Multinuclear Antimony–Bismuth–Lanthanide Cluster-Connected Polyoxometalate for the Detection of 5-Hydroxyindoleacetic Acid via Luminescence

The judicious selection and combination of multicomponents provide great potential for the further exploration of new polyoxometalate (POM) materials. Here, a delicate control on tungstate, Sb^III and Bi^III sources, Eu³⁺ ions, and organic molecules led to the discovery of a novel multimetal cluster-embedded POM [H₂N(CH₃)₂]₉Na₈H₅{[Eu₄(H₂O)₆Sb₄Bi₂W₂O₁₂](SbW₉O₃₃)₂(SbW₈O₃₁)₂}·78H₂O (1). The polyoxoanion of 1 was constructed from four in situ-formed [SbW₈O₃₁]^11- and [SbW₉O₃₃]^9- building blocks connected by two hexa-metallic [Eu₂(H₂O)₃Sb₂BiWO₆]⁹⁺ clusters, to be a rare member of Sb- and Bi-coexisting POM. The most impressive characteristic of 1 is the intricate [Eu₂(H₂O)₃Sb₂BiWO₆]⁹⁺ cluster linker, which contains a Sb^III-Bi^III coinserted [Sb₂BiWO₆]³⁺ core grasping one [Eu1(H₂O)₂]³⁺ cation and one [Eu2(H₂O)]³⁺ cation on both sides through Sb-O-Eu and Bi-O-Eu bonds. Functionalized by luminescence centers of Eu³⁺ ions, 1 can emit intense emission in water and be capable of detecting the biomarker of carcinoids, 5-hydroxyindoleacetic acid (5-HIAA) with a low limit of detection of 0.43 μM, high selectivity, and excellent anti-interference, as well as fast response (12 s). The high detectability of 1 for 5-HIAA is relevant to the underlying dynamic quenching and energy-transfer mechanism. In urine conditions, remarkable recognition of 1 for 5-HIAA and satisfactory recoveries were achieved, indicative of the possibility of 1 in detecting 5-HIAA in a real environment. This work reveals the special clustering effect of Sb^III and Bi^III atoms in the assembly of neoteric POM species and also promotes the application of POMs as potential diagnostic tool in the early detection of carcinoids.