Design and synthesis of a novel rhodamine-based chemosensor and recognition study to Fe3+

A fluorescent and colorimetric chemosensor Rh1 for Fe3+ was synthesized by condensation reaction of rhodamine B hydrochloride and 2-aminothiazole, and its structure was confirmed by NMR, IR, HRMS and crystal data. Upon coordination with Fe3+ in CH3CN-H2O (1:1, v/v) solution, the spirolactam of Rh1 is opened, which results in a dramatic enhancement of fluorescence intensity as well as the color change of the solution. Most importantly, other metal ions show no obvious interference with the detection of Fe3+. Under the optimum conditions described, the fluorescence intensity is linearly proportional to the concentration of Fe3+ in the range of 2 mu m similar to 7 mu m. The Job's plot indicates a 1:1 binding stoichiometry between Rh1 and Fe3+. The association constant (Ka) is 2.26 x 10(4) m(-1).