排序方式: 共有130条查询结果,搜索用时 15 毫秒
71.
Risa Suzuki Yuto Uziie Wataru Fujiwara Hiroshi Katagiri Takashi Murase 《化学:亚洲杂志》2020,15(8):1330-1338
The partial fluorination of polycyclic aromatic hydrocarbons often produces a layered crystal packing, where fluorinated aromatic surfaces are stacked over nonfluorinated aromatic surfaces. Herein, we report the synthesis and crystal packing of partially fluorinated [4]helicenes with steric congestion resulting from H and F atoms in the fjord region. F6‐[4]Helicene forms head‐to‐tail columnar stacks consisting of an alternate arrangement of perfluorinated and nonfluorinated naphthalene moieties. With decreasing fluorine content, aromatic stacking switched from arene?fluoroarene (ArH?ArF) hetero‐stacking to ArH?ArH/ArF?ArF homo‐stacking with the help of intermolecular C?H???F contacts in the fjord region. As a result, head‐to‐head columnar stacks appear. Therefore, the conventional ArH?ArF stacking motif is not always applicable to Fn‐[4]helicenes with twisted π‐surfaces. 相似文献
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A rat model of neonatal hypoxic-ischemic encephalopathy (Rice's model) was obtained by unilateral ligation of the common carotid artery of 7-day-old rats with hypoxia (exposure to 8% oxygen). To estimate the in vivo intracerebral reducing ability of the mature rats (8 weeks old) of Rice's model, temporal electron paramagnetic resonance (EPR) imaging of the brain of a rat receiving a blood-brain barrier-permeable nitroxide radical, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, was performed. In this imaging technique, the decay rate of the EPR signal intensity in a selected region of the brain is indicative of region-specific reducing ability. The effect of neonatal treatment of an antioxidant agent, 3-methyl-1-phenyl-2-pyrazolin-5-one (MCI-186), after a hypoxic-ischemic insult was also tested. It was found that the reducing ability had been depleted in the contralateral hemisphere of Rice's model rats; this depletion was suppressed by administering MCI-186. 相似文献
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Papidly curable hydrogels were prepared through chemical crosslinking of gelatin with poly(carboxylic acid)s including poly (L-glutamic acid) (PLGA), hyaluronic acid (HA), and poly (acrylic acid) (PAA) by use of water-soluble carbodiimide (WSC). The effects of the nature of added poly (carboxylic acid)s on gelation of mixed gelatinpoly (carboxylic acid) aqueous solutions and adhesion of the resulting hydrogels to the mouse skin were evaluated. The addition of poly (carboxylic acid) s reduced the gelation time of gelatin aqueous solutions except for HA. Mixed gelatin-PLGA solutions were cured more rapidly than other mixed solutions and the gelation time was shortened with the increasing PLGA molecular weight. The resulting gelatin-PLGA hydrogels exhibited stronger adhesion to the mouse skin than gelatin-HA and gelatin-PAA hydrogels. The bonding strength increased with the increase in PLGA molecular weight up to 83,000 and thereafter decreased. The longer gelation time and lower adhesion of the gelatin-PAA hydrogels than the gelatin-PLGA hydrogels seem to be due to poorer compatibility of gelatin with PAA than with PLGA. The mixed gelatin-PLGA solution underwent phase separation when the concentration and molecular weight of PLGA became higher than a threshold. The insignificant or suppressive effect of HA addition might be ascribed to the HA-WSC reaction which was the least effective in hydrogel formation. 相似文献
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Yuto Hino Shotaro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》2024,62(9):1915-1921
3,4-Appended thiophene monomers furnish unique optoelectronic properties due to electronic and steric effects on the donor unit. Here, we have demonstrated a new polymer synthesis by direct arylation polycondensation of 9,10-dihydro-9,10-[3,4]thiophenoanthracene, a thiophene-based monomer. Chloride-promoted direct arylation polycondensation of 9,10-dihydro-9,10-[3,4]thiophenoanthracene with dibromo monomers with acetate in N,N-dimethylacetamide gave conjugated alternating copolymers. The obtained polymer had a molecular weight of 38,000 and exhibited high film-forming ability. The optical and electrochemical properties of the polymers were also discussed. 相似文献
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Dr. Ami Nishijima Yuto Osugi Prof. Dr. Takashi Uemura 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(17):e202404155
Metal–organic cages (MOCs), which are formed via coordination-driven assembly, are being extensively developed for various applications owing to the utility of their accessible molecular-sized cavity. While MOC structures are uniquely and precisely predetermined by the metal coordination number and ligand configuration, tailoring MOCs to further modulate the size, shape, and chemical environment of the cavities has become intensively studied for a more efficient and adaptive molecular binding. Herein, we report self-expanding MOCs that exhibit remarkable structural variations in cage size and flexibility while maintaining their topology. A cyclic ligand with an oligomeric chain tethering the two benzene rings of stilbene was designed and mixed with RhII ions to obtain the parent MOCs. These MOCs were successfully transformed into expanded MOCs via the selective cleavage of the double bond in stilbene. The expanded MOCs could effectively trap multidentate N-donor molecules in their enlarged cavity, in contrast to the original MOCs with a narrow cavity. As the direct synthesis of expanded MOCs is impractical because of the entropically disfavored structures, self-expansion using ring-openable ligands is a promising approach that allows precision engineering and the production of functional MOCs that would otherwise be inaccessible. 相似文献
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Yukita Shunpei Suzuki Yuto Shiokawa Naoyuki Kobayashi Takayoshi Tokunaga Eiji 《Optical Review》2018,25(2):205-214
Optical Review - The “anomalous” Pockels effect is a phenomenon that a light beam passing between two electrodes in an aqueous electrolyte solution is deflected by an AC voltage applied... 相似文献
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The global and macrocyclic aromaticity of porphyrinoids was characterized using our graph theory of aromaticity. The sequential line plots of topological resonance energy (TRE) against the number of π-electrons (N(π)) for different porphyrinoids are similar with four major extrema to those for five-membered heterocycles. This supports the view that five-membered rings are the main origin of global aromaticity in porphyrinoids. Macrocyclic circuits contribute significantly to macrocyclic π-circulation but modestly to global aromaticity. Macrocyclic aromaticity/antiaromaticity in oligopyrrolic macrocycles can be predicted by formally applying Hückel's [4n + 2] rule to an annulene-like main macrocyclic conjugation pathway (MMCP). This bridged annulene model can be justified by examining the contribution of individual macrocyclic circuits to macrocyclic aromaticity. A Hückel-like rule of macrocyclic aromaticity was found for porphyrinoid species. 相似文献
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