Synthesis, Structure, and Photochemistry of an Organic Heptamolybdate-Monomolybdate

Structure Transformation of Methylammonium Polyoxomolybdates via In-Solution Acidification and Solid-State Heating from Methylammonium Monomolybdate and Application as Negative Staining Reagents for Coronavirus Observation

We prepared polyoxomolybdates with methylammonium countercations from methylammonium monomolybdate, (CH3NH3)2[MoO4], through two dehydrative condensation methods, acidifying in the aqueous solution and solid-state heating. Discrete (CH3NH3)10[Mo36O112(OH)2(H2O)14], polymeric ((CH3NH3)8[Mo36O112(H2O)14])n, and polymeric ((CH3NH3)4[γ-Mo8O26])n were selectively isolated via pH control of the aqueous (CH3NH3)2[MoO4] solution. The H2SO4-acidified solution of pH < 1 produced "sulfonated α-MoO3", polymeric ((CH3NH3)2[(MoO3)3(SO4)])n. The solid-state heating of (CH3NH3)2[MoO4] in air released methylamine and water to produce several methylammonium polyoxomolybdates in the sequence of discrete (CH3NH3)8[Mo7O24-MoO4], discrete (CH3NH3)6[Mo7O24], discrete (CH3NH3)8[Mo10O34], and polymeric ((CH3NH3)4[γ-Mo8O26])n, before their transformation into molybdenum oxides such as hexagonal-MoO3 and α-MoO3. Notably, some of their polyoxomolybdate structures were different from polyoxomolybdates produced from ammonium molybdates, such as (NH4)2[MoO4] or (NH4)6[Mo7O24], indicating that countercation affected the polyoxomolybdate structure. Moreover, among the tested polyoxomolybdates, (CH3NH3)6[Mo7O24] was the best negative staining reagent for the observation of the SARS-CoV-2 virus using transmission electron microscopy.

Smart Organic-Inorganic Polyoxomolybdates in Forward Osmosis for Antiviral-Drug Wastewater Treatment and Drug Reclamation

The demand to effectively treat medical wastewater has escalated with the much greater use of antiviral drugs since the COVID-19 pandemic. Forward osmosis (FO) has great potential in wastewater treatment only when appropriate draw solutes are available. Here, we synthesize a series of smart organic-inorganic polyoxomolybdates (POMs), namely, (NH₄)₆[Mo₇O₂₄], (PrNH₃)₆[Mo₇O₂₄], (ⁱPrNH₃)₆[Mo₇O₂₄], and (BuNH₃)₆[Mo₇O₂₄], for FO to treat antiviral-drug wastewater. Influential factors of separation performance have been systematically studied by tailoring the structure, organic characteristics, and cation chain length of POMs. POMs at 0.4 M produce water fluxes ranging from 14.0 to 16.4 LMH with negligible solute losses, at least 116% higher than those of NaCl, NH₄HCO₃, and other draw solutes. (NH₄)₆[Mo₇O₂₄] creates a water flux of 11.2 LMH, increased by more than 200% compared to that of NaCl and NH₄HCO₃ in long-term antiviral-drug wastewater reclamation. Remarkably, the drugs treated with NH₄HCO₃ and NaCl are either contaminated or denatured, while those with (NH₄)₆[Mo₇O₂₄] remain intact. Moreover, these POMs are recovered by sunlight-assisted acidification owing to their light and pH dual sensitivity and reusability for FO. POMs prove their suitability as draw solutes and demonstrate their superiority over the commonly studied draw solutes in wastewater treatment.

Synthesis, structure characterization and properties of a new oxidovanadium(IV) coordination polymer incorporating bridging (MoO4)2– and (Mo8O26)4– ligands

Hydrothermal synthesis, crystal structure and properties of a new heterometallic coordination polymer [(VO(terpy))4(MoO4)2(Mo8O26)]·2H2O (1) (terpy = 2,2′;6′,2″-terpyridine) are reported. Compound 1 contains two crystallographically unique vanadium(IV) atoms, bonded to a terminal oxido ligand and further coordinated to a terpy ligand. The three N atoms of terpy occupy the meridional sites of a distorted {VN3O3} octahedron. A γ-octamolybdate (Mo8O26)4– located on an inversion centre and a tetraoxidomolybdate (MoO4)2– function as bridging ligands. The μ3-bridging tridentate binding of (MoO4)2– leads to the formation of a {V4Mo2O12}4+ cationic unit consisting of an eight-membered heterometallic {Mo2V2O4} ring with protruding oxidovanadium handles. A pair of {V4Mo2O12}4+ units are bridged by the centrosymmetric (Mo8O26)4– ligand, resulting in the formation of an infinite chain of alternating {V4Mo2O12}4+ cations and (Mo8O26)4– anions.

Synthesis and structural characterization of a new heterometallicmolybdate coordination polymer based on a µ3-bridging amino alcohol

The reaction of Na2MoO4·2H2O with 2-amino-2-(hydroxymethyl)propane-1,3-diol (LH) in water at room temperature results in the formation of the heterometallic coordination polymer [Mo2O6L2(Na2(H2O)4)]·2H2O 1 (L = 2-amino-3-hydroxy-2-(hydroxymethyl)propan-1-olato). The structure of 1 consists of a neutral (Mo2O6) unit located on an inversion center. The Mo atoms exhibit hexa-coordination and are bonded to two terminal and two bridging oxido ligands, an alkoxide oxygen and the amine N atoms of an anionic ligand L– resulting in the formation of an edge-sharing {Mo2O8N2} bioctahedron. The Na+ cations of a centrosymmetric bis(μ2-aqua)-bridged (Na2(H2O)4)2+ unit are penta-coordinated and bonded to two symmetry related L– ligands via the oxygen atoms of their OH groups. The µ3-bridging tetradentate binding mode of L– results in the formation of a two-dimensional heterometallic coordination polymer. The constituents of 1 viz. (Mo2O6), (L)–, (Na2(H2O)4)2+ and lattice water molecules are interlinked with the aid of three varieties of hydrogen bonding interactions. The corresponding tungstate reported recently has been obtained through a similar synthetic protocol and is isostructural.

The role of mono- and dicarboxylic acids in the building of oxomolybdates containing {MoO4}, {Mo2O5}, {Mo2O6}, {Mo3O8}, {Mo5O17}, {Mo5O18}, {Mo8O26}, and {SiMo12O40} units

We describe the impact of mono- and dicarboxylic acids on the formation of polyoxomolybdates of different nuclearities, such as {Mo5O17}, {Mo5O18}, {Mo8O26}, and {SiMo12O40}.

Polyoxometalates in solution: speciation under spotlight

The review covers stability and transformations of classical polyoxometalates in aqueous solutions and provides their ion-distribution diagrams over a wide pH range.

The synthesis, structure and catalytic properties of the [Mo7O24(μ-Mo8O26)Mo7O24]16− anion formed via two intermediate heptamolybdates [Co(en)3]2[NaMo7O24]Cl·nH2O and (H3O)[Co(en)3]2[Mo7O24]Cl·9H2O

Ageing a mixture of sodium molybdate, malonic acid, and tris(ethylenediamine)cobalt(iii) chloride yielded POMs.

Single-Molecule Magnet Behavior of Individual Polyoxometalate Molecules Incorporated within Biopolymer or Metal-Organic Framework Matrices

The chemically and structurally highly stable polyoxometalate (POM) single-molecule magnet (SMM) [(FeW9 O34 )2 Fe4 (H2 O)2 ](10-) (Fe6 W18 ) has been incorporated by direct or post-synthetic approaches into a biopolymer gelatin (Gel) matrix and two crystalline metal-organic frameworks (MOFs), including one diamagnetic (UiO-67) and one magnetic (MIL-101(Cr)). Integrity of the POM in the Fe6 W18 @Gel, Fe6 W18 @UiO-67 and Fe6 W18 @MIL-101(Cr) composites was confirmed by a set of complementary techniques. Magnetic studies indicate that the POMs are magnetically well isolated. Remarkably, in Fe6 W18 @Gel, the SMM properties of the embedded molecules are close to those of the crystals, with clear quantum tunneling steps in the hysteresis loops. For the Fe6 W18 @UiO-67 composite, the molecules retain their SMM properties, the energy barrier being slightly reduced in comparison to the crystalline material and the molecules exhibiting a tunneling rate of magnetization significantly faster than for Fe6 W18 @Gel. When Fe6 W18 is introduced into MIL-101(Cr), the width of the hysteresis loops is drastically reduced and the quantum tunneling steps are smeared out because of the magnetic interactions between the antiferromagnetic matrix and the SMM guest molecules.

Recognition-mediated cucurbit[7]uril-heptamolybdate hybrid material: a facile supramolecular strategy for99mTc separation

Employing a novel cucurbit[7]uril (CB7)-heptamolybdate hybrid material developed as a solid generator bed, we demonstrate an efficient and facile supramolecular strategy to separate the^99mTc nuclide from⁹⁹Mo solution for its use in theranostic applications.