1-D Chain Tungstotellurate Hybrids Constructed from Organic-Ligand-Connecting Iron-Lanthanide Heterometal Encapsulated Tetrameric Polyoxotungstate Units

Two Types of Subgroup-Valence Heteroatoms (PIII, TeIV) Synergistically Controlling Octa-CeIII-Encapsulated Heteropolyoxotungstate and Its Electrochemical Recognition Properties

Rapid development of the synthetic chemistry of polyoxometalates (POMs) has greatly driven the generation of structurally variable innovative POM-based materials. Herein, we synthesized a novel P^III and Te^IV synergistically controlling octa-Ce^III-encapsulated heteropolyoxotungstate [H₂N(CH₃)₂]₁₁K₂Na₆H₁₁[Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂(B-β-TeW₈O₃₀)₂(B-α-TeW₈O₃₁)₄]·64H₂O (1). Its distinctive anion skeleton [Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂(B-β-TeW₈O₃₀)₂(B-α-TeW₈O₃₁)₄]^30- is built by two tetra-vacancy [B-β-TeW₈O₃₀]^8- and four tetra-vacancy [B-α-TeW₈O₃₁]^10- moieties linked through an inorganic-organic hybrid [Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂]²⁶⁺ {Ce₈P₂W₈} cluster core. Interestingly, {Ce₈P₂W₈} is assembled from four [W₂O₁₁]^10- groups and two [HP^IIIO₃]^2- anions and eight Ce³⁺ ions. Besides, 1 was further composited with carboxylated multiwalled carbon nanotube (CMCN), resulting in a bi-component 1/CMCN nanocomposite. An electrochemical recognition platform (named as 1/CMCN/GCE) was built by modifying 1/CMCN on a glassy carbon electrode (GCE) for electrochemical detection of dopamine (DPA) at physiological pH (pH = 7.0). The findings have shown that 1/CMCN/GCE exhibits a good detection limit of 4.95 nM for DPA. This work provides considerable inspiration to promote innovative and rational structure designs of POM-based materials and expand their applications to electrochemical and biological detection fields.

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

Two particular fumaric acid bridging lanthanide-encapsulated selenotungstates [H₂N(CH₃)₂]₁₆Na₈[Ln₃(H₂O)₇]₂ [W₄O₈(C₄H₂O₄) (C₄H₃O₄)]₂[SeW₆O₂₅]₂[B-α-SeW₉O₃₃]₄·46H₂O [Ln = Ce³⁺ (1), La³⁺ (2)] were acquired by the deliberately designed step-by-step synthetic strategy, which are composed of four trilacunary Keggin [B-α-SeW₉O₃₃]^8- and two original [SeW₆O₂₅]^10- building units together with one fumaric acid bridging heterometallic [Ln₃(H₂O)₇]₂[W₄O₈(C₄H₂O₄) (C₄H₃O₄)]₂²⁸⁺ entity. Particularly, this heterometallic cluster contains four fumaric acid ligands, which play two different roles: one works as the pendant decorating the cluster and the other acts as the linker connecting the whole structure. In addition, the 1@DDA hybrid material was produced through the cation exchange of 1 and dimethyl distearylammonium chloride (DDA·Cl) and its beehive-shaped film of 1@DDA was prepared by the breath figure method, which can be further used to establish an electrochemical biosensor for detecting a kind of mycotoxin-ochratoxin A (OX-A). The 1@DDA beehive-shaped film-based electrochemical biosensor exhibits good reproducibility and specific sensing toward OX-A with a low detection limit of 29.26 pM. These results highlight the huge feasibility of long-chain flexible ligands in building lanthanide-encapsulated selenotungstates with structural complexity and further demonstrate great electrochemical application potentiality of polyoxometalate-involved materials in bioanalysis, tumor diagnosis, and iatrology.

Roles of Organic Fragments in Redirecting Crystal/Molecular Structures of Inorganic-Organic Hybrids Based on Lacunary Keggin-Type Polyoxometalates

Lacunary polyoxometalates (LPOMs) are key precursors for the synthesis of functional POMs. To date, reviews dedicated to behavioral studies of LPOMs often comprise the role of metal ions, including transition metal (TM) and rare earth (RE) ions, in extending and stability of high-nuclearity clusters. In contrast, the role of organic ligands in the structures and properties of lacunary-based hybrids has remained less explored. In this review, we focus on the role of organic fragments in the self-assembling process of POM-based architectures and discuss relationships between the nature and structure of organic ligand and properties such as the topology of hybrid inorganic–organic material in RE and TM-RE heterometallic derivatives of lacunary Keggin-type POMs. The effects of organic fragment in mixed ligand hybrids are also briefly reviewed.

Hexameric to Trimeric Lanthanide-Included Selenotungstates and Their 2D Honeycomb Organic-Inorganic Hybrid Films Used for Detecting Ochratoxin A

Two types of organic-inorganic hybrid structure-related lanthanide (Ln)-included selenotungstates (Ln-SeTs) [H₂N(CH₃)₂]₁₁Na₇[Ce₄(H₂PTCA)₂(H₂O)₁₂(HICA)]₂[SeW₄O₁₇]₂[W₂O₅]₄[SeW₉O₃₃]₄·64H₂O (1, H₃PTCA = 1,2,3-propanetricarboxylic acid, H₂ICA = itaconic acid) and [H₂N(CH₃)₂]₆Na₄[Ln₄SeW₈(H₂O)₁₄(H₂PTCA)₂O₂₈] [SeW₉O₃₃]₂·31H₂O [Ln = Pr³⁺ (2), Nd³⁺ (3)] were obtained by Ln nature control. The primary frameworks of 1-3 are composed of trivacant Keggin-type [B-α-SeW₉O₃₃]^8- and [SeW₄O_m]^n- [Ln = Ce³⁺ (1), m = 17, n = 6; Ln = Pr³⁺ (2), Nd³⁺ (3), m = 18, n = 8] fragments bridged by organic ligands and Ln clusters. Intriguingly, Ln nature results in the degradation of hexameric 1 to trimeric 2-3. Besides, 1@DMDSA and 3@DMDSA composites (DMDSA·Cl = dimethyl distearylammonium chloride) were prepared through the cation exchange method, which were then reorganized to form two-dimensional (2D) honeycomb thin films by the breath figure method. Using these honeycomb thin films as electrode materials, the aptasensors were further established by utilizing methylene blue as an indicator and cDNA and Au nanoparticles as signal amplifiers to enhance the response signal so as to realize the purpose of ochratoxin A (OTA) detection. This work provides a new platform for detecting OTA and explores the application potential of POM-based composites in biological and clinical analyses.

Assembly of Lanthanide-Containing Tungstotellurates(VI): Syntheses, Structures, and Catalytic Properties

Lanthanide (Ln)-containing polyoxometalates (POMs) have attracted particular attention owing to their structural diversity and potential applications in luminescence, magnetism, and catalysis. Herein three types of Ln-containing tungstotellurates(VI) (Ln = Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, and Lu³⁺), dimeric (DMAH)_n[H_22−n{Ln(H₂O)₃[TeW₁₇O₆₁]}₂]^·mH₂O (abbreviated as {Ln₂Te₂W₃₄}; DMAH⁺ = dimethylammonium), mono-substituted (DMAH)₇Na₂{H₂Ln(H₂O)₄[TeW₁₇O₆₁]}^·mH₂O (abbreviated as {LnTeW₁₇}), and three-dimensional (3D) inorganic frameworks (DMAH)_n{H_3−nLn(H₂O)₄[TeW₆O₂₄]}^·mH₂O (abbreviated as {LnTeW₆}), have been synthesized by using simple metal salts and characterized by single-crystal X-ray diffraction and other routine techniques. Interestingly, the assembly of these POMs is pH dependent. Using the same starting materials, {Ln₂Te₂W₃₄} were obtained at pH 1.7, where two Dawson-like monovacant [TeW₁₇O₆₁]¹⁴⁻ are linked by two Ln³⁺ ions; mono-substituted Dawson-like {LnTeW₁₇} were isolated at pH 1.9, and 3D inorganic framework {LnTeW₆} based on Anderson-type [TeW₆O₂₄]⁶⁻ were formed at pH 2.3. It was also found that the assembly of Ln-containing POMs depends on the type of Ln³⁺ ions. The three types of POMs can be prepared by using Ln³⁺ ions with a relatively smaller ionic radius, such as Tb³⁺-Lu³⁺, while the use of Ln³⁺ ions (La³⁺-Eu³⁺) results in the formation of precipitation or {TeW₁₈O₆₂} clusters. Furthermore, three {LnTeW₆} (Ln = Tb³⁺, Er³⁺, Lu³⁺) were used as Lewis acid catalysts for the cyanosilylation of benzaldehydes, and their catalytic activity decreases with the decrease of Ln³⁺ ionic radius, giving the order: {TbTeW₆} > {ErTeW₆} > {LuTeW₆}. Notably, {TbTeW₆} is stable to leaching and can be reused for five cycles without a significant loss of its activity.

An unprecedented polyhydroxycarboxylic acid ligand bridged multi-EuIII incorporated tellurotungstate and its luminescence properties

The first polyhydroxycarboxylic acid ligand bridged multi-EuIII-incorporated tellurotungstate K14H10[Eu4(H2O)4W6(H2glu)4O12(B-α-TeW9O33)4]·60H2O (H6glu = d-gluconic acid) (1) was synthesized via an organic ligand-driven self-assembly strategy. The polyhydroxycarboxylic acid ligand bridged tetrameric polyoxoanion [Eu4(H2O)4W6(H2glu)4O12(B-α-TeW9O33)4]24- in 1 can be viewed as an aggregation of four trivacant Keggin [B-α-TeW9O33]8- fragments and an innovative heterometallic [Eu4(H2O)4W6(H2glu)4O12]8+ cluster, in which four high-coordinate polyhydroxy flexible H2glu4- ligands chelate W and Eu centers through carboxyl and hydroxyl groups, giving rise to a heterometallic cluster. The hexagonal packing of the tetrameric polyoxoanions in 1 along the c axis provides excellent porous channels, which greatly increases the specific surface area of the whole framework and may be of benefit for fluorescence sensing in aqueous solution. 1 can function as a "turn-off" luminescence sensor to detect Cu2+ ions in aqueous solution. The limit of detection (LOD) of the 1-sensor is 8.82 × 10-6 mM, which is the lowest among the reported polyoxometalate-based fluorescence sensors. As for the Cu2+-quenching system, it can function as an "off-on" sensor to detect cysteine in an aqueous system, affording a LOD of 1.75 × 10-4 mM. This work opens up an avenue to broaden the applications of polyoxometalate-based materials in the optical intelligence detection field.

2D chain layer versus 1D chain: rigid aromatic benzoate disassembling flexible alicyclic dicarboxylate-based lanthanide coordination polymers with enhanced photoluminescence and characteristic single-molecule magnet behavior

Used as photosensitizer and structural separator, aromatic benzoate activator was grafted on cyclopropane dicarboxylate-based lanthanide coordination polymers with efficient photoluminescence and characteristic behavior of single molecule magnet.

A novel cadmium metal–organic framework-based multiresponsive fluorescent sensor demonstrating outstanding sensitivities and selectivities for detecting NB, Fe3+ ions and Cr2O72− anions

A Cd(ii) metal–organic framework (MOF) [Cd₃(L)(NTB)₂(DMA)₂]·2DMA was solvothermal prepared in the presence of ligand L (L = (E)-4,4′-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide]) and ligand H₃NTB (H₃NTB = 4,4′,4′′-nitrilotribenzoic acid).