Synthesis of novel pillar-shaped cavitands “Pillar[5]arenes” and their application for supramolecular materials

Chalcogen Bond-Driven Alkylations: Selenoxide-Pillar[5]arene as a Recyclable Catalyst for Displacement Reactions in Water

A novel strategy to catalyze alkylation reactions through chalcogen bond interaction using a supramolecular structure is presented herein. Utilizing just 1.0 mol % of selenoxide-pillar[5]arene (P[5]SeO) as the catalyst we achieved efficient catalysis in the cyanation of benzyl bromide in water. Our approach demonstrated high efficiency and effectiveness, with the results supported by designed control experiments and theoretical models, highlighting the catalytic effect of the pillar[5]arene through noncovalent interactions. Quantum-chemical calculations (ωB97X-D/def2-TZVP@SMD) pointed out that the catalyzed cyanation reaction followed an SN2-like mechanism, with energy barriers (ΔH≠) ranging from 16.7 to 18.2 kcal mol-1, exhibiting dissociative character depending on the para-substituent. 1H NMR analysis revealed that P[5]SeO acted as a catalyst through inclusion complex formation, facilitating the transfer of the electrophilic substrate to the aqueous solution for nucleophilic displacement. Our reaction protocol proved applicable to various substrates, including aromatic and alpha-carbonyl derivatives. The use of sodium azide as the nucleophile was also feasible. Importantly, our method allowed scalability, and the catalyst P[5]SeO could be recovered and reused effectively for multiple reaction cycles, showcasing sustainability.

Temperature-Dependent Left- and Right-Twisted Conformational Changes in 1 : 1 Host-Guest Systems: Theoretical Modeling and Chiroptical Simulations

An efficient strategy for high-performance chiral materials is to design and synthesize host molecules with left- and right- (M- and P-)twisted conformations and to control their twisted conformations. For this, a quantitative analysis is required to describe the chiroptical inversion, chiral transfer, and chiral recognition in the host-guest systems, which is generally performed using circular dichroism (CD) and/or proton nuclear magnetic resonance (1H NMR) spectroscopies. However, the mass-balance model that considers the M- and P-twisted conformations has not yet been established. In this study, we derived the novel equations based on the mass-balance model for the 1 : 1 host-guest systems. Then, we further applied them to analyze the 1 : 1 host-guest systems for the achiral calixarene-based capsule molecule, achiral dimeric zinc porphyrin tweezer molecule, and chiral pillar[5]arene with the chiral and/or achiral guest molecules by using the data obtained from the CD titration, variable temperature CD (VT-CD), and 1H NMR experiments. The thermodynamic parameters (ΔH and ΔS), equilibrium constants (K), and molar CD (Δϵ) in the 1 : 1 host-guest systems could be successfully determined by the theoretical analyses using the derived equations.

Halogen bonding BODIPY-appended pillar[5]arene for the optical sensing of dicarboxylates and a chemical warfare agent simulant

A pillar[5]arene host, functionalised with halogen bonding (XB) recognition sites and BODIPY fluorophores, demonstrates strong binding and optical sensing of environmentally relevant dicarboxylates and a chemical warfare agent simulant, in organic and competitive aqueous-organic media - enabled by the unprecedented combination of fluorophore-conjugated XB interactions with the hydrophobic pillar[5]arene host cavity.

Telluride-Based Pillar[5]arene: A Recyclable Catalyst for Alkylation Reactions in Aqueous Solution

The syntheses of previously unknown sulfide- and telluride-pillar[n]arenes are reported here. These macrocycles, among others, were tested as catalysts for alkylation reactions in aqueous solutions. Telluride-pillar[5]arene (P[5]-TePh) showed the best performance, emulating the behavior of the methyltransferase enzyme cofactor S-adenosyl-l-methionine. Using 1.0 mol % of P[5]-TePh, benzyl bromides reacted with NaCN/NaN3 in water, yielding organic nitriles/azides. The catalyst was recycled and efficiently reused for up to six cycles. 1H NMR experiments indicate a possible interaction between the substrate and P[5]-TePh's cavity.

2D and 3D Self-Assembly of Fluorine-Free Pillar-[5]-Arenes and Perfluorinated Diacids at All-Aqueous Interfaces

The interaction of perfluorinated molecules, also known as "forever chemicals" due to their pervasiveness, with their environment remains an important yet poorly understood topic. In this work, the self-assembly of perfluorinated molecules with multivalent hosts, pillar-[5]-arenes, is investigated. It is found that perfluoroalkyl diacids and pillar-[5]-arenes rapidly and strongly complex with each other at aqueous interfaces, forming solid interfacially templated films. Their complexation is shown to be driven primarily by fluorophilic aggregation and assisted by electrostatic interactions, as supported by the crystal structure of the complexes, and leads to the formation of quasi-2D phase-separated films. This self-assembly process can be further manipulated using aqueous two-phase system microdroplets, enabling the controlled formation of 3D micro-scaffolds.

Molecular vessels from preorganised natural building blocks

Supramolecular vessels emerged as tools to mimic and better understand compartmentalisation, a central aspect of living matter. However, many more applications that go beyond those initial goals have been documented in recent years, including new sensory systems, artificial transmembrane transporters, catalysis, and targeted drug or gene delivery. Peptides, carbohydrates, nucleobases, and steroids bear great potential as building blocks for the construction of supramolecular vessels, possessing complexity that is still difficult to attain with synthetic methods - they are rich in functional groups and well-defined stereogenic centers, ready for noncovalent interactions and further functions. One of the options to tame the functional and dynamic complexity of natural building blocks is to place them at spatially designed positions using synthetic scaffolds. In this review, we summarise the historical and recent advances in the construction of molecular-sized vessels by the strategy that couples synthetic predictability and durability of various scaffolds (cyclodextrins, porphyrins, crown ethers, calix[n]arenes, resorcin[n]arenes, pillar[n]arenes, cyclotriveratrylenes, coordination frameworks and multivalent high-symmetry molecules) with functionality originating from natural building blocks to obtain nanocontainers, cages, capsules, cavitands, carcerands or coordination cages by covalent chemistry, self-assembly, or dynamic covalent chemistry with the ultimate goal to apply them in sensing, transport, or catalysis.

Kinetically controlled synthesis of rotaxane geometric isomers

Geometric isomerism in mechanically interlocked systems-which arises when the axle of a mechanically interlocked molecule is oriented, and the macrocyclic component is facially dissymmetric-can provide enhanced functionality for directional transport and polymerization catalysis. We now introduce a kinetically controlled strategy to control geometric isomerism in [2]rotaxanes. Our synthesis provides the major geometric isomer with high selectivity, broadening synthetic access to such interlocked structures. Starting from a readily accessible [2]rotaxane with a symmetrical axle, one of the two stoppers is activated selectively for stopper exchange by the substituents on the ring component. High selectivities are achieved in these reactions, based on coupling the selective formation reactions leading to the major products with inversely selective depletion reactions for the minor products. Specifically, in our reaction system, the desired (major) product forms faster in the first step, while the undesired (minor) product subsequently reacts away faster in the second step. Quantitative 1H NMR data, fit to a detailed kinetic model, demonstrates that this effect (which is conceptually closely related to minor enantiomer recycling and related processes) can significantly improve the intrinsic selectivity of the reactions. Our results serve as proof of principle for how multiple selective reaction steps can work together to enhance the stereoselectivity of synthetic processes forming complex mechanically interlocked molecules.

Rapid Access to Chiral and Tripodal Cavitands from β-Pinene

We report Pd-catalyzed cyclotrimerization of (+)-α-bromoenone, obtained from monoterpene β-pinene, into an enantiopure cyclotrimer. This C3 symmetric compound has three bicyclo[3.1.1]heptane rings fused to its central benzene with each ring carrying a carbonyl group. The cyclotrimer undergoes diastereoselective threefold alkynylation with the lithium salts of five terminal alkynes (41-63 %, de=4-83 %). The addition enabled a rapid synthesis of a small library of novel chiral cavitands that, in shape, resemble a tripod stand. These molecular tripods include a tris-bicycloannelated benzene head attached to three alkyne legs twisted in one direction to form a nonpolar cavity with polar groups as feet. Tripods with methylpyridinium and methylisoquinolinium legs, respectively, form inclusion complexes with anti-inflammatory and chiral drugs (R)/(S)-ibuprofen and (R)/(S)-naproxen. The mode of binding shows drug molecules docked in the cavity of the host through ion-ion, cation-π, and C-H-π contacts that, in addition of desolvation, give rise to complexes having millimolar to micromolar stability in water. Our findings open the door to creating a myriad of enantiopure tripods with tunable functions that, in the future, might give novel chemosensors, catalysts or sequestering agents.

Synthesis of Novel Cavitand Host Molecules via Palladium-Catalyzed Aryloxy- and Azidocarbonylation

Novel, elongated, resorcine[4]arene-based cavitands were synthesized via various consecutive reaction steps, including homogeneous catalytic aryloxy- and azidocarbonylation processes. The effects of carbon monoxide pressure and temperature on the conversion were examined in aryloxycarbonylation. It was revealed that a reaction temperature of 100 °C is required to achieve complete conversion both with monodentate (PPh₃) and bidentate (Xantphos) phosphines at different carbon monoxide pressures (1-40 bar). Using ten different phenols as O-nucleophiles, partial hydrolysis of the esters to the corresponding carboxylic acids took place-i.e., 58-90% chemoselectivities toward esters were obtained. Moreover, the influences of temperature, reaction time and the catalyst ratio on the selectivity and conversion were described in the case of azidocarbonylation reaction. The formation of the acyl azide with high chemoselevtivity can be achieved at room temperature only. The higher reaction temperatures (50 °C) and higher catalyst loadings favor the formation of the primary amide. The characterization of the target compounds (esters and acyl azides) was carried out by IR and ¹H and ¹3C NMR. The discussion of the influences of various parameters is based on in situ NMR investigations.

Mechanically interlocked polymers based on rotaxanes

The nature of mechanically interlocked molecules (MIMs) has continued to encourage researchers to design and construct a variety of high-performance materials. Introducing mechanically interlocked structures into polymers has led to novel polymeric materials, called mechanically interlocked polymers (MIPs). Rotaxane-based MIPs are an important class, where the mechanically interlocked characteristic retains a high degree of structural freedom and mobility of their components, such as the rotation and sliding motions of rotaxane units. Therefore, these MIP materials are known to possess a unique set of properties, including mechanical robustness, adaptability and responsiveness, which endow them with potential applications in many emerging fields, such as protective materials, intelligent actuators, and mechanisorption. In this review, we outline the synthetic strategies, structure-property relationships, and application explorations of various polyrotaxanes, including linear polyrotaxanes, polyrotaxane networks, and rotaxane dendrimers.

Copillar[5]arene Chemistry: Synthesis and Applications

Research on pillar[n]arenes has witnessed a very quick expansion. This emerging class of functionalized macrocyclic oligoarenes not only offers host–guest properties due to the presence of the central cavity, but also presents a wide variety of covalent functionalization possibilities. This short review focuses on copillararenes, a subfamily of pillar[n]arenes. In copillararenes, at least one of the hydroquinone units bears different functional groups compared to the others. After having defined the particular features of copillararenes, this short review compares the different synthetic strategies allowing their construction. Some key applications and future perspectives are also described.

1 Introduction

2 General Features of Pillar[5]arenes

3 Synthesis of Functionalized Copillar[4+1]arenes

4 Concluding Remarks

Supramolecular systems prepared using terpyridine-containing pillararene

Recent progresses about the preparation of terpyridine-containing pillararene, as well as the utilization of those building blocks for making external stimulud-responsive supramolecular systems were summarized in this review.

Dendritic-Like Molecules Built on a Pillar[5]arene Core as Hole Transporting Materials for Perovskite Solar Cells

Multi-branched molecules have recently demonstrated interesting behaviour as charge-transporting materials within the fields of perovskite solar cells (PSCs). For this reason, extended triarylamine dendrons have been grafted onto a pillar[5]arene core to generate dendrimer-like compounds, which have been used as hole-transporting materials (HTMs) for PSCs. The performances of the solar cells containing these novel compounds have been extensively investigated. Interestingly, a positive dendritic effect has been evidenced as the hole transporting properties are improved when going from the first to the second-generation compound. The stability of the devices based on the best performing pillar[5]arene material has been also evaluated in a high-throughput ageing setup for 500 h at high temperature. When compared to reference devices prepared from spiro-OMeTAD, the behaviour is similar. An analysis of the economic advantages arising from the use of the pillar[5]arene-based material revealed however that our pillar[5]arene-based material is cheaper than the reference.

Visualization and quantitation of electronic communication pathways in a series of redox-active pillar[6]arene-based macrocycles

While oxidized pillar[5]arenes with 1-5 benzoquinone units are known, very few examples of oxidized pillar[6]arenes have been reported. We describe here the synthesis, characterization and electrochemical behavior of a series of macrocyclic hosts prepared by the stepwise oxidation of 1,4-diethoxypillar[6]arene, resulting in high-yield and high-purity isolation of two constitutional isomers for each macrocycle, in which two, three or four 1,4-diethoxybenzene units are replaced by benzoquinone residues. A careful structural comparison with their counterparts in the pillar[5]arene framework indicates that the geometries of the macrocycles are better described as non-Euclidean hyperbolic hexagons and elliptic pentagons, respectively. A comprehensive computational study to determine anisotropic induced current density (ACID) allows us to visualize and quantify through-space and through-bond communication pathways along the macrocyclic belt. Experimental and simulated voltammetric data, as well as UV-vis spectra, of the new macrocycles afford insights into the various electronic communication pathways in these compounds.

Diversity Oriented Preparation of Pillar[5]arene-Containing [2]Rotaxanes by a Stopper Exchange Strategy

Rotaxane building blocks bearing 3,5-bis(trifluoromethyl) benzenesulfonate (BTBS) stoppers have been efficiently prepared from a pillar[5]arene derivative, 3,5-bis(trifluoromethyl) benzenesulfonyl chloride (BTBSCl) and different diols, namely 1,10-decanediol and 1,12-dodecanediol. The BTBS moieties of these compounds are good leaving groups and stopper exchange reactions could be achieved by treatment with different nucleophiles thus affording rotaxanes with ester, thioether or ether stoppers.

Radiation stability of phosphine oxide functionalized pillar[5]arenes

The radiation stability of three phosphine oxide functionalized pillar[5]arenes (POP5A) was studied by an electron accelerator with dose up to 5 MGy in air at room temperature. The structures of both irradiated and unirradiated pillar[5]arenes samples were comparatively characterized by Micro-FTIR, NMR, UV-vis, ESI-HRMS and HPLC techniques. The results revealed different degrees of radiation damage at different doses for POP5A, and the degradation products are mainly composed of organic species containing hydroxyl groups and carbonyl groups. The possible radiolytic degradation pathway was proposed. In addition, extraction of uranyl ion with irradiated POP5A samples was examined. The distribution ratio of uranyl ion was found to increase at low radiation dose and decrease until 3000 kGy. This is the first time that the irradiation stability of pillar[5]arenes derivative extractants has been studied in detail and it provides reliable data support for further application of pillar[5]arenes extractants in practical applications.

Pillararenes as macrocyclic hosts: a rising star in metal ion separation

Pillararenes are macrocyclic oligomers of alkoxybenzene akin to calixarenes but tethered at the 2,5-positions via methylene bridges. Benefiting from their unique pillar-shaped architecture favorable for diverse functionalization and versatile host-guest properties, pillararenes decorated with chelating groups worked excellently as supporting platforms to construct extractants or adsorbents for metal ion separation. This feature article provides a detailed summary of pillararenes in Ln/An separation by liquid-liquid extraction and heavy metal separation by solid-liquid extraction. The preorganization effect of the rigid pillararene framework has a profound impact on the extraction of metal ions, and a unique extraction mechanism is observed when employing ionic liquids as solvents. The rich host-guest chemistry of pillararenes enables construction of a wide variety of supramolecular materials as metal ion adsorbents. We also discuss the differences between pillararenes and several well-known macrocycles, with a focus on the metal-ligand coordination and its influencing factors. We hope this review will provide useful information and unleash new opportunities in this field.

Recent developments in the construction of metallacycle/metallacage-cored supramolecular polymers via hierarchical self-assembly

Supramolecular polymers have received considerable attention during the last few decades due to their scientific value in polymer chemistry and profound implications for future developments of advanced materials. Discrete supramolecular coordination complexes (SCCs) with well-defined size, shape, and geometry have been widely employed to construct hierarchical systems by coordination-driven self-assembly with the spontaneous formation of metal-ligand bonds, which results in the formation of well-defined two-dimensional (2D) metallacycles or three-dimensional (3D) metallacages with high functionalities. The incorporation of discrete SCCs into supramolecular polymers by the orthogonal combination of metal-ligand coordination and other noncovalent interactions or covalent bonding could further facilitate the construction of novel supramolecular polymers with hierarchical architectures and multiple functions including controllable uptake and release of guest molecules, providing a flexible platform for the development of smart materials. In this review, the recent progress in metallacycle/metallacage-cored supramolecular polymers that were constructed by the combination of metal-ligand interactions and other orthogonal interactions (including hydrophobic or hydrophilic interactions, hydrogen bonding, van der Waals forces, π-π stacking, electrostatic interactions, host-guest interactions and covalent bonding) has been discussed. In addition, the potential applications of metallacycle/metallacage-cored supramolecular polymers in the areas of light emitting, sensing, bio-imaging, delivery and release, etc., are also presented.

Pillararene-based self-assembled amphiphiles

Pillararenes are a unique group of supramolecular macrocycles, presenting important features and potential applications on account of their intrinsic structural properties and functionality. Developing pillararene-based self-assembled amphiphiles (PSAs) is an efficient approach to translate pillararenes into functional systems and materials for facilitating their practical applications. In this review article, we highlight recent significant advancements in PSAs. A new standard according to the number, solubility, and amphiphilicity of building blocks is employed for dividing PSAs into different categories. The fabrication of PSAs based on various building blocks and supramolecular interactions, and the formation of amphiphile-based self-assemblies are then discussed based on this standard. Furthermore, interesting stimulus-responsiveness to various factors, such as pH, redox, temperature, light, ionic effect, and host-guest competition, generated by the functional groups on various building blocks is summarized, and the corresponding supramolecular interactions in PSAs and their self-assemblies are elaborated. In addition, some important applications of PSAs and their assemblies are discussed. This review not only provides fundamental findings on the construction of PSAs, but also foresees future research directions in this rapidly developing area.

Bowl-in-bowl complex formation with mixed sized calixarenes: adaptivity towards guest binding

We demonstrated the organization of two differently sized calixarenes C-methylresorcin[4]arene (RsC1) and either calix[6]arene (Calix6) or calix[8]arene (Calix8), where the lower rim of RsC1 partially overlaps with the upper rim of Calix6 or Calix8. An adaptive nature of the heteromacrocyclic assembly towards the binding of a model guest has been observed.

Biological and related applications of pillar[n]arenes

Pillar[n]arenes are a new class of synthetic supramolecular macrocycles streamlined by their particular pillar-shaped architecture which consists of an electron-rich cavity and two fine-tuneable rims. The ease and diversity of the functionalization of the two rims open possibilities for the design of new architectures, topological isomers, and scaffolds. Significantly, this emerging class of macrocyclic receptors offers a unique platform for biological purposes. This review article covers the most recent contributions from the pillar[n]arene field in terms of artificial membrane transport systems, controlled drug delivery systems, biomedical imaging, biosensors, cell adhesion, fluorescent sensing, and pesticide detection based on host-guest interactions. The review also uniquely describes the properties of sub-units that make pillar[n]arenes suitable for biological applications and it provides a detailed outline for the design of new innovative pillar-like structures with specific properties to open up a new avenue for pillar[n]arene chemistry.

Supramolecular chemistry of pillar[n]arenes functionalised by a copper(i)-catalysed alkyne-azide cycloaddition "click" reaction

Since we discovered pillar[n]arenes in 2008, many chemists have developed a strong interest in pillar[n]arene chemistry because of the many advantages associated with these materials, including their facile and high yielding synthesis, versatile functionality, planar chirality and unique host-guest properties. In this feature article, we discuss recent advances in the field of supramolecular chemistry based on the use of pillar[n]arenes as substrates for copper(i)-catalysed alkyne-azide cycloaddition (CuAAC) "click" chemistry. The CuAAC reaction provides facile access to 1,4-disubstituted triazoles by a reaction between alkyne and azido substrates in the presence of a Cu(i) catalyst. Pillar[n]arenes bearing alkyne or azido groups can therefore be used as substrates for this reaction. Herein, we discuss not only the synthesis of pillar[n]arenes bearing alkyne or azido groups but also the application of these functionalised systems to the CuAAC reaction to construct supramolecular assemblies. We also discuss the rational molecular design and synthesis of guest compounds using the CuAAC reaction because linear alkanes sandwiched between 1,2,3-triazole moieties are good guests for cyclic pentamer pillar[5]arenes.

A Rotaxane Scaffold for the Construction of Multiporphyrinic Light-Harvesting Devices

A sophisticated photoactive molecular device has been prepared by combining recent concepts for the preparation of multifunctional nanomolecules (click chemistry on multifunctional scaffolds) with supramolecular chemistry (self-assembly to prepare rotaxanes). Specifically, a clickable [2]rotaxane scaffold incorporating a free-base porphyrin stopper has been prepared and functionalized with ten peripheral Zn(II)-porphyrin moieties. Electrochemical investigations of the final compound revealed a peculiar behavior resulting from the intramolecular coordination of the Zn(II) porphyrin moieties to 1,2,3-triazole units. Finally, steady state investigations of the compound combining Zn(II) and free-base porphyrin moieties have shown that this compound is a light-harvesting device capable of channeling the light energy from the peripheral Zn(II)-porphyrin subunits to the core by singlet-singlet energy transfer.

Preparation of Pillar[5]arene-Based [2]Rotaxanes by a Stopper-Exchange Strategy

A pillar[5]arene-containing rotaxane building block bearing exchangeable stoppers has been prepared in multigram scale quantities with high yields from the reaction of 2,4-dinitrophenol (DNP) with the inclusion complex resulting from the association of dodecanedioyl chloride with 1,4-diethoxypillar[5]arene. Stopper exchange reactions have been achieved by treatment of the resulting DNP diester with various amines through an addition-elimination mechanism preventing the unthreading of the axle component during the reaction and thus preserving the [2]rotaxane structures. The resulting diamide [2]rotaxane derivatives have thus been obtained in good to excellent yields. Importantly, [2]rotaxanes difficult or impossible to prepare by direct introduction of the two stoppers in a single synthetic step are now easily available.

Coordination-Driven Folding in Multi-ZnII -Porphyrin Arrays Constructed on a Pillar[5]arene Scaffold

Pillar[5]arene derivatives bearing peripheral porphyrin subunits have been efficiently prepared from a deca-azide pillar[5]arene building block (17) and Zn^II -porphyrin derivatives bearing a terminal alkyne function (9 and 16). For the resulting deca-Zn^II -porphyrin arrays (18 and 20), variable temperature NMR studies revealed an intramolecular complexation of the peripheral Zn^II -porphyrin moieties by 1,2,3-triazole subunits. As a result, the molecules adopt a folded conformation. This was further confirmed by UV/Vis spectroscopy and cyclic voltammetry. In addition, we have also demonstrated that the coordination-driven unfolding of 18 and 20 can be controlled by an external chemical stimulus. Specifically, addition of an imidazole derivative (22) to solution of 18 or 20 breaks the intramolecular coordination at the origin of the folding. The resulting molecular motions triggered by the addition of the imidazole ligand mimic the blooming of a flower.

Dual-Responsive Bola-Type Supra-Amphiphile Constructed from Water-Soluble Pillar[5]arene and Naphthalimide-Containing Amphiphile for Intracellular Drug Delivery

Supramolecular construction of multistimuli platform for drug delivery is a challenging task. In this work, a pH and GSH (glutathione) dual-responsive bola-type supramolecular amphiphile was successfully fabricated by the complexation between a water-soluble pillar[5]arene (WP5) and a bolaform naphthalimide guest (G) in water. The resulting bola-type amphiphile further self-assembled into supramolecular binary vesicles, which could be disassembled by low pH, a high-GSH-concentration environment, or both. Furthermore, the results of drug loading and releasing tests showed that doxorubicin (DOX), the hydrophobic anticancer drug, could be successfully encapsulated into the Stern region of the obtained supramolecular vesicles and generated the DOX-loaded vesicles with good drug-loading efficiency. Moreover, the obtained DOX-loaded vesicles displayed efficient and rapid DOX release at a simulated tumor microenvironment with low-pH or excess-GSH conditions or both. Significantly, cytotoxicity experiments revealed that the DOX-loaded supramolecular vesicles could obviously improve the anticancer efficiency of free DOX for tumor cells while remarkably reducing its side effects for normal cells. In vitro cellular uptake and subcellular localization assays further proved that these smart drug nanovehicles, entering cancer cells mainly via endocytosis, could cause excellent drug accumulation in cancer cells. The present study provides a successful example with which to rational design an effective bola-type stimuli-responsive supramolecular nanocarrier, which might have wide potential applications in the construction of various controlled drug-delivery systems.