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1.
A new series of dioxouranium(VI) complexes of a potential ONNO tetradentate donor 2-aminobenzoylhydrazone of butane-2,3-dione
(L1H2) have been synthesized. At pH 2·5–4·0, the donor (L1H2) reacts in the keto form and complexes of the type [UO2(L1H2)(X)2] (X−=Cl−, Br−, NO
3
−
, NCS−, ClO
4
−
, CH3COO−, 1/2SO
4
2−
) are obtained. At higher pH (6·5–7), the complex of the enol form having the formula [UO2(L1)(H2O)] has been isolated. On reaction with a monodentate lewis base (B), both types of complexes yield adducts of the type [UO2(L1)(B)]. All these complexes have been characterised adequately by elemental analyses and other standard physicochemical techniques.
Location of the bonding sites of the donor molecule around the uranyl ion, status of the uranium-oxygen bond and the probable
structure of the complexes have also been discussed. 相似文献
2.
The catalytic hydrogenation of an optically active mixture of (−)-menthone and (+)-isomenthone was studied. The catalysts
Raney nickel and Ni/SiO2 were used for these hydrogenations. Catalysts modified with (2R,3R)-(+)-tartaric acid were tested as well. Various non-equilibrium mixtures of isomers were produced by means of these reactions,
especially mixtures containing the less stable menthol isomers, (+)-neomenthol and (+)-neoisomenthol. (−)-Menthol was produced
during these reactions to a limited extent, the production of (−)-isomenthol was barcly existent. Isomerization of (−)-menthone
and (+)-isomenthone occurred during these reactions. Isomerizations among individual isomers were barely detectable. The catalysts
used showed a very low activity under the given reaction conditions. 相似文献
3.
Intramolecular metal-ligand OH/π (MLOH/π) and metal-ligand NH/π (MLNH/π) interactions in transition metal complexes between
aqua or ammine ligand and ligand containing a C6-aromatic ring were investigated in crystal structures deposited in the Cambridge
Structural Database (CSD). These intramolecular interactions appear in 38 structures with aqua ligand as the hydrogen atom
donor and in 10 structures with ammine ligand as the hydrogen atom donor. Among all these complexes only one is negatively
charged, 14 are positively charged and 33 are neutral indicating that the overall charge of the molecule has an influence
on the XH/π (X = O or N) interactions. Energy estimated by DFT calculations is approximately 19 kJ mol−1 for the MLOH/π interactions and approximately 15 kJ mol−1 for the MLNH/π interactions.
Dedicated to Professor Milan Melník on the occasion of his 70th birthday 相似文献
4.
The vibronic absorption spectrum of fluoral vapor was studied in the region of the S1←S0 electronic transition (313–360 nm). The origin O0
0+) of the transition (29419 cm−1) and a number of fundamental frequencies in the S0 and S1 states were determined. The character of intensity distribution in the spectral bands indicates that the electronic excitation
leads to significant change of the CF3 group orientation relative to the molecular frame. Moreover, it was found that the carbonyl fragment of the molecule in the
S1 state has pyramidal structure (in contrast, the carbonyl fragment of the fluoral molecule in the S0 state is planar). The experimental torsion and inversion energy levels were used for the calculation of internal rotation
and inversion potential functions of fluoral molecule in the S1 state. The potential barriers to internal rotation and inversion were found to be 1270 cm−1 (15.2 kJ mol−1) and 550 cm−1 (6.6 kJ mol−1), respectively. The conformational changes caused by S1←S0 electronic excitation in the fluoral molecule are similar to those observed in acetaldehyde and biacetyl molecules and differ
from the conformational behavior of hexafluorobiacetyl molecule.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 294–299, February, 1998. 相似文献
5.
Ishtiaque Ahamad Rajendra Prasad Mumtaz Ahmad Quraishi 《Journal of Solid State Electrochemistry》2010,14(11):2095-2105
The present study examines the effect of fexofenadine, an antihistamine drug, on corrosion inhibition of mild steel in molar
hydrochloric acid solution using different techniques under the influence of various experimental conditions. Results revealed
that fexofenadine is an effective inhibitor and percent inhibition efficiency increased with its concentration; reaching a
maximum value of 97% at a concentration of 3.0 × 10−4 M. Fourier-transform infrared spectroscopy (FTIR) observations of steel surface confirmed the protective role of the studied
drug. Polarization studies showed that fexofenadine is a mixed-type inhibitor. The adsorption of the inhibitor on mild steel
surface obeyed the Langmuir adsorption isotherm with free energy of adsorption (∆G°ads) of −40 kJ mol−1. Energy gaps for the interactions between mild steel surface and fexofenadine molecule were found to be close to each other
showing that fexofenadine has the capacity to behave as both electron donor and electron acceptor. The results obtained from
the different corrosion evaluation techniques are in good agreement. 相似文献
6.
The molecular and electronic structure of Mo12S24 macromolecule as the MoS2 single slab structure was calculated by the density functional theory (DFT) method with the B3P86 hybrid exchange-correlation
functional. The results of calculations point to slight relaxation of coordinatively unsaturated Mo and S atoms, which is
consistent with the published data. The calculated width of the forbidden band (0.85–0.98 eV) is comparable with the experimental
value (1.30 eV) and similar to that obtained from DFT calculations with periodic boundary conditions (0.89 eV). The surface
Mo centers in the Mo12S24 macromolecule are more reduced than the internal (MoIV) atoms. In order to characterize the adsorption capacity of coordinatively unsaturated Mo centers, a Mo12S24·6H2S adsorption complex was calculated. The structure and energy characteristics of the adsorption complex point to a weak donor-acceptor
interaction of the π-lone pair of H2S molecule with the surface (reduced) Mo centers. The active center of thiophene hydrodesulfuration catalysts is formed as
a result of the oxidative addition of hydrogen followed by occlusion of hydrogen into the MoS2 matrix.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2189–2193, October, 2005. 相似文献
7.
Izabela Witoska Stanisaw Karski Joanna Gouchowska 《Reaction Kinetics and Catalysis Letters》2007,90(1):107-115
Hydrogenation of nitrate (NO3
−) in water was studied with 0.8 ×10−3–3.2 ×10−3 mol/dm3 of reactant in the temperature range of 293–313 K over palladium promoted Ag catalysts. Pd-Ag catalysts with a low ratio
of Ag/Pd were characterized by high efficiency in the reduction of nitrates. The degradation of nitrates followed approximately
first order decay and the estimated apparent activation energy was about 4 kJ/mol. 相似文献
8.
The metathesis of ethene and 2-butene to propene was studied over WO3/SiO2 catalysts with various WO3 loadings (2, 4, 8, 12, 16, and 24 wt%). The 2-butene conversion and propene selectivity increased greatly with WO3 loading increasing from 2 to 8 wt%, reached maximum at 8–12 wt% WO3 loading, and then decreased when the WO3 loading was higher than 12 wt%. From the above results and taking the economics into account, the optimal amount of WO3 loading was ~8 wt%. The catalysts were characterized by physico-chemical and spectroscopic techniques to elucidate the effect
of different tungsten oxide loadings on the metathesis reactivity of ethene and 2-butene. The characterization data indicated
that three types of tungsten species (i.e., surface tetrahedral tungsten species, surface octahedral polytungstate species,
and WO3 crystallites) were present in the catalysts. It was found that WO3 was not the active centers, and surface tetrahedral tungsten species might be more active than octahedral polytungstate species
in metathesis reaction. The reduced form of tungsten species [W+4, W+5, and W+(6−y) (0 < y < 1)] may be the suitable state of W species acting as metathesis active centers. 相似文献
9.
G. A. Vorob'eva E. V. Gal'tseva A. V. Kozintsev A. I. Prokofev A. A. Dubinskii 《Russian Chemical Bulletin》1998,47(11):2155-2159
The kinetics of sequential generation of mono-, bi-, and triradical centers in heterogeneous reactions of toluene solutions
of orthoquinones, catechols, and their mixtures with γ-Al2O3 was studied. The localization of mono- and biradical centers on the solid oxide surface and the transfer of triradical Al3+ (Q−)3 complexes (Q− is the corresponding 3,6-di-tert-butylsemiquinone radical) to a solution (extraction of Al from the solid phase) were proved. The number of the triradical
complexes extracted is considerably higher than that of active surface centers accessible for coordination with radical ligands.
The conditions favoring the formation of the radical complexes on the Al ions were established. Possible mechanisms of these
processes were proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2223–2227, November, 1998. 相似文献
10.
A. K. Arof N. E. A. Shuhaimi N. A. Alias M. Z. Kufian S. R. Majid 《Journal of Solid State Electrochemistry》2010,14(12):2145-2152
In this work, a chitosan/iota (ι)-carrageenan blended film doped with orthophosphoric acid (H3PO4) as ionic dopant and poly(ethylene glycol) (PEG) as plasticizer has been used as a separator and electrolyte in an electrical
double layer capacitor (EDLC). A set of samples were prepared by the solution cast technique to see the effect of the different
weight ratios of the proton donor and plasticizer on the conductivity. The highest conducting sample has composition 37.50 wt.%
chitosan–37.50 wt.% ι-carrageenan–18.75 wt.% H3PO4–6.25 wt.% PEG. The conductivity value is 6.29 × 10−4 S cm−1. The conductivity–temperature relationship is Arrhenian, and the activation energy for the highest conducting sample is 0.09 eV.
The specific discharge capacitance of the EDLC is 35 F g−1 at 0.11 mA cm−2 current drain and was constant for 30 cycles. 相似文献
11.
Zhao J Li G Wang BM Liu W Nan TG Zhai ZX Li ZH Li QX 《Analytical and bioanalytical chemistry》2006,386(6):1735-1740
Glycyrrhizic acid (GL) is a major active compound of licorice. The specific monoclonal antibody (MAb) (designated as 8F8A8H42H7) against GL was produced with the immunogen GL–BSA conjugate. The dissociation constant (K
d) value of the MAb was approximately 9.96×10−10 M. The cross reactivity of the MAb with glycyrrhetic acid was approximately 2.6%. The conventional indirect competitive enzyme-linked
immunosorbent assay (icELISA) and simplified icELISA adapted with a modified procedure were established using the MAb. The
IC50 value and the detect range by the conventional icELISA were 1.1 ng mL−1 and 0.2–5.1 ng mL−1, respectively. The IC50 value and the detect range by the simplified icELISA were 5.3 ng mL−1 and 1.2–23.8 ng mL−1, respectively. The two icELISA formats were used to analyze GL contents in the roots of wild licorice and different parts
of cultivated licorice (Glycyrrhiza uralensis Fisch). The results obtained with the two icELISAs agreed well with those of the HPLC analysis. The correlation coefficient
was more than 0.98 between HPLC and the two icELISAs. The two icELISAs were shown to be appropriate, simple, and effective
for the quality control of raw licorice root materials. 相似文献
12.
R. S. Mitchenko A. A. Shubin T. V. Krasnyakova 《Theoretical and Experimental Chemistry》2006,42(5):314-319
A heterogeneous catalyst for the hydrochlorination of acetylene by gaseous HCl is formed as a result of mechanical treatment
of the solid salt K2PtCl4 in an atmosphere of acetylene, ethylene, or propylene by the formation of π complexes of platinum(II) as active centers in
the surface layer under these conditions. The controlling stage of the catalytic reaction is chloroplatination of the π-coordinated
acetylene by the HCl molecule. The reaction takes place as a concerted process, in which an intermediate β-chlorovinyl derivative
of platinum(II), a complex of platinum with a coordination vacancy[PtCl
3
*
]−, and a new molecule of HCl are formed simultaneously with cleavage of the H—Cl and Pt—Cl bonds in the metal complex adjacent
to the π-acetylene complex. The catalytic cycle closes with rapid dissociation of the organoplatinum intermediate by the action
of HCl, giving the final product and the initial complex [PtCl4]2−.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 306–311, September–October, 2006. 相似文献
13.
The article discusses recent results of kinetic analysis of propylene and ethylene polymerization reactions with several types
of Ti-based catalysts. All these catalysts, after activation with organoaluminum cocatalysts, contain from two to four types
of highly isospecific centers (which produce the bulk of the crystalline fraction of polypropylene) as well as several centers
of reduced isospecificity. The following subjects are discussed: the distribution of active centers with respect to isospecificity,
the effect of hydrogen on polymerization rates of propylene and ethylene, and similarities and differences between active
centers in propylene and ethylene polymerization reactions over the same catalysts. Ti-based catalysts contain two families
of active centers. The centers of the first family are capable of polymerizing and copolymerizing all α-olefins and ethylene.
The centers of the second family efficiently polymerize only ethylene. Differences in the kinetic effects of hydrogen and
α-olefins on polymerization reactions of ethylene and propylene can be rationalized using a single assumption that active
centers with alkyl groups containing methyl groups in the β-position with respect to the Ti atom, Ti-CH(CH3)R, are unusually unreactive in olefin insertion reactions. In the case of ethylene polymerization reactions, such an alkyl
group is the ethyl group (in the Ti-C2H5 moiety) and, in the case of propylene polymerization reactions, it is predominantly the isopropyl group in the Ti-CH(CH3)2 moiety.
Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 11, pp. 1911–1934.
The text was submitted by the authors in English. 相似文献
14.
Propylene polymerization on TiCl4/donor/MgCl2 (donor = ethyl benzoate, dibutyl phthalate, diisobutyl phthalate, diethyl 2,3-diisopropylsuccinate) supported catalysts is considered. The states of the donors in the catalysts have been investigated by diffuse reflectance IR spectroscopy. Data characterizing the distribution of the donors and the active component (TiCl4) on the support surface have been obtained. Molecular weight distribution data for polypropylene are presented. The molecular weight distribution of polypropylene depends on the location of the donor and TiCl4 molecules. 相似文献
15.
Hydrogenation of crotonaldehyde in a gas phase over Pt/α-GeO2 catalysts was investigated. The systems were characterized by BET, XRD, TPR, TEM, ToF-SIMS, and FTIR methods. The optimum
pretreatment parameters were studied. The best catalytic performance shows the catalyst 5 wt % Pt/α-GeO2 (69% selectivity to crotyl alcohol at 200 μmol s−1 g
Pt
−1
activity and 10% conversion of crotonaldehyde). Lower loaded catalysts (2 and 1 wt % Pt) show lower, but also promising activity
and selectivity. This good catalytic performance was related to the physicochemical properties of the catalyst. GeO2 in the presence of Pt undergoes a partial surface reduction at temperatures higher than 100°C probably leading to the creation
of the active Pt-Ge centers responsible for high selectivity to crotyl alcohol. Reduction at a temperature≥200°C deactivates
the catalytic systems due to the formation of inactive PtGe alloys.
Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 4, pp. 600–605.
This article was submitted by the authors in English. 相似文献
16.
Interactions of (Br−)
i
(H2O)50−i
clusters (0 ≤ i ≤ 6) with molecular oxygen is studied by the molecular dynamics method using flexible molecule model. Values of real and
imaginary parts of permittivity decrease in the 0 ≤ ω ≤ 3500 cm−1 frequency range with increasing number of bromine ions in a cluster. The ability of cluster to absorb IR radiation decreases,
whereas the reflectance and Raman light scattering remains nearly unchanged. An increase in the content of Br− ions in the cluster lowers the power of emitted IR radiation and decreases the amount of active electrons participating in
the interaction with IR radiation. However, when the concentration of Brions becomes substantially higher (at i = 5 and 6), the values of emitted power and the number of active electrons are restored to the values that are typical for
water cluster in the absence of Br− ions. At i ≥ 3, repelling Br− ions acquire kinetic energy, which is sufficient to remove molecular oxygen from the system. 相似文献
17.
This review article summarizes our recent researches for molecular design of polyoxometalates (POMs) and their related compounds
for environmentally-friendly functional group transformations. The divacant POM [γ-SiW10O34(H2O)2]4− exhibits high catalytic performance for mono-oxygenation-type reactions including epoxidation of olefins and allylic alcohols,
sulfoxidation, and hydroxylation of organosilanes with H2O2. We have successfully synthesized several POM-based molecular catalysts (metal-substituted POMs) with controlled active sites
by the introduction of metal species into the divacant POM as a “structural motif”. These molecular catalysts can efficiently
activate H2O2 (vanadium-substituted POM for epoxidation) and alkynes (copper-substituted POM for click reaction and oxidative homocoupling
of alkynes). The aluminum-substituted POM exhibits Lewis acidic catalysis for diastereoselective cyclization of (+)-citronellal
to (−)-isopulegol. In addition, we have developed POM-based “molecular heterogeneous catalysts” by the “solidification” and
“immobilization” of catalytically active POMs. 相似文献
18.
Detlef W. Bahnemann 《Research on Chemical Intermediates》2000,26(2):207-220
The photocatalytic activity of different commercially available titanium dioxide materials is compared employing dichloroacetate
(DCA−) as the model pollutant. A mechanism is presented evincing that one photon is sufficient to initiate the complete mineralization
of one DCA− molecule. The observed non-linear dependence of the photonic efficiency ζ of the DCA− degradation upon the incident photon rate is explained by a simple mathematical model considering only one-electron charge
transfer and recombination reactions on the semiconductor particle. Since photonic efficiencies below 1% are observed when
aromatic compounds are used as model pollutants, an electron-shuttle mechanism is proposed involving the benzoquinone/hydroquinone
redox couple and resulting in an overall enhancement of the electon/hole recombination. Newly synthesized colloidal Ti/Fe
mixed oxide particles exhibit higher activity for the degradation of dichloroacetate than pure TiO2 colloids, however, they still suffer from cathodic corrosion problems. Finally, a self-contained thin film fixed bed reactor
(TFFBR) is presented which can be operated as a stand-alone system gaining the energy for the pump operation from an appropriate
photovoltaic module and regulating the water flow as a function of the solar flux. 相似文献
19.
Maria Kamariotaki Alexandra Karaliota Despina Stabaki Thomas Bakas Spyros P. Perlepes Nick Hadjiliadis 《Transition Metal Chemistry》1994,19(2):241-247
Summary The synthesis and study of a number of new iron(III) complexes of the ligands 3-hydroxy-2(1H)-pyridinone (3,2-opoH), 2,3-dihydroxybenzoic
acid (2,3-dhbH3) and 3,4-dihydroxybenzoic acid (3,4-dhbH3) are described. These complexes have the formulae [Fe(3,2-opo)2Cl]·PrnOH, K[Fe(2,3-dhbH)2(H2O)2], [Fe(2,3-dhb)(H2O)2], K[Fe-(3,4-dhbH)2(H2O)2], [Fe(3,4-dhb)(H2O)2] and K6[Fe(3,4-dhb)3]·3H2O. The complexes were characterized by elemental analyses. X-ray powder patterns, t.g.a./d.t.g. techniques, magnetic susceptibilities
and spectroscopic (u.v.-vis., i.r. and variable-temperature 57Fe-M?ssbauer) studies. Monomeric octahedral structures are assigned for the 1∶2 2,3-dhbH2− complex and the 1:3 3,4-dhb3− compound. Dinuclear and/or oligonuclear structures are tentatively proposed for the remaining complexes in the solid state.
In [FeL(H2O)2] (L3− = 2,3-dhb3− or 3,4-dhb3−), iron(III) appears to be 5-coordinate. Both oxygens of 3,2-opo− participate in coordination, while the dihydroxybenzoato ligands exhibit various coordination modes, depending mainly on
the positions of the hydroxy groups, their anionic charge and the ligand∶metal molar ratio used. 相似文献
20.
Thato N. Mtshali Walter Purcell Hendrik G. Visser Steven S. Basson 《Transition Metal Chemistry》2008,33(4):481-491
The kinetics of the reaction between [ReN(H2O)-(CN)4]2− with different κ2
N,O-donor ligands (quin− and 2,3-dipic−, respectively) have been studied in the pH 4–12 range in aqueous solution. Two consecutive reaction steps with the formation
of the [ReN(η1-quin)(CN)4]3− and [ReN(μ2-quin) (CN)3]2− complexes, respectively, were spectrophotometrically observed and kinetically investigated. The same reaction mechanism is
proposed for these two ligands. The first fast reaction (for quin−) is attributed to the aqua substitution of [ReN(H2O)(CN)4]2− with forward and reverse rate constants of 1.96(5) × 10−1 M−1 s−1 and 5.6(3) × 10−2 s−1, while a rate of 2.64(3) M−1 s−1 was observed for the reaction between the conjugate base [ReN(OH)(CN)4]3− and quin− at 40.2 °C. Due to small absorbance changes, it was difficult to obtain any good quality data for the fast reactions for
2,3-dipic−. The second, slower reaction is attributed to cyano substitution with rate constants (k
3
K
1) of 4.17(4) × 10−3 for quin− and 4.68(7) × 10−3 M−1 s−1 for 2,3-dipic−, at 80.02 °C, respectively. The acid dissociation constant for the aqua complex was spectrophotometrically determined as
11.58(3) and 11.54(2) and kinetically as 11.51(8) and 11.41(1), at 80.4 °C, respectively. Negative values of −83.5(2) and −144.1(2) J K−1 mol−1 as well as the of 71.4(3) and 47.3(3) kJ mol−1, for the slow quin− and 2,3-dipic− reactions, respectively, point to an ordered transition state where bond formation is responsible for the major driving force
of the reaction. The and for the fast forward reaction of quin− is indicative of expected associative activation in the transition state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献