A novel on/off fluorescent rhodamine-based hexapodal Fe(3+) 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; (1)H, (13)C, and (31)P NMR; and MALDI MS spectrometry. The optical sensor features for the Fe(3+) complex of L were investigated by UV-vis and fluorescence spectroscopy. The stoichiometry of L-Fe(3+) complex was found to be 1:3 (ligand/metal ion), and the detection limit of L was determined as 4.8 μM (0.27 mg L(-1)) for Fe(3+) ions. The reusability of the sensor was tested by the addition of ethylenediamine to L-Fe(3+) complex solutions followed by the addition of Fe(3+) solution.

The hexapodal Rhodamine B derivative compound 3 containing a cyclotriphosphazene core was synthesized and characterized by spectroscopic techniques such as FT-IR, (1)H, (13)C and (31)P NMR, HR-MS, MALDI MS and microanalysis. Compound 3 is a naked eye selective sensor with colorimetric and fluorescent properties for Hg(2+) ions in the presence of other metal ions such as Na(+), K(+), Ca(2+), Ba(2+), Mg(2+), Ag(+), Mn(2+), Cu(2+), Ni(2+), Co(2+), Pb(2+), Cd(2+), Zn(2+), Fe(2+), Fe(3+), and Cr(3+). The optical sensor properties of compound 3 were investigated using UV-vis and fluorescence spectroscopy. The lowest detection limit of compound 3 was determined as 3.76 × 10(-9) M (0.75 ppb) for Hg(2+) ions. The stoichiometry of compound 3-Hg(2+) complex was found to be 1:3 (ligand/metal ion). The reusable test strip was improved by the immobilization of compound 3 into a hydrogel network. The reusability of the sensor and test strip was tested with S(2-) ion solutions.

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