Highly Selective Colorimetric Fluorescent Sensor for Pb2+

Phenanthroline-based colorimetric sensors 1 and 2 have been designed, synthesized, and compared with phenanthrene-based receptor 3 for sensing of Pb2+ by color change. Receptor 1 imparts color change (from yellow to red) selectively with Pb2+ in acetonitrile/water (9:1) as well as in methanol/water (9:1) when in the presence of other metal ions studied (Li+, Na+, K+, Ca2+, Mg2+, Ba2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Mn2+ as their perchlorate salts). Receptor 1 also shows fluorescence enhancement upon addition of lead perchlorate in acetonitrile/water (9:1) solvent possibly due to the chelation enhanced fluorescence (CHEF) effect. However, the binding behavior of 2 with Pb2+ is found to be less effective compared to that of receptor 1.