Near-Infrared Thienoisoindigos with Aggregation-Induced Emission: Molecular Design, Optical Performance, and Bioimaging Application.

Thienoisoindigo as a popular conjugated skeleton has been constantly applied in the construction of organic optoelectronic materials. Exploring its new applications in fluorescent sensors and bioimaging is helpful to extend its potential. In this work, a thienoisoindigo fluorophore was first selected as a building block to be applied in the construction of the near-infrared fluorescent materials with an aggregation-induced emission manner through introducing triarylamine, thiophene-bridged triarylamine, and N,N-dimethyl styrene, respectively. These fluorescent agents showed the near-infrared emission and possessed typical aggregation-induced emission behavior. Although they had low band gaps and near-infrared emission, they presented remarkable photostability. Especially, thiophene-bridged triarylamine and N,N-dimethyl styrene-coated thienoisoindigos exhibited strong lysosomal targeting capability, and they could also serve for fluorescence imaging in vivo.