Force-Triggered Guest Release from Mechanophore Incorporated Rotaxanes

We have developed a rotaxane-based mechanophore system that is capable of breaking a mechanical bond and releasing small molecules via force-triggered rotaxane disassembly.In this design,a cyclobutane mechanophore was fused to the ring component of a rotaxane,constructed through a template-mediated synthesis in high yields.Upon opening the ring component,the rotaxane disassembled to release the axle molecule.We successfully demonstrated and quantified the force-triggered release of the axlemolecule in both solution and solid-state samples.

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

Mono-alkyl-functionalized pillar[5]arenes PI, 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.

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.

Unveiling the Hidden Movements in the Shuttling of Rotaxanes

Movements in molecular machines are usually diverse and coupled,but some of them are often implicit and hard to be observed in experiments.In the present work,the two-or three-dimensional free-energy landscapes characterizing the coupled shutthng and other movements of a series of pH-triggered rotaxanes composed of a crown ether and an H-shaped axle with distinct number of phenyl rings(n=1-3)have been explored.The results show that although the calculated free-energy barriers against shutthng in the rotaxanes(n=2 and 3)change slightly,the move-ments coupled with the shutthng vary significantly with the axle length.At high pH,the shutthng in the rotaxane of n=2 is coupled with the isomerization of the wheel,while the shutthng in the one of n=3 is accompanied by both the isomerization and the rotation of the macrocycle.In addition,the crown ether imdenvent greater conlomiational change during shutthng at low pH compared to that at high pH.These results indicate that disentangling the coupled movements is important to reveal the underlying molecular mechanism of the shutthng.

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,13C 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.

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.

Temperature-driven braking of γ-cyclodextrin-curcubit[6]urilcowheeled [4]rotaxanes

Several cyclodextrin-cucurbit[6]uril-cowheeled [4]rotaxanes were synthesized through the cucurbit[6]uril-templated azide-alkyne 1,3-dipolar cycloaddition. The intramolecular interaction between the aromatic axle and the capping groups of cyclodextrin moieties was investigated by UV-vis, fluorescence,circular dichroism and NMR spectroscopic studies. The rotational kinetic of the wheel around the axle can be manipulated by adjusting the temperature. The capping group apparently slowed down the rotation of the wheel, playing a role of the brake, and lowering the temperature can stop the rotation of the wheel on the NMR timescale.

Self-assembly of Novel Hetero[3]rotaxane,[2]Rotaxanes and [2]Catenane

One linear template 13 and one cyclophane template 15, both incorporating two electron rich 1,4-dialkoxybenzene units and one diamide unit, have been synthesized. By utilizing donor-acceptor interaction and/or intermolecular hydrogen bonding assembling principles, one novel hetero[3]rotaxane 22·4Cl, possessing one neutral and one tetracationic ring components, has been synthesized from 13, through neutral [2]rotaxane 21 as intermediate. With 15 as template, tetracationic [2]catenane 23·4PF6 was assembled by using donor-acceptor interaction, but no neutral [2]rotaxane could be obtained under the typical conditions of hydrogen bonding assembling principle. The interlocked supramolecular compounds have been characterized and their spectral properties are investigated.

Construction of Crown Ether-Stoppering [3]Rotaxanes Based on N-Hetero Crown Ether Host

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.

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-[l]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. The newly synthesized bis-[1]rotaxane BR was characterized by ~1H NMR, ^(13)C NMR, 2D NMRs (~1H-^(13)C HSQC,~1H-~1H COSY and NOESY) and LC-ESI-MS,which indicated compound BR displayed an self-interlocked structure in CDCl_3. Surprisingly, the results of SEM, TEM and DLS showed that the compound BR could assemble into spherical nanoparticles in MeOH.

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.

基于Rotaxane单分子层的双稳态器件研究

利用微电子工艺制备了基于Rotaxane单分子层的双稳态分子电子器件,并对其电学特性进行了表征。研究发现,在Ti/Rotaxane/Au双稳态,器件具有可逆可重复的开关存储特性。将器件从初始的高阻态转变为低阻态的正向开关阈值电压为1.3 V,将低阻态转变为高阻态的负向开关阈值电压仅为-1.7 V。这种基于Rotaxane交叉结构的有机双稳态器件可望应用于非易失性分子存储器。

Rotaxane络合物研究新进展

Ｒｏｔａｘａｎｅ是在带有长链的分子上套入环状化合物的特殊络合物。本文综述了ｒｏｔａｘａｎｅ络合物，特别是环状化合物为环糊精（ｃｙｃｌｏｄｅｘｔｒｉｎ，ＣＤ）的ｒｏｔａｘａｎｅ－ＣＤ络合物的组成、合成，一些性质和应用以及研究方法，并提出了应子重视的研究方面。

A Molecular Modeling for the Complexation of Cyclobis(paraquat-p-phenylene) with Substituted Benzenes and Biphenyls

Molecular orbital PM3 calculation was performed on the complexation of cyclobis(paraquat-p-phenylene) with a number of 1,4-disubstituted benzenes and biphenyl derivatives. A fair correlation was found between the PM3 calculated binding energies and the experimental ones, which enabled the PM3 calculation to predict thc experimental binding energies for a number of important complexes. A good structure-activity relationship was also found between the PM3 calculated binding energies and the substituent molar refraction R-m and Hammett constants. indicating that the van der Waals force and the electronic interactions constituted the major driving forces for the complexation of cyclobis(paraquat-p-phenylene).

[5]Rotaxane, linear polymer and supramolecular organic framework constructed by nor-seco-cucurbit[10]uril-based ternary complexation

Here we use nor-seco-cucurbit[10]uril(ns-CB[10]) based ternary complexation to construct [5]rotaxane,linear supramolecular dynamic rotaxane polymers and cubic 3D supramolecular organic framework.A [5]rotaxane is constructed by ns-CB[10], TMe CB[6] and short linear derivatives of 4,4'-bipyridinium(M2). ns-CB[10], CB[7] and long linear derivatives of 4,4'-bipyridinium(M3) self-assemble into a linear supramolecular dynamic rotaxane polymer. ns-CB[10] and tetracationic tetrahedral monomer selfassemble and form a three-dimensional supramolecular organic framework. The above results demonstrate that ns-CB[10]-based ternary complexation is a versatile platform to build various supramolecular systems.

Molecular rotaxane shuttle-relay accelerates K^(+)/Cl^(-) symport across a lipid membrane

Synthetic molecules that can mediate the coupled transport of Cl^(-) with K^(+) and/or Na+across the lipid bilayers have aroused great interest due to their potential as a novel therapeutic strategy by disrupting cellular ion homeostasis.Based on the structural advantages of molecular rotaxanes,we herein show that two rotaxane-based transporters[2]R and[3]R induce coupled K^(+)/Cl^(-) channel transport by introducing Cl^(-) recognition sites in the thread and K^(+) binding group in the wheel,respectively.The welldesigned molecular structures allow the insertion of unimolecular rotaxanes into the lipid bilayer,thus achieving effective ion transport by means of thermodynamically controlled movement and driven by the difference in ion concentration inside and outside the vesicles.In addition,the use of a three-component rotaxane can accelerate ion transport through a cooperative shuttlerelay mechanism in which two wheels move along the thread in the lipid membrane,thereby enabling[3]R to have higher ion transport capacity.This work represents a major advance in the use of rotaxane molecules to accomplish more complex and effective tasks.

基于Rotaxane类分子的稳定、重复、可反复擦写的纳米信息存储

Rotaxane类分子在溶液中可以发生可逆的分子构型改变,并随之引起分子电导特性的转变,在纳米电子器件和分子存储器件中具有潜在的应用前景.但是还不能确定这类分子在固体薄膜中是否具有类似于在溶液中的结构与电导转变,需要对Rotaxane类分子固态薄膜进行深入的结构和特性研究.文章作者在一类Rotaxane分子H1和H2的固态薄膜上获得了纳米尺度的电导转变和稳定、重复的、近于单分子尺度的纳米级存储;同时,成功地在H2分子薄膜上实现了信息记录点的可反复擦写.另外,在单个分子和亚分子的水平上直接观察到了Rotaxane分子在外电场诱导下分子结构的可逆变化以及随之发生的相应电导特性的可逆转变,证实了Rotaxane分子在固态薄膜中的可逆结构和电导转变.

单次可编程金属-分子-金属器件(英文)

提出了一种单次可编程的金属-分子-金属器件.该器件利用一种经过改良的Rotaxane LB膜作为功能层,可以和应用于场编程门阵列电路中的无机反熔丝器件相比拟,将在有机可编程电路和容错电路等方面有较广泛的应用.所有的加工工艺都是低温工艺,使得该器件可以和其他有机器件集成.电学测试表明该器件有良好的单次编程能力,其击穿电压为2.2V,关态电阻为15kΩ,而开态电阻为54Ω.据分析,这一特性是由非对称的电极结构和金属原子在高电场作用下穿透了分子薄膜所造成的.

Topology: a unique dimension in protein engineering

Controlling protein topology has been a long standing challenge to go beyond their linear configuration defined by the translation mechanism of cellular machinery. In this mini-review, we focus on the topological diversity in proteins and review the major categories of protein topologies known to date, including branched/star proteins, circular proteins, lasso proteins, knotted proteins,and protein catenanes. The discovery of these topologically complex natural proteins and their synthetic pathways, the rational design and recombinant synthesis of artificial topological proteins and their biophysical studies, are summarized and discussed with regard to their general features and broad implications. The complexity of protein topology is recognized and the routes to diverse protein topologies are illustrated. We believe that topology engineering is an important way to modify protein properties without alternating their native sequences and shall bring in valuable dynamic features central to the creation of artificial protein machinery.

Synthesis of a bistable[3]rotaxane and its pH-controlled intramolecular charge-transfer behavior

A [3]rotaxane I involving two naphtho-21-crown-7 （N21 C7） rings and a dumbbell-shaped component 4 was synthesized. The dumbbell-shape molecule 4 contains one viologen nucleus, two secondary alkyl ammonium sites and two phenyl stoppers. After threading the N21C7 ring with the thread-like ammonium guest 3, the copper（l）-catalyzed Huisgen alkyne-azide 1,3-dipolar cycloaddition （CuAAC ＂click＂ reaction）, was performed to connect the pseudorotaxanes with viologen unit 2 and generate 1. Through treating the [3]rotaxane by the base and acid circularly, the two N21 C7 rings can make shuttling motion along the axle. Meanwhile the distance between the electron-deficient viologen unit and the electron-rich naphthol group can be adjusted precisely along with a remarkable intramolecular charge- transfer （CT） behavior.