Synthesis, structures and properties of new hybrid solids containing ruthenium complexes and polyoxometalates

Two new organic-inorganic hybrid solids containing Keggin ions and ruthenium complexes have been synthesized and characterized by FT-IR, UV-vis, luminescence, X-ray, and TG analysis. In KNa[Ru(bpy)₃]₂[H₂W₁₂O₄₀]·8H₂O (1), the [Ru(bpy)₃]²⁺ (bpy=2,2′-bipyridine) complex ions are located in between the infinite one-dimensional double-chains formed by adjacent Keggin anions [H₂W₁₂O₄₀]⁶⁻ linked through {KO₇} and {NaO₆} polyhedra, while in K₆[Ru(pzc)₃]₂[SiW₁₂O₄₀]•12H₂O (2), the [Ru(pzc)₃]⁻ (pzc=pyrazine-2-carboxylate) complex anions are confined by layered networks of the [SiW₁₂O₄₀]⁴⁻ clusters connected by potassium ions. Both compounds exhibit three-dimensional frameworks through noncovalent interactions such as hydrogen bonds and anion?π interactions. Additionally, compound 1 shows strong luminescence at 604 nm in solid state at room temperature.     

Structure and characterization of zero- to two-dimensional compounds built up of the sandwich-type clusters and transition-metal linkers

Five new heteropolyoxotungstates K₂Na₂Mn₂(H₂O)₁₂[Mn₂(H₂O)₁₀Mn₄(H₂O)₂(XW₉O₃₄)₂]·18H₂O (X=Ge, 1; X=Si, 2), Na₄[Mn₄(H₂O)₁₈Mn₄(H₂O)₂(XW₉O₃₄)₂]·22H₂O (X=Ge, 3; X=Si, 4) and K₃Na₅[Mn₂(H₂O)₆Mn₄(H₂O)₂(SiW₉O₃₄)₂]·23.5H₂O (5) have been obtained by the routine synthetic reactions in aqueous solution. In 1 and 2, two isolated Mn²⁺ ions are covalently linked to the sandwich-type polyoxoanions [Mn₄(H₂O)₂(B-α-XW₉O₃₄)₂]¹²⁻ (X=Ge or Si) by two μ₂-oxygen atoms resulting in the disupporting sandwich-type polyoxometalates (POMs). Compounds 3 and 4 are built from the disupporting sandwich-type polyoxoanions 1 and 2, linked by additional four Mn²⁺ ions to construct a 1D ladder-like chain-like structure, which is rarely observed in the POM chemistry. Compound 5 represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn₄(H₂O)₂(SiW₉O₃₄)₂]¹²⁻ and the binuclear {Mn₂(H₂O)₆}⁴⁺ group. The magnetic studies of compounds 1, 4 and 5 indicate that the antiferromagnetic interactions are predominant in the three compounds between Mn(II) metal ions.     

Ionothermal syntheses of three transition-metal-containing polyoxotungstate hybrids exhibiting the photocatalytic and electrocatalytic properties

Employing the ionothermal synthesis approach, three new transition-metal-containing polyoxotungstate hybrids: [Dmim]₂Na₃[SiW₁₁O₃₉Fe(H₂O)]·H₂O (Dmim=1,3-Dimethylimidazole) (1), [Emim]₉Na₈[(SiW₉O₃₄)₃{Fe₃(μ₂-OH)₂(μ₃-O)}₃(WO₄)]·0.5H₂O(Emim=1-Ethyl-3-meth-ylimidazole) (2) and [Dmim]2[HMim]Na₆[(AsW₉O₃₃)₂{Mn^III(H₂O)}₃]·3H₂O (Dmim=1,3-Dimethylimidazole; Mim=1-Methylimidazole) (3) have been synthesized in 1-ethyl-3-methyl imidazolium bromide ([Emim]Br) ionic liquids (ILs). Compound 1 possesses a 3-D open framework constructed from the mono-iron^III-substituted α-Keggin-type anion and the organic cations [Dmim]+ through the hydrogen bond interactions. Compound 2 contains a [{Fe^III₃(μ₂-OH)₂(μ₃-O)}₃(μ₄-WO₄)] cluster surrounded by three [SiW₉O₃₄]¹⁰⁻ ligands, eight sodium cations and nine dissociative [Emim]⁺ cations around the polyoxoanion. The polyoxoanion of 3 consists of a high-valent trinuclear-manganese (III)-substituted sandwiching polyoxoanion based on the [α-AsW₉O₃₃]⁹⁻ units. All the compounds are characterized by elemental analyses, IR, UV-vis spectra, TG-DTA and XRD analyses. The XPS and EPR spectra of Mn^III in 3 were studied. The photocatalytic and electrocatalytic properties, as well as the stabilities of 1-3 were also investigated.     

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes

Two new hybrid compounds based on Keggin-type polyoxometalates: {[PMo₁₂O₄₀][Ni(Phen)₂(H₂O)]₂}·K·2OH⁻ (1) and [Cd₂(Phen)₄Cl₂][HPW₁₂O₄₀]·H₂O (2) (Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K⁺ ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW₁₂O₄₀]²⁻ and novel metal-chloride-ligand coordination complexes [Cd₂(Phen)₄Cl₂]²⁺.     

Hydrothermal assembly of (3,6)-connected networks with classical mineral structures constructed from Anderson-type heteropolymolybdate and metal cations

A series of 3D heteropolymolybdates, (NH₄)₂{[M(H₂O)₃]₂[TeMo₆O₂₄]}·H₂O (M=Mn(1), Co(2), Ni(3), Cu(4), and Zn(5)) and [Ln(H₂O)₄]₂[TeMo₆O₂₄]·3H₂O (Ln=La(6), Ce(7), and Nd(8)), has been isolated from hydrothermal reactions and characterized by elemental analyses, IR spectra, X-ray crystallography and magnetic properties. Single-crystal X-ray diffraction analysis reveals that compounds 1-8 possess unusual (3,6)-connected networks constructed from Anderson-type anions [TeMo₆O₂₄]⁶⁻ and transion metal or rare-earth metal cations. Compounds 1-5 are of highly symmetrical structures with pyrite-like topology in which [TeMo₆O₂₄]⁶⁻ anions act as 6-connected sites and transition metal cations act as 3-connected sites. Compounds 6-8 crystallize in symmetrical space groups lower than that of 1-5 exhibiting rutile-like topology with [TeMo₆O₂₄]⁶⁻ anions acting as 6-connected sites and rare-earth metal cations acting as 3-connected sites. The magnetic properties of 1-4 are also presented.     

Influence of metal ions on the structures of Keggin polyoxometalate-based solids: Hydrothermal syntheses, crystal structures and magnetic properties

Three new Keggin polyoxometalate (POM)-based compounds linked to 3d metal complexes have been synthesized under hydrothermal conditions: [Cu(phen)₂]₂{[Cu(phen)]₂ [SiMo₁₂O₄₀(VO)₂]} (1), {[Zn(phen)₂]₂[GeMo₁₂O₄₀(VO)₂]}{[Zn(phen)₂(H₂O)]₂ [GeMo₁₂O₄₀(VO)₂]}·3H₂O (2) and {[Co(phen)₂]₂[PMo₁₂O₄₀(VO)₂]}{[Co(phen)₂(OH)]₂ [PMo₁₂O₄₀(VO)₂]}·2.5H₂O (3) (phen=1,10-phenanthroline). These three compounds present, as building blocks, the bicapped Keggin anions [XMo₁₂O₄₀(VO)₂] (X=Si, Ge and P). Compound 1 consists of a bicapped Keggin anion [SiMo₁₂O₄₀(VO)₂]²⁻ linked to two [Cu(phen)]⁺ complexes with two [Cu(phen)₂]⁺ countercations. Compound 2 contains two bicapped Keggin anions [GeMo₁₂O₄₀(VO)₂]⁴⁻, one linked to two [Zn(phen)₂(H₂O)]²⁺ cations and the other one linked to two [Zn(phen)₂]²⁺ cations. Compound 3 is a two-dimensional POM-based square network formed by bicapped Keggin anions [PMo₁₂O₄₀(VO)₂]⁴⁻ connected by [Co(phen)₂]²⁺ cations. Discrete bicapped Keggin anions [PMo₁₂O₄₀(VO)₂] linked to two [Co(phen)₂(OH)]⁺ cations are located between the layers. The magnetic properties show the presence of antiferromagnetic interactions among the reduced Mo(V) atoms (in the three compounds) plus a paramagnetic contribution from the V(IV) atoms (in 1 and 2). Compound 3 shows, in addition, an antiferromagnetic interaction between the Co(II) and the V(IV) ions directly linked through an oxygen bridge. The low-temperature ESR spectra of compound 3 confirm the presence of the reduced Mo(V) ions and the antiferromagnetic coupling between the Co(II) and the V(IV) ions.     

Synthesis, crystal structure, and property of one- and two-dimensional complexes based on paradodecatungstate-B cluster

Three polyoxotungstates, Na₈[Cu(H₂O)₂(H₂W₁₂O₄₂)]·30H₂O (1), Na₈[Cd(H₂O)₂(H₂W₁₂O₄₂)]·20H₂O (2), and Na_7.4[Cd_1.3(H₂O)₂(H₂W₁₂O₄₂)]·24H₂O (3), were synthesized and characterized by elemental and thermogravimetric (TG)analysis, infrared spectroscopy and X-ray single-crystal analysis. Both complexes 1 and 2 exhibit one-dimensional structure with two neighboring paradodecatungstate-B clusters, [H₂W₁₂O₄₂]¹⁰⁻, linked by [Cu(H₂O)₂]²⁺ or [Cd(H₂O)₂]²⁺ units, while complex 3 displays a two-dimensional network structure. The electrochemical behaviors of complexes 1 and 3 were investigated in the buffer solution of pH 4.8. The results of electrocatalysis reveal that the reduced species of complexes 1 and 3 are electrocatalytically active for the reduction of nitrite. Complex 1 exhibits the electrocatalytic activity for the reduction of nitrate as well. The surface photovoltage spectroscopy (SPS) and electric field-induced SPS (EFISPS) measurements show that the surface photovoltage behavior of complex 1 is complicated while complex 3 bears the property of n-type semiconductor.     

Polyoxometalate immobilization in Cu/Ag-pz porous coordination polymers: The influences of them on the structural properties of frameworks

Three new high dimensional Cu^I/Ag-pz porous coordination polymers (PCPs) with different Keggin polyoxometalate templates have been hydrothermally synthesized: [Cu^I₅(pz)₆Cl][HPMo^VI₁₀Mo^V₂O₄₀] (1) [Ag₅(pz)₇(BW₁₂O₄₀)] (2) and [Cu^I₅(pz)₆H(H₂W₁₂O₄₀)]·4H₂O (3) (pz=pyrazine). The choice of the particular Keggin POM templates is shown to influence the structural properties of the Cu/Ag PCPs. Compound 1 shows a Cl-bridged Cu-pz-Cl double layer, between which two kinds of [HPMo^VI₁₀Mo^V₂O₄₀]⁴⁻(PMo₁₂) polyanions are located. Compound 2 presents a 3D Ag-pz framework with parallelogram-like voids, into which BW₁₂O₄₀⁵⁻ (BW₁₂) Keggin ions are incorporated. Compound 3 contains a Cu-pz cationic layer framework, between which are located [H(H₂W₁₂O₄₀)]⁵⁻ (W₁₂) Keggin ions. Primary photocatalytic experiment indicates that compound 1 presents excellent photocatalytic activity. The photoluminescence properties and electrochemistry properties of the compounds are also discussed.     

Keggin-Type Polyoxometalate Cluster Functionalized with Dinuclear M-H2biim (M = Cu, Ag) Metal–Organic Segments

Three inorganic–organic hybrid complexes, [Cu₂(H₂biim)₂(OH)₂]₂(SiW₁₂O₄₀)·2H₂O (1), [Cu₂(H₂biim)₂]₂(SiW₁₂O₄₀)·2H₂O (2) and [Ag₂(H₂biim)₂]₂(SiW₁₂O₄₀)·2H₂O (3) (H₂biim = 2, 2′-biimidazole), have been synthesized under hydrothermal conditions, and characterized by elemental analysis, IR, PXRD, TG and single-crystal X-ray diffraction. The crystallographic analysis reveals that in compounds 1–3, the Keggin polyanions [α-SiW₁₂O₄₀]^4? act as inorganic building blocks, which are linked with the dinuclear metal–organic units via Cu–O bonds in compound 1, or through supramolecular interactions in compounds 2 and 3. Compound 1 shows a 3D supramolecular structure constructed by net-like layers. Compounds 2 and 3 display 2D layer structures which were composed of wave-like chains. In addition, these compounds show electrochemical activities, and photoluminescence properties are measured in the solid state.     

Synthesis and characterization of two novel organic–inorganic hybrid solids from Keggin ions and metal coordination complexes

Two new hybrid compounds, [Co(4,4′-bpy)₂(H₂O)₄][(4,4′-bpyH₂]₂[CoW₁₂O₄₀]·8H₂O (1) and [Fe(2,2′-bpy)₃]₃[H₂W₁₂O₄₀]·6H₂O (2), (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) have been hydrothermally synthesized. These solids were characterized by elemental analysis, thermogravimetric analysis, UV–Vis spectroscopy and X-ray diffraction. The hydrogen-bonding interactions in 1 lead to the formation of a three dimensional network consisting of [CoW₁₂O₄₀]⁶⁻ anionic clusters, [Co(4,4′-bpy)₂(H₂O)₄]²⁺ cations and lattice water molecules, while the discrete Keggin ion [H₂W₁₂O₄₀]⁶⁻ in compound 2 is surrounded by 14 [Fe(2,2′-bpy)₃]²⁺ complexes through CH?O interactions (2.24–2.56 Å).     

Three new 3-D inorganic-organic coordination polymers constructed from polyoxovanadate-based heterometallic network and flexible bis(imidazole) ligand: Syntheses, structures and properties

Three new 3-D inorganic-organic polyoxovanadate-based coordination polymers [M₂(bbi)(V₂O₆)₂(H₂O)₂] [M = Co (1), Mn (2)] and [Ni₂(bbi)₃V₄O₁₂]·4H₂O (3) (bbi = 1,1-(1,4-butanediyl)bis(imidazole)) have been synthesized under hydrothermal condition and characterized by elemental analyses, IR spectra, TG and single crystal X-ray diffraction. The 3-D networks of compounds 1 and 2 are constructed from neutral {M₂V₄O₁₂} [M = Co (1), Mn (2)] layers that are pillared via the coordination of organic ligands bbi to M sites. Compound 3 is a 3-D eight-connected network, in which each binuclear [Ni₂O₄N₆] node linked with other eight adjacent nodes through two {V₄O₁₂}⁴⁻ clusters and six bbi ligands. The electrochemical behaviors of 1-3 modified carbon paste electrodes (1-CPE, 2-CPE and 3-CPE) in 1 M H₂SO₄ aqueous solution have been reported.     

Two new organic-inorganic hybrid compounds based on metal-pyrazine coordination polymers and Keggin polyoxometalates: effect of metal ions on thestructure

Through changing the metal ions, two Keggin polyoxometalates-based hybrid compounds, [Cu₅(pz)₆(Cl)(SiW₁₂O₄₀)] (1) and [Ag₄(pz)₃(H₂O)₂(SiW₁₂O₄₀)] (2) (pz=pyrazine), were hydrothermally synthesized and characterized by an elemental analysis, IR spectroscopy, thermogravimetric analyses, and single X-ray diffraction. In compound 1, the metal-organic motif exhibits a 6³ topological 2-D sheet, which is further fused by the [SiW₁₂O₄₀]⁴⁻ anions to construct a (6·7·8)(6³·7·8²)(6³)(6⁵·7)(6⁵·8) topological 3D structure. In compound 2, the bridging groups Ag₂(pz) connect the [SiW₁₂O₄₀]⁴⁻ anions to form a (5³)₂(5⁴·8²) topological 2-D layer, which is further linked by an [Ag(pz)]_nⁿ⁺ chains to construct a 3D structure with the (3⁴·4¹⁶·5²⁴·6¹²·7⁸·8²)(3⁴·4⁶·5⁴·6)₂(4·5²)₂ topology. It represents the highest connected network topology presently known for the polyoxometalates system. The structure differences of compounds 1 and 2 reveal that the coordination numbers and geometries of the metal ions have a great influence on the final structure and topology of the Keggin POMs-based hybrid compounds. In addition, the electrochemistry properties of the two compounds have been studied.     

Syntheses and electrochemical properties of three supramolecular architectures based on Keggin silicontungstates and different metal-organic units

Three new compounds [Mn(H₂O)₂(bimb)₂(H₃SiW₁₂O₄₀)₂](bimb)₄ (1), [Zn₂(bimb)₄(H₂O)₄][SiW₁₂O₄₀] (2), and [Ni₂(bimb)₄(H₂O)₄][SiW₁₂O₄₀] (3) (bimb = 1,3-bis(1-imidazoly)benzene) have been synthesized under the same hydrothermal reaction except for tuning the metal cations (Mn²⁺, Zn²⁺, and Ni²⁺). Structural characterizations show that the three compounds possess distinct structural motives. Compound 1 displays a supramolecular one-dimensional (1 D) chain formed by π···π interactions that occur among the almost parallel bimb ligands from adjacent [Mn(H₂O)₂(bimb)₂(SiW₁₂O₄₀)₂] dimers. Compound 2 shows a supramolecular two-dimensional (2D) layer achieved by intermolecular (C–H···O) hydrogen bondings between the Zn₂(bimb)₄ molecular loops and the SiW₁₂ anions. Compound 3 also exhibits a supramolecular 2D layer, but it is different from 2, which is generated by the π···π interactions among adjacent 1D polymeric chains. The distinct structural features of the three compounds suggest that the metal cations should play a significant role in the process of assembly. Additionally, the electrochemical properties of compounds 1–3 have been investigated, and the results indicate that compounds 1–3 possess excellent electrocatalytic activity toward reduction of both iodated and nitrite molecules.     

Zn-containing double complex salts formed by Keggin type polyoxotungstates: Synthesis and crystal structure

Novel double complex salts, [Zn(DMF)₆]₂[SiW₁₂O₄₀] · 2H₂O (I) and [Zn(H₂O)₂(DMF)₄][Zn(DMF)₆]₂[PW₁₂O₄₀]₂ · 6DMF (II) (DMF = N,N-dimethylformamide), were prepared by the reaction of Zn²⁺ and heteropoly acids H_x[EW₁₂O₄₀] · xH₂O (E = P, X = 3, E = Si, X = 4) in DMF. Compounds I and II were studied by X-ray diffraction (СIF files CCDC nos. 1497570 (I) and 1497571 (II)) and IR spectroscopy.     

Study on ligation of copper complexes of the quinolone antibacterial drugs and octamolybdates POMs

By introducing different quinolone antibacterial drugs into the octamolybdates POMs, four new compounds, [Cu^II(L¹)₂(H₂O)₂]H₂[β-Mo₈O₂₆]·4H₂O (1), [Cu^II₂(L²)₄][δ-Mo₈O₂₆]·4H₂O (2), [Cu^II₂(L³)₂(H₂O)₂][β-Mo₈O₂₆] (3), [Cu^II₂(L⁴)₂(H₂O)₄][β-Mo₈O₂₆]·2H₂O (4) (where L¹ = Enrofloxacin; L² = Pipemidic Acid; L³ = Norfloxacin; L⁴ = Enoxacin), have been synthesized and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, isolated Cu-Enrofloxacin coordination subunits array the both sides of β-Mo₈O₂₆, forming 3D supramolecular structure via noncovalent interactions. And the Cu-Pipemidic Acid subunits covalently link δ-Mo₈O₂₆ to form 3D supramolecular structures via short interactions in 2. In 3, the Cu-Norfloxacin motif exhibits 1D chain structure, and the tetra-dentate β-[Mo₈O₂₆]⁴⁻ clusters interact with neighboring chains to construct a 2D sheet. Similar to that of 3, the Cu-Enoxacin subunit in 4 exhibits 1D chain structure, and the bi-dentate β-[Mo₈O₂₆]⁴⁻ clusters interact with neighboring chains to construct a 2D sheet. Due to the introduction of different drug molecules, the octamolybdates POMs exhibit different isomers and structures, which bring different properties. The antitumor activities of compounds 1-4 in vitro were studied by MTT experiments, and the results show that introduction of different drug molecules onto the polyoxoanion surface can affect their antitumor activities.     

Two highly connected POM-based hybrids varying from 2D to 3D: The use of the isomeric ligands

Through employing two isomeric ligands, isonicotinic acid (HINA) and nicotinic acid (HNA), with different electron delocalization nature, two high-dimensional hybrids based on highly connected α-metatungstate clusters, [Na₂(H₂O)₈Ag₂(HINA)₃(INA)][Na(H₂O)₂Ag₂(HINA)₄(H₂W₁₂O₄₀)]·2H₂O (1) and [Na₂(H₂O)₄Ag₆(HNA)₂(NA)₂(H₂W₁₂O₄₀)]·8H₂O (2), have been conventionally synthesized and structurally characterized. 1 exhibits an unusual 1D-in-2D pseudo-polyrotaxane entangled structure, namely, the 2D sheets [Na(H₂O)₂Ag₂(HINA)₄(H₂W₁₂O₄₀)]_n³ⁿ⁻ are penetrated by enantiomorphous meso-helical chains [Na₂(H₂O)₈Ag₂(HINA)₃(INA)]_n³ⁿ⁺. In the 2D sheets, each [H₂W₁₂O₄₀]⁶⁻ cluster is surrounded by six Ag and two Na atoms. 2 exhibits a 3D (4, 6)-net structure with (3²6²7²)(3²4⁴5⁴6⁴7)(3²4⁴6⁸7) topology, in which each [H₂W₁₂O₄₀]⁶⁻ cluster is connected with ten Ag atoms. These facts indicate that the isomeric ligands play a key role in the formation of final structures. From 1 to 2, the connection number of the [H₂W₁₂O₄₀]⁶⁻ cluster changes from 8 to 10 and the dimensionality increases from 2 to 3. Moreover, 1 and 2 display photoluminescent properties in the blue range at room temperature.     

A series of pure inorganic eight-connected self-catenated network based on Silverton-type polyoxometalate

In this paper, three pure inorganic eight-connected self-catenated networks based on the Silverton-type polyoxometalate [CeMo₁₂O₄₂]⁸⁻ with lanthanide, transition metal and alkali metal cations as linkers: [Li(H₂O)₄]₂Co(H₂O)₄Ce(H₂O)₃[CeMo₁₂O₄₂]·3H₂O (1), H_0.5[Li(H₂O)₄]_2.5[Ni(H₂O)₄]_0.5Ce(H₂O)₃[CeMo₁₂O₄₂]·3H₂O (2) and H[Li(H₂O)₄]₃Ce(H₂O)₃[CeMo₁₂O₄₂]·3H₂O (3) have been successfully synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, electrochemical analyses and single crystal X-ray diffraction. The single crystal X-ray diffraction analyses reveal that compounds 1-3 are isostructural. The [Ce^IVMo₁₂O₄₂]⁸⁻ polyoxoanions are connected by Ce⁴⁺ to form the infinite 1D chains. And then the parallel stacking chains linked by transition metal cations and lithium ions construct to an eight-connected self-catenated 4²⁴56³ topology framework.     

Insertion-release of guest species and ionic conduction in polyoxometalate solids with a layer-like Anderson structure

The precipitation of Na⁺ and K⁺ mixed salts of Anderson type [SbW₆O₂₄]⁷⁻ by addition of excess of NaNO₃ and NaCl yielded polycrystalline powders of Na_2.5K_5.3[SbW₆O₂₄](NO₃)_0.8·12H₂O (1) and Na₂K_5.35[SbW₆O₂₄]Cl_0.35·12H₂O (2), respectively. The two compounds are isomorphous and exhibit a layer-like Anderson (LLA) type structure, which consists of [SbW₆O₂₄]⁷⁻-containing layers and interstitial Na⁺, K⁺, NO₃⁻ or Cl⁻, and water O atoms. Recrystallization of 1 and 2 from hot water yielded Na₂K_5.4[SbW₆O₂₄](NO₃)_0.4·12H₂O (1-recry) and Na₂K_5.25[SbW₆O₂₄]Cl_0.25·12H₂O (2-recry) as a result of partial release of NO₃⁻ and Cl⁻ (and Na⁺ and K⁺ for charge compensation). Dehydration of 1 and 2 at 400 and 500 °C (1-dehyd400 and 2-dehyd500) caused a shrinkage of lattice, but their the LLA structures retained. Simulation of X-ray diffraction (XRD) patterns for the dehydrated forms allowed to presume that the each [SbW₆O₂₄]⁷⁻ anion had been 30°-rotated within its molecular plane in order to avoid intermolecular repulsion. A compressed powder of 1-dehyd400 exhibited fast alkaline-ion conduction with a bulk conductivity of 1.2×10⁻² Ω⁻¹ cm⁻¹ at 400 °C. The hosting of a sufficient amount of NO₃⁻ together with Na⁺ for charge compensation into the lattice is crucial for high conduction.     

Hydrothermal syntheses, crystal structures and properties of 0-D, 1-D and 2-D organic-inorganic hybrid borotungstates constructed from Keggin-type heteropolyanion [α-BW12O40] and transition-metal complexes

Three novel organic-inorganic hybrid borotungstates {[Ni(phen)₂(H₂O)]₂H(α-BW₁₂O₄₀)}·4H₂O (1), [Cu^I(2,2'-bipy)(4,4′-bipy)_0.5]₂{[Cu^I(2,2′-bipy)]₂Cu^I(4,4′-bipy)₂(α-BW₁₂O₄₀)} (2) and {[Cu^I(4,4′-bipy)]₃H₂(α-BW₁₂O₄₀)}·3.5H₂O (3) (phen=1,10-phenanthroline, 2,2′-bipy=2,2′-bipyridine, 4,4′-bipy=4,4′-bipyridine) have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, UV spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), single-crystal X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and photoluminescence. The structural analysis reveals that 1 consists of a 0-D bisupporting polyoxometalate cluster where two [Ni(phen)₂(H₂O)]²⁺ cations are grafted on the polyoxoanion [α-BW₁₂O₄₀]^5- through two terminal oxygen atoms, 2 shows a 1-D infinite chain constructed from [α-BW₁₂O₄₀]^5- polyoxoanions and {[Cu^I(2,2′-bipy)]₂Cu^I(4,4′-bipy)₂}³⁺ cations by means of alternating fashion, and 3 displays an unprecedented 2D extended structure built by [α-BW₁₂O₄₀]^5- polyoxoanions and -Cu^I-4,4′-bipy- linear chains, in which each [α-BW₁₂O₄₀]^5- polyoxoanion acts as a tetradentate inorganic ligand and provides three terminal oxygen atom and one two-bridging oxygen atom. The presence of Ni^II and W^VI in 1, Cu^I ions and W^VI in 2 and 3 are identified by XPS spectra. The photoluminescence of 2 and 3 are also investigated.     

An unprecedented extended architecture constructed from a 2-D interpenetrating cationic coordination framework templated by SiW12O40 anion

A novel inorganic-organic hybrid compound based on polyoxometalates (POMs) and organic ligand formulated as [Cu₂(bpp)₄(H₂O)₂](SiW₁₂O₄₀)∼6H₂O (1) [bpp=1,3-bis(4-pyridyl)propane], was hydrothermally synthesized and structurally characterized by elemental analysis, single-crystal X-ray diffraction analysis, IR, TG, and cyclic voltammetry. Crystal data for 1: Orthorhombic, Pbcn, a=23.0085(19) Å, b=14.6379(12) Å, c=23.6226(19) Å, V=7956.0(11) Å³, Z=4, Dc=3.315 g cm^-3, and R(final)=0.0826. X-ray diffraction study reveals that compound 1 was the first interpenetrating network of 2-D metal-organic cationic coordination framework [Cu₂(bpp)₄(H₂O)₂]_n⁴ⁿ⁺, in which Keggin-type anions SiW₁₂O₄₀^4- has been used as a non-coordinating anionic template. The electrochemical property of 1-bulk modified carbon paste electrode (1-CPE) has been studied, and the results indicate that 1-CPE has good electrocatalytic activities toward the reduction of nitrite in 1 M H₂SO₄ aqueous solution.