An Unusual Bismuth–Antimony–Europium Cluster-Imbedded Polyoxotungstate and Its Bidirectional Luminescence Detection

An unprecedented aggregate formed by two bismuth–antimony–europium cluster-imbedded tungsten-oxo clusters and one Krebs-type polyoxotungstate linker [H2N­(CH3)2]14Na30H6[W4O10]­[B-β-BiW9O33]2{[Bi5.35Sb0.65Eu3O9(H2O)9]­[B-α-SbW9O33]3}2·124H2O (1) was prepared. The polyoxoanion skeleton of 1 contains a Krebs-type polyoxotungstate [W4O10]­[B-β-BiW9O33]2}14– ({Bi2W22}) (1a) as a linker that offers six active coordinate O atoms (two μ3-O and four μ2-O atoms) to grasp two Bi–Sb–Eu cluster-imbedded tungsten-oxo clusters {[Bi5.35Sb0.65Eu3O9(H2O)9]­[B-α-SbW9O33]3}18– (1b) through Bi–O–W and Sb–O–W bonds. 1b comprises an unprecedented nona-nuclearity Bi–Sb–Eu [Bi5.35Sb0.65Eu3O9(H2O)9]9+ cluster encircled by three trivacant [B-α-SbW9O33]9–segments in a triangular motif through Eu–O–W, Sb–O–W, and Bi–O–W linkages into a trilobal trimer. Moreover, a bidirectional detection method by using 1 as an effective luminescence probe was proposed to recognize both Mn2+ and CO3 2– through an “on–off–on” mode. 1 can be used as an “on–off” luminescent sensor to detect Mn2+ ions in aqueous solution. The limit of detection was 0.05 μM (9 × 10–6 mg L–1), which is much lower than the World Health Organization (WHO) guideline for Mn2+ concentration in drinking water (0.05 mg L–1). Then the Mn2+-quenching system can be used as an “off–on” sensor to detect CO3 2– in water system. This work provides a new research idea for the application of rare-earth-imbedded polyoxotungstate-based materials in the field of optical smart detection.