Pyrene-dithienylethene-tetra(tri)phenylethylene triads: Photocontrolled intramolecular energy transfer and photochromic fluorescence switching

Photochromic fluorescence switching with aggregation-induced emission (AIE) property has attracted great research interest due to their wide application potential in optical electronics and biomaterials. In this work, three novel pyrene-dithienylethene-tetra(tri)phenylethylene triads were synthesized by connecting triphenylethene (TrPE) or tetraphenylethylene (TPE) and pyrene unit via dithienlethene (DTE) bridge. Efficient photochromism and fluorescence switching were demonstrated in solution, aggregates, solid powder, and poly(methyl methacrylate) (PMMA) films under alternating irradiation with UV/visible light. The photocyclization yield of DTE-Py-3 was examined by 1H NMR spectra and calculated as 59%. Moreover, these three compounds exhibited typical AIE character in THF/water mixture, the photochromic and fluorescent switching behavior were explored in aggregated state with 90% water fraction. Furthermore, they could be utilized in application of optical information storage and ink with naked-eye color and fluorescence double channel, indicating the promising potential in anti-counterfeiting. Interestingly, DTE-Py-3 could be reversibly switched by visible light in both directions, which endowed it with the application in biological filed.