The first tryptophan based turn-off chemosensor for Fe2+ ion detection.

Abstract In this research work, we have designed and synthesized a novel Tryptophan-Quinoline conjugated turn-off chemosensor 4 for the selective detection of Fe2+ ion with high sensitivity (3.06 μM) among 21 metal cations such as Ag+, Ca+, Cs+, Cu+, K+, Na+, NH4+, Ba2+, Ca2+, Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Pb2+, Zn2+, Al3+, Au3+, Cr3+ and Fe3+ in DMF-HEPES (1 mM, pH = 7.0, 1:1, v/v) aqueous-organic solvent system. It showed a fluorescence quenching mechanism through the blocked PET process. The optical properties, binding mode of the metal ion with the receptor, plausible electron transfer mechanism, and its practical applications have been discussed. This work will open up a new avenue in amino acid-based Fe2+ ion sensors.