Search

Polymer nanocomposites face a fundamental challenge in simultaneously enhancing strength and toughness, as current methods often compromise one for the other. Here the authors incorporate mechanically interlocked [2]rotaxane units into the interfacial layer of dynamically cross-linked polymer nanocomposites to enhance both strength and toughness.

The synthesis of molecular knots remains challenging. Here, the authors report the synthesis of a chiral molecular trefoil metallaknot by self-assembly which contains only 54 atoms in the backbone.

Knots reduce the tensile strength of macroscopic threads and fibres. Now it has been shown that the presence of a well-defined overhand knot in a polymer chain can substantially increase the rate of scission of the polymer under tension, as deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds.

A rotaxane-based mechanochemical system enables force-controlled release of multiple cargo molecules that are appended to its molecular axle.

Since the discovery of mechanically planar chiral rotaxanes and topologically chiral catenanes, their asymmetric synthesis has been a long-standing challenge. Here, the authors report enantioselective preparation of mechanically planar chiral rotaxanes with up to 99.9% ee in 29% yield.

Doping carbon nanomaterials with heteroatoms is the most common way to change their catalytic activity. Here, the authors show that the catalytic properties of single-walled carbon nanotubes can be modified by non-covalently encapsulating them within electron-accepting or electron-donating macrocycles to form rotaxane-like structures.

Mechanically locked molecules provide interesting topological structures and can present challenging synthetic targets. Here the authors report the synthesis of mechanically self-locked molecules, including chiral endo-spirobicyclics containing multiply interlocked rings within a single molecule.

Spiro compounds contain two or more rings linked together through one common atom. Here the authors provide a method to backfold both rings, producing spiro quasi[1]catenanes, via a strategy of temporarily linking the linear intermediates with covalent bonds.

Crystalline phase transition can be used to detect changes in the solid state properties of materials. Here, the authors describe the mechanical response of a crystal composed of ferrocene-containing rotaxane to laser irradiation.

A molecular ratchet, in which a crown ether is pumped from solution onto an encoded molecular strand by a pulse of chemical fuel, opens the way for the reading of information along molecular tapes.

The topology of a polymer is normally a fixed property of the material, derived from the characteristic of the monomers and their linkages. Here the authors present a method to transform the topology of block copolymers containing rotaxane linkages via acetylation.

Despite mechanically axially chiral (MAC) catenanes being recognized in 1961, their stereoselective synthesis had not been disclosed until now. Closer inspection of the MAC stereogenic unit has also led to the identification of an analogous, but unremarked upon, form of rotaxane stereochemistry and the conceptualization of a general approach to prepare MAC molecules stereoselectively.

A molecular-scale pump whose operation is driven by a catalytic process when in the presence of chemical fuel is autonomous, within an operating window, as long as the fuel lasts.

Communication of chirality at a molecular level is the fundamental for transmitting chirality information but one-step communication modes in many artificial systems limits further processing the chirality information. Here, the authors report chirality communication of aromatic oligoamide sequences within interpenetrated helicate architecture in a hierarchical manner.

For interlocking ring structures, knot theory predicts that the number of topologically different links increases with ring and crossing number. Here, the authors use a peptide folding-and-assembly strategy to selectively realize two highly entangled catenanes with 4 rings and 12 crossings, representing two of the 100 predicted topologies with this complexity.

A molecular strand can be knotted and unknotted into three different topologies, depending on the complexing metal ion used (copper or lanthanide or none).

Molecules exhibiting Möbius topology are fascinating but challenging synthetic targets. Here, the authors report the elegant synthesis and crystal structure of a catenane formed from two fully conjugated, interlocked Möbius nanohoops, and use theoretical calculations to understand its conformational stability and aromaticity.

The complexity of rotaxane dendrimers poses a great synthetic challenge and the synthesis of higher generation rotaxane dendrimers has therefore rarely been reported. Here the authors report the synthesis of acid-base switchable rotaxane dendrimers up to generation 4 and demonstrate the uptake and release of guest molecules.

The synthesis of interlocked compounds such as catenanes and rotaxanes has undergone much development in recent years, but molecular knots are still relatively hard to make. It has now been shown that a linear bipyridine oligomer can fold around a single zinc-ion template to form a complex that can be cyclized to give a molecular trefoil knot.

The Star of David topology is an iconic symbol that has been used in religious and cultural contexts for thousands of years. Now it is assembled in molecular form through a hexameric circular helicate generated by six tris(bipyridine) ligands entwined about six iron(II) cations. The structure of the two triply-entwined 114-membered rings is revealed by X-ray crystallography.

Woven topologies endow macroscopic objects with mechanical stability, but their molecular counterparts have remained difficult to prepare. Now, an extended triaxial supramolecular weave has been formed by the self-assembly of a judiciously shaped organic building block — a rigid oligoproline segment featuring two perylene-monoimide moieties — through π–π stacking and CH–π interactions.

Mechanically interlocked supramolecular compounds have garnered widespread attention but it remains challenging to investigate topological adjustments in such complicated structures. Here, the authors use a bidentate pyridyl ligand featuring an extended π-conjugated plane for coordination-directed self-assembly to engineer three different kinds of sophisticated complexes.

An amino-acid-encoded assembly strategy is developed for the synthesis of programmable chiral Solomon links, featuring tunable cavity dimensions and shapes. This template-free synthetic approach favours homochiral assembly over non-chiral or heterochiral pathways. The resulting interlocked molecules exhibit strong chiral amplification and exceptional enantioselective peptide recognition.

The formation of catenanes through dynamic covalent reaction of self-assembling precursors in one pot offers a powerful route to complex interlocked architectures, yet the mechanistic insight remains underexplored. Here, the authors elucidate the nucleation–elongation mechanism in the one-pot synthesis of topologically distinct catenanes.

The structural anisotropy necessary for the powered directional rotation of chemically fuelled molecular motors had previously been provided by chiral fuels or enzymes. Now it has been shown that asymmetry in the organocatalyst itself is sufficient for directional fuelled rotation. This informs how chemical energy is transduced through catalysis, the fundamental process that powers biology.

Molecular information encoded within supramolecular frameworks offers a powerful paradigm for directing emergent function beyond the genetic code, but systematic investigations into alternative spatial configurations and their consequences remain scarce. Here the authors use metalla-[2]catenanes to probe sequence–function relationships in layered architectures.

Controlled motion in mechanically interlocked molecules, such as a macrocycle moving back and forth along the axle of a rotaxane, forms the basis of complex functions in molecular machinery. Now, ring-through-ring shuttling has been achieved using two macrocycles that switch position between two anchoring sites, which involves the smaller ring passing through the larger one.

Pseudorotaxane dethreading offers a means to regulate motion in artificial molecular machines but achieving predictable and programmable control over dethreading kinetics remains challenging. Here, the authors report systematic modulation of dethreading behaviour through component engineering of a pseudorotaxane platform.

A [2]catenane comprising two intertwined aromatic (34π) octaphyrinoid rings with entangled magnetic shielding interactions is synthesized. Upon four-electron oxidation, the system converts to a tetracation with two globally antiaromatic (32π) rings, in which through-space bonding interactions diminish the antiaromatic destabilization. Counterions can also affect the (anti)aromaticity of the tetracations.

The design and assembly of interlocked supramolecular cages is of interest due to their exquisite topological configuration and excellent performance in a variety of applications. Here, the authors synthesize interlocked cages from half-sandwich rhodium building blocks and prepare membranes for applications in photothermal seawater desalination.

Catenanes can exhibit chirality even when their component rings are achiral. Here an isostructural desymmetrization strategy is developed, demonstrating that two achiral rings, each featuring two mirror planes and a two-fold axis of symmetry, can form a catenane with tuneable mechanical chirality.

A purely organic crystalline two-dimensional mechanically interlocked polymer comprising [c2]daisy chain units forms via preorganized crystallization and thiol–ene click chemistry. This polymer network can be exfoliated to give nanosheets with a 47-fold stiffness enhancement relative to the bulk parent.

Water treatment membranes are prone to fouling, degrading performance. Here the authors integrate cyclodextrin supramolecular systems which harness the dynamic behavior of surface molecules to prevent foulant accumulation, thereby preserving membrane performance.

A system is described in which a small macrocycle is continuously transported directionally around a cyclic molecular track when powered by irreversible reactions of a chemical fuel; such autonomous chemically fuelled molecular motors should find application as engines in molecular nanotechnology.

Interlocked molecules offer a platform to control the relative motion between different molecular components with precision which is a cornerstone of synthetic nanotechnology. Here, the authors utilize a molecular dual pump to achieve the assembly of translational isomers with high efficiency and accuracy.

Synthesizing topologically complex interwoven molecules with high yield remains challenging due to structural preorganization demands. Here face-bridging ligands on metal–organic cage frameworks are shown to enable high-yield synthesis of knotted cages that mechanically trap guests inside, enhancing guest retention and structural robustness.

Catalytic cycles have been demonstrated in mechanically interlocked systems. Here, the authors report a [2]rotaxane containing a nitroxidic radical macrocycle and establish the efficiency of its catalytic redox cycle in this constrained environment.

A strategy is introduced for promoting the folding in metallopeptide nanostructures, resulting in high mechanical rigidity. The mechanical properties are reflected in enhanced peptide-binding properties and heightened antimicrobial activities relative to their unfolded counterparts.

The importance of charged species in numerous biological and environmental processes has stimulated the development of host molecules for their selective recognition. Now anisotropically polarized halogen- and chalcogen-bonding [2]rotaxanes are demonstrated to exhibit dual Lewis-acidic and Lewis-basic amphoteric properties for anion or cation recognition via the same donor atoms.

A new concept termed 'robust dynamics' is presented as the intellectual centerpiece to the union between metal–organic frameworks (MOFs) and mechanically interlocking molecules. Robust dynamics allows highly flexible entities, which are bound covalently to MOF backbones, to carry out repeated movements without affecting the integrity of the overall structure.

Due to their dynamic planar chirality, pillar[n]arenes are promising circularly polarized luminescence emitters but efficient solution state emission is a challenge due to the unit flipping and swing. Here, the authors report a mechanically locking approach for boosted dissymmetry factor values of pyrene-tiaraed pillar[5]arenes up to 0.015 through the formation of corresponding [2]rotaxanes.

Preassembled materials are ubiquitous in our everyday life due to their readiness and functionality; an end-user simply follows instructions to assemble them and harness function. Here, metastable rotaxanes are utilized to approach preassembled materials: a multicomponent, preprogrammed system can be conveniently (via heating) transformed into colorful polymer networks at the end-user’s will.

“Cycloparaphenylenes consisting of are cyclic π-conjugated structures presetting interesting physical properties upon functionalization. However, the ring strain and steric hindrance of the substituents hamper the functionalization of small sized cycloparaphenylenes. Here, the authors describe a [6]cycloparaphenylene with twelve methoxy units employed to form a rotaxane with in-plane aromaticity upon oxidation.”

By virtue of the rotational motions of interlocked macrocycles, the authors describe a chameleon-like catenane host that can adjust its co-conformation for selective binding to copper(I) or sulfate ion. While the cationic copper(I) complex is achiral, the interlocked rings in the catenane host rotate and re-orient into a chiral co-conformation upon forming the anionic sulfate complex.

Mechanically interlocked structures in polymer backbones can give interesting functionality, but can be challenging to prepare and control. Here, the authors report the development of polymers with a daisy chain unit in the backbone that are capable of shape memory behaviour.

The study of cross-catenated metallacages could provide facile insights into achieving more precise control over low-symmetry/high-complexity hierarchical assembly systems but is currently lacking. Here, the authors report a cross-catenane formed between two position-isomeric Pt(II) metallacages in the solid state.

Long polyynes have fascinating properties but they are difficult to synthesize as a consequence of their high reactivity. Now, it has been shown that cobalt carbonyl complexes can be used as masked alkyne equivalents, enabling the preparation of stable polyyne polyrotaxanes with up to 34 contiguous triple bonds.

Enriching the toolbox of polymers, the design and construction of novel polymers with desired properties and functions remains an attractive topic in polymer chemistry. Here the authors demonstrate rotaxane-branched dendronized polymers with rotaxane-branched dendrons attached onto the polymer chains as polymers with attractive dynamic properties.

Mechanically interlocked architectures inspired the fabrication of numerous molecular systems, but the topological design of such architectures has not been fully explored from the nano- to the macroscopic scale. Here, the authors propose a MOFaxane, comprised of long chain molecules penetrating a microcrystal of metal– organic framework.