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81.
The dynamic processes of N(1s) core-hole excitation in gas-phase CH3CN molecule have been studied at both Hartree-Fock and hybrid density-functional theory levels. The vibrational structure is analyzed for fully optimized core-excited states. Frank-Condon factors are obtained using the linear coupling model for various potential surfaces. It is found that the vibrational profile of the N-K absorption can be largely described by a summation of two vibrational progressions: a structure-rich profile of nu(CN) stretching mode and a large envelope of congestioned vibrational levels related to the strong (-C-CN) terminal bending bond. Excellent agreement between theoretical and experimental spectra is obtained. 相似文献
82.
Elhabiri M Siri O Sornosa-Tent A Albrecht-Gary AM Braunstein P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(1):134-141
We present a detailed study on the acid-base behaviour of a family of "potentially antiaromatic" p-benzoquinonediimine ligands. These 12pi electron molecules can be considered as constituted of two chemically connected but electronically not conjugated 6pi-electron subunits. Upon successive protonation, "mono" and "double" cyanine-type chromophores are generated in solution and allow a precise and sensitive spectrophotometric detection. These molecules represent a new class of tunable quinones whose electronic and structural properties can be triggered by proton input, as established by a complete physico-chemical study involving a combination of potentiometric and spectrophotometric methods (absorption and emission). 相似文献
83.
Bismuth triflate catalyzes the allylation of a variety of in situ generated protected aldimines using aldehydes, primary carbamates, and allyltrimethylsilane in a three-component reaction. The reaction proceeds rapidly and affords the corresponding protected homoallylic amine in good yield (up to 86%). Scope and limitations of the aldehyde and carbamate components are reported. 相似文献
84.
Fiaty K Charcosset C Perrin B Couturier R Maïsterrena B 《Journal of computational chemistry》2005,26(3):201-213
Simulations of coupled interactions involving two opposite enzymatic reactions, solute diffusions, and electrostatic interactions between membrane charges and charged solutes were conducted under a fixed kinase-channel-phosphatase (KCP) topology oriented from the outside to the inside of a porous membrane structure. Depending on the kinase and phosphatase locations, we recently demonstrated that an active transport of a phosphorylated substrate may occur via the opposite topology, that is, a PCK topology. The present analysis demonstrates that, under a KCP membrane topology, which also behaves as a specific ATP-dependent transporter, the active transport of a neutral substrate may occur. This analogous active transport appears to be dependent on the phosphatase location and on the membrane surface potentials. A broad analysis of the role played by the main parameters taken into account in the model was conducted in order to define precisely the physico-chemical conditions and the membrane topology needed for the highest active transports within the shortest time. 相似文献
85.
A single crystal of a new sodium calcium iron (III) phosphate, Na4CaFe4(PO4)6, has been synthesized by a flux method and characterized by X-ray diffraction, Mössbauer spectroscopy and magnetic susceptibility measurements. The compound crystallizes in the monoclinic space group C2/c(a=12.099(5) Å, b=12.480(5) Å, c=6.404(2) Å, β=113.77(3)°, Z=2, R1=0.022, Rw2=0.066). The crystal structure belongs to the alluaudite type, characterized by the X(2)X(1)M(1)M(2)2(PO4)3 general formula. The open framework results from Fe2O10 units of edge-sharing FeO6 octahedra, which alternate with M(1)O6 octahedra (M(1)=Na+Ca) that form infinite chains. These chains are linked together through the common corners of PO4 tetrahedra yielding two distinct tunnels of sodium cation occupation. This compound is antiferromagnetic with a Néel temperature of 35 K. Mössbauer parameters are consistent with the structural results. 相似文献
86.
M. A. Kenawy M. S. Sakr E. M. Sakr H. A. Zayed N. O. Mourad 《Czechoslovak Journal of Physics》1991,41(10):967-974
Transient and steady state creep of Al-4.5 wt. % Mg alloy was studied under various constant stresses ranging from 91 MPa to 117 MPa in the temperature range from 473 K to 553 K. The results of creep characteristics have shown two main deformation temperature regions (below 493 K and above 513 K as well as a transient region between these temperatures). Peak values of transient creep parametersB andn were obtained at 493 K. The transient creep parameterB was related to the steady state creep rate st through the exponent which was found to range from 0.85 to 0.5. The stress exponentm of the steady state creep has been found to be minimum at the steady state strain peaks, which is characteristic of dislocation climb along the grain boundaries. Microstructural analysis confirmed that the above mentioned mechanism took place in the dissolution region of-phase. 相似文献
87.
88.
89.
Castillo JF Aoiz FJ Bañares L Martinez-Nuñez E Fernandez-Ramos A Vazquez S 《The journal of physical chemistry. A》2005,109(38):8459-8470
An ab initio interpolated potential energy surface (PES) for the F + CH4 reactive system has been constructed using the interpolation method of Collins and co-workers. The ab initio calculations have been performed using second-order M?ller-Plesset (MP2) perturbation theory to build the initial PES. Scaling all correlation (SAC) methodology has been employed to improve the ab initio calculations and to construct a dual-level PES. Using this PES, a detailed quasiclassical trajectory study of integral and differential cross sections, product rovibrational populations and internal energy distributions has been carried out for the F + CH4 and F + CD4 reactions and the theoretical results have been compared with the available experimental data. 相似文献
90.
Haneline MR Taylor RE Gabbaï FP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(21):5189-5193
Trimeric perfluoro-ortho-phenylenemercury (1) constitutes one of the simplest trifunctional Lewis acidic hosts. In addition to cooperative effects arising from the proximity of the mercury(II) centers, the electron-withdrawing properties of the backbone and the accessibility of the electrophilic sites lead to the facile complexation of neutral and electron rich substrates. The planarity of the structure as well as its overall polarizability compounded with relativistic effects at mercury also permits the occurrence of non-covalent interactions and accounts for the tendency of this compound to form cofacial dimers. Collectively, the Lewis acidic properties of 1 as well as its ability to engage in non-covalent interactions can be held responsible for its ability to form extended binary supramolecular stacks with arenes. The photoluminescence observed in some of these supramolecular complexes corresponds to the phosphorescence of the aromatic substrate and indicate the occurrence of a mercury heavy atom effect. 相似文献