Phosphazene Based Multicentered Naked-Eye Fluorescent Sensor with High Selectivity for Fe3+ Ions

A novel on/off fluorescent rhodamine-based hexapodal Fe3+ probe (L) containing a cyclotriphosphazene core was synthesized by an azide-alkyne "click-reaction". The synthesized compounds (1-5 and L) were characterized by FT-IR; H-1, C-13, and P-31 NMR; and MALDI MS spectrometry. The optical sensor features for the Fe3+ complex of L were investigated by UV-vis and fluorescence spectroscopy. The stoichiometry of L-Fe3+ complex was found to be 1:3 (ligand/metal ion), and the detection limit of L was determined as 4.8 mu M (0.27 mg L-1) for Fe3+ ions. The reusability of the sensor was tested by the addition of ethylenediamine to L-Fe3+ complex solutions followed by the addition of Fe3+ solution.