A selective N,N-dithenoyl-rhodamine based fluorescent probe for Fe3+ detection in aqueous and living cells.

A novel N,N-dithenoyl-rhodamine based fluorescent and colorimetric Fe3+ probe 1 was designed and synthesized by only one step from Rhodamine B hydrazide and 2-thiophenecarbonyl chloride. The structure of probe 1 was characterized by 1H NMR/13C NMR spectroscopy, IR spectroscopy, and HRMS spectrometry. Accompanying with significant changes in visual color and fluorescent spectrum, probe 1 displayed good sensitivity for Fe3+ with an abroad pH span. The detection limit (3.76 μmol/L, 0.2 mg/L) for Fe3+ was lower than WHO recommended value (0.3 mg/L) for drinking water. Using two thiophene carbonyl groups as coordinating functional recognition group, probe 1 showed excellent selectivity towards Fe3+ over diverse coexistent metal ions and anions. The sensing mechanism between dithenoyl-substituted probe 1 and Fe3+ was further confirmed by 1H NMR and IR titration experiments, binding constants study, and Job's plot analysis. Furthermore, probe 1 also exhibited good cell membrane permeability and could be used as an efficient Fe3+ probe in living human cells.