Characterization of Push-Pull-Type Benzo[X]quinoline Derivatives (X = or ): Environmentally Responsive Fluorescent Dyes with Multiple Functions.

Benzo[X]quinoline (X = or : ) derivatives bearing bis-trifluoromethyl and amine groups have been designed as push-pull-type fluorescent dyes. Through the synthesis of derivatives from 2,7-diaminonaphthalene, linear-type () and angular-type () structural isomers were obtained. X-ray structures of single crystals from six given derivatives revealed that the and series adopt planar- and bowl-shaped structures. In the fluorescence spectra, interestingly, the series emitted in the near-infrared region over 700 nm in polar solvents. Based on the visible absorptions and base properties related to the amine moiety, the ammonia responsiveness was investigated using an ion-exchange reaction by the salt. By exploiting the environmentally responsive fluorescence probe, cell imaging through confocal laser microscopy was conducted using HeLa and 3T3-L1 cells, emitting specific lipid droplets. The results indicate that derivatives have multiple functions and may be applied in materials chemistry and biochemistry.