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1.
A new 3D coordination polymer {[Gd2(bpdc)3(H2O)3]·H2O}n(1) has been isolated from the reaction of 2,2′-bipyridine-4,4′-dicarboxylic acid (H2bpdc) and Gd(III) salts under hydrothermal conditions. Single-crystal X-ray diffraction study shows that compound 1 is constructed from Gd2-based second building units (SBUs) [Gd2(bpdc)3(H2O)3] and displays a 3D (3,4,8)-connected net with (42·6)(32·42·52)(32·45·54·611·76) topology. A thermogravimetric analysis of 1 shows a high thermal stability. The magnetic behavior of 1 reveals a weak antiferromagnetic interaction between Gd(III) ions.  相似文献   

2.
A monolayer of Keggin-type heteropolyanion [SiNi(H2O)W11O39]6− was fabricated by electrodepositing [SiNi(H2O)W11O39]6− on cysteamine modified gold electrode. The monolayer of [SiNi(H2O)W11O39]6− modified gold electrode was characterized by atomic force microscopy (AFM) and electrochemical method. AFM results showed the [SiNi(H2O)W11O39]6− uniformly deposited on the electrode surface and formed a porous monolayer. Cyclic voltammetry exhibited one oxidation peak and two reduction peaks in 1.0 M H2SO4 in the potential range of −0.2 to 0.7 V. The constructed electrode could exist in a large pH (0-7.6) range and showed good catalytic activity towards the reduction of bromate anion (BrO3) and nitrite (NO2), and oxidation of ascorbic acid (AA) in acidic solution. The well catalytic active of the electrode was ascribed to the porous structure of the [SiNi(H2O)W11O39]6 monolayer.  相似文献   

3.
A novel sandwich-type lanthanide polyoxometalate (NH4)2[N(CH3)4]6Na2[Ce(PW11O39)2] · 14H2O (1) has been synthesized and characterized by cyclic voltammetry, IR spectroscopy and single crystal X-ray diffraction. X-ray diffraction result reveals that the sandwich-type polyanions are linked by sodium ions to form a structure of zigzag chains, and the chains are further connected into an extensive two-dimensional (2D) framework depending on hydrogen bond.  相似文献   

4.
A novel supramolecular assembly consisting of sodium-dibenzo-18-crown-6(DB18C6) complex cation [Na(C20H24O6)(CH3CN)2]2+ and isopolyanion [Mo6O19]2− has been demonstrated in the 3D structure of [Na(C20H24O6)(CH3CN)2]2[Mo6O19] · 4CH3CN (1). Weak intermolecular forces (C–HO hydrogen bonds) between isopolyanion and crown ether play a significant role in the construction of supramolecular framework in the crystal structure of 1. Compound 1 has been characterized in the solid state by single crystal X-ray diffraction, IR, CHN analysis, and TGA.  相似文献   

5.
The reaction of Np(V) methanesulfonate solution with imidazole led to the in situ formation of oxalic acid and the reduction of Np(V) to Np(IV). As a result, the novel organically templated organic polymer, (ImidazoleH)[Np(C2O4)(CH3SO3)3(H2O)2], was formed. The structure consists of infinite chains of [Np(C2O4)(CH3SO3)3(H2O)2] and imidazolium cations. The crystal structure is confirmed by IR and UV–vis spectroscopic data. This complex is the first example of structurally characterized 1:1 An(IV) oxalate.  相似文献   

6.
Free acids of the iron substituted heteropoly acids (HPA), H7[(P2W17O61)FeIII(H2O)] (HFe1) and H18[(P2W15O56)2FeIII2(H2O)2] (HFe2) were prepared from the salts K7[(P2W17O61)FeIII(H2O)] (KFe1) and Na12[(P2W15O56)2FeIII4(H2O)2] (NaFe4), respectively. The iron-substituted HPA were adsorbed on to XC-72 carbon based GDLs to form HPA doped GDEs after water washing with HPA loadings of ca. 1 μmol. The HPA was detected throughout the GDL by EDX. Solution electrochemistry of the free acids are reported for the first time in sulfate buffer, pH 1-3. The hydrogen oxidation reaction was catalyzed by KFe1 at 0.33 V, with an exchange current density of 38 mA/cm2. Moderate activity for the oxygen reduction reaction was observed for the iron substituted HPA, which was dramatically improved by selectively removing oxygen atoms from the HPA by cycling the fuel cell cathode under N2 followed by reoxidation to give a restructured oxide catalyst. The nanostructured oxide achieved an OCV of 0.7 V with a Tafel slope of 115 mV/decade. Cycling the same catalysts in oxygen resulted in an improved catalyst/ionomer/carbon configuration with a slightly higher Tafel slope, 128 mV/decade but a respectable current density of 100 mA/cm2 at 0.2 V.  相似文献   

7.
The synthesis of intercluster porous nanocomposites obtained from polyoxometallate compounds such as the [AlO4Al12(OH)24(H2O)12]7+ cation (named Al13) and the Anderson-type [Al1−x Cr x Mo6O24H6]3− anion (named Al1−x Cr x Mo6) has been performed in order to study the interaction between the two cluster ions, the stability of the XMo6 planar configuration, the products obtained after thermal treatment, the structure and the local symmetry of the Cr3+ species. Chemical, thermal, structural and spectroscopic characterizations of the original and thermally treated phases have been followed by different techniques such as TG-DTA, XRD, SEM-EDAX, and mainly by EPR. All the results have shown that the structure of the intercluster nanocomposites (Al13)(Al1−x Cr x Mo6)2 precursors is similar to that reported by Son et al. for the chromium-free (Al13)(AlMo6)2 intercluster nanocomposite [Son et al., J. Am. Chem. Soc. 122 (2000) 7432]. After thermal treatment in air at several temperatures of the (Al13)(Al1−x Cr x Mo6)2 nanocomposites the following phases have been observed and characterised: (i) at 400 °C an amorphous phase containing dispersed Cr3+ ions; (ii) at 700 °C a crystalline phase corresponding to Cr2(MoO4)3/Al2(MoO4)3 solid solutions; (iii) at 950 °C α-Al2O3/Cr2O3 solid solutions with a random dispersion of the Cr3+ ions.  相似文献   

8.
The first example of disubstituted Lindqvist-type polyoxomolybdate {[V(2,2-bipy)2]2(4,4-bipy)[Te2Mo4O19]} has been synthesized hydrothermally and characterized by elemental analyses, XPS, IR, TG-DTA and X-ray single crystal diffraction. The structural analysis shows that the neutral molecular unit [V(2,2-bipy)2]2[Te2Mo4O19] consists of a novel Lindqvist-type polyanion [Te2Mo4O19]6− supporting two vanadyl moieties [V(2,2-bipy)2]3+, and such neutral molecules are joined together by π − π stacking interactions between the pyridine groups to form a two-dimensional grid-like network with non-coordinating “guest” 4,4-bipys encapsulated.  相似文献   

9.
Summary The kinetics of the dibutyltin diacetate (DBTA) – catalyzed polymerization reactions of (η5-C5H4CH2CH2OH)2Mo2(CO)6 with Hypol 2000 (an isocyanate-terminated polyether prepolymer) and with 1,4-butanediol were studied, as were the kinetics of a copolymerization involving (η5-C5H4CH2CH2OH)2Mo2(CO)6 and PEG-1000 (a poly(ethylene glycol)) with Hypol 2000. The purpose was to determine if (η5-C5H4CH2CH2OH)2Mo2(CO)6 appreciably affected the overall rate of the polymerization reaction and if it changed the mechanism of the reaction. The kinetics were analyzed with a fitting program, which allowed extraction of the rate constants for the individual elementary steps in the mechanism. The results showed that (η5-C5H4CH2CH2OH)2Mo2(CO)6 does not significantly alter the timescale of the reaction and that the same reaction mechanism is likely used as with the 1,4-butanediol and PEG-1000. There are some differences in the rate constants of the elementary steps, but these differences can be attributed to the increased steric crowding caused by the bulkier (η5-C5H4CH2CH2OH)2Mo2(CO)6 diol. The effect of the (η5-C5H4CH2CH2OH)2Mo2(CO)6 on the polymers’ physical properties was also investigated. As is the case with other segmented polyurethanes, the hydrogen bonding index (HBI) and the relative amount of soft segments of the (η5-C5H4CH2CH2OH)2Mo2(CO)6-containing polyurethane correlate in a general way with the physical properties of the polymer.  相似文献   

10.
The Se(VI)-analogues of ettringite and monosulfate, selenate-AFt (3CaO·Al2O3·3CaSeO4·37.5H2O), and selenate-AFm (3CaO·Al2O3·CaSeO4·xH2O) were synthesised and characterised by bulk chemical analysis and X-ray diffraction. Their solubility products were determined from a series of batch and resuspension experiments conducted at 25 °C. For selenate-AFt suspensions, the pH varied between 11.37 and 11.61, and a solubility product, log Kso=61.29±0.60 (I=0 M), was determined for the reaction 3CaO·Al2O3·3CaSeO4·37.5H2O+12 H+⇔6Ca2++2Al3++3SeO42−+43.5H2O. Selenate-AFm synthesis resulted in the uptake of Na, which was leached during equilibration and resuspension. For the pH range of 11.75 to 11.90, a solubility product, log Kso=73.40±0.22 (I=0 M), was determined for the reaction 3CaO·Al2O3·CaSeO4·xH2O+12 H+⇔4Ca2++2Al3++SeO42−+(x+6)H2O. Thermodynamic modelling suggested that both selenate-AFt and selenate-AFm are stable in the cementitious matrix; and that in a cement limited in sulfate, selenate concentration may be limited by selenate-AFm to below the millimolar range above pH 12.  相似文献   

11.
A new oxidation state Keggin-type isopolyoxomolybdate, (C3H5N2)4H[MoVI0.5MoVI12O40]·H2O (1), was synthesized and structurally characterized by single crystal X-ray crystallography, spectroscopy, and further characterized by IR spectroscopy, UV–vis spectra, ESI-MS and thermogravimetric analysis. All the Mo atoms in the [[MoVI0.5MoVI12O40]]5  anion are Mo6 +, which was confirmed by the X-ray photoelectron spectroscopy(XPS), bond valence sum (BVS), and UV–vis spectra. Electrospray ionization mass spectrometry (ESI-MS) results suggest that {Mo12O40} and {Mo13O40} fragments coexist in compound 1. Compound 1 demonstrated good electrocatalytic activity for nitrite and hydrogen peroxide reduction.  相似文献   

12.
In this study, we synthesized a new hybrid material using well-Dawson K6[P2Mo18O62nH2O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). CHN elemental analysis showed that one mole of [P2Mo18O62]6− reacts with 6 moles of [BMIM]+ to form [BMIM]6P2Mo18O62. 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 material compared to the parent Dawson POM. The new hybrid material [BMIM]6P2Mo18O62 was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P2Mo18O62]6−, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]6P2Mo18O62. The relationship between the peak currents of the deposited [BMIM]6P2Mo18O62 film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]6P2Mo18O62 modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]6P2Mo18O62 modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]6P2Mo18O62 modified GC electrode occurs at low potential of ∼0 V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]6P2Mo18O62 and [P2Mo18O62]6− modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]6P2Mo18O62 film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]6P2Mo18O62/GC has a significant sensitivity of ∼63 nA/μM AA, fast response time (<9 s), low detection limit (<0.1 μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1 μM to at least 22 mM AA and was stable for at least 2 weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7.  相似文献   

13.
Cyclic voltammetry and degradation of dimethylphthalate (DMP) revealed that the iron-substituted heteropolytungstate anion PW11O39Fe(III)(H2O)4− is an excellent indirect cathodic oxidative electrocatalyst in the presence of H2O2. PW11O39Fe(III)(H2O)4− can electrocatalyze the reduction of H2O2 to hydroxyl radicals via an inner-sphere electron transfer mechanism, which cause oxidative decomposition of DMP. Almost complete DMP removal and ca. 30% mineralization were obtained in less than 120 min in a mixed phosphate solution at pH 6.86 containing 0.1 mM DMP. MS analyses of the intermediates and final products suggested that glyoxal, oxalic acid and acetic acid are the main ring-opening products, besides some unstable hydroxylated aromatic intermediates. The effects of added H2O2 concentration, applied cathodic potential and DMP initial concentration on the degradation of DMP were also investigated. A concentration of 1.0 mM H2O2 and cathodic potential of −0.3 V were optimal conditions for DMP degradation in our experiments. At higher initial DMP concentrations degradation also occurred, but at a slower decay rate compared to lower initial concentrations. The present system thus represents a possible method to use PW11O39Fe(III)(H2O)4− as an indirect cathodic oxidative electrocatalyst in water and wastewater treatment.  相似文献   

14.
A series of transition metal (i.e. Cu2+ and Co2+) substituted Krebs type polyoxometalates (POMs), of the general formula [X2W20M2O70(H2O)6]n, X = Sb or Bi, M = Co(II) or Cu(II), have been successfully immobilised onto carbon electrode surfaces through the employment of the layer-by-layer (LBL) technique. This involved the construction of alternating anionic POM, [X2W20M2O70(H2O)6]n, layers and the cationic metallodendrimer, Ru(II)-metallodendrimer as the cationic layers, in addition to a [poly(diallyldimethylammonium chloride)] PDDA base layer. Stable multielectron redox couples associated with the W–O framework, for the Krebs type POMs, and the Ru(III/II) for the metallodendrimer, were clearly observed upon layer construction and redox switching within the pH domain of 2–6.5. The constructed multilayer assemblies exhibited pH dependent redox activity and thin layer behaviour up to 100 mV s−1. The porosity and permeability of the individual multilayer assemblies towards an anionic probe were determined by AC impedance and cyclic voltammetry. The surface morphology of each multilayer was also determined by Atomic Force Microscopy (AFM).  相似文献   

15.
The title compound, [Sm2(C3H2O4)3(H2O)6], was investigated by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with cell parameters a = 17.1650(8) ?, b = 12.3010(5) ?, c = 11.1420(4) ?, β = 127.5161(10)°, Z = 4 and V = 1866.04(14) ?3. The Sm atom lies on a two-fold axis and has nine-coordination with six oxygen atoms from carboxylate groups and three water molecules. The compound forms a layer-type polymeric structure. The layers are formed by samarium and one independent malonate group to give a three-dimensional framework. The extensive network of hydrogen bonds and bridge bonds observed in this structure enhances the structural stability. The thermal dehydration of the compound was investigated by thermogravimetric analysis.  相似文献   

16.
A novel heteropolyoxometallate with the formula [H3NNH3]2K2MnMo9O32·(NH3)·3H2O has been prepared in water solution. The crystal structure of the title compound was determined by the single-crystal method. This new mixed metal anionic complex crystallizes in the rhombohedral space group R3 (No. 146) with a=b=15.873(5), c=12.344(6) Å, γ=120°. The disordered structure contains three molecules in the unit cell. Full-matrix least-squares refinements of the title complex yielded final reliability (R) factors of 0.0356 (Rw=0.0868) with a goodness-of-fit (GOF, Σ2) value of 1.099 based on 1430 [I>2σ(I)] observed reflections. All Mo and Mn atoms are six-coordinated octahedrally to form a Mn-centered cage with a Mo9O32 group as the framework.  相似文献   

17.
The modification of a gold electrode surface by electropolymerization of trans-[Ru(NH3)4(Ist)SO4]+ to produce an electrochemical sensor for nitric oxide was investigated. The influence of dopamine, serotonin and nitrite as interferents for NO detection was also examined using square-wave voltammetry (SWV). The characterization of the modified electrode was carried out by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and SERS techniques. The gold electrode was successfully modified by the trans-[Ru(NH3)4(Ist)SO4]+ complex ion using cyclic voltammetry. The experiments show that a monolayer of the film is achieved after ten voltammetric cycles, that NO in solution can coordinate to the metal present in the layer, that dopamine, serotonin and nitrite are interferents for the detection of NO, and that the response for the nitrite is much less significant than the responses for dopamine and serotonin. The proposed modified electrode has the potential to be applied as a sensor for NO.  相似文献   

18.
[Os(bpy)3]3[P2W18O62] has been synthesised and characterised by elemental analysis, spectroscopic (UV-vis, IR spectroscopy) and electrochemical techniques. In 0.1 M Bu4NPF6 DMSO the complex shows a series of redox couples associated with the Os3+/2+ and bipyridine ligands of the cationic [Os(bpy)3]2+ moiety and the tungsten-oxo framework of the associated Dawson parent heteropolyanion, [P2W18O62]6−. At this electrolyte concentration, the Os3+ redox form of the complex was seen to adsorb onto the electrode surface. When the electrolyte concentration is lowered to 0.01 M Bu4NPF6 in addition to the Os3+/2+ redox couple, the redox process associated with the [P2W18O62]8−/7− couple also exhibited properties indicating surface based processes were present. Electroactive films of the complex were formed on carbon macroelectrodes by the redox switching of the transition metal within the complex. Voltammetric investigations into the film's behaviour in a range of buffer solutions (pH 2.0, 4.5 and 7.0) were performed. The films were found to possess better stability in acidic pH and the same pH dependence for the tungsten-oxo framework of the heteropolyanions as in solution. Solid state electrochemical measurements on mechanically attached microparticles of the complex were performed, with the effect of both the nature and concentration of the aqueous electrolyte on this behaviour being investigated. Upon redox switching between the Os2+/3+ redox states, there is an associated insertion/expulsion of anions from/to the solution phase. Scanning electron micrographs of these solid state films were attained before and after redox cycling.  相似文献   

19.
Reactions of the ferrocene-phosphines FcPH2 and 1,1-Fc(PH2)2 with excess formaldehyde gives the new hydroxymethylphosphines FcP(CH2OH)2 1 and 1,1-Fc[P(CH2OH)2]2 2, respectively. Phosphine 1 is an air-stable crystalline solid, whereas 2 is isolated as an oil. Reaction of 1 with H2O2, S8 or Se gives the chalcogenide derivatives FcP(E)(CH2OH)2 (E=O, S or Se), whilst reaction of 2 with S8 gives 1,1-Fc[P(S)(CH2OH)2]2, which were fully characterised. Phosphine 1 was also characterised by an X-ray crystal structure determination.  相似文献   

20.
A new 3D coordination polymer [Cd2(L3)(BTC)(H2O)] (1) (HL3 = 3,5-bis(pyridin-3-ylmethoxy)benzoic acid, H3BTC = 1,3,5-benzenetricarboxylic acid), has been isolated under hydrothermal condition and characterized by single-crystal X-ray diffraction. Compound 1 is constructed from Cd2-based second building units (SBUs) [Cd2(CO2)3O4N2] and displays a 3D (3,4,7)-connected net with (42·6)(43·63)(45·611·85) topology. In addition, the photoluminescent spectra indicate compound 1 may be a good candidate for blue-luminescent materials.  相似文献   

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