Hexadecacobalt(II)-Containing Polyoxometalate-Based Single-Molecule Magnet

High-Nuclear Co-Added Polyoxometalate-Based Chain: Electrocatalytic Oxygen Production

A high-nuclear Co-added polyoxometalate (CoAP) was synthesized via a hydrothermal reaction: H14.5K9Na7.5-{[Co8(μ2-OH)(μ3-OH)2(H2O)2(Co(H2O)GeW6O26)(B-α-GeW9O34)2][BO(OH)2][Co12(μ2-OH)(μ3-OH)5(H2O)3(Co(H2O)GeW6O26)(GeW6O26)(B-α-GeW9O34)]}·46H2O (1). The polyoxoanion of 1 contains a large Co20 cluster gathered by lacunary GeW6O26 and GeW9O34 subunits. 1 represents a one-dimensional (1D) chain formed by adjacent polyoxoanions coupling through a CoO6 double bridge, showing the first example of a high-nuclear CoAP-based inorganic chain. 1 served as an efficient electrocatalyst in oxygen evolution reactions (OERs).

Single-Molecule Magnet Behavior of Confined Dy(III) in a Mixed Heteroatom-Substituted Polyoxotungstate

Two heteroatom-templated Dy(III)-confined polyoxotungstates [H2N(CH3)2]7Na7[Dy2(H2O)7(W4O9)(HPSeW15O54)(α-SeW9O33)2]·31H2O (1) and [H2N(CH3)2]14K2Na18{[Dy2(H2O)13W14O40]2[α-SeW9O33]4[HPSeW15O54]2}·44H2O (2) were synthesized by a one-pot aqueous reaction and structurally characterized. The most distinctive structural feature of complexes 1 & 2 is the simultaneous presence of both trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building blocks containing P(III)-Se(IV) heteroatoms. The trimeric polyanion of 1 can be represented as a fusion of two trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units encapsulating the [Dy2(H2O)7(W4O9)]12+ cluster. On the other hand, hexameric polyoxoanions of 2 are described as four trivacant Keggin [α-SeW9O33]8- and two Dawson [HPSeW15O54]10-, building units anchoring a [Dy4(H2O)26W28O80]20+ cluster. The magnetic investigation revealed the presence of significant magnetic anisotropy and slow relaxation of magnetization behavior for complex 1 with a phenomenological energy barrier, Ueff = 13.58 K in the absence of an external magnetic field, and Ueff = 24.57 K in the presence of a 500 Oe external dc magnetic field. On the other hand, complex 2 favors the QTM relaxation process in the absence of an external magnetic field and shows field-induced slow relaxation of magnetization with Ueff = 11.11 K at 1500 Oe applied dc field. The in-depth analysis of magnetic relaxation dynamics shows that the relaxation process follows the Orbach as well as Raman relaxation pathways. Further, the ab initio calculation of the studied complexes confirms that the highly axial ground and first excited energy states (containing pure highest mJ states) are responsible for the observed single-molecule magnet (SMM) behavior. Remarkably, this is the first example of a mixed heteroatom-based Dy(III)-substituted polyoxotungstate with both trimeric Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units showing SMM behavior.

Three Double-Layered {Ni8}@{Bn}2 (n = 3, 4, 6) Cluster Sandwiched Polyoxometalates

The reaction of [A-α-GeW9O34]10- with Ni2+ in the presence of inorganic boron sources yielded three unprecedented sandwiched Ni-added polyoxometalates (NiAPs): K6Na7H7[({Ni8(μ6-O)(OH)2}@{B3O6(OH)3}2)@(B-α-GeW9O34)2]·16H2O (1), K4Na4H12[({Ni8(μ6-O)}@{B4O8(OH)3}2)@(B-α-GeW9O34)2]·16H2O (2), and K10Na6[({Ni8(μ6-O)}@ {B6O9(OH)5}2)@(B-α-GeW9O34)2]·12H2O (3). The common feature of 1-3 is that a rare double-layered {Ni8}@{Bn}2 (n = 3,4,6) cluster is inlaid in their sandwich belts. The {Ni8} cluster is composed of two cubane {Ni4} clusters by six bridging oxygen atoms and sharing a μ6-O atom. The numbers of boron atoms in the {Ni8}@{Bn}2 (n = 3,4,6) clusters of 1-3 are different, namely, {Ni8}@{B3}2, {Ni8}@{B4}2, and {Ni8}@{B6}2 clusters. To the best of our knowledge, such architectures containing a double-layered {Ni8}@{Bn}2 (n = 3,4,6) cluster in the sandwich belts are the first observed in POM chemistry. Furthermore, 2 was investigated as an efficient heterogeneous catalyst for the Knoevenagel condensation of various aldehydes with malononitrile at room temperature.

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

A Hexadecanuclear Cobalt-Added Tungstogermanate Containing Counter Cobalt Hydrates: Synthesis, Structure and Photocatalytic Properties

The synthesis and exploration of the properties of structurally-new polyoxometalates (POMs) has been attracting considerable research interest. In this work, a hexadecanuclear cobalt-added tungstogermanate, H₃₁(NH₄)₅Na₁₆{Co^Ⅲ(H₂O)₆}₄{[Co^Ⅱ₄(μ₃-OH)₃(PO₄)]₄(A-α-GeW₉O₃₄)₄}₂·23-H₂O (1), was synthesized under hydrothermal conditions and characterized by various techniques. Compound 1 can effectively drive the heterogeneous photocatalytic hydrogen evolution reaction in the presence of [Ir(ppy)₂(dtbbpy)][PF₆] as the photosensitizer, with triethanolamine (TEOA) and N-Hydroxy succinimide (NHS) used as the dual sacrificial reagents. Control experiments revealed the important role of NHS in enhancing the hydrogen-evolution activities. Under optimal catalytic conditions, a hydrogen yield of 54.21 μmol was achieved after 10-h photocatalysis, corresponding to a hydrogen evolution rate of 1807.07 μmol·g^-1·h^-1. Stability studies demonstrated that catalyst 1 can be isolated and reused for three successive photocatalytic cycles with negligible decline of the H₂ yield, indicating the stability and recycling robustness of catalyst 1.

40Ni-Added Poly(polyoxometalate) Assembled by {Ni6GeW9} and {Ni8(GeW9)2} Units: Structure, Magnetic, and Heterogeneous Catalysis Properties

A novel 40Ni-added germanotungstate, Cs₈K₁₄Na₃H₃{[Ni₆(OH)₃(H₂O)₆(B-α-GeW₉O₃₄)]₂[Ni₈(μ₆-O)(μ₂-OH)₂ (μ₃-OH)₂(H₂O)B₂O₃(OH)₂(B-α-GeW₉O₃₄)₂]}₂·84H₂O (1), was made by the reaction of the trivacant [A-α-GeW₉O₃₄]^10- ({GeW₉}) precursor with Ni²⁺ cations and B₅O₈^-, and systematically investigated by Fourier-transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, and powder X-ray diffraction. Single crystal X-ray analysis indicates that the polyoxoanion of 1 is a novel octamer constructed by {Ni₆GeW₉} and {Ni₈(GeW₉)₂} structural building units via Ni-O═W linkages. The magnetic behavior shows the existence of overall ferromagnetic interactions among the Ni²⁺ centers in compound 1. Photocatalytic H₂ production studies have implied that 1 can work as a heterogeneous catalyst for hydrogen production with decent robustness and recyclability.

Structurally-New Hexadecanuclear Ni-Containing Silicotungstate with Catalytic Hydrogen Generation Activity

A structurally-new, carbon-free hexadecanuclear Ni-containing silicotungstate, [Ni₁₆(H₂O)₁₅(OH)₉(PO₄)₄(SiW₉O₃₄)₃]^19-, has been facilely synthesized using a one-pot, solution-based synthetic method systematically characterized by single-crystal X-ray diffraction and several other techniques. The resulting complex works as a noble-metal-free catalyst for visible-light-driven catalytic generation of hydrogen, by coupling with a [Ir(coumarin)₂(dtbbpy)][PF₆] photosensitizer and a triethanolamine (TEOA) sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of 842 was achieved for TBA-Ni₁₆P₄(SiW₉)₃-catalyzed hydrogen evolution system. The structural stability of TBA-Ni₁₆P₄(SiW₉)₃ catalyst under photocatalytic conditions was evaluated by the mercury-poisoning test, FT-IR, and DLS measurements. The photocatalytic mechanism was elucidated by both time-solved luminescence decay and static emission quenching measurements.

A {Co9}-Added Polyoxometalate for Efficient Visible-Light-Driven Hydrogen Evolution

A polyanion cluster H₆Na₈Cs₃[Co₉(μ₃-OH)₃(H₂O)₆(HPO₄)₂(B-α-PW₉O₃₄)₃]Cl·40H₂O (1) was made with the guidance of the lacunary directing strategy under hydrothermal conditions. Compound 1 was characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric analysis, respectively. Single-crystal X-ray diffraction analyses showed that 1 consists of three anions [B-α-PW₉O₃₄]^9- and a cyclic cationic [Co₉(μ₃-OH)₃(H₂O)₆]¹⁵⁺ and two anions HPO₄^2-. Variable-magnetic properties indicate antiferromagnetic interactions in 1. Visible-light-driven hydrogen evolution tests demonstrated that 1 was an efficient water reduction catalyst with an H₂ evolution rate of 1217.6 μmol h^-1 g^-1.

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.

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.

Hepta-Zr-Incorporated Polyoxometalate Assembly

Driven by the synergistic-directing effect of the lacunary fragments, [B-α-GeW₉O₃₄]^10- and [B-α-GeW₁₁O₃₉]^8-, an unprecedented hepta-Zr-substituted polyoxometalate (POM) assembly K₂Na₆H₁₀(Hpy)₃[SbZr₇O₆(OH)₄(B-α-GeW₉O₃₄)₂(B-α-GeW₁₁O₃₉)₂]·28H₂O (1) was made under hydrothermal condition and structurally characterized. Of which, a unique hepta-Zr cluster, [SbZr₇O₆(OH)₄]¹⁵⁺ core, was built by two trilacunary [B-α-GeW₉O₃₄]^10- fragments and two monolacunary [B-α-GeW₁₁O₃₉]^8- fragments and further arranged in a mode of a vertical cross and formed a pseudo-tetrahedron geometry. Compound 1 features the first Zr₇-cluster-substituted POM. Moreover, 1 is an effective heterogeneous catalyst for the catalytic oxidation of sulfides into the corresponding sulfones with H₂O₂, manifesting distinguished conversion, excellent yield, and desired recyclability.

Synergic coordination of multicomponents for the formation of a {Ni30} cluster substituted polyoxometalate and its in situ assembly

The synergic coordination of trz, en, and PW9 resulted in a {Ni30} cluster substituted POM, [Ni(trz)3]2@[Ni30(H2O)16]POM, that was discovered as the SBU of four frameworks which served as heterogeneous catalysts for HERs.

NiII 36 -Containing 54-Tungsto-6-Silicate: Synthesis, Structure, Magnetic and Electrochemical Studies

The 36-NiII -containing 54-tungsto-6-silicate, [Ni36 (OH)18 (H2 O)36 (SiW9 O34 )6 ]6- (Ni36 ) was synthesized by a simple one-pot reaction of the Ni2 -pivalate complex [Ni2 (μ-OH2 )(O2 CCMe3 )4 (HO2 CCMe3 )4 ] with the trilacunary [SiW9 O34 ]10- polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII 6 SiW9 } units which are linked by Ni-O-W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6 } building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6 } units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple.

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.

Robotic Stepwise Synthesis of Hetero-Multinuclear Metal Oxo Clusters as Single-Molecule Magnets

An efficient stepwise synthesis method for discovering new heteromultinuclear metal clusters using a robotic workflow is developed where numerous reaction conditions for constructing heteromultinuclear metal oxo clusters in polyoxometalates (POMs) were explored using a custom-built automated platform. As a result, new nonanuclear tetrametallic oxo clusters {FeMn₄}Lu₂A₂ in TBA₅[(A-α-SiW₉O₃₄)₂FeMn₄O₂{Lu(acac)₂}₂A₂] (II^A; A = Ag, Na, K; TBA = tetra-n-butylammonium; acac = acetylacetonate) were discovered by the installation of diamagnetic metal cations A⁺ into a paramagnetic {FeMn₄}Lu₂ unit in TBA₇[(A-α-SiW₉O₃₄)₂FeMn₄O₂{Lu(acac)₂}₂] (I). POMs II^A exhibited single-molecule magnet properties with the higher energy barriers for magnetization reversal (II^Ag, 40.0 K; II^Na, 40.3 K; II^K, 26.7 K) compared with that of the parent I (19.7 K). Importantly, these clusters with unique properties were constructed as designed by a step of the predictable sequential multistep reactions with the time-efficient platform.

{Cu8} Cluster-Sandwiched Polyoxotungstates and Their Polymers: Syntheses, Structures, and Properties

Four inorganic-organic hybrid octa-Cu cluster sandwiched polyoxotungstates (POTs), [Cu₈(H₂O)₂(en)₄(B-α-H₂SiW₉O₃₄)₂] (1), [Cu₈(H₂O)₂(en)₄(B-α-H₂GeW₉O₃₄)₂] (2), K₂[Cu₈(en)₄(B-α-HSiW₉O₃₄)₂]·6H₂O (3), and K₂[Cu₈(en)₄(B-α-HGeW₉O₃₄)₂]·2H₂O (4) (en = ethylenediamine), were hydrothermally made and characterized by single-crystal X-ray diffraction, infrared spectra, powder X-ray diffraction, and thermogravimetric analysis, respectively. Structure analysis reveals that the polyoxoanion of 1/2 is a discrete dimer built by two trivalent Keggin [B-α-XW₉O₃₄]^10- (X = Si/Ge) fragments and one octa-Cu cluster, whereas 3 and 4 display a two-dimensional network built by octa-Cu-sandwiched POT units via substitution of coordinated water on polyanions of 1 and 2 and further expand into a three-dimensional framework via K cation bridges. Ultraviolet-visible diffuse reflectance spectra reveal that 1-4 are potential semiconductor materials. Moreover, its visible light-driven catalytic H₂ evolution activity, electrochemical properties, catalysis for oxygenation reactions of thioethers, and magnetic behaviors have been investigated in detail.

Structural and Magnetical Studies of Mixed-Valence Hexavanadate Hybrids: How Organic Ligands Affect the Magnetism of Polyoxometalates?

In this Communication, we illustrate the influence of organic ligands on magnetic structure and behavior by employing a mixed-valence Lindqvist-type hexavanadate as a research platform. Through covalently attaching to different halogen-containing organic ligands, the derived hybrid materials have different magnetism compared to their parent structure. Single-crystal X-ray analyses show that the introduction of organic ligands can modify the crystal packing manners of the derivatives, leading to further changes of the interaction between magnetic units. This work demonstrates that organic functionalization can remarkably affect the magnetism of polyoxometalates by adjusting the distance and location of the magnetic fractions.

A μ-AsO4-Bridging Hexadecanuclear Ni-Substituted Polyoxotungstate

A novel tetrahedral μ-AsO₄-bridging hexadecanuclear Ni-substituted silicotungstate (ST) Na₂₁H₁₀[(AsO₄){Ni₈(OH)₆(H₂O)₂(CO₃)₂(A-α-SiW₉O₃₄)₂}₂]·60H₂O (1) was made by the reactions of trivacant [A-α-SiW₉O₃₄]^10- ({SiW₉}) units with Ni²⁺ cations and Na₃AsO₄·12H₂O and characterized by IR spectrometry, elemental analysis, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). 1 contains a novel polyoxoanion [(AsO₄){Ni₈(OH)₆(H₂O)₂(CO₃)₂(A-α-SiW₉O₃₄)₂}₂]^31- built by four trivacant Keggin [A-α-SiW₉O₃₄]^10- fragments linked through an unprecedented [(AsO₄){Ni₈(OH)₆(H₂O)₂(CO₃)₂}₂]⁹⁺ cluster, where the tetrahedral AsO₄ acts as an exclusively μ₂-bridging unit to link multiple Ni centers; such a connection mode appears for the first time in polyoxometalate chemistry. Furthermore, the electrochemical and catalytic oxidation properties of compound 1 have been investigated.

Pentadecanuclear Fe-Containing Polyoxometalate Catalyst for Visible-Light-Driven Generation of Hydrogen

The structurally new, carbon-free pentadecanuclear Fe-containing polyoxometalate, Na₂₁[NaFe₁₅(OH)₁₂(PO₄)₄(A-α-SiW₉O₃₄)₄]·85H₂O (Na₂₁-Fe₁₅P₄(SiW₉)₄), was synthesized using a facile one-pot, solution-based synthetic approach and systematically characterized by various spectroscopic techniques. Single-crystal X-ray diffraction reveals that the title complex is composed of two [Fe₄(A-α-SiW₉O₃₄)] fragments and two [Fe_3.5(A-α-SiW₉O₃₄)] fragments stabilized by four PO₄ linkers in a tetrameric style with idealized T_d point group symmetry. When coupling with (4,4'-ditert-butyl-2,2'-dipyridyl)-bis(coumarin)-iridium(III) hexafluorophosphate ([Ir(coumarin)₂(dtbbpy)][PF₆]) photosensitizer and triethanolamine (TEOA) sacrificial electron donor, polyoxoanion Fe₁₅P₄(SiW₉)₄ effectively catalyzed hydrogen production with a minimally optimized TON of 986, which represents, to our knowledge, one of the highest values among known Fe-substituted POM-catalyzed hydrogen production systems. Both a mercury-poisoning test and FT-IR characterizations proved the structural stability of Fe₁₅P₄(SiW₉)₄ catalyst under photocatalytic conditions. The photocatalytic mechanism of the present hydrogen-evolving system was investigated by time-solved luminescence and static emission quenching measurements.

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

The assembly of gigantic heterometallic metal clusters remains a great challenge for synthetic chemistry. Herein, based on the slow release strategy of lanthanide ions and in situ formation of lacunary polyoxometalates, two giant 3d-4f polyoxometalate inorganic clusters [LaNi₁₂ W₃₅ Sb₃ P₃ O₁₃₉ (OH)₆ ]^23- (LaNi₁₂ ) and [La₁₀ Ni₄₈ W₁₄₀ Sb₁₆ P₁₂ O₅₆₈ (OH)₂₄ (H₂ O)₂₀ ]^86- (La₁₀ Ni₄₈ ) are obtained. The nanoscopic inorganic cluster La₁₀ Ni₄₈ possesses a super tetrahedron structure, which can be viewed as assembly from four LaNi₁₂ molecules encapsulating a central [La₆ (SbO₃ )₄ (H₂ O)₂₀ ]⁶⁺ octahedron core. This giant aesthetic La₁₀ Ni₄₈ tetrahedron containing 214 metal ions is the largest 3d-4f cluster reported thus far in polyoxometalate system. More interestingly, the LaNi₁₂ and La₁₀ Ni₄₈ display high stability in solution and La₁₀ Ni₄₈ displays excellent proton conductivity.

FeIII 48 -Containing 96-Tungsto-16-Phosphate: Synthesis, Structure, Magnetism and Electrochemistry

The 48-FeIII -containing 96-tungsto-16-phosphate, [FeIII 48 (OH)76 (H2 O)16 (HP2 W12 O48 )8 ]36- (Fe48 ), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII 6 P2 W12 } units that are linked in an end-on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one-pot reaction of an {Fe22 } coordination complex with the hexalacunary {P2 W12 } POM precursor in water. The title polyanion was characterized by single-crystal XRD, FTIR, TGA, magnetic and electrochemical studies.

A New FeIII Substituted Arsenotungstate [FeIII2(AsIIIW6O23)2(AsIIIO3H)2]12−: Synthesis, Structure, Characterization and Magnetic Properties

The iron(III)-containing arsenotungstate [FeIII2(AsIIIW6O23)2(AsIIIO3H)2]12− (1) was prepared via a simple, one-pot reaction in aqueous basic medium. The compound was isolated as its sodium salt, and structurally-characterized by Single Crystal X-ray Diffraction (SCXRD), Powder X-ray Diffraction (PXRD), Fourier-Transform Infrared (FT-IR) spectroscopy, Thermogravimetric Analysis (TGA) and elemental analysis. Its magnetic properties are reported; the antiferromagnetic coupling between the two FeIII centers is unusually weak as a result of the bridging geometry imposed by the rigid arsenotungstate metalloligands.

Three Zr(IV)-Substituted Polyoxotungstate Aggregates: Structural Transformation from Tungstoantimonate to Tungstophosphate Induced by pH

Three novel Zr-substituted polyoxotungstate aggregates [H₂N(CH₃)₂]₇NaH₂[Zr₂Sb₂O₃(A-α-PW₉O₃₄)₂]·16H₂O (1), [H₂N(CH₃)₂]₆H₁₂[ZrSb₄(OH)O₂(A-α-PW₈O₃₂)(A-α-PW₉O₃₄)]₂·33H₂O (2), and [H₂N(CH₃)₂]₄Na_11.5H_4.5[Zr₄W₈Sb₄P₅O₄₉(OH)₅(B-α-SbW₉O₃₃)₂]·53H₂O (3) have been made in hydrothermal reactions of the [B-α-SbW₉O₃₃]^9- precursor with Zr⁴⁺ cations and PO₄^3- anions in the presence of dimethylamine hydrochloride and sodium acetate buffer (pH = 4.8) and structurally characterized. Different pH values induce structural transformation from tungstoantimonate (TA) to tungstophosphate (TP). 1 is a di-Zr-substituted sandwich-type TP, the tetranuclear heterometallic [Zr₂Sb₂O₃]⁸⁺ entity sandwiched by two [A-α-PW₉O₃₄]^9- moieties. 2 is a double sandwich-type structure, which can be perceived as two equivalent sandwiched [Sb₃(PW₈O₃₂)(PW₉O₃₄)]^11- further sandwiching one [Sb₂Zr₂(OH)₂O₄]⁴⁺ core to form a novel large-size sandwich-type architecture. Different from 1 and 2, 3 is a tetra-Zr-substituted sandwiched configuration, in which two [B-α-SbW₉O₃₃]^9- fragments sandwich a unique 21-core Sb-P-W-Zr oxo cluster ({Zr₄W₈Sb₄P₅}). Furthermore, the catalytic oxidation of aromatic thioethers by 3 as the heterogeneous catalyst has been investigated, showing high conversion and remarkable selectivity as well as excellent recyclability.

Various Anderson-type polyoxometalate-based metal–organic complexes induced by diverse solvents: assembly, structures and selective adsorption for organic dyes

A series of Anderson-type polyoxometalates (POMs)-based metal–organic complexes with different structures have been synthesized, they show excellent dye adsorption and chromatographic separation in a short time.

Two organic–inorganic hybrid polyoxotungstogermanates containing organic ligand chelated Fe–Dy heterometallic clusters and frequency dependent magnetic properties

Two organic–inorganic hybrid polyoxotungstogermanates are constructed from organic ligand chelated Fe–Dy heterometallic clusters and [B-α-GeW₉O₃₄]¹⁰⁻ units with frequency dependent magnetic properties.

A new [Co21(H2O)4(OH)12]30+ unit-incorporating polyoxotungstate for sensitive detection of dichlorvos

A new [Co₂₁(H₂O)₄(OH)₁₂]³⁰⁺ unit-incorporating polyoxotungstate (denoted as Co25Si6W60) has been hydrothermally synthesized and fully characterized. The unique Co25Si6W60-based biosensing system offers an environmentally-friendly route for detecting dichlorvos.

From Simplicity to Complexity in Grafting Dawson-Type Polyoxometalates on Porphyrin, Leading to the Formation of New Organic-Inorganic Hybrids for the Investigation of Third-Order Optical Nonlinearities

Four new organic-inorganic hybrids, [N(C₄H₉)₄]₅H[{HNC₂O(CH₂O)₃P₂V₃W₁₅O₅₉}C₄₄N₄H₂₉O₃] (TPPOH-1POM), [N(C₄H₉)₄]₁₀H₂[{HNC₂O(CH₂O)₃P₂V₃W₁₅O₅₉}₂C₄₄N₄H₂₈O₂] (TPPOH-2POM trans), [N(C₄H₉)₄]₁₀H₂[{HNC₂O(CH₂O)₃P₂V₃W₁₅O₅₉}₂C₄₄N₄H₂₈O₂] (TPPOH-2POM cis), and [N(C₄H₉)₄]₁₅H₃[{HNC₂O(CH₂O)₃P₂W₁₅V₃O₅₉}₃C₄₄N₄H₂₇O] (TPPOH-3POM), have been synthesized by covalently grafting the Dawson-type polyoxometalate (POM) [N(C₄H₉)₄]₅[H₄P₂W₁₅V₃O₆₂] onto new porphyrins N-[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]-4-[10,15,20-tris(4-hydroxyphenyl)porphyrin-5-yl]benzamide (TPPOH-1Tris), 4,4'-[5,15-bis(4-hydroxyphenyl)porphyrin-10,20-diyl]bis[ N-[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]benzamide] (TPPOH-2Tris trans), 4,4'-[10,15-bis(4-hydroxyphenyl)porphyrin-5,20-diyl]bis[ N-[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]benzamide] (TPPOH-2Tris cis). and 4,4',4″-[20-(4-hydroxyphenyl)porphyrin-5,10,15-triyl]tris[ N-[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]benzamide] (TPPOH-3Tris), respectively, in N, N-dimethylacetamide under nitrogen. The hybrid compounds were thoroughly characterized by elemental analysis, FT-IR, NMR (¹H, 2D NOESY, ³¹P, and ⁵¹V), ESI-MS, MALDI-TOF-MS, UV-vis, and fluorescence spectroscopy. All porphyrins and their corresponding hybrids exhibited remarkable third-order nonlinear-optical responses under laser irradiation, with the intensity of light at focus E₀ being 4.2 μJ at wavelength 532 nm, pulse duration τ = 6 ns, and repetition rate 10 Hz. The molecular second hyperpolarizability (γ) values of the hybrids (TPPOH-1POM, TPPOH-2POM trans, TPPOH-2POM cis, TPPOH-3POM) were calculated to be 8.48 × 10^-28 esu, 8.94 × 10^-28 esu, 10.16 × 10^-28 esu, and 8.93 × 10^-28 esu, while the molecular second hyperpolarizability (γ) of their corresponding porphyrin precursors (TPPOH-1Tris, TPPOH-2Tris trans, TPPOH-2Tris cis, and TPPOH-3Tris) were 7.19 × 10^-28 esu, 8.09 × 10^-28 esu, 9.07 × 10^-28 esu, and 7.24 × 10^-28 esu, respectively. The γ values of the cis forms were found to be superior to those of all other compounds, indicating the significant role of the greater dipole moment and low symmetry of the cis form compared to other compounds. It was also found that the fluorescence intensity was decreased by 81.52%, 90.37%, 93.93%, and 84.62% for the hybrids TPPOH-1POM, TPPOH-2POM trans, TPPOH-2POM cis, and TPPOH-3POM with respect to their corresponding precursors, respectively, which reveals the Dawson-type POM as a strong quencher. This quenching phenomenon not only indicates again unequivocally the formation of hybrid compounds but also may imply a photoinduced electron/energy-transfer process favored from a porphyrin moiety to a Dawson-type POM moiety.