Constructing small molecular AIE luminophores through a 2,2-(2,2-diphenylethene-1,1-diyl)dithiophene core and peripheral triphenylamine with applications in piezofluorochromism, optical waveguides, and explosive detection

In this work, we employ the Corey-Fuchs reaction followed by coupling reactions to develop a series of π-conjugated aggregation-induced emission (AIE) small-molecule luminophores (DT2A, DT3A and DT4A) through a 2,2-(2,2-diphenylethene-1,1-diyl)dithiophene (DPDT) core with different amounts and different strengths of TPA peripheral moieties. Interestingly, these molecules give obviously higher solid fluorescent quantum efficiency and AIE phenomena. In particular, the thin film of DT3A exhibited the highest fluorescent quantum efficiency of ca. 25% and the DT2A showed the highest α_AIE of 78. Moreover, the excellent optical waveguide applications of DT2A and DT4A were achieved because of their excellent self-assembly properties. Meanwhile, piezofluorochromic behavior with a large red shift of 35 nm only appeared when DT4A was ground using a pestle, because DT4A inserted more TPA and changed the twisting conformation. The piezofluorochromic behavior can be recovered to its original color by fuming with solvent. Finally, DT2A and DT4A were utilized as fluorescent probes to detect nitroaromatic/nitroaliphatic compounds and showed evident fluorescence quenching. These results indicate a huge potential to develop bright AIEgens based on DPDT core units and also provide insights into understanding how piezofluorochromism, optical waveguides and explosive detection properties are influenced by alternating the spatial symmetry of AIE materials with different numbers of TPA terminal groups.