Aqueous Nanoaggregation-Enhanced One- and Two-Photon Fluorescence, Crystalline J-Aggregation-Induced Red Shift, and Amplified Spontaneous Emission of 9,10-Bis(p-dimethylaminostyryl)anthracene

We have synthesized two 9,10-bis(p-dialkylaminostyryl)anthracene derivatives, 9,10-bis(p-dimethylaminostyryl)anthracene (9,10-MADSA), and 9,10-bis(p-dipropylaminostyryl)anthracene (9,10-PADSA), and the photophysical properties in solution, aqueous suspension, and crystalline state are comparatively investigated. Their twisted conjugated skeleton and D-pi-D pattern make the molecular solution show weak fluorescence and the aqueous suspension exhibit aggregation-induced one- and two-photon emission. The crystals of 9,10-MADSA display high fluorescence efficiency (59.4%) and unusual red-shifted emission (586 nm) compared with that in solution and aqueous suspension, which is different from its homologue 9,10-PADSA that is yellow-emitting crystal (553 nm) with the fluorescence efficiency of 29.2%. Moreover, the amplified spontaneous emission effect is observed only from the single crystal of 9,10-MADSA. The origin of these unique photophysical properties for 9,10-MADSA crystals is ascribed to its specific packing mode, J-aggregation. This work demonstrates that the subtle manipulation of end groups of 9,10-divinylanthracene derivatives could significantly influence the molecular packing in crystals and endow them with novel optical properties.