Synthesis and biological application of a water-soluble fluorescent probe for Fe3+ based on sodium benzo[c]chromene-2-sulfonate

Four water-soluble sodium 8-carboxy-7-hydroxy-6-oxo-6H-benzo[c]chromene-2-sulfonates (2a-2d) were pre-pared and structurally characterized by H-1 NMR, C-13 NMR and HRMS-ESI spectra. The experimental results showed that 2a-2d were new water-soluble photoluminescent materials with strong photoluminescence prop-erty, large quantum yield and Stokes shift. In view of the high fluorescence quantum efficiency, 8-carboxy-7-hydroxy-3-methoxy-6-oxo-6H-benzo[c]chromene-2-sulfonate (2b, Phi = 0.74) was applied to the detection of Fe3+ in water solution. And probe 2b not only exhibited a naked-eye color change from colorless to pink, but also displayed highly selective turn-off'' probe for Fe3+ with detection limit of 1.72 umol/L in comparison to Na+, K+, Ag+, Ca2+, Cd2+, Co2+, Cu2+, Mg2+, Ni2+, Pb2+, Zn2+, Al3+ and Cr3+ cations in Tris-HCl buffer solution (pH 7.24). Futhermore, the binding stoichiometry of 2b with Fe3+ was determined to be 1:1 by Job's plot. Because of the good water-solubility and strong fluorescence in physiological pH, 2b was applied in monitoring intracellular Fe3+ of living Ramos cells successfully.