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201.
The living radical photocopolymerization of 2-(N,N-diethyldithiocarbamyl)ethyl methacrylate (DCEM) as inimer and stearyl methacrylate (STM) as comonomer was carried out under UV irradiation. According to this method, we synthesized hyperbranched polymers (HP) consisting of a STM sequence having a long alkyl side chain. The gel permeation chromatography distribution of hyperbranched polymers had a unimodal pattern. The reactivity ratios (r(1)=0.79 and r(2)=0.81) were estimated by the Kelen-Tüd?s method (DCEM: [M](1) and STM: [M](2)). These values indicated that the two monomers showed almost equal reactivity toward propagating radical species. The radius of gyration (R(g)) and the hydrodynamic radius (R(h)) of copolymers were determined by static and dynamic light scattering (SLS and DLS), and the values of R(g)/R(h) changed from 0.79 to 1.59 with an increment of the feed amount of STM. These results indicated that the copolymer structures changed from hard spheres to loose branched molecules in solution. 相似文献
202.
Takuya Akatsuka Mayuko Ushiro Shin-ichi Nagamatsu Yoshio Takahashi Takashi Fujikawa 《Polyhedron》2008,27(14):3146-3150
We apply multiple-scattering calculations to the analyses of Sn L3-edge X-ray absorption near-edge structure (XANES) spectra for environmental organotin compounds such as SnCl4−nMen, SnCl4−nBtn, and SnCl4−nPhn (n = 0–4) where Me = CH3, Bt = C4H9, and Ph = C6H5. The XANES peak at 3960 eV has rich information on the local structure. Referring to the optimized structures by density functional theory (DFT) calculations, multiple-scattering calculations well explain the observed spectral changes for different “organic extents”. The present study also supports the widely-used semiempirical rule called ‘Natoli’s rule’ for these environmental compounds, which will be useful to use XANES spectra for the practical analytical tools. 相似文献
203.
Fukui H Kishi R Minami T Nagai H Takahashi H Kubo T Kamada K Ohta K Champagne B Botek E Nakano M 《The journal of physical chemistry. A》2008,112(36):8423-8429
Hybrid density functional theory method is applied for investigating the diradical character dependence of the second hyperpolarizability (gamma) of square planar nickel complexes involving several types of bidentate ligands [o-C6H4XY, where X = Y = O, NH, S, Se, and PH as well as (X, Y) = (NH, NH2) and (S, NH2)]. It is found that, as a function of the donor atoms, the diradical character of these complexes varies from 0.0 to 0.884 and is associated with substantial variations of gamma ranging from 14 x 10(3) to 819 x 10(3) au. In particular, the largest gamma values are associated with intermediate diradical characters in good agreement with the structure-property relationship obtained for pure hydrocarbon systems. Increasing the electronegativity of the X and Y donor groups of the ligands leads to larger diradical characters as a result of the enhancement of the double bond nature of the C=X(Y) bonds, which further stabilizes the diradicals on both-end benzene rings. This demonstrates that the electronegativities of the donor atoms of the ligands become a tuning parameter of the diradical character and then of the gamma values of these complexes. 相似文献
204.
We study the problem of classification of triples ( $ \mathfrak{g} $ ; f; k), where g is a simple Lie algebra, f its nilpotent element and k ∈ $ \mathbb{C} $ , for which the simple W-algebra W k ( $ \mathfrak{g} $ ; f) is rational. 相似文献
205.
206.
Sumio Kato Takuya Yoshizawa Nobuhiro Kakuta Shinya Akiyama Masataka Ogasawara Takashi Wakabayashi Yuunosuke Nakahara Shinichi Nakata 《Research on Chemical Intermediates》2008,34(8-9):703-708
Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La9.33Si6O26 and La8.33ASi6O25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La9.33Si6O26 catalyst exhibited high activity for oxidation of C3H6, comparable to Pd/Al2O3 catalyst, although the specific surface area of La9.33Si6O26 was lower than that of Al2O3. In addition, Pt/La9.33Si6O26 catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al2O3 catalyst. Substitution of Ba2+ for La3+ of La9.33Si6O26 led to increased catalytic activity at low temperature. 相似文献
207.
Hori T Peng X Aratani N Takagi A Matsumoto T Kawai T Yoon ZS Yoon MC Yang J Kim D Osuka A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(2):582-595
Starting from 1,3-phenylene linked diporphyrin zinc(II) complex 2ZA, repeated stepwise Ag I-promoted coupling reactions provided linear oligomers from 2nZA up to 128ZA. Of these zigzag shaped porphyrin arrays, the Ag I-promoted intramolecular cyclization reaction of 2 nZA (n=5, 6, 8, 9, 12, and 16) under dilute conditions gave the corresponding cyclic porphyrin wheels C2nZA (n=5, 6, 8, 9, 12, and 16), whereas large arrays 2nZA (n=24, 32, and 48) did not provide cyclic porphyrin products. These large discrete porphyrin arrays and wheels were fully characterized by means of 1H NMR spectroscopy, MALDI-TOF mass spectrometry, UV/Vis absorption spectroscopy, GPC-HPLC analysis, and the scanning tunneling microscopy (STM) technique. The STM images of C12ZA and C18ZA reveal their large circular structures. In the cyclic structures of C2nZA in solution, however, the gradual decrease in fluorescence quantum yields and fluorescence lifetimes are observed, reflecting some conformational heterogeneities. Collectively, the present work provides an important contribution to the construction of fully covalently linked large cyclic arranged porphyrin arrays with ample electronic interactions as a model of light-harvesting antenna. 相似文献
208.
Caskey DC Yamamoto T Addicott C Shoemaker RK Vacek J Hawkridge AM Muddiman DC Kottas GS Michl J Stang PJ 《Journal of the American Chemical Society》2008,130(24):7620-7628
The coordination-driven self-assembly of four different trigonal prisms from 3 equiv of one of four different tetrapyridyl star connectors and 6 equiv of a platinum linker dication in nitromethane is presented. This face-directed approach affords high yields without template assistance. The prisms have been characterized by multinuclear and DOSY NMR and dual ESI-FT-ICR mass spectrometry. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges, and vertices. Molecular mechanics results suggest that in the smallest prism 3d collective effects dominate and the all-P and all-M conformers are strongly favored. NMR data prove that the two edges of the pyridine rings in the triflate salts of 3a-3d are distinct. An Eyring plot of rates obtained from line-shape analysis and 1-D EXCHSY NMR yields an activation enthalpy DeltaH(double dagger) of approximately 12 kcal/mol and activation entropy DeltaS(double dagger) of approximately -15 cal/mol x K for the edge interconversion process, compatible with pyridine rotation around the Pt-N bond. For 3c, this behavior is observed only up to approximately 318 K. At higher temperatures, the Eyring plot is again linear but follows a very different straight line, with a DeltaH(double dagger) of approximately 35 kcal/mol and DeltaS(double dagger) of approximately 60 cal/mol x K. This highly unusual result is further investigated and discussed in the following companion paper. 相似文献
209.
Axially chiral dicarboxylic acid (R)-1d catalyzed reaction of diazoacetamides and N-Boc imines provided a novel organocatalytic means for the formation of enantiomerically enriched N-Boc protected trans aziridines. 相似文献
210.
An intermolecular nickel-catalyzed addition reaction has been developed where N-arylphthalimides react with alkynes to afford substituted isoquinolones. A mechanistic rationale is proposed, implying nucleophilic attack of Ni(0) to an amide as the primary step of the catalytic cycle. 相似文献