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981.
Prof. Hidemitsu Uno Kota Muramatsu Shogo Hiraoka Hiroyuki Tahara Mako Hirose Eidai Tamura Tatsumi Shiraishi Dr. John Mack Prof. Nagao Kobayashi Dr. Shigeki Mori Dr. Tetsuo Okujima Dr. Masayoshi Takase 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5701-5708
A bicyclo[2.2.2]octadiene(BCOD)-fused bis(dipyrromethane) derivative was reacted with methylal in the presence of trifluoroacetic acid followed by oxidation with chloranil to give a doubly N-confused phlorin derivative, which did not undergo the retro-Diels–Alder reaction extruding an ethylene molecule on heating. In contrast, a 7-tert-butoxybicyclo[2.2.1]heptadiene(7-BuOBCHD)-fused bis(dipyrromethane) yielded benzene-ring-fused doubly N-confused porphyrins by following similar reaction sequences. 相似文献
982.
Dr. Honghong Fan Dr. Farzaneh Bahmani Dr. Yusuf Valentino Kaneti Dr. Yanna Guo Prof. Asma A. Alothman Prof. Xinglong Wu Prof. Yusuke Yamauchi Prof. Wenliang Li Prof. Jingping Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(60):13652-13658
Binary transition-metal oxides (BTMOs) with hierarchical micro–nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe2O4 (cl-CoFe2O4) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro–nano-structure can promote fast ion transport and stable electrode–electrolyte interfaces. As a result, the cl-CoFe2O4 can deliver a high specific capacity (1019.9 mAh g−1 at 0.1 A g−1), excellent rate capability (626.0 mAh g−1 at 5 A g−1), and good cyclability (675.4 mAh g−1 at 4 A g−1 for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and −25 °C, the cl-CoFe2O4 anode can deliver high capacities of 907.5 and 664.5 mAh g−1 at 100 mA g−1, respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO4 cathode exhibits a high rate performance (214.2 mAh g−1 at 5000 mA g−1) and an impressive cycling performance (612.7 mAh g−1 over 140 cycles at 300 mA g−1) in the voltage range of 0.5–3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe2O4 is dominated by pseudocapacitive behavior, leading to fast Li+ insertion/extraction and good cycling life. 相似文献
983.
Yusuke Matsuo Dr. Takayuki Tanaka Prof. Dr. Atsuhiro Osuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8144-8152
N,N’-Diarylated tetrabenzotetraaza[8]circulenes 3 a and 3 b were synthesized in good yields by a reaction sequence involving oxidation of tetrabenzodiazadithia[8]circulene 5-Oct and SNAr reaction with aniline derivatives. The obtained aza[8]circulenes 3 a and 3 b were easily oxidized to give their radical cations 3 a+ and 3 b+ , which are highly stable under ambient conditions. X-ray diffraction analysis of radical cation 3 a+ showed a face-to-face dimer arrangement with an interplanar separation of 3.320 Å. The spin density of 3 a+ was calculated to be delocalized over the whole circulene π-systems with spin–spin exchange integral (J=−144 cm−1) in the dimeric part. These radical cations displayed far red-shifted absorption bands reaching to 2000 nm. Thus this study has proved the hetero[8]circulene scaffold to be a new entry of promising electronics and spin materials. 相似文献
984.
We review recent developments in the preparation of mesoporous metals and related metal‐based nanomaterials. Among the many types of mesoporous materials, mesoporous metals hold promise for a wide range of potential applications, such as in electronic devices, magnetic recording media, and metal catalysts, owing to their metallic frameworks. Mesoporous metals with highly ordered networks and narrow pore‐size distributions have traditionally been produced by using mesoporous silica as a hard template. This method involves the formation of an original template followed by deposition of metals within the mesopores and subsequent removal of the template. Another synthetic method is the direct‐template approach from lyotropic liquid crystals (LLCs) made of nonionic surfactants at high concentrations. Direct‐template synthesis creates a novel avenue for the production of mesoporous metals as well as related metal‐based nanomaterials. Many mesoporous metals have been prepared by the chemical or electrochemical reduction of metal salts dissolved in aqueous LLC domains. As a soft template, LLCs are more versatile and therefore more advantageous than hard templates. It is possible to produce various nanostructures (e.g., lamellar, 2D hexagonal (p6mm), and 3D cubic (Ia d)), nanoparticles, and nanotubes simply by controlling the composition of the reaction bath. 相似文献
985.
Tomonori Mori Dr. Shuhei Higashibayashi Dr. Taiji Goto Mitsunori Kohno Yukiko Satouchi Kazuyuki Shinko Kengo Suzuki Shunya Suzuki Hiraku Tohmiya Kimiko Hashimoto Prof. Dr. Masaya Nakata Prof. Dr. 《化学:亚洲杂志》2008,3(6):1013-1025
The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ). 相似文献
986.
Periodically Arranged Arrays of Dendritic Pt Nanospheres Using Cage‐Type Mesoporous Silica as a Hard Template 下载免费PDF全文
Kenya Kani Dr. Victor Malgras Dr. Bo Jiang Dr. Md. Shahriar A. Hossain Prof. Saad M. Alshehri Prof. Tansir Ahamad Dr. Rahul R. Salunkhe Dr. Zhenguo Huang Prof. Yusuke Yamauchi 《化学:亚洲杂志》2018,13(1):106-110
Dendritic Pt nanospheres of 20 nm diameter are synthesized by using a highly concentrated surfactant assembly within the large‐sized cage‐type mesopores of mesoporous silica (LP‐FDU‐12). After diluting the surfactant solution with ethanol, the lower viscosity leads to an improved penetration inside the mesopores. After Pt deposition followed by template removal, the arrangement of the Pt nanospheres is a replication from that of the mesopores in the original LP‐FDU‐12 template. Although it is well known that ordered LLCs can form on flat substrates, the confined space inside the mesopores hinders surfactant self‐organization. Therefore, the Pt nanospheres possess a dendritic porous structure over the entire area. The distortion observed in some nanospheres is attributed to the close proximity existing between neighboring cage‐type mesopores. This new type of nanoporous metal with a hierarchical architecture holds potential to enhance substance diffusivity/accessibility for further improvement of catalytic activity. 相似文献
987.
Dr. Meicheng Wen Dr. Kohsuke Mori Dr. Yasutaka Kuwahara Prof. Taicheng An Prof. Hiromi Yamashita 《化学:亚洲杂志》2018,13(14):1767-1779
Single‐site photocatalysts generally display excellent photocatalytic activity and considerably high stability compared with homogeneous catalytic systems. A rational structural design of single‐site photocatalysts with isolated, uniform, and spatially separated active sites in a given solid is of prime importance to achieve high photocatalytic activity. Intense attention has been focused on the design and fabrication of single‐site photocatalysts by using porous materials as a platform. Metal–organic frameworks (MOFs) have great potential in the design and fabrication of single‐site photocatalysts due to their remarkable porosity, ultrahigh surface area, extraordinary tailorability, and significant diversity. MOFs can provide an abundant number of binding sites to anchor active sites, which results in a significant enhancement in photocatalytic performance. In this focus review, the development of single‐site MOF photocatalysts that perform important and challenging chemical redox reactions, such as photocatalytic H2 production, photocatalytic CO2 conversion, and organic transformations, is summarized thoroughly. Successful strategies for the construction of single‐site MOF photocatalysts are summarized and major challenges in their practical applications are noted. 相似文献
988.
Dr. Takahiro Mori Xin Sun Dr. Stanislav Kadlcik Dr. Jiri Janata Prof. Dr. Ikuro Abe 《Angewandte Chemie (International ed. in English)》2023,62(29):e202304989
The S-glycosyltransferase LmbT, involved in the biosynthesis of lincomycin A, is the only known enzyme that catalyzes the enzymatic incorporation of rare amino acid L-ergothioneine (EGT) into secondary metabolites. Here, we show the structure and function analyses of LmbT. Our in vitro analysis of LmbT revealed that the enzyme shows promiscuous substrate specificity toward nitrogenous base moieties in the generation of unnatural nucleotide diphosphate (NDP)-D-α-D-lincosamides. Furthermore, the X-ray crystal structures of LmbT in its apo form and in complex with substrates indicated that the large conformational changes of the active site occur upon binding of the substrates, and that EGT is strictly recognized by salt-bridge and cation-π interactions with Arg260 and Trp101, respectively. The structure of LmbT in complex with its substrates, the docking model with the EGT-S-conjugated lincosamide, and the structure-based site-directed mutagenesis analysis revealed the structural details of the LmbT-catalyzed SN2-like S-glycosylation reaction with EGT. 相似文献
989.
Dr. Kazuhisa Yamasumi Kentaro Ueda Dr. Yohei Haketa Dr. Yusuke Hattori Prof. Masayuki Suda Prof. Shu Seki Dr. Hayato Sakai Prof. Taku Hasobe Ryoya Ikemura Prof. Yoshitane Imai Dr. Yukihide Ishibashi Prof. Tsuyoshi Asahi Dr. Kazuto Nakamura Prof. Hiromitsu Maeda 《Angewandte Chemie (International ed. in English)》2023,62(8):e202216013
Squarylium-based π-electronic cation with an augmented dipole was synthesized by methylation of zwitterionic squarylium. The cation formed various ion pairs in combination with anions, and the ion pairs exhibited distinct photophysical properties in the dispersed state, ascribed to the formation of J- and H-aggregates. The ion pairs provided solid-state assemblies based on cation stacking. It is noteworthy that complete segregation of cations and anions was observed in a pseudo-polymorph of the ion pair with pentacyanocyclopentadienide as a π-electronic anion. In the crystalline state, the ion pairs exhibited photophysical properties and electric conductivity derived from cation stacking. In particular, the charge-segregated ion-pairing assembly induces an electric conductive pathway along the stacking axis. The charge-segregated mode and fascinating properties were derived from the reduced electrostatic repulsion between adjacent π-electronic cations via dipole–dipole interactions. 相似文献
990.
Yusuke Hioki Dr. Tatsuya Sato Dr. Toyoki Iwao Junya Ikuma Dr. Atsushi Kawamura Dr. Takayuki Ohyoshi Dr. Yuta Tsunematsu Dr. Masaki Kita 《European journal of organic chemistry》2023,26(12):e202300084
The shell-less herbivorous marine mollusk (sea hare) Aplysia kurodai is known to contain a variety of bioactive substances. While these compounds have been thought to originate from sea algae or their associated microbes, most of their origin and acquisition pathways are still unclear. Six new cytotoxic aplaminone derivatives, bromodopamine-terpenoid hybrid molecules, were isolated from A. kurodai. Among them, isoaplaminone had a reverse prenyl group at the C15 aliphatic chain, which is a rare structural feature from the viewpoint of terpenoid biosynthesis. Investigation for chemical components in A. kurodai and the sea algae collected at several different locations revealed that two major aplaminones were contained in the Laurencia complex species at specific sites. Our chemical and ecological studies provide new insights into the origin of marine alkaloid toxins and their dynamism through the food chain. 相似文献