New electron-donor/acceptor-substituted tetraphenylethylenes: aggregation-induced emission with tunable emission color and optical-waveguide behavior.

Herein, we report the synthesis of new tetraphenylethylene derivatives 1-5 that feature electron-donating (methoxy) and -accepting (dicyanomethane) groups as AIE-active molecules with tunable emission colors. The crystal structures of compounds 3 and 4 are described and the intermolecular interactions within their crystals agree with the observation that they exhibit strong solid-state emission. Compounds 1-4 exhibit typical AIE behavior and their emission maxima are red-shifted in the order: 1<2<3<4. Such red-shifts are ascribed to the fact that intramolecular interactions between the electron donor and the electron acceptor become stronger with increasing number of methoxy groups. The solid-state emission colors of compounds 1-4 are successfully tuned from yellow-green to red. Compound 5 shows AIE behavior, but its emission is only slightly enhanced after aggregation and its solid shows a low quantum yield. Furthermore, microplates of compound 3 exhibit 2D optical-waveguide behavior.