Stimuli-responsive 2,6-diarylethene-4H-pyran-4-one derivatives: Aggregation induced emission enhancement, mechanochromism and solvatochromism

A series of 2,6-diarylethene-4H-pyran-4-one organic functional materials (pp-s) were designed and successfully synthesized, characterized by PL spectra. It was found that all of them displayed the aggregation induced emission enhancement (AIEE) phenomenon, and three of them presented different emission spectra in different solvents i.e. solvatochromism, which was confirmed by density functional theory (DFT) calculation on the ICT process. Remarkably, an inverted U-shaped mechanochromic behavior (MFC) and red-shifted phenomenon of their emission spectra (bathochromism) was observed along with the increasing of conjugation degree. In which, the compound containing triphenylamine units (pp-3) showcasing the best MFC nature. PXRD profiles indicated the transformation between two different crystalline states upon grinding. Thus, we offer a way to manipulate the chromism performance via conjugation-regulating strategy.