A new intramolecular charge transfer receptor as a selective ratiometric 'off-on' sensor for Zn2+

Probe 3 displays a highly selective photophysical response in the presence of Zn2+ with the absorption maxima of 3 being red shifted by 84 nm and the fluorescence output enhanced by 13 fold. The binding interaction follows the order Zn2+ > Cd2+ > Mg2+ > Ba2+ > Ca2+ > K+ ≅ Na+ ≅ Li+.