Tunable Naphthalimide/Cinnoline-Fused (CinNapht) Hybrid Dyes for Fluorescence Imaging in Living Cells

This paper presents the synthesis, photophysical characterization and use for cell imaging of 14 fluorophores derived from a hybrid Naphthalimide/Cinnoline fused backbone called "CinNapht". Photophysical properties of these fluorophores including absorbance, excitation and emission spectra have been recorded in CHCl3, DMSO and PBS +5%BSA. They exhibit red emission associated to a large Stokes shift and fluorescence quantum yields up to 52%. Theoretical calculations have been undertaken in order to provide elements of rationalization for a major part of the results. Some of these analogues have been tuned to enable imaging of cell organelles such as mitochondria, lysosome or lipid droplets. This study comes to confirm that CinNapht dyes can be considered as relevant alternatives to existing tools for cell imaging.