The synthesis of a rhodamine B schiff-base chemosensor and recognition properties for Fe3+ in neutral ethanol aqueous solution

A new rhodamine B schiff-base fluorescent sensor (1) was synthesized by a one-step condensation reaction of rhodamine B ethylenediamine and acetylacetone. The structure of 1 was characterized by single crystal X-ray crystallography, 1H NMR, MS and IR spectroscopy. Studying its fluorogenic and colorimetric behaviors towards various metal ions, high sensitivity and selectivity were achieved for Fe3+ over other commonly coexistent metal ions, which were accompanied by ring opening of a rhodamine spirocycle framework. In the ethanol aqueous medium (v/v = 4/6, Tris–HCl buffer, pH = 7.0), the presence of Fe3+ induces the formation of a 1-ion complex, which was deduced by spectroscopy, HPLC and electrochemical methods. The limit of detection for Fe3+ determinations was low to 0.11 μM (fluorescence measurement) and 1.6 μM (UV–vis measurement), respectively, indicating the potential application of 1 for the determination of trace Fe3+ ions in neutral medium.