Rotaxane Research Articles

Light-Driven Aqueous Dissipative Pseudorotaxanes with Tunable Fluorescence Enabling Deformable Nano-Assemblies

Developing an artificial dynamic nanoscale molecular machine that dissipatively self-assembles far from equilibrium is fundamentally important but is significantly challenging. Herein, we report dissipatively self-assembling light-activated convertible pseudorotaxanes (PRs) that show tunable fluorescence and enable deformable nano-assemblies. A pyridinium-conjugated sulfonato-merocyanine derivative (EPMEH) and cucurbit[8]uril (CB[8]) form the 2EPMEH ⊂ CB[8] [3]PR in a 2:1 stoichiometry, which phototransforms into a transient spiropyran containing 1:1 EPSP ⊂ CB[8] [2]PR when exposed to light. The transient [2]PR thermally relaxes (reversibly) to the [3]PR in the dark accompanied by periodic fluorescence changes that include near-infrared emission. Moreover, octahedral and spherical nanoparticles are formed through the dissipative self-assembly of the two PRs, and the Golgi apparatus is dynamically imaged using fluorescent dissipative nano-assemblies.

Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization

Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit[8]uril (CB[8])-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB[8]-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB[8]-MPyVB undergoes a regioselective solid-state [2 + 2] photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals. The fabrication of rotaxane-based crystalline materials with both photoresponsive microscopic and macroscopic dynamic behaviors in solid state can be promising photoactuator devices, and will have implications in emerging fields such as optomechanical microdevices and smart microrobotics.

Cover Feature: Pentafluorophenyl Esters as Exchangeable Stoppers for the Construction of Photoactive [2]Rotaxanes (Chem. Eur. J. 33/2021)

Cover Feature: Pentafluorophenyl Esters as Exchangeable Stoppers for the Construction of Photoactive [2]Rotaxanes (Chem. Eur. J. 33/2021)

Party of Rotaxanes

Party of Rotaxanes

Macromolecular [2]Rotaxanes Linked with Polystyrene: Properties and Nanoscale Film Morphologies

In this study, poly(δ-valerolactone) (PVL) axles bearing movable and ionically fixed rotaxane wheels linked with polystyrene (rot-PS-M and rot-PS-F) have been investigated for the first time in the...

Chemical reactivity driving switchable molecular machines. A case of Bipyridine -Calixarene rotaxane

The driving interlocked mechanisms by the chemical reactivity profiles of molecular machine’s stages is undertaken, for the calixare-based rotaxane complexes containing tris(N-phenylureido)-calix[6]arene as wheel and a 4,4’-bipyridinium dication’s units as axle; The results clearly indicate the huge chemical reactivity dynamic potential (especially of electronegativity which is ultimately assimilated with the negative of the chemical potential of a system) able to drive either the slipper as well as the deslipper interlocked mechanisms of molecular machines, here for the bipyridine-calixarene rotaxane case, yet with appearing as a structural best (to date) structural explanation of the “activated mobile” character of the molecular machines by simple its inner self-activated potential.

Design and Construction of Pillar[5]arene-Based Bis-[1]rotaxane

Design and Construction of Pillar[5]arene-Based Bis-[1]rotaxane

(Invited) Rotaxanes and SWNTs Tie the Knot

Here, we present a strategy for the synthesis of rotaxane-type derivatives of carbon nanotubes, the first example of mechanically interlocked derivatives of SWNTs (MINTs).1 In the key rotaxane-forming step, we employed macrocycle precursors equipped with two recognition units and terminated with bisalkenes that were closed around the nanotubes through ring-closing metathesis (RCM). The mechanically interlocked nature of the derivatives is probed by analytical, spectroscopic, and microscopic techniques, as well as by appropriate control experiments. Remarkably, bulk reaction data confirm the interlocked nature of MINTs. We will also show that the effect of the mechanical bond on the properties of SWNTs is unique, and clearly different from the noninterlocked, supramolecular compounds.3

Rotamer‐Induced Dynamic Nature of a [2]Rotaxane and Control of the Dynamics by External Stimuli

A CuI‐catalyzed azide–alkyne cycloaddition reaction between an azide‐terminated NiII‐templated [2]pseudorotaxane with an oxy‐ether tris(amino) macrocycle (MC) and an alkyne‐terminated triphenylene stopper unit produces a new [2]rotaxane (ROT) with multiple functional groups. A detailed mass spectrometry study and various 1D and 2D NMR spectroscopy studies confirm the interpenetration of the axle in the macrocycle of ROT. The tri‐acetylation of the tris(amine) moiety of ROT produces AcROT with three tertiary amide functionalities. Prior to this selection, a detailed study of the dynamic properties was undertaken with the tertiary amide functionalized macrocycle MC1 and the tri‐methylated derivative of MC, MC2. A 1H NMR study of AcROT at room temp. reveals multiple signals for most of the protons owing to the existence of multiple conformers and co‐conformers in solution through tertiary amide bond rotations. Furthermore, the ethereal pocket of the heteroditopic macrocycle was explored to demonstrate the reversible locking and unlocking of the dynamic behaviour of AcROT through the addition and removal, respectively, of alkali‐metal ions.

ChemInform Abstract: Development of Pseudorotaxanes and Rotaxanes: From Synthesis to Stimuli‐Responsive Motions to Applications

AbstractReview: 681 refs.

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

Abstract We reported a new monofunctionalized pillar[5]arene bearing imidazolium moiety that formed stable [1] pseudo rotaxane even at high concentration (100 mmol/L) in chloroform. The self-assembly was detailed investigated by multiple methods, including varying concentration 1 H NMR, 2D COSY NMR, 2D NOESY NMR, viscosity measurements, 2D DOSY NMR, and HR-ESI-MS analysis. [1]Rotaxane was obtained efficiently through photo thiol-ene reaction which further confirmed the formation of [1] pseudo rotaxane.

Development of Pseudorotaxanes and Rotaxanes: From Synthesis to Stimuli-Responsive Motions to Applications.

Development of Pseudorotaxanes and Rotaxanes: From Synthesis to Stimuli-Responsive Motions to Applications.

ChemInform Abstract: Synthesis and Molecular Shuttling of [2]Rotaxanes under Mild Conditions.

[2]Rotaxanes constructed with an ethereal end-capped axle and a dibenzo-24-crown-8 wheel were synthesized from pseudorotaxanes bearing an alcoholic terminus and diaryldiazomethanes using diphenyl p...

A twin-axial[5]pseudorotaxane based on cucurbit[8]uril and α-cyclodextrin

Abstract A twin-axial hetero[5] pseudo rotaxane was constructed based on 1-hexyl-4,4′-bipyridinium guest 1 and cucurbit[8]uril (CB[8]) and α -cyclodextrin ( α -CD). In its structure, CB[8] included two bipyridinium units to realize the twin-axial mode, and the hexyl chain was threaded into the cavity of α -CD. The [5] pseudo rotaxane contains two types of macrocyclic hosts while the single axial and twin axial modes co-exist in its structure. The transformation of [5] pseudo rotaxane could be realized by the addition of acid and 2,6-dihydroxynaphthalene (HN).

Complexation of sym-bis(benzimidazole)-2,2′-ethylene salts with cucurbit[6]uril derivatives: A potential axle molecule for pseudorotaxanes

Abstract Sym -bis(benzimidazole)-2,2′-ethylene cations act as a new axle template for threading cucurbit[6]uril derivatives on, forming [2] pseudo rotaxane and [3] pseudo rotaxane. These new complexes have been studied using 1 H NMR, UV–vis absorption spectroscopy and X-ray analysis. Changes in the 1 H NMR spectra indicate that the two types of pseudo rotaxane can be formed by varying the host concentration. UV–vis absorption titration experiments at different pH values demonstrate that interesting p K a shifts of the bis-benzimidazole derivatives can be induced by the host–guest complexation. The associated constants were calculated to be 2.81 × 10 4 L/mol and 9.06 × 10 6 L/mol for the [2] pseudo rotaxanes and [3] pseudo rotaxanes, respectively. Furthermore, X-ray diffraction studies of the solid state structures provide unequivocal proof of the host concentration dependent pseudo rotaxane, which is strongly in line with the evidences in solution.

A Convenient Strategy to Control the Specific Surface Area of the Mesoporous Silica by Using the Poly(pseudo)rotaxanes Template

The poly(pseudo)rotaxanes formed by β-CD and F127 was used as the template to prepare the mesoporous silica. The specific surface area, pore size distribution and pore volume of the mesoporous silica could be controlled by simply changing the poly(pseudo)rotaxanes forming time. A series of samples with different template forming time were prepared to investigate the various specific surface area and pore size of the mesoporous silica. The morphology, composition, specific surface area and pore size of the mesoporous silica particle were investigated by the scanning electron microscopy, Fourier transformation infrared spectroscope, and N2 adsorption–desorption measurement.

ChemInform Abstract: Linear Aromatic Amide Foldamer‐Derived Supramolecular Architectures and Materials

AbstractReview: 73 refs.

Quantitative Emergence of Hetero[4]rotaxanes by Template‐Directed Click Chemistry

Quantitative Emergence of Hetero[4]rotaxanes by Template‐Directed Click Chemistry

Self-Entangling in a [1]Rotaxane

Self-Entangling in a [1]Rotaxane

Templated Threading to [3]Rotaxanes

Templated Threading to [3]Rotaxanes