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, SbIII and BiIII 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 SbIII–BiIII 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 SbIII and BiIII 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.