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1.
Inorg Chem ; 60(20): 15759-15767, 2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34606253

RESUMO

The crown-shaped organotriphosphonate-modified 36-molybdenum cluster (NH4)18Na7H11[Zn(H2O)TeMo6O21{N(CH2PO3)3}]6·23H2O (1) has been synthesized, which is the largest zinc-containing organophosphonate-based polyoxometalate to date. Compound 1 was prepared in buffer solution (pH 5.5) with heptamolybdate and amino trimethylene phosphonic acid (ATMP) as the organic ligand. The polyanion constructed from a hexmeric assembly of [Zn(H2O){TeMo6O21}{N(CH2PO3)3}]6- subunits has been fully investigated by a few characterization methods. In this work, we discovered that 1 exhibited reversible photochromism and it changed from white to reddish brown upon UV irradiation. In addition, compound 1, as a catalyst, can oxidize sulfides to sulfoxides, showing a high yield/conversion and a good selectivity.

2.
Inorg Chem ; 60(19): 14872-14879, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34533941

RESUMO

A novel organodiphosphonate-based telluromolybdate cluster, (NH4)6Na3H13[TeMo10O37(CoMo2O6L)4]·11H2O [1; L = (O3P)2C(O)(CH2)3NH2], has been successfully synthesized by a simple one-pot aqueous reaction. Intriguingly, the [TeMo10O37]10- subunit with tetrahedral geometry of TeO4 is observed in the organophosphonate-functionalized polyoxometalates for the first time. Compound 1 was prepared in a buffer solution (pH = 5.5) with alendronic acid (Ale) and (NH4)6Mo7O24·4H2O as raw materials. The polyanion [TeMo10O37(CoMo2O6L)4]22- was constructed from four {Mo2O6L} subunits encapsulating an interesting Te-Mo heterometal subunit [TeMo10O37]10- through four CoO6 octahedra and has been fully characterized by routine techniques. In addition, compound 1, as a heterogeneous catalyst, shows good conversion (92%) and high selectivity (99%) for Knoevenagel condensation reaction.

3.
Chem Commun (Camb) ; 57(79): 10250-10253, 2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34528652

RESUMO

The first example of Rh-substituted organic-inorganic hybrid arsenotungstate [H2N(CH3)2]8{[Na(H2O)4]NaAs2W22(CH3COO)2O76 Rh2(N(CH3)2)2}·H2O (1) synthesised in an aqueous solution by the conventional method is reported. Two [Rh(N(CH3)2)]3+ fragments are imbedded into the vacancy of the [NaAs2W22(CH3COO)2O76]15- unit by Rh-As bonds [2.439(1) Å], which are observed in POM chemistry for the first time.

4.
Dalton Trans ; 50(36): 12664-12673, 2021 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-34545885

RESUMO

A novel ruthenium-containing polyoxometalate-based organic-inorganic hybrid, K4Na9H7.4[(AsW9O33)4(WO2)4{Ru3.2(C3H3N2)2}]·42H2O (1), was successfully synthesized by a one-step hydrothermal method under acidic conditions, which applied a self-assembly strategy between inorganic polyoxometalate based on trivacant [B-α-AsW9O33]9- {AsW9} fragments and an organic ligand, imidazole (C3H4N2). Compound 1 was further characterized by single-crystal X-ray diffraction, PXRD, IR spectroscopy, UV-Vis spectroscopy, ESI-MS, elemental analysis and TGA. Single-crystal X-ray diffraction data reveal that the polyanion consists of four trivacant Keggin-type polyanion {AsW9} building blocks bridged by four {WO6} units, leading to a crown-shaped tetrameric structure [(AsW9O33)4(WO2)4{Ru3.2(C3H3N2)2}]20.4-. The ESI-MS result reveals that the polyanion unit has excellent structural integrity in water. Moreover, the catalysis study of 1 was also further investigated, and the experimental results indicate heterogeneous catalyst 1 presents high efficiency (yield = 98%), excellent selectivity (>99%), and good recyclability for the oxidation of 1-(4-chlorophenyl)ethanol to 4'-chloroacetophenone with commercially available 70% aqueous tert-butyl hydroperoxide {TBHP (aq.)} as the oxidant at room temperature.

5.
Chem Commun (Camb) ; 57(80): 10415-10418, 2021 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-34546227

RESUMO

Ultrafine ternary carbide Co6W6C@C nanoparticles (NPs) were successfully synthesized and these NPs exhibited high catalytic activities for the hydrazine oxidation reaction (HzOR) under alkaline conditions. In a practical O2-hydrazine fuel cell test, its peak power density reached 203 mW cm-2, a value superior to that of the state-of-the-art commercial Pt/C catalyst.


Assuntos
Fontes de Energia Elétrica , Hidrazinas/química , Nanopartículas Metálicas/química , Carbono/química , Catálise , Cobalto/química , Eletrodos , Oxirredução , Oxigênio/química , Compostos de Tungstênio/química
6.
Inorg Chem ; 60(11): 8164-8172, 2021 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-34014645

RESUMO

A series of benzoate-decorated lanthanide (Ln)-containing tetrameric Dawson-type phosphotungstates [N(CH3)4]6H20[{(P2W17O61)Ln(H2O)3Ln(C6H5COO)(H2O)6]}{[(P2W17O61)Ln(H2O)3}]2Cl2·98H2O [Ln = Sm (1), Eu (2), and Gd (3)] were made using a facile one-step assembly strategy and characterized by several techniques. Notably, the Ln-containing tetrameric Dawson-type polyoxoanions [{(P2W17O61)Ln(H2O)3Ln(C6H5COO)(H2O)6]}{[(P2W17O61)Ln(H2O)3}]224- are all established by four monolacunary Dawson-type [P2W17O61]10- segments, encapsulating a Ln3+ ion with two benzoates coordinating to the Ln3+ ions. 1-3 exhibit reversible photochromism, which can change from intrinsic white to blue for 6 min upon UV irradiation, and their colors gradually recover for 30 h in the dark. The solid-state photoluminescence spectra of 1 and 2 display characteristic emissions of Ln components based on 4f-4f transitions. Time-resolved emission spectra of 1 and 2 were also measured to authenticate the energy transfer from the phosphotungstate and organic chromophores to Eu3+. In particular, 1 shows an effectively switchable luminescence behavior induced by its fast photochromism.

7.
Inorg Chem ; 60(11): 7753-7761, 2021 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-34019402

RESUMO

Developing new catalysts for highly efficient and selective oxidation of saturated C-H bonds is significant due to their thermodynamic strength. Via incorporation of PW12O403-, pyridine-2,5-dicarboxylic acids (pydc), and Fe(III) ions into one framework, a new polyoxometalate-based metal-organic framework, [HFe4O2(H2O)4(pydc)3PW12O40]·10.5H2O (FeW-PYDC), was successfully prepared by a hydrothermal method. Interestingly, FeW-PYDC features a three-dimensional porous structure with {Fe4O2} interconnecting with PW12O403- units. FeW-PYDC displayed excellent performance in the selective oxidation of C-H bonds of alkylbenzenes with high conversion (95.7%) and selectivity (96.6%). As an effective heterogeneous catalyst, FeW-PYDC demonstrates good reusability and structural stability.

8.
Dalton Trans ; 50(22): 7610-7620, 2021 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-33988637

RESUMO

Three structurally intriguing polyoxoniobates (PONbs) based on the trivacant B-type α-Keggin ion {TeNb9O33}, H4K(CN3H6)2{[Cu4(2,2'-bipy)4(H2O)2][TeNb9V2O37]}·29H2O (1, 2,2'-bipy = 2,2'-bipyridine), H0.5K5Na2.5{[Cu(en)H2O]3[TeNb9V3O39]}·10H2O (2, en = ethylenediamine), and K3Na5{[Cu(1,3-dap)H2O]3[TeNb9V3O39]}·11H2O (3, 1,3-dap = 1,3-diaminopropane), are assembled by the conventional aqueous solution methods using a series of N-containing organic ligands. In 1, each of the two {VO4} units is attached to two coplanar NbO6 octahedra on the {Nb3O13} cluster of the {TeNb9O33} unit. Differently, three {VO4} units in 2 and 3 are linked to two edge-sharing NbO6 octahedra, respectively. Compounds 1-3 represent the first oxo NbTeV clusters and also the first vanadoniobates based on the trivacant Keggin PONb units. All three compounds were characterised by single-crystal X-ray structural analysis, TGA and IR, ESI-MS and 51V NMR spectroscopy. Furthermore, the magnetic properties of compounds 1 and 2 were also studied.

9.
Chem Commun (Camb) ; 57(33): 3999-4002, 2021 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-33885695

RESUMO

A 72-nuclearity niobium cluster was synthesized, in which two {CuNb26O76} clusters and one {Nb20O59} cluster are fused in a triangular fashion, resulting in a {Nb12} cavity. Further, the simple nature of the species allowed its investigation by ESI-MS analysis, yielding two subunits with time.

10.
Nanoscale ; 13(17): 8077-8086, 2021 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-33899868

RESUMO

Five-coordinate geometry around ruthenium with highly exposed active sites has attracted intensive scientific interest due to its superior properties and extensive applications. Herein, we report a series of structurally controllable multi-Ru-bridged polyoxometalates, K5NaH10[{Ru4(H2O)n}(WO2)4(AsW9O33)4]·mH2O {1, 1-dehyd-373K, 1-dehyd-473K, 1-dehyd-573K; n = 4, m = 36; n = 4, m = 6; n = 4, m = 0; n = 0, m = 0} fabricated through a feasible assembly strategy using arsenotungstate {2, KNa12H17Cl2(As4W40O140)·29H2O} as a structure-directing unit. Systematic characterization methods identified that the six-coordinate geometry can successfully transform into five-coordinate geometry about active sites (Ru) by removing aqua ligands under high reaction temperatures. All the multi-Ru-bridged polyoxometalates demonstrated strong stability and catalytic effectiveness in the transformation of 1-(4-chlorophenyl)ethanol to 4'-chloroacetophenone under very mild conditions. 1-dehyd-573K, specifically, achieves the best catalytic effectiveness with a turnover frequency (TOF) = 25 100·h-1 owing to its unique five-coordinate geometry on the Ru sites. To our knowledge, 1-dehyd-573K outperforms other POM-based catalysts in the oxidative catalysis of 1-(4-chlorophenyl)ethanol. The heterogeneous polyoxometalates were also proven to be strongly reusable, with their structural integrities well maintained after multiple-cycle catalytic reactions.

11.
Front Chem ; 9: 615595, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33681143

RESUMO

A three-dimensional (3D) Silverton-type polyoxomolybdate (POMo) with the formula of NH4{Mn4[PrMo12O42]}·18H2O (1) was successfully isolated and well characterized by single crystal X-ray diffraction, X-ray powder diffraction pattern, infrared spectrum, thermogravimetric and elemental analyses. The inorganic building block {PrMo12O42} has formed 3D frameworks via the {MnO6} linker. The excitation of compound 1 in solid state at 375 nm displays red emission. Moreover, variable temperature magnetic susceptibility measurements indicate that the magnetic behavior in compound 1 is dominated by antiferromagnetic interactions.

12.
Inorg Chem ; 60(7): 4792-4799, 2021 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-33715352

RESUMO

A copper-containing polyoxometalate-based metal-organic framework (POMOF), CuI12Cl2(trz)8[HPW12O40] (HENU-7, HENU = Henan University; trz = 1,2,4-triazole), has been successfully synthesized and well-characterized. In addition, the excellent catalytic ability of HENU-7 has been proved by the selective oxidation of diphenylmethane. Under the optimal conditions, the diphenylmethane conversion obtained over HENU-7 is 96%, while the selectivity to benzophenone is 99%, which outperforms most noble-metal-free POM-based catalysts. Moreover, HENU-7 is stable to reuse for five runs without an obvious loss in activity and also can catalyze the oxidation of different benzylic C-H with satisfactory conversions and selectivities, which implied the significant catalytic activity and recyclability.

13.
Inorg Chem ; 60(5): 2888-2892, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33576618

RESUMO

A new family of trinuclear transition-metal (TM)-sandwiched heteropolyoxovanadates (hetero-POVs) [(SeV10O28(SeO3)3M(H2O)3)2(M(H2O)4)]10- (Se8V20M3, where M = Mn2+, Co2+, and Zn2+) were prepared using two feasible approaches: a stepwise assembly strategy atop the POV precursor Se4V10 and a one-pot reaction approach of KVO3, SeO2, TM2+, and a proline ligand. The crystallographic studies reveal that Se8V20M3 consist of two asymmetric [SeV10O28(SeO3)3M(H2O)3)]6- units, linked by another TM2+ ion, thus forming an interesting staggered sandwich-type arrangement. Additionally, Se8V20M3 and Se8V20M present strong correlations between their structures and catalytic properties. In particular, Se8V20M3 demonstrate an analogical heterogeneous catalytic performance as Se8V20M in the sulfoxidation reaction of thioethers owing to their structural similarities.

14.
Chem Commun (Camb) ; 57(17): 2172-2175, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33524095

RESUMO

Two new members of highly charged Silverton archetype [NaM12O42]11- were demonstrated in the 3D POM-based frameworks Na3[NaM12O42(Ru(DMSO)3)4]·13H2O (M = Mo (1), W (2)), where the unusual icosahedron coordination of a Na+ ion incubated as a heteroatom is reported for the first time in topical POMs. Furthermore, 23Na NMR was applied to certify the interpretation of X-ray diffraction data concerning Na localization. Additionally, the porous nature of the frameworks 1 and 2 has also been investigated.

15.
Inorg Chem ; 60(2): 682-691, 2021 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-33355447

RESUMO

Two-dimensional (2D) crystalline porous materials with designable structures and high surface areas are currently a hot research topic in the field of proton- and electron-conducting materials, which provide great opportunities to orderly accommodate carriers in available spaces and to accurately understand the conducting path. The 2D dual-conductive inorganic framework [Co(H2O)6]2{[Co(H2O)4]4[WZn3(H2O)2(ZnW9O34)2]}·8H2O (Co6Zn5W19) is synthesized by combining [WZn3(H2O)2(ZnW9O34)2]12- (Zn5W19) and a Co(II) ion via a hydrothermal method. Due to the presence of a consecutive H-bonding network, electrostatic interactions, and packing effects between the framework and guest molecules, Co6Zn5W19 displays a high proton conductivity (3.55 × 10-4 S cm-1 under 98% RH and 358 K) by a synergistic effect of the combined components. Additionally, a photoactuated electron injection into the semiconducting materials is an important strategy for switching electronic conductivity, because it can efficiently reduce the frameworks without destroying the crystallinity. I-V curves of a tablet of Co6Zn5W19 in the reduced and oxidized states yield conductivities of 1.26 × 10-6 and 5 × 10-8 S cm-1, respectively. Moreover, Co6Zn5W19 is also successfully applied in the photocatalytic reduction of the toxic Cr(VI) metal ion by utilizing its excellent electronic storage capacity and Baeyer-Villiger (BV) oxidation in a molecular oxygen/aldehyde system.

16.
Dalton Trans ; 49(44): 15731-15738, 2020 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-33146210

RESUMO

Three oxalate-bridging lanthanide-based polyoxometalates (Ln-POMs) K17Na2H5[{(As2W19O67(H2O))Ln(H2O)2}2(C2O4)]·50H2O. [Ln = Sm3+ (1), Pr3+ (2), and Ce3+ (3)] were successfully synthesized. The structures were further characterized by single-crystal X-ray diffraction analyses, Raman spectroscopy, elemental analyses, powder X-ray diffraction (PXRD), IR spectra, UV/vis diffuse reflectance spectroscopy, and thermogravimetric analysis (TGA). The structural characterization study reveals that Ln-POMs 1-3 crystallize in the form of the triclinic space group P1[combining macron] and consist of an oxalate bridging di-Ln3+-incorporated H-shaped dimer, which can also be viewed as a combination of two half-units {Ln(As2W19O67(H2O))(H2O)2}222- related by an inversion center. It is worth noting that the opening angle (33.01°) from the [As2W19O67(H2O)]14- fragment in 1-3 is less than that of the [As2W19O67(H2O)]14- precursor (40.99°). Furthermore, the stability of 1-3 in aqueous solution and their solid-state photoluminescence properties have also been investigated in this work.

17.
Dalton Trans ; 49(35): 12458-12465, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32930684

RESUMO

A triangular {Er3} cluster containing polyoxometalate (POM), [Er3(µ3-OH)(H2O)8(AsW9O33)(AsW10O35(dl-mal))]222- (1) (mal = malate), has been obtained via one-pot reactions. Structural analyses demonstrate that three Er3+ ions bridged one µ3-OH to generate a rare µ3-OH-capped triangular {Er3} cluster, which connects two different vacant polyanions to form an unsymmetrical sandwich-type subunit, and adjacent sandwiched subunits are linked through mal ligands to give the targeted dimer. When the Er3+ ions are substituted in whole or in part with Y3+ ions, the diamagnetic yttrium analogue [Y3(µ3-OH)(H2O)8(AsW9O33)(AsW10O35(dl-mal))]222- (2) and diluted sample [Er0.15Y2.85(µ3-OH)(H2O)8(AsW9O33)(AsW10O35(dl-mal))]222- (Er@2) have also been synthesized. Magnetic studies reveal that 1 exhibits field-induced two-step magnetic relaxation processes; the slow relaxation process may arise from intramolecular magnetic interactions, whereas the fast one is likely to originate from the intermolecular dipole-dipole interactions supported by the magnetic results of Er@2. From ab initio calculations, it is found that although the magnetic anisotropies of 1 mainly originate from individual Er3+ fragments, the Er3+-Er3+ interactions have a considerable influence on their slow magnetic relaxation processes.

18.
Chem Commun (Camb) ; 56(84): 12849-12852, 2020 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-32969428

RESUMO

We present a single molecular polyoxometalate cluster (K41[(P2W12Nb6O62)6{Mn3(OH)3(H2O)6}4{Mn3Na(H2O)16}]·26H2O) with controllable release of a large number of protons (∼40 per molecule) in its aqueous solution upon addition of a base. The deprotonation/protonation process is reversible with the clusters remaining intact. This molecule can also absorb up to 11 protons per cluster when an acid, HCl, was added to its original aqueous solution. To the best of our knowledge, such large proton absorption/release capacity along with excellent stability is unprecedented.

19.
Inorg Chem ; 59(18): 13733-13740, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32865978

RESUMO

A high-nuclear Mn72W48 cluster has been successfully synthesized by employing acetate coordinated Mn12 and Na2WO4 as starting materials. To investigate the synthesis mechanism, a series of synthesis experiments and high-resolution ESI-MS tests were designed and conducted. These experimental results demonstrate that inorganic tungstates exhibit better coordination capacity and variability than organic acetates in Mn12. Furthermore, a series of low nuclearity Mn clusters and Mn-W species were successfully detected and a possible synthesis mechanism of Mn72W48 was proposed. These results show that inorganic tungstate ligands have a great potential to construct high-nuclear transition-metal-oxo clusters by forming various intermediates.

20.
Inorg Chem ; 59(13): 8690-8698, 2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32623893

RESUMO

POM-supported metal carbonyl derivatives (PMCDs) represent a family of tremendous potential catalysts owing to their peculiar physical and chemical properties. Yet low-valence transition metal-substituted Dawson-type PMCD catalysts are uncommon. Hence, we synthesized a tricobalt-substituted PMCDs by conventional aqueous solution method, [Na(H2O)5](NH4)7[P2W15O56Co3(H2O)3(OH)3Re(CO)3]·13H2O (1), and characterized by single crystal X-ray diffraction crystallography, IR, and thermogravimetric analyses (TGA), etc. The obtained compound 1 was employed as a catalyst for the oxidation of diphenylmethane (DPM) to benzophenone, giving 96.8% yield in the presence of tert-butyl hydroperoxide (TBHP) and pyridine. The control experiments indicate that Co metal ion plays an important role in the catalytic reactions. As a side note, the electrospray ionization mass spectrometry (ESI-MS) and UV spectroscopy showed that 1 can retain its integrity in solution, and magnetic measurements indicated that 1 exhibited a weaker ferromagnetic interaction at low temperature.

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