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11.
Tada M Taniike T Kantam LM Iwasawa Y 《Chemical communications (Cambridge, England)》2004,(22):2542-2543
The self-dimerized chiral assembly of vanadium-Schiff-base complexes was found to occur on a SiO2 surface and to be the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol with 100% selectivity and 90% enantioselectivity. 相似文献
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Proton T1 measurement with the Fourier transform method combined with quenching of dipolar coupling through selective deuterium substitution is shown to be a useful method for elucidating intra- and intermolecular interactions in solution, with 2′,3′-isopropylideneadenosine as an example. Average distances between H-8 and ribose protons are determine in combination with carbon-13 T1 measurement. The method is compared with the nuclear Overhauser effect. 相似文献
14.
Rotational correlation times (τT) of the 5′-AMP molecule deduced from spin-lattice relaxation times (T1) of different protons in the molecule agree fairly well with each other in the temperature range of 3.5–74°C. The same is true with τT values deduced from 13CT1 values. These results indicate that the internal motions are slow as compared to the overall rotation of the 5′-AMP molecule. 相似文献
15.
Okuno Y Yokoyama T Yokoyama S Kamikado T Mashiko S 《Journal of the American Chemical Society》2002,124(24):7218-7225
We made theoretical calculations for a benzonitrile molecule and its clusters in the gas phase and as adsorbed on the Au(111) surface, to explain the observation by scanning tunneling microscope, that is, the trimer formation of cyanophenyl porphyrins adsorbed onto the Au(111) surface. With regard to the gas-phase species, ab initio calculations showed that (1) the benzonitrile dimer has a single stable structure that is planar and antiparallel; (2) the trimer has two isoenergetic stable structures, that is, a planar and cyclic structure and an antiparallel and nonplanar one; (3) the clusters are more stable, at low temperatures, than the monomer. For the adsorbed species, we made quantum mechanical/molecular mechanical calculations in which the interaction between the adsorbates and the surface is evaluated in a molecular-mechanical way by using analytical potential functions and an image charge model. Because the stable structures were found to be similar to those in the gas phase, the cluster formation of adsorbed cyanophenyl porphyrins was attributed to the interaction between cyanophenyl groups, which is barely affected by adsorbate-surface interaction. It was also found that the adsorbed cyclic benzonitrile trimer is more stable than the monomer and the dimer because the relative stability is dependent on enthalpy alone. We therefore concluded that the preferential formation of trimers by the adsorbed cyanophenyl porphyrins is due to the negligible contribution of entropy to the relative stability of the adsorbed species and that the adsorption hardly changes the situation found in the gas phase. 相似文献
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Kazunori Yokoyama 《Mathematical Programming》1992,56(1-3):233-243
In this paper, we present-optimality criteria for convex programming problems associated with exact penalty functions. Several authors have given various criteria under the assumption that such convex problems and the associated dual problems can be solved. We assume the solvability of neither the convex problem nor the dual problem. To derive our criteria, we estimate the size of the penalty parameter in terms of an-solution for the dual problem. 相似文献
18.
Ammonium aromatic diselenoates were synthesized by reacting aromatic diselenoic acid 2-(trimethylsilyl)ethyl esters derived from aluminum 2-(trimethylsilyl)ethyl selenolate with aromatic selenoic acid O-methyl esters with ammonium fluorides. The results of molecular structure analysis and NMR studies of ammonium salts supported the double-bond character between the carbon atom and selenium atoms. 相似文献
19.
Infrared studies of Se-based polynary chalcogenide glasses (II): YxZxSe100−2x (Y = Ge,As; Z = As,Te)
Toshiaki Ohsaka 《Journal of Non》1976,22(1):89-96
The infrared (IR) absorption spectra for YxZxSe100?2x glasses (Y = Ge, As;Z = As, Te), x = 2.5 and 5.0 are measured in the wavenumber region 700-60 cm?1 at room temperature. These IR spectra are explained by comparing with the IR spectra already reported for the binary glasses such as Ge–Se, As–Se and Se–Te. In GexAsxSe100-2x glasses (x ? 5.0), the main spectral features as well explained by both the spectra of GexSe100?x and AsxSe100?x glasses. Main structural units in these glasses are considered to be GeSe4 tetrahedra and AsSe3 pyramids, and Se8 rings and Sen chains which are the units in pure glassy Se. In GexTexSe100?2x glasses (x ? 5.0) and IR band which cannot be explained by either the spectra of GexSe100?x or Se100?xTex glasses appears at 210 cm?1. This band is considered to be due to Ge–Te bonds. The IR spectra of AsxTex Se100?2x glasses (x ? 5.0) are well explained by both the spectra of AsxSe100?x and Se100?xTex glasses. It is concluded that As and Te atoms combine with Se atoms in the forms of AsE3 pyramids and Se5Te3 mixed rings, respectively. 相似文献
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