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131.
The function Δ(ΔG A 0), which is the difference of Gibbs energies characterizing surface-active substance (surfactant, SAS) adsorption at metal/solution and air/solution surfaces, has been introduced. The equation connecting the function Δ(ΔG A 0) with SAS ionization potential has been obtained using the elementary theory of donor-acceptor interactions. Published experimental data on SAS adsorption at mercury, bismuth and gold have been used for Δ(ΔG A 0) calculation. The dependence of Δ(ΔG A 0) on ionization potentials can be described by an equation derived in this work. It has been demonstrated that the value of the hydrophilicity of gold is much higher than the values for mercury and bismuth. The lifetime of SAS molecules at a metal surface has been estimated. The question of the possibility of theoretica l estimation of standard energies ΔG A 0 characterizing SAS adsorption at a metal/solution surface has been discussed. Received: 9 December 1996 / Accepted: 13 January 1997  相似文献   
132.
Geometry optimization of small (H2O)n+ clusters (n ≤ 4) at the UHF/4–31 + + G** level indicates that the cations consist of two fragments: the OH radical and the H2n−1 O+n−1 ion. The latter can be considered as a thermodynamically stable combination of a distorted H3O+ ion and (n−2) H2O molecules. The H bond between the fragments becomes weaker with increasing cluster size. Extrapolation of the adiabatic ionization potentials calculated for the (H2O)n oligomers (n ≤ 4) at the MP2 level to an infinite cluster size provides the value of approximately 8.7 eV, which can be presumably necessary for the ionization of liquid water in a vacuum. © 1997 John Wiley & Sons, Inc.  相似文献   
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135.
A number of macromolecular and supramolecular catalysts which combine the functions of transition metal complex, phase transfer agent with molecular recognition ability has been designed. The complexes of rhodium, palladium, iron and copper showed the remarkable activity in hydroformylation, Wacker‐type oxidation of various olefins, oxidation of alkanes and hydroxylation of aromatics.  相似文献   
136.
Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical‐warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence‐based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven π‐conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1 – 7 , were adsorbed onto a solid support and exposed to vapors of alkylators 8 – 15 . The alkylation‐induced color‐shift patterns of the seven‐spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb.  相似文献   
137.
A synthetic approach leading to the meso-arylporphyrins containing a conformationally mobile polyether fragment on the benzene ring with a terminal pyridine ring has been developed, which opens the possibility for design of new porphyrin-based molecular receptors for detection and selective binding of alkali metal cations.  相似文献   
138.
Nanostructured doped ceria is a prospective material for catalytic applications such as the construction of membranes with mixed electronic and ionic conductivity for effective syngas production. In this article, the surface properties of nanostructured ceria doped with praseodymium have been studied by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy of adsorbed carbon monoxide. The effects of supporting 1.4 wt % Pt as well as structural changes upon the reduction of the samples with methane have been investigated. While in samples without supported platinum, mainly praseodymium cations are reduced in a methane atmosphere; stronger reduction of cerium cations was found in the case of surface modification with Pt. The structural differences correlate with results from temperature-programmed reaction experiments with methane. Explanations are discussed in terms of different reaction mechanisms.  相似文献   
139.
The possibility to extend the classical Ito's construction of stochastic integrals is studied. This construction can be applied to fractional Brownian motions with Hurst index H(0, 1/2). A change of variables formula for fractional Brownian motions in terms of the stochastic integrals is given.  相似文献   
140.
Interface water anions composed of several chainlike or cyclic fragments were simulated with a 6‐31++G** basis set at the unrestricted Hartree–Fock level with the second‐order Moeller–Plesset perturbation theory corrections taken into account. The estimated vertical electron detachment energies (VDEs) of (H2O) anions were approximated by a VDE‐n?1/3 dependence close to the experimental one. A hypothesis about the predominant formation of interface structures under conditions of molecular flows is put forward. The atomic population analysis, character of the highest occupied molecular orbital, and changes in the geometry of interface anions with an increase in their molecular size reveal the compact localization of the excess electron density in water clusters and allow evaluating the effective excess‐electron radius of condensed water as 2.5 Å, in good agreement with a similar empirical estimate. The scope of the data obtained shows the relatively low probability of the formation of octahedral hydration shells compared to the tetrahedral coordination of solvating water molecules. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002  相似文献   
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