Fullerene-like Niobovanadate Cage Built from {(Nb)V5 } Pentagon

The striking aesthetic appeal of fullerene-like clusters has captured the interest of researchers. Nevertheless, the assembly of fullerene-like polyoxovadanadate (POV) cages remains a significant challenge due to the scarcity of suitable pentagonal motif. Herein, we have successfully synthesized the first fullerene-like all-inorganic POV cage, {(V2 O)V30 Nb12 O102 (H2 O)12 } (V30 Nb12 ), by introducing Nb into the POVs. V30 Nb12 is assembled by 12 heterometallic {(Nb)V5 } pentagons through sharing V centers with Ih symmetry, reminiscent of C60 . To our knowledge, the fullerene-like V30 Nb12 not only represents the highest-nuclearity POV cage but also stands as the first niobovanadate cluster. Notably, V30 Nb12 exhibits excellent solution stability, as confirmed by ESI-MS, FT-IR and UV/Vis spectra. As there is no protection organic ligand on its outer surface, V30 Nb12 can be further modified with Cu-complexes to form a fullerene-like cluster based zigzag chain (Cu-V30 Nb12 ).

A Rhombus-Like Tetrameric Vanadoniobate Containing Pseudo-Sandwich-Type {Li ⊂ V2O8(Nb5O14)2} and Its Electrocatalytic Activity for the Selective Oxidation of Benzyl Alcohol

Ongoing research on V-containing polyoxoniobates (PONbs) is driven by their diverse structures and potential applications. Although Lindqvist-type {Nb6O19} is a widely used building block in PONbs, vanadoniobates based on {Nb6O19} and/or its derivatives are still very limited. Herein, a discrete vanadoniobate, LiNa14K11[Li2 ⊂ VIV8Nb32O110]·45H2O (1), has been synthesized by a hydrothermal method, which shows a rhombus-like tetrameric structure composed of two {V2O6(Nb6O19)} and two {Li ⊂ V2O8(Nb5O14)2} subunits derived from {Nb6O19}. Notably, the {Li ⊂ V2O8(Nb5O14)2} subunit has an interesting pseudo-sandwich-type structure, where a {LiV2O8} belt is coordinated by two monolacunary {Nb5O14} molecules and the central site of the cluster is occupied by Li+. Considering that 1 has both basic hexaniobates and redox active V centers, 1 was used as a noble metal-free electrocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde, achieving complete conversion of benzyl alcohol with 94% selectivity for benzaldehyde in 3 h under ambient conditions without using any alkaline additives. Moreover, the catalytic performance of 1 remained largely unchanged after four cycles.

A Series of Cube-Shaped Polyoxoniobates Encapsulating Octahedral Cu12X m O n Clusters With Hydrolytic Decomposition for Chemical Warfare Agents

This study reported a series of cube-shaped polyoxoniobates, {MCu₁₂O₈)(Cu₁₂X_mO_n)(Nb₇(OH)O₂₁)₈} [M = Nb(1, 2), Ln³⁺(3), X = I(1, m = 3, n = 3; 2, m = 5, n = 1), Br(3, m = 5, n = 1)]. As the first octahedral Cu₁₂X_mO_n cluster incorporated polyoxoniobate, the cube-shaped three-shell structure of {MCu₁₂O₈)(Cu₁₂X_mO_n)(Nb₇(OH)O₂₁)₈} polyanion contains a {MCu₁₂O₈} body-centered cuboctahedron, a {Cu₁₂X_mO_n} octahedron and a {Cu₁₂(Nb₇(OH)O₂₁)₈} cube. Compounds 1, 2, 3 show effective catalytic activities for the hydrolytic decomposition of chemical warefare agent simulants.

An inorganic Co-containing heteropolyoxoniobate: reversible chemochromism and H2O-dependent proton conductivity properties

A novel pure inorganic cobalt-containing heteropolyoxoniobate is constructed from crescent-shaped [SiNb18O54]14− units. It exhibits reversible chemochromism, H2O-dependent proton conductivity, water vapor adsorption and magnetic properties.

Directional Bonding in Decaniobate Inorganic Frameworks

Metal-oxo clusters offer an opportunity to assemble inorganic and metal-organic frameworks (MOFs) by a controlled building-block approach, which led to the revolutionary discoveries of zeolites and MOFs. Polyoxometalate clusters are soluble in water, but more challenging to link into frameworks; the inert oxo-caps that provide solubility are resistant to replacement or further connectivity. We demonstrate how the unique directional bonding and varying basicity of the decaniobate ([Nb₁₀ ]) oxo-caps can be exploited to build 1D, 2D, and 3D inorganic frameworks. In nine structures, A⁺ (A=Li, Na, K, Rb and Cs), AE²⁺ (AE=Ca, Sr, Ba) and Mn²⁺ demonstrate that the dimensionality of the obtained material is controlled by cation charge and size. Increased cation charge decreases selectivity for oxo-site bonding, leading to higher dimensional linking. Larger cation radii also decreases bonding selectivity, yielding higher dimensional materials. Ion-exchange studies of the A⁺ -Nb₁₀ family shows exclusive selectivity for Cs⁺ over other alkalis, which is important for radioactive Cs removal and sequestration.

Self-assembly of polyoxovanadate-capped polyoxoniobates and their catalytic decontamination of sulfur mustard simulants

Two novel polyoxovanadate-capped polyoxoniobates with non-classical structural motifs have been successfully assembled, which are active heterogeneous catalysts for the oxidative detoxification of sulfur mustard simulants.

Two synthetic routes generate two isopolyoxoniobates based on {Nb16} and {Nb20}

The directing effects of SeO₂ adduct and the different routes has yielded two novel isopolyniobates, representing new members of the polyoxoniobate family. Mass spectrometry has been applied to explore the solution behavior of compound 1.

Self-assembly and Li-ion storage performance of three new Nb/W mixed-addendum polyoxometalates based on the {SiNb3W9O40} clusters and transition-metal cations

Three polyoxometalates have been synthesized to be utilized as anode materials for lithium ion batteries.

Inorganic–organic hybrid high-dimensional polyoxotantalates and their structural transformations triggered by water

In this work, novel dimeric polyoxotantalate (POTa) clusters {Cu(en)(Ta₆O₁₉)}₂/{Cu(enMe)(Ta₆O₁₉)}₂ were introduced as SBUs to construct a new family of extended POTa materials, including the first two 3D POTa frameworks and two 2D POTa layers.

Toward Exploiting the Behavior of Niobium-Containing Mesoporous Silicates vs. Polyoxometalates in Catalysis

Classification of polyoxometalates (POMs) is based on their chemical composition, basically represented by two general formulae: a) [MmOy]p- b) [XxMmOy]q-, where M is the main transition metal, O is the oxygen atom and X can be a non-metal atom such as Si. Additionally, in the most cases, the structure of the polyoxometalates is derived from a combination of octahedral units MO6 with a central metal atom M and the oxygen atoms placed at their corners. In such octahedra, oxygen atoms allow the condensation between two octahedral units, while one oxygen atom (or max. two atoms) makes double bond with the central metal atom and is not shared with other metal atoms within the complex (terminal oxygens). On the other hand, niobium-containing mesoporous silicates contain mainly MO4 tetrahedra and reveal superior activity in heterogeneous catalysis. Thus, the proper coordination of niobium is crucial for the catalytic activity and will be deeply discussed. The similarity in the catalytic behavior of niobium-polyoxometalates and heterogeneous niobium single-site catalysts in selective oxidations will be demonstrated.

A luminescent polyoxoniobate lanthanide derivative {Eu3(H2O)9[Nb48O138(H2O)6]}27−

An Eu-containing polyoxoniobate (CN₃H₆)₇K₃H₁₇{Eu₃(H₂O)₉Nb₄₈O₁₃₈(H₂O)₆}·40H₂O is obtained under the protection of citric acid, which is a triangular cylindrical entity and displays red emission.

A Ni-containing decaniobate incorporating organic ligands: synthesis, structure, and catalysis for allylic alcohol epoxidation

Na₈{Ni[Ni(en)]₂Nb₁₀O₃₂}·28H₂O, representing the first example of trinuclear nickel-containing polyoxoniobate, has been synthesized. It was found to catalyze the epoxidation of 3-methyl-2-buten-1-ol with high conversion and selectivity.

An unprecedented 3D architecture based on a Nb/W mixed-addendum polyoxometalate and lanthanide–organic complex: synthesis, crystal structure and properties

For the first time, a 3D framework based on lanthanide-containing Nb/W mixed-addendum polyoxometalate has been obtained by utilizing the steam-assisted conversion method.

Synthesis and Characterization of [(OH)TeNb5O18](6-) in Water Solution, Comparison with [Nb6O19](8-)

Reaction of [Nb6O19](8-) with H6TeO6 in water gives telluropentaniobate [(OH)TeNb5O18](6-) (1) as single product, which was isolated as Na(+) and mixed Na(+)/K(+) salts. Crystal structures were determined for Na6[(OH)TeNb5O18]·15H2O (Na6-1) and K6Na[Nb(5.5){Te(OH)}(0.5)O(18.5)]·26H2O (K6Na-1). Formation of 1 was monitored with electrospray ionization mass spectrometry (ESI-MS) and (125)Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)TeNb5O18](6-) and [Nb6O19](8-) in borate buffer. No condensation or degradation products were detected. Reactions of 1 with {Cp*Rh}(2+) sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by (125)Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}(2+) to different {M3O3} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na3[{Cp*Rh}2TeNb5O19]·24H2O (Cp*2Rh2-1) with two {Cp*Rh}(2+) fragments capping the opposing faces of the Lindqvist anion.

An arsenicniobate-based 3D framework with selective adsorption and anion-exchange properties

An arsenicniobate-based cationic framework shows a high adsorption selectivity of water and ethanol and effectively removes toxic SCN⁻ anions.

Sulfur-centred polyoxoniobate-based 3D organic–inorganic hybrid compound and its magnetic behavior

A novel sulfur-centered polyanion {SNb₈V_9.25O_45.25} was connected by cobalt-complexes into a 3D hybrid compound showing weak ferromagnetic interaction at low temperature.

Two Rh(III)-substituted polyoxoniobates and their base-induced transformation: [H2RhNb9O28](6-) and [Rh2(OH)4Nb10O30](8-)

Two new rhodium-substituted polyoxoniobates, [H2RhNb9O28](6-) (RhNb9) and [Rh2(OH)4Nb10O30](8-) (Rh2Nb10) are reported. The two distinct Rh(III)-substituted niobate clusters behave differently when the pH is raised with TMAOH: the Rh2Nb10 is stable until pH ∼ 12.7, but RhNb9 dissociates to form RhNb5 and RhNb10, similar to some of our other metal-substituted niobates, such as the MNb9 ions (M = Cr or Mn), which transform to MNb10 when the solution pH is raised.

Design and synthesis of purely inorganic 3D frameworks composed of reduced vanadium clusters and manganese linkers

Two purely inorganic three-dimensional (3D) frameworks [Mn4(H2O)11V(IV)(18)O42(PO4)](7-) (1) and [Mn2(H2O)7V(IV)(18)O42(PO4)](11-) (2) were synthesized under hydrothermal conditions and fully characterized by single-crystal X-ray structural analysis, IR spectroscopy, thermogravimetric analysis and PXRD. Structural analysis revealed that these two compounds contained a similar all reduced polyoxoanion [V(IV)(18)O42(PO4)](15-) linked by different amounts of manganese centers to form 3D framework materials. The V centers in these two compounds were all reduced to the +IV oxidation state, resulting in an all reduced polyoxoanion, which was firstly used as the building block for constructing 3D framework materials. The all reduced typical polyoxoanion [V(IV)(18)O42(PO4)](15-) with 15 negative charges supplied enough charge amount to accept TM cations. In these two structures, the anions were surrounded by 12 and 5 Mn(2+) ions, respectively, adjusted by varying the feeding amount of MnCl2·4H2O. An electrocatalytic study revealed that compound 1 exhibits electrocatalytic activity for reduction of H2O2.

A platonic solid templating Archimedean solid: an unprecedented nanometre-sized Ag37 cluster

The spontaneous formation of discrete spherical nanosized molecules is prevalent in nature, but the authentic structural mimicry of such highly symmetric polyhedra from edge sharing of regular polygons has remained elusive. Here we present a novel ball-shaped {(HNEt3)[Ag37S4(SC6H4(t)Bu)24(CF3COO)6(H2O)12]} cluster () that is assembled via a one-pot process from polymeric {(HNEt3)2[Ag10(SC6H4(t)Bu)12]}n and CF3COOAg. Single crystal X-ray analysis confirmed that is a Td symmetric spherical molecule with a [Ag36(SC6H4(t)Bu)24] anion shell enwrapping a AgS4 tetrahedron. The shell topology of belongs to one of 13 Archimedean solids, a truncated tetrahedron with four edge-shared hexagons and trigons, which are supported by a AgS4 Platonic solid in the core. Interestingly, the cluster emits green luminescence centered at 515 nm at room temperature. Our investigations have provided a promising synthetic protocol for a high-nuclearity silver cluster based on underlying geometrical principles.

Unprecedented high-nuclear transition-metal-cluster-substituted heteropolyoxoniobates: synthesis by {V8 } ring insertion into the POM matrix and antitumor activities

Reactions of hexaniobate with vanadate in the presence of Ni(2+) , Zn(2+) , or Cu(2+) have furnished three high-nuclear vanadium cluster-substituted heteropolyoxoniobates (HPNs): {Ni(en)3 }5 H{V(V) Nb8 V(IV) 8 O44 }⋅9 H2 O (1), (H2 en)Na2 [{Zn(en)2 (Hen)}{Zn(en)2 (H2 O)}2 {PNb8 V(IV) 8 O44 }]⋅11 H2 O (2), and Na{Cu(en)2 }3 {[Cu(en)2 ]2 [PNb8 V(IV) 8 O44 ]}⋅11 H2 O (3) (en=1,2-diaminoethane). Their structures have been determined and characterized by single-crystal X-ray diffraction analysis, thermogravimetric analysis (TGA), and elemental analysis. Structural analysis has revealed that compounds 1-3 contain similar {V8 }-substituted [X(V) Nb8 V(IV) 8 O44 ](11-) (X=P, V) clusters, obtained by inserting a {V8 } ring into tetravacant HPN [XNb8 O36 ](27-) . To the best of our knowledge, compounds 1-3 represent the first high-nuclear vanadium cluster-substituted HPNs, and compound 1 is the largest vanadoniobate cluster yet obtained in HPN chemistry. Nickel and zinc cations have been introduced into HPNs for the first time, which might promise a more diverse set of structures in this family. Antitumor studies have indicated that compounds 1 and 2 exhibit high activity against human gastric cancer SGC-7901 cells, SC-1680 cells, and MG-63 cells.

Synthesis, crystal structure and photocatalytic properties of an unprecedented arsenic-disubstituted Lindqvist-type peroxopolyoxoniobate ion: {As2Nb4(O2)4O14H1.5}4.5−

An unprecedented arsenic-disubstituted Lindqvist-type ion {As₂Nb₄(O₂)₄O₁₄H_1.5}^4.5− which shows a certain photocatalytic water splitting activity has been successfully synthesized and characterized.

Highly soluble iron- and nickel-substituted decaniobates with tetramethylammonium countercations

Iron- and nickel-substituted decaniobates, [H2Fe(III)Nb9O28](6-) and [H3Ni(II)Nb9O(28)](6-) were hydrothermally synthesized as tetramethylammonium salts and the structures were determined by X-ray crystallography. The highly soluble title compounds were characterized by ESI-MS, FT-IR and UV-Vis titration.

A decatungstate-type polyoxoniobate with centered manganese: [H2Mn(IV)Nb10O32]8- as a soluble tetramethylammonium salt

A highly symmetric Mn(IV)-centered polyoxoniobate [H2Mn(IV)Nb10O32](8-) was synthesized via hydrothermal methods as a soluble tetramethylammonium salt. The structure is similar to decatungstate structure [W10O32](4-), except for the central heteroatom. The cluster is stable between 4 < pH < 10, as was characterized with ESI-MS and UV-Vis spectroscopy.