A Giant 3d-4f Polyoxometalate Super-Tetrahedron with High Proton Conductivity

Pyrazine Dicarboxylic Acid and Phosphite-Bridging Lanthanide-Incorporated Tellurotungstates and Their Fluorescence Performances

Two pyrazine dicarboxylic acid and phosphite-bridging lanthanide-incorporated tellurotungstates [H2N(CH3)2]12 Na4[Ln4(H2O)2(H2PDBA)2(HPO3)2W6O10][B-α-TeW8O31]4 · 70H2O [Ln = Eu3+ (1), Tb3+ (2); H2PDBA = 2,5-pyrazine dicarboxylic acid) were prepared, which contain four [B-α-TeW8O31]10- subunits and a deca-nuclear heterometallic [Ln(H2O)2(HPO3)2 (H2PDBA)2(W3O5)2]24+ cluster. Strikingly, two H2PDBA ligands connect two equivalent {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moieties to form the polyanion skeleton, while the phosphite plays a bridging role in joining two lanthanide centers in the {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moiety. In addition to the fluorescence (FL) properties of 1 and 2 at room temperature, their temperature-dependent FL properties were also investigated. In 80-298 K, FL intensities of 1 and 2 decrease as temperature increases, and their maximum relative sensitivities (Sr) are 3.70 and 1.99% K-1, whereas the minimum temperature uncertainties (δT) are 1.25 and 1.18 K for 1 and 2. In 298-973 K, upon increasing temperature, FL intensities of 1 and 2 initially rise to their maxima at 373 K and subsequently decrease. This is because samples of 1 and 2 undergo dehydration together with amorphization below 473 K and decomposition above this temperature. This work lays a foundation for the development for luminescent thermometers based on lanthanide-incorporated polyoxometalates.

Synthesis of {AlMo14O44}-Based Supramolecular Structures with High Proton Conductivity

Polyoxometalates (POMs) are esteemed for their remarkable stability and exceptionally high proton conductivity, rendering them ripe for extensive exploration owing to their research significance. Herein, we synthesized two bimolybdenum-capped {AlMoVI8MoV6O44} cluster-based coordination polymers through a solvothermal method. Single-crystal X-ray diffraction analysis elucidates that H[(H2bimb)3(AlMoVI8MoV6O44)] [bimb = 1,4-bis(imidazole-1-ylmethyl)benzene, compound 1] is the POMs-organic supramolecular structure. The introduction of zinc ions into the reaction environment facilitated the connection of initially dispersed ligands, which yielded the well-ordered structure H3[Zn2(bimb)4(AlMoVI8MoV6O44)]·4H2O (compound 2) with a layer distance of 11.8 Å. The proton conductivities (σ) of two compounds were measured under conditions of 85 °C and 98% relative humidity (RH), resulting in values of 3.89 × 10-2 and 4.76 × 10-2 S·cm-1, respectively. This study presents a novel approach to fabricating POMs as proton conductors through structural design and manufacturing adjustments.

Recent advances in atomic cluster synthesis: a perspective from chemical elements

Despite its potential significance, "cluster chemistry" remains a somewhat marginalized topic within the chemistry field. However, atomic clusters with their unusual and unique structures and properties represent a novel material group situated between molecules and nanoparticles or solid matter, judging from both scientific standpoints and historical backgrounds. Surveying an entire material group, including all substances that can be regarded as a cluster, is essential for establishing cluster chemistry as a more prominent chemistry field. This review aims to provide a comprehensive understanding by categorizing, summarizing, and reviewing clusters, focusing on their constituent elements in the periodic table. However, because numerous disparate synthetic processes have been individually developed to date, their straightforward and uniform classification is a challenging task. As such, comprehensively reviewing this field from a chemical composition viewpoint presents significant obstacles. It should be therefore noted that despite adopting a synthetic method-based classification in this review, the discussions presented herein could entail inaccuracies. Nevertheless, this unorthodox viewpoint unfolds a new scientific perspective which accentuates the common ground between different development processes by emphasizing the lack of a definitive border between their synthetic methods and material groups, thus opening new avenues for cementing cluster chemistry as an attractive chemistry field.

{SeO2(OH)} Bridging Lanthanide-Containing Antimono-Seleno-Tungstates

A series of new trigonal pyramidal {SeO2(OH)} bridging lanthanide-containing antimono-seleno-tungstates [H2N(CH3)2]8Na8Cs4H9[Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]2·32H2O [Ln = Tb (1), Dy (2), Ho (3), Er (4)] have been prepared by the synthetic strategy of simultaneously using the antimonotungstate precursor and simple material in an acidic aqueous solution and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectrometry, and thermogravimetric analysis. Their molecular structures contain an unprecedented hexameric polyoxoanion [Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]229- constituted by two equivalent trimeric subunits Ln2W4O9(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33) bridged via two μ2-{SeO2(OH)} linkers. Furthermore, the catalytic oxidation of various aromatic sulfides and sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) by compound 3 as the heterogeneous catalyst has been investigated, exhibiting high conversion and selectivity as well as good stability and recyclability.

An Organodiphosphate-Containing Polyoxoniobate Ring and Its Assembly into a Three-Dimensional Framework through Hydrogen Bonding

In this work, a novel organodiphosphate-containing inorganic-organic hybrid polyoxoniobate (PONb) ring {(PO3CH2CH2PO3H)4Nb8O16}4- (Nb8P8) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb8O36} motif and four {PO3CH2CH2PO3H} ligands. Interestingly, Nb8P8 can be joined together via K-H2O clusters {K2(H2O)4(OH)2} to form one-dimensional chains {[K2(H2O)4(OH)2]Nb8P8}n and further linked by {Cu(en)2}2+ (en = ethylenediamine) complexes, resulting in a three-dimensional supramolecular framework {[Cu(en)2]2[K2(H2O)4(OH)2]Nb8P8}·3en·H2O (1). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm3 g-1 (22.71 mol·mol-1) at 298 K, outperforming most of the known polyoxometalate-based materials. Impedance measurements prove that 1 can transfer protons with moderate conductivity. This study not only contributes to the structural diversity of organodiphosphate-containing PONbs and PONb rings but also provides a reference for the development of PONb-based materials with unique performance.

A Giant Heterometallic Polyoxometalate Nanocluster for Enhanced Brain-Targeted Glioma Therapy

Giant heterometallic polyoxometalate (POM) clusters with precise atom structures, flexibly adjustable and abundant active sites are promising for constructing functional nanodrugs. However, current POM drugs are almost vacant in orthotopic brain tumor therapy due to the inability to effectively penetrate the blood-brain barrier (BBB) and low drug activity. Here, we designed the largest (3.0 nm × 6.0 nm) transition-metal-lanthanide co-encapsulated POM cluster {[Ce10 Ag6 (DMEA)(H2 O)27 W22 O70 ][B-α-TeW9 O33 ]9 }2 88- featuring 238 metal centers via synergistic coordination between two geometry-unrestricted Ce3+ and Ag+ linkers with tungsten-oxo cluster fragments. This POM was combined with brain-targeted peptide to prepare a brain-targeted nanodrug that could efficiently traverse BBB and target glioma cells. The Ag+ active centers in the nanodrug specifically activate reactive oxygen species to regulate the apoptosis pathway of glioma cells with a low half-maximal inhibitory concentration (5.66 μM). As the first brain-targeted POM drug, it efficiently prolongs the survival of orthotopic glioma-bearing mice.

Controlled Assembly of a Dawson-like Antimoniotungstate-Supported Trefoil-type Trimer with Good Proton Conductivity Performance

With the excellent properties of POM in the field of proton conductivity, the preparation of POM-based proton-conductive materials has burst into life. Herein, an unprecedented Sb-templated all-inorganic trimer Na8H18.64[(SbW14O52)3(Sb2W6.12Ru5.88O18)]·85H2O (1), which is based on tetravacant Dawson-like [SbW14O52]17- blocks and exhibits a trefoil type with D3 symmetry, has been successfully designed and synthesized by the assembly of simple materials with a one-pot hydrothermal method under acidic conditions. Also, compound 1 is systematically characterized by single-crystal X-ray diffraction, PXRD, ESI-MS, IR spectroscopy, UV-vis, elemental analysis, and TGA. Crystal structure data analysis demonstrates that compound 1 is constructed by a hexagonal prismatic heterometallic {Sb2W6.12Ru5.88O18} core and three equivalent {SbW14} units bridged through μ2-O atoms in periphery. Subsequently, further property experiments show that compound 1 exhibits high proton conductivity with a conductivity value (σ) of 3.07 × 10-2 S cm-1 at 75 °C and 80% relative humidity (RH). The activation energy of compound 1 evaluated by the Arrhenius plots is 0.22 eV, which indicates that the Grotthuss mechanism is dominant during the process of proton transfer.

Synthesis and Properties of Cobalt/Nickel-Iron-Antimony(III, V)-Oxo Tartrate Cluster-Based Compounds

Two types of isostructural iron-cobalt/nickel-antimony-oxo tartrate cluster-based compounds, namely (H3O)(Me2NH2)[M(H2O)6]2[FeII2SbIII12(μ4-O)3(μ3-O)8(tta)6]·6H2O (M = Co (1); Ni (3)), H5/3[Co2.5FeII4/3FeIII3(H2O)13SbV1/3FeIII2/3(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (2) and H2[Ni2.25FeII1.5FeIII3(H2O)14SbV0.25FeIII0.75(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (4) (H4tta = tartaric acid) were synthesized via simple solvothermal reactions. All the clusters in the structures adopt sandwich configurations, that is, bilayer sandwich configuration in 1 and 3 and monolayer sandwich configuration in 2 and 4. Interestingly, the monolayer sandwiched compounds 2 and 4 represent rare examples of cluster-based compounds containing mixed-valence Sb(III, V), whose center of the intermediate layer is the co-occupied [FexSbV1-x]. This is different from that of previously reported sandwich-type antimony-oxo clusters in which the center position is either occupied by a transition metal ion or a Sb(V) alone. Thus, the discovery of title compounds 2 and 4 makes the evolution of center metal ion more complete, that is, from M, MxSbV1-x to SbV. All the title compounds were fully characterized, and the photocatalysis, proton conduction and magnetism of compounds 2 and 4 were studied.

Mixed-valence compounds based on heterometallic-oxo-clusters containing Sb(III,V): crystal structures and proton conduction

Two isostructural Co(Cd)-antimony-oxo tartrate cluster-based compounds with a one-dimensional (1-D) belt-like structure, namely H9.2[Co(H2O)6]{M0.5(H2O)3.5{M'(H2O)4[SbVO6[Co4.2(H2O)5SbIII6(μ3-O)2(tta)6]]}}2·nH2O (M = Co, M' = Co, n = 9 (1); M = Cd0.39/Co0.61, M' = Cd0.24/Co0.76, n = 7 (2); H4tta = tartaric acid), have been synthesized by solvothermal methods. It is noteworthy that the relatively rare mixed-valence Sb(III,V) exists in the structures. The anionic clusters in both compounds appear to be in a sandwich configuration; the top and bottom layers are based on {Sb3(μ3-O)(tta)3} brackets, and the intermediate layer is occupied by {SbVO6[Co4.2(H2O)5]}. The title compounds have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, thermogravimetric analyses, and UV-Vis spectroscopy. We chose compound 2 as a representative to test its proton conductivity, and the results show that the conductivity can reach 1.42 × 10-3 S cm-1 at 85 °C under 98% relative humidity.

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 CO32- 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 CO32- 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.

A Macrocyclic Polyoxomolybdate with Phosphate and Phosphonate Linkers: Synthesis, Structure, and Proton Conductivity

A coordination macrocycle composed of eight identical [PMo8O27]- ({PMo8}) clusters connected by both organic tetraphosphonates and inorganic phosphates, (C3N2H5)29(NH4)6H12[(PMo8O27)8(C10P4O12N2H20)4(PO4)4Cs(Mo4O10(H2O)4)] (C3N2H5+ = imidazolium), is presented here. The primary building block, {PMo8}, is a tetravacant Keggin-type phosphomolybdate that has never been observed before. The compound shows a high proton conductivity of 9.70 × 10-3 S cm-1 at 373 K and 98% relative humidity. Control experiments on an imidazolium-free sample demonstrate the critical role of the imidazolium counterions as mobile proton carriers. The contribution of imidazolium necessitates a high activation energy (Ea = 0.502 eV) for proton conduction via the vehicle mechanism.

Cerium-Encapsulated SbIII-SeIV-Templating Polyoxotungstate for Electrochemically Sensing Human Multidrug Resistance Gene Segment

A tower-like SbIII-SeIV-templating polyoxotungstate [H2N(CH3)2]12Na7H3[Ce0.5/Na0.5(H2O)5]2[SbSe2W21O75]2·50H2O (1) was synthesized, whose skeleton is assembled from two prolonged lacunary Dawson [SbSe2W21O75]13- units and two [Ce0.5/Na0.5(H2O)5]2+ linkers. The uncommon [SbSe2W21O75]13- unit can be viewed as a combination of one [SeW6O21]2- group grafted onto a trivacant Dawson [SbSeW15O54]11- subunit. The conductive composite 1-Au@rGO containing 1, gold nanoparticles, and reduced graphene oxide (rGO) was conveniently prepared, using which the 1-Au@rGO-based electrochemical genosensor was constructed for detecting human multidrug resistance gene segment. This work enriches structural types of dual-heteroatom-inserted polyoxometalates and promotes the application of polyoxometalates in genosensors.

Single-Crystal Superstructures via Hierarchical Assemblies of Giant Rubik's Cubes as Tertiary Building Units

Intricate superstructures possess unusual structural features and promising applications. The preparation of superstructures with single-crystalline nature are conducive to understanding the structure-property relationship, however, remains an intriguing challenge. Herein we put forward a new hierarchical assembly strategy towards rational and precise construction of intricate single-crystal superstructures. Firstly, two unprecedented superclusters in Rubik's cube's form with a size of ≈2×2×2 nm³ are constructed by aggregation of eight {Pr₄ Sb₁₂ } oxohalide clusters as secondary building units (SBUs). Then, the Rubik's cubes further act as isolable tertiary building units (TBUs) to assemble diversified single-crystal superstructures. Importantly, intermediate assembly states are captured, which helps illustrate the evolution of TBU-based superstructures and thus provides a profound understanding of the assembly process of superstructures at the atomic level.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

Space-Confined Nucleation of Semimetal-Oxo Clusters within a [H7P8W48O184]33- Macrocycle: Synthesis, Structure, and Enhanced Proton Conductivity

Spatially confined assembly of semimetallic oxyanions (AsO₃^3- and SbO₃^3-) within a [H₇P₈W₄₈O₁₈₄]^33- (P₈W₄₈) macrocycle has afforded three nanoscale polyanions, [{As^III₅O₄(OH)₃}₂(P₈W₄₈O₁₈₄)]^32- (As₁₀), [(Sb^IIIOH)₄(P₈W₄₈O₁₈₄)]^32- (Sb₄), and [(Sb^IIIOH)₈(P₈W₄₈O₁₈₄)]^24- (Sb₈), which were crystallized as the hydrated mixed-cation salts (Me₂NH₂)₁₃K₇Na₂Li₁₀[{As^III₅O₄(OH)₃}₂(P₈W₄₈O₁₈₄)]·32H₂O (DMA-KNaLi-As₁₀), K₂₀Li₁₂[(Sb^IIIOH)₄(P₈W₄₈O₁₈₄)]·52H₂O (KLi-Sb₄), and (Me₂NH₂)₈K₆Na₅Li₅[(Sb^IIIOH)₈(P₈W₄₈O₁₈₄)]·65H₂O (DMA-KNaLi-Sb₈), respectively. A multitude of solid- and solution-state physicochemical techniques were employed to systematically characterize the structure and composition of the as-made compounds. The polyanion of As₁₀ represents the first example of a semimetal-oxo cluster-substituted P₈W₄₈ and accommodates the largest As^III-oxo cluster in polyoxometalates (POMs) reported to date. The number of incorporated SbO₃^3- groups in Sb₄ and Sb₈ could be customized by a simple variation of Sb^III-containing precursors. Encapsulation of semimetallic oxyanions inside P₈W₄₈ sets out a valid strategy not only for the development of host-guest assemblies in POM chemistry but also for their function expansion in emerging applications such as proton-conducting materials, for which DMA-KNaLi-As₁₀ showcases an outstanding conductivity of 1.2 × 10^-2 S cm^-1 at 85 °C and 70% RH.

Keeping Superprotonic Conductivity over a Wide Temperature Region via Sulfate Hopping Sites-Decorated Zirconium-Oxo Clusters

Metal-oxo clusters have emerged as advanced proton conductors with well-defined and tunable structures. Nevertheless, the exploitation of metal-oxo clusters with high and stable proton conductivity over a relatively wide temperature range still remains a great challenge. Herein, three sulfate groups decorated zirconium-oxo clusters (Zr₆ , Zr₁₈ , and Zr₇₀ ) as proton conductors are reported, which exhibit ultrahigh bulk proton conductivities of 1.71 × 10^-1 , 2.01 × 10^-2 , and 3.73 × 10^-2  S cm^-1 under 70 °C and 98% relative humidity (RH), respectively. Remarkably, Zr₆ and Zr₇₀ with multiple sulfate groups as proton hopping sites show ultralow activation energies of 0.22 and 0.18 eV, respectively, and stable bulk conductivities of >10^-2  S cm^-1 between 30 and 70 °C at 98% RH. Moreover, a time-dependent proton conductivity test reveals that the best performing Zr₆ can maintain high proton conductivity up to 15 h with negligible loss at 70 °C and 98% RH, representing one of the best crystalline cluster-based proton conducting materials.

Ni12 tetracubane cores with slow relaxation of magnetization and efficient charge utilization for photocatalytic hydrogen evolution

We report two Ni₁₂ multicubane topologies enclosed in the polyanions [Ni₁₂(OH)₉(WO₄)₃(PO₄)(B-α-PW₉O₃₄)₃]^21-{Ni₁₂W₃₀} and [Ni₁₂(OH)₉(HPO₄)₃(PO₄)(B-α-PW₉O₃₄)(A-α-PW₉O₃₄)₂]^21-{Ni₁₂W₂₇} that magnetically behave as Ni₁₂ units clearly distinguishing them from typical Ni₄ cubanes as shown by magnetic studies together with high field and frequency electron paramagnetic resonance (HFEPR). Beyond the unprecedented static properties, {Ni₁₂W₃₀} shows the unusual coexistence of slow relaxation of the magnetization and a diamagnetic ground state (S = 0), providing the unique opportunity of studying the essentially elusive magnetic relaxation behavior in excited states. The cubane-topology dependent activity of {Ni₁₂W₃₀} and {Ni₁₂W₂₇} as homogeneous HER photocatalysts unveils the structural key features significant for the design of photocatalysts with efficient charge utilization exemplified by high quantum yields (QY) of 10.42% and 8.36% for {Ni₁₂W₃₀} and {Ni₁₂W₂₇}, respectively.

Lamellar Nanocomposite Based on a 1D Crayfish-like CeIII-Substituted Phospho(III)tungstate Semiconductor and Polyaniline Used as a High-Performance Humidity Sensing Device

In order to meet people's demand for intelligent management of daily life and health, manufacturing and developing humidity monitoring equipment with convenience, high sensitivity, easy miniaturization, and low cost is particularly important in the era of rapid development of artificial intelligence and the Internet of Things. Polyaniline (PANI) is an attractive humidity sensing material due to its designable functional properties. However, PANI modified polyoxometalates (POMs) for humidity sensing are still rare. As a proof of concept, a novel moisture sensing composite material was obtained based on PANI and a novel 1D rare-earth-substituted phospho(III)tungstate [H₂N(CH₃)₂]₉Na₃H₆[Ce₂(H₂O)₃W₅O₁₃(C₂O₄)][HP^IIIW₉O₃₃]₂[(HP^III)₂W₁₅O₅₄]·42H₂O (1). Notably, the anion structure of 1 contains trivacant Keggin-type [B-α-HP^IIIW₉O₃₃]^8- and Dawson-like [(HP^III)₂W₁₅O₅₄]^10- subunits linked by a heterometallic [Ce₂(H₂O)₃W₅O₃₂(C₂O₄)]^30- cluster. Furthermore, the 1/PANI composite shows a typical semiconductive characteristic with a "band-like" conductive mechanism. The fabricated 1/PANI-based humidity sensing device exhibits a broad sensing range (11∼97% relative humidity), fast response/recovery time (3.45 s/3.24 s), good repeatability, and long-term stability (over 3 months). Additionally, the possible sensing mechanism is proposed. This work offers an enormous possibility for the design of high-performance humidity sensing materials through POM material chemistry.

Organophosphonic Acid-Regulating Assembly of PV-SbIII Polyoxotungstate and Its Potential in Building a Dual-Signal Readout Electrochemical Aptasensor for Carcinogen Detection

Template-directed assembly of giant cluster-based nanomaterials is an everlasting theme in cluster science. In this work, ethylenediamine tetramethylphosphonic acid [H₈EDTPA = (POCH₂(OH)₂)₄C₂H₄N₂] and [B-α-SbW₉O₃₃]^9- were, respectively, used as an organic template and an inorganic template to prepare an organophosphonic acid-regulating P^V-Sb^III-heteroatom-inserted polyoxotungstate aggregate [H₂N(CH₃)₂]₅Na₁₁H₉[CeW₄O₁₀(HEDTPA)SbW₁₅O₅₀][B-α-SbW₉O₃₃]₂·36H₂O (1). Noteworthily, organophosphonic acid ligand not only works as an organic template leading to the assembly of a [HEDTPASbW₁₅O₅₀]^14- building block but also further bridges the sandwich-type [CeW₄O₁₀(B-α-SbW₉O₃₃)₂]^11- entity. To extend its potential application in electrochemical sensing properties, we prepared a three-dimensional 1@EGO composite (EGO = reduced graphene oxide functionalized by ethylenediamine) with porous architecture and a prominent conducting ability. Furthermore, the 1@EGO composite was explored as a modification material for glassy carbon electrodes to build a dual-signal readout electrochemical aptasensor for carcinogens, which shows much better detection performance for aflatoxin B1 compared with traditional single-signal biosensors.

2D Windmill-like Ln-Containing Organophosphonate-Based Polyoxomolybdates: Synthesis, Characterization, Fluorescence, and Magnetism

By integration of {Ln(H₂O)₆}³⁺ into organophosphonate-based polyoxometalates, three Ln-containing organophosphonate-functionalized polyoxomolybdates Na_1.5H_1.5[{Ln(H₂O)₆}₂{(Mo₃O₈)(O₃PC(C₃H₆NH₃)OPO₃)}₄]·(CH₃CO₂)·43H₂O (Ln = Eu (1), Tb (2), and Dy (3)) are successfully prepared and systematically characterized. The X-ray crystallography analyses display complexes 1-3 crystallize in the C2/c space group of the monoclinic system and compose several distinctive tetramer windmill-like compounds that further assemble into two-dimensional (2D) frameworks associated with the {Ln(H₂O)₆}³⁺ core. The fluorescence spectra of 1-3 show red, green, and chartreuse emissions, respectively, originating in the typical f-f transitions of Ln³⁺ ions. More interestingly, complex 3 shows the field-induced single-molecule magnet (SMM) properties, resulting from the fact that [(Mo₃O₈)₄{O₃PC(C₃H₆NH₃)OPO₃}₄]^8- offers excellent magnetic isolation for Dy³⁺ ions by the nearest Dy1···Dy2 distance of 11.207 Å. The study demonstrates that the incorporation of {Ln(H₂O)₆}³⁺ into organophosphonate-based polyoxomolybdates is an effective synthetic strategy in implementing late-model opto-magnetic materials.

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.

High-Nuclear Ni-Substituted Poly(polyoxometalate) Containing an Anderson-like {Cs7} Cluster

A novel high-nuclear Ni-substituted poly(polyoxometalate) [poly(POM)], [H₂N(CH₃)₂]₂Na₁₈Cs₂H₁₃[(Cs₇(H₂O)₆)@{(PO₄)-@(Ni₄(OH)₃(WO₄))₃@(B-α-PW₉O₃₄)₃}₂]·30H₂O (1), has been successfully developed and structurally characterized. The polyoxoanion of 1 can be viewed as a unique huge sandwich structure made of an unprecedented Cs₇(H₂O)₆ ({Cs₇}) cluster core encapsulated by two trimeric [(PO₄)@(Ni₄(OH)₃(WO₄))₃@(B-α-PW₉O₃₄)₃]^21- subunits, in which the {Cs₇} cluster presents an interesting Anderson-like arrangement and is the first example of a classical POM configuration based on the alkali metal cluster in the POM chemistry. The polyoxoanion can also be described as an unusual [(Cs₇(H₂O)₆)@{(PO₄)@(Ni₄(OH)₃(WO₄))₃}₂]¹⁹⁺ cluster packaged by six {PW₉} fragments. Furthermore, investigations on the Knoevenagel condensation reaction reveal that 1 has good catalytic activity for the condensation of various aldehydes and malononitrile into corresponding products with excellent yields.

Trisubstituted 4f- and 4d tungstoantimonates as artificial phosphoesterases for nerve agent degradation

Three new trisubstituted 4f- and 4d tungstoantimonates (TA) K3Na21[(M(CH3COO))3(HPO3)(WO4)(SbW9O33)3]·nH2O {M3(HPO3)Sb3W28} (M = GdIII, YIII, YbIII, n = 35-36) were synthesized using a double-template synthetic approach. Following their characterization in the solid state employing single- and powder X-ray diffraction (XRD), IR-spectroscopy, and elemental - and thermogravimetric analyses (TGA), {M3(HPO3)Sb3W28} were subjected to a comprehensive set of solution characterization methods including UV/vis- and multinuclear 31P and 13C NMR spectroscopy. All representatives were shown to be highly active, recyclable, and stable Lewis-acid catalysts towards the nerve agent simulant O,O-dimethyl O-(4-nitrophenyl) phosphate (DMNP) at neutral pH (in Tris-HCl [125 mM] at pD 7.0 25 °C). Control experiments showing catalytic activity of the unsubstituted trilacunary TA [SbW9O33]9- suggest the non-innocence of Tris in the DMNP hydrolysis for the first time.

A Three-Dimensional (3D) Indium-Containing Polyoxoniobate Framework Based on {In5Nb71}n Helical Pillars

A rare 3D Indium-containing polyoxoniobate framework {H₉[Cu(en)₂(H₂O)₂][Cu(en)₂]₁₂[In(en)]₅[Nb₂₃-O₆₅(OH)₃(H₂O)₂]{Nb₂₄O₆₇(OH)₂(H₂O)₃]₂}·68H₂O(1), based on the In-containing polyoxoniobate cluster, {[In(en)]₅[Nb₂₃O₆₅(OH)₃(H₂O)₂][Nb₂₄O₆₇(OH)₂(H₂O)₃]₂}^35- ({In₅Nb₇₁}) and [Cu(en)₂]²⁺ linkers has been successfully synthesized. The nest-like cluster {In₅Nb₇₁} is constructed from one brand-new V-shaped {Nb₂₃O₇₀}, two triangle-shaped {Nb₂₄O₇₂} and five [In(en)]³⁺. The [In(en)] fragments link {Nb₂₄O₇₂} and {Nb₂₃O₇₀} units into unique {In₅Nb₇₁}_n helical pillars. The copper-amine complexes connect the {In₅Nb₇₁}_n helical pillars into a three-dimensional (3D) inorganic-organic hybrid In-Cu-containing framework. This material also exhibits good ionic conductivity and vapor adsorption capacity properties.

Ligand Induced Double-Chair Conformation Ln12 Nanoclusters Showing Multifunctional Magnetic and Proton Conductive Properties

Many methods have been utilized to adjust the size of superatomic metal nanoclusters, while tuning the geometric conformations of specific nanoclusters is rare. Here, we demonstrate that conformation variation can be realized by slightly modifying the ligand under maintaining the nuclei number of metal atoms. A series of novel "double-chair" conformation Ln₁₂ (Ln = Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)) clusters were generated by replacing 3-formylsalicylic acid with 2,3-dihydroxybenzoic acid in the Ln₁₂ nanocluster. Intriguingly, Dy₁₂ displays slow magnetic relaxation at low temperatures, while Gd₁₂ shows a large magnetocaloric effect (MCE) of 35.63 J kg^-1 K^-1 at 2 K for ΔH = 7 T. Additionally, the introduction of numerous coordination water molecules in these clusters enables Dy₁₂ and Gd₁₂ with high proton conductivity, namely, 2.13 × 10^-4 and 3.62 × 10^-4 S cm^-1 under 358 K and 95% RH humidity conditions.

Synergistic Experimental and Theoretical Studies of Luminescent-Magnetic Ln2Zn6 Clusters

The present work is part of our ongoing quest for developing functional inorganic complexes using unorthodox pyridyl-pyrazolyl-based ligands. Accordingly, we report herein the synthesis, characterization, and luminescence and magnetic properties of four 3d-4f mixed-metal complexes with a general core of Ln₂Zn₆ (Ln = Dy, Gd, Tb, and Eu). In stark contrast to the popular wisdom of using a compartmental ligand with separate islands of hard and soft coordinating sites for selective coordination, we have vindicated our approach of using a ligand with overcrowded N-coordinating sites that show equal efficiency with both 4f and 3d metals toward multinuclear cage-cluster formation. The encouraging red and green photolumiscent features of noncytotoxic Eu₂Zn₆ and Tb₂Zn₆ complexes along with their existence in nanoscale dimension have been exploited with live-cell confocal microscopy imaging of human breast adenocarcinoma (MCF7) cells. The magnetic features of the Dy₂Zn₆ complex confirm the single-molecule-magnet behavior with befitting frequency- and temperature-dependent out-of-phase signals along with an U_eff value of ∼5 K and a relaxation time of 8.52 × 10^-6 s. The Gd₂Zn₆ complex, on the other hand, shows cryogenic magnetic refrigeration with an entropy change of 11.25 J kg^-1 K^-1 at a magnetic field of 7 T and at 2 K. Another important aspect of this work reflects the excellent agreement between the experimental results and theoretical calculations. The theoretical studies carried out using the broken-symmetry density functional theory, ORCA suite of programs, and MOLCAS calculations using the complete-active-space self-consistent-field method show an excellent synergism with the experimentally measured magnetic and spectroscopic data.

Organic–inorganic hybrid phosphite-participating S-shaped penta-CeIII incorporated tellurotungstate as electrochemical enzymatic hydrogen peroxide for β-D-glucose detection

Polyoxometalate chemistry has made rapid advances in innovative structural chemistry. The lower valence state and lone electron pair effect of subgroup-valence heteroatom Te(IV) can be introduced into the tungsten-oxygen system...

Chiral Wheel Anions of Copper(II)-Early Lanthanides(III) with High Optical-Limiting Properties

A new family of chiral wheel anions {CuII22LnIII4} (La, Ce, Pr, Nd and Sm) was obtained from aqueous solution by the use of tartrate anions. It provides a new perspective...

Assembly of tetra-nuclear YbIII-containing selenotungstate clusters: synthesis, structures, and magnetic properties

Two tetra-nuclear Yb^III-incorporated selenotungstate clusters, Keggin (C₂H₈N)₆Na₁₄[Yb₄Se₆W₄₄O₁₆₀(H₂O)₁₂]·40H₂O (1) and Wells-Dawson (C₂H₈N)₄Na₁₄[Yb₄Se₆W₄₅O₁₅₉(OH)₆(H₂O)₁₁]·38H₂O (2), have been isolated through a pH-controlled assembly, which exhibit the first Yb^III-containing polyoxotungstates with selenium heteroatoms. Their assemblies rely on the structure-directing effects of SeO₃^2- anion templates to give rise to available Se-containing Keggin-/Wells-Dawson-type motifs. Both compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, power X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as electrospray ionization mass spectrometry (ESI-MS). Furthermore, systematic magnetic studies revealed that 1 exhibits field-induced single-molecule magnetic behavior with a pre-exponential factor of τ₀ = 6.60(7) × 10^-8 s and a relaxation energy barrier of ΔE/k_B = 39.44(2) K, while 2 only displays antiferromagnetic interactions between the ytterbium centers.

Organoamine-Directed Assembly of 5p-4f Heterometallic Cluster Substituted Polyoxometalates: Luminescence and Proton Conduction Properties

The assembly of heterometallic cluster substituted polyoxometalates (POMs) remains a great challenge for inorganic synthetic chemistry up to now. Herein, a series of 5p-4f heterometallic cluster substituted POMs were successfully isolated by a facile one-step hydrothermal reaction method, namely H₁₇(H₂en)₃[Sb^III₉Sb^VLn₃O₁₄(H₂O)₃][(SbW₉O₃₃)₃(PW₉O₃₄)]·28H₂O(1-Ln, Ln = Ce, Sm, Eu, Gd, Tb, Dy) (en = ethylenediamine). Interestingly, by replacing en with imidazole, another series of 5p-4f heterometallic cluster substituted POMs H₁₃(HIm)₄K₂Na₄(H₂O)₉[Sb^III₉Sb^VLn₃O₁₄(H₂O)₃][(SbW₉O₃₃)₃(PW₉O₃₄)]·26H₂O (2-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Im = imidazole) were obtained. Structural analyses indicate that both 1-Ln and 2-Ln are made up of an unprecedented 5p-4f heterometallic {Sb₁₀Ln₃O₁₄(H₂O)₃} cluster stabilized simultaneously by mixed trilacunary heteropolyanions including {A-α-PW₉O₃₄} and {B-α-SbW₉O₃₃}. Impedance measurements indicate that both compounds exhibit different proton conduction properties, and the conductivity of 2 can reach up to 1.64 × 10^-2 S cm^-1 at 85 °C under 98% relative humidity. Moreover, the fluorescence emission behaviors of both compounds have been studied.

3d-4f Heterometallic cluster incorporated polyoxoniobates with magnetic properties

A series of 3d-4f heterometallic cluster incorporated polyoxoniobates (PONbs) with different magnetic properties were first made and characterized. This work not only provides a promising strategy to make new heterometallic cluster incorporated PONbs but also demonstrates an ideal model to probe how transition-metal ions influence the magnetic property of PONbs.

Snapshots of Ce70 Toroid Assembly from Solids and Solution

Crystallization at the solid-liquid interface is difficult to spectroscopically observe and therefore challenging to understand and ultimately control at the molecular level. The Ce₇₀-torroid formulated [Ce^IV₇₀(OH)₃₆(O)₆₄(SO₄)₆₀(H₂O)₁₀]^4-, part of a larger emerging family of M^IV₇₀-materials (M = Zr, U, Ce), presents such an opportunity. We elucidated assembly mechanisms by the X-ray scattering (small-angle scattering and total scattering) of solutions and solids as well as crystallizing and identifying fragments of Ce₇₀ by single-crystal X-ray diffraction. Fragments show evidence for templated growth (Ce₅, [Ce₅(O)₃(SO₄)₁₂]^10-) and modular assembly from hexamer (Ce₆) building units (Ce₁₃, [Ce₁₃(OH)₆(O)₁₂(SO₄)₁₄(H₂O)₁₄]^6- and Ce₆₂, [Ce₆₂(OH)₃₀(O)₅₈(SO₄)₅₈]^14-). Ce₆₂, an almost complete ring, precipitates instantaneously in the presence of ammonium cations as two torqued arcs that interlock by hydrogen boding through NH₄⁺, a structural motif not observed before in inorganic systems. The room temperature rapid assemblies of both Ce₇₀ and Ce₆₂, respectively, by the addition of Li⁺ and NH₄⁺, along with ion-exchange and redox behavior, invite exploitation of this emerging material family in environmental and energy applications.

Sandwich-Type Uranyl Phosphate-Polyoxometalate Cluster Exhibiting Strong Luminescence

A pure inorganic uranyl phosphate-polyoxometalate of Na₁₇{Na@[(SbW₉O₃₃)₂(UO₂)₆(PO₃OH)₆]}·xH₂O (abbreviated as Na@U₆P₆, with x ≈ 46) featuring a sandwich-type structure was prepared using Keggin-type trilacunary [α-B-SbW₉O₃₃]^9- units as building blocks, which were formed in situ by SbCl₃ and Na₂WO₄·2H₂O. Crystal structural analysis showed that six UO₂²⁺ cations and six PO₃OH^2- anions generated a wheel-like cluster unit with a Na⁺ center ([Na@(UO₂)₆(PO₃OH)₆]⁺) that is stabilized by two [α-B-SbW₉O₃₃]^9- units. Na@U₆P₆ displayed a solid-state photoluminescence quantum yield of 33% at 300 K. The temperature-dependent fluorescence emission spectra showed that Na@U₆P₆ has temperature-sensitive fluorescence in which its emission intensity decreased by 77% as the temperature increased from 200 to 300 K. These results suggest that such uranyl phosphate-polyoxometalate clusters could serve as potential temperature-sensitive molecular materials.

Multi-Nuclear Rare-Earth-Implanted Tartaric Acid-Functionalized Selenotungstates and Their Fluorescent and Magnetic Properties

A family of multinuclear rare-earth (RE)-implanted H₂tart^2--functionalized selenotungstates (STs) [H₂N(CH₃)₂]₁₃H{[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}·31H₂O [RE = Eu³⁺ (1), Tb³⁺ (2), Dy³⁺ (3), Ho³⁺ (4), Y³⁺ (5); H₄tart = d-tartaric acid] have been afforded by a simple one-pot aqueous reaction and were structurally characterized. Intriguingly, their isomorphous organic-inorganic hybrid anion {[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}^14- includes two sandwich-type {[W₃O₆[RE₂(H₂O)₆][SeW₉O₃₃]₂}^4- dimeric units with a W-O-RE heterometal core, which are further joined by two H₂tart^2--decorated dinuclear tungsten-oxo {W₂O₅(OH)₂(H₂tart)₂} clusters and a bridging H₂tart^2- ligand, contributing to a surprising Mobius band-like configuration. It is worth emphasizing that three H₂tart^2- ligands coordinate with tungsten centers rather than RE cations. For all we know, 1-5 delegate the infrequent RE-implanted STs functionalized by triplicate H₂tart^2- bridges. Furthermore, fluorescent performances of 1-4 as well as magnetic properties of 2-4 have been surveyed. The solid-state fluorescence emission spectra prove that each of them undoubtedly shows the characteristic emission peaks of RE cores, while alternating-current susceptibility measurements suggest field-induced single-molecule magnetic behavior in 3.

Ferromagnetic Archimedean polyhedra {Fe24M18} (M = Fe, Ni, and Mn) with tunable electron configurations

Three symmetric nanocages {Fe24M18} that mimic the Archimedean polyhedra, namely pseudo-rhombicuboctahedron, were synthesized. Their electron configurations depend highly on the changes of metal ions and the deprotonation of auxiliary ligands.