A highly sensitive and selective fluorescent probe for Fe3+ based on 2-(2-hydroxyphenyl)benzothiazole

A novel fluorescent Fe3+ probe (L)based on 2-(2-hydroxyphenyl)benzothiazole has been synthesized and characterized. Both UV-vis and fluorescence spectroscopic studies demonstrated that L was highly sensitive and selective towards Fe3+ over other metal ions in acetonitrile. Upon binding with Fe3+, the emission band of L red-shifted from 370 nm to 420 nm and the fluorescence intensity was enhanced ∼103-fold. The lowest detection limit for L is 6.04 × 10−8 M and the dissociation constants Kd is 1.13 × 10−11 M, which were calculated from the fluorescence titration curves. The detailed UV-vis and fluorescent titrations studies suggested that the binding stoichiometry of the L–Fe3+ complex was 2 : 1, and the structure between L and the Fe3+ complex was confirmed by the 1H NMR titration. Then IR spectra provided further proof of the binding mode of the L–Fe3+ complex.