A novel reversible fluorescent probe for Zinc(II) ion and bioimaging in living cells

A simple Schiff-base fluorescent probe (L) was synthesised for selective detection of Zn2+ ion in CH3CN/HEPES solution (1/1, 10.0 μM, pH = 7.0). The probe L showed highly fluorescence enhancement towards Zn2+ over other metal ions with obvious fluorescence colour change from faint yellow to blue, which should be attributed to the formation of a 1:2 ligand-metal complex resulting in the inhibition of intramolecular charge transfer (ICT) and the chelation-enhanced fluorescence (CHEF) process. The bonding mechanism was confirmed by UV-vis, fluorescence, HRMS, 1 H NMR experiments and theoretical calculation. Reversibility of the probe in its binding with Zn2+ ion was established in the presence of EDTA. Furthermore, the fluorescence imaging indicated that probe L could be used to effectively identify Zn2+ in living cells.