Ultrastable 1D Europium Complex for Simultaneous and Quantitative Sensing of Cr(III) and Cr(VI) Ions in Aqueous Solution with High Selectivity and Sensitivity.

A unique metal-organic complex (MOC) with formula [Eu2(tpbpc)4·CO3·4H2O]·DMF·solvent (Htpbpc = 4'-[4,2';6',4″]-terpyridin-4'-yl-biphenyl-4-carboxylic acid) has been successfully constructed under solvothermal conditions. The Eu complex, as proved by structural analysis, exhibits a fascinating 1D linear-type chain structure which is further extended to a 3D H-bonded supramolecular framework. The luminescent investigations confirm that the emission behavior of the Eu complex possesses excellent water stability and pH stability, and it is the first example of a MOC-based fluorescent probe with high selectivity, high sensitivity, and low detection limit, targeting Cr(III) and Cr(VI) (CrO42-/Cr2O72-) ions in aqueous solution. Importantly, the luminescence can be fast and simple, regenerated in detecting CrO42- and Cr2O72- ions. Furthermore, the simple fluorescent-based test paper was successfully prepared and provided a reliable and visual detection of Cr3+, CrO42-, and Cr2O72- ions in daily applications.