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1.
A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N3O2] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H2DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H4DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C2H5OH)Cl] (1); [Er(DAPMBH)(H2O)Cl]·2C2H5OH (2); [Er(DAPMBH)(CH3OH)Cl] (3); [Er(DAPMBH)(CH3OH)(N3)] (4); [(Et3H)N]+[Er(H2DAPS)Cl2] (5); and [(Et3H)N]+[Y0.95Er0.05(H2DAPS)Cl2] (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1–6 were studied. The AC magnetic measurements revealed that most of Compounds 1–6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, Ueff ≈ 16–28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1–6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.  相似文献   

2.
The catalysts prepared sequentiallyvia the interaction of C3H5PdC5H5 with the surface of evacuated Pr4O7/C and reduction with H2 at 573 K, contain 20–30 Pd particles and Pr4O7 particles<20 . The catalysts obtained have two-order of magnitude higher specific activity in the CH3OH synthesis than Pd/C.  相似文献   

3.
Detailed quartet and doublet potential energy surfaces for the Ti+ + C3H8 → TiC3H6+ + H2 and Ti+ + C3H8 → TiC2H4+ + CH4 elimination reactions have been studied using density functional theory with B3LYP functional and ab initio coupled cluster CCSD(T) methods. Several H2 elimination and CH4 elimination reaction paths have been examined including the IRC following. In particular, the mechanisms involving, respectively, the H2TiC3H6+ and CH3TiHC2H4+ intermediates have been studied. Contribution to the Mark S. Gordon 65th Birthday Festschrift Issue.  相似文献   

4.
In the present study, we successfully prepared two different electrospun polyacrylonitrile (PAN) based-activated carbon nanofiber (ACNF) composites by incorporation of well-distributed Fe2O3 and Co3O4 nanoparticles (NPs). The influence of metal oxide on the structural, morphological, and textural properties of final composites was thoroughly investigated. The results showed that the morphological and textural properties could be easily tuned by changing the metal oxide NPs. Even though, the ACNF composites were not chemically activated by any activation agent, they presented relatively high surface areas (SBET) calculated by Brunauer–Emmett–Teller (BET) equation as 212.21 and 185.12 m2/g for ACNF/Fe2O3 and ACNF/Co3O4 composites, respectively. Furthermore, the ACNF composites were utilized as candidate adsorbents for CO2 and CH4 adsorption. The ACNF/Fe2O3 and ACNF/Co3O4 composites resulted the highest CO2 adsorption capacities of 1.502 and 2.166 mmol/g at 0 °C, respectively, whereas the highest CH4 adsorption capacities were obtained to be 0.516 and 0.661 mmol/g at 0 °C by ACNF/Fe2O3 and ACNF/Co3O4 composites, respectively. The isosteric heats calculated lower than 80 kJ/mol showed that the adsorption processes of CO2 and CH4 were mainly dominated by physical adsorption for both ACNF composites. Our findings indicated that ACNF-metal oxide composites are useful materials for designing of CO2 and CH4 adsorption systems.  相似文献   

5.
The deposition of diamondlike carbon (DLC) film and the measurements of ionic species by means of mass spectrometry were carried out in a CH4/N2 RF (13.56 MHz) plasma at 0.1 Torr. The film deposition rate greatly depended on both CH4/N2 composition ratio and RF power input. It was decreased monotonically as CH4 content decreased in the plasma and then rapidly diminished to negligible amounts at a critical CH4 content, which became large for higher RF power. The rate increased with increasing RF power, reaching a maximum value in 40% CH4 plasma. The predominant ionic products in CH4/N2 plasma were NH+ 4 and CH4N+ ions, which were produced by reactions of hydrocarbon ions, such as CH+ 3, CH+ 2, CH+ 5, and C2H+ 5 with NH3 molecules in the plasma. It was speculated that the production of NH+ 4 ion induced the decrease of C2H+ 5 ion density in the plasma, which caused a reduction in higher hydrocarbon ions densities and, accordingly, in film deposition rate. The N+ 2 ion sputtering also plays a major role in a reduction of film deposition rate for relatively large RF powers. The incorporation of nitrogen atoms into the bonding network of the DLC film deposited was greatly suppressed at present gas pressure conditions.  相似文献   

6.
Excess molar volumes V E and excess molar heat capacities C P E at constant pressure have been measured, at 25°C, as a function of composition for the four binary liquid mixtures propylene carbonate (4-methyl-1,3-dioxolan-2-one, C4H6O3; PC) + benzene (C6H6;B), + toluene (C6H5CH3;T), + ethylbenzene (C6H5C2H5;EB), and + p-xylene (p-C6H4(CH3)2;p-X) using a vibrating-tube densimeter and a Picker flow microcalorimeter, respectively. All the excess volumes are negative and noticeably skewed towards the hydrocarbon side: V E (cm3-mol–1) at the minimum ranges from about –0.31 at x1=0.43 for {x1C4H6O3+x2p-C6H4(CH3)2}, to –0.45 at x1=0.40 for {x1C4H6O3+x2C6H5CH3}. For the systems (PC+T), (PC+EB) and (PC+p-X) the C P E s are all positive and even more skewed. For instance, for (PC+T) the maximum is at x 1,max =0.31 with C P,max E =1.91 J-K–1-mol–1. Most interestingly, C P E of {x1C4H6O3+x2C6H6} exhibits two maxima near the ends of the composition range and a minimum at x 1,min =0.71 with C P,min E =–0.23 J-K–1-mol–1. For this type of mixture, it is the first reported case of an M-shaped composition dependence of the excess molar heat capacity at constant pressure.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990.  相似文献   

7.
The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H* over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^*, which reacted with adsorbed CO subsequently via CO^*+OH^* → CO2^*+H^*; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^*+2H^* → CH^*+OH^*. The formation of the surface species (CH) from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.  相似文献   

8.
Results of investigations of the adsorption and decomposition of methanol on the surface of transition metals such as Fe, Ni, Cu, Pd, Ag, Mo, W and Pt byuv and x-ray photoelectron spectroscopy, electron energy loss spectroscopy, Auger electron spectroscopy and thermal desorption spectroscopy have been reviewed. The first step in the decomposition of CH3OH on these metal surfaces is the formation of the methoxy species, OCH3 radical. In the case of Fe, Mo and W, complete decomposition of CH3OH occurs leaving CO(β), H2 and CH4 on the surface. Dissociation proceeds upto CO(α) and H2 on the surface of Ni, Pd and Pt whereas on Ag and Cu, selective oxidation of CH3OH to H2CO is preferred. The difference in the reactivity of metals towards CH3OH is rationalised from the heats of adsorption of O2, CO and H2 on these metals. Contribution No. 253 from the Solid State and Structural Chemistry Unit.  相似文献   

9.
Viscosities for aqueous NH4Cl and tracer diffusion coefficients for22Na+,36Cl, HTO, and CH3OH, acetone and dimethylformamide (all14C-labelled) in NH4Cl supporting electrolyte are reported for 25°, together with tracer diffusion coefficients for22Na+,36Cl, and14CH3OH in 1M KI, and for14CH3OH in 1M MgCl2. The diffusion coefficient of HTO in NH4Cl solutions is slightly larger, for most of the concentration range investigated (0.05 to 4.5 M), than the value for pure water and is almost unaffected by the supporting electrolyte up to about 4M. Similar behavior is shown by CH3OH, acetone and dimethylformamide in NH4Cl solutions. Onsager limiting law behavior is approached by Cl at NH4Cl concentrations in the 0.05–0.1M region but at much lower concentrations by Na+.  相似文献   

10.
Magnetic nanocapsules were constructed by fabricating nanometer scaled C60-like “Keplerate” type {Mo72Fe30} with molecular formula [Mo72VIFe30IIIO252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91]ca.150H2O into nanocapsule shells using the LbL technique. The morphology of the obtained hybrid nanocapsules was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Shell thickness of the {Mo72Fe30}-embedded nanocapsules can be tailored at the nanometer level more precisely than other nanoparticle-embedded capsules due to the homogeneous diameter and surface charges of {Mo72Fe30}. Interestingly, the {Mo72Fe30}-embedded nanocapsules could be separated and aligned under a circumstance of magnetic field, though {Mo72Fe30} is a paramagnetic molecule. This is the first time to fabricate hybrid magnetic materials containing {Mo72Fe30} using LbL technique. The obtained nanocapsules can be a good candidate for bioseparation as well as targeted delivery.  相似文献   

11.
Reaction of cis-[Mo(NCMe)2(CO)2(η5-L)][BF4] (L=C5H5 or C5Me5) with 1-acetoxybuta-1,3-diene gives the cationic complexes [Mo{η4-syn-s-cis-CH2CHCHCH(OAc)}(CO)2(η5-L)][BF4], which, on reaction with aqueous NaHCO3/CH2Cl2, afford good yields of the anti-aldehyde substituted complexes [Mo{η3-exo-anti-CH2CHCH(CHO)}(CO)2(η5-L)] 2 (L=C5Me5), 4 (L=C5H5)]. The corresponding η5-indenyl substituted complex 5 was prepared by protonation (HBF4·OEt2) of [Mo(η3-C3H5)(CO)2(η5-C9H7)] followed by addition of CH2=CHCH=CH(OAc) and hydrolysis (aq. NaHCO3/CH2Cl2). An X-ray crystallographic study of complex 2 confirmed the structure and showed that there is a contribution from a zwitterionic form involving donation of electron density from the molybdenum to the aldehyde carbonyl group. Treatment of 2 and 4, in methanol solution, with NaBH4 afforded the alcohols [Mo{η3-exo-anti-CH2CHCHCH2(OH)}(CO)2(η5-L)] [6 (L=C5H5), 8 (L=C5Me5)]; however, prolonged (30 h) reaction with NaBH4/MeOH surprisingly gave good yields of the methoxy-substituted complexes [Mo{η3-exo-anti-CH2CHCHCH2(OMe)}(CO)2(η5-L)] [7 (L=C5H5), 9 (L=C5Me5)], the structure of 7 being confirmed by single crystal X-ray crystallography. This methoxylation reaction can be explained by coordination of the hydroxyl group present in 6 and 8 onto B2H6 to form the potential leaving group HOBH3, which on ionisation affords [Mo(η4-exo-buta-1-3-diene)(CO)2(η5-L)]+ which is captured by reaction with OMe. Complex 8 is also formed in good yield on reaction of 2 with HBF4·OEt2 followed by treatment of the resulting cation [Mo{η4-exo-s-cis-syn-CH2CHCHCH(OH)}(CO)2(η5-C5Me5)][BF4] with Na[BH3CN]. Reaction of 4 with the Grignard reagents MeMgI, EtMgBr or PhMgCl afforded moderate yields of the alcohols [Mo{η3-exo-anti-CH2CHCHCH(OH)R}(CO)2(η5-C5H5)] [11 (R=Me), 12 (R=Et), 13 (R=Ph)]. Similarly, treatment of 2 with MeLi gave the corresponding alcohol 14. An attempt to carry out the Oppenauer oxidation [Al(OPr′)3/Me2CO] of 11 resulted in an elimination reaction and the formation of the η3-s-pentadienyl complex [Mo{η3-exo-anti-CH2CHCH(CHCH2)}(CO)2(η5-C5H5)], which was structurally identified by X-ray crystallography. Interestingly, oxidation of 6 with [Bu4nN][RuO4]/morpholine-N-oxide affords the aldehyde complex, 4 in good yield. Finally, reaction of 11 with [NO][BF4] followed by addition of Na2CO3 affords the fur-3-ene complex [Mo{η2-
(H)Me}(CO)(NO)(η5-C5H5)].  相似文献   

12.
29Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O)4/2 and CH3Si(O)3/2 units, (CH3) n Si8O 20 – n /(8 – n) – (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that 29Si NMR peaks due to Si(OSi)3(O) units shift to lower frequencies by replacement of the adjacent Si(O)4/2 units by CH3Si(O)3/2 units, in other words, with increasing m value in Si[OSi(O)3]3 – m [OSi(CH3) (O)2] m (O) (m=0–2). Peaks from CH3 Si(OSi)3 units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH3Si(O)3/2 units in the cubic octameric siloxane framework of (CH3) n Si8O 20 – n /(8 – n) – (n=2, 3), for both of which three isomers are present, have been estimated.  相似文献   

13.
The main objective of this study was to develop a thermodynamic model for predicting Cr(III) behavior in concentrated NaOH and in mixed NaOH–NaNO3 solutions for application to developing effective caustic leaching strategies for high-level nuclear waste sludges. To meet this objective, the solubility of Cr(OH)3(am) was measured in 0.003 to 10.5 m NaOH, 3.0 m NaOH with NaNO3 varying from 0.1 to 7.5 m, and 4.6 m NaNO3 with NaOH varying from 0.1 to 3.5 m at room temperature (22 ± 2°C). A combination of techniques, X-ray absorption spectroscopy (XAS) and absorptive stripping voltammetry analyses, were used to determine the oxidation state and nature of aqueous Cr. A thermodynamic model, based on the Pitzer equations, was developed from the solubility measurements to account for dramatic increases in aqueous Cr with increases in NaOH concentration. The model includes only two aqueous Cr species, Cr(OH) 4 and Cr2O2(OH) 4 (although the possible presence of a small percentage of higher oligomers at >5.0 m NaOH cannot be discounted) and their ion–interaction parameters with Na+. The logarithms of the equilibrium constants for the reactions involving Cr(OH) 4 [Cr(OH)3(am) + OH Cr(OH) 4 ] and Cr2O2(OH) 4 2– [2Cr(OH)3(am) + 2OH Cr2O2(OH) 4 2– + 2H2O] were determined to be –4.36 ± 0.24 and –5.24 ± 0.24, respectively. This model was further tested and provided close agreement between the observed Cr concentrations in equilibrium with Cr(OH)3(am) in mixed NaOH–NaNO3 solutions and with high-level tank sludges leached with and primarily containing NaOH as the major electrolyte.  相似文献   

14.
Thermal treatment of SiO2-aerogel in inert atmosphere, in contrary to oxidizing atmosphere, yields a series of gas products with great range of mole masses (12–154 g mol–1) and every product has specific way of evolving. These substances are represented by CO, CO2, CH4, CH3OH, C2H6, C2H4 and aromates. Part of evolving products, which are formed during catalytic condensation, is trapped under the surface and after carbonisation it causes opacity of surface layer of aerogel.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

15.
The purpose of this article is to show that CHELP, CHELPG, and Merz and Kollman undergo error for the charge on atoms of HCOO (H2O) n for n = 1 6. We also demonstrate that the CHELP, CHELPG, and Merz and Kollman show error for the tendency toward change in the charges on carbons for CH3NH+ 3 (CH3)2NH+ 2 (CH3)3NH+ (CH3)4N+.  相似文献   

16.
Ionic liquid A327H+Cl was generated by reaction of tertiary amine A327 and HCl, and the liquid-liquid extraction of indium(III) from the HCl medium by this ionic liquid dissolved in Solvesso 100 was investigated. The extraction reaction is exothermic. The numerical analysis of indium distribution data suggests the formation of A327H+InCl4 in the organic phase. The results derived from indium(III) extraction have been implemented in a supported liquid membrane system. The influence of the stirring speed (600–1200 min−1), carrier concentration (2.5–20% v/v) in the membrane phase, and indium concentration (0.01–0.2 g/L) in the feed phase on metal transport have been investigated.  相似文献   

17.
This paper is a detailed review of the chemistry of medium-size reactive systems using the following hydrogen abstraction reactions with ethane, X + C2H6 → HX + C2H5; X ≡ H, F(2P), Cl(2P), O(3P) and OH, and focusing attention mainly on the theoretical developments. These bimolecular reactions range from exothermic to endothermic systems and from barrierless to high classical barriers of activation. Thus, the topography of the reactive systems changes from reaction to reaction with the presence or not of stabilized intermediate complexes in the entrance and exit channels. The review begins with some reflections on the inherent problems in the theory/experiment comparison. When one compares kinetics or dynamics theoretical results with experimental measures, one is testing both the potential energy surface describing the nuclei motion and the kinetics or dynamics method used. Discrepancies in the comparison may be due to inaccuracies of the surface, limitations of the kinetics or dynamics methods, and experimental uncertainties that also cannot be ruled out. The paper continues with a detailed review of some bimolecular reactions with ethane, beginning with the reactions with hydrogen atoms. The reactions with halogens present a challenge owing to the presence of stabilized intermediate complexes in the entrance and exit channels and the influence of the spin-orbit states on reactivity. Reactions with O(3P) atoms lead to three surfaces, which is an additional difficulty in the theoretical study. Finally, the reactions with the hydroxyl radical correspond to a reactive system with ten atoms and twenty-four degrees of freedom. Throughout this review, different strategies in the development of analytical potential energy surfaces describing these bimolecular reactions have been critically analyzed, showing their advantages and limitations. These surfaces are fitted to a large number of ab initio calculations, and we found that a huge number of calculations leads to accurate surfaces, but this information does not guarantee that the kinetics and dynamics results match the experimental measurements.  相似文献   

18.
Raman and infrared spectra of polycrystalline6Li2C2O4 and7Li2C2O4 have been investigated in the wavenumber region from 1,800 to 40 cm–1. The internal C2O4 –2 vibrations have been studied on the basis of a D2h molecular structure and the correlation field splittings have been found to be about 40 cm–1 for the stretching modes and about 15 cm–1 for the bending modes. The external vibrations of the Li+ and C2O4 –2 sites have been discussed by considering the results of the factor group analysis and the6Li/7Li isotope effect on the normal vibrations.
Raman- und Infrarot-Spektren von6Li2C2O4 und7Li2C2O4
Zusammenfassung Es wurdenRaman- und IR-Spektren von polykristallinem6Li2C2O4 und7Li2C2O4 im Bereich der Wellenzahlen von 1800 bis 40 cm–1 untersucht. Die internen Schwingungen wurden auf der Basis einer D2h Molekülstruktur analysiert. Für die Streckschwingungen wurde eine Korrelationsaufspaltung von etwa 40 cm–1 gefunden, für die Deformationsschwingungen etwa 15 cm–1. Die Diskussion der externen Schwingungen von Li+ und C2O4 –2 erfolgte unter Berücksichtigung der Resultate der Faktorgruppenanalyse und des6Li/7Li Isotopeneffekts auf die Normalschwingungen.
  相似文献   

19.
以Fe(NO3)3·9H2O和正硅酸乙酯(TEOS)为原料, 通过溶胶-凝胶法和辅助模板法分别制备了纳米α-Fe2O3和SiO2, 并对所合成样品进行了粉末X射线衍射(XRD)和BET表征. 使用自动电位滴定仪测定了α-Fe2O3/SiO2纳米颗粒混合体系的表面酸碱性质. 研究了在不同pH下α-Fe2O3/SiO2混合体系对Cu2+、Pb2+、Zn2+离子的吸附行为. 基于上述实验数据, 用WinSGW软件计算了α-Fe2O3/SiO2混合体系表面酸碱配位常数, 并得出结论: α-Fe2O3/SiO2混合体系表面反应为单一脱质子反应≡XOH ⇔ ≡XO-+ H+(lg K = -8.19±0.15), 明显区别于同时具有加质子和脱质子反应的α-Fe2O3/SiO2/γ-Al2O3, α-Fe2O3/γ-Al2O3和SiO2/γ-Al2O3等纳米颗粒混合体系. 在此基础上拟合得到α-Fe2O3/SiO2混合体系吸附重金属离子Cu2+、Pb2+、Zn2+的表面络合反应平衡常数分别为:
≡XOH + M2+ ⇔ ≡XOM++ H+ [lg K = -3.1, -3.6, -3.8 (M = Cu, Pb, Zn)].
≡XOH+M2++H2O ⇔≡XOMOH+2H+[lg K = -8.8, -8.0, -10.5 (M = Cu, Pb, Zn)]  相似文献   

20.
The FT IR and FT Raman spectra of Co(en)3Al3P4O16 · 3H2O (compound I) and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O (compound II) are recorded and analysed based on the vibrations of Co(en)33+, Co(NH3)63+, NH4+, Al---O---P, PO3, PO2 and H2O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH2 deformation Fermi resonates with its symmetric stretching vibration. The NH4 ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.  相似文献   

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