A Visual and Ratiometric Chemosensor Using Thiophene Functionalized Hydrazone for the Selective Sensing of Pb2+ and F- Ions.

Herein, a simple, efficient ratiometric chemosensor was reported for the selective sensing of Pb2+ and F- ions using thiophene functionalized hydrazone as a chemical probe. Hydrazone moiety was developed by utilizing thiophene/naphthalene as a platform for the particular recognition of cation and anion. The structures of the precursor (Z)-(1-(5-bromothiophen-2-yl)ethylidene)hydrazine (ABTH) and the final probe 1-((Z)-(((Z)-1-(5-bromothiophen-2-yl)ethylidene)hydrazono)methyl)naphthalen-2-ol (NAPABTH) were confirmed by 1H, 13C-NMR and LC-MS spectroscopic methods. The interaction of NAPABTH with Pb2+ and F- ions was visually observed by the formation of pink and dark yellow solutions, respectively. The detection limits were found to be very low for Pb2+ as 1.06 ppm and for F- ions as 3.72 nM. This visual detection of Pb2+/F- ions with satisfactory outcomes obtained from UV-Vis titrations. The sensing mechanistic pathways and stoichiometric ratios were obtained from DFT and Job's plot, respectively. The observed results are highly promising as highly selective chemosensor with lower detection limits for Pb2+ and F- ions. This strategy could exhibit tremendous applications for the selective sensing of heavy metal cations with rapid sensitivity for the design of new devices.