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This review explores calixarenes, a prominent family of third-generation supramolecules celebrated for their distinct hollow, cavity-shaped structures. These macrocycles are intricately assembled by linking multiple phenolic units orthogonally through methylene (–CH2–), sulfur (–S–), or sulfonyl (–SO2–) bridges. This structural framework plays a pivotal role in the intricate assembly of nanoclusters, significantly advancing the field of cluster chemistry. A key focus of current research is the remarkable ability of calixarenes to stabilize titanium-oxo clusters. Our review details the application of calixarenes in constructing titanium-oxo cluster structures, emphasizing how these clusters, when encapsulated within calixarenes, exploit flexible coordination sites for structural modifications and serve as foundational units for more complex assemblies. Additionally, we investigate how these calixarene-stabilized metal-oxo clusters function as versatile scaffolds for catalytically active metal ions, facilitating the creation of bimetallic nanoclusters. These clusters not only exhibit unique structural diversity but also demonstrate exceptional catalytic efficiency. This review aims to inspire ongoing exploration and innovation in the use of calixarenes for the synthesis and application of advanced cluster materials. [ABSTRACT FROM AUTHOR]

Calixarenes are reportedly excellent activators that can remarkably improve the transport efficiencies of cell penetrating peptides. We employed eight calixarenes to systematically study the influence of structure on activation efficiency, which revealed that the scaffold, head group, and alkyl chain are all significant factors for activation efficiency by affecting affinities with the peptide and membrane. [ABSTRACT FROM AUTHOR]

Calix[6]arene (CX6) was found to be an efficient ion transmembrane channel, which could be blocked by methylene blue (MB) through host–guest interactions. The blocked CX6 channel could be reopened by 4-sulfonated calix[6]arene owing to its stronger affinity with MB, thereby achieving a reversible ON–OFF–ON type switch. [ABSTRACT FROM AUTHOR]

Methyl carbonate ionic liquids are shown to readily mono-deprotonate p-tert-butylcalix-[4]-arenes initiating the formation of an organic mono-anionic p-tert-butylcalix-[4]-arate salt, methanol and carbon dioxide. These calix-[4]-arate salts have been successfully used in alkylation reactions with dialkyl sulfates and alkyl halides to form a mono-alkylated single product with high yield. This method avoids the common use of alkali metal bases such as caesium fluoride hence providing a safer and more selective synthetic route. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An unprecedented meso-decorated pillar[5]arene derivative, EtP5A-DPE, embedded with a TPE unit was prepared and structurally characterized. In the crystal, the incubation of the guest 1,4-dicyanobutane molecule inside the tetraphenylethene-embedded pillar scaffold induces a significant change in the molecular conformation, shutting down the AIE emission of this compound. [ABSTRACT FROM AUTHOR]

The morphologies of an azobenzene-bridged biscalix[4]arene organogel in different organic solvents can be photo-reversibly switched between nanofibers and nanorings as well as between closed and open-form vesicles. [ABSTRACT FROM AUTHOR]

The synthesis of high surface-area colloidal assemblies of calixarene-phosphine-capped nanoporous gold is reported under reductive electrochemical conditions. These materials uniquely exhibit a remarkably thin wall thickness down to 10 nm, while possessing pore sizes on the order of up to hundreds of nanometers, which can be controlled via choice of organic ligand. [ABSTRACT FROM AUTHOR]

Herein, an unprecedented monomeric bowl-like coordination complex, Ti12PgC3 (PgC3 = C-propylpyrogallol[4]arene), has been successfully synthesized. To the best of our knowledge, Ti12PgC3 not only presents the first pyrogallol[4]arene-based titanium coordination complex, but also the highest nuclearity titanium coordination complex in the metal–calixarene system. In addition, this titanium coordination complex can effectively degrade the methylene blue (MB) dye under sunlight. [ABSTRACT FROM AUTHOR]

Two calix[6]arene-based molecular containers were synthesized in high yields. These containers can encapsulate small guests through a unique “rotating door” complexation process. The sequestration of greenhouse gases is clearly demonstrated. They can be stored in the solid state for long periods and released via dissolution of the inclusion complex. [ABSTRACT FROM AUTHOR]

Host–guest recognition plays an important role in biological analysis and biosensing. Accordingly, great efforts have been devoted to the development of sensors using versatile 3D surface materials. These functionalized nanomaterials possess the advantages of high selectivity and visual signals, enabling the selective detection of ions, amino acids, proteins, and other biological molecules. Therefore, in this feature article, we present some significant and representative examples of molecular recognition on calixarene functionalized 3D surface nanomaterials. By virtue of host–guest interactions, the functional interfaces displaying high selectivity and featuring a reversible switch response towards the environmental stimuli with various signal output (electrochemical and optical signals) are herein introduced. Furthermore, various 3D surface materials with unique signal amplification in molecular recognition are presented, including quantum dots (QDs), metal nanoparticles (NPs), nanotubes, and mesoporous silica. These excellent properties enable calixarene-functionalized 3D materials to become an outstanding platform for molecular recognition, offering convenient approaches for sensing and separation. [ABSTRACT FROM AUTHOR]

A 3D supramolecular polymer based on calix[5]arene tethered poly(p-phenyleneethynylene) with a complementary porphyrin endowed with alkanediyldiammonium functions is prepared in solution but collapses when transferred to a chemically inert solid matrix forming a dispersion of de-phasing porphyrin aggregates. We found that a short thermal shock induces the de-aggregation of the porphyrin aggregates, and a partial restoration of the original 3D-supramolecular architecture. [ABSTRACT FROM AUTHOR]

We present two approaches to low-molecular-weight supramolecular gels bearing hydrophobic cavities based on calixarene-containing building blocks. Gels are formed by a calixarene based tetrahydrazide gelator or a co-gel of a calixarene diammonium salt and a bis-crown ether. The calixarene hydrophobic cavity enables the complexation of hydrophobic drug molecules in a generic fashion thus providing an anchor site on the surface of the gel fibre to initiate drug crystal nucleation and growth. This technique potentially represents a route to growth of hard-to-nucleate polymorphic modifications. The co-gel comprising two components holding together by non-covalent ammonium-crown ether interaction can be easily switched back to the sol state by adding competitive binding cations. [ABSTRACT FROM AUTHOR]

Molecular switch systems, having been extensively studied in the solution phase, have the ability to perform with good controllability and rapid-responsiveness, making them ideally suited for the design of molecular devices for drug delivery, and information or sensing functions. Inspired by a wide range of objects with visual changes, like Mimosa pudica towards external stimuli, in order to understand molecular switches well, they must be interfaced with the macroscopic world so that they can be directly realized by visual detectable changes even observed by the naked eye. This can be critical for fabricating intelligent microfluidics and laboratory-on-chip devices, that may have wide applications in the fields of biology and materials science. But to realize this objective, especially for fabricating macroscopic surface switches, unveiling host–guest weak interactions to achieve visual phenomena is still the greatest thrill. Thankfully, surface contact angles provide us with a wonderful method to further investigate the microscopic origin of the macroscopic changes. Therefore, interfacial modification becomes a paramount process. Macrocyclic compounds, encompassing an innovative concept to deal with reversible noncovalent interactions between macrocyclic hosts and suitable guests, are good candidates for surface functionalization. In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications. [ABSTRACT FROM AUTHOR]

A mixture of heterotrinuclear lanthanide cluster complexes, Tb3−xYbxTCAS2 (x = 1, 2), was obtained by mixing thiacalix[4]arene-p-tetrasulfonate (TCAS), TbIII, and YbIII, which shows enhanced YbIII-centred luminescence and shortened lifetime for TbIII-centred luminescence as compared to Yb3TCAS2 and Tb3TCAS2, indicating f–f communication, i.e., energy transfer from TbIII to YbIII. [ABSTRACT FROM AUTHOR]

A dynamic vesicle was constructed by the complexation of (dodecyloxybenzyl)tripropargylammonium and p-sulfonatocalix[4]arene, then the dynamic vesicle was cross-linked by a “click” reaction. The cross-linked vesicle presents improved stability over the dynamic one. Meanwhile, it can be disrupted with specific chemical stimuli to give the controlled release. [ABSTRACT FROM AUTHOR]

After their successful use as a preorganized platform for the preparation of receptors for metal ions and small neutral molecules over the last 15 years, calixarenes are enjoying a renaissance of popularity as scaffolds for ligands that are able to efficiently and selectively target macromolecules such as proteins/enzymes, nucleic acids and lipids. This feature article summarizes the peculiar factors characterizing the calixarene structure and properties, as well as outlines the main rules that can be used to turn such macrocycles into efficient and successful ligands for these classes of biomacromolecules. Factors that affect the multivalent properties of calixarenes, such as the size, conformation and stereochemical presentation of binding groups or their amphiphilicity and hybrid character, are described in detail with the use of a few selected examples from the literature. Perspectives and applications of these ligands in bionanotechnology and nanomedicine, such as protein sensing and inhibition, gene-delivery, targeted drug-delivery and cell imaging, are also discussed. [ABSTRACT FROM AUTHOR]

The structure of the C60 and p-But-calix[8]arene complex has been reinvestigated, showing an unprecedented continuous layered tetragonal array of fullerenes encapsulated by calixarenes. Electron diffraction data revealed the tetragonal symmetry, with a stepped structure observed by AFM and SEM, and the thickness of the basal plane was measured by XRD, as 2 nm. The molecular simulated arrangement of fullerenes accounts for the ability to take up to ca. 11% of fullerenes C70 in place of the smaller fullerene. [ABSTRACT FROM AUTHOR]

Direct disubstitution at the methylene bridges of p-tert-butylcalix[6]arenemethyl ether has been achieved for the first time using a lithiation–substitution protocol. Two stable conformers have been isolated using column chromatography, and their structures have been unambiguously confirmed from 1D, 2D and variable temperature NMR studies and single crystal X-ray structure analysis. [ABSTRACT FROM AUTHOR]

A unique host–guest recognition process involving a new class of homoditopic CMPO-pillar[5]arenes and lanthanides was revealed to proceed in a stepwise manner, and correlated with the efficient separation of americium(iii) and europium(iii) under acidic feed conditions. [ABSTRACT FROM AUTHOR]

We describe the active template effect of a calix[6]arene host towards the alkylation of a complexed pyridylpyridinium guest. The acceleration of the reaction within the cavity is significant and rim-selective, enabling the efficient preparation of rotaxanes with full control of the mutual orientation of their nonsymmetric components. [ABSTRACT FROM AUTHOR]

A crystal structure of lysozyme in complex with p-sulfonato-calix[4]-arene (sclx4) reveals a linear assembly of protein tetramers glued together by protein-calixarene interactions. One interaction involves encapsulation of the highly exposed C-terminal Arg128. The other involves an intricate protein-bound complex of sclx4, Mg2+ and a fragment of polyethylene glycol. [ABSTRACT FROM AUTHOR]

Stable core-shell nanospheres self-assemble in water from heterodimers combining a hydrophobic calix[4]arene moiety and a hydrophilic ß-cyclodextrin head; their potential to encapsulate and provide sustained release of the anticancer drug docetaxel and undergo surface post-modification with glycoligands targeting the macrophage mannose receptor is discussed. [ABSTRACT FROM AUTHOR]

The outstanding cation complexation properties emerging from the pioneering studies on calixarene ligands during a five-year period in the early 1980s triggered a big-bang burst of publications on such macrocycles that is still lasting at a distance of more than 30 years. A time-lapse photography of this timeframe is proposed which allows the readers to pinpoint the contributions of the different research groups. [ABSTRACT FROM AUTHOR]

The 1979 X-ray crystal structure of the p-t-butylcalix[4]arene toluene 1 : 1 intra-cavity inclusion complex proved a landmark result that established the iconic calixarene shape, proved the tetrameric calixarene structure and showed that an intrinsic molecular cavity in an artificial receptor could contain a guest molecule. [ABSTRACT FROM AUTHOR]

p-Phosphonic acid calix[n]arenes and their O-alkylated lower rim analogues are remarkably versatile macrocycles, with applications in selective diameter uptake of single walled carbon nano-tubes, as surfactants in stabilising and protecting nano-particles and graphene sheets, as crystal growth modifiers for inorganic systems, in encapsulating molecules of anti-cancer carboplatin, self assembly into nano-arrays, including nano-fibres and molecular capsules, and for binding metal ions including biologically relevant Ca2+. They are readily accessible viafive or six high yielding steps from the parent p-Butsubstituted compounds. [ABSTRACT FROM AUTHOR]

Herein, we reported a new strategy based on self-assembly chemistry for chiral discrimination of glucose on a new S-mandelic acid-appended calix[4]arene (S-MC4) modified nanostructure, which exhibits macroscopic chiral preference for d-glucose via contact angle measurements (CA). The proposed macroscopic chiral device displays rapidly remarkable specificity and is convenient to use, which should be suitable for diagnostic purposes, nanomedical applications, etc. [ABSTRACT FROM AUTHOR]

Among all crystalline complexes of calix-type calix[n]arenes those with organic molecules which are biologically relevant are especially of interest due to their potential medical and pharmaceutical applications. The co-crystallization of drugs with water-soluble calixarenes offers the opportunity to modify chemical and physical properties of APIs (active pharmaceutical ingredients) and to control drug conformation. Such co-crystallization can improve solubility, bioavailability and stability of pharmaceutically active molecules and/or eliminate polymorphism. In this article the solid-state interactions between calixarene hosts and biologically relevant guest molecules are summarized for the currently available structures solved by single-crystal X-ray crystallography. [ABSTRACT FROM AUTHOR]

This feature article is a timely review of a portion of the authors' work concerning the chemistry of dendrimers and subsequent related fluorescent probes. The design of supramolecular systems provides an original approach to nanoscience and nanochemistry. The construction of well-defined functional architectures of nanometric size represents a way of performing programmed engineering of nanomaterials. Among the nanomaterials, dendrimers are set apart, and very recently a large number of works have been devoted to the elaboration of molecular sensors. These two aspects will be developed in this article from the authors' experience with calixarenes. [ABSTRACT FROM AUTHOR]

This feature article is a timely review of a portion of the authors’ work concerning the chemistry of dendrimers and subsequent related fluorescent probes. The design of supramolecular systems provides an original approach to nanoscience and nanochemistry. The construction of well-defined functional architectures of nanometric size represents a way of performing programmed engineering of nanomaterials. Among the nanomaterials, dendrimers are set apart, and very recently a large number of works have been devoted to the elaboration of molecular sensors. These two aspects will be developed in this article from the authors’ experience with calixarenes. [ABSTRACT FROM AUTHOR]

Heterocalixaromatics, the heteroatom bridged calix(hetero)arenes, have been emerging as new generation macrocyclic host molecules in supramolecular chemistry recently. Being different from the conventional calixarenes in which the aromatic rings are linked by methylene units, heterocalixaromatics assemble various aromatic rings by different heteroatoms. Owning to the intrinsic nature of heteroatoms that can adopt different electronic configurations to form various degrees of conjugation with their neighboring aromatic rings, heterocalixaromatics exhibit unique structural features and versatile recognition properties in comparison to conventional calixarenes. This feature article highlights recent advances in the synthesis, functionalization, structure and molecular recognition of nitrogen- and/or oxygen-bridged calixaromatics, with a primary focus on our own work. [ABSTRACT FROM AUTHOR]

We present a new molecular shuttle, consisting of a calixarene core attached to two different photoactive centers, DCM and DMABN. We show that a K+ ion bound to the DCM-grafted crown is translocated towards the other site of the molecule upon photoexcitation, but not released to the bulk. [ABSTRACT FROM AUTHOR]

A calixarene-based supramolecular hydrogel with a porous network structure was successfully constructed via a hierarchical induced assembly strategy, showing reversible or irreversible gelation behaviors in response to several external stimuli including thermal, redox and ionic strength. [ABSTRACT FROM AUTHOR]