Synthesis and properties of D-π-A triphenylamine derivatives with solvatochromism and bioimaging application

D-π-A type molecular structures often exhibit excellent photophysical properties due to intramolecular charge-transfer interactions. Herein, two donor-π-acceptor (D-π-A) type triphenylamine derivatives were designed and synthesized. These two compounds exhibited bright solid-state emission with orange-red fluorescence (compound 1, 620 nm) and near-infrared (NIR) fluorescence (compound 2, 650 nm). Moreover, the photophysical properties studies showed that these two compounds exhibited significant solvatochromism with different solvent polarity, indicating their effective intramolecular charge transfer. Furthermore, the two compounds showed remarkable aggregation-induced emission (AIE) effect, and compound 2 was more likely to form the aggregation state in the presence of less water. In addition, compared to compound 1, compound 2 only had a more sensitive response to high viscosity environments. These results indicate that the additional phenyl ring could be an alternative way to tune the fluorescence behaviors and provide a new strategy to design AIE-active and solvatochromism dyes. Finally, cell imaging experiments showed that these two compounds had the ability to be applied for bioimaging in living cells.