Synthesis of pillar[7]arene

The first synthesis of pillar[7]arene is reported with two methods.Method A:the FeCl₃-catalyzed condensation reaction of 1,4- dimethoxybenzene（1） with paraformaldehyde in CHCl₃ gave dimethoxypillar[7]arene（3）.Method B:the p-toluenesulfonic acid catalyzed condensation reaction of 2,5-bis（benzyloxymethyl）-1,4-dimethoxybenzene（2） in CH₂Cl₂ gave compound 3.Demethylation of 3 with BBr₃ gave pillar[7]arene（4）.The pillar[7]arene might be a perspective macrocyclic host in host-guest chemistry.     

Piling Up Pillar[5]arenes To Self‐Assemble Nanotubes

New liquid‐crystalline pillar[5]arene derivatives have been prepared by grafting first‐generation Percec‐type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc‐shaped structure perfectly suited for self‐organization into a columnar liquid‐crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6‐dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Col_h mesophase has been deduced from X‐ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4‐dimethoxypillar[5]arene and 1,6‐dicyanohexane.     

Synthesis and X-ray crystal structure of a difunctionalized pillar[5]arene at A1/B2 positions by in situ cyclization and deprotection

The reaction of 1,4-dimethoxybenzene and paraformaldehyde using AlBr(3) yields multiple-deprotected pillar[5]arenes. A1/B2 di-deprotected pillar[5]arene can be isolated by silica gel chromatography and washing procedures. The X-ray structure and polymerization of the A1/B2 di-deprotected pillar[5]arene are reported.     

Construction of unique pseudo[1]rotaxanes and [1]rotaxanes based on mono-functionalized pillar[5]arene Schiff bases

Journal of Inclusion Phenomena and Macrocyclic Chemistry - A series of mono-functionalized pillar[5]arene Schiff bases were successfully synthesized by amidation reaction of pillar[5]arene...     

Water-soluble pillar[4]arene[1]quinone: Synthesis,host-guest property and application in the fluorescence turn-on sensing of ethylenediamine in aqueous solution,organic solvent and air

Water-soluble pillar[5]arenes are a class of typical macrocycles and have aroused tremendous attention for its easy to modify, abundant host-guest properties and extensive applications. However, up to now, all the reported water-soluble pillar[5]arenes acted as the host molecules, whereas they failed to be postsynthetically modified, which seriously impeded the development of the pillar[5]arene-based supramolecular chemistry. In this work, a new water-soluble pillar[5]arene, pillar[4]arene[1]quinone, was designed and synthsized with eight quaternary ammonium groups as well as a quinone units. Such a new water-soluble pillar[4]arene[1]quinone was capable of forming 1:1 stable complex with sodium 1-octanesulfonate in aqueous solution. Since the 1,4-quinone unit of WP[4]Q[1] could react with ethylenediamine (EDA) to form a conjugated quinoxaline structure, so pillar[4]arene[1]quinone could apply to the facile fluorescence turn-on sensing of EDA in aqueous solution, organic solvent and air.     

Monofunctionalized pillar[5]arenes: synthesis and supramolecular structure

The first synthesis of a monohydroxy pillar[5]arene has been carried out, by controlling the de-O-methylation of per-methylated pillar[5]arene. Using monohydroxy pillar[5]arene as an intermediate, mono-guest-functionalized pillar[5]arene was prepared. It formed a self-inclusion complex in CDCl(3) whereas in acetone-d(6) dethreading of the guest moiety took place.     

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.     

Selective complexation of n-alkanes with pillar[5]arene dimers in organic media

A pillar[5]arene dimer was synthesized by linking a mono-hydroxylated pillar[5]arene with 1,4-bis(bromomethyl)benzene. The pillar[5]arene dimer formed stronger complexes with n-alkanes than did a monomeric pillar[5]arene.     

Synthesis,crystal structures and complexing ability of difunctionalized copillar[5]arene Schiff bases

An efficient method for the synthesis of some difunctionalized copillar[5]arene Schiff bases from condensation of salicylaldehyde and its 5-chloro, 5-bromo, 3,5-di(t-butyl) substituted derivatives with corresponding diamino-functionalized copillar[5]arene, which were prepared by Gabriel reaction according to the reported method. Single-crystals of six copillar[5]arenes were determined by X-ray diffraction. An ORTEP of compounds showed that the two chains units of Schiff base exist in the outside of the cavity of pillar[5]arene. Furthermore, the complexing ability of these Schiff bases to transition metal ions were investigated by UV and fluorescence spectroscopy.     

para-Bridged symmetrical pillar[5]arenes: their Lewis acid catalyzed synthesis and host-guest property

Condensation of 1,4-dimethoxybenzene (DMB) with paraformaldehyde in the presence of BF3.O(C2H5)2 gave novel para-bridged pentacyclic pillar DMB (DMpillar[5]arene). Moreover, para-bridged pentacyclic hydroquinone (pillar[5]arene) was prepared. Pillar[5]arene formed 1:1 host-guest complexes with dialkyl viologen and alkyl pyridinium derivatives. However, pillar[5]arene did not form complexes with the diadamantyl viologen derivative since a bulky adamantyl group was unable to thread the cavity of pillar[5]arene.     

Separation of Linear and Branched Alkanes Using Host–Guest Complexation of Cyclic and Branched Alkane Vapors by Crystal State Pillar[6]arene

Activated crystals of pillar[6]arene produced by removing the solvent upon heating were able to take up branched and cyclic alkane vapors as a consequence of their gate‐opening behavior. The uptake of branched and cyclic alkane vapors by the activated crystals of pillar[6]arene induced a crystal transformation to form one‐dimensional channel structures. However, the activated crystals of pillar[6]arene hardly took up linear alkane vapors because the cavity size of pillar[6]arene is too large to form stable complexes with linear alkanes. This shape‐selective uptake behavior of pillar[6]arene was further utilized for improving the research octane number of an alkane mixture of isooctane and n‐heptane: interestingly, the research octane number was dramatically improved from a low research octane number (17 %) to a high research octane number (>99 %) using the activated crystals of pillar[6]arene.     

Host–Guest Complexation Using Pillar[5]arene Crystals: Crystal-Structure Dependent Uptake,Release, and Molecular Dynamics of an Alkane Guest

Host–guest complexation has been mainly investigated in solution, and it is unclear how guest molecules access the assembled structures of host and dynamics of guest molecules in the crystal state. In this study, we studied the uptake, release, and molecular dynamics of n-hexane vapor in the crystal state of pillar[5]arenes bearing different substituents. Pillar[5]arene bearing 10 ethyl groups yielded a crystal structure of herringbone-type 1:1 complexes with n-hexane, whereas pillar[5]arene with 10 allyl groups formed 1:1 complexes featuring a one-dimensional (1D) channel structure. For pillar[5]arene bearing 10 benzyl groups, one molecule of n-hexane was located in the cavity of pillar[5]arene, and another n-hexane molecule was located outside of the cavity between two pillar[5]arenes. The substituent-dependent differences in molecular arrangement influenced the uptake, release, and molecular dynamics of the n-hexane guest. The substituent effects were not observed in host–guest chemistry in solution, and these features are unique for the crystal state host–guest chemistry of pillar[5]arenes.     

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.     

Syntheses of a pillar[4]arene[1]quinone and a difunctionalized pillar[5]arene by partial oxidation

A pillar[4]arene[1]quinone and a difunctionalized pillar[5]arene have been synthesized by partial oxidation.     

Construction of π‐Surface‐Metalated Pillar[5]arenes which Bind Anions via Anion–π Interactions

By simple ligand exchange of the cationic transition‐metal complexes [(Cp*)M(acetone)₃](OTf)₂ (Cp*=pentamethylcyclopentadienyl and M=Ir or Rh) with pillar[5]arene, mono‐ and polynuclear pillar[5]arenes, a new class of metalated host molecules, is prepared. Single‐crystal X‐ray analysis shows that the charged transition‐metal cations are directly bound to the outer π‐surface of aromatic rings of pillar[5]arene. One of the triflate anions is deeply embedded within the cavity of the trinuclear pillar[5]arenes, which is different to the host–guest behavior of most pillar[5]arenes. DFT calculation of the electrostatic potential revealed that the metalated pillar[5]arenes featured an electron‐deficient cavity due to the presence of the electron‐withdrawing transition metals, thus allowing encapsulation of electron‐rich guests mainly driven by anion–π interactions.     

Synthesis and characterization of bis-[1]rotaxanes via salen-bridged bis-pillar[5]arenes

The series of salen-bridged bis-pillar[1]arenes were conveniently prepared by condensation reaction of5,5'-methylenebis(2-hydroxybenzalde hyde)or 5,5'-(propane-2,2-diyl)bis(2-hydroxybenzaldehyde)with mono-amido-functionalized pillar[5]arenes containing different terminal aminoalkyl groups in refluxing ethanol.The^1H NMR and 2D-NOESY spectra indicated that the salen-bridged bis-pillar[5]arenes with longer allcylene linker(n=3,4,6)formed the fascinating bis-[1]rotaxanes,while the salenbridged bis-pillar[5]arenes with short hydrazine and ethylenediamino linker(n=0,2)predominately existed in free form.The single crystal structure of the bis-pillar[5]are ne ambiguously indicated that two propylenediamino linker inserted in to two cavities of pillar[5]arene to form a novel bis-[1]rotaxanes.     

Host–Guest Complexation of Perethylated Pillar[5]arene with Alkanes in the Crystal State

Activated perethylated pillar[5]arene crystals show an unexpected alkane‐shape‐ and ‐length‐selective gate‐opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n‐alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate‐opening pressure. As the chain length of the n‐alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n‐hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane‐shape‐selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state.     

Comparison of pillar[5]arene and calix[4]arene anion receptor ability in aqueous media

Abstract

Recognition ability of both cationic pillar[5]arene and calix[4]arene has been studied in aqueous media. Anion complexation can be evaluated from their ability to complex their counterions as well as an added external organic anion. DOSY NMR experiments and fluorescence quenching show that pillararenes have a larger ability for including their own counterions than calixarenes irrespective of the anion (tetrafluoroborate or chloride or bromide) and the structure of the cationic moiety (trimethylammonium or methylimidazolium). Counterion complexation shows a picture where four to five positive charges of the pillar[5]arene are neutralised, meanwhile only one positive charge of the calixarene is neutralised for a 1 mM solution of the macrocycle. Irrespective of the smaller net positive charge in the pillar[5]arene, its binding ability for organic anions (toluenesulfonate or hydroxybenzoate) is larger than for calix[4]arene allowing a better accommodation of the guest in its cavity. The larger separation between the cationic groups of the receptor and its electron-rich aromatic region improves the anion recognition ability for pillar[5]arene.     

A Diaminopillar[5]arene-Based Macrobicyclic Molecule: Synthesis,Characterization and A Lock–Key Story

A new macrobicyclic molecule ( BC-DAP5 ), consisting of a diaminopillar[5]arene cavity and a fused ring, was successfully constructed using a Grubbs metathesis reaction. Further studies indicated that BC-DAP5 possessed a unique molecular behavior, showing a response to acid/base stimuli. In BC-DAP5 , protons (acid) acted as a lock, locking the fused ring out of the cavity (pillar[5]arene), and a base served as the key, making the fused ring switch in or out freely. Reversible control of the molecular behavior was achieved simply by adding acid and base alternately.     

Polycationic Pillar[5]arene Derivatives: Interaction with DNA and Biological Applications

Dendritic pillar[5]arene derivatives have been efficiently prepared by grafting dendrons with peripheral Boc‐protected amine subunits onto a preconstructed pillar[5]arene scaffold. Upon cleavage of the Boc‐protected groups, water‐soluble pillar[5]arene derivatives with 20 ( 13 ) and 40 ( 14 ) peripheral ammonium groups have been obtained. The capability of these compounds to form stable nanoparticles with plasmid DNA has been demonstrated by gel electrophoresis, transmission electron microscopy (TEM), and dynamic light scattering (DLS) investigations. Transfection efficiencies of the self‐assembled 13 /pCMV‐Luc and 14 /pCMV‐Luc polyplexes have been evaluated in vitro with HeLa cells. The transfection efficiencies found for both compounds are good, and pillar[5]arenes 13 and 14 show very low toxicity if any.