Synthesis of novel fluorinated coumarins: Excellent UV-light excitable fluorescent dyes

Two new fluorinated fluorescent dyes, 6,8-difluoro-7-hydroxy-4-methylcoumarin (Marina BlueTM) and 3-carboxy-6,8-difluoro-7-hydroxycoumarin (Pacific BlueTM), exhibit excellent photophysical properties among a series of novel fluorinated 7-hydroxycoumarins. Most of these fluorinated coumarins have quantum yields (0.63 to 0.89) equal to or higher than that of the parent compound (0.63), which, in combination with their lower pKas and higher photostability, make them superior fluorescent dyes for use as reporter molecules in biological systems.