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.     

Syntheses, structures and properties of 3D inorganic-organic hybrid frameworks constructed from lanthanide polymer and Keggin-type tungstosilicate

Inorganic-organic hybrid frameworks, namely [Ce(H₂O)₃(pdc)]₄[SiW₁₂O₄₀]·6H₂O 1, [M(H₂O)₄(pdc)]₄[SiW₁₂O₄₀]·2H₂O (M=Ce for 2a, La for 2b, Nd for 2c; H₂pdc=pyridine-2,6-dicarboxylic acid) were assembled through incorporation of Keggin-type heteropolyanion [SiW₁₂O₄₀]⁴⁻ within the voids of lanthanides-pdc network as pillars or guests under hydrothermal condition. Single-crystal X-ray analyses of these crystals reveal that compound 1 presents 3D pillar-layered framework with the [SiW₁₂O₄₀]⁴⁻ anions located on the square voids of the two-dimensional Ce-pdc bilayer. Compounds 2a-c are isostructural and constructed from 3D Ln-pdc-based metal-organic framework (MOF) incorporating noncoordinating guests Keggin structure [SiW₁₂O₄₀]⁴⁻. Solid-state properties of compounds 1 and 2a-c such as thermal stability and photoluminescence have been further investigated.     

Syntheses, structures and properties of a series of photochromic hybrids based on Keggin tungstophosphates

Three inorganic-organic hybrids based on Keggin tungstophosphates and lanthanides, [Pr(NMP)₆(PW₁₂O₄₀)]_n (1), [Eu(NMP)₆(PW₁₂O₄₀)]_n (2), and [Er₂(NMP)₁₂(PW₁₂O₄₀)][PW₁₂O₄₀] (3) (NMP=N-methyl-2-pyrrolidone), have been synthesized and characterized by elemental analysis, IR, UV-vis, and single-crystal X-ray diffraction. Compounds 1 and 2 exhibit 1D infinite zigzag chain structures, while compound 3 exhibits an ionic asymmetric structure due to lanthanide contraction. The three compounds are all photochromic. The magnetic susceptibility for 1 measured over the range 2-300 K shows that there is the dominant antiferromagnetic interaction in the compound. The results of luminescent properties show that compound 2 displays an interesting selectivity for Zn²⁺ ions.     

Supramolecular assembly of organic bicapped Keggin polyoxometalate

Two novel supramolecular assemblies of organic bicapped Keggin polyoxometalates (pbpy)₈H₃[PW₁₂O₄₀]·2H₂O (1) and (pbpy)₄H[PMo₁₂O₄₀(VO)] (2) (pbpy=5-phenyl-2-(4-pyridinyl)pyridine) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Crystallographic data for compound (1), C₁₂₈H₁₀₃N₁₆O₄₂PW₁₂, triclinic, space group : a=13.4759(8) Å, b=14.6395(11) Å, c=16.5743(10) Å, α=95.764(2)°, β=102.166(2)°, γ=92.9870(10)°, Z=1, V=3171.1(4) Å³; for compound (2), C₆₄H₄₉N₈O₄₁PMo₁₂V, triclinic, space group : a=11.5377(11) Å, b=12.7552(8) Å, c=14.9599(10) Å, α=72.270(4)°, β=88.916(2)°, γ=67.865(4)°, Z=1, V=1931.0(3) Å³. X-ray analyses show that both 1 and 2 represent rare organic bicapped Keggin structures and are supported by supramolecular interactions to extend into a 3D framework. In particular, the unusual structure feature of compound 2 contains a simultaneously organic and inorganic capped structure.     

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.     

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⁺.     

Synthesis, structure and luminescent property of a new hybrid solid based on Keggin anions and silver-organonitrogen fragments

A new hybrid solid, {Ag(phen)₂}₂{[Ag(phen)]₂[PMo₁₂O₄₀]} (phen=1,10-phenanthroline) 1, constructed from one-electron-reduced mono-supported α-Keggin polyanions and silver-phenanthroline fragments via either covalent bonds or supramolecular interactions, is described. In the structure of 1, mono-supported {Ag(phen)[PMo₁₂O₄₀]}³⁻ polyanions are connected by {Ag(phen)}⁺ linking fragments to form a hybrid chain structure with engrafted phen ligands. {Ag(phen)₂}⁺ counter-cations occur in pairs trapping in strong inter-chain π-π stacking to form a three-dimensional supramolecular framework. Luminescent investigation of the compound indicates that 1 displays fascinating orange luminescent property at ambient temperature.     

Assembly of a Two-Fold Interpenetrated Three-Dimensional Metal–Organic Framework by Using the Template Function of Keggin Anions

A metal–organic framework [Co₂(btp)₃(GeMo₁₂O₄₀)] (1) (btp = 1,3-bis-(1,2,4-triazol-1-yl)propane) has been constructed by using the template function of the Keggin anions GeMo₁₂O₄₀^4?. Single-crystal X-ray analysis reveals that the structure exhibits two-fold interpenetrated 3D host metal–organic framework constructed from cobalt(II) and btp linkers and the voids of which are occupied by Keggin anions. The optical band gap of 1 indicates that it is potential wide-gap semiconductive material. The photocatalytic activity of compound 1 in degradation of MB under visible light and UV light irradiation are also investigated.     

Two new transition-metal complexes (TMCs)-templated three-dimensional supramolecular networks based on tungstovanadophosphates

Two new polyoxometalates [Ni(phen)₃][Ni(en)₃][Ni(en)₂(H₂O)₂][Ni(en)₂]_0.5[PW^VI₇W^V₂V^IV₃O₄₀(V^IVO)₂]·6H₂O (1) and [Ni(phen)₃]₂[Ni(en)₂]Na[PW^VI₇W^V₂V^IV₃O₄₀(V^IVO)₂]·8H₂O (2) (en=ethylenediamine, phen=1,10-phenanthroline) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR, EPR, XPS, elemental analysis and thermogravimetry. Their structures exhibit interesting 3D supramolecular networks, and contain new bicapped (pseudo-) Keggin-type tungsten-vanadium cluster and the template transition-metal complexes (TMCs) being generated in situ under mild hydrothermal conditions. Interestingly, compound 1 contains four different kinds of nickel complex countercations.     

Preparation, crystal structures, EPR and reflectance spectra of two new charge-transfer salts, [CpFeCpCH2N(CH3)3]4[XMo12O40] · nCH3CN (n = 0 for X = P or n = 1 for X = Ge)

Two new charge-transfer salts, [CpFeCpCH₂N(CH₃)₃]₄[PMo₁₂O₄₀] · CH₃CN (1) and [CpFeCpCH₂N(CH₃)₃]₄[GeMo₁₂O₄₀] (2), were synthesized by the traditional solution synthetic method and their structures were determined by single-crystal X-ray analysis. Salt 1 belongs to the triclinic space group P1, and salt 2 belongs to the triclinic space group . There exist the complex interactions of the cationic ferrocenyl donor and Keggin polyanion in the solid state. The solid state UV-Vis diffuse reflectance spectra indicate the presence of a charge-transfer band climbing from 450 nm to well beyond 900 nm for 1, a charge-transfer band from 460 to 850 nm with λ_max = 630 nm for 2.The EPR spectra of salts 1 and 2 at 77 K show a signal at g = 2.0048 and 1.9501, respectively, ascribed to the delocalization of one electron in reduced Keggin ion in salt 1 and the Mo^VI in [GeMo₁₂O₄₀]⁴⁻ is partly reduced to Mo^V owing to the charge-transfer transitions taking place between the ferrocenyl donors and the POM acceptors. The two compounds were also characterized by IR spectroscopy and cyclic voltammetry.     

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.     

Syntheses and characterization of novel lanthanide adamantine-dicarboxylate coordination complexes

Hydrothermal reactions of 1,10-phenanthroline (phen), 1,3-adamantanedicarboxylic acid (H₂L) and lanthanide chlorides yielded six compounds: [Ln(L)(HL)(phen)] (Ln=Pr, 1; Nd, 2), [Ln(L)(HL)(phen)(H₂O)] (Sm, 3; Eu, 4), [Tb(L)(HL)(phen)(H₂O)]₂·2H₂O (5), [Er₃(L)₄(OH)(phen)]₂ (6). Compounds 1-4 are structurally featured by one-dimensional polymeric chains; 5 hold binuclear structure constructed from eight-coordinated lanthanide center LnN₂O₆ of distorted bicapped trigonal prism bridged by dicarboxylate ligands; 6 shows that erbium ions are in mono and bicapped trigonal prismatic geometries, respectively, which are further connected by μ₃-OH to give rise to trinuclear structure. Thermogravimetric analyses of 1, 3 and 5 were performed. Fluorescent measurements of 4 and 5 were carried out, respectively.     

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.     

Syntheses, crystal structures, thermal stabilities and luminescence of six M(II)-hydroxyphosphonoacetate materials

Hydrothermal reactions of Zn^II, Ba^II or Co^II ion with 2-hydroxyphosphonoacetic acid (H₃L) afforded six metal phosphonates, namely, [Zn₅(O₃PCH(OH)CO₂)₄(C₆H₉N₂)₂] (1), [(C₄H₁₂N₂)Zn₅(O₃PCH(OH)CO₂)₄(H₂O)₂] (2), [(C₃H₁₂N₂)_0.5Zn₅(HO₃PCH(OH)CO₂)(O₃PCH(OH)CO₂)₃(H₂O)₂]·0.75H₂O (3), [BaZn₂(O₃P CH(OH)CO₂)₂] (4), [Ba(HO₃PCH(OH)CO₂)] (5) and [(NH₄)₂Co₇(HO₃PCH(OH) CO₂)₆(HPO₄)₂(H₂O)₆]·4H₂O (6). In 1, zinc tetrahedra ([ZnO₄]) and octahedra ([ZnO₅N], [ZnO₆]) are bridged by 2-hydroxyphosphonoacetate with penta- and hexadendate modes into a hybrid layer, which is further pillared by the 3-picolylamines to form a 3D structure through Zn-N bonds and hydrogen bondings. Both 2 and 3 are 3D framework encapsulating piperazine and 1,2-propanediamine cations, respectively. In solids 4-6, the cross-linkages of [ZnO₄], [BaO₁₀] and [CoO₆] polyhedral with 2-hydroxyphosphonoacetate form 3D frameworks. Solids 3 and 4 behave thermally stable up to 250 and 300 °C under air atmosphere, respectively. It is interesting that the peak emission of solid 3 displays a 10 nm red-shift after simple heat-treatment.     

Two Bisupporting Keggin-Type POM-Based Hybrids Decorated by [Zn(phen)2]2+ Fragments

Two bisupporting Keggin-type polyoxoanion-based hybrids decorated by [Zn(phen)₂]²⁺ complexes, [Zn(phen)₂]₂(PW ₁₁ ^VI W^VO₄₀) (1) and K[Zn(phen)₂(H₂O)]₂(OH) (SiW₁₂O₄₀)·H₂O (2) (phen = 1,10′-phenanthroline), have been hydrothermally synthesized, and characterized by elemental analysis, IR spectra, UV–Vis spectrum, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, and single-crystal X-ray diffraction. The structural analyses reveal that compound 1 consists of a 0D bisupporting Keggin-type heteropoly blue cluster obtained by using reductant glucose, which is grafted by two [Zn(phen)₂]²⁺ fragments; compound 2 presents a 1D infinite chain, which is constructed from bisupporting [SiW₁₂O₄₀]^4? polyoxoanions decorated by [Zn(phen)₂(H₂O)]²⁺ fragments and K⁺ ions. Additionally, the electrochemical behaviors of two compounds were studied.     

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).     

Inorganic-organic hybrid polyoxometalate: Preparation, characterization and electrochemistry properties

The solid hybrid material (H_3/4pbpy)₄[PMo₁₂O₄₀]·1.25H₂O (1) (pbpy=5-phenyl-2-(4-pyridinyl)pyridine) has been prepared and characterized. A structural feature of compound 1 is that the polyoxometalate anions exhibit a one-dimensional inorganic double chain-like structure via weak interactions of O…O. The organic moiety exhibits regular packing with offset aromatic-aromatic interactions between the pbpys, leading to a compact supramolecular framework structure to accommodate the inorganic chains. Compound 1 was employed to fabricate the three-dimensional bulk-modified carbon paste electrode (1-CPE) to research on its electrochemistry properties. The results indicate that 1 retained Keggin molybdate anion electrocatalytic activities toward the reduction of chlorate, hydrogen peroxide and nitrite.     

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.     

Molecular assemblies based on the template-directing effect of anionic polyoxometalate clusters and organic cationic flexibility

Molecular assembly processes by utilizing the template-directing effect of anionic polyoxometalate clusters and the flexible organic cation have achieved three hybrids: (H₂bpp)(Hbpp)[PMo₁₂O₄₀]·3DMF (1), (H₂bpp)(Hbpp)(bpp)₂ [PMo₉V₃O₄₀(VO)₂]₂ (2), and (H₂bpp)₂[β-Mo₈O₂₆] (3) (bpp = 1,3-bis(4-pyridyl)propane). Three compounds were characterized using single crystal X-ray crystallography, elemental analysis, IR, XPS, EPR, voltammetric behavior and TGA. Crystal structural analyses revealed that compounds 1–3 were all constructed from protonated organic bpp cations with different POM clusters: isolated α-Keggin P–Mo cluster in 1; dimer of bi-capped α-Keggin P–Mo–V anions linked through a {V₂O₂} unit in 2; β-octamolybdate isopolyanion in 3, respectively. All three assemblies demonstrated a higher thermal stability. The protonated bpp cations lost at temperature higher than 300 °C that the strong intermolecular interactions may account for the high initial temperature of weight loss. The electrochemistry property of compound 2 modified carbon paste electrode was also studied in 1 M H₂SO₄ aqueous.     

Two highly proton-conductive molecular hybrids based on ionized water clusters and poly-Keggin-anion chains

Two proton-conductive molecular hybrid complexes, {[Zn(H₂O)₈][H(H₂O)₂](HINO)₄(PMo₁₂O₄₀)}_n (1) and {[Mn(H₂O)₈][H(H₂O)_2.5](HINO)₄(PMo₁₂O₄₀)}_n (2), were constructed by introducing protonated water clusters, transition metal ionized water clusters and [PMo₁₂O₄₀]³⁻ anions in the gallery of H-bonding networks based on isonicotinic acid N-oxide (HINO). Single-crystal X-ray diffraction analyses at 293 K revealed that both complexes presented exactly the same three-dimensional (3D) hydrogen-bonded networks with large one-dimensional (1D) channels. Interestingly, [PMo₁₂O₄₀]³⁻ anions just filled in the 1D channels and self-assembled into poly-Keggin-anion chains. Thermogravimetric analyses both show no weight loss in the temperature range of 20-100 °C, indicating that all water molecules in the unit structure are not easily lost below 100 °C. Surprisingly, the proton conductivities of 1 and 2 in the temperature range of 85-100 °C under 98% RH conditions reached high proton conductivities of 10⁻³ S cm⁻¹. A possible mechanism of the proton conduction was proposed according to the experimental results.