D-π-A type carbazole and triphenylamine derivatives with different π-conjugated units: Tunable aggregation-induced emission (AIE) and mechanofluorochromic properties

Eight donor-pi-acceptor (D-pi-A) skeleton high brightness luminogens 1-8 with various it-conjugated units are designed, synthesized, and fully characterized. Among synthetic luminophores, 7 and 8 possess typical aggregation-induced emission properties, and these reported fluorophores display different fluorescence in the solid state. Meanwhile, their solid-state emission behaviors can be effectively regulated by mechanical grinding except for solids 5 and 7. More specifically, the solid-state fluorescence of D-pi-A type compounds 1, 3, 4, and 6 can be reversibly switched by successive mechanical grinding and solvent fuming, while D-pi-A type compounds 2 and 8 display irreversible mechanofluorochromism behaviors. Remarkably, when the pristine powders of these mechanical force-responsive fluorophores are ground, 1 and 2 exhibit an obvious blue-shift, while 3, 4, 6, and 8 show a red-shift. The powder X-ray diffraction measurements demonstrate that these observed diverse mechanoresponsive fluorescence phenomena are attributed to the different morphological interconersion between the crystalline and amorphous states.

Automated summary

The synthesis of eight donor-pi-acceptor (D-pi-A) skeleton high brightness luminogens with different it-conjugated units showed that their solid-state emission behaviors can be effectively regulated by mechanical grinding and solvent fuming, with different morphological interconversion between crystalline and amorphous states accounting for the diverse mechanoresponsive fluorescence phenomena.