Design and synthesis of self-included pillar[5]arene-based bis-[1]rotaxanes

Two strategies for the design of new pillar[5]arene-based mechanically self-interlocked molecules (MSMs) are reported here. The first strategy is based on the construction of an intermediate pseudo[1]rotaxane followed by the desired bis-[1]rotaxane. The other one is based on the construction of the desired bis-[1]-rotaxane directly via a condensation reaction through host-guest interactions between a mono-functionalized pillar[5]arene and the axle. This compound has interesting self-assembly properties in methanol and some extended applications of this compound will be reported in the near future.     

Synthesis and characterization of a new pillar[5]arene-based [1]rotaxane

In this study, we reported the synthesis of three kinds of mono-functional pillar[5]arene derivatives PRI, PRII and R and their structures were studied by 1D and 2D NMR spectra and mass spectra. The 2D NMR spectra including ¹H-¹³C HSQC, ¹H-¹H COSY and NOESY spectra indicated that PRI and PRII are both stable self-included pseudo[1]rotaxanes in CDCl₃. These original structures are promising compounds for the design of pillar[5]-based [1]rotaxane. And the results showed that R could exist stable in CDCl₃ and DMSO because of the coordination of N-H?O hydrogen bonding interaction and C-H?π interaction.     

Axle length- and solvent-controlled construction of (pseudo)[1]rotaxanes from mono-thiourea-functionalised pillar[5]arene derivatives

A series of thiourea-functionalised pillar[5]arene derivatives 3ⁿm were constructed from a series of mono-amide-functionalised pillar[5]arenes 2ⁿ. The formation of their free forms or (pseudo)[1]rotaxane structures were controlled by their axle lengths or solvents, which were investigated by ¹H NMR spectroscopy. Some of (pseudo)[1]rotaxane structures were also supported by their single-crystal structures.     

Construction of [1]rotaxanes with pillar[5]arene as the wheel and terpyridine as the stopper

The condensation reaction ofω-aminoalkyleneamide-functionalized pillar[5]arenes with 2-(4-([2,2’:6’,2〃-terpyridin]-4’-yl)phenoxy)acetic acid or 4-(4-([2,2’:6’,2"-terpyridin]-4’-yl)phenoxy)butanoic acid in dry chloroform at room temperature under the catalysis of HOBT/EDCl resulted in novel pillar[5]arene diamido-bridged terpyridine derivatives.~1 H NMR and 2 D NOESY spectra clearly indicated that the interesting[1]rotaxanes were formed by longer alkylene such as propylene,butylene and hexylenediamido chains threading into the cavity of the pillar[5]arene and with larger terpyridine acting as the stopper.However,the shorter ethylenediamido chain only exists outer of cavity of pillar[5]arene and the molecule exist on free form.     

Construction and investigation of photo-switch property of azobenzene-bridged pillar[5]arene-based [3]rotaxanes

Series of azobenzene-bridged pillar[5]arene-based [3]rotaxanes with different alkyl chain length of guest molecules were constructed by threading-endcapping method with alkylenetriazole as axile and tetrahydrochromene as endcapping group.The encapsulation of pillar[5]arenes were proved by highresolution mass,¹ H NMR and NOESY spectra.The photo-responsive property were examined by irradiation of the synthesized [3]rotaxanes with 365 nm and blue light LED,which caused trans to cis and cis to trans isomerization,respectively.Irradiation of corresponding model guest compounds without pillar[5]arene encapsulation resulted in near completely trans to cis and cis to trans isomerization,indicating the existence of pillar[5]arenes is the determining factor for the comprised photo isomerization efficiency.     

Pillar[5]arene-based [3]rotaxanes: Convenient construction via multicomponent reaction and pH responsive self-assembly in water

Four pillar[5]arene based [3]rotaxanes(1-4) involving two 1,4-diethoxypillar[5]arene(DEP5) rings and a dumbbell-shaped component were successfully synthesized.The dumbbell-shape molecules contain one longer bridge,two triazole sites and two multicomponent stoppers.After threading DEP5 rings with linear guests(G1-G4) which contain two benzaldehyde units,the base catalyzed three-component reaction of dimedone,malononitrile and benzaldehyde was performed to construct the stoppers and connected the pseudorotaxanes with stoppers to generate 1-4.The structures of [3]rotaxanes and their self-assembly behaviors were characterized by ~1 H NMR,~(13)C NMR,NOESY,HR-ESI-MS,DLS and TEM technologies.We hope that pillar[5]arene based [3]rotaxanes may have potential applications in drug delivery systems and molecular devices.     

Helic[6]arene-Based Chiral Pseudo[1]rotaxanes and [1]Rotaxanes

Chiral pseudo[1]rotaxanes and [1]rotaxanes constructed from macrocyclic arenes still remain a big challenge mainly owing to the lack of such chiral macrocycles. In this work, a new system of chiral pseudo[1]rotaxanes formed by self-inclusion of helic[6]arene containing amide linked with the terminal tertiary amines was first discovered. Based on an atom-economic stopping strategy, a pair of chiral [1]rotaxanes were conveniently obtained in almost quantitative yields by blocking the pseudo[1]rotaxanes with monobenzyl bromide of tetraphenylethene. The structures of pseudo[1]rotaxanes and [1]rotaxanes were characterized by 2D NMR spectra in solution, combined with DFT calculations. The photophysical properties further revealed the efficient chirality transfer of helic[6]arene to the tetraphenylethene moiety, compared to their unthreaded chiral isomers. The discovery of the chiral pseudo[1]rotaxanes allows for a wide and available synthesis of chiral [1]rotaxanes, and also opening a new avenue to the design of chiral supramolecular materials.     

Stable pillar [5] arene-based pseudo [1] rotaxanes formed in polar solution

Mono-alkyl-functionalized pillar[5] arenes P1,P2,and P3 were synthesized by click reaction,which exhibited different self-assembly behavior in polar solvent DMSO.Stable pseudo [1] rotaxane was formed by the self-complexation from P1 or P2,whereas,concentration-dependent pseudorotaxane structures were generated by P3 which bearing more flexible side chain.Interestingly,the obtained pseudo[1] rotaxanes exhibited a dynamic fast assembly process upon adding NaBF₄,resulting in the formation of Na⁺-induced pseudorotaxanes.     

Hydrazides of glycine-containing decasubstituted pillar[5]arenes: Synthesis and encapsulation of Floxuridine

Hydrazides of glycine-containing decasubstituted pillar[5]arenes were synthesized and characterized. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that self-assembly into monodisperse spherical nanoparticles (28?nm) was typical in water for pillarene hydrazides containing glycylglycide fragments (1?×?10^?3?M). Binding of the antitumor drug Floxuridine in water by the substituents of the macrocycle was established by NMR spectroscopy. It was shown by DLS and TEM, that heating the macrocycle-Floxuridine system in a 1:1 ratio at 1?×?10^?4?M led to its self-organization into monodisperse spherical particles 132?nm in diameter.     

Monofunctionalized pillar[5]arene-based stable [1]pseudorotaxane

A new monofunctionalized pillar[5]arene bearing imidazolium moiety that formed stable [1]pseudorotaxane even at high concentration (100 mmol/L) was reported. [1]Rotaxane was obtained effi ciently through thiol-ene reaction from [1]pseudorotaxane which further confi rmed the formation of [1]pseudorotaxane.     

Self-assembly and proton conductance of organic nanotubes from pillar[5]arenes

Organic nanotubes have been assembled from pillar[5]arenes 1 and 2. Compound 1 gelates organic solvents through the formation of tubular fibers which are evidenced by TEM and XRD experiments, while 2 assembles into two different channels under the template effect of water wires. In addition, the water wires in the nanotubes of 2 can be under selective proton conductance. The results described herein represent a new strategy for building tubular structures.     

Synthesis of Cucurbit[5]uril-Spermine-[2]Rotaxanes

Cucurbit[5]uril and decamethylcucurbit[5]uril are cyclic pentamers built from glycoluril or dimethylglycoluril respectively. Two different experimental methods have been used for the synthesis of the different [2]rotaxanes. The formed rotaxanes are characterized using ¹H-NMR spectroscopy, mass spectrometry and elemental analysis. In contrast to cucurbit[5]uril no [2]rotaxane could be obtained with decamethylcucurbit[5]uril.     

Dual Electroactivity in a Covalent Organic Network with Mechanically Interlocked Pillar[5]arenes

The synthesis and characterization of a polyrotaxanated covalent organic network (CON) based on the association between the viologen and pillar[5]arene (P[5]OH) units are reported. The mechanical bond allows for the irreversible insertion of n-type redox centers (P[5]OH macrocycles) within a pristine structure based on p-type viologen redox centers. Both redox units are active on a narrow potential range and, in water, the presence of P[5]OH greatly increases the electroactivity of the material.     

Synthesis of [60]fullerene-functionalized rotaxanes

Synthesis of [60]fullerene (C₆₀)-functionalized rotaxanes via Diels-Alder reactions with C₆₀ is described. Diels-Alder reaction of C₆₀ and sulfolene moiety as masked diene attached on the wheels of rotaxanes results in high yields of C₆₀ incorporation. Rotaxanes are prepared by tin-catalyzed urethane-forming end-capping reaction with isocyanate of pseudorotaxane having the wheel carrying C₆₀ functionality as introduced by the Diels-Alder reaction. The Diels-Alder reaction was accomplished as end-capping reaction between C₆₀ and pseudorotaxane bearing sultine moiety as masked diene on the axle terminal. A variety of C₆₀-containing [2]rotaxanes was prepared in moderate to good yields by these Diels-Alder protocols.     

Fullerene encapsulation with calix[5]arenes

This paper presents the synthesis of the fullerene hosts based on the calix[5]arenes and their binding properties. Calix[5]arenes 1a, 2, 3a bind C₆₀ or C₇₀ in organic solvents. The solvent effect of the fullerene complexation was clearly observed; the association constant decreases in a solvent with high solubility for C₆₀. Covalently linked double-calix[5]arenes 4-6 were also investigated on their binding properties for fullerenes in organic solvents. Their binding abilities for both C₆₀ and C₇₀ are extremely high in toluene solution. Higher binding selectivity toward C₇₀ is observed by all the double-calix[5]arenes. The selectivity of 5a toward C₇₀/C₆₀ is highest in toluene with a value of 10. The structures of the supramolecular complexes of the calix[5]arene hosts and C₆₀ or C₇₀ were investigated by using ¹H and ¹³C NMR studies. The molecular mechanics calculation and X-ray structure reveal that the interior of the calix[5]arene is complementary to the exterior of C₆₀ molecule. In contrast, the host-guest complexes of C₇₀ with the simple calix[5]arenes take many conformational options due to its less symmetric shape. The molecular mechanics calculation and our chemical shift simulation nicely worked to estimate the reliable structures; the calix[5]arene cavity takes up C₇₀ molecule, and the C₇₀ molecule tilts significantly from the C5 axis of the calix[5]arene. In the case of the host-guest complex of C₇₀ with the double-calix[5]arene, the molecular dynamics simulation of the host-guest complex represented the realistic movement of the bound C₇₀ inside the cavity. The combination of the molecular dynamics simulation and the chemical shift simulation of the host-guest complex suggested that the C₇₀ molecule rapidly moves inside the cavity.     

Synthesis of （p-Formylphenyl）azo Calix[4]arenes

Five novel azo calix[4]arenes were reported. The p-aminobenzaldehyde was diazotized with sodium nitrite in aqueous hydrochloride solution. Mono-, bis-, tris- and tetrakis(p-formylphenyl)azo calix[4]arenes (including proximal and distal isomers) were obtained respectively by diazo-coupling in different molar ratio to calix[4]arene(1) under pH=7.5--8.5 at 0-5℃. All (p-formylphenyl)azo calix[4]arenes were characterized by ^1H NMR, ^13C NMR, IR, MS (ESIMS) spectroscopies and elemental analysis.     

基于柱[5]芳烃的超分子组装研究进展

介绍了柱[5]芳烃基于主客体性质和柱状立体结构的超分子组装,以及边缘取代基对柱[5]芳烃的溶解性、功能性和主客体性质的影响。     

Synthesis and binding studies of novel bisthiacalix[4]arenes with diimime linkages

A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions.     

A pillar[5]arene-based side-chain pseudorotaxanes and polypseudorotaxanes as novel fluorescent sensors for the selective detection of halogen ions

A pseudorotaxane and its polypseudorotaxanes formed between pillar[5]arene moieties and noctylpyrazinium cations as novel fluorescent sensors for the selective detection of halogen ions were reported.A collapse of these pillar[5]arene-based pseudorotaxanes and polypseudorotaxanes occurred upon the addition of Cl,Br,and I（tetrabutylammonium salts）,respectively,leading to their fluorescence recovery.The fluorescence enhancement of the pseudorotaxane and the polypseudorotaxanes increases in the order of I