Isolation of a stable lacunary Dawson-type polyoxomolybdate cluster

A polyoxotetradecamolybdate cluster [Mo(14)O(38)(OAc)(6)](2-), which has a lacunary core of the Wells-Dawson structure, is isolated by the reduction of [Mo(6)O(19)](2-). The Mo(14) core is comprised of a mixed valence of [Mo(V)(4)Mo(VI)(10)], exhibiting multi-step reversible redox processes that experience both oxidation and reduction.     

Catalytic properties of the macromolecular polyoxomolybdate cluster in selective oxidation of sulfides

The catalytic properties of the iron-containing Keplerate [H₄Mo₇₂Fe₃₀O₂₅₄(CH₃COO)₁₀-Mo₂O₇(H₂O)H₂Mo₂O₈(H₂O)₃(H₂O)₈₇] • (~80)H₂O (1) in the selective liquid-phase oxidation of thio ethers were studied. Compound 1 shows high catalytic activity and selectivity in the oxidation of organic sulfides to sulfoxides when hydrogen peroxide and tert-butyl hydroperoxide are used as oxidants.     

A novel zigzag chain based on polyoxomolybdate decorated by glycine ligand in covalent bond

An unusual compound, K₂[Mo₄O₁₃(NH₃CH₂COO)₂]?·?2H₂O (1), has been synthesized and structurally characterized by the XRD, elemental analysis, IR spectrum, TG analyses and the single crystal X-ray diffraction. The structure of 1 exhibits a zigzag chain based on corner-shared tetramolybdate chelated by two bidentate glycine ligands.     

Coordination assemblies of polyoxomolybdate cluster framework: from labile building blocks to stable functional materials

Polyoxomolybdates, an important branch in polyoxometalates chemistry, present complicated solution chemistry and unmatched physicochemical properties, which endows us with both great opportunities and considerable challenges in creating new functional materials. This perspective highlights the recent development on the coordination assembly of transition-metal-substituted heteropolymolybdates by using labile lacunary heteropolymolybdates as inorganic multidentate ligands. A series of strategies have been used to stabilize the lacunary heteropolymolybdate building blocks. Finally, we introduce some researches on the modification of polymolybdates by organic groups in aqueous media, which may shed light on the green chemistry of the functionalization of polyoxomolybdates.     

A regioselective Huisgen reaction inside a Keplerate polyoxomolybdate nanoreactor

A 1,3-dipolar cycloaddition reaction taking place quantitatively between propiolic acid "guests" and azide functions previously attached to binding sites within the cavity of a {Mo(132)}-type Keplerate reproducibly gives a 2?:?1 ratio of 1,4- and 1,5-triazoles.     

A novel mass spectrometry cluster for high-throughput quantitative proteomics

We have developed and implemented a novel mass spectrometry (MS) platform combining the advantages of high mass accuracy and resolving power of Fourier transform ion cyclotron resonance (FTICR) with the economy and speed of multiple ion traps for tandem mass spectrometry. The instruments are integrated using novel algorithms and software and work in concert as one system. Using chromatographic time compression, a single expensive FTICR mass spectrometer can match the throughput of multiple relatively inexpensive ion trap instruments. Liquid chromatography (LC)-mass spectrometry data from the two types of spectrometers are aligned and combined to hybrid datasets, from which peptides are identified using accurate mass from the FTICR data and tandem mass spectra from the ion trap data. In addition, the high resolving power and dynamic range of a 12 tesla FTICR also allows precise label-free quantitation. Using two ion traps in parallel with one LC allows simultaneous MS/MS experiments and optimal application of collision induced dissociation and electrontransfer dissociation throughout the chromatographic separation for increased proteome coverage, characterization of post-translational modifications and/or simultaneous measurement in positive and negative ionization mode. An FTICR-ion trap cluster can achieve similar performance and sample throughput as multiple hybrid ion trap-FTICR instruments, but at a lower cost. We here describe the first such FTICR-ion trap cluster, its performance and the idea of chromatographic compression.     

Polymer-assisted formation of giant polyoxomolybdate structures.

A highly ordered, porous nanoscale network structure of polyoxomolybdate was prepared from the slow decomposition of an unstable precursor compound MoO(2)(OH)(OOH) in the presence of PEO-containing triblock copolymer gels or semidilute/concentrated poly(ethylene oxide) (PEO) homopolymer solutions. Small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements of the 1-microm size crystals revealed an extremely ordered primitive cubic (pc) structure made of polyoxomolybdates. Scanning electron microscopy (SEM) measurements showed that the overall size of these single crystals was close to 1 microm, in agreement with estimates from the scattering peak widths. Evidence from both scattering measurements and transmission electron microscope (TEM) measurements suggested that the system formed a highly porous primitive cubic network similar to that of certain zeolite structures. However, the observed lattice constant of 5 nm was much larger. The function of the PEO-containing polymer network was found to be very subtle and complex. Presumably, PEO acted simultaneously as a weak reducing agent and as a viscous matrix to ensure sufficient time for the formation of long-range ordered structures, resulting in the growth of extremely uniform but probably hollow "nanospheres". We suggest that this new material may find unique applications as a high-efficiency absorbent or catalyst. Furthermore, the current synthetic method may open up new pathways to prepare similar functional nanomaterials.     

Directed synthesis of stable large polyoxomolybdate spheres

Polyoxometalates or POMs, a class of inorganic transition metal-oxide based clusters, have gained significant interest owing to their catalytic, magnetic, and material science applications. All such applications require high surface area POM based materials. However, chemically synthesized POMs are still at most in the range of a few nanometers, with their size and morphology being difficult to control. Hence, there is an immediate need to develop design principles that allow easy control of POM morphology and size on mesoscopic (50-500 nm) length scales. Here, we report a design strategy to meet this need. Our method reported here avoids a complex chemical labyrinth by using a prefabricated cationic 1,2-dioleol-3-trimethylammonium-propane (DOTAP) vesicle as a scaffold/structure directing agent and gluing simple anionic heptamolybdates by electrostatic interaction and hydrogen bonds to form large POM spheres. By this method, complexity in the resulting structure can be deliberately induced either via the scaffold or via the oxometalate. The high degree of control in the matter of the size and morphology of the resulting POM superstructures renders this method attractive from a synthetic standpoint.     

A novel one-step synthesis of alkylidyne tricobalt nonacarbonyl cluster complexes from dithioesters

Dithioesters react with dicobalt octacarbonyl in ethanol to afford in one step good yields of various alkylidyne tricobalt nonacarbonyl clusters.     

A novel desorption mechanism of (AgnIn−1)+ cluster ions

Silver iodide clusters have been generated by inert gas condensation technique, ionized via electron impact, and mass analyzed in a reflectron equipped time-of-flight mass spectrometer. The mass spectra are dominated by cluster ions of the composition (Ag_nI_n?1)⁺. Additional kinetic energy analysis is applied to detect metastable decay of the cluster ions for n up to 30. In contrast to alkali halides, where halogen and monomer desorption had been observed, the main decay channel of silver iodide cluster ions is the loss of a neutral trimer Ag₃I₃.     

Capsule formation in novel cadmium cluster metallocavitands

We report the synthesis and characterization of a new heptanuclear cadmium cluster complex formed within a Schiff base macrocycle and study its surprising dimerization in the solid-state and solution to form capsules.     

Formation of novel anionic gold-tin cluster compounds

A straightforward procedure for the formation of mixed metal Au/Sn clusters is presented: reaction of the heteroborate [SnB11H11]2- with phosphine gold electrophiles gave the clusters [Bu3NH]3[{(Et3P)Au(SnB11H11)}3] and [Bu3MeN]4[{(dppm)Au2(SnB11H11)2}2], which were characterised by X-ray diffraction.     

A novel trinuclear zinc(II) cluster with a tetrahedral ZnO4 core

The reaction of 0.67 molar equivalents of the O,N,O′‐tridentate zwitterionic Schiff base (2Z,4E)‐4‐[(2‐hydroxyphenyl)iminio]pent‐2‐en‐2‐olate (H₂L) with one equivalent of zinc(II) acetate in methanol affords a novel trinuclear Zn^II cluster, di‐μ‐acetato‐1:2κ²O:O′;2:3κ²O:O′‐dimethanol‐1κO,3κO‐bis{μ‐2‐[(2E,3Z)‐4‐oxidopent‐3‐en‐2‐ylideneamino]phenolato}‐1:2κ⁴O²,N,O⁴:O⁴;2:3κ⁴O⁴:O²,N,O⁴‐trizinc(II), [Zn₃(C₁₁H₁₁NO₂)₂(C₂H₃O₂)₂(CH₄O)₂], (I), in which two bridging acetate ligands link the terminal square‐based pyramidal Zn^II ions to the approximately tetrahedral Zn^II ion at the core of the cluster. The ZnO₄ coordination group of the central Zn^II ion is established by two bridging phenolate and two bridging acetate O atoms. The remaining four coordination sites of each terminal Zn^II ion are occupied by methanol and deprotonated H₂L. Furthermore, the Zn‐bound methanol hydroxyl groups are involved in complementary hydrogen bonding with the Zn‐bound enolate O atom of a neighbouring molecule, about an inversion centre in each case. The structure of (I) is therefore best described as an extended one‐dimensional hydrogen‐bonded chain of trinuclear Zn^II clusters.     

Self-assembled architecture based on triiron-substituted polyoxomolybdate anion and positively charged polymer

A new self-assembled multilayer architecture was constructed by successive deposition of poly(4-vinylpyridine) partially quaternized with ethylamine (B) and Keggin trilacunary polyoxomolybdate [Aα-PFe₃^III(H₂O)₃Mo₉O₃₇]⁶⁻ (PFe₃Mo₉) on the Au electrode surface, covered with 3-mercapto-1-propanesulfonic acid (MPS). Surface plasmon resonance and cyclic voltammetry measurements were performed at Au/MPS/B/PFe₃Mo₉/B interface in order to investigate the structure and the electrochemical behavior of this electrode. Due to the presence of PFe₃Mo₉, the Au/MPS/B/PFe₃Mo₉/B-modified electrode showed electrocatalytic activity towards H₂O₂ amperometric detection. Additionally, when GOx was deposited as the outermost layer on the abovementioned multilayer structure, the Au/MPS/B/PFe₃Mo₉/B/GOx-modified electrode was able to detect glucose.     

A new class of cluster complexes between group IB metal arylacetylides. Preparation and x-ray structure of a novel tetranuclear gold-silver cluster

The cluster [Au₂Ag₂(C₂Ph)₄(PPh₃)₂)] has been prepared by the reaction of Ph₃PAuC₂Ph with [AgC₂Ph]_n, and by that of Ph₃P with the polymer [AuAg(C₂Ph)₂]_n. The structure of the new cluster involves a linear arrangement of two phenylacetylide groups about each gold atom, with each silver atom asymmetrically π-bonded to two triple bonds and one phosphine ligand.     

Synthesis and structural characterization of the novel cluster compound

Reaction of [Mo3Y(mu-S)3(dtp)4(H2O)] (Y = O, S; dtp = S2P(OC2H5)2(-)) with HgI2 gave the novel compound [[Mo3S7(dtp)3]4 x I][(HgI3)3] x 4H2O (1), which contains a [[Mo3S7(dtp)3]4 x I] tetramer and (HgI3)-. Compound 1 has been characterized by IR, Raman, UV/Vis, and NMR spectroscopy and single-crystal X-ray diffraction analysis. It is shown that this formation process can be referred to as a new cluster reaction. The structure and spectroscopic data of the tetramer is also compared with that of the related discrete cluster [Mo3S7(dtp)3 x I]. Crystal data: space group F23, a = 26.786(3) A, V = 19218.7(4) A3, Z = 4, R = 0.059.     

一维亚微米多钼酸盐形貌可控合成及氧的电催化还原研究

通过调节反应pH值和反应物种实现了一维亚微米多钼酸盐的控制合成,以钼酸铵和十二烷基苯磺酸钠为原料,在pH=6时制备出亚微米线,在pH=2时制备出亚微米棒,而以钼酸铵和氯化钠为原料,在pH=6时制备出纳米带.在pH=6时,纳米材料在长胶束内生长成亚微米线,而pH值降低至2时,过多的H＋不仅会形成大量的Mo3O102-,还会使得胶束变短,因此使得亚微米材料变短,成为亚微米棒.在没有模板剂十二烷基苯磺酸钠时,多钼酸铵就会长成结构更为稳定的纳米带.循环伏安测试结果表明在有机溶剂中,多钼酸盐的亚微米棒对氧电催化还原具有优异活性.研究表明,由于有机醇能与电解质溶液中的H＋反应,因此有机醇能显著促进一维多钼酸盐亚微米材料的氧的电催化活性.     

Probing the self-assembly of inorganic cluster architectures in solution with cryospray mass spectrometry: growth of polyoxomolybdate clusters and polymers mediated by silver(I) ions

Cryospray mass spectrometry (CSI-MS) has been used to probe the mechanism of self-assembly of polyoxometalate clusters in solution. By using CSI-MS and electronic absorbance spectroscopy it was possible to monitor in real-time the self-assembly of polymeric chains based on [Ag 2Mo 8O 26] (2-) n building blocks. The role of the Ag (I) ion in the solution state rearrangement of molybdenum Lindqvist ({Mo 6}) into the silver-linked beta-octamolybdate ({Mo 8}) structure (( n-C 4H 9) 4N) 2 n [Ag 2Mo 8O 26] n ( 1) is revealed in unprecedented detail. A monoanionic series, in particular [AgMo m O 3 m+1 ] (-) where m = 2 to 4, and series involving mixed oxidation state polyoxomolybdate species, which illustrate the in-solution formation of the (Ag{Mo 8}Ag) building blocks, have been observed. CSI-MS detection of species with increasing metal nuclearity concomitant with increasing organic cation contribution supports the hypothesis that the organic cations used in the synthesis play an important structure-directing role in polyoxometalate (POM) growth in solution. A real-time decrease in [{Mo 6}] and associated increase in [{Mo 8}] have been observed using CSI-MS and electronic absorbance spectroscopy, and the rate of {Mo 6} interconversion to {Mo 8} was found to decrease on increasing the size of the countercation. This result can be attributed to the steric bulk of larger organic groups hindering {Mo 6} to {Mo 8} rearrangement and hindering the contact between silver cations and molybdenum anions.     

A new type of cluster and cluster ion source

Combining a magnetron gas discharge with the gas aggregation technique an intense source of clusters has been developed. A large part (up to 80%) of the clusters can be generated as ions without using additional electron impact ionisation.