A Penta‐Eu^III Sandwiched Dawson Selenotungstate and Its Unique Luminescence Properties

Abstract

A new penta‐EuIII sandwiched Dawson‐type selenotungstate (ST) [H2N(CH3)2]10H3{SeO4Eu5(H2O)8[Se2W14O52]2}·40H2O (1) was constructed by an in‐situ self‐assembly strategy. The unique architectural feature of 1 is that two [Se2W14O52]12– segments graft each other by five Eu3+ ions via oxygen linkers. Meanwhile, a disordered tetra‐coordinate SeIV ion locates on the central symmetric site of the structure. What's more, based on its benign fluorescence properties and excellent water solubility, 1 was prepared to be an efficient chemosensor for the selective detection of the Cu2+ ion in aqueous solution. The detection was found to be 1.24 × 10–3 mm. The fluorescence quenching mechanism of the Cu2+ ion towards the 1‐based sensor might be caused by the LMCT absorption of the Cu2+ ion hindering energy transfer from ST fragments to the Eu3+ ion in 1 in aqueous solution. More interestingly, the Cu2+‐quenched system could be recovered by addition of cysteine (cys) because the strong chelation between cys and Cu2+. The LOD value of detecting cys is 2.17 × 10–4 mm for the continuous “off‐on” chemosensor, which provides a promising prospect of polyoxometalate‐based materials for environmental monitoring and clinical medical testing.

Polyoxometalate Functionalized Sensors: A Review

“…Although the luminescent EuW 10 dominate in the Ln-POM based fluorescence optical sensors group, other luminescent Eu-POMs have been reported ( Table 8 ). Two systems, a penta-Eu III sandwiched Dawson-type selenotungstate ( Zhang et al, 2020a ) [H 2 N(CH 3 )2] 10 H 3 {SeO 4 Eu 5 (H 2 O) 8 [Se 2 W 14 O 52 ] 2 }·40H 2 O, represented in Table 8 as EuSe 3 W 14 , and a polyhydroxycarboxylic acid ligand bridged multi-Eu III -incorporating tellurotungstate ( Zhang et al, 2020b ) K 14 H 10 [Eu 4 (H 2 O) 4 W 6 (H 2 glu) 4 O 12 (B- α -TeW 9 O 33 ) 4 ]·60H 2 O (H 6 glu = D-gluconic acid), represented in Table 8 as EuTeW 9 , were reported as sensors to detect Cu 2+ ions in aqueous solution. Both systems exhibited high fluorescence signals and good selectivity for detecting Cu 2+ ions in an aqueous solution ( Zhang et al, 2020a ; Zhang et al, 2020b ).…”

“…Two systems, a penta-Eu III sandwiched Dawson-type selenotungstate ( Zhang et al, 2020a ) [H 2 N(CH 3 )2] 10 H 3 {SeO 4 Eu 5 (H 2 O) 8 [Se 2 W 14 O 52 ] 2 }·40H 2 O, represented in Table 8 as EuSe 3 W 14 , and a polyhydroxycarboxylic acid ligand bridged multi-Eu III -incorporating tellurotungstate ( Zhang et al, 2020b ) K 14 H 10 [Eu 4 (H 2 O) 4 W 6 (H 2 glu) 4 O 12 (B- α -TeW 9 O 33 ) 4 ]·60H 2 O (H 6 glu = D-gluconic acid), represented in Table 8 as EuTeW 9 , were reported as sensors to detect Cu 2+ ions in aqueous solution. Both systems exhibited high fluorescence signals and good selectivity for detecting Cu 2+ ions in an aqueous solution ( Zhang et al, 2020a ; Zhang et al, 2020b ). The Eu-tellurotungstate showed the best performance due to the hexagonal packing of the tetrameric polyoxoanions, providing excellent porous channels, which greatly increased the specific surface area of the whole framework and fluorescence sensing.…”

Two Innovative Fumaric Acid Bridging Lanthanide-Encapsulated Hexameric Selenotungstates Containing Mixed Building Units and Electrochemical Performance for Detecting Mycotoxin

“…Selenotungstates (SeTs), as a burgeoning and promising branch of HPOM family, have attracted researchers’ vast interest and developed rapidly in recent years. − On one hand, the lone pair electrons stereochemical effect of Se IV HOA in SeTs can effectively preclude from generating the closed HPOM building units (BUs) and result in the formation of open and lacunary HPOM BUs, which can be deemed as peculiar inorganic ligands to combine functional metal cations for fabricating extraordinary architectures. On the other hand, the trigonal pyramidal SeO 3 2– anion can apply the self-carrying structure-directing effect to construct abundant SeT BUs. , In 2010, Cronin and collaborators reported several SeTs involving diverse BUs such as high-vacant {SeW 3 }, {SeW 8 }, and tri-vacant Keggin-type {SeW 9 } BUs . Moreover, the structures can be expanded through increasing the proportion of SeO 3 2– because it can work as the linkage to connect adjacent BUs .…”

“…On the other hand, the trigonal pyramidal SeO 3 2− anion can apply the self-carrying structure-directing effect to construct abundant SeT BUs. 38,39 In 2010, Cronin and collaborators reported several SeTs involving diverse BUs such as highvacant {SeW 3 }, {SeW 8 }, and tri-vacant Keggin-type {SeW 9 } BUs. 11 Moreover, the structures can be expanded through increasing the proportion of SeO 3 2− because it can work as the linkage to connect adjacent BUs.…”