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排序方式: 共有1880条查询结果,搜索用时 312 毫秒
991.
Takanori Hirano Takeo Oku Masayuki Kawaguchi Katsuaki Suganuma 《Molecular Crystals and Liquid Crystals》2013,570(1):787-792
Abstract Boron nitride nanocapsules with gold, iron oxide and germanium nanoparticles were produced. High-resolution electron microscopy and electron energy-loss spectroscopy showed the gold, iron oxide and germanium nanoparticles were encapsulated in the boron nitide sheets. Weak peaks of photoluminescence spectrum were observed from the nanocapsules with germanium nanoparticles. The present work indicates that the boron nitide nanocapsules with conducting, magnetic and semiconductor nanoparticles can be produced by are melting method, and models for the formation mechanism and nano-structures of the boron nitide nanocapsule were proposed. 相似文献
992.
993.
Andrew G. Dalling Takayuki Yamauchi Niall G. McCreanor Lydia Cox John F. Bower 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):227-231
Rh‐catalyzed carbonylative C?C bond activation of cyclopropylamides generates configurationally stable rhodacyclopentanones that engage tethered alkenes in (3+1+2) cycloadditions. These studies provide the first examples of multicomponent cycloadditions that proceed through C?C bond activation of “simple” electron poor cyclopropanes. 相似文献
994.
Takayuki Yamada Dr. Yu Shibata Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16022-16031
It has been established that a cyclopentadienyl (Cp) RhIII complex with two aryl groups and a pendant amide moiety catalyzes the formal Lossen rearrangement/alkenylation cascade of N-pivaloyl heterole carboxamides with internal alkynes, leading to alkenylheteroles. Interestingly, the use of sterically demanding internal alkynes afforded not the alkenylation but the [3+2] annulation products ([5,5]-fused heteroles). In these reactions, the pendant amide moiety of the CpRhIII complex may accelerate the formal Lossen rearrangement. The use of five-membered heteroles may deter reductive elimination to form strained [5,5]-fused heteroles; instead, protonation proceeds to give the alkenylation products. Bulky alkyne substituents accelerate the reductive elimination to allow the formation of the [5,5]-fused heteroles. 相似文献
995.
996.
The morphology and dispersion state of Ba2TiSi2O8 (BTS) nanocrystals in transparent glass-ceramics (composition: 40BaO–20TiO2–40SiO2) were examined from high resolution transmission electron microscope observations, and their nano-scale deformation behavior was examined using Berkovich nanoindentation technique (standard-type and continuous stiffness measurement (CSM)-type). In the early stage of crystallization, BTS crystalline layers with a thickness of ~ 120 nm were formed at the surface and ellipsoid-shaped crystallites with a diameter of 100–200 nm were dispersed in the glass matrix. In the late stage, BTS crystals with a diameter of 200–400 nm were formed densely, but a glassy phase was present between BTS crystals. The Young's modulus evaluated from CSM-type nanoindentation measurements for a deformation scale of about 100 nm shows the values of 98 GPa for the glass and 110 GPa for the glass-ceramics with nanocrystals. It was suggested that CSM-type measurements are very sensitive in the nano-scaled homogeneity in the heat-treated samples. 相似文献
997.
Dr. Haruhisa Kikuchi Kosuke Kawai Yota Nakashiro Takayuki Yonezawa Kumi Kawaji Prof. Dr. Eiichi. N. Kodama Prof. Dr. Yoshiteru Oshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(4):1106-1112
The structural diversity of natural products and their derivatives have long contributed to the development of new drugs. However, the difficulty in obtaining compounds bearing skeletally novel structures has recently led to a decline of pharmaceutical research into natural products. This paper reports the construction of a meroterpenoid-like library containing 25 compounds with diverse molecular scaffolds obtained from diversity-enhanced extracts. This method constitutes an approach for increasing the chemical diversity of natural-product-like compounds by combining natural product chemistry and diversity-oriented synthesis. Extensive pharmacological screening of the library revealed promising compounds for anti-osteoporotic and anti-lymphoma/leukemia drugs. This result indicates that the use of diversity-enhanced extracts is an effective methodology for producing chemical libraries for the purpose of drug discovery. 相似文献
998.
Dr. Chihiro Maeda Shuichi Nomoto Koki Akiyama Dr. Takayuki Tanaka Prof. Tadashi Ema 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(63):15699-15705
Carbazole-based aza[7]helicenes and hetero[9]helicenes were successfully obtained via the intramolecular Scholl reaction of 3,6-bis(biphenyl-2-yl)carbazole congeners, while the reaction of 3,6-bis(naphthylphenyl)-appended carbazole gave a triple helicene via an unexpected simultaneous double aryl rearrangement. DFT calculations suggested that the rearrangement proceeded via an arenium cation intermediate. In addition, the reaction of methoxy-appended substrate gave an azahepta[8]circulene via the concurrent C−C bond formation. These helical dyes showed circularly polarized luminescence. The azahepta[8]circulene was further transformed into deeply saddle-distorted dibenzodiaza[8]circulenes as the first example of its solution-based synthesis and unambiguous structural determination. 相似文献
999.
1000.
Atsushi OkazawaKei Fujiwara Ryo WatanabeNorimichi Kojima Shunsuke YoshiiHiroyuki Nojiri Takayuki Ishida 《Polyhedron》2011,30(18):3121-3126
Heterometallic polymeric coordination compounds [{Ln(hfac)2(CH3OH)}2{Cu(dmg)(Hdmg)}2]n (abbreviated as [Ln2Cu2]n) involving light lanthanoid ions, Pr, Nd, Sm, and Eu, were synthesized, where H2dmg and Hhfac stand for dimethylglyoxime and 1,1,1,5,5,5-hexafluoropentane-2,4-dione, respectively. The X-ray crystallographic analysis shows that their structures are isomorphous to those of the known heavy lanthanoid analogs. The exchange couplings were evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving ferromagnetic exchange parameters: JPr-Cu/kB = 0.039(1) K, JNd-Cu/kB = 0.38(1) K, JSm-Cu/kB = 0.95(2) K, and no interaction between Eu and Cu ions. A significant trend is found in the order of the periodic table. The ferro- and antiferromagnetic 4f-3d couplings were characterized for the light and heavy lanthanoid derivatives, respectively. The magnitude of JLn-Cu decreases with a decrease of the 4f-spin portion, i.e., the number of unpaired electrons, whether the coupling is ferro- or antiferromagnetic. 相似文献