Quinoline-fused BODIPY with large Stokes shift as near-infrared dye for cell imaging

A new BODIPY dye was synthesized by fusing quinoline with BODIPY core by oxidative cyclodehydrogenation reaction, and the spectral properties of this dye were investigated. It displayed remarkable red shift in absorption and emission spectra compared with its precursor. Especially, the maximum emission peak of the fused dye reached to the near-infrared region. The red-shifted spectrum was ascribed to the expansion of molecular electron system. Meanwhile, due to the reduction of molecular symmetry, the quantum yield of the fused dye in dichloromethane was 41% and Stokes shift was 67 nm. Moreover, the results of cell imaging showed that the fused dye could be a candidate chromophore in organisms due to its good imaging effect, high photostability and low cytotoxicity. In addition, the fused dye exhibited a quantum yield of 0.12 in solid state.