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121.
Langmuir-Blodgett(LB)技术可在二维气/液界面上精确地控制分子之间的排列及堆积方式, 构建有序超薄膜及纳米组装体. 同时, 界面这一不对称环境也可有效放大组装体的手性信息, 实现超分子体系中的手性传递和手性放大. 本文研究了萘环取代位置不同的两种手性两亲分子——N,N′-双十八烷基-α-萘-L-氨基-谷氨酸二酰胺(1NLG)和N,N′-双十八烷基-β-萘-L-氨基-谷氨酸二酰胺(2NLG)在气/液界面的铺展及组装行为, 发现同分异构效应影响了两亲分子在界面的排列, 1NLG组装形成了均一的纳米带状结构, 而2NLG则形成了左手螺旋结构, 并且2NLG薄膜表现出圆偏振发光(CPL)性质, 其不对称因子(glum)比三维体相组装体(超分子凝胶)大23倍, 表明界面促进了超分子手性的放大. 相似文献
122.
Simone Pilon Steen Ingemann Jørgensen Prof. Dr. Jan H. van Maarseveen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2310-2314
After earlier unsuccessful attempts, this work reports the application of covalent templating for the synthesis of mechanically interlocked molecules (MiMs) bearing no supramolecular recognition sites. Two linear strands were covalently connected in a perpendicular fashion by a central ketal linkage. After subsequent attachment of the first strand to a template via temporary benzylic linkages, the second was linked to the template in a backfolding macrocyclization. The resulting pseudo[1]rotaxane structure was successfully converted to a [2]catenane via a second macrocyclization and cleavage of the ketal and temporary linkages. 相似文献
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Helical Carbon and Graphite Films Prepared from Helical Poly(3,4‐ethylenedioxythiophene) Films Synthesized by Electrochemical Polymerization in Chiral Nematic Liquid Crystals
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Dr. Satoshi Matsushita Bairu Yan Shinsuke Yamamoto Dr. Yong Soo Jeong Prof. Kazuo Akagi 《Angewandte Chemie (International ed. in English)》2014,53(6):1659-1663
Helical carbon and graphite films from helical poly(3,4‐ethylenedioxythiophene) (H‐PEDOT) films synthesized through electrochemical polymerization in a chiral nematic liquid‐crystal (N*‐LC) field are prepared. The microscope investigations showed that the H‐PEDOT film synthesized in the N*‐LC has large domains of one‐handed spiral morphology consisting of fibril bundles. The H‐PEDOT films exhibited distinct Cotton effects in circular dichroism spectra. The highly twisted N*‐LC with a helical pitch of smaller than 1 μm produced the H‐PEDOT film with a highly ordered morphology. The spiral morphologies with left‐ and right‐handed screws were observed for the carbon films prepared from the H‐PEDOT films at 800 °C and were well correlated with the textures and helical pitches of the N*‐LCs. The spiral morphologies of the precursors were also retained even in the graphite films prepared from the helical carbon films at 2600 °C. 相似文献
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Synthesis of Chiral Exocyclic Amines by Asymmetric Hydrogenation of Aromatic Quinolin‐3‐amines
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Xian‐Feng Cai Ran‐Ning Guo Mu‐Wang Chen Lei Shi Prof. Yong‐Gui Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7245-7248
Asymmetric hydrogenation of aromatic quinolin‐3‐amines was successfully developed with up to 94 % enantiomeric excess (ee). Introduction of the phthaloyl moiety to the amino group is crucial to eliminate the inhibition effect caused by the substrate and product, to activate the aromatic ring, and to improve the diastereoselectivity. This new methodology provides direct and facile access to chiral exocyclic amines. Notably, this report is the first on the highly enantioselective hydrogenation of aromatic amines. 相似文献
127.
Localized Crystallization of Enantiomeric Organic Compounds on Chiral Micro‐patterns from Various Organic Solutions
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Dr. Maarten W. van der Meijden Prof. Richard M. Kellogg Prof. David B. Amabilino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10466-10474
The controlled crystallization of enantiomers of an organic compound (a cyclic phosphoric acid derivative) on templated micro‐patterned functionalised surfaces is demonstrated. Areas where a complementary chiral thiol has been located were effective heterogeneous nucleation centres when a solution of the compound is evaporated slowly. Various organic solvents were employed, which present a challenge with respect to other examples when water is used. The solvent and the crystallization method have an important influence on the crystal growth of these compounds. When chloroform was employed, well‐defined crystals grow away from the surface, whereas crystals grow in the plane from solutions in isopropanol. In both cases, nucleation is confined to the polar patterned regions of the surface, and for isopropanol growth is largely limited within the pattern, which shows the importance of surface chemistry for nucleation and growth. The apparent dependence on the enantiomer used in the latter case could imply stereo‐differentiation as a result of short‐range interactions (the templating monolayer is disordered, even at the nanometre scale). The size of the pattern of chiral monolayer also determines the outcome of the crystallization; 5 μm dots are most effective. Despite the low surface tension of the samples (relative to the high surface tension of water), differential solvation of the polar and hydrophobic layers of the solvents allows crystallization in the polar regions of the monolayer, therefore the polarity of the regions in which heterogeneous nucleation takes place is indeed very important. Despite the complex nature of the crystallization process, these results are an important step towards to the use of patterned surfaces for heterogeneous selective nucleation of enantiomers. 相似文献
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Control of Chiral Nanostructures by Self‐Assembly of Designed Amphiphilic Peptides and Silica Biomineralization
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Zhehao Huang Dr. Yuan Yao Dr. Lu Han Prof. Shunai Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):17068-17076
Peptides, the fundamental building units of biological systems, are chiral in molecular scale as well as in spatial conformation. Shells are exquisite examples of well‐defined chiral structures produced by natural biomineralization. However, the fundamental mechanism of chirality expressed in biological organisms remains unclear. Here, we present a system that mimics natural biomineralization and produces enantiopure chiral inorganic materials with controllable helicity. By tuning the hydrophilicity of the amphiphilic peptides, the chiral morphologies and mesostructures can be changed. With decreasing hydrophilicity of the amphiphilic peptides, we observed that the nanostructures changed from twisted nanofibers with a hexagonal mesostructure to twisted nanoribbons with a lamellar mesostructure, and the extent of the helicity decreased. Defining the mechanism of chiral inorganic materials formed from peptides by noncovalent interactions can improve strategies toward the bottom‐up synthesis of nanomaterials as well as in the field of bioengineering. 相似文献
130.