A turn-on and reversible fluorescence sensor for zinc ion

A simple Schiff base type fluorescent receptor 1 was prepared and evaluated for its fluorescence response to heavy metal ions. Receptor 1 exhibits an "off-on-type" mode with high selectivity in the presence of Zn 2+ ion. The addition of EDTA quenches the fluorescence of receptor 1-Zn2+ complex, making receptor 1 a reversible chemosensor. The selectivity of 1 for Zn2+ is the consequence of combined effects of CHEF, CN isomerization and inhibition of ESIPT.