Spectroscopic studies of molybdenum polyoxometallates with the buckyball structure and polymer-containing compositions based thereon

Molybdenum polyoxometallates with the buckyball structure, ((NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(H₃CCOO)₃₀(H₂O)₇₂] · 30H₃CCOONH₄ · 250H₂O (I), (NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(ClCH₂COO)₃₀(H₂O)₇₂)] · 250H₂O · 15ClCH₂COONa (II), in particular, as parts of polymer-containing compositions were studied by EPR, NMR, IR, and Raman spectroscopy. The structural and chemical aspects responsible for the formation of the observed spectra were considered.     

Another application of (NH4)42[MoVI72MoV60O372(CH3COO)30(H2O)72] as a highly efficient recyclable catalyst for the synthesis of dihydropyrano[3,2‐c]chromenes

In continuation of our previous works on the application of (NH₄)₄₂[Mo^VI₇₂Mo^V₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂], a Keplerate‐type giant‐ball nanoporous isopolyoxomolybdate, as a catalyst for the synthesis of heterocyclic compounds, in this paper, we report another application of this attractive catalyst in the synthesis of 2‐amino‐5‐oxo‐4,5‐dihydropyrano[3,2‐c]chromene‐3‐carbonitriles via a one‐pot three‐component reaction of 4‐hydroxycoumarin, aldehydes and malononitrile. The reactions occur in ethanol–water as solvent at room temperature and the process is operative with various aldehydes, giving the corresponding products in high yields. Other beneficial features of this protocol include short reaction times, simple work‐up and the recyclability and reusability of the catalyst for up to five consecutive runs. Copyright © 2016 John Wiley & Sons, Ltd.     

Cross-linking nanostructured spherical capsules as building units by crystal engineering: related chemistry

The compound [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₀{Mo₂O₇(H₂O)}{H₂Mo₂O₈(H₂O)}₃ (H₂O)₉₁]·ca. 140 H₂O 3≡3a·ca. 140 H₂O, an important educt for an unusual solid state reaction, can now be obtained easily by reacting (NH₄)₄₂[{Mo^V₂O₄(CH₃COO)}₃₀{(Mo)Mo₅O₂₁(H₂O)₆}₁₂]·10 CH₃COONH₄·ca. 300 H₂O 1 with FeCl₃·6 H₂O in water. Interestingly, the freshly precipitated crystals of 3 contain discrete spherical clusters of the type {Mo^VI₇₂Fe^III₃₀} with as yet unprecedented 30×5 unpaired electrons (S=150/2 at room temperature). Upon drying 3, its cluster units 3a get covalently linked to form layers in a step by step solid state reaction, according to the scheme described below, resulting finally in the crystalline reaction product [H₄Mo₇₂Fe₃₀O₂₅₄(CH₃COO)₁₀{Mo₂O₇(H₂O)}{H₂Mo₂O₈(H₂O)}₃(H₂O)₈₇]·ca. 80 H₂O 44a·ca. 80 H₂O. The linking process at the Fe sites follows the well known inorganic condensation process leading to Fe^III polycations in aqueous solution according to the scheme Fe(OH₂)+(H₂O)Fe Fe(OH)+(H₂O)Fe Fe–O–Fe and thus is based on a type of crystal engineering with nanostructured spherical building blocks. This process does not allow chaotic characteristics in contrast to the mentioned polycation formation. Careful investigation leads to the identification of an intermediate 5 containing clusters 5a — with the same cluster composition as 3a and 4a — in the closest possible non-covalent contact. The related materials are of tremendous interest for magnetochemistry (nano-magneto-technology).

     

Crystal Structure and EPR Spectra of cis—Dioxo—molybdenum（V） Complex with o—Aminophenol

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Acetate-Functionalized Zirconium-Substituted Tungstogermanate, [Zr4O2(OH)2(CH3COO)2(α-GeW10O37)2]12−

The two acetate-functionalized zirconium(IV)-substituted tungstogermanates, Na₈K₄[Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂] · 33H₂O and Na₈Cs₄[Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂] · 32H₂O, were synthesized by the reaction of ZrOCl₂ with [A-α-GeW₉O₃₄]¹⁰⁻ in pH = 4.8 buffer and their structures were determined by single-crystal X-ray analysis. Both of them contain a centrosymmetric polyanion [Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂]¹²⁻ consisting of two {α-GeW₁₀O₃₇} units sandwiching an inorganic–organic hybrid {Zr₄O₂(OH)₂(CH₃COO)₂} cluster. The polyanion contains a mixing of seven- and eight-coordinate Zr centres. The two compounds were also characterized by elemental analysis, IR spectroscopy, UV–vis and TG–DSC analysis.     

Thermochemical charge generation in polymer-salt films as a function of temperature

Potential was studied as a function of temperature during charge generation in poly(vinyl alcohol) films containing ammonium heptamolybdate, copper nitrate, and polyoxometalate (NH₄)₄₂[Mo ₇₂ ^VI Mo ₆₀ ^V O₃₇₂(HCOO)₃₀(H₂O)₇₂] · 30HCOONH₄ · 250H₂O. The range of the strongest charge generation and its bounds were determined. The results are matched to thermal analysis data. Charge generation correlates with evolution of volatiles from the films.     

Synthesis,Structure and Characterization of Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo₂^VO₃L₂] [L = thiosemicarbazonato ligand: C₆H₄(O)CH:NN:C(S)NHR′ and C₁₀H₆(O)CH:NN:C(S)NHR′; R′ = H, CH₃, C₆H₅) were obtained either by oxygen atom abstraction from Mo^VIO₂L with triphenylphosphine or by using [Mo₂O₃(acac)₄] in the reaction with the corresponding ligands H₂L. Crystal and molecular structure of [Mo₂O₃{C₆H₄(O)CH:NN:C(S)NHC₆H₅}₂] · CH₃CN has been determined by the single‐crystal X‐ray diffraction method.     

Keplerate巨型纳米多孔聚氧钼酸盐作为可重复使用催化剂用于合成1,2,4,5-四取代咪唑(英文)

The Keplerate‐type giant nanoporous isopolyoxomolybdate (NH4)42[MoVI72MoV60O372‐(CH3COO)30(H2O)72], denoted {Mo132}, has been used as a catalyst for the synthesis of1,2,4,5‐tetrasubstituted imidazoles by the one‐pot, four‐component thermal reaction of benzil with aromatic aldehydes, primary amines, and ammonium acetate under solvent‐free conditions. The catalyst was prepared according to a previously published literature procedure using inexpensive and readily available starting materials, and subsequently characterized by FT‐IR, UV and X‐ray diffraction spectroscopy, as well as microanalysis. The results showed that {Mo132} exhibited high catalytic activity towards the synthesis of 1,2,4,5‐tetrasubstituted imidazoles, with the desired products being formed in good to high yields. Furthermore, the catalyst was recyclable and could be reused at least three times without any discernible loss in its catalytic activity. Overall, this new catalytic method for the synthesis of 1,2,4,5‐tetrasubstituted imidazoles provides rapid access to the desired compounds following a simple work‐up procedure, and avoids the use of harmful organic solvents. This method therefore represents a significant improvement over the methods currently available for the synthesis of tetrasubstituted imidazoles.     

Thermal behavior of polyoxometalate Mo132

Thermal destruction of (NH₄)₄₂[Mo ₇₂ ^VI Mo ₆₀ ^V O₃₇₂(H₃CCOO)₃₀(H₂O)₇₂]30H₃CCOONH₄ · 250H₂O, polyoxometalate Mo132, was analyzed. Differential scanning calorimetry (DSC) and mass spectrometry were investigative tools. Thermal destruction occurs in air and in nitrogen in three main stages. First, water is eliminated. The thermolysis products at higher temperatures include acetamide and acetonitrile. Molybdenum oxides are formed in solid products through an amorphous stage. The utility of NMR spectroscopy for analyzing poly(oxometalates) is demonstrated.     

Experimental and theoretical study of <Superscript>13</Superscript>C shielding tensors in new-style molybdenum complex

¹³C 2D-PASS spectra of two new cis-dioxo catecholatomolybdenum complexes (NH₂CH₂NH₂CHCH₂)₂(H⁺)₃[Mo^vO ₂(C₆H₄O₂)₂] and (NH₂CH₂CH₂CH₂NH₂)₂(H⁺)₃[Mo^(v)O₂ (C₂H₂O₂)₂] have been obtained by solid-state nuclear magnetic resonance (NMR), in which the spinning sidebands were well-separated. The principal components of the ¹³C shielding tensors were extracted by theoretically fitting the intensities of ¹³C spinning sidebands. The effects of counter cations on ¹³C chemical shift isotropy and shielding tensor of cis-dioxo catecholatomolybdenum complex anion [Mo ^(v)O₂(C₆H₄O₂)₂]³⁻ were studied, comparing the ¹³C CSA of those carbon sites in complex anions with that of the counter cations. Based on the known structure of the molybdenum complex crystal, theoretical values of ¹³C shielding tensors were calculated by the ainitio GIAO method, in comparison with the experimental results.     

Characterization of tetra,dodeca and tetradeca MoV polyoxometalate wheels structured by etidronate ligands

The reactivity of the [Mo^V₂O₄]²⁺ dinuclear unit with the [O₃P(C(CH₃)(OH))PO₃]^4? etidronate ligand has been investigated. Three complexes have been isolated and characterized by IR spectroscopy, elemental analysis and single crystal X-Ray diffraction studies. Structural determination of the tetranuclear compound (CN₃H₆)₆[(Mo^V₂O₄)₂(O₃P(C(CH₃)O)PO₃)₂]·12H₂O (1) revealed that the hydroxo group of the etidronate ligand can be deprotonated in presence of Mo^V even in acidic media. It follows that its coordination mode thus differs from that of the methylenediphosphonate ligand [O₃P(CH₂)PO3]4?, which reactivity with Mo^V has been previously widely studied. In contrast, no such deprotonation of the hydroxo group is observed in the (NH₄)₁₈[(Mo^V₂O₄)₆(OH)₆(O₃P(C(CH₃)(OH))PO₃)₆]·35H₂O complex 2. This species contains a dodecanuclear core analogous to the one previously found in the [(Mo^V₂O₄)₆(OH)₆(O₃PCH₂PO₃)₆]^18? methylenediphosphonato polyanion. In 2, six interconnected {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)} units form a cyclohexane-like ring in a chair conformation. In the (CN₃H₆)₁₈Na₃[(Mo^V₂O₄)₇(O₃P(C(CH₃)(OH))PO₃)₇(CH₃COO)₇]·5CH₃COONa 52H₂O compound 3, seven {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)(CH₃COO)} units are connected, forming an almost planar tetradecanuclear wheel. This compound represents the largest homometallic Mo^V polyoxometalate cyclic system reported to date. Finally, ³¹P NMR studies revealed that only complex 1 is stable in aqueous solution.     

Self‐Recognition Between Two Almost Identical Macroions During Their Assembly: The Effects of pH and Temperature

Two Keplerate‐type macroions, [Mo^VI₇₂Fe^III₃₀O₂₅₂‐ (CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁]?ca. 150 H₂O= {Mo₇₂Fe₃₀} and [{Na(H₂O)₁₂}?{Mo^VI₇₂Cr^III₃₀O₂₅₂(CH₃COO)₁₉‐ (H₂O)₉₄}]?ca. 120 H₂O= {Mo₇₂Cr₃₀} , with identical size and shape but different charge density, can self‐assemble into spherical “blackberry”‐like structures in aqueous solution by means of electrostatic interactions. These two macroanions can self‐recognize each other and self‐assemble into two separate types of homogeneous blackberries in their mixed dilute aqueous solution, in which they carry ?7 and ?5 net charges, respectively. Either adjusting the solution pH or raising temperature is expected to make the self‐recognition more difficult, by making the charge densities of the two clusters closer, or by decreasing the activation energy barrier for the blackberry formation, respectively. Amazingly, the self‐recognition behavior remains, as confirmed by dynamic and static light scattering, TEM, and energy dispersive spectroscopy techniques. The results prove that the self‐recognition behavior of the macroions due to the long‐range electrostatic interaction is universal and can be achieved when only minimum differences exist between two types of macroanions.     

The Reaction of Molybdenum with 2,3-Dihydroxynaphthalene

[H2N（CH2）3NH312[MoO2（C10H6O2）2] （1） was synthesized by the 2,3-dihydroxynaphthalene in the mixed solvent of CH3OH, CH3CN reaction of （n-Bu4N）4[Mo8O26] with and 1,3-propanediarnine. （C5HllN2）2- [HeN（CH2）3NH2][MoO2（CloH6O2）2] （2） was obtained by the reaction of Na2MoO4.2H20 with 2,3-dihydroxynaphthalene in the same solvent above. Both of the complexes possess complex anion [Mo（VI）O2（OC10H6O）2]^2- which shows pseudo-octahedrally coordinated fashion, while the counterions are two protonated 1,3-propanediamine in complex 1 and （CsH11N2）^＋ in complex 2. （C5H11N2）＋ is the byproduct of reaction 2, which results from combination of acetonitrile with 1,3-propanediamine. Packing diagrams of the two complexes are also different. There is anti-parallel-aligned-double-meso-bilayer unit in complex 1. However there are four chiral anions arranged in anticlockwise orientation in complex 2.     

Molybdenum Bisphosphonates with Cr(III) or Mn(III) Ions

The synthesis of Mo^VI bisphosphonates (BPs) complexes in the presence of a heterometallic element has been studied. Two different BPs have been used, the alendronate ligand, [O₃PC(C₃H₆NH₃)(O)PO₃]^4? (Ale) and a new BP derivative with a pyridine ring linked to the amino group, [O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃]^4? (AlePy). Three compounds have been isolated, a tetranuclear Mo^VI complex with Cr^III ions, (NH₄)₅[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Cr]·11H₂O (Mo₄(Ale)₂Cr), its Mn^III analogue, (NH₄)_4.5Na_0.5[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Mn]·9H₂O (Mo₄(Ale)₂Mn), and a cocrystal of two polyoxomolybdates, (NH₄)₁₀Na₃[(Mo₂O₆)₂(O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃)₂Cr]₂[CrMo₆(OH)₆O₁₈]·37H₂O ([Mo₄(AlePy)₂Cr]₂[CrMo₆]). In this latter compound an Anderson-type POM [CrMo₆(OH)₆O₁₈]^3? is sandwiched between two tetranuclear Mo^VI complexes with AlePy ligands. The protonated triply bridging oxygen atoms bound to the central Cr^III ion of the Anderson anion develop strong hydrogen bonding interactions with the oxygen atoms of the bisphosphonate complexes. The UV–Vis spectra confirm the coexistence in solution of both POMs. Cyclic voltammetry experiments have been performed, showing the reduction of the Mo centers. In strong contrast with the reported Mo^VI BP systems, the presence of trivalent cations in close proximity to the Mo^VI centers dramatically impact the potential solid-state photochromic properties of these compounds.     

The kinetics of photochemical processes in polymer-salt systems

The kinetics of photochemical reactions in aqueous polymer-salt systems containing ammonium heptamolybdate, dodecatungstate, or metavanadate and polyvinyl alcohol or polyvinylpyrrolidone was studied by measurements of photoinduced electrode potential difference. The rate of primary accumulation of reduced d metal forms was evaluated for different systems. Possible reasons for complex oscillatory processes in the systems were analyzed. Comparative data were obtained for compositions containing polyoxometallate shaped like buckyball:(NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(HCOO)₃₀(H₂O)₇₂] · 30HCOONH₄ · 250H₂O. UV irradiation of this system caused the oxidation of molybdenum(V). Original Russian Text ? A.A. Ostroushko, M.Yu. Sennikov, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 1, pp. 127–131.     

Novel Three-Dimensional Coordination Polymers Based on [Mo6Se8(CN)6]7− Anions and Mn2+ Cations

Three novel coordination polymers K₅[MnMo₆Se₈(CN)₆] · 8H₂O (1), (Me₄N)₄[{Mn(H₂O)₂}_1.5Mo₆Se₈(CN)₆] · 4H₂O (2), and K₃[{Mn₂(H₂O)₄}Mo₆Se₈(CN)₆] · 7H₂O (3) have been synthesized by layering of a methanol solution of [Mn(salen)]CH₃COO (salen–N,N′-bis(salicylidene)ethylenediamine) on an aqueous solution of K₇[Mo₆Se₈(CN)₆] · 8H₂O. The compounds have been characterized by single-crystal X-ray diffraction analysis. All structures are based on negatively charged porous polymer frameworks where CN groups of [Mo₆Se₈(CN)₆]⁷⁻ cluster complexes are coordinated to Mn²⁺ cations. Cavities in the frameworks are filled by additional cations and solvate water molecules.     

New data for molybdenum polyoxometallate with the buckyball structure containing acetate groups and compositions based thereon

Synthesis and characterization of the polyoxometallate (NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(H₃CCOO)₃₀(H₂O)₇₂]30H₃CCOONH₄ · 250H₂O (Mo132) with the buckyball structure were carried out. New crystallographic data were obtained. Stability of Mo132 was studied as a function of external factors, acidity, concentration of the solution, and the presence of a polymeric component. The composition of the most stable complexes of buckyballs with polymers was confirmed. The aggregation of buckyballs in the presence of polyvinylpyrrolidone were studied. Thermochemical studies of Mo132 interaction with polyvinyl alcohol in films were carried out. Electromigration of polymer-salt complexes in solutions was established, the possibility of change of the sign of associates upon interaction of Mo132 anions with lanthanum cations was confirmed.     

Deep desulfurization of diesel by selective oxidation using amphiphilic paradodecatungstate catalyst

An amphiphilic paradodecatungstate catalyst, [(C₁₈H₃₇)₂N(CH₃)₂]₉[NaH₂W₁₂O₄₂] was prepared and characterized by Fourier transform infrared spectroscopy, UV–visible spectrum, differential thermal analysis, and thermogravimetric analysis. The amphiphilic catalyst exhibits very high catalytic activity that dibenzothiophene (DBT) in model diesel can be oxidized into dibenzothiophene sulfones using hydrogen peroxide as an oxidant. The reactivity of sulfur compounds decreased in the order of DBT > 4,6-DMDBT > BT > 5-MBT. The reaction rates of these sulfur compounds are sensitive to the electron density on sulfur atoms and the steric hindrance of the substituted groups of sulfur compounds. The sulfur level of a commercial diesel after desulfurization can drop from 200 ppm to about 12 ppm.     

Association of Spherical Porous Nanocluster Keplerate-Type Polyoxometalate Mo<Subscript>72</Subscript>Fe<Subscript>30</Subscript> with Biologically Active Substances

The peculiarities of formation of ionic associates of the spherical porous nanocluster polyoxometalate [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁] ~ 150H₂O with biologically active substances, in particular, thiamine chloride using the methods of UV/Vis spectroscopy, pH-metry, laser light scattering (the measurement of Zeta potential and particle size distribution), Raman spectroscopy, infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy has been studied. The location of thiamine molecules on POM’s surface is given. The solubility product of associate was estimated. The formation of molecular associates of polyoxometalate with insulin, albumin has been shown. Using the meglumine acridonacetate the influence of complexing agents on the possibility of obtaining associates on the basis of [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁] ~ 150H₂O has been studied.     

New girdle‐like Mo18 polyanions linked into chains

From the reduction of heptamolybdate, a polyoxomolybdate was obtained with the formula [Na(H₂O)₁₆(NH₂CH₂­COO)]⁴⁺·{Na⁺[H₉MoMoO₅₆(NH₂CH₂COO)]^5?}^4?­·20H₂O, i.e. hepta­sodium nona­hydrogen tetra­car­bam­ate hexa­deca­aqua­hexa­penta­conta­oxa­octa­deca­molyb­date(V,VI) icosa­hydrate. The 18 Mo atoms are connected by bridging O atoms to form a centrosymmetric girdle‐like structure, in which Mo^V–Mo^V units are found. An Na⁺ cation occupies the central hole of the girdle, while four Na⁺ cations are bonded to the O atoms on the girdle edge. The girdles are linked into a one‐dimensional chain by the other Na⁺ cations.