Luminescent Sm(III) complex bearing dynamic imine bonds as a multi-responsive fluorescent sensor for F− and PO43− anions together with Zn2+ cation in water samples

We have designed and synthesized a new luminescent mononuclear samarium (III) complex Sm-2h based on the [1 + 1] Schiff-base macrocycle H2L2h, derived from the cyclocondensation reaction between dialdehyde and diamine precursors, and its exact architecture is determined to be [Sm(HL2h) (NO3)2]. The sensing ability of complex Sm-2h is carefully evaluated for various common inorganic ions in solution. It is shown that complex Sm-2h is a multi-responsive fluorimetric sensor with high selectivity for F− and PO43− anions together with Zn2+ cation. The sensing process is rapid within 60 s for F− and PO43− ions and 300 s for Zn2+ ion. Further detailed responsive investigations suggest that its sensing behavior has excellent linear relationship between the fluorescence intensity (or absorption value) and ion concentration. The limit of detection (LOD) for sensing F−, PO43− and Zn2+ ions are as low as 2.61 μM (2.94 μM), 1.92 μM (1.64 μM) and 5.67 μM (3.53 μM), respectively, verified by fluorimetric (or colorimetric) titration experiments. ESI mass spectra prove that these efficient detections originate from the structure collapse of sensor Sm-2h because of the ion-induced imine bond breakage. Moreover, sensor Sm-2h shows excellent sensing performances for F−, PO43− and Zn2+ ions in real water samples, and we also have developed a convenient method to detect these three ions by use of the sensor impregnated test paper strips, providing rapid and distinguishable fluorimetric color changes. Therefore, the macrocyclic Sm(III) complex Sm-2h could be regarded as a valuable candidate for monitoring F−, PO43− and Zn2+ ions in practical applications. [Display omitted] •Luminescent macrocyclic Sm(III) complex Sm-2h was prepared by the template method.•Sm-2h was a multi-responsive fluorescent sensor for F−, PO43− and Zn2+ ions.•Efficient responses originated from the ion-induced imine bond breakage in Sm-2h.•Test strips offered a convenient way to detect three ions, even in water samples.