A Fluorinated Carbanionic Substituent for Improving Water Solubility and Lipophilicity of Fluorescent Dyes

Installation of a carbanionic substituent, that is strongly stabilized by two (trifluoromethyl)sulfonyl (Tf=SO2CF3) groups, into several fluorescence dyes including boron‐dipyrromethenes (BODIPYs), fluoresceins, and aminocoumarins has been achieved by the 2,2‐bis(triflyl)ethylation reaction of the dye frameworks with highly electrophilic Tf2C=CH2, followed by neutralization with NaHCO3. Despite the contradiction between water solubility and lipophilicity, the carbanion‐decorated dyes thus obtained showed significant enhancement of not only water solubility but also lipophilicity. This work clearly demonstrates that the fluorinated, highly stabilized carbanionic substituent is a new option for controlling the macroscopic property of chemical materials. A fluorinated carbanionic substituent enhanced both water solubility and lipophilicity of organic fluorescence dyes, including BODIPYs, fluorescein, and aminocoumarin, without impairing the photophysical properties of the parent fluorophores. Considering that incorporation of conventional ionic substituents reduces the lipophilicity, the present carbanion structure is a new and promising candidate to tune such macroscopic properties.