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1.
Herein we report a novel magnetically recoverable lanthanum hydroxide nanoparticles for oxidative synthesis of nitriles directly from corresponding alcohols with ammonia as nitrogen source. The procedure for the preparation and characterization of La(OH)3/Fe3O4 magnetic nanoparticles were investigated and the scope and generality of the method was explored for a series of structurally diverse primary alcohols with electron‐donating and electron‐withdrawing groups. The best result was observed when 5 mol% of La with respect to the benzyl alcohol was used at reflux condition under O2 atmosphere. The La(OH)3/Fe3O4 magnetic nanoparticles could be easily isolated from the reaction mixture with an external magnet and reused at least 5 times without significant loss in activity.  相似文献   

2.
Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta6O19]8−, has yielded a new phase, La2Ta2O7(OH)2. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 °C, which converts to a previously reported LaTaO4 polymorph at 1200 °C. The stabilities of La2Ta2O7(OH)2 (LaTa−OH), the intermediate LaTaO4 polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be −87.1±9.6, −94.9±8.8, and −93.1±8.7 kJ/mol for LaTa−OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO4 and Ln2Ta2O7(OH)2 analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases.  相似文献   

3.
An on-line solution-reaction isoperibol calorimeter has been constructed. The performance of the apparatus was evaluated by measuring the molar enthalpy of solution of KCl in water at 298.15 K. The uncertainty and the inaccurary of the experimental results were within ±0.3% compared with the recommended reference data. Using the calorimeter, the molar enthalpies of reaction for the following two reactions: LaCl3·7H2O(s)+2Hhq(s)+NaAc(s)=La(hq)2Ac(s)+NaCl(s)+2HCl(g)+7H2O(l) and PrCl3·6H2O(s)+2Hhq(s)+NaAc(s)=Pr(hq)2Ac(s)+NaCl(s)+2HCl(g)+6H2O(l), were determined at T=298.15 K, as −(78.3±0.6) and −(97.3±0.5) kJ mol−l, respectively. From the above molar enthalpies of reaction and other auxiliary thermodynamic quantities, the standard molar enthalpies of formation of La(hq)2Ac and Pr(hq)2Ac, at T=298.15 K, have been derived to be −(1535.5±0.7) and −(1536.7±0.6) kJ mol−l, respectively.  相似文献   

4.
Two new hydrated borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]·1.5H2O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn8[(BO3)3O2(OH)3] crystallizes in a non-centrosymmetric space group R32 with a=8.006(2) Å, c=17.751(2) Å, Z=3 and Pb[B5O8(OH)]·1.5H2O in a triclinic space group P1¯ with a=6.656(2) Å, b=6.714(2) Å, c=10.701(2) Å, α=99.07(2)°, β=93.67(2)°, γ=118.87(1)°, Z=2. Zn8[(BO3)3O2(OH)3] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons 1[Zn8O15(OH)3]17− that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional 3[Zn8O11(OH)3]9− framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B5O8(OH)]·1.5H2O is a layered compound containing double ring [B5O8(OH)]2− building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center-related layers are stacked along the c-axis and held together by interlayer Pb2+ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO3 and OH groups in Zn8[(BO3)3O2(OH)3], and BO3, BO4, OH groups as well as guest water molecules in Pb[B5O8(OH)]·1.5H2O.  相似文献   

5.
A pure hydrated potassium borate K2B5O8(OH)·2H2O has been synthesized under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, XRD, FT-IR, Raman spectra and DTA-TG. The crystal structure consists of two K-O polyhedra and [B5O8(OH)]2− polyborate anion. The enthalpy of formation was determined to be −4772.6 ± 4.0 kJ mol−1 by solution calorimetry.  相似文献   

6.
Two pure strontium borates SrB2O4·4H2O and SrB2O4 have been synthesized and characterized by means of chemical analysis and XRD, FT-IR, DTA-TG techniques. The molar enthalpies of solution of SrB2O4·4H2O and SrB2O4 in 1 mol dm−3 HCl(aq) were measured to be −(9.92 ± 0.20) kJ mol−1 and −(81.27 ± 0.30) kJ mol−1, respectively. The molar enthalpy of solution of Sr(OH)2·8H2O in (HCl + H3BO3)(aq) were determined to be −(51.69 ± 0.15) kJ mol−1. With the use of the enthalpy of solution of H3BO3 in 1 mol dm−3 HCl(aq), and the standard molar enthalpies of formation for Sr(OH)2·8H2O(s), H3BO3(s), and H2O(l), the standard molar enthalpies of formation of −(3253.1 ± 1.7) kJ mol−1 for SrB2O4·4H2O, and of −(2038.4 ± 1.7) kJ mol−1 for SrB2O4 were obtained.  相似文献   

7.
The hydridic reactivity of the complex W(CO)(H)(NO)(PMe3)3 (1) was investigated applying a variety of protic donors. Formation of organyloxide complexes W(CO)(NO)(PMe3)3(OR) (R = C6H5 (2), 3,4,5-Me3C6H2 (3), CF3CH2 (4), C6H5CH2 (5), Me (6) and iPr (7)) and H2 evolution was observed. The reactions of 1 accelerated with increasing acidity of the protic donor: Me2CHOH (pKa = 17) < MeOH (pKa = 15.5) < C6H5CH2OH (pKa = 15) < CF3CH2OH (pKa = 12.4) < C6H2Me3OH (pKa = 10.6) < C6H5OH (pKa = 10).Regioselective hydrogen bonding of 1 was probed with two of the protic donors furnishing equilibrium formation of the dihydrogen bonded complexes ROH···HW(CO)(NO)(PMe3)3 (R = 3,4,5-Me3C6H2,3a and iPr, 7a) and the ONO hydrogen bonded species ROH···ONW(CO)(H)(PMe3)3 (R = C6H2Me3,3b and iPr, 7b) which were studied in hexane and d8-toluene solutions using variable temperature IR and NMR spectroscopy. Quantitative IR experiments at low temperatures using 3,4,5-trimethylphenol (TMP) confirmed the two types of competitive equilibria: dihydrogen bonding to give 3aH1 = −5.8 ± 0.4 kcal/mol and ΔS1 = −15.3 ± 1.4 e.u.) and hydrogen bonding to give 3b (ΔH2 = −2.8 ± 0.1 kcal/mol and ΔS2 = −5.8 ± 0.3 e.u.). Additional data for the hydrogen bonded complexes 3a,b and 7a,b were determined via NMR titrations in d8-toluene from the equilibrium constants Kδ) and KR1) measuring either changes in the chemical shifts of HW(Δδ) or the excess relaxation rates of HWR1) (3a,b: ΔHδ) = −0.8 ± 0.1 kcal/mol; ΔSδ) = −1.4 ± 0.3 e.u. and ΔHR1) = −5.8 ± 0.4 kcal/mol; ΔSR1) = −22.9 ± 1.9 e.u) (7a,b: ΔHδ) = −2.3 ± 0.2 kcal/mol; ΔSδ) = −11.7 ± 0.9 e.u. and ΔHR1) = −2.9 ± 0.2 kcal/mol; ΔSR1) = −14.6 ± 1.0 e.u). Dihydrogen bonding distances of 1.9 Å and 2.1 Å were derived for 3a and 7a from the NMR excess relaxation rate measurements of HW in d8-toluene. An X-ray diffraction study was carried out on compound 2.  相似文献   

8.
Hydrated layered crystalline barium phenylarsonate, Ba(HO3AsC6H5)2·2H2O was used as host for intercalation of n-alkylmonoamine molecules CH3(CH2)n-NH2 (n = 1-4) in aqueous solution. The amount intercalated (nf) was followed batchwise at 298 ± 1 K and the variation of the original interlayer distance (d) for hydrated barium phenylarsonate (1245 ppm) was followed by X-ray powder diffraction. Linear correlations were obtained for both d and nf as a function of the number of carbon atoms in the aliphatic chain (nc): d = (2225 ± 32) + (111 ± 11)nc and nf = (2.28 ± 0.15) − (11.50 ± 0.03)nc. The exothermic enthalpies of intercalation increased with nc, which was derived from the monomolecular amine layer arrangements with the longitudinal axis inclined by 60° to the inorganic sheets. The intercalation was followed by titration with amine at the solid/liquid interface and gave the enthalpy/number of carbons correlation: ΔH = −(7.25 ± 0.40) − (1.67 ± 0.10)nc. The negative Gibbs free energies and positive entropic values reflect the favorable host/guest intercalation processes for this system.  相似文献   

9.
In this study, the tin(II) oxy-hydroxychloride Sn21O6Cl16(OH)14 has been synthesised and investigated. This compound is the synthetic equivalent of mineral abhurite, which was discovered in 1985 as a tin corrosion product formed on the surface of tin ingots after long immersion in seawater. The Mössbauer parameters of Sn21O6Cl16(OH)14 determined at various temperatures are reported and discussed for the first time. At room temperature, the isomer shift and the quadrupole splitting are, respectively, δ=3.22 mm s−1 and Δ=1.71 mm s−1, relative to the centroid of the spectrum of BaSnO3. The Mössbauer recoil-free fraction has been also evaluated over a wide range of temperature. At 300 K, the recoil-free fraction of Sn21O6Cl16(OH)14 is f300=0.09±0.02.  相似文献   

10.
Nanocrystalline lanthanum hexaboride (LaB6) with mean particle size of 30 nm has been successfully synthesized at 400 °C in an autoclave starting from metallic magnesium powder, NaBH4 and LaCl3. In this case, by using B2O3 instead of NaBH4, LaB6 nanocubes with mean size of ∼200 nm were formed at 500 °C. The X-ray diffraction (XRD) pattern can be indexed as cubic LaB6 with the lattice constant of a=4.151 Å for LaB6 nanoparticles and 4.154 Å for LaB6 nanocubes. An atomic ratio of La and B as 1:5.94 was determined from EDS for LaB6 nanoparticles. XPS data of LaB6 nanocubes indicate the atomic ratio of La to B as 1:5.95. Raman spectra indicate the formation of LaB6.  相似文献   

11.
The enthalpies of solution of NaRb[B4O5(OH)4]·4H2O in approximately 1 mol dm−3 aqueous hydrochloric acid and of RbCl in aqueous (hydrochloric acid + boric acid + sodium chloride) were determined. From these results and the enthalpy of solution of H3BO3 in approximately 1 mol dm−3 HCl(aq) and of sodium chloride in aqueous (hydrochloric acid + boric acid), the standard molar enthalpy of formation of −(5128.02 ± 1.94) kJ mol−1 for NaRb[B4O5(OH)4]·4H2O was obtained from the standard molar enthalpies of formation of NaCl(s), RbCl(s), H3BO3(s) and H2O(l). The standard molar entropy of formation of NaRb[B4O5(OH)4]·4H2O was calculated from the Gibbs free energy of formation of NaRb[B4O5(OH)4]·4H2O computed from a group contribution method.  相似文献   

12.
A new sodium gallophosphate, NaGa2(OH)(PO4)2, has been obtained by hydrothermal synthesis under autogeneous pressure at 473 K. It crystallizes in the P21/n space group with the cell parameters a=8.9675(8) Å, b=8.9732(5) Å, c=9.2855(7) Å, β=114.812(6)°, V=678.2 Å3 (Z=4). In its original three-dimensional framework, monophosphate groups share their apices with [Ga4O16(OH)2] tetrameric units, which are built from two GaO5(OH) octahedra and two GaO4(OH) trigonal bipyramids. The sodium cations are located in tunnels running along a, whereas the tunnels running along b are empty.  相似文献   

13.
A new hydrated borate compound, [NH3CH2CHCH3NH3]][B8O11(OH)4]·H2O 1, has been synthesized in the presence of 1,2-diaminopropane acting as a structure-directing agent under mild conditions. Its structure was determined by single crystal X-ray diffraction and further characterized FTIR, elemental analysis, powder X-ray diffraction and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system, space group P21/c (No. 14), a=10.0787(7) Å, b=8.8482(6) Å, c=19.3097(4) Å, β=91.352(6)°, V=1721.53(2) Å3, and Z=4. The structure consists of infinite open-branched borate chains constructed from [B3O6(OH)] units, onto which the [B5O7(OH)3] groups are grafted. It represents the first example of one-dimensional borate templated by an organic amine. The adjacent borate chains are further linked together by extensive hydrogen bonds to form a 3D supramolecular network. The diprotonated organic amines and guest water molecules are filled in the free space of the hydrogen-bonded network and interact with the inorganic framework by extensive hydrogen bonds.  相似文献   

14.
The reaction of [60]fullerene with primary aliphatic alcohols (ROH, R = Et, Me, Pr) mediated by cerium(IV) ammonium nitrate [(NH4)2Ce(NO3)3] affords the corresponding alkoxy-derivatives with a hydroxy group, C60(OR)x(OH) (x = 3, 4) in high yield. The reaction is characterized by a free radical mechanism confirmed by an EPR study of the alkoxy fullerenyl radical (g = 2.0023).  相似文献   

15.
A series of mononuclear complexes based on lanthanide ions has been synthesized and X-ray characterized. The compounds [LnIIIL2(NO3)3(H2O)2] (Ln = La, Ce, Pr, Nd, Sm, Gd and Tm; L = 2,6-bis(2-formylphenoxymethyl)pyridine) are found to be isomorphous and isostructural. Ligand L systematically coordinates through one carbonyl functionality, and the resulting complexes are placed on a twofold axis in crystals belonging to C2/c space-group. Emission spectra for Ln = La, Pr, Nd revealed a correlation between the Ln–O coordination bond length and the photoluminescent properties of the complexes, in line with a Förster–Dexter mechanism for intramolecular energy transfer. Ligand L is therefore a suitable sensitizer for lanthanide ions.  相似文献   

16.
The family of hydroxymonophosphates of generic formula AMIII(PO3(OH))2 has been revisited using hydrothermal techniques. Four new phases have been synthesized: CsIn(PO3(OH))2, RbFe(PO3(OH))2, RbGa(PO3(OH))2 and RbAl(PO3(OH))2. Single crystal diffraction studies show that they exhibit two different structural types from previously observed other phases with A=H3O, NH4, Rb and M=Al, V, Fe. The “Cs-In” and “Rb-Fe” phosphates crystallize in the triclinic space group , with the cell parameters a=7.4146(3) Å, b=9.0915(3) Å, c=9.7849(3) Å, α=65.525(3)°, β=70.201(3)°, γ=69.556(3)° and V=547.77(4) Å3 (Z=3) for CsIn(PO3(OH))2 and a=7.2025(4) Å, b=8.8329(8) Å, c=9.4540(8) Å, α=65.149(8)°, β=70.045(6)°, γ=69.591(6)° and V=497.44(8) Å3 (Z=3) for α-RbFe(PO3(OH))2. The “Rb-Al” and “Rb-Ga” phosphates crystallize in the Rc space group, with a=8.0581(18) Å and c=51.081(12) Å (V=2872.5(11) Å3 and Z=18) for RbAl(PO3(OH))2 and a=8.1188(15) Å and c=51.943(4) Å (V=2965(8) Å and Z=18) for RbGa(PO3(OH))2. These two structural types are closely related. Both are built up from MIIIO6 octahedra sharing their apices with PO3(OH) tetrahedra to form [M3(PO3OH)6] units, but the latter exhibits a different configuration of their tetrahedra. The three-dimensional host-lattices result from the connection of the [M3(PO3OH)6] units and they present numerous intersecting tunnels containing the monovalent cations.  相似文献   

17.
The Co2−xCux(OH)AsO4 (x=0 and 0.3) compounds have been synthesized under mild hydrothermal conditions and characterized by X-ray single-crystal diffraction and spectroscopic data. The hydroxi-arsenate phases crystallize in the Pnnm orthorhombic space group with Z=4 and the unit-cell parameters are a=8.277(2) Å, b=8.559(2) Å, c=6.039(1) Å and a=8.316(1) Å, b=8.523(2) Å, c=6.047(1) Å for x=0 and 0.3, respectively. The crystal structure consists of a three-dimensional framework in which M(1)O5-trigonal bipyramid dimers and M(2)O6-octahedral chains (M=Co and Cu) are present. Co2(OH)AsO4 shows an anomalous three-dimensional antiferromagnetic ordering influenced by the magnetic field below 21 K within the presence of a ferromagnetic component below the ordering temperature. When Co2+ is partially substituted by Cu2+ions, Co1.7Cu0.3(OH)AsO4, the ferromagnetic component observed in Co2(OH)AsO4 disappears and the antiferromagnetic order is maintained in the entire temperature range. Heat capacity measurements show an unusual magnetic field dependence of the antiferromagnetic transitions. This λ-type anomaly associated to the three-dimensional antiferromagnetic ordering grows with the magnetic field and becomes better defined as observed in the non-substituted phase. These results are attributed to the presence of the unpaired electron in the dx2y2 orbital and the absence of overlap between neighbour ions.  相似文献   

18.
Crea F  Milea D  Sammartano S 《Talanta》2005,65(1):229-238
In order to analyze the formation of hetero-metal polynuclear hydrolytic species, in this paper, we reported some results of an investigation (at I = 0.16 mol L−1 in NaNO3, at t = 25 °C by potentiometry, ISE-H+, glass electrode) on the hydrolysis of several mixtures (in different ratios) of two couples of cations: dioxouranium(VI)/copper(II) and dioxouranium(VI)/diethyltin(IV). The elevated total concentrations of cations 0.005 ≤ ΣCM mol L−1 ≤ 0.05) adopted in these measurements induced us to study again the hydrolysis of uranyl, for which no suitable literature data are available in these particular experimental conditions. All measurements were performed by two different operators, using completely independent instruments and reagents. Many different speciation models were considered in the calculations, including the simultaneous refinement of homo- and hetero-metal species, and a statistical analysis of obtained results was proposed too. Main results can be summarized as follows: UO22+ and Cu2+ form three hetero-metal polynuclear hydrolytic species [(UO2)Cu(OH)3+, (UO2)Cu2(OH)2+ and (UO2)2Cu4(OH)2+, with log βpqr = −2.93 ± 0.01, −7.34 ± 0.03 and −13.78 ± 0.03, respectively], all those common to their simple speciation without the other cation; UO22+ and (C2H5)2Sn2+ form seven mixed hydrolytic species [(UO2)(DET)(OH)3+, (UO2)(DET)2(OH)2+, (UO2)2(DET)4(OH)2+, (UO2)(DET)24(OH)2+, (UO2)2(DET)+5(OH), (UO2)(DET)2+5(OH) and (UO2)2(DET)7(OH), with log βpqr = −2.5 ± 0.2, −4.74 ± 0.02, −10.70 ± 0.06, −10.34 ± 0.03, −15.70 ± 0.06, −15.58 ± 0.06 and −27.9 ± 0.1, respectively] that are of the same kind of those formed by uranyl; formation of mixed hydrolytic species causes a significant enhancement of the percentage of hydrolyzed metal cations, modifying the solubility and, therefore, the bioavailability of these cations. We also determined, for dioxouranium(VI)/copper(II) system, the corresponding complex formation enthalpies and entropies by direct calorimetric measurements. We obtained ΔH112 = 47.9 ± 0.6 and ΔH214 = 92.9 ± 0.5 kJ mol−1, TΔS112 = 6 ± 1 and TΔS214 = 14 ± 1 kJ mol−1 (±S.D.), respectively, for the formation of (UO2)(Cu)2(OH)2+ and (UO2)2(Cu)4(OH)2+ species (according to reaction 2). We also calculated the single enthalpic and entropic contributes to the extra-stability that these species show with respect to the corresponding homo polynuclear ones.  相似文献   

19.
CTAB-Mn3O4 nanocomposites: Synthesis,NMR and low temperature EPR studies   总被引:1,自引:0,他引:1  
We are reporting on the synthesis of Mn3O4 nanoparticles and CTAB-Mn3O4 nanocomposites via a sonochemical route using MnCl2, ethanol, NaOH and CTAB. The crystalline phase was identified as Mn3O4. The crystallite size of the CTAB-Mn3O4 nanocomposite was identified as 13 ± 5 nm from X-ray line profile fitting and the particle size from TEM was 107.5 ± 1.4 nm. The interaction between CTAB and the Mn3O4 nanoparticles was investigated by FTIR and 1H NMR spectroscopies. Two different magnetic phase transitions were observed for both samples below the Curie temperature (43 °C) by using a low temperature Electron Paramagnetic Resonance (EPR) technique. Also we determined the effect of the capping with CTAB on the reduction in absorbed power.  相似文献   

20.
Direct treatment of HOdbp (= 2,6-dibenzylphenol) with strontium or barium metal in the absence of solvent at high temperature provides the corresponding phenolates Sr(Odbp)2 and Ba(Odbp)2. Recrystallisation of Ba(Odbp)2 from THF gave a good yield of the crystalline dimer [Ba(Odbp)2(THF)]2 · 2THF. Attempted recrystallisation of Sr(Odbp)2 from THF mostly yielded microcrystalline material characterized as [Sr(Odbp)2]n but on one occasion gave a small crop of crystalline [Sr9(Odbp)8(O2SiMe2)4(OH)2(THF)6(OH2)2] · 6THF derived from the adventitious reaction of Sr(Odbp)2 with dimethylsilicone grease ({OSiMe2}). In the solid-state [Ba(Odbp)2(THF)]2 · 2THF displays significant intramolecular Ba?π-arene interactions with the pendant benzyl substituents. [Sr9(Odbp)8(O2SiMe2)4(OH)2(THF)6(OH2)2] · 6THF features a square prismatic [Sr(O2SiMe2)4]6− core capped by two inverse crown-like square [Sr4(Odbp)4(OH)(L)4]3+ units, where L = OH2 or THF, that are staggered with respect to the cuboidal core.  相似文献   

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