</b>_<b>4</b> was designed and synthesized, and a significant increase in photoluminescence quantum yield (Φ_F) is realized from <b>4PV·2Br</b> (Φ_F = 0%) to <b>4PV·ZnCl</b>_<b>4</b> (Φ_F = 27.0%) in solid and from 97% to 98% in H₂O. <b>4PV·ZnCl</b>_<b>4</b> also displays pH stimuli-responsive naked-eye chromic behavior and photoluminescence with different coloring states and intensities. The multifunctional performance of <b>4PV·ZnCl</b>_<b>4</b> provides a prerequisite for carrying different information, expanding their promising application in multilevel information encryption.