A highly selective ratiometric fluorescent chemosensor for Zn2+ ion based on a polyimine macrocycle

A new ratiometric fluorescent chemosensor based on a polyimine macrocycle ligand 1 has been synthesized. The chemosensor can exhibit a pronounced fluorescence response and high selectivity to Zn2+ ion over other 15 metal ions, including Cd2+. Sensor 1 appears an emission peak at 370 nm. Upon the addition of Zn2+ ion, the typical emission peak for 1 at 370 nm is obviously quenched, but a new emission peak at around 470 nm appears and shows a large enhancement due to the formation of a 1:1 Zn2+-1 complex. In addition, there is a good linear relationship between the fluorescence ratio I470nm/I370nm and the concentration of Zn2+, which makes a ratiometric assay of Zn2+ ion possible.