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To explore the chirality induction and switching of topological chirality, poly[2]catenanes composed of helical poly(phenylacetylenes) (PPAs) main chain and topologically chiral [2]catenane pendants are described for the first time. These poly[2]catenanes with optically active [2]catenanes on side chains were synthesized by polymerization of enantiomerically pure topologically chiral [2]catenanes with ethynyl polymerization site and/or point chiral moiety. The chirality information of [2]catenane pendants was successfully transferred to the main chain of polyene backbones, leading to preferred‐handed helical conformations, while the introduction of point chiral units has negligible effect on the overall helices. More interestingly, attributed to unique dynamic feature of the [2]catenane pendants, these polymers revealed dynamic response behaviors to solvents, temperature, and sodium ions, resulting in the fully reversible switching on/off of the chirality induction. This work provides not only new design strategy for novel chiroptical switches with topologically chiral molecules but also novel platforms for the development of smart chiral materials. [ABSTRACT FROM AUTHOR]

Expanding the diversity of multi‐macrocyclic nanocarbons, particularly those with all‐benzene scaffolds, represents intriguing yet challenging synthetic tasks. Complementary to the existing synthetic approaches, here we report an efficient and modular post‐functionalization strategy that employs iridium‐catalyzed C−H borylation of the highly strained meta‐cycloparaphenylenes (mCPPs) and an mCPP‐derived catenane. Based on the functionalized macrocyclic synthons, a number of novel all‐benzene topological structures including linear and cyclic chains, polycatenane, and pretzelane have been successfully prepared and characterized, thereby showcasing the synthetic utility and potential of the post‐functionalization strategy. [ABSTRACT FROM AUTHOR]

Although catenated cages have been widely constructed due to their unique and elegant topological structures, cyclic catenanes formed by the connection of multiple catenane units have been rarely reported. Herein, based on the orthogonal metal‐coordination‐driven self‐assembly, we prepare a series of heterometallic [2]catenanes and cyclic bis[2]catenanes, whose structures are clearly evidenced by single‐crystal X‐ray analysis. Owing to the multiple positively charged nature, as well as the potential synergistic effect of the Cu(I) and Pt(II) metal ions, the cyclic bis[2]catenanes display broad‐spectrum antibacterial activity. This work not only provides an efficient strategy for the construction of heterometallic [2]catenanes and cyclic bis[2]catenanes but also explores their applications as superior antibacterial agents, which will promote the construction of advanced supramolecular structures for biomedical applications. [ABSTRACT FROM AUTHOR]

Triply interlocked [2]catenane complexes featuring two identical, mechanically interlocked units are extraordinarily rare chemical compounds, whose properties and applications remain open to detailed studies. Herein, we introduce the rational design of a new ligand precursor, L1, suitable for the synthesis of six triply interlocked [2]catenanes by coordination‐driven self‐assembly. The interlocked compounds can be reversibly converted into the corresponding simple triangular prism metallacage by addition of H2O or DMF solvents to their CH3OH solutions, thereby demonstrating the importance of π⋅⋅⋅π stacking and hydrogen bonding interactions in the formation of triply interlocked [2]catenanes. Moreover, extensive studies have been conducted to assess the remarkable photothermal conversion performance. Complex 6 a, exhibiting outstanding photothermal conversion performance (conversion efficiency in solution : 31.82 %), is used to prepare novel photoresponsive elastomer in combination with thermally activated liquid crystal elastomer. The resultant material displays robust response to near‐infrared (NIR) laser and the capability of completely reforming the shape and reversible actuation, paving the way for the application of half‐sandwich organometallic units in photo‐responsive smart materials. [ABSTRACT FROM AUTHOR]

Among mechanically interlocked supramolecular systems with cyclodextrins (CDs), successful examples of CD‐based catenanes are limited compared to a number of CD rotaxanes owing to the synthetic difficulties. We herein demonstrate an efficient synthesis of a CD‐based catenane using a meso‐arylporphyrin (Por) platform. Using Por modified with two olefin‐terminated oxyethylene chains at the cis‐meso‐positions, an interlocked Por‐CD catenane was synthesized via olefin metathesis in the presence of per‐O‐methylated β‐CD (TMe‐β‐CD) in water. The novel Por‐CD catenane was obtained in 30 % isolated yield, which was characterized by MALDI‐TOF mass and NMR spectroscopies. In the latter part, we demonstrate determination of the binding constants between TMe‐β‐CD and meso‐(4‐sulfonatophenyl)porphyrin using Por‐CD catenane, 2,6‐di‐O‐methyl‐β‐CD (DMe‐β‐CD), and 13C‐labeled TMe‐β‐CD (13C‐TMe‐β‐CD). The host‐guest exchange reaction from the Por‐CD catenane/DMe‐β‐CD to the Por‐CD catenane/TMe‐β‐CD complexes was directly monitored through 1D HMQC spectroscopy. The ratio of these complexes revealed the difference in the binding affinities of DMe‐β‐CD and TMe‐β‐CD to Por. The stable 1 : 2 inclusion complex between meso‐tetrakis(4‐sulfonatophenyl)porphyrin (TPPS) and TMe‐β‐CD has been well‐studied for many years. This study is the first to determine the respective binding constants, K1 and K2, using the model system, to be 3.0×107 M−1 and 3.4×107 M−1, respectively. [ABSTRACT FROM AUTHOR]

Catenanes, a distinctive category of mechanically interlocked molecules composed of intertwined macrocycles, have undergone significant advancements since their initial stages characterized by inefficient statistical synthesis methods. Through the aid of molecular recognition processes and principles of self-assembly, a diverse array of catenanes with intricate structures can now be readily accessed utilizing template-directed synthetic protocols. The rapid evolution and emergence of this field have catalyzed the design and construction of artificial molecular switches and machines, leading to the development of increasingly integrated functional systems and materials. This review endeavors to explore the pivotal advancements in catenane synthesis from its inception, offering a comprehensive discussion of the synthetic methodologies employed in recent years. By elucidating the progress made in synthetic approaches to catenanes, our aim is to provide a clearer understanding of the future challenges in further advancing catenane chemistry from a synthetic perspective. [ABSTRACT FROM AUTHOR]

Over the last two decades ratchet mechanisms have transformed the understanding and design of stochastic molecular systems—biological, chemical and physical—in a move away from the mechanical macroscopic analogies that dominated thinking regarding molecular dynamics in the 1990s and early 2000s (e.g. pistons, springs, etc), to the more scale‐relevant concepts that underpin out‐of‐equilibrium research in the molecular sciences today. Ratcheting has established molecular nanotechnology as a research frontier for energy transduction and metabolism, and has enabled the reverse engineering of biomolecular machinery, delivering insights into how molecules 'walk' and track‐based synthesisers operate, how the acceleration of chemical reactions enables energy to be transduced by catalysts (both motor proteins and synthetic catalysts), and how dynamic systems can be driven away from equilibrium through catalysis. The recognition of molecular ratchet mechanisms in biology, and their invention in synthetic systems, is proving significant in areas as diverse as supramolecular chemistry, systems chemistry, dynamic covalent chemistry, DNA nanotechnology, polymer and materials science, molecular biology, heterogeneous catalysis, endergonic synthesis, the origin of life, and many other branches of chemical science. Put simply, ratchet mechanisms give chemistry direction. Kinetic asymmetry, the key feature of ratcheting, is the dynamic counterpart of structural asymmetry (i.e. chirality). Given the ubiquity of ratchet mechanisms in endergonic chemical processes in biology, and their significance for behaviour and function from systems to synthesis, it is surely just as fundamentally important. This Review charts the recognition, invention and development of molecular ratchets, focussing particularly on the role for which they were originally envisaged in chemistry, as design elements for molecular machinery. Different kinetically asymmetric systems are compared, and the consequences of their dynamic behaviour discussed. These archetypal examples demonstrate how chemical systems can be driven inexorably away from equilibrium, rather than relax towards it. [ABSTRACT FROM AUTHOR]

Brønsted basicity is a fundamental chemical property featured by several kinds of inorganic and organic compounds. In this Review, we treat a particularly high basicity resulting from the mechanical entanglement involving two or more molecular subunits in catenanes and rotaxanes. Such entanglement allows a number of basic sites to be in close proximity with each other, highly increasing the proton affinity in comparison with the corresponding, non-entangled counterparts up to obtain superbases, properly defined as mechanically interlocked superbases. In the following pages, the development of this kind of superbases will be described with a historical perusal, starting from the initial, serendipitous findings up to the most recent reports where the strong basic property of entangled molecular units is the object of a rational design. Brønsted basicity can be greatly enhanced by the mechanical entanglement of two or more interlocked molecular subunits within catenanes and rotaxanes. Here, the authors discuss the development of such mechanically interlocked superbases, and outline challenges and opportunities for future directions of research. [ABSTRACT FROM AUTHOR]

Mechanically interlocked molecules (MIMs) represent an exciting yet underexplored area of research in the context of carbon nanoscience. Recently, work from our group and others has shown that small carbon nanotube fragments—[n]cycloparaphenylenes ([n]CPPs) and related nanohoop macrocycles—may be integrated into mechanically interlocked architectures by leveraging supramolecular interactions, covalent tethers, or metal‐ion templates. Still, available synthetic methods are typically difficult and low yielding, and general methods that allow for the creation of a wide variety of these structures are limited. Here we report an efficient route to interlocked nanohoop structures via the active template Cu‐catalyzed azide‐alkyne cycloaddition (AT−CuAAC) reaction. With the appropriate choice of substituents, a macrocyclic precursor to 2,2′‐bipyridyl embedded [9]CPP (bipy[9]CPP) participates in the AT−CuAAC reaction to provide [2]rotaxanes in near‐quantitative yield, which can then be converted into the fully π‐conjugated catenane structures. Through this approach, two nanohoop[2]catenanes are synthesized which consist of a bipy[9]CPP catenated with either Tz[10]CPP or Tz[12]CPP (where Tz denotes a 1,2,3‐triazole moiety replacing one phenylene ring in the [n]CPP backbone). [ABSTRACT FROM AUTHOR]

Although the synthesis of mechanically interlocked molecules has been extensively researched, selectively constructing homogeneous linear [4]catenanes remains a formidable challenge. Here, we selectively constructed a homogeneous linear metalla[4]catenane in a one‐step process through the coordination‐driven self‐assembly of a bidentate benzothiadiazole derivative ligand and a binuclear half‐sandwich rhodium precursor. The formation of metalla[4]catenanes was facilitated by cooperative interactions between strong sandwich‐type π‐π stacking and non‐classical hydrogen bonds between the components. Moreover, by modulating the aromatic substituents on the binuclear precursor, two homogeneous metalla[2]catenanes were obtained. The molecular structures of these metallacatenanes were unambiguously characterized by single‐crystal X‐ray diffraction analysis. Additionally, reversible structural transformation between metal‐catenanes and the corresponding metallarectangles could be achieved by altering their concentration, as confirmed by mass spectrometry and NMR spectroscopy studies. [ABSTRACT FROM AUTHOR]

The study of cross-catenated metallacages, which are complex self-assembly systems arising from multiple supramolecular interactions and hierarchical assembly processes, is currently lacking but could provide facile insights into achieving more precise control over low-symmetry/high-complexity hierarchical assembly systems. Here, we report a cross-catenane formed between two position-isomeric Pt(II) metallacages in the solid state. These two metallacages formed [2]catenanes in solution, whereas a 1:1 mixture selectively formed a cross-catenane in crystals. Varied temperature nuclear magnetic resonance experiments and time-of-flight mass spectra are employed to characterize the cross-catenation in solutions, and the dynamic library of [2]catenanes are shown. Additionally, we searched for the global-minimum structures of three [2]catenanes and re-optimized the low-lying structures using density functional theory calculations. Our results suggest that the binding energy of cross-catenanes is significantly larger than that of self-catenanes within the dynamic library, and the selectivity in crystallization of cross-catenanes is thermodynamic. This study presents a cross-catenated assembly from different metallacages, which may provide a facile insight for the development of low-symmetry/high-complexity self-assemble systems. 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. [ABSTRACT FROM AUTHOR]

It is necessary to conduct more in-depth research based on the metal-mediated interlocking catenanes reported by 2016 Nobel Prize winners in Chemistry. The synthetic approach of catenanes, consisting of two or more interlocked macrocycles, relies on the use of transition metals as templating species. We imagine that the catenanes directed by transition metals in complex system may be similar to the form of Maxwell's electromagnetic waves. To prove this conjecture, we designed a method to synthesize wavy interlocked macrocycles mediated by Pt/Ni ions. Through using high-temperature and -pressure methods, we quickly fixed the wavy interlocked macrocycles as templates, which were gradually covered by the Pt–Ni nanoparticles (NPs) in the synthesis process. The morphology of Pt–Ni NPs is observed by transmission electron microscopy (TEM). The results reveal that Pt–Ni NPs with a nanoparticle size about 9.54 ± 1.51 nm are covered along the wavy interlocked macrocycles templates. This work for assembling common small molecules into wavy structure opens up promising avenues for wavy NPs synthesis. [ABSTRACT FROM AUTHOR]

The use of 2,5‐diformylpyrrole in self‐assembly reactions with diamines and Zn(II)/Cd(II) salts allowed the preparation of [2]catenane, trefoil knot, and Borromean rings. The intrinsically dynamic nature of the diiminopyrrole motif rendered all of the formed assemblies intramolecularly flexible. The presence of diiminopyrrole revealed new coordination motifs and influenced the host–guest chemistry of the systems, as illustrated by hexafluorophosphate encapsulation by Borromean rings. [ABSTRACT FROM AUTHOR]

Over the last few decades, research on mechanically interlocked molecules has significantly evolved owing to their unique structural features and interesting properties. A substantial percentage of the reported works have focused on the synthetic strategies, leading to the preparation of functional MIMs for their applications in the chemical, materials, and biomedical sciences. Importantly, various macrocyclic wheels with specific heteroditopicity (including phenanthroline, amide, amine, oxy-ether, isophthalamide, calixarene and triazole) and threading axles (bipyridine, phenanthroline, pyridinium, triazolium, etc.) have been designed to synthesize targeted multifunctional mononuclear/multinuclear pseudorotaxanes, rotaxanes and catenanes. The structural uniqueness of these interlocked systems is advantageous owing to the presence of mechanical bonds with specific three-dimensional cavities. Furthermore, their multi-functionalities and preorganised structural entities exhibit a high potential for versatile applications, like switching, shuttling, dynamic properties, recognition and sensing. In this feature article, we describe some of the most recent advances in the construction and chemical behaviour of a new generation of interlocked molecules, primarily focusing on heteroditopic wheels and their applications in different directions of the modern research area. Furthermore, we outline the future prospects and significant perspectives of the new generation heteroditopic wheel based interlocked molecules in different emerging areas of science. [ABSTRACT FROM AUTHOR]

A series of [2]catenanes has been prepared from di‐NHC building blocks by utilizing solvophobic effects and/or π⋅⋅⋅π stacking interactions. The dinickel naphthobiscarbene complex syn‐[1] and the kinked biphenyl‐bridged bipyridyl ligand L2 yield the [2]catenane [2‐IL](OTf)4 by self‐assembly. Solvophobic effects are pivotal for the formation of the interlocked species. Substitution of the biphenyl‐linker in L2 for a pyromellitic diimide group gave ligand L3, which yielded in combination with syn‐[1] the [2]catenane [3‐IL](OTf)4. This assembly exhibits enhanced stability in diluted solution, aided by additional π⋅⋅⋅π stacking interactions. The π⋅⋅⋅π stacking was augmented by the introduction of a pyrene bridge between two NHC donors in ligand L4. Di‐NHC precursor H2‐L4(PF6)2 reacts with Ag2O to give the [Ag2L42]2 [2]catenane [4‐IL](PF6)4, which shows strong π⋅⋅⋅π stacking interactions between the pyrene groups. This assembly was readily converted into the [Au2L42]2 gold species [5‐IL](PF6)4, which exhibits exceptional stability based on the strong π⋅⋅⋅π stacking interactions and the enhanced stability of the Au‐CNHC bonds. [ABSTRACT FROM AUTHOR]

The first examples of [2]catenanes capable of selective anion transport across a lipid bilayer are reported. The neutral halogen bonding (XB) [2]catenanes were prepared via a chloride template‐directed strategy in an unprecedented demonstration of using XB⋅⋅⋅anion interactions to direct catenane assembly from all‐neutral components. Anion binding experiments in aqueous‐organic solvent media revealed strong halide over oxoanion selectivity, and a marked enhancement in the chloride and bromide affinities of the catenanes relative to their constituent macrocycles. The catenanes additionally displayed an anti‐Hofmeister binding preference for bromide over the larger iodide anion, illustrating the efficacy of employing sigma‐hole interactions in conjunction with the mechanical bond effect to tune receptor selectivity. Transmembrane anion transport studies conducted in POPC LUVs revealed that the catenanes were more effective anion transporters than the constituent macrocycles, with high chloride over hydroxide selectivity, which is critical to potential therapeutic applications of anionophores. Remarkably these outperform existing acyclic halogen bonding anionophores with regards to this selectivity. Record chloride over nitrate anion transport selectivity was also observed. This represents a rare example of the direct translation of intrinsic anion binding affinities to anion transport behaviour, and demonstrates the key role of the catenane mechanical bond effect for enhanced anion transport selectivity. [ABSTRACT FROM AUTHOR]

Poly[n]catenanes have exceptional mechanical bonding properties that give them tremendous potential for use in the development of molecular machines and soft materials. Synthesizing these compounds has, however, proven to be a formidable challenge. Herein, we describe a concise method for the construction of twisted polycatenanes. Our approach involves using preorganized double helicates as templates, linked crosswise in a linear fashion by either silver ions or triple bonds. By using this approach, we successfully synthesized twisted polycatenanes with both coordination and covalent bonding employing Ag(I) ions and ethynylene units, respectively, as the linkages and leveraging the same Ag(I)‐templated double helicate in both cases. Synthesis with Ag(I) ions formed a single‐crystalline one‐dimensional (1D) coordination poly[n]catenane, and synthesis using ethynylene units generated 1D fibers which self‐assembled with solvents to form a gel. Our results confirm the potential of multi‐stranded metallohelicates for creating sophisticated mechanically interlocked molecules and polymers, which could pave the way for exploration in the realms of molecular nanotopology and materials design. [ABSTRACT FROM AUTHOR]

Chemical topology refers to the three-dimensional arrangement (i.e., connectivity and spatial relationship) of a molecule's constituent atoms and bonds. The molecular mechanism for translation defines the linear configuration of all nascent proteins. Nontrivial protein topology arises only upon post-translational processing events and often imparts functional benefits such as enhanced stability, making topology a unique dimension for protein engineering. Utilizing the assembly-reaction synergy, our group has developed several methods for the effective and convenient cellular synthesis of a variety of topological proteins, such as lasso proteins, protein rotaxanes, and protein catenanes. The work opens the access to new protein classes and paves the road toward illustrating the topological effects on structure-function relationship of proteins, which lays solid foundation for exploring topological proteins' practical application. [ABSTRACT FROM AUTHOR]

The ever‐increasing demand for data storage and neuromorphic computing calls for innovative, high‐density solutions, such as resistive random‐access memory (RRAM). However, the integration of resistive switching and rectification at the nanoscale remains a formidable challenge. In this study, we introduce a bistable [2]catenane‐based supramolecular junction that simultaneously functions as a resistive switch and a diode. All supramolecular junctions are highly stable and reproducible over thousands of resistive switching cycles, because the nano‐confinement of two mechanically interlocked rings can stabilize the radical states of pyridinium moieties under ambient conditions. The successful realization of supramolecular junctions in functionality with a thickness of approximately 2 nm presents a promising avenue for the development of molecule‐scale based RRAM for a better solution to high density and energy efficiency. [ABSTRACT FROM AUTHOR]

The addition of two unsymmetric malonate esters to the Buckminster fullerene C60 can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out‐trans‐3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C60 with the shape‐persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self‐assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP). [ABSTRACT FROM AUTHOR]

The chemistry of mechanically interlocked molecules (MIMs) such as catenane and rotaxane is full of new opportunities for the presence of a mechanical bond, and the efficient synthesis of these molecules is therefore of fundamental importance in realizing their unique properties and functions. While many different types of preorganizing interactions and covalent bond formation strategies have been exploited in MIMs synthesis, the use of cucurbit[6]uril (CB[6]) in simultaneously templating macrocycle interlocking and catalyzing the covalent formation of the interlocked components is particularly advantageous in accessing high‐order catenanes and rotaxanes. In this review, catenane and rotaxane obtained from CB[6]‐catalyzed azide‐alkyne cycloaddition will be discussed, with special emphasis on the synthetic strategies employed for obtaining complex [n]rotaxanes and [n]catenanes, as well as their properties and functions. [ABSTRACT FROM AUTHOR]

Natural proteins exhibit rich structural diversity based on the folds of an invariably linear chain. Macromolecular catenanes that cooperatively fold into a single domain do not belong to the current protein universe, and their design and synthesis open new territories in chemistry. Here, we report the design, synthesis, and properties of a single-domain green fluorescent protein catenane via rewiring the connectivity of GFP's secondary motifs. The synthesis could be achieved in two steps via a pseudorotaxane intermediate or directly via expression in cellulo. Various proteins-of-interest may be inserted at the loop regions to give fusion protein catenanes where the two subunits exhibit enhanced thermal resilience, thermal stability, and mechanical stability due to strong conformational coupling. The strategy can be applied to other proteins with similar fold, giving rise to a family of single-domain fluorescent proteins. The results imply that there may be multiple protein topological variants with desirable functional traits beyond their corresponding linear protein counterparts, which are now made accessible and fully open for exploration. Natural proteins exhibit rich structural diversity based on the folds of an invariably linear chain. Here the authors design a single-domain GFP catenane as the counterpart of conventional linear GFP with enhanced thermal resilience and to provide a robust scaffold for making fusion protein catenanes. [ABSTRACT FROM AUTHOR]

Mechanically interlocked architecture has inspired the fabrication of numerous molecular systems, such as rotaxanes, catenanes, molecular knots, and their polymeric analogues. However, to date, the studies in this field have only focused on the molecular-scale integrity and topology of its unique penetrating structure. Thus, the topological material design of such architectures has not been fully explored from the nano- to the macroscopic scale. Here, we propose a supramolecular interlocked system, MOFaxane, comprised of long chain molecules penetrating a microcrystal of metal–organic framework (MOF). In this study, we describe the synthesis of polypseudoMOFaxane that is one of the MOFaxane family. This has a polythreaded structure in which multiple polymer chains thread a single MOF microcrystal, forming a topological network in the bulk state. The topological crosslinking architecture is obtained by simply mixing polymers and MOFs, and displays characteristics distinct from those of conventional polyrotaxane materials, including suppression of unthreading reactions. 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. [ABSTRACT FROM AUTHOR]

A series of Cp*Rh‐based discrete architectures was constructed by selecting four ether bipyridyl ligands and three half‐sandwich rhodium(III) bimetallic construction units, respectively. This study demonstrates a strategy for making the transition from a binuclear D‐shaped ring to a tetranuclear [2]catenane by adjusting the length of bipyridyl ligands. In addition, changing the position on the naphthyl group of the bipyridyl ligand from 2,6‐ to 1,5‐position substitution can realize the selective synthesis of [2]catenane and Borromean rings under similar conditions. The above‐mentioned constructions have been determined via X‐ray crystallographic analysis, detailed NMR techniques, electrospray ionization‐time‐of‐flight/mass spectrometry analysis, and elemental analysis. [ABSTRACT FROM AUTHOR]

Catenanes with multistate switchable properties are promising components for next‐generation molecular machines and supramolecular materials. Herein, we report a ligand‐controlled switching method, a novel method for the multistate switching of catenanes controlled by complexation with added amine ligands. To verify this method, a [3]catenane comprising cyclic porphyrin dimers with a rigid π‐system has been synthesized. Owing to the rigidity, the relative positions among the cyclic components of the [3]catenane can be precisely controlled by complexation with various amine ligands. Moreover, ligand‐controlled multistate switching affects the optical properties of the [3]catenanes: the emission intensity can be tuned by modulating the sizes and coordination numbers of integrated amine ligands. This work shows the utility of using organic ligands for the structural switching of catenanes, and will contribute to the further development of multistate switchable mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

We report herein a series of organometallic Borromean rings (BRs) and [2]catenanes prepared from benzobiscarbene ligands. The reaction of dinickel complexes of the benzobiscarbenes 1 a–1 c with a thiazolothiazole bridged bipyridyl ligand L2 led by self‐assembly to a series of organometallic BRs. Solvophobic effects played a crucial role in the formation and stability of the interlocked species. The stability of BRs is related to the N‐alkyl substituents at the precursors 1 a–1 c, where longer alkyl substitutes improve stability and inter‐ring interactions. Solvophobic effects are also important for the stability of [2]catenanes prepared from 1 a–1 c and a flexible bipyridyl ligand L3. In solution, an equilibrium between the [2]catenanes and their macrocyclic building blocks was observed. High proportions of [2]catenanes were obtained in concentrated solutions or polar solvents. The proportion of [2]catenanes in solution could be further enhanced by lengthening of the N‐alkyl substitutes. [ABSTRACT FROM AUTHOR]

This article discusses the author's pet peeves regarding stereochemical terminology in chemistry. The author emphasizes the importance of using correct terminology and clarifies the definitions of terms such as stereoisomers, chiral objects, enantiomers, and diastereomers. The author also explains the historical reasons behind the misconception that tetrahedral atoms with four different groups attached are necessary for enantiomers and diastereomers. The article concludes by discussing the relevance of these concepts in supramolecular chemistry, specifically in the context of catenanes. [Extracted from the article]

A review of heteroditopic interlocked molecules and their application as receptors for simple inorganic ion pair species. The review details the design and ion recognition properties of the rotaxane and catenane receptors, as well as highlighting some of the experimental challenges; hence, it provides insight into possible future avenues of research in this youthful field. [ABSTRACT FROM AUTHOR]

Cucurbit[n]uril supramolecular chemistry has developed rapidly since 2001 when different cucurbit[n]uril homologues (Q[n]) were successfully separated in pure form. The combination of Q[n] cavity size and various types of external stimuli has given birth to numerous types of Q[n]-based mechanically interlocked molecules (MIMs), including (pseudo)rotaxanes, catenanes, dendrimers and poly(pseudo)rotaxanes. In this review article, the important advances in the field of Q[n]-based MIMs over the past two decades are highlighted. This review also describes examples of heterowheel (pseudo)rotaxanes and poly(pseudo)rotaxanes involving Q[n]s, and reflects on the opportunities and challenges of constructing Q[n]-based stimuli-responsive MIMs. [ABSTRACT FROM AUTHOR]

In this work, a series of homoleptic monocyclic and [2]catenanes gold(I) thiolates were studied by DFT and TD-DFT methods to analyze the relationship between structure and property. The results reveal that the increase of Au–S–Au bond angles in Au11 and Au12 makes the [2]catenanes more planar than the monocyclic molecules. The smaller Au⋯Au contacts tighten the overall structure and enhance its geometrical stability. There is a positive correlation between the Au percentage in the frontier molecular orbitals and the orbital energy levels for both monocyclic molecules and [2]catenanes. The HOMO levels of the [2]catenanes are higher than those of the monocyclic molecules, which may be caused by stronger Au⋯Au Pauli repulsion. Differences in size and metallophilic interactions are responsible for the different absorption spectra of the complexes, and the electronic spectral redshift of the [2]catenanes is consistent with their higher HOMO energy levels. The results of energy decomposition analysis indicate that electrostatic interaction and orbital interaction are the main driving forces of molecular formation. In [2]catenanes, Pauli repulsion and steric interaction can be balanced. The calculated results of interaction energy and stabilization energy suggest that [2]catenanes are very stable. The calculated reaction enthalpies indicate that the chemical stabilization of [2]catenanes decreased in the order of Au12, Au11, and Au10. [ABSTRACT FROM AUTHOR]

Rotaxanes and molecular knots exhibit particular properties resulting from the presence of a mechanical bond within their structure that maintains the molecular components interlocked in a permanent manner. On the other hand, the disassembly of the interlocked architecture through the breakdown of the mechanical bond can activate properties which are masked in the parent compound. Herein, we present the development of stimuli‐responsive CuI‐complexed [2]catenanes as OFF/ON catalysts for the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction. The encapsulation of the CuI ion inside the [2]catenanes inhibits its ability to catalyze the formation of triazoles. In contrast, the controlled opening of the two macrocycles induces the breaking of the mechanical bond, thereby restoring the catalytic activity of the CuI ion for the CuAAC reaction. Such OFF/ON catalysts can be involved in signal amplification processes with various potential applications. [ABSTRACT FROM AUTHOR]

The present review introduces the electrochemical properties of macrocyclic compounds in the light of their use as supramolecular electrochemically controlled systems with reversible switchable binding of ions, molecules and redox-triggered reversible molecular motion of components with respect to each other. In particular, the electrochemical properties of calix[n]arenes, macrocyclic biindolizines, pseudorotaxanes, rotaxanes and catenanes are comprehensively considered. Besides that, the present article provides the readers with the brightest examples of reversible redox-switchable molecular motions, redox-switchable shuttles on the basis of mechanically interlocked molecules such as catenanes and rotaxanes. Donor and acceptor structural blocks of considered macrocyclic systems are described separately with the aim to familiarize the readers with this information first before introduction to the redox-switchable systems on their basis. Finally, the paper contains references to the most important and comprehensive literature on the subject of redox-switchable molecular systems. This approach will be especially useful for young researches wishing to study and work in the field of design of electrochemically driven devices based on supramolecular complexes. [ABSTRACT FROM AUTHOR]

The first examples of halogen bonding (XB) heteroditopic homo[2]catenanes were prepared by discrete Na+ template‐directed assembly of oligo(ethylene glycol) units derived from XB donor‐containing macrocycles and acyclic bis‐azide precursors, followed by a CuI‐mediated azide‐alkyne cycloaddition macrocyclisation reaction. Extensive 1H NMR spectroscopic studies show the [2]catenane hosts exhibit positive cooperative ion‐pair recognition behaviour, wherein XB‐mediated halide recognition is enhanced by alkali metal cation pre‐complexation. Notably, subtle changes in the catenanes' oligo(ethylene glycol) chain length dramatically alters their ion‐binding affinity, stoichiometry, complexation mode, and conformational dynamics. Solution‐phase and single‐crystal X‐ray diffraction studies provide evidence for competing host‐separated and direct‐contact ion‐pair binding modes. We further demonstrate the [2]catenanes are capable of extracting solid alkali‐metal halide salts into organic media. [ABSTRACT FROM AUTHOR]

In this minireview we present the use of the axially chiral 1,1'-binaphthyl-2,2'-diol (BINOL) unit as a stereogenic element in mechanically interlocked molecules (MIMs). We describe the synthesis and properties of such BINOL-based chiral MIMs, together with their use in further diastereoselective modifications, their application in asymmetric catalysis, and their use in stereoselective chemosensing. Given the growing importance of mechanically interlocked molecules and the key advantages of the privileged chiral BINOL backbone, we believe that this research area will continue to grow and deliver many useful applications in the future.

The initial evaluation of MOF entanglements as their main limitation is changing to an opportunity since the related benefits are now known. Based on a linear rigid dicarboxylic acid, biphenyl-4,4′-dicarboxylic acid (H2bpdc), and a flexible dipyridyl piperazine ligand, 1,4-bis(4-pyridylmethyl)piperazine (bpmp), with versatile conformations, four divalent metal–organic frameworks (MOFs), namely {[Cu2(bpmp)2(bpdc)2(H2O)2]·1.25DMF·1.5H2O}n (1), {[Zn2(bpmp)(bpdc)2]·2H2O}n (2), {[Cd(bpmp)(bpdc)(H2O)2]·2DMA}n (3), and [Cd(bpmp)1.5(bpdc)]n (4), with entangled structures from interpenetration and self-penetration to polycatenation are reported. In all the products, both bpmp and bpdc acted as linkers, connecting the metal centres into different entangled frameworks: 3D inclined polycatenane (1), 4-fold interpenetrated 3D MOF with the pcu topology (2), non-interpenetrated square net 2D MOF with sql topology (3), and self-penetrated 3D MOF (4). The solvent-dependent formations of Cd-MOFs 3 and 4 are discussed in detail as 3 isolated from DMA/water is a simple square net product, while 4 obtained from DMF/water shows a self-penetrating 3D framework in which three square circuits are interlocked with each other to form a cyclic [3]catenane unit via threading of the S-shaped bpmp. These cyclic [3]catenanes were further linked by the V-shaped bpmp, giving rise to a 3D infinite aggregate of cyclic [3]catenanes via the self-penetration, which seems to be unique. Consequently, all the products shared a square net (or square circuit) layer, which was further extended and interlocked in different ways depending on the conformations and roles of the flexible ligands together with the ligand–ligand or ligand–solvent interactions. The photoluminescence properties of the products were compared with those of free ligands and discussed. [ABSTRACT FROM AUTHOR]

Aiming at the construction of novel circularly polarized luminescence (CPL) switches with multiple switchable emission states and high dissymmetry factors (glum), topologically chiral [2]catenanes were employed as the key platform to construct a novel multistate CPL switching system. Taking advantage of the precise co‐conformation regulations of the resultant pyrene‐functionalized [2]catenanes under different external stimuli, reversible transformations between three emission states with different CPL performances, i.e. the initial "closed" form with a |glum| value of 0.012, the "open" form with an almost complete turn‐off of CPL emission, and the "protonated" form with a boosted |glum| value of 0.022, were successfully realized. This study demonstrates the successful construction of not only the first topological chirality‐based CPL switch, but also a novel bidirectional CPL switch, thus providing a promising platform for the construction of novel chiral materials. [ABSTRACT FROM AUTHOR]

An nθ graph is an n‐valent graph with two vertices. From symmetry considerations, it has vertex–edge transitivity 1 1. Here, they are considered extended with divalent vertices added to the edges to explore the simplest piecewise‐linear tangled embeddings with straight, non‐intersecting edges (sticks). The simplest tangles found are those with 3n sticks, transitivity 2 2, and with 2⌊(n − 1)/2⌋ ambient‐anisotopic tangles. The simplest finite and 1‐, 2‐ and 3‐periodic decussate structures (links and tangles) are described. These include finite cubic and icosahedral and 1‐ and 3‐periodic links, all with minimal transitivity. The paper also presents the simplest tangles of extended tetrahedra and their linkages to form periodic polycatenanes. A vertex‐ and edge‐transitive embedding of a tangled srs net with tangled and polycatenated θ graphs and vertex‐transitive tangled diamond (dia) nets are described. [ABSTRACT FROM AUTHOR]

The beauty and utility of mechanically interlocked architectures have received considerable notice from scientists in the past several decades. Plentiful scientific and technological achievements have been made and developed because of conjoining mechanically interlocked molecules (MIMs) and molecular electronic devices at nanoscale. The interaction mechanisms and translational dynamics of various MIMs, e.g., rotaxanes, catenanes, and daisy chains, have been investigated systemically through different experimental methods. On account of the recent advances of single-molecule techniques, the electrical and mechanical performance of mechanically interlocked molecular junctions (MIMJs) or nanodevices have been explored in a timely manner. In this Review, we survey the field of MIMs from a perspective of unique structural properties including topological features, translational dynamics, bistable switching properties, insulation effects, and dynamic stability present in MIMs. We then give a fundamental description of electron transport mechanisms in MIMJs for three different nanodevice geometries: (i) monolayer switching tunnel junctions (MSTJs), (ii) single-molecule junctions (SMJs) based on MIMs, and (iii) real-time transistor-like platforms. [ABSTRACT FROM AUTHOR]

Cyclodextrins (CDs) are essential in the pharmaceutical industry and have long been used as food and pharmaceutical additives. CD-based interlocked molecules, such as rotaxanes, polyrotaxanes, catenanes, and polycatenanes, have been synthesized and have attracted considerable attention in supramolecular chemistry. Among them, CD polyrotaxanes have been employed as slide-ring materials and biomaterials. CD polycatenanes are new materials; therefore, to date, no examples of applied research on CD polycatenanes have been reported. Consequently, we expect that applied research on CD polycatenanes will accelerate in the future. This review article summarizes the syntheses and structural analyses of CD polyrotaxanes and polycatenanes to facilitate their applications in the pharmaceutical industry. We believe that this review will promote further research on CD-based interlocked molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

The article titled "Template Assisted Synthesis of Linear [5]Catenane by Post-Functionalization of Templated [2]Catenane and Using Click Reaction" discusses the potential of catenated polymers to be stronger and more flexible than traditional polymers. The authors present their synthesis of linear [5]catenane as a step towards achieving polycatenane. The article provides more details on this topic and is authored by Mana Bhanjan Podh, Radhakrishna Ratha, and Chandra Shekhar Purohit. [Extracted from the article]

Type II topoisomerases modulate chromosome supercoiling, condensation, and catenation by moving one double-stranded DNA segment through a transient break in a second duplex. How DNA strands are chosen and selectively passed to yield appropriate topological outcomes – for example, decatenation vs. catenation – is poorly understood. Here, we show that at physiological enzyme concentrations, eukaryotic type IIA topoisomerases (topo IIs) readily coalesce into condensed bodies. DNA stimulates condensation and fluidizes these assemblies to impart liquid-like behavior. Condensation induces both budding yeast and human topo IIs to switch from DNA unlinking to active DNA catenation, and depends on an unstructured C-terminal region, the loss of which leads to high levels of knotting and reduced catenation. Our findings establish that local protein concentration and phase separation can regulate how topo II creates or dissolves DNA links, behaviors that can account for the varied roles of the enzyme in supporting transcription, replication, and chromosome compaction.

Polyynes are alternations of single and triple bonds between carbon atoms, while cumulenes are successions of double bonds. Since the triple bond is the strongest bond between two carbon atoms, recent preoccupations included synthesizing and condensing cyclic polyynes and cumulenes and their clusters. Density functional theory calculations predicted stable monocyclic rings formation for a number of C atoms equal to or higher than 16. Alternative to the series of Carbon atoms are alternations of Boron and Nitrogen. Large rings (such as those of 24 atoms) can be crossed and thus small clusters can be formed. Patterns of three crosses seem to further stabilize the atomic ensemble. Clusters of 4 C 24 and 4 B 12 N 12 (96 atoms) as well as 4 C 26 (104 atoms) have been designed, and their conformation has been studied here. [ABSTRACT FROM AUTHOR]

A new demetallation method for Cu(I)‐bound catenanes that contain a strong binding bis(phenanthroline) cavity using the bidentate ethylenediamine is reported. Cu(I) extraction using the organic diamine is mild, convenient and efficient, and the metal can be removed from the kinetically stable catenane complexes in various solvents within 5 minutes, offering an alternative strategy to the use of toxic cyanide in competing for the Cu(I) coordination. [ABSTRACT FROM AUTHOR]

The synthesis of [2]rotaxanes stoppered with one or two dipyrromethane groups opened a route for the construction of mechanically interlocked molecules incorporating various porphyrinoid stations. The exploitation of those precursors allowed for the creation of [3]rotaxanes and [2]catenanes based on the calix[4]phyrin motif, presenting intriguing molecular dynamics. The intrinsic flexibility of the porphyrinoid allowed the introduction of a new type of molecular motion within the rotaxanes, termed fluttering. The latter involved a bending of the axle, interconverting two angular-shaped stereoisomers of the rotaxane through a planarised transition state. Simple chemical transformations, i.e. methylation and (de)protonation of [3]rotaxane and [2]catenane allowed for the controllable transformations within the conformationally flexible calix[4]phyrin-incorporated mechanically interlocked porphyrinoids., (© 2024 Wiley‐VCH GmbH.)

Mutualisms are interactions that benefit all species involved. It has been widely investigated in neighbouring subjects, such as biology, ecology, sociology, and economics. However, such a reciprocal relationship in synthetic chemical systems has rarely been studied. Here, we demonstrate a mutualistic synthesis where byproducts from two orthogonal chemical reactions aid each other's production. Disulfide exchange and hydrazone exchange were chosen to generate two dynamic combinatorial libraries. A minor tetrameric macrocycle from the active disulfide library was quantitatively amplified in the presence of the hydrazone library. This incorporation also turned on the previously inert hydrazone reaction, producing a linear species that formed a "handcuffs" catenane with the disulfide tetramer. These findings not only lend robust support to the hypothesis of "RNA-peptide coevolution" for the origin of life but also broaden the scope of synthetic chemistry, highlighting the untapped potential of minor products from different reactions. Additionally, the co-self-assembly of these mutualistic entities to form supramolecular structures opens new avenues for future development of composite nanosystems with synergistic properties., (© 2024 Wiley‐VCH GmbH.)

Chemical composition and architecture are two key factors that control the physical and material properties of polymers. Some of the more unusual and intriguing polymer architectures are the polycatenanes, which are a class of polymers that contain mechanically interlocked rings. Since the development of high yielding synthetic routes to catenanes, there has been an interest in accessing their polymeric counterparts, primarily on account of the unique conformations and degrees of freedom offered by non-bonded interlocked rings. This has lead to the synthesis of a wide variety of polycatenane architectures and to studies aimed at developing structure–property relationships of these interesting materials. In this review, we provide an overview of the field of polycatenanes, exploring synthesis, architecture, properties, simulation, and modelling, with a specific focus on some of the more recent developments. [ABSTRACT FROM AUTHOR]

Endometrial carcinoma (EC) is the most common type of gynecologic malignant epithelial tumor, with the death rate from this disease doubling over the past 20 years. Mitochondria provide cancer cells with necessary anabolic building blocks such as amino acids, lipids, and nucleotides, and EC samples have been shown to increase mitochondrial biogenesis. In cancer, mitochondrial DNA (mtDNA) heteroplasmy studies suggest that heteroplasmic variants encode predicted pathogenic proteins. We investigated the mtDNA genotypes within peri-normal and tumor specimens obtained from three individuals diagnosed with EC. DNA extracts from peri-normal and tumor tissues were used for mtDNA-specific next-generation sequencing and analyses of mtDNA content and topoisomers. The three tumors harbor heteroplasmic somatic mutations, and at least one mutation in each carcinoma is predicted to deleteriously alter a mtDNA-encoded protein. Somatic heteroplasmy linked to two mtDNA tRNA genes was found in separate tumors, and two heteroplasmic non-coding variants were identified in a single EC tumor. While two tumors had altered mtDNA content, all three displayed increased mtDNA catenanes. Our findings support that EC cells require wild-type mtDNA, but heteroplasmic mutations may alter mitochondrial metabolism to help promote cancer cell growth and proliferation. [ABSTRACT FROM AUTHOR]