A relay identification fluorescence probe for Fe³⁺ and phosphate anion and its applications

A simple relay identification fluorescence probe for Fe³⁺ and phosphate anion with "on-off-on" switching was designed and synthesized based on the phenylthiazole and biphenylcarbonitrile. Probe 1 displayed highly selective and sensitive recognition to Fe³⁺ in HEPES aqueous buffer (EtOH/H₂O=2:8, v/v, pH=7.4) solutions. The optimized structures and HOMO and LUMO of probe 1 and [1-Fe³⁺] complex were obtained by the density functional theory (DFT) calculations with B3LYP as the exchange and correlation functional using a suite of Gaussian 09 programs. The [1-Fe³⁺] complex solution also showed a high selectivity toward PO₄^3-. The lower limits of detection of probe 1 to Fe³⁺ and [1-Fe³⁺] complex to PO₄^3- were estimated to 1.09×10^-7M and 1.86×10^-7M. Besides, the probe 1 also was used to detected the target ions in real water sample and living cells successfully.