Selective and sensitive fluorescent turn-off chemosensors for Fe3+.

Two novel chemosensors (2a and 2b) were synthesized by facile condensation of the binding unit (L-histidine) and the fluorophores (anthracene and dansyl groups). Both of them displayed high selectivity and sensitivity towards Fe(3+) over other metal ions in aqueous solution. The sensing mechanism was based on the paramagnetic property of Fe(3+) that would lead to fluorescence quenching of the fluorophores when Fe(3+) was bound to the recognition units. The results showed that l-histidine was a good coordination motif for Fe(3+) and both the anthracene and dansyl groups can sensitively report the sensing information.