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Highlights • Solutol/α-CD forms poly(pseudo)rotaxane instantaneously maintaining drug solubility. • Soluplus/α-CD interactions require 48 h and decrease drug solubility. • PEG distribution in the copolymer determines poly(pseudo)rotaxanes structure. • Soluplus poly(pseudo)rotaxane dispersions showed viscoelastic behavior. • Drug release was modulated by formation of soluble/insoluble poly(pseudo)rotaxanes. Abstract This work aimed to design supramolecular gels combining Soluplus or Solutol and alfa- and hydroxypropyl-β-cyclodextrin (α-CD, HPβ-CD) for carvedilol (CAR) transdermal delivery. Poly(pseudo)rotaxane formation (appearance, SEM, 1H NMR), drug solubilization, rheological properties and in vitro release were investigated. CAR-CD complexes were prepared in situ or by spray drying. For Solutol, poly(pseudo)rotaxanes were formed immediately after mixing with α-CD and did not influence CAR solubility. Differently, Soluplus poly(pseudo)rotaxanes took 24–48 h to be formed and CAR solubility decreased compared to Soluplus micelles. Soluplus 20% + α-CD (5–10%) showed higher G' and G'’ but also faster CAR release than Solutol poly(pseudo)rotaxanes, which is explained by the different location of PEG chains in the two amphiphilic polymers. Faster drug release was achieved incorporating HPβ-CD or CAR-HPβ-CD spray-dried complexes. The results evidenced the versatility of the formulations in terms of rheological behavior and drug release patterns, which can be adjusted for CAR transdermal delivery. [ABSTRACT FROM AUTHOR]

A mechanical bond serves as a distinctive approach for harnessing the most beneficial features of both covalent and supramolecular chemistries, offering stability and structural adaptability owing to its unique dynamic nature. Molecules formed by mechanical bonding, known as mechanically interlocked molecules (MIMs) including catenanes, rotaxanes, and knots have opened new possibilities. Notably, the introduction of mechanically interlocked structures into polymers has led to the emergence of novel polymeric materials referred to as mechanically interlocked polymers (MIPs), such as polyrotaxanes and polycatenanes. The interlocked nature of these architectures can lead to particular conformational freedom and high mobility of their components, resulting in exceptional properties, such as ultra-stretchability, toughness, and immediate recoverability. These properties have found potential applications in diverse fields, including the development of tough hydrogels, scratch-resistant coatings, smart actuators, and batteries. Recent years have witnessed a surge in the synthesis and investigation of a diverse array of rotaxane-based MIPs, an essential class that has enabled researchers to begin grasping the impact of incorporating mechanical bonds within polymer structures, and of their mobility, on material properties. In this review, an overview of the dynamics of ring-containing polymers is presented. The review encompasses macromolecular rotaxanes, polyrotaxanes, and slide-ring networks, including the role of ring mobility in shaping the dynamics and properties of rotaxane polymers. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of functionalized pillar[5]arenes mono-pyridylimine derivatives with different lengths of diaminoalkylene units as the side chains on the pillar[5]arene's rim were conveniently synthesized. The investigation of 1 H NMR spectra and single crystal structures indicated that the formation of free forms or pseudo[1]rotaxanes turned out to be controlled by both the axle lengths of diaminoalkylene chains and the solvent effect. The pillar[5]arene mono-pyridylimines with short hydrazinyl and diaminoethylene chains exist in free form. On the other hand, pillar[5]arene mono-pyridylimines with longer than diaminopropylene chains formed stable pseudo[1]rotaxanes both in solution and in the crystal state. [ABSTRACT FROM AUTHOR]

[Display omitted] In [2]rotaxanes, hydrogen bonding interactions are found to be one of the prominent factors driving the templation of the macrocycle to the molecular axle. Several hydrogen bonding templating moieties like amides, hydrazones, nitrones, and squaraines have been incorporated into the molecular axle and the macrocycle for generating hydrogen bonding [2]rotaxanes. This review focuses on the design and synthetic strategy adopted in rendering various molecular axles, which can be used to generate [2]rotaxanes for numerous applications. Moreover, a detailed description is provided with suitable mechanistic insights about the utilization of hydrogen bonding [2]rotaxanes in applications like molecular motors, organic synthesis, and catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Cytotoxic agents that specifically target cancer cells are in high demand. Modifying drugs with targeting groups however, can produce deleterious effects on drug pharmokinetics. In this study, platinum (Pt) was linked with host-rotaxanes to discover the effect on the cytotoxicity of Pt when carried by a highly modified rotaxane as a ligand. One host-rotaxane (Pt-BocRot) contains the basic components of a rotaxane: wheel (with a Boc protecting group), axle, and blocking group. A second rotaxane (Pt-ArgRot) contains arginine moieties on its wheel instead to potentially improve association with the phosphate groups on cell membranes or DNA backbone. The cytotoxicities of the rotaxanes and various model compounds were determined using ovarian cancer SKOV-3 cell line, which is resistant to cisplatin. We found Pt-ArgRot was slightly more cytotoxic than Pt-BocRot. Both were clearly more cytotoxic than rotaxanes without Pt and the model compounds. As importantly, they killed cells through an apoptotic mechanism. These results suggest that targeting agents for a particular cell type can be incorporated with Pt-complexes using the rotaxane architecture to improve drug specificity. [Copyright &y& Elsevier]

Two functional [2]rotaxanes, with a 4-morpholin-naphthalimide fluorophore as one of the two stoppers and a difluoroboradiaza- s -indacene functionalized dibenzo[24]crown-8 as macrocycle, were designed, synthesized and well characterized. [2]Rotaxane 1 and 2 had almost the same structural skeleton, and a ferrocene unit was introduced in [2]rotaxane 1 as the other stopper, while a 3,5-dimethoxybenzene stopper in [2]rotaxane 2 . It has shown that efficient energy transfer process in both two [2]rotaxanes occurred from the 4-morpholin-naphthalimide donor to the difluoroboradiaza-s-indacene acceptor. Moreover, [2]rotaxane 1 exhibited a remarkable fluorescence increase in response to the addition of base that can drive the shuttling motion because of the introduction of ferrocene electron donor. This work can pave the way for the design and construction of complex and functional molecular systems based on the mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

Main chain polyaramides were prepared by the Highashi protocol from oxydianiline (ODA) and isophthalic acid (ISOPA) in the presence of 30-crown-10 and “60-crown-20”. Relatively small amounts of the smaller macrocycle were incorporated (<2 mass %), but the larger one resulted in ∼17 mass % incorporation. These polymers display a previously observed irreversible high temperature exothermic transition that is attributed to a solid-state reorganization to intermolecularly hydrogen bonded amide pairs. An analogous set of polymers was prepared from bis( p -aminophenyl)fluorene (FLUODA) and ISOPA, with similar results, except that the exothermic transition was not observed. A main chain polypseudorotaxane was also prepared from Nylon-6,6 by condensation of adipoyl chloride and hexamethylene diamine in the presence of 30-crown-10; again only a small amount (∼5 mass %) of the macrocycle was threaded onto the backbone. [ABSTRACT FROM AUTHOR]

Abstract: Host–guest complexation between an alkane functionalized with triazole moieties and three pillar[5]arenes was studied. Three pillar[5]arene-based [2]rotaxanes were constructed based on this new recognition motif. The sequence of the yields of these [2]rotaxanes was consistent with the order of association constants between the three corresponding pillar[5]arenes and the alkane. 1H NMR, electrospray ionization mass spectrometry, and NOESY NMR were employed to characterize these [2]rotaxanes. [Copyright &y& Elsevier]

Abstract: Hydrogen bonded arylamide foldamers have been introduced in switchable pseudo[2]rotaxanes and [2]rotaxanes, which also include a cyclobisparaquat(p-phenylene) (CBPQT4+) ring and a ‘dumbbell’ containing tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP, for rotaxanes). The foldamer size changes through folding and unfolding serve as a steric handle to modulate the mechanical movement of the CBPQT4+ ring along the dumbbell of the pseudo[2]rotaxanes and [2]rotaxanes. By varying the number of the repeating units in the foldamer, the kinetics of the solvent-dependent slippage/deslippage of pseudo[2]rotaxanes and the switching of the ring between TTF and DNP of the [2]rotoxanes can be tuned remarkably, with the time scope ranging from several minutes to several days, in twelve solvents of varying polarity, which have been confirmed by the 1H NMR, UV–vis spectroscopy, and cyclic voltammogram experiments. [Copyright &y& Elsevier]

Abstract: This Letter describes the formation of pseudo[3]rotaxanes containing calix[4]-bis-crowns, exhibiting a 1,3-alternate conformation and large crown cavities, and secondary ammonium ions. The first and second association constants of pseudo[3]rotaxane formation are moderate (K 1 =175, K 2 =100M−1) and are higher than that of the corresponding pseudo[2]rotaxane (K =24M−1), consisting of a calix[4]-mono-crown and the same secondary ammonium ion. [Copyright &y& Elsevier]

Abstract: Host–guest complexation between a dibenzo-24-crown-8-based cryptand and a paraquat derivative was studied. Subsequently, two novel [2]rotaxanes based on the dibenzo-24-crown-8-based cryptand/paraquat recognition motif were prepared by threading-followed-by-stoppering method and single-pot method, respectively. The obtained mechanically interlocked structures were confirmed by 1H NMR, 13C NMR, 2D NMR, and ESI-MS. [Copyright &y& Elsevier]

Rotaxanes are a new class of interesting macromolecules, composed from two interlocked, mobile parts. They can be processed into good optical quality thin films and exhibit interesting second and third-order nonlinear optical properties. In solution the macrocycle rotate around the thread, as it was shown previously by the electro-optic Kerr effect and NMR. The measured frequency of rotation agrees well with theoretical calculations and depends on temperature as well as on the applied external field strength. Rotaxanes can be poled, similarly as functionalized polymers. Using the third harmonic generation technique a clipping movement was demonstrated when shining in the thread absorption band. [Copyright &y& Elsevier]

Abstract: The Cu(I)-catalyzed dipolar cycloaddition of azides and terminal alkynes (‘click’ chemistry) has been used as a mild and efficient stoppering reaction for the preparation of new copper(I)-complexed rotaxanes. [Copyright &y& Elsevier]

Abstract: Linked symmetrical [3] and [5]rotaxanes consisting of an oligomeric phenylene ethynylene (OPE) framework as a π-conjugated guest moiety and lipophilic permethylated α-cyclodextrins (PM α-CDs), as macrocyclic hosts have been prepared by double intramolecular self-inclusion of an OPE guest unit carrying two PM α-CDs followed by capping with bulky stopper groups using click azide–alkyne Huisgen cycloaddition or Sonogashira coupling. The structures of these linked rotaxanes were determined by MALDI-TOF mass spectrum and two-dimensional NMR spectroscopy. [Copyright &y& Elsevier]

Abstract: We have synthesized a series of three rotaxanes constituted of a calix[6]arene wheel and a 4,4′-bipyridinium unit on the axle, which differ in the length of the two aliphatic chains that connect the central bipyridinium unit with the two terminal stoppers. We have investigated the photophysical and electrochemical properties of these systems and of suitable model compounds in two prototypical solvents, namely, acetonitrile and methylene chloride. Our results show that these rotaxanes are characterized by a complex pattern of intercomponent interactions whose strength can be influenced by the length of the axle as well as the nature of the solvent. [Copyright &y& Elsevier]

Abstract: This Letter describes an efficient method—one that takes advantage of hydrogen bond-guided self-assembly and ruthenium-catalysed propargylic substitution—for the preparation of rotaxanes. The substitution reactions of a pseudorotaxane with a diverse range of heteroatom- and carbon-atom-centred nucleophiles were catalysed by the [(Cp∗)RuCl(SMe)]2 complex to furnish rotaxanes in good yields. [Copyright &y& Elsevier]

Abstract: Synthesis of [60]fullerene (C60)-functionalized rotaxanes via Diels–Alder reactions with C60 is described. Diels–Alder reaction of C60 and sulfolene moiety as masked diene attached on the wheels of rotaxanes results in high yields of C60 incorporation. Rotaxanes are prepared by tin-catalyzed urethane-forming end-capping reaction with isocyanate of pseudorotaxane having the wheel carrying C60 functionality as introduced by the Diels–Alder reaction. The Diels–Alder reaction was accomplished as end-capping reaction between C60 and pseudorotaxane bearing sultine moiety as masked diene on the axle terminal. A variety of C60-containing [2]rotaxanes was prepared in moderate to good yields by these Diels–Alder protocols. [Copyright &y& Elsevier]

Abstract: A C 1-symmetric Box macrocycle has been synthesized for the first time. The Box macrocycle along with other C 1 and C 2-symmetric Box ligands were evaluated and compared as ligands in the Cadiot–Chodkiewicz, oxidative Heck and CuAAC ‘click’ reactions as part of our studies towards achieving active-metal template synthesis of mechanically planar chiral rotaxanes. This study constitutes the first report of Cadiot–Chodkiewicz and CuAAC ‘click’ reactions using Box ligands, as well as the first dedicated study of oxidative Heck reactions using Box ligands. [Copyright &y& Elsevier]

Abstract: Based on the pillar[5]arene/alkane recognition motif, two [2]rotaxanes were successfully prepared. Their formation was confirmed by NMR spectroscopy and ESI mass spectrometry. We also demonstrated that 3,5-dinitrophenyl group and 3,5-bis(trifluoromethyl)phenyl group are big enough to work as stoppers for DPPillar[5]arene, which lays a foundation for the preparation of more complex and functional supramolecular structures. [Copyright &y& Elsevier]

Abstract: The synthesis of new [2]- and [3]rotaxanes through Sonogashira coupling has been accomplished in the aim to built oligo(phenyleneethynylene) (OPE) encircled by crown ethers. Optimization of the Sonogashira coupling for the formation of the [2]rotaxane (capping reaction) is presented and the best method has been applied for the synthesis of the longer [3]rotaxane. [Copyright &y& Elsevier]

Abstract: Diels–Alder reactions of the terminal alkyne units of SiO2-supported [2]pseudorotaxanes with 1,2,4,5-tetrazine derivatives proceed efficiently through solid-to-solid contact to provide both asymmetric and symmetric [2]rotaxanes incorporating either 24- or 25-membered-ring macrocycles. [Copyright &y& Elsevier]

Abstract: A multiple-use macrocycle recognizes dibenzylammonium ions and 2,6-lutidine derivatives, each in a [2]pseudorotaxane-like manner, through interactions with its diethylene glycol (hydrogen bonding) and 2,6-pyridinedicarboxamide (Pd2+ chelation) spacers, respectively. We characterized these complexes in the solid state (X-ray crystallography) and in solution (1H NMR spectroscopy). The synthesis of two corresponding [2]rotaxanes confirmed that these recognition systems possess [2]pseudorotaxane geometries in solution. [Copyright &y& Elsevier]

Abstract: Polymeric macromolecules are promising drug delivery devices with endocytotic properties that need to be resolved. Host-rotaxanes (HRs) also deliver materials into cells but require improved in vivo targeting capacity. Combining the targeting properties of nanoparticles with the transport function of HRs may improve drug efficacy. Our prototype HR (HR 1) has a short axle and is an efficient transporter. Here, we have constructed HRs that contain an oligo(ethylene glycol) (HR 2) or an oligoalkyl (HR 3) axle with the future goal of combining them with nanoparticles. HR 2 more efficiently delivers Fl-peptides into ovarian cancer cells than HR 3 and, in most cases, than HR 1. HR 2 appears to possess the appropriate balance between water solubility and lipophilicity to be an efficient transporter along with a suitable structure for incorporation into a larger nanoparticle. [Copyright &y& Elsevier]

Abstract: Two novel crown ethers incorporating the acridinone and the 9-phenyl-9-methoxy-acridane unit were used to form pseudorotaxanes with the 1,2-bis(4,4′dipyridinium)ethane axle, which are stoppered by the alkylative method to form rotaxanes. The pseudorotaxane formed from the acridane-containing crown was photochemically converted to the corresponding acridinium methoxide thereby releasing the guest. The acridane-containing rotaxane could not be isolated because the preparation conditions formed the acridinium salt. [Copyright &y& Elsevier]

Abstract: 1-(2-Carboxyethyl)-1′-(10-carbazole-9-yl-decyl)-4,4′-bipyridinium dibromide 2 forms a unidirectional [2]pseudorotaxane with α-cyclodextrin (α-CD) in water. Condensation of 2/α-CD [2]pseudorotaxane with 4-amino-1-naphthalenesulfonate or 6-amino-β-CD provided the unidirectional [2]rotaxanes 3 and 4, in which the secondary face of α-CD is oriented toward the viologen moiety. The structures were elucidated from two-dimensional ROESY and circular dichroism spectra. [Copyright &y& Elsevier]

During an attempt to synthesize polyrotaxanes by Wittig step-growth polymerization between a dibenzylic bis(triphenylphosphonium)-stoppered [2]rotaxane, with an NH2+ recognition site encircled by a DB24C8 ring, and appropriate derivatives of terephthaldehyde carrying bulky groups, large macrocyclic compounds with the topologies of catenanes and molecular-necklaces, are formed. [Copyright &y& Elsevier]

This paper describes the synthesis of four isomeric [2]rotaxanes and includes the first example of a salt binding [2]rotaxane with the following key observations. In polar solvents the [2]rotaxane undergoes a relatively slow co-conformational exchange that produces broad signals in the 1H NMR spectrum. Upon complexation with K+, the NMR signals sharpen apparently because the rotaxane adopts a single co-conformation. In contrast, the binding of Cl− has no effect on the rotaxane''s dynamic behavior. Although the binding of K+ induces a preorganization of the [2]rotaxane it does not change the rotaxane/Cl− association constant. The paper finishes with a discussion of the future directions of this work. [Copyright &y& Elsevier]

We have successfully synthesized novel polyurethanes where PU1 contains a [3]rotaxane that consists of N -3,5-di- tert -butylbenzyl- N -3-hydroxypropylammonium hexafluorophosphate ( AOH1 ) and N , N′ -Dimethyl- N , N′ -bis(dibenzo-24-crown-8)-terephthalamide (BisC ) as well as PU2 contains a [2]rotaxane that consists of AOH1 and dibenzo-24-crown-8 ether. Diphenylmethanediisocyanate (MDI), 1,4-butanediol (BD) and poly( ε -caprolactone)diol (PCL) were used as an isocyanate, chain expander, and soft segment, respectively. A polyurethane without any rotaxane structures (PU0) were also prepared as a reference polymer. The existence of the rotaxanes in the polyurethanes was confirmed by 1 H NMR spectroscopy and TGA measurement. ATR-FT-IR spectral measurement revealed that the rotaxanes disturb the formation of hydrogen bonding between the polyurethane chains. From the DSC result, the rotaxanes retard the recrystallization of the PCL unit whereas no influence on the glass transition temperatures of the polyurethanes was observed. The retarding effect appeared remarkably with PU1. These thermal behaviors of the polyurethanes were also supported by viscoelastic measurement. In tensile test, the tensile strength and break of strain of PU1 were larger than those of PU2. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel photo-responsive pseudorotaxanes employing three different hetero-macrocycles combination, α-cyclodextrin (α-CD), cucurbit[7]uril (CB[7]) and p-sulfonatocalix[4]arene (SC4), as hosts were obtained. The shuttling of α-CD on the dumbbell can be reversibly driven by alternating irradiation with different lights. 1H NMR, 2D NOSEY experiments, and MALDI-TOF MS measurement are used to demonstrate the formation of the pseudorotaxanes. UV–vis absorption and induced circular dichroism measurements were carried out to illustrate the reversible photo-responsive properties of the pseudorotaxanes as well. [Copyright &y& Elsevier]