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1.
A new three-dimensional (3D) organic–inorganic hybrid compound based on the Wells–Dawson POMs modified by Ag(I) ions and bpe (bpe = bis(4-pyridyl)ethylene) molecules, {[Ag(C 12N 2H 10)] 3(H 3P 2W 18O 62)}·(C 12N 2H 10)·4H 2O, has been synthesized under hydrothermal condition and structurally characterized. Crystal data for the title compound: C 48H 51Ag 3N 8O 66P 2W 18, monoclinic, space group P2 1/m, a = 13.623(5) Å, b = 25.345(5) Å, c = 13.858(5) Å, α = 90°, β = 98.038(5)°, γ = 90°, V = 4738(3) Å 3. It represents an important example of the family of Wells–Dawson POMs modified by M–N chains, in which Wells–Dawson POMs covalently link eight transitional metal complex fragments and represent the highest track number (8) of M–N chains modifying Wells–Dawson POMs. Furthermore, the electrochemical properties of the title compound were studied. 相似文献
2.
A series of tris(hydroxymethyl)aminomethane (TRIS)‐based linear (bis(TRIS)) and triangular (tris(TRIS)) ligands has been synthesised and were covalently attached to the Wells–Dawson type cluster [P 2V 3W 15O 62] 9? to generate a series of nanometer‐sized inorganic–organic hybrid polyoxometalate clusters. These huge hybrids, with a molecular mass similar to that of small proteins in the range of ≈10–16 kDa, were unambiguously characterised by using high‐resolution ESI‐MS. The ESI‐MS spectra of these compounds revealed, in negative ion mode, a characteristic pattern showing distinct groups of peaks corresponding to different anionic charge states ranging from 3 ? to 8 ? for the hybrids. Each peak in these individual groups could be unambiguously assigned to the corresponding hybrid cluster anion with varying combinations of tetrabutylammonium (TBA) and other cations. This study therefore highlights the prowess of the high‐resolution ESI‐MS for the unambiguous characterisation of large, nanoscale, inorganic–organic hybrid clusters that have huge mass, of the order of 10–16 kDa. Also, the designed synthesis of these compounds points to the fact that we were able to achieve a great deal of structural pre‐design in the synthesis of these inorganic–organic hybrid polyoxometalates (POMs) by means of a ligand design route, which is often not possible in traditional “one‐pot” POM synthesis. 相似文献
3.
In this study, we synthesized hybrid materials using well-Dawson polyoxometalates (POMs), K 7[H 4PW 18O 62]·18H 2O or K 6[P 2W 18O 62]·13H 2O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4]). K, W, P and CHN elemental analysis showed that one mole of [H 4PW 18O 62] 7− reacts with 6 moles of BMIM + and one mole of [P 2W 18O 62] 6− reacts with 4 moles of BMIM + to form, respectively, K[BMIM] 6H 4PW 18O 62 and K 2[BMIM] 4P 2W 18O 62. X-ray diffraction illustrated amorphous structure of the hybrid materials. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid materials compared to the parents Dawson POMs. Cyclic voltammetry showed that the reduction peak potentials of the Dawson anion in the hybrid materials shift towards negative values and the shift is more pronounced for K[BMIM] 6H 4PW 18O 62 compared to K 2[BMIM] 4P 2W 18O 62. This was attributed to a decrease in the acidity of the Dawson POM anion in the hybrid material. 相似文献
4.
We report the synthesis of the first organo‐POM with thermoresponsive properties. Our concept will provide chemists with a new tool to design POMs whose solubility is reversibly controllable through an external stimulus. POM–polymer TBA 7[POM]‐poly( N,N‐diethylacrylamide) (POM–PDEAAm), was prepared by grafting PDEAAm‐NH 2 (obtained by RAFT polymerization) onto the activated Dawson acyl‐POM, α 2‐[P 2W 17O 61SnCH 2CH 2C(?O)] 6?. Extensive MS analysis was used to monitor the chain‐functionalization steps and to confirm the formation of the hybrid. Aqueous solutions of the (NH 4) 7[POM–PDEAAm] exhibited a LCST of 38 °C. Thus, the solubility/aggregation of the hybrid was reversibly controlled by changing the temperature. Above 38 °C, the solution became cloudy, and cleared again upon cooling. Dynamic light scattering (DLS) revealed the formation of small aggregates in the range 100 nm. We assumed that the charged POM head units prevented the formation of the larger‐scattering aggregates that are usually observed for PDEAAm, and promoted the formation of micelle‐like structures. The conjugate exhibited a temperature transition, which was different from that of the polymer and depended on the counterions associated with the POM. This result demonstrates the potential for merging organic (in this case, polymer) and inorganic structures to afford materials that exhibit new properties. 相似文献
5.
A mono‐cobalt substituted Wells–Dawson polyoxometalate with an antenna ligand linked to the Co II atom, was prepared by reaction of the mono‐vacant Wells–Dawson precursor [P 2W 17O 61] 10– with a imidazole‐cobalt complex by using the bench method. It was isolated as the imidazole salt: (HIm) 7H[P 2W 17O 61Co(Im)] · 4H 2O ( 1 ) (Im = imidazole). Compound 1 was characterized by elemental analysis, IR and UV/Vis spectroscopy, TG analysis, cyclic voltammetry and single‐crystal/powder X‐ray diffraction. This is the first example of the 3d transition metal mono‐substituted Wells–Dawson polyoxometalate with an antenna ligand. 相似文献
6.
Solutions of the quaternary ammonium salts of a set of classic polyoxometalates (POMs) (Keggin [XM 12O 40] n–, Dawson [P 2W 18O 62] 6–, and Lindqvist [M 6O 19] 2– (X = P, Si; M = W, Mo) were characterized by electrospray mass spectrometry. The gas-phase fragmentations of a series of quaternary ammonium-associated clusters were investigated by their collision-induced dissociations to elucidate their fragmentation mechanisms. It was found that the quaternary ammonium-associated clusters had distinctive dissociation characteristics. Moreover, the mono-quaternary ammonium-associated clusters, {NR 4[POMs]} (n-1)–, shared a common fragmentation feature, that is, they decomposed exclusively into their respective alkyl cation-bound clusters irrespective of the different cation sizes and the different natures of the polyoxoanions. The optimized geometries and the binding energies of the mono cation-bound Lindqvist POM-based clusters were obtained by calculations. To the best of our knowledge, this is the first investigation of the gas-phase fragmentations of these noncovalent complexes between organic amines and inorganic POM anions by a combination of theory and mass spectrometry. Figure
7.
Two new polyoxometalate (POM)‐based hybrid monomers (Bu 4N) 5(H)[P 2V 3W 15O 59{(OCH 2) 3CNHCO(CH 3)C?CH 2}] ( 2 ) and (S(CH 3) 2C 6H 4OCOC(CH 3)=CH 2) 6[PVMo 10O 40] ( 5 ) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells–Dawson and Keggin‐type clusters and were characterized by analytical and spectroscopic techniques including ESI‐MS and/or single‐crystal X‐ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by 1H, 31P NMR and IR spectroscopic techniques, gel‐permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E‐beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source. 相似文献
8.
A new [Cu2bix2] sub-ring modifying Wells–Dawson polyoxometalates (POMs) compound containing, H10[Cu(bix)2(P2W18O62)2](bix)6·16H2O (CubixP2W18) (bix?=?1,4-bis(imidazol-1-ylmethyl)benzene), has been synthesized, characterized and studied as electrochemical biosensor for detecting uric acid (UA) for the first time in the work. Interesting is that CubixP2W18 contain fascinating left- and right-helical chain. Moreover, the CubixP2W18 modified glassy carbon electrodes (GCE) shows excellent electrochemical activities and higher selectivity and stabilization toward UA. The linear response range is from 2.5?×?10?7 M to 6.79?×?10?4 M and the lower detection limit is as low as 4.97?×?10?7 M (S/N?=?3). The strategy of employing Wells–Dawson POMs-based sensors provides a new pathway to design new sensor for detecting UA in the field of sensor and medical diagnosis. 相似文献
9.
Three novel hexa‐Ni‐substituted Dawson phosphortungstates [Ni 6(en) 3(H 2O) 6(μ 3‐OH) 3(H 3P 2W 15O 56)] ? 14 H 2O ( 1 ), [Ni(enMe) 2(H 2O)][Ni 6(enMe) 3(μ 3‐OH) 3(H 2O) 6(HP 2W 15O 56)] ? 10 H 2O ( 2 ), and [Ni(enMe) 2] 3[Ni(enMe) 2(H 2O)][Ni(enMe)(H 2O) 2][Ni 6(enMe) 3(μ 3‐OH) 3(Ac) 2(H 2O)(P 2W 15O 56)] 2 ? 6 H 2O ( 3 ) (en=ethylenediamine, enMe=1, 2‐diaminopropane, Ac=CH 3COO ?) have been made under hydrothermal conditions and were characterized by IR spectroscopy, elemental analysis, diffuse reflectance spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The common structural features of compounds 1 – 3 contain the similar hexa‐Ni‐substituted Dawson polyoxometalate (POM) units that can be viewed as a [Ni 6(μ 3‐OH) 3] 9+ cluster capping on a [P 2W 15O 56] 12? fragment. Compounds 1 and 2 are two isolated clusters, whereas compound 3 is the first 3D POM framework constructed from hexa‐Ni‐substituted Dawson POM units and Ni(enMe) complex bridges. The preparations of compounds 1 – 3 not only indicate that triangle coplanar Ni 6 clusters are very stable fragments in both trivacant Keggin and trivacant Dawson POM systems, but also offer that the hydrothermal technique can act as an effective strategy for making novel Dawson‐type high‐nuclear transition‐metal cluster substituted POMs by combination of lacunary Dawson precusors with transition‐metal cations in the tunable role of organic ligands. In addition, magnetic measurements illustrate that there exist overall ferromagnetic interactions in compound 3 . 相似文献
10.
An inorganic‐organic hybrid solid (H 6/5bppy) 5[P 2W 18O 62]·4.5H 2O ( 1 ) (bppy = 4‐(5‐(4‐bromophenyl)pyridin‐2‐yl)pyridine) was hydrothermally synthesized by using pre‐constructed Wells‐Dawson type salt α‐K 6P 2W 18O 62·15H 2O as inorganic moiety. The crystal structure keeps integrated and steady under the interactions together of aryl packing, hydrogen bonding and halogen bonding. X‐ray single crystal structure analysis reveals that compound 1 contains cavities with the sizes of about 6 × 8Å, in which H 2O molecules are captured. The hybrid was used as a solid bulk modifier to fabricate a three‐dimensional bulk‐modified carbon paste electrode ( 1 ‐CPE) by direct mixing. The electrochemical and electrocatalytic behavior of the 1 ‐CPE has been studied in detail. The results exhibit that the redox ability of the Wells‐Dawson polyanions can be maintained in the hybrid solid, which has a good electrocatalytic activity toward the reduction of bromate and hydrogen peroxide. A hydrodynamic voltammetric experiment was performed to characterize the electrode as an amperometric sensor for the determination of hydrogen peroxide. The 1 ‐CPE showed long‐term stability and excellent reproducibility of surface renewal. 相似文献
11.
Al‐ and Ga‐containing open‐Dawson polyoxometalates (POMs), K 10[{Al 4(μ‐OH) 6}{α,α‐Si 2W 18O 66}] · 28.5H 2O ( Al 4 ‐ open ) and K 10[{Ga 4(μ‐OH) 6}(α,α‐Si 2W 18O 66)] · 25H 2O ( Ga 4 ‐ open ) were synthesized by the reaction of trilacunary Keggin POM, [A‐α‐SiW 9O 34] 10–, with Al(NO 3) 3 · 9H 2O or Ga(NO 3) 3 · nH 2O, and unequivocally characterized by single‐crystal X‐ray analysis, 29Si and 183W NMR, and FT‐IR spectroscopy as well as elemental analysis and TG/DTA. Single‐crystal X‐ray analysis revealed that the { M4(μ‐OH) 6} 6+ ( M = Al, Ga) clusters were included in an open pocket of the open‐Dawson polyanion, [α,α‐Si 2W 18O 66] 16–, which was constituted by the fusion of two trilacunary Keggin POMs via two W–O–W bonds. These two open‐Dawson structural POMs showed clear difference of the bite angles depending on the size of ionic radii. In cases of both compounds, the solution 29Si and 183W NMR spectra in D 2O showed only one signal and five signals, respectively. These spectra were consistent with the molecular structures of Al 4 ‐ and Ga 4 ‐ open , suggesting that these polyoxoanions were obtained as single species and maintained their molecular structures in solution. 相似文献
12.
The tri-rhenium(VI) capped Wells–Dawson polyoxometalate, [Re 3P 2W 15O 62] 6– with quaternary ammonium cations was synthesized by reacting the trivacant lacunary species, [P 2W 15O 56] 12– with [ReOCl 3(PPh 3) 2] in an organic solvent. Elemental analysis by thermogravimetry and inductively coupled plasma mass spectroctrometry confirmed the substitution of three rhenium atoms, single-crystal X-ray diffraction as well as infra red spectroscopy showed the complete Wells–Dawson structure. The presence of all three rhenium atoms in one cap is indicated by 31P nuclear magnetic resonance spectroscopy and the electron spin resonance spectrum shows that the tri-rhenium(V) species with three unpaired electrons is low spin, S = ½. 相似文献
13.
A new inorganic-organic hybrid, [Zn(phen) 2(ppy)][{Zn(phen) 2}{Zn(phen) 2(H 2O)}{P 2W 18O 62}]?·?2H 2O (phen?=?1,10′-phenanthroline, ppy?=?2-(5-phenylpyridin-2-yl)pyridine) ( 1), by using pre-prepared Wells–Dawson salt α-K 6P 2W 18O 62?·?15H 2O as precursor, has been synthesized under hydrothermal conditions. Compound 1 was characterized by single-crystal X-ray diffraction, elemental analyses, IR spectrum and cyclic voltammetry. Yellow crystals crystallized in the monoclinic space group P2 (1)/ c with a?=?16.2450(11)?Å, b?=?17.0918(11)?Å, c?=?43.640(3)?Å, β?=?92.0060(10)°, V?=?12109.4(14)?Å 3, Z?=?4. The title compound represents a novel zero-dimensional structure based on bisupporting Wells–Dawson POM: one terminal oxygen atom located in the “belt” site and another located in the “cap” site of the same hemisphere of the polyanion are coordinated by Zn 2+ cations. Compound 1 also contains the isolated secondary metal complex [Zn(phen) 2(ppy)] 2+ with two different organic ligands phen and ppy. 相似文献
14.
A novel Wells–Dawson heteropolyacid-based magnetic Inorganic–organic nanohybrid, Fe 3O 4@SiO 2@ADMPT/H 6P 2W 18O 62, was fabricated and used as a green, efficient, eco-friendly, and highly recyclable catalyst for the one-pot and multi-component synthesis of 1,4-Dihydopyridine (1,4-DHP) derivatives from the reaction of various aromatic aldehydes with ethyl acetoacetate and ammonium acetate with good to excellent yields and in a short span of time. The nanohybrid catalyst was prepared by the chemical anchoring of Wells–Dawson heteropolyacid H 6P 2W 18O 62 onto the surface of functionalized Fe 3O 4 nanoparticles with 2,4-bis(3,5-dimethylpyrazol)-triazine (ADMPT) linker. These nanocatalysts were identified by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM). This protocol is developed as a safe, cost-effective and convenient alternate method for the synthesis of 1,4-DHP derivatives utilizing an eco-friendly, and a highly reusable catalyst. 相似文献
15.
Three new organic–inorganic hybrid materials based on two important heteropolyoxometalates namely Preyssler (=K 12.5H 1.5[Na(H 2O)P 5W 30O 110]·35H 2O) and Wells–Dawson (=K 6[P 2W 18O 62]·10H 2O) anions, namely, (Hpro) 9(Hleu) 3K 2[Na(H 2O)P 5W 30O 110]·25H 2O ( 1), (Hpro) 4(Hasp)[HP 2W 18O 62]·20H 2O ( 2), and (Hpro) 11K 3[Na(H 2O)P 5W 30O 110]·18H 2O ( 3) where pro, leu, and asp are proline, leucine, and asparagine, respectively, were prepared and identified by elemental analysis, infrared and proton nuclear magnetic resonance spectroscopies, and thermogravimetric analysis. The hybrid materials are made up of positively charged amino acids, [Na(H 2O)P 5W 30O 110] 14? and [P 2W 18O 62] 6? anions, and H 2O molecules of crystallization. These constituents’ fragments held together into a three-dimensional supermolecular network through non-covalent interactions. The protonation constants of the amino acids used, and Preyssler and Wells–Dawson species in all possible protonated forms, the equilibrium constants for binary systems of proline–asparagine and proline–leucine, and the stoichiometry and stability constants of the corresponding binary and ternary hybrids with Preyssler and Wells–Dawson heteropolyoxometalates in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most hybrid species in solution were compared with the corresponding hybrids in the solid phase, in detail. 相似文献
16.
The design of structurally well‐defined anionic molecular metal–oxygen clusters, polyoxometalates (POMs), leads to inorganic receptors with unique and tunable properties. Herein, an α‐Dawson‐type silicotungstate, TBA 8[α‐Si 2W 18O 62] ? 3 H 2O ( II ) that possesses a ?8 charge was successfully synthesized by dimerization of a trivacant lacunary α‐Keggin‐type silicotungstate TBA 4H 6[α‐SiW 9O 34] ? 2 H 2O ( I ) in an organic solvent. POM II could be reversibly protonated (in the presence of acid) and deprotonated (in the presence of base) inside the aperture by means of intramolecular hydrogen bonds with retention of the POM structure. In contrast, the aperture of phosphorus‐centered POM TBA 6[α‐P 2W 18O 62]?H 2O ( III ) was not protonated inside the aperture. The density functional theory (DFT) calculations revealed that the basicities and charges of internal μ 3‐oxygen atoms were increased by changing the central heteroatoms from P 5+ to Si 4+, thereby supporting the protonation of II . Additionally, II showed much higher catalytic performance for the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde than I and III . 相似文献
17.
A Wells‐Dawson Polyoxometalate‐based hybrid, Ag 9(trz) 3(Htrz) 4 (H 2O)(P 2W 18O 62)·3H 2O ( 1 ) (Htrz = 1,2,4‐1H‐triazole) was hydrothermally synthesized through using trz ligand and silver nitrate in the presence of [P 2W 18O 62] 6– polyoxoanion. In the 3D framework structure of compound 1 , two kinds of wave‐like Ag/trz chains originated from trz ligands and silver cations are aggregated in a “2+1” mode by {Ag 2/trz} linkages to result in a 1D Ag/trz metal‐organic ribbon, which is further extended into a 3D framework structure by [P 2W 18O 62] 6– polyoxoanions through Ag‐O covalent bonds. Additionally, the electrochemical properties of compound 1 have also been investigated. 相似文献
18.
We induce and study reactions of polyoxometalate (POM) molecules, [PW 12O 40] 3− (Keggin) and [P 2W 18O 62] 6− (Wells–Dawson), at the single-molecule level. Several identical carbon nanotubes aligned side by side within a bundle provided a platform for spatiotemporally resolved imaging of ca. 100 molecules encapsulated within the nanotubes by transmission electron microscopy (TEM). Due to the entrapment of POM molecules their proximity to one another is effectively controlled, limiting molecular motion in two dimensions but leaving the third dimension available for intermolecular reactions between pairs of neighbouring molecules. By coupling the information gained from high resolution structural and kinetics experiments via the variation of key imaging parameters in the TEM, we shed light on the reaction mechanism. The dissociation of W–O bonds, a key initial step of POM reactions, is revealed to be reversible by the kinetic analysis, followed by an irreversible bonding of POM molecules to their nearest neighbours, leading to a continuous tungsten oxide nanowire, which subsequently transforms into amorphous tungsten-rich clusters due to progressive loss of oxygen atoms. The overall intermolecular reaction can therefore be described as a step-wise reductive polycondensation of POM molecules, via an intermediate state of an oxide nanowire. Kinetic analysis enabled by controlled variation of the electron flux in TEM revealed the reaction to be highly flux-dependent, which leads to reaction rates too fast to follow under the standard TEM imaging conditions. Although this presents a challenge for traditional structural characterisation of POM molecules, we harness this effect by controlling the conditions around the molecules and tuning the imaging parameters in TEM, which combined with theoretical modelling and image simulation, can shed light on the atomistic mechanisms of the reactions of POMs. This approach, based on the direct space and real time chemical reaction analysis by TEM, adds a new method to the arsenal of single-molecule kinetics techniques.We induce and study reactions of polyoxometalate (POM) molecules, [PW 12O 40] 3− (Keggin) and [P 2W 18O 62] 6− (Wells–Dawson), at the single-molecule level, utilising TEM as an analytical tool, and nanotubes as test tubes. 相似文献
19.
A series of polyoxometalates (POMs) that incorporate the highest‐nuclearity Ln clusters that have been observed in such structures to date (Ln 26 , Ln=La and Ce) are described, which exhibit giant multishell configurations (Ln⊂W 6⊂Ln 26⊂W 100). Their structures are remarkably different from known giant POMs that feature multiple Ln ions. In particular, the incorporated Ln–O clusters with a nuclearity of 26 are significantly larger than known high‐nuclearity (≤10) Ln–O clusters in POM chemistry. Furthermore, they also contain the largest number of La and Ce centers for any POM reported to date and represent a new kind of rare giant POMs with more than 100 W atoms. Interestingly, the La 26‐containing POM can undergo a single‐crystal to single‐crystal structural transformation in the presence of various transition‐metal ions, such as Cu 2+, Co 2+, and Ni 2+, from an inorganic molecular nanocluster into an inorganic–organic hybrid extended framework that is built from POM building blocks with even higher‐nuclearity La 28 clusters bridged by transition‐metal complexes. 相似文献
20.
Two new Wells–Dawson based compounds containing alkali metals, [Ag(H 2biim) 2] 2·[Ag 5(H 2biim) 10Na 2(H 2O) 2(H 3/2P 2W 18O 62) 2]·12H 2O ( 1) and [Cd(H 2biim) 2?K(P 2W 18O 62) 1/2] ( 2) (H 2biim?=?2,2′-biimidazole), have been synthesized under hydrothermal conditions. In 1, two-supporting Wells–Dawson anions are linked by a [Ag(H 2biim) 2] + subunit to form a dimer. The adjacent dimers are further connected by Na + through (POM)O-Na-O(POM) bonds to build a 1-D chain. In 2, adjacent anions are linked by two [Cd 2(H 2biim) 2] 4+ subunits and a 1-D chain is formed. Furthermore, the anion in the chain is fused by six K + ions and a 3-D framework is obtained. The alkali metals exhibit crucial influence on the conversion of dimensionality assisting anions and Ag-H 2biim subunits to construct 1-D and 3-D frameworks. The electrochemical and photocatalytic properties of 1 and 2 have been investigated. 相似文献
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