Deep-Red Emissive Crescent-Shaped Fluorescent Dyes: Substituent Effect on Live Cell Imaging

A series of crescent-shaped fluorescent
dyes (CP1–CP6) were synthesized by
hybridizing coumarin and pyronin moieties with different amino substituents
at both ends. The molecular structures and photophysical properties
of these fluorescent dyes were investigated through X-ray diffraction,
absorption spectroscopy, and fluorescence spectroscopy. Results show
that the fluorescent dyes exhibited crescent-shaped structures, deep-red
emissions (approximately 650 nm), and significant Stokes shifts. In
live-cell-imaging experiments, CP1 stains mitochondria,
whereas CP3 and CP6 stain the lysosomes
in a cytoplasm and the RNA in nucleoli. The relationships between
different amino substituent groups and the imaging properties of CP dyes were discussed as well. Additionally, findings from
the cytotoxicity and photostability experiments on living cells indicated
the favorable biocompatibility and high photostability of the CP dyes.