Constructing Two Cu-Modified Organophosphomolybdates from a Nanocluster to a One-Dimensional Chain for Boosted Visible-Light-Driven Hydrogen Production

Photocatalytic decomposition of water to produce hydrogen H2 is an ideal way to solve energy and environmental problems, and the development of highly efficient polyoxometalate catalysts for photocatalytic hydrogen production has attracted wide attention. Herein, two Cu-modified Strandberg-type organophosphomolybdates were successfully synthesized, [Cu(C8H7N3)(H2O)2]2[(C6H5PO3)2Mo5O15]·4H2O (1) and [Cu(phen)(H2O)][Cu(phen)(H2O)2][(C6H5PO3)2Mo5O15]·2H2O (2) ([(C6H5P)2Mo5O21]Cu2) (C8H7N3 = 2-(1H-pyrazol-3-yl)pyridine, phen = 1,10-phenanthroline). Two Strandberg-type organophosphomolybdates can be used for visible-light-driven hydrogen production. Also, compound 2 exhibits an H2 production rate of 6399 μmol g-1 h-1 after 8 h light exposure in the presence of photosensitization agent [Ir(dtbbpy)(ppy)2][PF6] and TEOA. In addition, cyclic tests showed that compound 2 could be recycled four times without a significant reduction in catalytic performance. This work offers fresh insight into the development of novel polyoxometalates for efficient hydrogen evolution.

Assembly of a coordination polymer with sulphate-capped pentamolybdate units and copper: Synthesis, Structure, Magnetic and Catalytic studies

A new coordination polymer based upon the sulphate-capped pentamolybdate unit has been synthesized from the reaction of {Mo3S7Br6}2- with copper(II) bromide and pyridine, in DMF. The as-synthesized compound, formulated as...

A POM-based copper-coordination polymer crystal material for phenolic compound degradation by immobilizing horseradish peroxidase

A new polyoxometalate (POM)-based organic-inorganic hybrid Cu-coordination polymer, namely {((Cu(bipy))₂(μ-PhPO₃)₂Cu(bipy))₂H(PCuW₁₁O₃₉)·3H₂O}_n (denoted as compound 1, bipy = 2,2'-bipyridine, PhPO₃ = phenylphosphonate), was self-assembled hydrothermally. Single-crystal X-ray diffraction (SC-XRD) analysis shows that two unique types of 1D chains are present in compound 1, i.e. Cu(II)-organophosphine and organonitrogen complex cation ([((Cu(bipy))₂(μ-PhPO₃)₂Cu(bipy))₂]⁴⁺) chains and Cu-monosubstituted Keggin-type polyoxoanion ([PCuW₁₁O₃₉]^5-) chains, forming a hetero-POM. Crystalline compound 1 as a new enzyme immobilization support exhibited a high horseradish peroxidase (HRP) loading capacity (268 mg g^-1). The powder X-ray diffraction (PXRD), FTIR, zeta potential, confocal laser scanning microscopy (CLSM) and circular dichroism (CD) results show that HRP is only immobilized on the surface of compound 1 through simple physical adsorption without a secondary structure change. This POM-immobilized enzyme (HRP/1) was first used for degradation of pollutants in wastewater, and it showed a high degradation efficiency and TOC removal efficiency for phenol, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) within 30 min reaction time. Moreover, HRP/1 exhibited better operational and storage stabilities and reusability compared with free HRP. This work suggests that POMs can be used as new supports for enzyme immobilization and POM-immobilized enzymes may be used as a new kind of biocatalyst for degradation of phenolic pollutants.

Polyoxometalate-based metal–organic frameworks for heterogeneous catalysis

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

Crystal structure of tetrakis(1H-benzo[d]imidazol-3-ium) bis(μ5-phenylphosphonato)-pentakis(μ2-oxido)-decaoxo-penta-molybdenum dihydrate, C40H42Mo5N8O23P2

C40H42Mo5N8O23P2, triclinic, P1̄ (no. 2), a = 10.9867(2) Å, b = 15.4753(3) Å, c = 15.5666(3) Å, α = 85.583(2)°, β = 81.294(2)°, γ = 84.844(2)°, V = 2600.18(9) Å3, Z = 2, R gt(F) = 0.0208, wR ref(F 2) = 0.0485, T = 293(2) K.

In Vitro Anti-tumoral and Anti-bacterial Activity of an Octamolybdate Cluster-Based Hybrid Solid Incorporated with a Copper Picolinate Complex

Inorganic drugs, especially polyoxometalate-based hybrids, are expected to be developed as promising future metallodrugs. Herein, an organic-inorganic hybrid solid based on pyridine-2-carboxylic acid or picolinic acid (pic), [(Cu(pic)₂)₂(Mo₈O₂₆)]·8H₂O (1), was synthesized. A single-crystal structure of a solid possesses a discrete β-type octamolybdate cluster that supramolecularly aggregates with a {Cu₂(pic)₄}^4- complex and eight lattice water molecules. The study indicates that the solid is stable in aqueous medium and less toxic toward normal cell lines. The in vitro anti-bacterial and anti-tumor properties of the solid 1 were investigated. The results of the anti-tumor action against various human cancer cell lines, namely, lung (A549), breast (MCF-7), and liver (HepG2) cancer cells suggest that this β-octamolybdate-based solid yielded the lowest IC₅₀ value reported so far among octamolybdate anion-based hybrid solids, i.e., 24.24 μM for MCF-7, 21.56 μM for HepG2, and 25 μM for A549, indicating significant anti-cancer activity. The cell cycle analysis further reveals the observed anti-tumor effect to be governed by the arrest of breast cancer cells in the G2/M phase while that of lung and liver cancer cells in the S phase of the cell cycle. A fluorescence quenching study suggests the binding interaction between solid and ctDNA, which in turn induces apoptosis and necrosis pathways leading to cancer cell death. This is also the first study of {Mo₈O₂₆}^4- cluster-based solids as an anti-bacterial agent against Escherichia coli, and it was found to be very effective with a minimal inhibitory concentration value of ∼135 μg/mL, which is the lowest so far reported for any octamolybdate-based solid.

Effective inhibitory activity against MCF-7, A549 and HepG2 cancer cells by a phosphomolybdate based hybrid solid

A novel P₂Mo₅ cluster based hybrid solid [{4,4′-H₂bpy}{4,4′-Hbpy}₂{H₂P₂Mo₅O₂₃}]·5H₂O with effective anti-proliferation activity against MCF-7, HepG2 and A549 cancer cells comparable with a routinely used chemotherapeutic agent, methotrexate (MTX).

Synthesis, characterization and bioactivities of a new covalent copper(II) compound derived from {P2Mo5O23}6- and thiosemicarbazones

In this article, a new compound H₂[{Cu(HL)(H₂O)}₂(P₂Mo₅O₂₃)]·5H₂O (1) (HL = 2-acetylpyrazine thiosemicarbazone) has been synthesized and structurally characterized by single-crystal X-ray diffraction of and other detection techniques. Interestingly, the structure of 1 is different from many reported copper-based complexes, in which the [P₂Mo₅O₂₃]^6-, two Cu²⁺ ions and two HL were directly connected by covalent bands. Biological studies demonstrated that 1 indicated moderate antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and a better cytotoxicity against human hepatic cancer line (SMMC-7721) than Mitoxantrone (Mito), the current clinical anticancer drug. Besides, the antibacterial mechanisms of 1 have been studied by the membrane integrity disruption, the destructive reactive oxygen species generation (ROS), the glutathione (GSH) depletion and the depressed enzymatic activity of respiratory chain dehydrogenases (RCD). These results revealed that the combination of HL, Cu²⁺, [P₂Mo₅O₂₃]^6- shows a higher antibacterial and cytotoxic activity.

Copper-containing hybrid compounds based on extremely rare [V2Mo6O26]6– POM as water oxidation catalysts

Hybrid Cu/V/Mo compounds with rare [α-V₂Mo₆O₂₆]^6– and oxides prepared by their thermal degradation were used as catalysts for water oxidation.

A new hexamolybdate-based copper-2,2'-biimidazole coordination polymer serving as an acid catalyst and support for enzyme immobilization

The hydrothermal reaction of (NH₄)₃[CoMo₆O₂₄H₆]·7H₂O (CoMo₆), CuCl₂·2H₂O and 2,2'-biimidazole (H₂biim) led to the formation of a new coordination polymer, namely poly[diaquabis(2,2'-biimidazole)hexa-μ₃-oxo-octa-μ₂-oxo-hexaoxodicopper(II)hexamolybdate(VI)], [Cu₂Mo₆O₂₀(C₆H₆N₄)₂(H₂O)₂]_n (Cu-Mo₆O₂₀), at pH 2-3. It is obvious that in the formation of crystalline Cu-Mo₆O₂₀, the original Anderson-type skeleton of heteropolymolybdate CoMo₆ was broken and the new isopolyhexamolybdate Mo₆O₂₀ unit was assembled. In Cu-Mo₆O₂₀, one Mo₆O₂₀ unit connects four [Cu(H₂biim)(H₂O)]²⁺ ions in a pentacoordinate mode via four terminal O atoms, resulting in a tetra-supported structure, and each Cu^II ion is shared by two adjacent Mo₆O₂₀ units. Infinite one-dimensional chains are established by linkage between two adjacent Mo₆O₂₀ units and two Cu^II ions, and these chains are further packed into a three-dimensional framework by hydrogen bonds, π-π interactions and electrostatic attractions. The catalytic performance of this crystalline material used as an efficient and reusable heterogeneous acid catalyst for carbonyl-group protection is discussed. In addition, Cu-Mo₆O₂₀ was applied as a new support for enzyme (horseradish peroxidase, HRP) immobilization, forming immobilized enzyme HRP/Cu-Mo₆O₂₀. HRP/Cu-Mo₆O₂₀ showed good catalytic activity and could be reused.

Synthesis and properties of a POM-based trinuclear copper(ii) triazole framework

A novel POM-based trinuclear copper(ii) triazole framework, namely, [H₂{Cu₆(trz)₆(μ₃-OH)₂}Mo₅O₁₈]·3H₂O (1) was isolated using a hydrothermal method, which displays a 3D network constructed from trinuclear copper(ii) units and triazole ligands with [Mo₅O₁₈]⁶⁻ anions as templates. 1 has been identified by single crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and FT-IR. Magnetic studies indicate that antiferromagnetic interactions exist in 1. In addition, 1 exhibits good Lewis acid catalytic activity for the synthesis of cyclohexanone ethylene ketal with 95% conversion. The HOMO–LUMO gap (E_g) of 1 is 2.34 eV calculated using the Kubelka–Munk equation (Fhν)^0.5, indicating that its forbidden bandwidth belongs to the semiconductor category. Visible-light photodegradation of RhB catalyzed by 1 was investigated, which shows high activity with an above 98% degradation rate.

A novel POMs-based trinuclear copper(ii) triazole framework, namely, {[H₂Cu₆(trz)₆(μ₃-OH)₂]} [Mo₅O₁₈]·3H₂O (1) was isolated by hydrothermal method, which displays remarkable Lewis acid catalytic activity and photocatalytic activity.

Three new Strandberg-type phenylphosphomolybdate supports for immobilizing horseradish peroxidase and their catalytic oxidation performances

Three new Strandberg-type polyoxometalate TM-(PhP)2Mo5 supports for immobilizing HRP showed high adsorption capacity and good catalytic oxidation activity.

Syntheses and characterization of phosphonates and diphosphonates of molybdenum, A4[(MoO3)5(O3PR)2]·xH2O, A2[Mo2O5(O3PR)2] and A2[Mo2O5(O3P-R-PO3)] (A = K, Rb, Cs, Tl, NH4)

Cs₄[(MoO₃)₅(O₃PPh)₂]·6H₂O and K_1.5(H₃O)_0.5[Mo₂O₅(O₃PPh)₂] are molecular and non-molecular phenylphosphonates of molybdenum that contain discrete [(MoO₃)₅(O₃PPh)₂]⁴⁻ and layered [Mo₂O₅(O₃PPh)₂]²⁻ anions respectively.

Controllable assembly, characterization and catalytic properties of a new Strandberg-type organophosphotungstate

A new Strandberg-type organophosphotungstate was assembled under hydrothermal conditions and displayed good fluorescence properties and catalytic activity.