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Rotaxanes are a type of mechanically interlocked molecules (MIMs), constituted by at least a thread surrounded by a wheel, which are widely employed in the research field of artificial molecular machines. Although applications retaining the integrity of the mechanical bond are usually reported, the dethreading of the components can be crucial to develop some advanced applications. Thus, different dethreading strategies have been reported, and advanced applications which require such a process have turned out to be suitable approaches towards machine‐like operation. This review article covers recent examples of applications of pseudorotaxanes and rotaxanes in which dethreading processes have a key role to accomplish the desired function. [ABSTRACT FROM AUTHOR]

Here is reported the synthesis and study of dibenzo‐24‐crown‐8 (DB24C8)‐based [2]‐ and [3]rotaxanes that contain an ammonium as the best molecular station and carbamate moieties as secondary molecular stations. The common post‐interlocking synthesis relies on the aminolysis of the N‐succinimidyl carbonate extremity of an activated though insulated pseudorotaxane. The N‐succinimidyl carbonate‐based thread's extremity proved to be small enough to allow the slow slippage of the DB24C8 around the thread and large enough to allow insulation of the kinetically stable pseudorotaxane. Due to its sensitivity towards amine compounds, the activated carbonate end of the encircled thread allowed post‐interlocking aminolysis‐based conversion into mechanically interlocked rotaxanes by providing the same way the carbamate secondary station for the DB24C8 in the thread backbone. Translation of the DB24C8 along the threaded axle between the two molecular stations was investigated. [ABSTRACT FROM AUTHOR]

A homologous series of two‐station [2]rotaxanes incorporating amino‐acid units in the molecular thread has been developed. The degenerate [2]rotaxanes exhibit amino‐acid specific shuttling rates between two fumaric stations related to the steric factor associated to the amino‐acid side chain, as demonstrated by variable‐temperature 1H NMR spectroscopy and exchange spectroscopy (EXSY). This allows tuning of the macrocycle shuttling rate over 4 orders of magnitude, which has a relatively small solvent dependency. [ABSTRACT FROM AUTHOR]

This minireview overviews rotaxanes and pseudorotaxanes containing cyclodextrins (CDs) as the rotor component. Since CDs interact with molecules, e.g., hydrophobic compounds of the size and shape matching their cavity, to form inclusion complexes in aqueous media, CDs are an important class of macrocyclic compounds as rotor components of rotaxanes and pseudorotaxanes. Research on CD‐based rotaxanes has begun with the synthesis of rotaxanes from low molecular weight axis molecules and then developed into the construction of molecular machines and polyrotaxanes. Recently, the research has further developed into macroscopic functional materials, e.g., slide‐ring gels, macromolecular assemblies, self‐healing materials, and soft actuators. In the present article, typical examples of CD‐based rotaxanes and pseudorotaxanes are described; synthesis of rotaxane and construction of molecular machine are described in Section 2, synthesis of polyrotaxanes is dealt with in Section 3, and development of macroscopic functional materials based on rotaxane structure is discussed in Section 4. [ABSTRACT FROM AUTHOR]

The present study discusses the crystalline packing formation of several [2]rotaxanes with Leigh‐type tetralactam macrocycle bearing different threads. The presence of solvent molecules in some structures are also addressed to shed some light on this matter. Additionally, the degree of similarity between supramolecular structures of rotaxanes was discussed using similarity indices. For this, new descriptors and crystallization mechanisms, which were proposed in terms of contact area and stabilization energy, were carried out to evaluate the rotaxane molecules. It was possible to observe similar general stages of crystallization dominated by the formation of 1D‐blocks and, in fewer cases, by dimers in the first stage of nucleation. The preference for the formation of 1D nuclei resides in the large contact area and complementarity involved in the large set of interactions between the rotaxanes at the earliest stages of crystallization. In this context, it was possible to propose when solvent molecules are trapped between the rotaxanes during crystal formation. Therefore, a unique example of a rotaxane whose topology favored the entrapment of water molecules between rotaxanes during the first stage of the crystallization process is presented. Crystallization mechanisms showed to be a valuable asset in the supramolecular investigation of rotaxanes in the crystalline state. [ABSTRACT FROM AUTHOR]

One‐pot synthesis of various α‐cyclodextrin‐(α‐CD‐) based [3]rotaxanes in water and their structural modifications are discussed in detail. Pseudo[3]rotaxane was prepared from α‐CD and α,ω‐diaminododecane in water (above 100 g, quantitative yield in a 1 L flask). Successive urea‐forming end‐capping reactions with isocyanate in water selectively afforded [3]rotaxane with head‐to‐head structured α‐CDs. The yields were varied by bulkiness and functionality of end‐capping agents. Significant modifications of the axle end and wheel OH group of the [3]rotaxanes were performed by the Suzuki coupling with arylboronic acids and by the perfect acylation with acid anhydrides, respectively. [ABSTRACT FROM AUTHOR]

Research at the University of Freiburg is summarized which aimed at realizing catenanes, rotaxanes, and a molecular knot from 61–62 until 41 years ago. Taking a fresh view at ansa‐compounds – distinct from those in which he had been interested for other reasons before – Arthur Lüttringhaus began to tackle syntheses of catenanes in 1957. The first isolation of a pure catenane (37) succeeded in 1964 jointly with Gottfried Schill. Most of the progress made in the sequel was due to Schill alone or achieved under his direction; in addition, a few follow‐up studies were published without Schill or Lüttringhaus being their authors. The major feats of these endeavors were the syntheses of the following molecules: (1) the first catenanes (38 – de‐acetyl‐41, 74) without a ring in any constituent (this feature makes them unique till today; the catenane 74 holds the additional record of being the only all‐hydrocarbon catenane till now); the first [3]catenanes at all (obtained as a mixture of constitutional isomers C2v‐97 and C2h‐97); the first [3]catenanes exhibiting topological isomerism (89, iso‐89, and neo‐iso‐89); the rotaxanes 70 [which had the design peculiarity of being convertible into a catenane (74)], 113 (Schill's #1‐rotaxane), and 115; the pre‐knotane rac‐dia‐iso‐123 [provided it was obtained and not (only) its topological isomer dia‐iso‐123]. – For due perspectives, pertinent studies of third parties are included, too: 1) Wasserman's reports on the isolation of the catenane 8 are analyzed in great detail; the conclusion is that the identity of 8 was never established. 2) Schill's oscillating rotaxane 70 from 1988, which is subject to a reversible and non‐degenerate ring migration (→ iso‐70), is supplemented by Stoddart's much faster oscillating rotaxane 71 from 1991, which undergoes a reversible and degenerate ring migration (→ 71 instead of → iso‐71) and was dubbed "molecular shuttle". 3) The first [3]catenanes from the groups of Schill (97; 1969), Sauvage (98 and 99; 1985), and Stoddart (100–102; 1991) are juxtaposed. 4) The Harrisons' synthesis of the rotaxane 106 by a most noteworthy solid‐phase approach (1967) is recalled in the context of Schill's synthesis of the rotaxane 113 (1967 or 1969). 5) Attempts at threading α‐cyclodextrin by long‐chain 1,ω‐dithiols (→ 130) and ring‐closing the latter oxidatively for obtaining catenated disulfides failed in Lüttringhaus' 1957/1958 studies; in contrast, Stoddart's threading permethyl‐β‐cyclodextrin (133) by the long‐chain 1,ω‐diamine 132 and ring‐closing the latter by a double condensation with terephthaloyl dichloride was successful by providing 3 % of the catenated bislactame 134 in 1993. The concluding section characterizes the synthetic strategies towards catenanes and rotaxanes developed in Freiburg as "template‐based". This differs from the Nobel Prize Committee's assessment. [ABSTRACT FROM AUTHOR]

This study investigated the proper classification and quantification of intercomponent trifurcated hydrogen bonds, in the crystalline state, of rotaxanes bearing a tetralactam Leigh‐type macrocycle. Quantum mechanical calculations were carried out to obtain the interaction paths and their stabilization energies. In general, the use and necessity of fragmentation in types of interaction have been reported in the literature, although they are commonly performed only using a geometric approach. This results in N–H···O interactions that are indicated as the main interactions between components, neglecting other possible interactions. The use of energetic fragmentation was demonstrated here under an appropriate demarcation considering all interactions and showing the existence and role of the C–H···O interaction. The C–H···O interactions showed similar energy to N–H···O interactions with average values around –4.75 kcal mol–1 and –4.60 kcal mol–1, respectively. This revealed that the three hydrogen bonds are part of a cooperative set of interactions with a similar contribution. The trifurcated hydrogen bonds presented high contribution in the total intercomponent stabilization energy of the rotaxanes, with an average value of 51 % in the studied series. [ABSTRACT FROM AUTHOR]

The activation energies of the shuttling of [2]rotaxanes with various N‐arylpyrrole moieties were determined by variable temperature (VT) 1H NMR experiments. The value provided a new quantitative scale for the estimation of the steric bulk of the substituents. The rigidity and the electronic effect of the substituents, which could inadequately influence the estimation of the steric bulk, were minimized in the method we presented. [ABSTRACT FROM AUTHOR]

Mechanically interlocked molecules (MIMs) have emerged as intriguing building blocks for the construction of stimuli‐responsive devices and materials. A particularly interesting and well‐implemented subclass of MIMs is composed of symmetric bistable [c2]daisy chain rotaxanes. Topologically, they consist in the double thread of two symmetric macrocycles that are covalently linked to an axle bearing two switchable stations and a bulky stopper to avoid unthreading. Herein we report the synthesis and characterization of a series of unsymmetric bistable [c2]daisy chain rotaxanes that present two different electroactive units as stoppers (an electron donor triarylamine and an electron acceptor perylene bisimide unit). Using a combination of 1D and 2D NMR along with cyclic voltammetry, we demonstrate that the pH actuation of the mechanical bond can be used to modulate the electrochemical properties of the bistable [c2]daisy chain rotaxanes when switching between the contracted and extended forms. [ABSTRACT FROM AUTHOR]

Tailoring synthetic strategies toward complex, but well‐defined, molecular architectures is an important aspect of Today's organic chemistry. Herein, we present designs to build up [3]rotaxanes of Type 2.1 and Type 3 that feature both a polyyne and a cumulene axle in a single mechanically interlocked molecule. The combination of two sp‐hybridized carbon chains was achieved by functionalization of a phenanthroline‐based macrocycle, which allowed the coupling of two [2]rotaxanes toward Type 3 [3]rotaxanes with two polyynes, two cumulenes, or one polyyne and one cumulene axle. The structures have been established by NMR and UV/Vis spectroscopies, as well as high‐resolution mass spectrometry. A [3]rotaxane of Type 3, featuring two [9]cumulene axles, has been assembled and spectroscopically characterized despite expectations that it would be unstable. This represents only the second cumulene rotaxane reported to date. All designs and attempts to form [3]rotaxanes of Type 2.1, which combine a polyyne and cumulene threaded through a single macrocycle, have been unsuccessful. [ABSTRACT FROM AUTHOR]

Pillar[5]arene‐containing [2]rotaxanes have been efficiently prepared under solvent‐free conditions. Specifically, solid‐to‐solid ball‐milling of primary or secondary amine reagents with the inclusion complex resulting from the association of dodecanedioyl dichloride and a pillar[5]arene derivative provided the corresponding diamide [2]rotaxanes in good to excellent yields. Importantly, [2]rotaxanes difficult or even impossible to prepare under classical reaction conditions in solution, are now easily obtained. [ABSTRACT FROM AUTHOR]

The thermally and photochemically induced dethreading of a series of pseudo[2]rotaxanes bearing tetraalkyl‐substituted fumaramide axles and polyamide macrocycles is reported herein. The length of the alkyl chains at the ends of the thread, the void size, and flexibility of the macrocycle and the intercomponent interactions are critical for a satisfactory dethreading process. 1H NMR kinetic experiments were carried out in order to calculate the rate constants of the thermal dethreading processes and stabilities of the rotaxanes, by comparing with the similar data for the deslipping of the succinamide surrogates. The deslipping reaction occurs faster with the fumaramide systems than succinamide ones. The incorporation of adamantane moieties into the polyamide macrocycle drastically slowed down the disconnecting process. Furthermore, interlocked systems with dipropylamino groups as stoppers experienced a rapid dethreading when irradiated under UV‐light, a process triggered by the fumaramide–maleamide isomerization. In this case, the n‐propyl groups are not bulky enough to keep together both components as the number of hydrogen bonds between thread and macrocycle is halved in the maleamide systems. [ABSTRACT FROM AUTHOR]

Understanding the role played by the nature, number, and arrangement of binding sites anchored to a macrocycle remains a topic of current interest for the synthesis of new interwoven species. We report the synthesis and detailed structural characterization of a new calix[6]arene derivative decorated with two phenylureido groups anchored at the diametrical position of the calix upper rim that adopts a 1,2,3‐alternate conformation in solution and in the solid state. Preliminary data on the ability of this host to form redox‐active pseudorotaxanes and rotaxanes are reported. [ABSTRACT FROM AUTHOR]

Two [2]rotaxanes have been assembled in water from modular subunits through CuI-catalyzed azide--alkyne "click" chemistry. For this purpose, 2,6-disubstituted naphthalene axles with solubilizing oligo(ethylene glycol) (OEG) chains (n = 1-5) and propargyl terminal groups were synthesized and examined for their propensity to form inclusion complexes with a dicationic Diederich-type cyclophane host. The dependence of pseudorotaxane formation on the linkers between the naphthalene core and OEG chains, and in the case of ester linkers on different spacer lengths, was analyzed by titration experiments. In addition, the inclusion complexes of two [2]rotaxanes were trapped by using a water-soluble azide-functionalized stopper. Repetitive chromatography finally enabled the isolation of both mechanically interlocked [2]rotaxanes. [ABSTRACT FROM AUTHOR]

Rotaxanes are designated as molecular machines due their different movements. Systematic studies regarding the different conformations adopted by these systems and the factors that lead to the distribution of the conformations, in both solution and the solid state, have not been widely explored, especially for rotaxanes with nonsymmetric stoppers. Therefore, in this study we have investigated three novel [2]rotaxanes containing threads derived from nonsymmetric succinamides [R1R2NC(O)‐CH2CH2‐C(O)NR2R1, with R1/R2 = Bu/Bn, Bu/2‐furylmethyl, and 5‐methylisoxazol‐3‐yl/2‐furylmethyl]. The proportions of rotamers were investigated for threads and rotaxanes by solution and solid‐state NMR spectroscopy as well as by single‐crystal and powder X‐ray diffraction. In solution, the threads present different proportions of conformer, with the E,Z conformation prevailing, whereas only one conformer is observed in the solid state. For the rotaxanes, only one conformer prevails in the single crystal, whereas the solution and solid (bulk) states present more than one rotamer. These proportions are modified when the threads are incorporated into the macrocycle during rotaxane formation. The intramolecular interactions in each rotamer were investigated by QTAIM and variable‐temperature 1H NMR experiments. The changes in conformational population between the threads and respective rotaxanes can be explained by a set of different intramolecular interactions, with trifurcated hydrogen bonds responsible for most of the stabilization energy. [ABSTRACT FROM AUTHOR]

Oriented rotaxanes composed of tris( N-phenylureido)calix[6]arene wheel 1 and N, N′-dialkyl viologen-based axles were synthesized in which the span between the diphenylacetyl stoppers at the wheel upper and lower rim and the bis-pyridinium cation portion of the axial component is different in length. A sequential synthetic pathway was followed to achieve the selective formation of orientational isomers, wherein the short (or long) chain of the axle is positioned either on the upper or lower rim of the wheel. The synthetic strategy adopted involves the upper rim threading of axles 2a- c to yield oriented pseudorotaxanes, which were then stoppered in situ. The structure of the oriented rotaxanes was unravelled by detailed NMR experiments, and their spectroscopic, electrochemical and dynamic properties were investigated by UV/Vis, cyclic voltammetry, and EPR measurements. The results were compared with those of their symmetric counterparts. [ABSTRACT FROM AUTHOR]

Alongside the use of metal cations and π–π stacking, hydrogen bonding is one of the major templating interactions used to prepare rotaxanes and catenanes. In this review, a brief summary of key historical milestones will be followed by discussion of developments from over the last decade in both synthetic methodology and application of hydrogen bond templated interlocked molecules. Hydrogen bond templation can allow for rapid access to interlocked molecules in high yields, with select examples having been put to useful purpose, in applications such as organocatalysis and cellular imaging. [ABSTRACT FROM AUTHOR]

Guest editor Jean‐Pierre Sauvage introduces the Special Issue dedicated to 50 Years of Rotaxanes. [ABSTRACT FROM AUTHOR]

Pillar[5]arene-based [2]rotaxanes have been prepared from the reactions of diacyl chloride reagents with various amine stoppers. The yields of the [2]rotaxanes are sensitive to the reaction conditions (solvent and stoichiometry) as well as to structural and electronic factors. In particular, the nature of the starting amine reagent has a dramatic influence on the yields of [2]rotaxanes; thus, the reaction outcome is not simply related to the binding constant of the diacyl chloride reagent with the pillar[5]arene. Indeed, the differences in the yields must be related to the different affinities for the various monoacylated intermediates. The yields of the [2]rotaxanes are also influenced by several structural factors such as the chain length of the diacyl chloride reagent and the size of the peripheral substituents of the pillar[5]arene building block. Finally, the preparation of [2]rotaxanes from alkyldiamine reagents and acyl chloride stoppers has also been investigated. [ABSTRACT FROM AUTHOR]

O-acylation, cyclodextrins, MALDI-TOF-MS, rotaxanes, vinyl-group introduction Keywords: O-acylation; cyclodextrins; MALDI-TOF-MS; rotaxanes; vinyl-group introduction EN O-acylation cyclodextrins MALDI-TOF-MS rotaxanes vinyl-group introduction 1 1 1 03/24/23 20230321 NES 230321 B The Cover Feature b illustrates the acylation reaction of cyclodextrin (CD)-based [3]rotaxane. In this reaction system, one [3]rotaxane has 36 hydroxyl groups on two CD units, and excess of methacryl anhydride was added, as shown on the background. [Extracted from the article]

The acylation of a cyclodextrin‐based [3]rotaxane was implemented with anhydride reagents following a facile procedure. Methacrylic anhydride facilitated the introduction of a vinyl‐group into the rotaxane structure toward achieving a crosslinker. Interestingly, only a few methacrylic units were attached to the cyclodextrin at reaction temperatures of up to 60 °C even with an excess amount of the reagent, probably due to steric hindrance. Therefore, the number of vinyl groups on the [3]rotaxane framework was easily controlled to be approximately two units via a simple random acylation, which worked effectively as a facile synthesis route for the rotaxane crosslinker. The acylation behavior was investigated in detail by NMR and MALDI‐TOF‐MS analyses. Such a proposed approach will help overcome the trade‐off between convenience and utility associated with the mono‐modification of cyclodextrins. [ABSTRACT FROM AUTHOR]

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 alkyneterminated 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 alkalimetal ions. [ABSTRACT FROM AUTHOR]

The helical structures of m-ethynylpyridine (2,6-pyridyleneethynylene) oligomers have been stabilized by mechanical crosslinking. A heptameric oligomer, in which the two terminal pyridine rings bear two carbaldehyde groups, has been designed. When this heptamer was treated with octyl β- d-glucopyranoside, a circular dichroism (CD) band was induced at around 330 nm, which corresponds to the formation of a chiral ethynylpyridine helix. The CD band was enhanced by the addition of a diamine and a diammonium dumbbell as a result of the formation of a [3]rotaxane structure linked to the terminal pyridines of the helical structure. A decameric oligomer containing four diformylarene units showed stronger CD enhancement in similar experiments owing to two crosslinking events. [ABSTRACT FROM AUTHOR]

Pseudorotaxane type host-guest complex of a secondary ammonium salt and oxacalixcrown with the polyether linker as short as five ethylene glycol units was created. While an axle containing both ammonium and carbamate stations was installed in an oxacalixcrown-6-based [2]rotaxane through a threading-followed-by-stoppering approach, translocation of the oxacalixcrown-6 component of the [2]rotaxane from the secondary ammonium station to the carbamate station of the thread was achieved through blocking the amino moiety with a bulky Boc group. [ABSTRACT FROM AUTHOR]

A non-symmetrical pH-sensitive bistable [2]rotaxane that bears a cholesterol unit and a tetraphenylmethane group as stopper groups was designed and synthesized in 18 steps. The successful formation of the rotaxane was proven by NMR spectroscopy and MS/MS. Besides a permanent cationic alkylated triazolium unit, the axle contains a secondary amine that can act as a second pH-sensitive binding site for a crown ether. Depending on the protonation state of this amine function, the crown ether reversibly changes its position by moving between the two binding sites along the axle, as revealed by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The article features a selection of work that has recently been published in other journals. One study describes the preparation of anion-templated rotaxanes incorporating an optical- and electroactive osmium(II) bipyridyl reporter group. Another study examines how ethanol electro-oxidation catalysis depends on differences in the particle size distribution of supported platinum-nanoparticle catalysts.

A [2]rotaxane shuttle for (light-driven) proton transport has been designed and synthesized. The rotaxane contains a macrocyclic ring that carries a pyridine nitrogen atom as a basic center to bind and to transport a proton. The axis includes an amide binding site for the macrocycle and a positive charge in close vicinity. Upon protonation of the pyridine nitrogen atom, the hydrogen bond is broken and Coulomb repulsion between the protonated pyridine and the permanent positive charge in the axis pushes the protonated macrocycle to the other end of the axis. By variation of the pH the ring can shuttle to and fro. Its locations on the axis were determined by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Inherent chirality represents a distinct category of molecular chirality that does not fall within the traditional classification of four chiral elements: central, axial, planar, and helical chirality. While extensive research has been conducted on the catalytic enantioselective construction of these conventional chiralities, the corresponding synthesis of inherently chiral molecules has remained largely unexplored. This minireview provides a comprehensive summary of recent advancements in this field, focusing on the catalytic asymmetric synthesis of inherently chiral calixarenes, saddle‐shaped tetraphenylenes and their heterocycle derivatives, mechanically planar chiral rotaxanes and chiral multilayer 3D frameworks, as well as our perspective in this field. [ABSTRACT FROM AUTHOR]

The cover picture shows a pseudorotaxane intermediate bearing an acyl chloride unit ready to react with an amine stopper to afford a pillar[5]arene‐based [2]rotaxane. The yield of [2]rotaxane is sensitive to the reaction conditions but also to electronic and structural factors, in particular the nature of the amine reagent and the size of the peripheral groups on both rims of the pillar[5]arene building block. Details are discussed in the article by R. Deschenaux, J.‐F. Nierengarten et al. on 479 ff. [ABSTRACT FROM AUTHOR]

Mechanically interlocked molecules (MIMs) carry great potential in different fields of chemistry, based on their specific structures, their internal dynamics, their stimuli‐responsive behavior, and other unique features of the mechanical bond. This minireview presents some of the most recent developments in their use for medical and biological applications. For example, they have been used to influence, enhance or block the action of therapeutic agents to enable targeted drug delivery. The dynamic structural properties have been used to generate switches and transporters, as well as sensors for various medically relevant species. Building MIMs by incorporating biomolecules like DNA and proteins has served as a novel way to control their properties. [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]

The front cover matter of a 2015 issue of the journal "European Journal of Organic Chemistry" is presented, along with the table of contents.

Mechanically interlocked molecules have found extensive applications in areas all across the physical sciences, from materials to catalysis and sensing. However, introducing mechanical bonds and entanglements at the molecular level is still a significant challenge due to the inherent restriction in entropy needed to preorganize strands before interlocking. Over the last decade, dynamic covalent chemistry has emerged as one of the most efficient methods of forming rotaxanes, catenanes and molecular knots. By using reversible bonds such as imines, disulfides and boronate esters, one can use the inherent error‐correction in these linkages to form interlocked architectures with high fidelity and often in excellent yields. This review reports on recent advances in the use of dynamic covalent chemistry to make mechanically interlocked molecules, systematically surveying clipping, capping and templating approaches with dynamic bonds. Furthermore, it is also discussed how dynamic bonds can be used to control motion, co‐conformational expression and catalytic activity in mechanically interlocked molecular machinery. [ABSTRACT FROM AUTHOR]

Keywords: Antitumor agents; Rotaxanes; Sensors; Supramolecular chemistry; Theranostics EN Antitumor agents Rotaxanes Sensors Supramolecular chemistry Theranostics 5104 5104 1 10/19/21 20211007 NES 211007 B The Front Cover b shows an artistic rendition of a cell culture incorporating mechanically interlocked molecules (MIMs), illustrating different strategies in which they have been applied for biological and medical functions. Front Cover: Mechanically Interlocked Molecules for Biomedical Applications (Eur. J. Org. Antitumor agents, Rotaxanes, Sensors, Supramolecular chemistry, Theranostics. [Extracted from the article]

Considerable research efforts have been devoted to the development of rotaxanes and the study of their unique dynamic properties. This minireview provides an overview of the main advances that have been realized in rotaxane architectures involving different types of carbon nanostructures. In particular, rotaxanes based on fullerenes and carbon nanotubes will be discussed. [ABSTRACT FROM AUTHOR]

Porphyrins have been widely recognized for their unique photo‐ and electrochemical properties as well as their crucial roles in a wide variety of biological processes including catalysis, oxygen transport, and photosynthesis. In addition, their size and predictable coordination geometries makes them attractive components in the assembly of functional supramolecular assemblies. Advances in porphyrin synthesis have enabled their incorporation into rotaxanes not only as stoppers but also as components of the macrocycle, or even higher order rotaxane architectures, each design imparting unique functionality either through redox, fluorescence, or coordination environment. Here we describe advances in the synthesis of increasingly complex porphyrin‐containing rotaxane assemblies and their dynamic properties that arise from the porphyrin inclusion. [ABSTRACT FROM AUTHOR]

A family of three molecular shuttles based upon ammonium/triazolinium salt motifs with one, two, and three catalytic centers were prepared along with their corresponding non-interlocked threads. The switching process for all rotaxanes was tested through an in situ procedure in solution. Furthermore, their organocatalysis of two Michale-type reactions by iminium activation was tested to check whether the increase of the number of catalytic centers in the same shuttle is a decisive factor to improve their efficiencies compared with those of single-active-site organocatalytic shuttles under the same conditions. [ABSTRACT FROM AUTHOR]

Despite their anticipated utility and aesthetic appeal, attempts to prepare extended molecular daisy chains have been thwarted by preferential formation of cyclic dimers ([c2]‐rotaxanes). Previously, to circumvent this limitation, an alternative type of molecular chain has been synthesized by linking pre‐prepared [c2]rotaxanes already interlocked with bulky capping groups. Instead of this stepwise approach, here we describe the direct self‐assembly of dimeric complexes and their in situ oligomerization, which simultaneously interlocks the dimers so that no prior capping of the complexes is required. Eight individual supramolecular species, including a tetramer, hexamer, octamer and decamer series, have been isolated and characterized. The decamer is derived from 16 molecular components, through ten highly selective reactions of six equivalents of the bifunctional linking reagent with five self‐assembled dimeric cyclodextrin inclusion complexes, all in one pot. [ABSTRACT FROM AUTHOR]

Here are reported the synthesis and characterization of four new dibenzo‐24‐crown‐8 (DB24C8)‐based ammonium‐containing pseudorotaxanes, for which one of the two encircled axle's extremities consists of a perfluorobutyl moiety. The subsequent dethreading of the DB24C8 over the perfluorobutyl extremity was studied. Although the perfluorobutyl extremity of an ammonium‐containing axle did not allow threading of DB24C8, dethreading of a perfluorobutyl extremity‐containing pseudorotaxane was possible and its rate depended on both the strength of the template‐to‐DB24C8 complex and the nature of the axle. In particular, dethreading process may be assisted by the presence, in the threaded axle, of a poor secondary site of interaction for the DB24C8 and this assistance proved to be higher when this site is close to the DB24C8. [ABSTRACT FROM AUTHOR]

In this report, our work describing the use of spin probes in the field of supramolecular chemistry and how electron spin resonance (EPR) has been used for detecting and identifying supramolecular assemblies is shortly reviewed. Selected examples are reported, including paramagnetic host–guest complexes, self‐assembled systems doped with spin probes, spin‐labelled macrocycles and open shell mechanically interlocked structures (MIMs) such as rotaxanes, in which the dumbbell, the wheel or both are tagged with nitroxide radicals. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a new member of the pillar[5]arene family carrying a paramagnetic side-arm based on the 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO) moiety has been achieved by the Huisgen-type CuAAC reaction. The possibility of exploiting the proposed pillar[5]arene as a host in paramagnetic rotaxane-like structures was tested in the presence of charged guests and confirmed by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

A ethylene glycol bridged pyridine and pillar[5]arene based mechanically selflocked pseudo[1]rotaxane was constructed successfully. The structure and selflocked conformation of pseudo[1]rotaxane were confirmed by 1H, 2D NMR spectrum and HR‐ESI‐MS. It was found that in dilute solution the pseudo[1]rotaxane could be operated as an acid/base‐controllable two state molecular shuttle while In concentrated solution, the pseudo[1]rotaxane existed as a dimer and could be operated from shrinking state to extension state. [ABSTRACT FROM AUTHOR]

The selective electrochemical sensing of heavy halides, such as bromide, over more charge‐dense counterparts, like chloride, using mechanically‐interlocked structures remains a formidable challenge. Using the active‐metal templation methodology, the first redox‐active ferrocene‐appended rotaxane containing an all‐halogen bonding anion binding cavity was synthesised. 1H NMR binding studies in aqueous–organic solvent media demonstrated a marked recognition bias for heavy halides, facilitating the selective redox sensing of bromide over chloride to be demonstrated for the very first time with an interlocked host molecule. [ABSTRACT FROM AUTHOR]

Modified crown ethers are fundamental building blocks in supramolecular chemistry, with applications in phase transfer catalysis, metal extraction, smart materials, and molecular machines. Here we report on a one‐pot highly chemo‐ and regioselective photocatalytic fluoroalkylation protocol for the mono‐functionalization of benzo substituted crown ethers. For this important class of macrocycles, the method described here represents one of the few late‐stage functionalization procedures that is both high yielding and scalable. Because of its breadth of scope and substrate tolerance, the devised approach can be applied to a wide range of aromatic crown ethers (18 examples, up to 99 % yield), including those engaged in mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]