Syntheses, structures and electrochemical properties of a class of 1-D double chain polyoxotungstate hybrids [H(2)dap][Cu(dap)(2)](0.5)[Cu(dap)(2)(H2O)][Ln(H(2)O)3(α-GeW(11)O(39))]·3H(2)O

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.

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.

Syntheses, Crystal Structure, Electrocatalytic, and Magnetic Properties of the Monolanthanide-Containing Germanotungstates [Ln(H2O) n GeW11O39]5- (Ln = Dy, Er, n = 4,3)

Two monolanthanide-containing polyanions based on monolacunary Keggin germanotungstates [Ln(H2O) n GeW11O39]5- (Ln = Dy, Er, n = 4,3) have been synthesized in simple one-pot synthetic procedure and compositionally characterized in solid state by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Electronic absorption and emission spectra of the title compounds in solution were also studied. The [DyIII(H2O)4GeW11O39]5- Keggin POM exhibits a slow relaxation of magnetization. The cyclic voltammetry measurements and mass spectrometry were carried out to check the stability of the compounds in solution. Both polyanions prove efficient in the electrocatalytic reduction of nitrite. To our knowledge, this observation establishes the first example of electrocatalysis of nitrite reduction by all inorganic monolanthanide-containing germanotungstates family.

Organic–inorganic hybrids assembled from plenary Keggin-type germanotungstate units and 3d–4f heterometal clusters

Two kinds of 3d–4f heterometal plenary Keggin germanotungstates were prepared. Their electrochemical sensing properties towards Acetaminophen detection were investigated.

Ligand-Controlled Assembly of Heteropolyoxomolybdates from Plenary Keggin Germanomolybdates and Cu-Ln Heterometallic Units

By virtue of combining an in-situ assembly process with a stepwise synthesis in conventional aqueous solution, two series of unique organic-inorganic hybrid heteropolyoxomolybdates were constructed from plenary Keggin germanomolybdates and Cu-Ln heterometallic units and fully characterized: [H₂ INA]₂ H₈ [LnCu(INA)₄ (H₂ O)₆ ]₂ [α-GeMo₁₂ O₄₀ ]₃ ⋅52 H₂ O (Ln=La³⁺ (1), Ce³⁺ (2), Pr³⁺ (3), Nd³⁺ (4), Sm³⁺ (5), Eu³⁺ (6); HINA=isonicotinic acid) and (NH₄ )[Cu(PA)₂ ][Cu(PA)₂ Ln(H₂ O)₈ ][α-GeMo₁₂ O₄₀ ]⋅10 H₂ O (Ln=Nd³⁺ (7), Sm³⁺ (8), Eu³⁺ (9); HPA=picolinic acid). The most remarkable structural characteristic of compounds 1-6 was that their molecular units were defined by three discrete plenary Keggin [α-GeMo₁₂ O₄₀ ]^4- polyoxoanions and two organic-inorganic hybrid heterometallic [LnCu(INA)₄ (H₂ O)₆ ]⁺ moieties, whereas compounds 7-9 exhibited a nice-looking 1D chain-like structure that was built from plenary [α-GeMo₁₂ O₄₀ ]^4- polyoxoanions, pendent [Cu(PA)₂ ] complexes, and bridging {[Cu(PA)₂ ][Ln(H₂ O)₈ ]}³⁺ heterometallic groups. Notably, two different pyridine carboxylic acid ligands led to the discrepancy between the two structure types. To the best of our knowledge, compounds 1-9 constitute the first examples of plenary Keggin heterometallic germanomolybdates that include Cu-Ln-organic subunits. Further studies revealed that compounds 3 and 8 exhibited fast adsorption capacity for cationic dyes methylene blue (MB) and rhodamine B (RhB) in water. Moreover, compounds 3 and 8 could quickly and selectively adsorb MB from a mixture of MB/methyl orange (MO) or MB/azophloxine (Apo).

Synthesis and characterization of self-assembled inorganic-organic hybrid arsenotungstates

A series of 12 inorganic-organic hybrid 4f-substituted arsenotungstates decorated with 3d-based complexes along with acetate bridging, viz. {[Cu₂(H₂O)(1,10-phen)₂(μ-CH₃COO)₂]₄[Ln₂(H₂O)₂(μ-CH₃COO)₂(α-AsW₁₁O₃₉)₂]}^2- (Ln^III = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), have been synthesized. These compounds were isolated using a one-pot synthetic strategy with copper, lanthanoid, trilacunary arsenotungstate and 1,10-phenanthroline as precursors. They were characterized using various analytical techniques, such as single-crystal X-ray diffraction (SC-XRD), powder XRD (PXRD), Fourier transform IR (FT-IR) spectroscopy, UV-Vis spectroscopy and thermogravimetric analysis (TGA). In all these compounds, a dinuclear Ln₂(ac)₂ moiety is sandwiched between two monolacunary [AsW₁₁O₃₉]^7- polyoxometalates (POMs), where the Ln₂(ac)₂ moiety is comprised of two acetate ligands in a μ-κO,O':κO fashion. Moreover, the anion is decorated by a copper-phenanthroline-acetate complex through a terminal O atom of the polyanion.

Synergistic Effect between Different Coordination Geometries of Lanthanides and Various Coordination Modes of 2-Picolinic Acid Ligands Tuning Three Types of Rare 3d-4f Heterometallic Tungstoantimonates

Three types of N-heterocyclic aromatic acid decorated 3d-4f heterometallic Keggin-type tungstoantimonates: Na₄[Ln(H₂O)₅]₂[Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]·26H₂O [Ln³⁺ = La³⁺ (1), Pr³⁺ (2), Nd³⁺ (3), Sm³⁺ (4), Eu³⁺ (5)], Na₆H₄[Fe₂W₄O₉(H₂O)₂(Hpic)₄ (B-β-SbW₉O₃₃)₂][Ln(H₂O)₈]₂[Fe₄W₂O₇(H₂O)₄(pic)₂(Hpic)₂(B-β-SbW₉O₃₃)₂]·38H₂O [Ln³⁺ = Gd³⁺ (6), Dy³⁺ (7)], and Na₂H₂{[Ln(H₂O)₆]₂[Fe₄(H₂O)₂(Hpic)₂(pic)₂(B-β-SbW₉O₃₃)₂]}₂·44H₂O [Ln³⁺ = Ho³⁺ (8), Er³⁺ (9), Hpic = 2-picolinic acid] have been prepared. 1-5 comprise a quadripic-inserted Krebs-type [Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]^10- moiety supported by two [Ln(H₂O)₅]³⁺ groups on both sides where it can be considered that four pic ligands replace eight aqua ligands located on the original Krebs-type [Fe₄(H₂O)₁₀(B-β-SbW₉O₃₃)₂]^10- fragment to form the [Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]^10- moiety. Remarkably, the quadripic-inserted subunits are further concatenated through the coordination role of the pic ligands to create a 3-D heterometallic framework. In contrast, the molecular units of 6-7 contain two kinds of non-Krebs-type quadripic-inserted [Fe₂W₄O₉(H₂O)₂(Hpic)₄(B-β-SbW₉O₃₃)₂]^6- and {[Ln(H₂O)₈]₂[Fe₄W₂O₇(H₂O)₄(pic)₂(Hpic)₂(B-β-SbW₉O₃₃)₂]}^4- moieties. The molecular units of 8-9 contain two identical quadripic-inserted Krebs-type {[Ln(H₂O)₆]₂[Fe₄(H₂O)₂(Hpic)₂(pic)₂(B-β-SbW₉O₃₃)₂]}^2- moieties, and both display a 1-D heterometallic double chain. For all we know, 1-9 stand for the first 3d-4f heterometallic tungstoantimonate hybrids functionalized by pic ligands. Particularly, the solid-state NIR photoluminescence (PL) spectrum in the range of 800-1450 nm of 3 and the solid-state visible PL spectra in the range of 500-750 nm of 4, 5, 7, and 8 at room temperature display the featured fluorescence emission bands stemming from Ln³⁺ cations. In the PL emission procedures of 5 and 7, energy transfer from [B-β-SbW₉O₃₃]^9- fragments and pic ligands to Ln³⁺ ions has been observed. Additionally, the correlated color temperatures of 4, 5, 7, and 8 are indexed to 2731, 2020, 4557, and 1685 K, respectively.

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

The reaction of [α-P₂W₁₅O₅₆]¹²⁻ with Mn^II and Dy^III in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na₁₀(OH₂)₄₂[{Dy(H₂O)₆}₂Mn₄P₄W₃₀O₁₁₂(H₂O)₂]·17H₂O (Dy₂Mn₄-P₂W₁₅). Single-crystal X-ray diffraction revealed that Dy₂Mn₄-P₂W₁₅ crystallizes in the triclinic system with space group P1¯, and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (Mn₄-P₂W₁₅), Na, and Dy^III cations. Compound Dy₂Mn₄-P₂W₁₅ exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy₂Mn₄-P₂W₁₅ and Mn₄-P₂W₁₅ were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻.

A new 3D POMOF with two channels consisting of Wells–Dawson arsenotungstate and {Cl4Cu10(pz)11} complexes: synthesis, crystal structure, and properties

A new 3D POMOF based on Wells–Dawson arsenotungstate was prepared using a hydrothermal reaction. The POMOF exhibits a novel topological structure, photoluminescence properties, and excellent photocatalytic activity.

Lanthanoid Template Isolation of the α-1,5 Isomer of Dicobalt(II)-Substituted Keggin Type Phosphotungstates: Syntheses, Characterization, and Magnetic Properties

A new series of heterometallic 3d-4f sandwich type phosphotungstates, [Ln{PCo2W10O38(H2O)2}2](11-) (Ln = Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III), denoted 1a-10a, respectively), have been synthesized by a one-pot reaction procedure on reacting the dilacunary K14[P2W19O69(H2O)]·24H2O precursor with Ln(NO3)3·nH2O and Co(NO3)2·6H2O in an aqueous potassium chloride solution. All the compounds were isolated as potassium salts and further characterized with different analytical techniques such as single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectrometry, elemental analysis by inductively coupled plasma atomic emission spectroscopy, magnetic measurement, and thermogravimetric analysis. Single-crystal X-ray diffraction analysis of the compounds reveals that all these compounds are isostructural and crystallized in the orthorhombic crystal system in space group Iba2. The polyanions contain the α-1,5 isomer of dicobalt-substituted α-Keggin phosphotungstate, which sandwiched lanthanoid cation and formed novel heterometallic dimer species. The temperature-dependent magnetic susceptibilities of 1a, 2a, 4a, and 7a-10a indicate the dominant contribution of the ferromagnetic interaction between Co(II) and Co(II) within the cluster, while the antiferromagnetic interaction between Co(II) and Ln(III) dominates for 3a, 5a, and 6a. The isothermal magnetizations of 1a-10a show a gradual increase in magnetization at low fields and do not reach saturation even at 50 kOe.

Supermolecular assembly of polyoxoanion and metal–organic cationic units towards a model for core–shell nanostructures

Two novel core–shell-like molecular composites [NiL₃]₄[HV^IV₁₂V^V₆O₄₂(PO₄)] and [NiL₂]₄[HV^IV₁₂V^V₆O₄₂(PO₄)] were designed and synthesized, which exhibited electrocatalytic activity for the reduction of H₂O₂ and oxidation of NO₂⁻.

Two 3d–4f double helical chains including [Dy2M2]n (M = NiII and CoII) cores exhibiting slow magnetic relaxation

Two new heterometallic complexes with one-dimensional ladder-like double-helical chain structures were prepared. They both exhibit interesting magnetic properties.

Research progress on polyoxometalate-based transition-metal–rare-earth heterometallic derived materials: synthetic strategies, structural overview and functional applications

This review summarizes the structural types of reported polyoxometalate-based transition-metal–rare-earth heterometallic derived materials (PTRHDMs) together with synthetic strategies, structural motifs and relevant functional applications.

Heterometallic 3d–4f cluster-containing polyoxotungstate obtained by partial disassembly of preformed large clusters

A new heterometallic 3d–4f tungstoantimonite, KNa₅{K₂Dy₂Cu₂(H₂O)₈(SbW₉O₃₃)₂}·17H₂O (1) was designed and synthesized by decomposition of preformed large cluster, resulting in a ring-like 3d–4f–4p cluster {K₂Dy₂Cu₂(H₂O)₈}-containing polyoxotungstate.

Two types of novel tetra-iron substituted sandwich-type arsenotungastates with supporting lanthanide pendants

Two classes of novel tetra-iron substituted sandwich-type arsenotungastates with supporting lanthanide pendants have been synthesized and characterized.

Syntheses, crystal structure, electrochemistry and luminescence properties of lanthano–germanotungstates

[Ln(α-GeW₁₁O₃₉)₂]¹³⁻ (Ln = La^III and Ce^III) and [{Ln(μ-CH₃COO)GeW₁₁O₃₉(H₂O)}₂]¹²⁻ (Ln = Pr^III, Nd^III and Sm^III) complexes were synthesized using a one-pot reaction. Similar complexes were isolated and their electrochemical and photochromic properties were studied.

Co-sensitization promoted light harvesting with a new mixed-addenda polyoxometalate [Cu(C12H8N2)2]2[V2W4O19]·4H2O in dye-sensitized solar cells

[Cu(C₁₂H₈N₂)₂]₂[V₂W₄O₁₉]·4H₂O-doped TiO₂ composites were introduced into the dye-sensitized solar cells as co-sensitizers in N719-sensitized photoanodes to enhance the photoelectric conversion efficiency.

Self-assembled arrays of polyoxometalate-based metal–organic nanotubes for proton conduction and magnetism

The first polyoxometalate-based metal–orangic nanotube via covalent bonds has been synthesized, in which POMs act as linkers holding together the metal–organic nanotubes to construct 3D nanotubular arrays.