Finely regulated benzothiadiazole derivatives: Aggregation-induced emission (AIE), hypso- or bathochromic mechanofluorochromic behaviors, and multilevel information encryption applications

Six fluorescent dyes containing the same central benzothiadiazole skeleton were synthesized. Fluorogenic compounds 1 and 2 demonstrated typical aggregation-induced emission enhancement and aggregation-induced emission phenomena. These benzothiadiazole-modified dyes emitted different crystal-state fluorescence including green, yellow-green, yellowish brown, orange red and red colors, and these compounds displayed contrasting force-responsive fluorescence characteristics. More specifically, compound 1 exhibited red-shifted mechanofluorochromism behavior, and compounds 4–6 exhibited blue-shifted mechanofluorochromism phenomena, while compounds 2 and 3 showed no fluorescence change under mechanical stimulation. Among these benzothiadiazole derivatives, luminogens 1 and 6 presented mechanically triggered high-contrast bathochromic and hypsochromic fluorescence responses, respectively. Based on their various crystal fluorescence and force-sensitive emissive properties of fluorogenic molecules 1–6, an interesting multilevel information encryption system was successfully constructed. Indeed, this study not only provided a valuable reference for the preparation of luminophores possessing rich mechanoluminochromic natures, but also extended ideas for the development of advanced information encryption systems.