Effects of substituents on the optical properties of AIEE-active 9, 10-dithiopheneanthrylene derivatives and their applications in cell imaging

A series of asymmetric 9, 10-dithiopheneanthrylene derivatives (DTAs) with various substituent groups and large Stokes shifts (>80 nm) have been synthesized and characterized. All of them displayed aggregation-induced emission enhancement (AIEE) behaviors expect for DTA-M, which fluorescence was gradually enhanced in low water fraction (50%), but dramatically quenched with the increase of water fraction to 90% due to the twisted intramolecular charge transfer (TICT) effect. The size of particles in aggregates were studied by using a scanning electron microscope, indicating the formation of morphological diversity nanoparticles due to the various substituents on 2-position of lateral thiophene ring. Furthermore, all of them exhibited reversible mechanofluorochromic and vapochromic luminescence behaviors, especially compound DTA-M, which showed high color contrast mechanofluorochromism between yellow and red color. In addition to the AIEE and mechanofluorochromic properties, HeLa cells fluorescence imaging experiments proved that these DTAs are capable to achieving bioimaging.