Colorimetric chemosensor for multi-signaling detection of metal ions using pyrrole based Schiff bases

Pyrrole based Schiff bases act as a highly sensitive probe for metal ions in aqueous medium. Both receptors R 1 and R 2 are sensitive towards Fe 3+ , Cu 2+ , Hg 2+ and Cr 3+ among the other metal ions. The sensing ability of the receptors are investigated via colorimetric, optical and emission spectroscopic studies. The binding stoichiometries of R 1 and R 2 with metal ions have been determined as 2:1 by using Job’s plot. The colorimetric receptors exhibited high sensitivity with a low detection limit of μM levels. In the presence of metal ions both receptors shows fluorescence quenching. This might be due to the photo induced electron transfer mechanism. The quenching constant was further determined using Stern–Volmer plot.