排序方式: 共有18条查询结果,搜索用时 31 毫秒
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Masumi Asakawa Peter R. Ashton Vincenzo Balzani Alberto Credi Christoph Hamers Gunter Mattersteig Marco Montalti Andrew N. Shipway Neil Spencer J. Fraser Stoddart Malcolm S. Tolley Margherita Venturi Andrew J. P. White David J. Williams 《Angewandte Chemie (International ed. in English)》1998,37(3):333-337
A mechanical switch in a [2]catenane , made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides “inside” the tetracationic cyclophane in the reduced state and “alongside” it in the oxidized species (TTF+/ TTF2+). Switching between the reduced (I4+) and oxidized state (I5+(I6+)) is accompanied by a dramatic color change. 相似文献
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Soo‐Gyun Roh Ki‐Min Park Gil‐Jae Park Shigeru Sakamoto Kentaro Yamaguchi Kimoon Kim 《Angewandte Chemie (International ed. in English)》1999,38(5):637-641
Like with a string of pearls , four molecular “beads” are threaded on a molecular rectangle to form a molecular necklace. This rectangular species is synthesized from two L‐shaped, preorganized pseudorotaxanes with two molecular beads each (cucurbituril, schematically symbolized by the barrels), held together by Cu2+ ions [Eq. (1)]. 相似文献
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Nadrian C. Seeman 《Angewandte Chemie (International ed. in English)》1998,37(23):3220-3238
Knots, polyhedra, and Borromean rings with specific structural and topological features can be made from DNA. Biotechnologists have been exploiting the programmability of DNA intermolecular associations for a quarter of a century. These operations have now been applied successfully to branched DNA species to produce complex target structures (for example, the cube shown in the picture) and a nanomechanical device. The assembly of two-dimensional crystals with programmed topographic characteristics demonstrates the simplicity of translating design into surface structures. 相似文献
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Andrew C. Benniston Philip R. Mackie Anthony Harriman 《Angewandte Chemie (International ed. in English)》1998,37(3):354-356
Directional light-induced electron transfer takes place in the catenane shown schematically on the right. This catenane is similar to the photosynthetic reaction center: The two chemically identical electron acceptors (rectangles) bound to a ruthenium complex as donor have different reduction potentials because their environments are of different polarity. The electron transfer proceeds preferentially (85 %) to the external acceptor. 相似文献
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Alberto Credi Steven J. Langford Anna Prodi J. Fraser Stoddart Margherita Venturi 《Supramolecular chemistry》2013,25(2):303-311
Abstract The spectroscopic and electrochemical properties of two cyclophanes containing one and, respectively, two 2,7-diazapyrenium electron-acceptor units, and of their [2]catenanes with macrocycles containing two dioxybenzene or dioxynaphthalene electrondonor units have been investigated. The absorption spectra of the catenanes show weak and broad bands in the visible region, assigned to charge-transfer (CT) interactions. The very strong and structured fluorescence (298 K) and the structured fluorescence and phosphorescence (77 K) of the diazapyrenium unit are maintained in the two cyclophanes, but they are no longer present in the [2]catenanes, presumably because of a quenching process caused by the lower energy CT excited states. Each diazapyrenium unit undergoes two distinct reduction processes - only the first one of which is fully reversible - that are hardly affected at all when the diazapyrenium units are incorporated in a cyclophane. In the [2]catenanes, the CT interaction displaces the reduction processes of the diazapyrenium units toward more negative potentials. The results obtained for the diazapyrenium and previously investigated 4,4′-bipyridinium salts, selected cyclophane derivatives, and some [2]catenanes obtained by interlocking the cyclophanes with macrocycles containing two dioxyaromatic electron-donor units are compared and discussed. 相似文献
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Fabian M. Steudel Dr. Ernest Ubasart Luigi Leanza Míriam Pujals Dr. Teodor Parella Prof. Giovanni M. Pavan Prof. Xavi Ribas Prof. Max von Delius 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309393
The addition of two unsymmetric malonate esters to the Buckminster fullerene C60 can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out-trans-3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C60 with the shape-persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self-assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP). 相似文献
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We have demonstrated the self-assembly of linear oligo[2]catenanes via selective cross-catenation. A Pd(II)-linked double looped molecule 1 was transformed into the cyclic trimer c-(1)3 through the catenation. When 1 was treated with a kinetically inert Pt(II)-linked single looped molecule 2a in aqueous media (1:1.2 DMSO/H2O) at room temperature, linear oligo[2]catenanes of 2a-(1)n-2a (n=1 and 2) were selectively obtained, because the kinetically inert Pt(II)-linked ring 2a is allowed to thread on only kinetically labile Pd(II)-linked ring of 1. The distribution of the oligomers depends on the monomer ratio of 1 to 2a. When the ratio of 1 to 2a was 1:2, bis[2]catenane 3a (2a-1-2a) was quantitatively assembled. When the ratio of 1 to 2a was 1:1, not only 3a but also tris[2]catenane 4 (2a-1-1-2a) was assembled. The ratio of 3a to 4 was carefully determined to be 1:1 by NMR. The lengths of 3a and 4 in an extended conformation were estimated by MD/MM2 simulation to be 3.6 and 5.4 nm, respectively. 相似文献
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Gerhard Wenz 《Angewandte Chemie (International ed. in English)》1994,33(8):803-822
Cyclodextrins are frequently used as building blocks, because they can be linked both covalently and noncovalently with specificity. Thus one, two, three, seven, fourteen, eighteen, or twenty substituents have been linked to one β-cyclodextrin molecule in a regioselective manner. Furthermore, Cyclodextrins may serve as organic host molecules. Their internal cavity is able to accommodate one or two guest molecules. Conversely, suitable guest molecules can be used to thread one, two, or many (one hundred or more) cyclodextrin rings. The resulting supramolecular structures are often formed in solution, which allows characterization by high-resolution spectroscopic methods. Chemical conversion of these structures provides molecular architectures such as catenanes, rotaxanes, polyrotaxanes, and tubes, which are not readily prepared by other methods. The particular properties of Cyclodextrins can also be employed, for example, for the chromatographic separation of complex mixtures of substances, even racemates, by molecular recognition. Cyclodextrins and their derivatives have been found to be remarkably active catalysts as well. Finally, since Cyclodextrins can favorably influence the release of drugs, many new applications will certainly be developed in the near future. 相似文献