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1.
In this study we synthesized two acid‐/base‐controllable [2]rotaxanes featuring aminodiazobenzene and aminocoumarin units, respectively, as chromophores and dibenzo[24]crown‐8 and dibenzo[25]crown‐8 units, respectively, as their macrocyclic components. Each [2]rotaxane contained N‐alkylarylamine (ammonium) and N,N‐dialkylamine (ammonium) centers as binding sites for their crown ether components. The absorption patterns of the chromophores were dependent on the position of the encircling macrocyclic component and the degree of protonation, with three distinct states (under acidic, neutral, and basic conditions) evident for each [2]rotaxane. The mixed [2]rotaxane system displayed stepwise and independent molecular shuttling behavior based on the degree of protonation of the amino groups in response to both the amount and strength of added acids or bases; as such, the system provided five different absorption signals as outputs that could be read using UV/Vis spectroscopy.  相似文献   

2.
《中国化学》2017,35(7):1050-1056
Crown ether usually plays the role of macrocyclic host in supramolecular chemistry, but here the crown ether is also utilized as the stoppers in rotaxanes. In this work, we designed and synthesized two [3]rotaxanes containing four crown ether components by using an approach of template‐directed clipping reaction, of which, two crown ether components were employed as the macrocyclic hosts to assemble the mechanically interlocked framework while another two crown ether units located on the two ends of ammonium template acting as the stoppering groups of rotaxanes. Their self‐assembling process was monitored by the 1H NMR and one of the single crystal structures of [3]rotaxane was obtained.  相似文献   

3.
Efficient end‐capping synthesis of neutral donor–acceptor (D –A) [2]rotaxanes without loading any catalysts or activating agents was achieved by utilizing high reactivity of a pentacoordinated hydrosilane toward salicylic acid derivatives. As components of [2]rotaxanes, an electron‐deficient naphthalenediimide‐containing axle with a salicylic acid terminus and several electron‐rich bis(naphthocrown) ether macrocycles were employed. End‐capping reactions with the pentacoordinated hydrosilane underwent smoothly even at low temperature to afford the corresponding [2]rotaxanes in good yields. A [2]rotaxane containing bis‐1,5‐(dinaphtho)‐38‐crown‐10 ether as a wheel molecule was synthesized and isolated in 84 % yield by the end‐capping at ?10 °C, presenting the highest yield ever reported for the end‐capping synthesis of a neutral D –A [2]rotaxane. It was found that the yields of the [2]rotaxanes in the end‐capping reactions were almost parallel to the formation ratios of the corresponding pseudo[2]rotaxanes estimated by utilizing model systems. These results indicate that the end‐capping reaction using the pentacoordinated hydrosilane proceeded without perturbing the threading process, and most of the pseudo[2]rotaxanes underwent efficient end‐capping reaction even at low temperature.  相似文献   

4.
Two ferrocenylmethyl ammonium salts were used as axle components of pseudorotaxanes with dibenzo[24]crown‐8. The pseudorotaxane with an alkyne terminal group in the axle component underwent a Cu‐catalyzed Huisgen coupling reaction (click reaction) with an alkyl azide to afford cationic [2]rotaxanes with a triazole group in the axle molecule. The rotaxane reacted with Ac2O to produce neutral rotaxanes with an amide group in the axle component. Both cationic and neutral rotaxanes were treated with K[PtCl3(CH2?CH2)] to form the PtII‐containing rotaxanes.  相似文献   

5.
[reaction: see text] In this Letter, we present an easy method for the synthesis of rotaxanes using a novel DCC-[2]rotaxane. The DCC-[2]rotaxane is composed of dibenzo-24-crown-8 ether, an amino acid tether, and di-tert-butyl phenyl rings as blocking groups. It is relatively stable and can be purified by column chromatography. A series of model rotaxanes were obtained in good yields by condensing the DCC-[2]rotaxanes with N-(2-aminoethyl)-3,5-di-tert-butylbenzylamide in acetonitrile and chloroform.  相似文献   

6.
The structural complexity of mechanically interlocked molecules are very attractive to chemists owing to the challenges they present. In this article, novel mechanically interlocked molecules with a daisy‐chain‐containing hetero[4]rotaxane motif were efficiently synthesized. In addition, a novel integrative self‐sorting strategy is demonstrated, involving an ABB‐type (A for host, dibenzo‐24‐crown‐8 (DB24C8), and B for guest, ammonium salt sites) monomer and a macrocycle host, benzo‐21‐crown‐7 (B21C7), in which the assembled species in hydrogen‐bonding‐supported solvent only includes a novel daisy‐chain‐containing hetero[4]pseudorotaxane. The found self‐sorting process involves the integrative recognition between B21C7 macrocycles and carefully designed components simultaneously containing two types of secondary ammonium ions and a host molecule, DB24C8 crown ether. The self‐sorting strategy is integrative to undertake self‐recognition behavior to form one single species of pseudorotaxane compared with the previous report. This self‐sorting system can be used for the efficient one‐pot synthesis of a daisy‐chain‐containing hetero[4]rotaxane in a good yield. The structure of hetero[4]rotaxane was confirmed by 1H NMR spectroscopy and high‐resolution electrospray ionization (HR‐ESI) mass spectrometry.  相似文献   

7.
Fréchet‐type dendrons (G0–G3) were added as both axle stoppering units and cyclic wheel appendages in a series of [2]rotaxanes, [3]rotaxanes, and molecular shuttles that employ 1,2‐bis(pyridinium)ethane axles and 24‐membered crown ethers wheels. The addition of dendrimer wedges as stoppering units dramatically increased the solubility of simple [2]rotaxanes in nonpolar solvents. The X‐ray structure of a G1‐stoppered [2]rotaxane shows how the dendritic units affect the structure of the interlocked components. Increased solubility allows observation of how the interaction of dendritic units on separate components in interlocked molecules influences switching properties and molecular size. In a series of [2]rotaxane molecular shuttles incorporating two recognition sites, it was demonstrated that an increase in generation on either the stoppering unit or cyclic wheel could influence both the rate of shuttling and the site preference of the wheel on the axle.  相似文献   

8.
Two novel multilevel switchable [2]rotaxanes containing an ammonium and a triazole station have been constructed by a CuI‐catalyzed azide–alkyne cycloaddition reaction. The macrocycle of [2]rotaxane containing a C6‐chain bridge between the two hydrogen bonding stations exhibits high selectivity for the ammonium cation in the protonated form. Interestingly, the macrocycle is able to interact with the two recognition stations when the bridge between them is shortened. Upon deprotonation of both [2]rotaxanes, the macrocycle moves towards the triazole recognition site due to the hydrogen‐bond interaction between the triazole nitrogen atoms and the amide groups in the macrocycle. Upon addition of chloride anion, the conformation of [2]rotaxane is changed because of the cooperative recognition of the chloride anion by a favorable hydrogen‐bond donor from both the macrocycle isophthalamide and thread triazole CH proton.  相似文献   

9.
A pseudorotaxane consisting of a 24-membered crown ether and secondary ammonium salt with the hydroxy group at the terminus was quantitatively acylated by bulky acid anhydride in the presence of tributylphosphane as catalyst to afford the corresponding rotaxane in high yield. Large-scale synthesis without chromatographic separation was easily achieved. The ammonium group in the resulting rotaxane was quantitatively acylated with excess electrophile in the presence of excess trialkylamine. Various N-functionalized rotaxanes were prepared by this sequential double-acylation protocol. 1H NMR spectra and X-ray crystallographic analyses of the rotaxanes showed that the crown ether component was captured on the ammonium group in ammonium-type rotaxane by strong hydrogen-bonding intercomponent interaction. The conformation around the ammonium group was fixed by the hydrogen-bonding interaction. Meanwhile, the conformation of the amide-type rotaxane was determined by the weak CH/pi interaction between the methylene group in crown ether and the benzene ring of the axle component. The N-acylation of ammonium-type rotaxane is useful for the preparation of both functionalized rotaxanes and weak intercomponent interaction-based rotaxanes.  相似文献   

10.
Translational movement of the macrocycle in two structurally similar bistable [2]rotaxanes, which is induced by a four-step electrochemical process in solution, has been investigated by using a methodology developed in the preceding article (Chem. Eur. J. 2008, 14, 1107-1116). Both [2]rotaxanes contain a crown ether that can be accommodated by either of two interconnected viologen recognition sites. These sites are substantially different in terms of their affinity towards the crown ether and they possess considerably different electrochemical reduction potentials. The two [2]rotaxanes differ in the length and the rigidity of a bridge that links these sites. A combination of molecular mechanics modelling and NOE spectroscopy data provides information about the conformations of both [2]rotaxanes in the parent oxidation state when the crown ether exclusively populates the strong recognition site. To determine the population of the recognition sites at subsequent stages of reduction, a paramagnetic NMR technique and cyclic voltammetry were used. The key finding is that the flexibility of the connecting bridge element between the recognition sites interferes with shuttling of the crown ether in [2]rotaxanes. It can be demonstrated that the more flexible trimethylene bridge is folded, thus limiting the propensity of the crown ether to shuttle. Consequently, the crown ether populates the original site even in the second reduced state of the flexible [2]rotaxane. On the contrary, in the [2]rotaxane in which two viologen sites are connected by a larger and more rigid p-terphenylene bridge, the predominant location of the crown ether at the weak recognition site is achieved after just one single electron reduction.  相似文献   

11.
This paper reports a novel methodology for the conformational analysis of [2]rotaxanes. It combines NMR spectroscopic (COSY, NOESY and the recently reported paramagnetic line-broadening and suppression technique) and electrochemical techniques to enable a quantitative analysis of the co-conformations of interlocked molecules and the conformations of their components. This methodology was used to study a model [2]rotaxane in solution. This [2]rotaxane consists of an axle that incorporates an electron-poor, doubly positively charged viologen that threads an electron-rich crown ether. It has been shown that the axle of the [2]rotaxane in its dicationic state adopts a folded conformation in solution and the crown ether is localised at the viologen moiety. Following a one-electron reduction of viologen, the paramagnetic radical cation of the [2]rotaxane retains its folded conformation in solution. The data also demonstrate that in the radical cation the crown ether remains localised at the viologen, despite its reduced affinity for the singly reduced viologen. The combined quantitative NMR spectroscopic and electrochemical characterisation of the electromechanical function of the model [2]rotaxane in solution provides an important reference point for the study of switching in structurally related bistable [2]rotaxanes, which is the subject of the second part of this work.  相似文献   

12.
New dibenzo[24]crown‐8 ether derivatives were prepared that contain appendages with thioether donors that can coordinate to a metal ion. These macrocycles were then combined with 1,2‐bis(pyridinium) ethane axles to create two types of [2]rotaxane ligands; those with the four thioether donors on the crown ether and those with six donor groups, four from the crown ether and two more attached to the stoppering groups of the dumbbell. The crown ethers and both types of [2]rotaxane ligands were allowed to react with AgI ions to form metal‐organic rotaxane framework (MORF) style coordination polymers. The interlocked hexadentate ligand forms the first example of a new type of lattice containing interwoven frameworks resulting from both interpenetration of frameworks due to the presence of an interlocked ligand and more classical interpenetration of independent frameworks.  相似文献   

13.
A fifteen-year riddle has been settled: neutralization, the most popular chemical event, of a crown ether/sec-ammonium salt-type rotaxane has been achieved and a completely nonionic crown ether/sec-amine-type rotaxane isolated. A [2]rotaxane was prepared as a typical substrate from a mixture of dibenzo[24]crown-8 ether (DB24C8) and sec-ammonium hexafluorophosphate (PF(6)) with a terminal hydroxy group through end-capping with 3,5-dimethylbenzoic anhydride in the presence of tributylphosphane as a catalyst in 90% yield. A couple of approaches to the neutralization of the ammonium rotaxane were investigated to isolate the free sec-amine-type rotaxane by decreasing the degree of thermodynamic and kinetic stabilities. One approach was the counteranion-exchange method in which the soft counterion PF(6)(-) was replaced with the fluoride anion by mixing with tetrabutylammonium fluoride, thus decreasing the cationic character of the ammonium moiety. Subsequent simple washing with a base allowed us to isolate the free sec-amine-type rotaxane in a quantitative yield. The other approach was a synthesis based on a protection/deprotection protocol. The acylation of the sec-ammonium moiety with 2,2,2-trichloroethyl chloroformate gave an N-carbamated rotaxane that could be deprotected by treating with zinc in acetic acid to afford the corresponding free sec-amine-type rotaxane in a quantitative yield. The structure of the free sec-amine-type rotaxane was fully confirmed by spectral and analytical data. The generality of the counteranion-exchange method was also confirmed through the neutralization of a bisammonium-type [3]rotaxane. The mechanism was studied from the proposed potential-energy diagram of the rotaxanes with special emphasis on the role of the PF(6)(-) counterion.  相似文献   

14.
[3]- and [5]-rotaxanes consisting of crown ether and ammonium salts were synthesized in high yields by a tributylphosphine-catalyzed end-capping method which provides a simple and practical means of obtaining higher-order rotaxanes.  相似文献   

15.
α‐Cyclodextrin (CD)‐based size‐complementary [3]rotaxanes with alkylene axles were prepared in one‐pot by end‐capping reactions with aryl isocyanates in water. The selective formation of [3]rotaxane with a head‐to‐head regularity was indicated by the X‐ray structural analyses. Thermal degradation of the [3]rotaxanes bearing appropriate end groups proceeded by stepwise dissociation to yield not only the original components but also [2]rotaxanes. From the kinetic profiles of the deslippage, it turned out that the maximum yield of [2]rotaxane was estimated to be 94 %. Thermodynamic studies and NOESY analyses of such rotaxanes revealed that [2]rotaxanes are specially stabilized, and that the dissociation capability of the [3]rotaxanes to the components can be adjusted by controlling the structure of the end groups, direction of the CD groups, and length of the alkylene axle.  相似文献   

16.
A general synthesis of triazolium‐containing [2]rotaxanes, which could not be accessed by other methods, is reported. It is based on a sequential strategy starting from a well‐designed macrocycle transporter which contains a template for dibenzo‐24‐crown‐8 and a N‐hydroxysuccinimide (NHS) moiety. The sequence is: 1) synthesis by slippage of a [2]rotaxane building‐block; 2) its elongation at its NHS end; 3) the delivery of the macrocycle to the elongated part of the axle by an induced translational motion; 4) the contraction process to yield the targeted [2]rotaxane and recycle the initial transporter.  相似文献   

17.
Three new [2]rotaxanes with aromatic nitrogen donors appended to the crown ether wheel have been synthesized and used as ligands to coordinate Cd(II) ions. One of these yields a new type of 2-periodic, metal organic rotaxane framework in which the wheel rather than the axle is used to link the metal nodes.  相似文献   

18.
A triethylphosphonium group attached to a pyridinium ethane moiety can be used as an axle for the self-assembly of [2]pseudorotaxanes and [2]rotaxanes. Although [2]pseudorotaxane formation is limited due to the bulk of the PR4+ group, [2]rotaxanes can be formed utilising 24-crown-8 ether, benzo-24-crown-8 ether and naphtho-24-crown-8 ether. The synthesis of these [2]rotaxanes and the X-ray structure of the [2]rotaxane containing a 24-crown-8 ether wheel are described. When the crown ether contains an aromatic group two possible conformational isomers exist; these are identified at low temperature by 1H and 31P NMR spectroscopy.  相似文献   

19.
A [2]rotaxane was produced through the assembly of a picolinaldehyde, an amine, and a bipyridine macrocycle around a CuI template by imine bond formation in close‐to‐quantitative yield. An analogous [3]rotaxane is obtained in excellent yield by replacing the amine with a diamine, thus showing the suitability of the system for the construction of higher order interlocked structures. The rotaxanes are formed within a few minutes simply through mixing the components in solution at room temperature and they can be isolated through removal of the solvent or precipitation.  相似文献   

20.
Effective induction of preferred‐handed helicity of polyacetylenes by pendant mechanically chiral rotaxanes is discussed. Polyacetylenes possessing optically active mechanically chiral rotaxanes in the side chains were synthesized by the polymerization of the corresponding enantiopure [2]rotaxane‐type ethynyl monomers prepared by the chiral‐phase HPLC separations. The CD Cotton effects revealed that the polyacetylenes took preferred‐handed helical conformations depending on the rotaxane chirality. The preferred‐handed helix was not disturbed by an additional chiral substituent on the rotaxane side chain. These results demonstrate the significance and utility of mechanically chiral rotaxanes for the effective construction of asymmetric fields.  相似文献   

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