Three colorimetric and off-on fluorescent chemosensors for Fe3+ in aqueous media

Three Rhodamine B derivatives were synthesized and characterized by ESI-MS, NMR, HR-MS and IR. The probes exhibit high selectivity and sensitivity towards Fe(3+) over other metal ions in CH3CN-water. Upon the addition of Fe(3+), the spirocyclic ring of the probe was opened and a significant enhancement of visible color and fluorescence within the range of 540-700 nm was observed. The colorimetric and fluorescent response to Fe(3+) can be conveniently detected even by the naked eye, which provides a facile method for the visual detection of Fe(3+). Job's plot, fluorescence titration and MS indicated the formation of 1:2 complexes between the probes and Fe(3+). The reversibility of the reaction establishes the potential of these probes as chemosensors for Fe(3+) detection.