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101.
Yuki Kataoka Dr. Naoya Kanbayashi Naoka Fujii Dr. Taka-aki Okamura Prof. Takeharu Haino Prof. Kiyotaka Onitsuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10372-10377
π-Stacked polymers, which consist of layered π-electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π-stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π-stacked architecture based on poly(quinolylene-2,3-methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo-copolymerization of an o-allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted-tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic-force microscopy. 相似文献
102.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献
103.
We investigated the fluorescent properties, including the excited-state intermolecular proton transfer, of urea derivatives comprising a coumarin ring, which is a widely used fluorophore. We prepared two different coumarin–urea derivatives, 6CU and 7CU, which bear a urea-based substituent at the 6 and 7 positions of a coumarin ring, respectively. In the presence of the acetate ion, 7CU showed additional tautomer fluorescence emission with respect to 6CU, indicating that tautomer formation depends on the positions of the urea-based substituent on the coumarin ring. Thus, the resonance structures of urea derivatives might play an important role in the behavior of dual fluorescence, which is an important phenomenon applicable to photochemical anion sensing. Moreover, in order to further improve the fluorescence properties of the mentioned derivatives, a CF3 group was introduced in a phenyl ring opposite to a coumarin ring. The fluorescence quantum yield of 7CUCF3 thus synthesized was 65 times as large as that of 7CU, an observation that renders 7CUCF3 a suitable anion sensor candidate. The results of this study will contribute to the development of new molecular designs for highly fluorescent sensing. 相似文献
104.
Yuki Kataoka Naoya Kanbayashi Naoka Fujii Taka‐aki Okamura Takeharu Haino Kiyotaka Onitsuka 《Angewandte Chemie (International ed. in English)》2020,59(26):10286-10291
π‐Stacked polymers, which consist of layered π‐electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π‐stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π‐stacked architecture based on poly(quinolylene‐2,3‐methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo‐copolymerization of an o‐allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted‐tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic‐force microscopy. 相似文献
105.
Mami Miyairi Tsuyoshi Taniguchi Tatsuya Nishimura Katsuhiro Maeda 《Angewandte Chemie (International ed. in English)》2020,59(35):14772-14780
An alternative reaction mechanism of the polymerization of diphenylacetylelnes using a catalytic system composed of tungsten(VI) chloride and tetraphenyltin has been proposed through the optimization of reaction conditions and investigation of the effect of the electronic nature of diphenylacetylene monomers on the polymerizability. The detailed structures of the polymers have been suggested by mass spectrometric analysis of the obtained polymers and oligomers, which suggested that a phenyl group of tetraphenyltin has been introduced to an initiating end of the polymer chain. Mass spectrometric analysis also provided information about the termination processes of the polymerization. The experimental results strongly suggested that the polymerization of diphenylacetylenes using tungsten(VI) chloride and tetraphenyltin proceeds through a migratory insertion mechanism rather than the long‐accepted metathesis mechanism. 相似文献
106.
Naoya Onishi Ryoichi Kanega Hajime Kawanami Yuichiro Himeda 《Molecules (Basel, Switzerland)》2022,27(2)
Recently, there has been a strong demand for technologies that use hydrogen as an energy carrier, instead of fossil fuels. Hence, new and effective hydrogen storage technologies are attracting increasing attention. Formic acid (FA) is considered an effective liquid chemical for hydrogen storage because it is easier to handle than solid or gaseous materials. This review presents recent advances in research into the development of homogeneous catalysts, primarily focusing on hydrogen generation by FA dehydrogenation. Notably, this review will aid in the development of useful catalysts, thereby accelerating the transition to a hydrogen-based society. 相似文献
107.
Keisuke Kurita Shin-Ichi Watabe Shin-Ichiro Nishimura Shigeru Ishii 《Journal of polymer science. Part A, Polymer chemistry》1996,34(3):429-438
Linear polybiurets have been synthesized by polyaddition of benzyloxyamine and diisocyanates, and properties of the novel polymeric materials have been elucidated. Prior to polymerization, model reactions between benzyloxyamine and phenyl isocyanate were examined in detail and proved to be controlled by the molar ratio of reagents and by catalysts to give the urea (1:1 adduct) and/or biuret (1:2 adduct). Under appropriate conditions, the biuret was synthesized in a quantitative yield. Polymerization of equimolar amounts of benzyloxyamine and diphenylmethane or hexamethylene diisocyanate proceeded smoothly to give polybiurets with inherent viscosities up to 0.52 dL/g. The benzyl group of the model biuret and polybiuret could be removed by catalytic hydrogenation. Both the N-benzyloxy-type and N-hydroxy-type polybiurets showed excellent solubility in common organic solvents. The two kinds of polybiurets as well as model biurets adsorbed metal cations efficiently. The N-hydroxybiuret structure exhibited particularly high affinity for iron(III) and was useful for selective removal of iron from metal cation mixtures. © 1996 John Wiley & Sons, Inc. 相似文献
108.
Prof. Makoto Tadokoro Masaki Itoh Ryota Nishimura Kensuke Sekiguchi Dr. Norihisa Hoshino Dr. Hajime Kamebuchi Prof. Jun Miyazaki Dr. Fumiya Kobayashi Prof. Motohiro Mizuno Prof. Tomoyuki Akutagawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201397
A new H-bonded crystal [RuIII(Him)3(Im)3] with three imidazole (Him) and three imidazolate (Im−) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the RuIII complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10−5 S cm−1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [RuIII(Him)3(Im)3] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state 2H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered. 相似文献
109.
Takegawa Y Deguchi K Ito H Keira T Nakagawa H Nishimura S 《Journal of separation science》2006,29(16):2533-2540
Asparagine-linked oligosaccharides (N-glycans) usually show structural heterogeneity, especially in proteins with sialylated N-glycans and, therefore, their structural analysis is still very difficult. A zwitterionic type of hydrophilic interaction chromatography column with sulfobetaine functional groups (called a ZIC-HILIC column) was applied to the separation of tryptic peptides of alpha-1-acid glycoprotein. It was demonstrated that the ZIC-HILIC separation column has a selectivity for sialylated N-glycopeptides and a high capability for separation based on the structural recognition of sialylated N-glycan isomers as well as for the previously reported neutral N-glycans and N-glycopeptides. The retention characteristics of neutral and sialylated N-glycans derivatized with 2-aminopyridine (PA N-glycans) demonstrate that the retentions of the N-glycans are based primarily on hydrophilic interaction with the water-rich liquid layer generated on the surface of the ZIC-HILIC column. In addition, the electrostatic repulsion interaction shielded with counter ions effectively tunes the separation and recognition of sialylated N-glycan isomers. 相似文献
110.
Deguchi K Keira T Yamada K Ito H Takegawa Y Nakagawa H Nishimura S 《Journal of chromatography. A》2008,1189(1-2):169-174
A novel chromatographic approach coupling anion-exchange (diethylaminoethylene) and hydrophilic-interaction (amide or zwitterionic type) columns was developed for the separating of 2-pyridylamino derivatives of N-glycans (PA-N-glycans). This is a kind of on-line, two-dimensional (2D) separation approach in hydrophilic-interaction chromatography (called the 2D-HILIC method), analogous to that of coupling cation- (or anion-, or mixed ion-) exchange and reversed-phase columns in hydrophobic interaction (reversed-phase) chromatography. The efficiency of the 2D-HILIC method was tested with biantennary neutral and sialylated PA-N-glycan standards by properly combining linear gradient elutions of water-acetonitrile and spiked-salt (ammonium acetate) elutions. The retention time RSDs of all the peaks in three sequential runs of a 100 min cycle are less than 0.52%, which indicates a reasonably good repeatability of the 2D-HILIC method. Then, the method was applied to a complex mixture of PA-N-glycans from human serum proteins. It was demonstrated that the neutral PA-N-glycans and mono-, di-, tri-, and tetrasialylated PA-N-glycans are able to be eluted in turn according to the number of sialic acids in an automated (programmed) single run. 相似文献