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61.
Dr. Yoshihiro Sohtome Bongki Shin Natsuko Horitsugi Prof. Dr. Keiichi Noguchi Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2011,6(9):2463-2470
Herein, we present details of our conformationally flexible, 1,3‐diamine‐tethered guanidine/bisthiourea organocatalysts for chemo‐, regio‐, and enantioselective 1,4‐type Friedel–Crafts reactions of phenols. These organocatalysts show a unique stereo‐discrimination governed by the differential activation entropy (ΔΔS≠), rather than by the differential activation enthalpy (ΔΔH≠). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS≠). A plausible guanidine–thiourea cooperative mechanism for the enantioselective Friedel–Crafts reaction is proposed. 相似文献
62.
Bungo Ochiai Jun‐ichi Nakayama Masayuki Mashiko Yoshiro Kaneko Tomomi Nagasawa Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5899-5905
This article describes the polyaddition of bifunctional five‐membered cyclic carbonates and diethylenetriamine. The polyaddition proceeded via the selective addition of the primary amino group to the cyclic carbonates to give poly(hydroxyurethane)s bearing a secondary amine structure in the main chain. The resulting poly (hydroxyurethane) having a secondary amine structure was crosslinked by a reaction with a bifunctional dithiocarbonate to give a networked poly(hydroxyurethane–mercaptothiourethane). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5899–5905, 2005 相似文献
63.
Hiroyuki Sasaki Akinori Tanaka Tazumi Nagasawa Shoji Suzuki Toshiro Nagase 《Solid State Communications》2004,129(2):91-95
We have carried out an angle-resolved photoemission study for CoSi2 nanofilms grown on the Si(111)-7×7 substrates. The surface of CoSi2(111) nanofilm changes from the bulk-truncated surface to the surface with additional Si-bilayer by annealing at higher temperature above 825 K. The angle-resolved photoemission spectra of the CoSi2 nanofilm annealed at 853 K show the spectral features originated from the surface resonance state on the CoSi2 surface terminated by Si-bilayer. From the detailed photoemission study, we discuss the surface electronic structure in CoSi2(111) nanofilms grown on Si(111) substrates. 相似文献
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The modulation of the real part of the non-linear refractive index (Δn) associated with the giant two-photon absorption (GTA) band of the excitonic molecules (EM's) has been measured in CuCl at 1.6K. This has been measured by the observation of the polarization rotation effects due to the induced optical anistropy between the right circularly polarized (σ+) and the left circularly polarized (σ-) components of the linearly polarized probe team of Ω1 under the strong irradiation of the σ- beam of Ω2 fixed around the GTA band at 3.1861 eV. The maximum amount of Δn has been 2.9×10-4 at 3.1920 eV under the maximum excitation level when Ω2 has been fixed at 3.1796 eV. The experimental results have been discussed in terms of the renormalization of the polaritons due to the real and virtual formation of EM's. 相似文献
66.
A method of measuring flow-birefringence is reported. In this method, a circularly polarized light wave is transmitted through the flow-birefringent medium. The transmitted elliptically polarized wave is compensated by a Babinet-Soleil plate to convert it back into a circularly polarized wave. The state of circular polarization is confirmed using the rotating-analyser method. Measurements can be carried out with a sample having a fixed azimuth. The minimum detectable optical retardation angle was 5 × 10-3 degree. This corresponds to a birefringence of Δn = 1 × 10-10, when the optical path length of the sample cell is 100 mm. 相似文献
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The temperature dependences of the elastic constants, c11, c33, c44, and c66, in KCP are described. In the temperature range 10–100 K softening is observed in c44, while c66 decreases almost linearly with decreasing temperature. These results indicate the presence of a new critical region. 相似文献
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