Ratiometric fluorescence sensing and intracellular imaging of Al3+ ions driven by an intramolecular excimer formation of a pyrimidine-pyrene scaffold.

An Al(3+) selective ratiometric fluorescent probe (L) has been synthesized by condensation of 4,5-diaminopyrimidine with 1-pyrenecarboxaldehyde. The structure of L has been confirmed by single crystal X-ray analysis. In the presence of Al(3+), L exhibits a considerable excimer emission at 445 nm along with the decrease of its monomer emission at 368 nm in DMSO-H2O (4 : 1, v/v). The lowest detection limit for Al(3+) is 0.24 μM. Furthermore, L can permeate through the cell membrane and detects intracellular Al(3+) ions under a fluorescence microscope.