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151.
Kobayashi Y Katakami H Mine E Nagao D Konno M Liz-Marzán LM 《Journal of colloid and interface science》2005,290(2):392-396
Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory. 相似文献
152.
Mitsunori Honda Sho Sasaki Tsuyoshi Nishimoto Hiromoto Koshiro Ko-Ki Kunimoto Masahito Segi 《Tetrahedron letters》2018,59(42):3777-3781
The synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring was investigated. The reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes derived from α,β-unsaturated aldehydes did not afford the desired acylsilane derivatives. Instead, the corresponding silyl enol ethers were yielded exclusively. On the other hand, the Corey-Chaykovsky cyclopropanation of α-substituted α,β-unsaturated aldehydes proceeded well to give 1-substituted cyclopropyl aldehydes. The silyl substitution of formyl proton in the obtained aldehydes via umpolung of carbonyl group afforded the target acylsilanes. 相似文献
153.
Dr. Sho Hirai Dr. Patchiya Phanthong Tsubasa Wakabayashi Prof. Shigeru Yao 《ChemistryOpen》2021,10(3):352-359
Porous polyimide (PI) membranes are widely used in separation processes because of their excellent thermal and mechanical properties. However, the applications of porous PI membranes are limited in the nanofiltration range. In this study, porous PI membranes with through-holes have been successfully fabricated by the novel multiple solvent displacement method. This new method requires only a porous polyamic acid (PAA) membrane, which was prepared by immersing PAA film in N-methylpyrrolidoneebk; (NMP) prior to immersing it in a mixed solvent consisting of NMP and a poor solvent, followed by immersion only in poor solvent. The pore size, morphology, porosity, and air permeability demonstrated that the fabricated PI membranes had a uniformly porous structure with through-holes over their surface. This new method enabled control of pore size (3–11 μm) by selecting a suitable poor solvent. This multiple solvent displacement method is highly versatile and promising for the fabrication of porous PI membranes. 相似文献
154.
Dr. Shunpei Hitosugi Prof. Kei Ohkubo Yuki Kawashima Dr. Taisuke Matsuno Sho Kamata Kosuke Nakamura Hirohiko Kono Dr. Sota Sato Prof. Shunichi Fukuzumi Prof. Hiroyuki Isobe 《化学:亚洲杂志》2015,10(11):2404-2410
The energetics and photodynamics of carbonaceous molecular bearings with discrete molecular structures were investigated. A series of supramolecular bearings comprising belt‐persistent tubular cycloarylene and fullerene molecules accepted photonic stimuli to afford charge‐separated species via a photoinduced electron transfer process. The energy conversion processes associated with the photoexcitation, however, differed depending on the molecular structure. A π‐lengthened tubular molecule allowed for the emergence of an intermediary triplet excited state at the bearing, which should lead to an energy conversion to thermal energy. On the other hand, low‐lying charge‐separated species induced by an endohedral lithium ion in fullerene enabled back electron transfer processes to occur without involving triplet excited species. The structure–photodynamics relationship was analyzed in terms of the Marcus theory to reveal a large electronic coupling in this dynamic supramolecular system. 相似文献
155.
Isao Ando Yige Yin Chenhua Zhao Sho Kanesaka Shigeki Kuroki 《Macromolecular Symposia》2005,220(1):61-74
In this lecture the measurements and analyses of the isotropic and anisotropic diffusion coefficients(D) of rod-like polypeptide such as poly(γ-L-glutamate)(PLG) with n-alkyl side chains, of which the main chain takes the α-helical conformation, as a function of the main chain length in the thermotropic and lyotropic liquid crystalline phases over a wide range of temperatures from 30 to 80°C by means of pulse high field-gradient spin echo 1H NMR method have been introduced. In the anisotropic diffusion, the D∥ value in direction parallel to the α-helical chain axis is found to be much larger than the D⊥ value in direction perpendicular to the α-helical chain axis. The diffusion process is followed by the Kirkwood theory. Further, it is described that the diffusion in the nematic liquid crystalline phase is much slower than that in the isotropic phase. 相似文献
156.
Maika Kawaura Takumi Aizawa Sho Takahashi Hiroshi Miyasaka Hikaru Sotome Shiki Yagai 《Chemical science》2022,13(5):1281
Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π–π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π–π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl3, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.Two barbiturate dyes with regioisomeric thiophene-cored twisted π-systems show strongly enhanced emission through supramolecular polymerization. The supramolecular polymers thus formed exhibit distinct emission colors and degree of agglomeration. 相似文献
157.
Yuji Kikukawa Hiromasa Kitajima Sho Kuwajima Yoshihito Hayashi 《Molecules (Basel, Switzerland)》2020,25(23)
A calix-shaped polyoxometalate, [V12O32]4− (V12), stabilizes an anion moiety in its central cavity. This molecule-sized container has the potential to control the reactivity of an anion. The highly-reactive cyanate is smoothly trapped by V12 to form [V12O32(CN)]5−. In the CH3NO2 solution, cyanate abstracts protons from CH3NO2, and the resultant CH2NO2− is stabilized in V12 to form [V12O32(CH2NO2)]5− (V12(CH2NO2)). A crystallographic analysis revealed the double-bond characteristic short bond distance of 1.248 Å between the carbon and nitrogen atoms in the nitromethane anion in V12. 1H and 13C NMR studies showed that the nitromethane anion in V12 must not be exchanged with the nitromethane solvent. Thus, the V12 container restrains the reactivity of anionic species. 相似文献
158.
Masaya Nakajima Sho Nagasawa Koki Matsumoto Takahito Kuribara Atsuya Muranaka Masanobu Uchiyama Tetsuhiro Nemoto 《Angewandte Chemie (International ed. in English)》2020,59(17):6847-6852
According to the Grotthuss–Draper law, light must be absorbed by a substrate to initiate a photoreaction. There have been several reports, however, on the promotion of photoreactions using hypervalent iodine during irradiation with light from a non‐absorbing region. This contradiction gave rise to a mystery regarding photoreactions involving hypervalent iodine. We demonstrated that the photoactivation of hypervalent iodine with light from the apparently non‐absorbing region proceeds via a direct S0→Tn transition, which has been considered a forbidden process. Spectroscopic, computational, and synthetic experimental results support this conclusion. Moreover, the photoactivation mode could be extended to monovalent iodine and bromine, as well as bismuth(III)‐containing molecules, providing new possibilities for studying photoreactions that involve heavy‐atom‐containing molecules. 相似文献
159.
Toshinori Miyagi Sho Okada Naoya Tada Masahiro Sugihara Natsuko Kagawa Tetsuhiko Takabatake Masahiro Toyota 《Tetrahedron letters》2019,60(25):1653-1657
A Pd-catalyzed orthogonal synthesis of substituted 2-hydroxybenzoates and substituted cyclohexanones was developed for the first time. The substituted 2-hydroxybenzoates were obtained from acyclic unsaturated 1,3-carbonyl compounds using a combination of catalytic Pd(OAc)2 and Cu(OAc)2. On the other hand, the substituted cyclohexanones were produced from similar substrates via catalytic Pd(OAc)2 and hydrogen chloride. Each transformation was clean, easy to work up, provided the desired compounds in good purities, and did not require column chromatography purification. 相似文献
160.
Mingoo Jin Sho Yamamoto Tomohiro Seki Hajime Ito Miguel A. Garcia‐Garibay 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18171-18178
Herein we report a crystalline molecular rotor with rotationally modulated triplet emission that displays macroscopic dynamics in the form of crystal moving and/or jumping, also known as salient effects. Molecular rotor 2 with a central 1,4‐diethynyl‐2,3‐difluorophenylene rotator linked to two gold(I) nodes, crystalizes as infinite 1D chains through intermolecular gold(I)–gold(I) interactions. The rotational motion changes the orientation of the central phenylene, changing the electronic communication between adjacent chromophores, and thus the emission intensities. Crystals of 2 showed the large and reversible thermal expansion/compression anisotropy, which accounts for 1) a nonlinear Arrhenius behavior in molecular‐level rotational dynamics, which correlates with 2) changes in emission, and determines 3) the macroscopic crystal motion. A molecular rotor analogue 3 has properties similar to those of 2 , suggesting a generalized way to control mechanical properties at molecular and macroscopic scales. 相似文献