We describe the design, synthesis and characterization of
five high Stokes shift quadrupolar heteroaryl compounds suitable
as fluorescent probes in bio-imaging. In particular, we
characterize the photophysical properties and the intracellular
localization in Human Umbilical Vein Endothelial Cells
(HUVEC) and Human Mesenchymal Stem Cells (HMSCs) for
each dye. We show that, amongst all of the investigated
derivatives, the 2,5-bis[1-(4-N-methylpyridinium)ethen-2-yl)]-
N-methylpyrrole salt is the best candidates as selective mitochondrial
tracker. Finally, we recorded the full emission spectrum
of the most performing - exclusively mitochondrial selective
- fluorescent probe directly from HUVEC stained cells.
The emission spectrum collected from the stained mitochondria
shows a remarkably more pronounced vibronic structure
with respect to the emission of the free fluorophore in solution.