3-Aroylbenzocoumarin-Based Luminogens: Bright Solid-State Emission, AIE Properties and Cell Imaging Application.

A series of 3-aroylbenzocoumarin-based luminogens have been synthesized for investigating their aggregation-induced emission (AIE) and solid-state fluorescence. The single crystal X-ray diffraction analysis of one of them showed that the molecules are arranged in the form of π-dimers which may lead to excimer emission. The large Stokes shifts and the broad-band emission of these 3-aroylbenzocoumarins in solid/aggregation state demonstrated the probable formation of excimers. The shapes of benzocoumarin units have a great effect on the AIE behaviors. The linear benzocoumarin derivatives show larger Stokes shifts, while the bent-benzocoumarin derivatives exhibit better AIE performances. All of them show aggregation-enhanced excimer emission which is supported by the large Stokes shifts. The electronic effect of 3-aroyl groups also has a certain effect on their fluorescence properties. The polymorphism phenomenon was observed for one of the benzoyl-containing derivatives. Additionally, two of the derivatives containing methoxy group were successfully used for cell imaging.