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排序方式: 共有1273条查询结果,搜索用时 78 毫秒
1.
Sho Ikeda Ryo Shintani 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5790-5794
A new mode of polymerization, rhodium‐catalyzed stitching polymerization, has been developed for the synthesis of π‐conjugated polymers with bridged repeating units from nonconjugated 1,5‐hexadiynes containing both terminal and internal alkyne moieties as monomers. The polymerization proceeded smoothly with a high degree of stitching efficiency under mild conditions, and 1,5,9‐decatriyne and 1,5,9,13‐tetradecatetrayne monomers could also be employed. The present polymerization strategy would be particularly beneficial for the synthesis of polymers consisting of a repeating unit that is difficult to prepare as a stable monomer because it does not require the use of a preformed bridged π‐conjugated monomer. 相似文献
2.
3.
Jin Tanaka Yu Shibata Anton Joseph Juntaro Nogami Jyunichi Terasawa Ryo Yoshimura Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5774-5779
It has been established that a newly developed cyclopentadienyl rhodium(III) [CpARhIII] complex, bearing an acidic secondary amide moiety on the Cp ring, is able to catalyze the ortho-bromination of O-phenyl carbamates with N-bromosuccinimide (NBS) at room temperature. The presence of the acidic secondary amide moiety on the CpA ligand accelerates the bromination by the hydrogen bond between the acidic NH group of the CpA ligand and the carbonyl group of NBS. 相似文献
4.
Genki Namba Yuki Mimura Prof. Yoshitane Imai Dr. Ryo Inoue Prof. Yasuhiro Morisaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14871-14877
Optically active X-shaped molecules based on the planar chiral [2.2]paracyclophane building block were prepared, in which di(methoxy)terphenyl units were stacked on the central benzene rings. At 25 °C, anisolyl rings freely rotate in solution, while in the crystal form, they are fixed by intramolecular CH–π interactions, thereby leading to the expression of the axial chirality, i.e., propeller chirality was exhibited by the planar chiral [2.2]paracyclophane moiety. The X-shaped molecule exhibited good circularly polarized luminescence (CPL) profiles with moderate ΦPL and a large glum value in the order of 10−3 at 25 °C, in solution. In contrast, at −120 °C, dual CPL emission with opposite signs was observed. According to the theoretical studies, the rotary motion of the anisolyl units is suppressed in the excited states, and so emission from two isomers could be observed. These results demonstrate that the axial chirality was controlled by the planar chirality, leading ultimately to propeller chirality. 相似文献
5.
To prepare cross‐linked silicone (silicone rubber) particles in an aqueous medium, we investigated two synthesis methods involving a miniemulsion system. The first method was based on cationic ring‐opening polymerization of cyclic siloxane, which is a common synthetic route for linear silicone oil and uses octamethylcyclotetrasiloxane (D4) as the monomer and dimeric D4 (bis‐D4) as the cross‐linker. Although this method produces silicone particles, the particles do not remain in the particulate state after drying because of low cross‐linking density. The polymerization mechanism of this method was also investigated, which proceeds under the ring‐opening reaction of D4 in monomer droplets and upon polycondensation of hydrolyzed D4, which occurs in the water phase (ie, outside the monomer droplets). This mechanism implied that introducing the cross‐linking structure into particles is difficult because of the low solubility of bis‐D4 in water. To overcome these difficulties, we demonstrated a second method of preparing silicone particles based on the thiol‐Michael addition reaction between thiol‐terminated silicone oil and triacrylate in miniemulsion systems. Transmission electron microscopy images indicated that the silicone particles obtained in the particulate state upon drying and the aggregates of these particles showed elasticity. 相似文献
6.
Dr. Yoji Horii Dr. Keiichi Katoh Dr. Kunihisa Sugimoto Dr. Ryo Nakanishi Dr. Brian K. Breedlove Prof. Dr. Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3098-3104
In the research field of single-molecule magnets (SMMs), lanthanoid–lanthanoid interactions, so-called f–f interactions, are known to affect the SMM properties, although their magnitudes are small. In this article, an SMM with very weak f–f interactions is reported, and the effects of the interactions on the SMM properties are discussed. X-ray structural analysis of the DyIII-CdII-phthalocyaninato sextuple-decker complex (Dy2Cd3) reveals that the intramolecular Dy−Dy length in Dy2Cd3 is more than 13 Å, which is longer than the intermolecular Dy−Dy length. Even though the two DyIII ions are far apart, intermolecular ferromagnetic dipole–dipole interactions are observed in Dy2Cd3. From detailed analysis of ac magnetic susceptibilities, quantum tunneling of the magnetization (QTM) in Dy2Cd3 is partially suppressed owing to the existence of very weak Dy−Dy interactions. Our results show that even very weak Dy−Dy interactions act as a dipolar bias, suppressing QTM. 相似文献
7.
Kazunori Masuko Chiharu Kumano Ryo Sugawara Kazuhiro Nakabayashi Hideharu Mori 《Journal of polymer science. Part A, Polymer chemistry》2021,59(15):1664-1677
A series of amino-acid-based amphiphilic diblock copolymer nano-objects having different morphologies were developed by reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N-acryloyl amino acid) macro-chain transfer agents (CTAs), including three carboxylic-acid-containing ones, poly(N-acryloyl-l -proline) (PAProOH), poly(N-acryloyl-4-trans-hydroxy-l -proline) (PAHypOH), and poly(N-acryloyl-l -threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate-terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen-bonding and ionic interactions of the macro-CTAs on the assembled structures of the nano-objects were evaluated using six different macro-CTAs. Transforming the products from methanol to water via dialysis produced amino-acid-based block copolymer nano-objects, exhibiting pH-responsive morphological change, in aqueous solution. 相似文献
8.
Chikako Matsuda Ryo Igarashi Prof. Dr. Hiroshi Katagiri Dr. Takashi Murase 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200132
Tri- and tetra-fluorinated [7]helicenes are photolabile and undergo a double fluorine atom transfer. Herein, we show that the transferred product further undergoes a skeletal transformation on silica gel. The transformation begins with activation of the allylic C−F bond on the silanol surface. Then, the resulting carbocation readily undergoes a regioselective nucleophilic aromatic substitution with water, depending on the position of the fluorine substituents. Hexafluoro-2-propanol also activated the allylic C−F bond and acted as a nucleophile. These findings support the generation of a highly reactive cationic electrophilic intermediate in the successive transformations involving fluorine atoms. 相似文献
9.
Makoto Obata Ryo Asato Kazunori Mitsuo Shiho Hirohara 《Journal of polymer science. Part A, Polymer chemistry》2014,52(7):963-972
Three CF3‐substituted methyl methacrylates (MMAs), 2,2,2‐trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFIPMA) and nonafluoro‐tert‐butyl methacrylate (NFTBMA), were polymerized by conventional radical polymerization to give oxygen‐permeable polymers for application in pressure‐sensitive paint (PSP). The radical copolymerizations of styrene with TFEMA, HFIPMA, or NFTBMA were carried out to examine the effect of CF3 groups on the polymerizability. The e values increased in the order of MMA (0.40) < TFEMA (0.76) < HFIPMA (1.19) < NFTBMA (1.31). The homopolymers of TFEMA, HFIPMA and NFTBMA (PTFEMA, PHFIPMA, and PNFTBM, respectively) were examined as polymers for use in PSP using 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II) (PtTFPP). The PSP consisting of PNFTBMA and PtTFPP exerted very high pressure sensitivity and very low temperature sensitivity. In the absence of oxygen, the temperature sensitivity decreased in the order of PTFEMA > PHFIPMA > PNFTBMA = PMMA, which corresponds to the order of glass transition temperatures (Tg). However, the activation energies of the overall process of the luminescence quenching by oxygen were found to be 16.8 (PMMA), 13.0 (PTFEMA), 6.8 (PHFIPMA), and 4.3 kJ mol?1 (PNFTBMA). Therefore, the low temperature sensitivity of PNFTBMA was attributed to its high degree of substitution with CF3 groups and to its relatively high Tg value. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 963–972 相似文献
10.
Highly Chemoselective and Versatile Method for Direct Conversion of Carboxylic Acids to Ketones Utilizing Zinc Ate Complexes 下载免费PDF全文
Various carboxylic acids were directly transformed into the corresponding ketones by utilizing organozinc ate complexes, which provide high chemoselectivity without any overreaction to the undesired tertiary carbinol, owing to formation of a stable tetrahedral zincioketal intermediate. This method offers good overall atom/step/pot economy and operational simplicity. 相似文献