Nonclassical Phosphomolybdates with Different Degrees of Reduction: Syntheses and Structural and Photo/Electrocatalytic Properties.

Four nonclassical phosphomolybdates, formulated as (H2pytty)8[{Mn(H2pytty)(H2O)3}{Sr⊂P6Mo6(V) Mo12(VI)O73}]2·16H2O (1), [{Mn(H3pytty)(H2O)3}2{Sr⊂P6Mo4(V)Mo14(VI)O73}]·18H2O (2), (H3pytp) (H2pytty)2[{Fe(H2O)4}{Sr⊂P6Mo3(V)Mo15(VI)O73}]·5H2O (3), and (H2pytty)2[{Cd(H2O)4}{Cd(H2O)3 (H3pytty)}{Sr⊂P6Mo5(V)Mo13(VI)O73}]·9H2O (4) (pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl; pytp = 4'-(4″-pyridyl)-2,4':6',4″-terpyridine) were hydrothermally synthesized and fully characterized. The penta- and hexa-reduced basket clusters represent the highest reduced level of basket-based polyoxometalate so far. In addition, transition metal complexes as bridge units were introduced to basket system for the first time to induce rare two-dimensional inorganic-organic hybrid layer. The results indicate that reduced degrees of the basket clusters of compounds 1-4 can be tuned by altering the molar ratio of organic ligand pytty and Na2MoO4. Compounds 1-4 exhibit bifunctional electrocatalytic behaviors for oxidation of dopamine and reduction of H2O2. Electrocatalytic mechanism, chronoamperometric experiments and electrocatalytic stability are studied in detail. In addition, the compounds show highly efficient catalytic ability for the degradation of typical dyes under UV irradiation.

Organic-Inorganic Hybrid Materials Based on Basket-like {Ca⊂P6Mo18O73} Cages.

Four basket-like organic-inorganic hybrids, formulated as [{Cu(II)(H2O)2}{Ca4(H2O)4(HO0.5)3(en)2}{Ca⊂P6Mo4(V)Mo14(VI)O73}]·7H2O (1), (H4bth)[{Fe(II)(H2O)}{Ca⊂P6Mo18(VI)O73}]·4H2O (2), (H2bih)3[{Cu(II)(H2O)2}{Ca⊂P6Mo2(V)Mo16(VI)O73}]·2H2O (3), (H2bib)3[{Fe(II)(H2O)2}{Ca⊂P6Mo2(V) Mo16(VI)O73}]·4H2O (4), (bth = 1,6-bis(triazole)hexane; bih = 1,6-bis(imidazol)hexane; bib = 1,4-bis(imidazole)butane) have been hydrothermally synthesized and fully characterized. Compounds 1-4 contain polyoxoanion [Ca⊂P6Mon(V)Mo18-n(VI)O73]((6+n)-) (n = 0, 2, or 4) (abbreviated as {P6Mo18O73}) as a basic building block, which is composed of a "basket body" {P2Mo14} unit and a "handle"-liked {P4Mo4} fragment encasing an alkaline-earth metal Ca(2+) cation in the cage. Compound 1 exhibits an infrequent 2D layer structure linked by the Cu(H2O)2 linker and an uncommon tetranuclear calcium complex, while compound 2 is 8-connected 2-D layers connected by binuclear {Fe2(H2O)3} segaments, which are observed for the first time as 2-D basket-like assemblies. Compounds 3 and 4 are similar 1D Z-typed chains bonded by M(H2O)2 units (M = Cu for 3 and Fe for 4). The optical band gaps of 1-4 reveal their semiconductive natures. They exhibit universal highly efficient degradation ability for typical dyes such as methylene blue, methyl orange, and rhodamine B under UV light. The lifetime and catalysis mechanism of the catalysts have been investigated. The compounds also show good bifunctional electrocatalytic behavior for oxidation of amino acids and reduction of NO2(-).

Assembly of organic-inorganic hybrid supramolecular materials based on basketlike {M⊂P6Mo18O73} (M = Ca, Sr, Ba) cage and transition-metal complex.

Eight members of basketlike mixed-valent compounds, formulated as {H(3)O}(2){Fe(III)(2,2'-bpy)(3)}(6){Sr⊂P(6)Mo(V)(4)Mo(VI)(14)O(73)}(2)·9H(2)O (1), {H(2)(4,4'-bpy)}(5){[Ni(4,4'-bpy)(H(2)O)(3)](2)[Ni(H(2)O)(2)][Sr⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)](2)}·12H(2)O (2), {Cu(2)(bim)(4)(H(2)O)}(2){[Cu(bim)(2)](2)[Cu(bim)(H(2)O)](2)Cu(H(2)O)(2)[Sr⊂P(6)Mo(V)(3)Mo(VI)(15)O(73)](2)}·16H(2)O (3), {H(3)O}(4){[Cd(phen)(2)](2)Sr(H(2)O)(5)[Sr⊂P(6)Mo(V)(4)Mo(VI)(14)O(73)]}·H(2)O (4), {Cu(bim)(2)} {[Cu(bim)(2)](2)[Cu(Hbim)(H(2)O)(2)][Ca⊂P(6)Mo(V)(3)Mo(VI)(15)O(73)]}·9H(2)O (5), {[Cu(2,2'-bpy)(H(2)O)](4)[Ca⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·4H(2)O (6), {[Cu(2,2'-bpy)(H(2)O)](4)[Sr⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·8H(2)O (7), and {[Cu(2,2'-bpy)(H(2)O)](4)[Ba⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·8H(2)O (8), have been hydrothermally synthesized and structurally characterized via elemental analysis, thermogravimetry (TG), infrared (IR) spectroscopy, ultraviolet-visible light (UV-vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), and single-crystal X-ray diffraction (XRD). The structural analysis shows that all the compounds contain basket-shaped polyoxoanions [M⊂P(6)Mo(V)(n)Mo(VI)(18-n)O(73)]((6+n)-) (M = Ca, Sr, Ba; n = 2, 3, or 4) (abbreviated as {P(6)Mo(18)O(73)}) as building units, which consists of a tetravacant γ-Dawson-type{P(2)Mo(14)} unit and a "handle"-shaped {P(4)Mo(4)} segment encapsulating a single alkaline-earth metals cation M(2+) in the central cavity. Compound 1 presents a zero-supported basketlike structure decorated by three discrete {Fe(2,2'-bipy)(3)} fragments. Compound 2 is monosupported by {Ni(4,4'-bipy)(H(2)O)(3)} subunit. Compound 3 and 4 are bisupported by copper complexes and cadmium complexes, respectively. Compound 5 exhibit a trisupported basket cluster modified with two {Cu(bim)(2)}(2+) and one {Cu(Hbim)(H(2)O)}(3+) cations. Compounds 6-8 are isostructural clusters exhibiting similar tetra-supported structures. Compound 1, 2, and 4 represent the first basket-like hybrids containing transition-metal iron, nickel, and cadmium, respectively. In addition, compounds 2, 6, 7, and 8 are observed for the first time as a two-electron-reduced basket form. The compounds display good electrocatalytic activity upon the reduction of nitrite, and fluorescent properties.

Novel antitumor agent, trilacunary Keggin-type tungstobismuthate, inhibits proliferation and induces apoptosis in human gastric cancer SGC-7901 cells.

A new one-dimensional chain-like compound of tungstobismuthate, [(W(OH)2)2 (Mn(H2O)3)2(Na3(H2O)14)(BiW9O33)2](Himi)2·16H2O (1) (imi = iminazole), has been synthesized in aqueous solution. The structure of 1 was identified by elemental analysis, IR, thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), (183)W-NMR, and single crystal X-ray diffraction. To investigate the inhibitory effect of 1 on human gastric adenocarcinoma SGC-7901 cells, cell proliferation and apoptosis initiation were examined by MTT assay (MTT = 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide), flow cytometry, nuclear staining, transmission electron microscopy, single cell gel electrophoresis, DNA fragmentation, and Western blotting. The results showed that 1 inhibited cell proliferation and induced apoptosis in SGC-7901 cells in dose-dependent manner. In addition, 1 also decreased the expression of bcl-2 protein and nuclear factor-κB p65 protein in SGC-7901 cells. And expression of bcl-2 protein exhibits a decreasing trend with increase of concentration of 1. Thus, 1 possessed a potential antitumor activity in SGC-7901 cells. This suggests that polyoxotungstates will provide a promising and novel antitumor agent in prevention and treatment of gastric adenocarcinoma.

Porous {P6Mo18O73}-type Poly(oxometalate) Metal-Organic Frameworks for Improved Pseudocapacitance and Electrochemical Sensing Performance.

{P6Mo18} poly(oxometalate) (POM) clusters have huge steric hindrance and limited active oxygen atoms, which make them difficult to combine with metal-organic units to form three-dimensional (3D) porous structures. Therefore, functionalization of such POMs has always been a bottleneck that is difficult to break through. In this study, {P6Mo18} POM was successfully grafted on a lock-like metal-organic chain to generate a multiporous coordination polymer, [{Na(H2O)(H2btb)}{Cu4I(H2O)(pz)5Cl}{H2Sr⊂P6Mo2VMo16VIO73}]·3H2O (1) (pz = pyrazine; btb = 1,4-bis(1,2,4-triazole) butane). Meanwhile, a zero-dimensional (0-D) control compound with only btb ligands as counterions, (H4btb)[H4Sr⊂P6Mo2VMo16VIO73]·3H2O (2), was also obtained via a hydrothermal reaction. Compound 1 represents the first basket-type 3D poly(oxometalate) metal-organic framework (POMOF) assembly, which possesses interpenetrating pores and complex topology. 1-GO-CPE displays improved supercapacitor (SC) performance (the specific capacitance of 929.4 F g-1 at a current density of 3 A g-1 with 94.1% of cycle efficiency after 5000 cycles) compared with 2-GO-CPE and most reported POMOF electrode materials, which may be due to the outstanding redox capability of basket-POM, introduction of metal-organic chains, intersecting pores, and excellent conductivity of graphene. An asymmetric SC device with 1-GO-CPE as the negative electrode exhibits an energy density of 29.7 Wh kg-1 with a power density of 3148.2 W kg-1 and long-lasting cycling life. In addition, 1-GO-GCE as an electrochemical sensor responds to dopamine (DA) at a voltage of 0.40 V and shows lower detection limits (0.19 µM (signal-to-noise ratio (SNR) = 3)), higher selectivity, and good reproducibility in the linear range of 0.56 µM to 0.24 mM. The ability to accurately detect the content of DA in biological samples further proves the feasibility of the sensor in practical applications.

A new organic-inorganic hybrid layered molybdenum(V) cobalt phosphate constructed from [H24(Mo16O32)Co16(PO4)24(OH)4(C5H4N)2(H2O)6](4-) wheels and 4,4'-bipyridine linkers.

A new layered molybdenum cobalt phosphate, Na(2)[Co(H(2)O)(6)][(Mo(16)O(32))Co(16)(PO(4))(4) (HPO(4))(16)(H(2)PO(4))(4)(OH)(4)(C(10)H(8)N(2))(4)(C(5)H(4)N)(2)(H(2)O)(6)]·4H(2)O (1), has been hydrothermally synthesized and structurally characterized. 1 crystallizes in the monoclinic space group P2(1)/n with a = 15.6825(18) Å, b = 39.503(4) Å, c = 17.2763(17) Å, ß = 93.791(2)°, V = 10679.4(18) Å(3), and Z = 2. A polyoxoanion of 1 exhibits an unusual organic-inorganic hybrid wheel-type cluster, in which two pyridine ligands link to the surface Co(II) atoms of a [H(24)(Mo(16)O(32))Co(16)(PO(4))(24)(OH)(4)(H(2)O)(6)] (namely, {Mo(16)Co(16)P(24)}) wheel via the Co-N bonds. Furthermore, each {Mo(16)Co(16)P(24)} wheel is connected to four adjacent wheels by four pairs of 4,4'-bipyridine linkers, forming a 2D layered network. The susceptibility measurement shows the existence of dominant antiferromagnetic interactions in 1.

Efficient and robust photocatalysts based on {P2W18} modified by an Ag complex.

Two novel Wells-Dawson polyoxometalate-based compounds, (H2bimb)2[{Ag1.5(bimb)1.5}(P2W18O62)] (1), (H2bimb)2[Ag(bimb)]0.5[Ag(eim)2]0.5[P2W18O62]·H3O (2) (bimb = 1,4-bis(imidazole-l-yl)butane, eim = ethyl(imidazole)), have been synthesized under hydrothermal conditions and characterized by IR, thermogravimetric, XRD and single-crystal X-ray diffraction analyses. In compound 1, two "U"-type bimb ligands are connected together viaπ interactions of Ag-C to form a ring unit. The ring unit alternately links with the "Z"-type bimb via an Ag-N bond to form an infinite Z-shaped {Ag4(bimb)3}n chain. The adjacent two {P2W18} clusters bonded to two Ag1 ions on two adjacent Z-shaped chains to form an inorganic dimer linker, which further joins the Z-shaped chains together, resulting in unique organic-inorganic alternating 2-D layers. Adjacent 2D layers are further aggregated together via Ag-O bonds between the Dawson cluster and the Z-type chain on different layers to yield a 3-D network with a new topology {103}2{10}{4·102}4{42·104}2. In compound 2, the eim ligand was synthesized in situ from bimb, which acts as a small molecular ligand to alter the structure and adjust the catalytic activity of compound 2. Each Ag2 connects with the bimb ligand to form a linear {Ag(bimb)} chain. Adjacent chains are bonded together via the bimb ligand to generate a supermolecule 2-D layer, in which a Dawson dimer cluster as a guest molecule is embedded in both sides of the layer through supermolecule interactions. Such 2-D layers are further supported by Ag(eim)2 units leading to 3D supermolecule nets. In addition, the compounds exhibit excellent electrocatalytic behavior and better photocatalytic degradation capability for typical dyes than other Wells-Dawson POMs.

Synthesis and photo-/electro-catalytic properties of a 3D POMOF material based on an interpenetrated copper coordination polymer linked by in situ dual ligands and Dawson-type phosphotungstates.

A novel 3D polyoxometalate metal organic framework (POMOF), [{CuCu (H2O)5(pzc)10(pz)6}{P2W18O62}2]·4H2O (1) (Hpzc = pyrazine-2-carboxylic acid, pz = pyrazine) has been hydrothermally synthesized and characterized by IR, TG, XRD, UV-vis and elemental analyses. In compound 1, the pzc and pz ligands are generated through in situ transformation from pyrazine-2,3-dicarboxylic acid (pzdc) to remove one or two CO2 molecules. The ligands with four coordination modes connect nine crystallographically independent Cu atoms to form a super-big circle unit. Each ring unit is connected to the adjacent six rings via an edge-sharing way to form a 2-D Cu/pz/pzc MOF layer, which is further extended along two spatial directions by two kinds of insert modes to generate an interpenetrating and staggered 3-D metal organic network. The {P2W18} clusters as nine-node inorganic guest molecules are grafted on the Cu/pz/pzc framework forming a complex 3D POMOF with a new topology {4·6·83·10}2 {4·6·8}2 {4·62·82·10}2{4·63·82}2{4·85}2{42·62·82}2{42·63·8}{43·67·813·1010·123}2 {4}6{6·82}2{62·8}2 {64·8·10}{6}2{8}4. Additionally, compound 1 exhibits good electrocatalytic activity for the reduction of H2O2 and effective photocatalytic degradation ability for three azo dyes under UV irradiation.

Assembly of a basket-like {Sr ⊂ P6Mo18O73} cage from 0D dimmer to 2D network and its photo-/electro-catalytic properties.

A series of basket-like heteropoly blues, formulated as (H4bth)[{Cu(H2O)}2{Sr ⊂ P6MoV2MoVI16O73}]·4H2O (1), {H2bih}3[{FeII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (2), (H2bih)3[{CoII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (3), (H2bih)3[{NiII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (4), (H2bih)2(H2bip)[{Zn (H2O)0.5}{Sr ⊂ P6MoV2MoVI16O73}]·5.5H2O (5), (bth = 1,6-bis(triazole)hexane; bih = 1,6-bis(imidazol)hexane; bip = 1,5-bis(imidazol)pentane) have been synthesized hydrothermally and fully characterized. The structural analysis shows that all the compounds contain two electron reduced polyanions [Sr ⊂ P6MoV2MoVI16O73]8− (abbreviated as {P6Mo18O73}), which consists of a tetra vacant γ-Dawson-type{P2Mo14} unit and a "handle"-shaped {P4Mo4} segment encapsulating a Sr2+ cation in the central cavity. Compound 1 is a 6-connected two-dimensional (2D) layer, which represents the first 2D assembly of basket-type polyoxometalates. Compounds 2­4 are isostructural one-dimensional zigzag chains linked by an M(H2O)2 linker (M = iron for 2, cobalt for 3, and nickel for 4). Compound 5 is a dimeric cluster supported by a binuclear {Zn2(H2O)} unit. The optical band gaps of 1­5 reveal their semiconductive natures. The compounds if used as photocatalysts exhibit a universal high efficiency degradation ability for dyes such as methylene blue, Rhodamine B, and Azon phloxine. The lifetime and reaction mechanism of the catalysts were investigated with a series of experiments. The compounds also show good bifunctional electrocatalytic behavior for the oxidation of ascorbic acid (AA) and reduction of nitrite ions.

An organic-inorganic hybrid semiconductor material based on Lindqvist polyoxomolybdate and a tetra-nuclear copper complex containing two different ligands.

A 3D organic-inorganic hybrid compound based on the Lindqvist-type polyoxometalate, [{Cu(phen)}3{Cu(µ2-ox)3}{Mo6O19}] (1) (phen = 1,10-phenanthroline, ox = oxalate), has been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, TG, PXRD, XPS, UV-vis, and single-crystal X-ray diffraction. In compound 1, three C2O4(2-) ligands bridge one Cu atom and three Cu(phen) fragments to form a tetra-nuclear copper(II) coordination complex [{Cu(phen)}3{Cu(µ2-ox)3}](2+) unit. The six-node [Mo6O19](2-) clusters are interweaved by the 6-connected tetranuclear copper(II) complex units into an intricate 3D network structure, exhibiting a 4(12)·6(3)-nbo (sodium chloride-type) topology. Compound 1 exhibits the highest connectivity of Lindqvist-type POM hybrid materials. The electrochemical behavior of 1-CPE has been investigated in detail. Furthermore, a diffuse reflectivity spectrum of 1 reveals the presence of an optical band gap and the nature of semiconductivity with a large energy gap. A magnetic susceptibility study reveals predominant antiferromagnetic interactions between the Cu(II) bridge units.

The inhibitory effects of a new cobalt-based polyoxometalate on the growth of human cancer cells.

A new cobalt-based polyoxometalate, (Himi)2[Bi(2)W2(0)O(66)(OH)(4)Co2(H2O)(6)Na(4) (H2O)14] · 17H2O (imi = iminazole) (BWCN) has been synthesized and structurally characterized. The inhibitory activities against selected human cancer lines were also determined in this study. The cell viability and chemoresistance of BWCN on human colon carcinoma HT-29 cells were assessed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide), cell morphology changes, a comet assay and western blot analysis. The typical morphologic changes of apoptosis and DNA damage indicated that BWCN could have a distinct proliferation inhibitory effect on cancer cells. BWCN as a chemotherapeutic agent also induced apoptosis on HT-29 cells and showed a significant expression of cleaved-caspase-3. These results suggested that the active site of BWCN is the polymeric anion based on the basic tectonic block {BiW(9)}, and the possible mechanism is related to the interference of DNA synthesis in cancer cells.

Three new three-dimensional organic-inorganic hybrid compounds based on PMo12O40(n-) (n = 3 or 4) polyanions and Cu(I)-pyrazine/Cu(I)-pyrazine-Cl porous coordination polymers.

Three new organic-inorganic hybrid compounds based on PMo12O40(n-) (n = 3 or 4) polyanions and Cu(I)-pz/Cu(I)-pz-Cl porous coordination polymers: [Cu(I)(pz)]3[PMo(VI)12O40] (1), [Cu(I)(pz)1.5]4[PMo(V)Mo(VI)11O40]·pz·2H2O (2), [Cu(I)3(pz)3Cl][Cu(I)2(pz)3(H2O)][PMo(V)Mo(VI)11O40] (3) (pz = pyrazine) have been hydrothermally prepared and characterized by elemental analysis, IR, TG, XRD, XPS and single-crystal X-ray diffraction. Compound 1 presents a three-dimensional Cu(I)-pz framework with cube-like chambers, into which PMo(VI)12O40(3-) Keggin ions are incorporated. Compound 2 shows a three-dimensional sandwich-like framework, and PMo(V)Mo(VI)11O40(4-) polyanions are located in the octagonal voids of every two-dimensional Cu(I)-pz 4(1)8(2) network structure. Compound 3 exhibits a two-dimensional Cl-bridged Cu(I)-pz-Cl double-layer structure, and two kinds of PMo(V)Mo(VI)11O40(4-) polyanions as bridging linkers connect two adjacent double-layers to form a three-dimensional organic-inorganic framework through Cu(I)-O bonds. Additionally, their electrochemical characters, electrocatalytic behaviors and solid state fluorescent properties at room temperature have been investigated in detail.

Influence of pH and organic ligands on the supramolecular network based on molybdenum phosphate/strontium chemistry.

Three supramolecular materials based on different poly(oxomolybdophosphate) clusters, (H(2)imi)(6)(Himi)(4)[{Sr(H(2)O)(4)}(2){Sr ⊂ P(6)Mo(4)(V)Mo(14)(VI)O(73)}(2)]·17H(2)O (1), (H(2)(4,4'-bpy))(2)[Cu(2)Sr(2)Mo(12)O(24)·(OH)(6)(H(2)O)(6)(H(2)PO(4))(2)(HPO(4))(2)(PO(4))(4)]·5H(2)O (2), and (H(2)bim)(H(2)bim)[SrP(2)Mo(5)O(23)(H(2)O)(3)]·2H(2)O (3) (imi = imidazole, 4,4'-bpy = 4,4'-bipyridine, and bim = 2,2'-biimidazole), have been hydrothermally synthesized and structurally characterized by the elemental analysis, TG, IR, UV-vis, XPS and the single-crystal X-ray diffraction. Compound 1 is made up of unusual basket-shape [Sr ⊂ P(6)Mo(18)O(73)](10-) cages linked by [Sr(H(2)O)(4)](2+) fragments to yield unprecedented dimeric chains, which represent the first 1-D assemblies of basket-type POMs. Compound 2 exhibits a novel string constructed from sandwich-like [Cu(P(4)Mo(6)O(31))(2)] units and {Sr(2)Cu} trinuclear linkers. Compound 3 is the first chain of Strandberg-type polyoxoanions connected by Sr(2+) cations. All the 1-D chains are further packed into various 3-D supramolecular assemblies via strong hydrogen-bonding interactions. The electrochemical and electrocatalysis behavior of 1, 2, and 3-CPE have been investigated in detail.

A new molybdenum(V) nickel phosphate based on divacant [H30(Mo(V)16O32)Ni14(PO4)26O2(OH)4(H2O)8]12- wheel.

A new molybdenum nickel phosphate, [H(2)en](3)Na(4)[Ni(H(2)O)(3)][H(30)(Mo(V)(16)O(32))Ni(14)(PO(4))(26)O(2) (OH)(4)(H(2)O)(8)] x 8 H(2)O 1, has been hydrothermally synthesized and structurally characterized. Compound 1 crystallizes in the monoclinic space group P2(1)/c with a = 18.6118(6) A, b = 20.9879(6) A, c = 22.9360(5) A, beta = 116.678(2) degrees, V = 8005.5(4) A(3) and Z = 2. The polyoxoanion of 1 exhibits an unusual divacant wheel-type cluster in which two {NiO(6)} octahedra are lost from the well-known "saturated" {Mo(16)TM(16)P(26)} wheel. The two vacant sites are occupied by two protonated ethylenediamines (H(2)en) via the strong hydrogen-bonding interactions between the surface O atoms of the polyoxoanions and the amine group derived from the H(2)en ligands. DC susceptibility measurements show that compound 1 exhibits strong antiferromagnetic interactions inside the wheel-type cluster.