Isopolymolybdate-Based Cobalt/Nickel Coordination Polymers Constructed by V-Type N-Donor Ligands

Four novel isopolymolybdate-based coordination polymers (CPs), constructed from 2,6-bis(1,2,4-triazol-1-yl)pyridine (btp), 1,3-bis(4H-1,2,4-triazol-4-yl)benzene (btb), and 3,5-bis(1-imidazolium)pyridine (bip), have been synthesized under a hydrothermal method: {[Co(btp)(H₂O)₂(β-Mo₈O₂₆)_0.5]·3H₂O}_n (1), [Ni(btp)(H₄Mo₆O₂₂)_0.5]_n (2), [Co(btb)(H₂O)(β-Mo₈O₂₆)_0.5]_n (3), and {[Co(Hbip)₂(H₂O)₂(γ-Mo₈O₂₆)]·6H₂O}_n (4). Complex 1 exhibits one 3D framework with an unexpected 3-nodal 2,4,6-c net topology containing the 1D {β-Mo₈O₂₆}_n chains, 6-connected Co^II centers, and V-type coordinated btp ligands. The neighboring [Mo₆O₂₂]^4- anions of complex 2 are bridged by the Ni^II centers to build one 2D {Ni₂(Mo₆O₂₂)} network, which is arranged into the 3D framework through the weak π···π stacking interactions. In compound 3, one 3D framework is formed by the adjacent 1D {Co₂(btp)₂}_n chains connected by {β-Mo₈O₂₆}_n units, which demonstrates a rare 4,6-c fsc topology. In complex 4, one 2D {Co(Hbip)₂(γ-Mo₈O₂₆)} layer with a (4, 4) network is connected to one 3D hydrogen-bonding framework via N-H···O and O-H···O hydrogen bonds. Magnetic data indicate that complexes 1 and 4 exhibit antiferromagnetic behaviors, whereas complexes 2 and 3 reveal spin-canting magnetic behavior and metamagnetic behavior, respectively. In addition, the proton conductivity of complexes 3 and 4 was investigated, showing that compound 4 has good proton conductivity at 85 °C and a relative humidity of 98% RH.

Polyoxometalate-based metal–organic frameworks for heterogeneous catalysis

POM-based MOFs simultaneously possessing the virtues of POMs and MOFs exhibit excellent heterogeneous catalytic properties.

Effects of Polyoxometalates on the Hydroxylation of N-Heterocyclic Ligands

Four polyoxometalate (POM)-based Cu complexes with the hydroxylated pyridine analogue 3-(2-hydroxylpyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl (btpo), H₃{[Cu₂(btpo)₂](PW₁₂O₄₀)}·2H₂O (1), H₃{[Cu₂(btpo)₂](PMo₁₂O₄₀)}·2H₂O (2), H₂{[Cu₂(btpo)₂](SiW₁₂O₄₀)·SO₄ (3), and H₄{[Cu₄(btpo)₄](SiW₁₂O₄₀)}·8H₂O (4), were synthesized hydrothermally under acid conditions. Single-crystal X-ray structural analysis reveals that 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl was hydroxylated into btpo in compounds 1-4, again providing structural evidence for the Gillard mechanism, in which H₂O as a weak nucleophile can attack the α-C atom of N-heterocyclic molecules at a lower pH value (ca. 1.0) with the help of POMs.

A series of new polyoxometalate-based metal-organic complexes with different rigid pyridyl-bis(triazole) ligands: assembly, structures and electrochemical properties

Five new polyoxometalate (POM)-based metal-organic complexes (MOCs) with different rigid pyridyl-bis(triazole) ligands, namely, H{Co2(Hpyttz-I)2(H2O)6[CrMo6(OH)6O18]}·8H2O (1), {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}[Co(H2O)6]·3H2O (2), {Co3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (3), {Ni3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (4), {Ni3(Hpyttz-III)2(H2O)8[γ-Mo8O26]}·10H2O (5) (H2pyttz-I = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz-II = 3-(pyrid-3-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz -III = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a two-dimensional (2D) supramolecular network based on the binuclear complex unit: [Co2(Hpyttz-I)2(H2O)6 [CrMo6(OH)6O18]]. Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex: {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}2-, the discrete [Co(H2O)6]2+ units act as counter cations. Complexes 3 and 4 are isostructural with different center metals (M = Co or Ni), the adjacent γ-Mo8O26 4- anions are linked by the MII ions to form a 1D M-γ-Mo8O26 inorganic chain. Then 1D M-γ-Mo8O26 inorganic chains are linked together by the 1D metal-organic M-(Hpyttz-II) chains to form a 3D framework. In complex 5, γ-Mo8O26 4- anions are bridged by the NiII ions to give a 1D Ni-γ-Mo8O26 inorganic chain, the adjacent 1D Ni-γ-Mo8O26 chains are connected through [Ni(Hpyttz-III)2] units to form a 2D layer. The effect of POM type and coordination site of the ligands on the structures of the title complexes were discussed. The title complexes 1, 2 and 5 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid. In addition, the redox potentials of complexes 1, 2 and 5 are highly sensitive to pH and may be used as a kind of potential pH sensor.

Solvent-controlled synthesis of various Anderson-type polyoxometalate-based metal–organic complexes with excellent capacity for the chromatographic separation of dyes

A series of Anderson-type POMs-based metal-organic complexes were synthesized in different solvents, which show excellent dye adsorption and chromatographic separation performance in a short time.

Novel polyoxometalate-based cobalt complexes based on rigid pyridyl-triazole-tetrazole and pyridyl-bis(triazole) ligands

Three novel polyoxometalate (POM)-based cobalt complexes have been synthesized and structurally characterized. The adsorption activities for organic dyes and electrochemical properties have been studied in detail.

Novel Anderson-type [TeMo6O24]6−-based metal–organic complexes tuned by different species and their coordination modes: assembly, various architectures and properties

Four novel Anderson-type polyoxometalate [TeMo₆O₂₄]⁶⁻-based metal–organic complexes were hydrothermally synthesized and characterized, which show fluorescence, electrochemical and photocatalytic properties.

The first 3D host–guest structure based on a three-fold interpenetrated Ag-pz coordination polymer network and Keggin-type aluminum tungstates with photo/electro-catalytic properties

A 3-D POMOF host–guest structure based on {AlW₁₂} and Ag-pz MOF units was prepared, which exhibit good photo- and electrocatalytic behavior.

A series of Anderson-type polyoxometalate-based metal–organic complexes: their pH-dependent electrochemical behaviour, and as electrocatalysts and photocatalysts

Seven novel polyoxometalate-based metal–organic complexes are synthesized and structurally characterized, exhibiting high electrochemical sensitivity to pH and photocatalytic activities for the degradation of organic dyes under UV irradiation.

pH-tuned diverse structures and properties: two Anderson-type polyoxometalate-based metal–organic complexes for selective photocatalysis and adsorption of organic dyes

Two novel Anderson-type POM-based metal–organic complexes were synthesized, which exhibit high selective photocatalytic activities for the degradation of organic dyes. Interestingly, 2 also shows selective adsorption capacity of organic dyes.

“Pinwheel” subunit-directed polyoxometalate-based hybrid compound [Cu(bimb)2]2[β-Mo8O26] with both helixes and chiral layers

An unprecedented hybrid octamolybdate-based compound with both chiral and helical structure, consisting of a pair of enantiomorphous chiral “pinwheel” subunits, has been synthesized and its photocatalytic properties have been investigated.

The first two-fold interpenetrating polyoxometalate-based coordination polymer with helical channels: structure and catalytic activities

A polyoxometalate-based coordination polymer POMCP-1 with a [helix + interpenetration] double configuration was successfully isolated, which shows effective catalytic activities for the esterification reaction and the photodecomposition of Rhodamine-B.

Three multi-nuclear clusters and one infinite chain induced by a pendant 4-butyl-1H-pyrazole ligand for modification of Keggin anions

By utilizing a pendant 4-butyl-1H-pyrazole, four POM-based multi-nuclear clusters or infinite chain subunits are formed: tetra-, tri- and penta-nuclear clusters in 1, 3 and 4 and an infinite chain in 2.

Three new POM-based compounds constructed by rigid thiabendazole and flexible bis(pyrazole) ligands: structures and properties for Hg2+ recognition

The introduction of S atoms to ligands induces the properties for Hg²⁺ recognition of POM-based compounds.

Two novel Anderson-type polyoxometalate-based metal–organic complexes with high-efficiency photocatalysis towards degradation of organic dyes under UV and visible light irradiation

Two novel Anderson-type polyoxometalate-based metal–organic complexes constructed from two bis-pyridyl-bis-amide ligands have been hydrothermally synthesized, showing excellent photocatalytic activities toward the degradation of dyes.

A novel polyoxometalate templated microporous metal–organic framework with electrochemical properties

A novel Wells–Dawson polyoxometalate-templated 3D microporous metal–organic framework with a rare 8⁶ uniform net was obtained, which showed electrochemical properties.

The coexistence of interconnected and interweaved double helices in an octamolybdate-based compound: synthesis, structure, and photocatalytic properties

Assembly and photocatalytic properties of an unprecedented helical compound based on polyoxometalates, with the coexistence of both interconnected and interweaved double helices, are reported.