Coordination properties of a Schiff base probe for Zn2+ ion in aqueous media having no Cu2+ ion interference

• The rational design of simple and low-cost highly selective sensors is presented.
• Zn2+ ion versus Cu2+ ion interference.
• A turn-on fluorescent Zn2+ ion sensor in the presence Cu2+ ion.
• The enol–imine and keto–enamine tautomerization directs ion selectivity.

The coordination properties and acid–base behavior of 2-[{(1S,2R)-1-hydroxy-1-phenylpropan-2-ylimino}methyl]-4-bromophenol Schiff base probe (L1) were characterized by UV–Vis and fluorescence titrations in water. The dissociation constants for the ligand account for a keto–enamine tautomer at pH 7. Detailed complexation studies were carried out, observing the formation of stable 1:1 complex for Zn2+, where a “turn-on” fluorescence effect is obtained. More importantly, no Cu2+ interference is observed, which is a typical problem for Zn2+ probes, this is awarded to the keto–enamine tautomeric form of the probe L1 according to UV–Vis and X-ray structure data. Also, the Zn2+vs. Cd2+ ion discrimination for L1 is proved. Finally, TD-DFT theoretical calculations were conducted in order to stablish the detection mechanism of the probe.

2-[{(1S,2R)-1-Hydroxy-1-phenylpropan-2-ylimino}methyl]-4-bromophenol Schiff base probes bind Zn2+ ion with excellent selective fluorescence response in aqueous media, even in the presence of large amounts of Cu2+ ion.Figure optionsDownload as PowerPoint slide