Tetraphenylethene or triphenylethylene-based luminophors: Tunable aggregation-induced emission (AIE), solid-state fluorescence and mechanofluorochromic characteristics

Four newly synthesized tetraphenylethene or triphenylethylene-modified fluorescent dyes were reported. All synthesized luminophores displayed typical aggregation-induced emission effects, with bright and varying aggregative-state emission involving multiple fluorescence colors containing yellow, orange, green, and yellow-green. In addition, these luminogens also showed different fluorescence in the solid state. Meanwhile, their solid-state fluorescence could be effectively switched by mechanical grinding and solvent fuming except for luminogen 4. More specifically, luminogen 1 exhibited a weak mechanofluorochromic response with a color change from yellow to yellowish brown, whereas luminogen 4 displayed negligible mechanofluorochromism behavior. In stark contrast to luminogens 1 and 4, luminogens 2 and 3 in the solid state were characterized by reversible high-contrast mechanochromic phenomena involving distinct fluorescent color changes from green to orange and from blue to yellow, respectively. These contrasting fluorescence changes were due to the morphological conversion from stable crystalline state to metastable amorphous state.