Triphenylamine[3]arenes: Streamlining Synthesis of a Versatile Macrocyclic Platform for Supramolecular Architectures and Functionalities

Triphenylamine[3]arenes (TPA[3]s), featuring [16]paracyclophane backbone with alternating carbon and nitrogen bridging atoms, were synthesized through a BF3 ⋅ Et2O-catalyzed cyclization reaction using triphenylamine derivatized monomers and paraformaldehyde. This molecular design yielded a series of TPA[3] macrocycles with high efficiency, with their facile derivatizations also successfully demonstrated. On account of the strong electron-donating properties of the TPA moieties, these TPA[3]s exhibit remarkable delayed fluorescence, and possess a significant affinity for iodine. Furthermore, their inherent three-fold symmetry rendered TPA[3]s as novel building blocks for the construction of extended frameworks and molecular cages. This advancement expands the versatility of discrete macrocycles into complex architectures, enhancing their applicability across a broad spectrum of applications.

Isoreticular Covalent Organic Pillars: Engineered Nanotubular Hosts for Tailored Molecular Recognition

In the realm of nanoscale materials design, achieving precise control over the dimensions of nanotubular architectures poses a substantial challenge. In our ongoing pursuit, we have successfully engineered a novel class of single-molecule nanotubes─isoreticular covalent organic pillars (iCOPs)─by stacking formylated macrocycles through multiple dynamic covalent imine bonds, guided by principles of reticular chemistry. Our strategic selection of rigid diamine linkers has facilitated the synthesis of a diverse array of iCOPs, each retaining a homologous structure yet offering distinct cavity shapes influenced by the linker choice. Notably, three of these iCOP variants feature continuous one-dimensional channels, exhibiting length-dependent host-guest interactions with α,ω-dibromoalkanes, and each presenting a distinct critical guest alkyl chain length threshold for efficient guest encapsulation. This newfound capability not only provides a platform for tailoring nanotubular structures with precision, but also opens new avenues for innovative applications in molecular recognition and the purification of complex mixtures.

Solid-State Self-Assembly: Exclusive Formation and Dynamic Interconversion of Discrete Cyclic Assemblies Based on Molecular Tweezers

In contrast to self-assembly in solution systems, the construction of well-defined assemblies in the solid state has long been identified as a challenging task. Herein, we report the formation of tweezers-shaped molecules into various assemblies through a solid-state self-assembly strategy. The relatively flexible molecular tweezers undergo exclusive and quantitative assembly into either cyclic hexamers or a porous network through classical recrystallization or the exposure of powders to solvent vapor, despite the fact that they form only dimers in solution. The cyclic hexamers have high thermal stability and exhibit moderate solid-state fluorescence. The formation of heterologous assemblies consisting of different tweezers allows for tuning these solid-state properties of the cyclic hexamer. Furthermore, (trimethylsilyl)ethynyl-substituted tweezers demonstrate solvent-vapor-induced dynamic interconversion between the cyclic hexamer and a pseudocyclic dimer in the solid state. This assembly behavior, which has been studied extensively in solution-based supramolecular chemistry, had not been accomplished in the solid state so far.

Window[1]resorcin[3]arenes: A Novel Macrocycle Able to Self-Assemble to a Catalytically Active Hexameric Cage

The hexameric resorcin[4]arene capsule has been utilized as one of the most versatile supramolecular capsule catalysts. Enlarging its size would enable expansion of the substrate size scope. However, no larger catalytically active versions have been reported. Herein, we introduce a novel class of macrocycles, named window[1]resorcin[3]arene (wRS), that assemble to a cage-like hexameric host. The new host was studied by NMR, encapsulation experiments, and molecular dynamics simulations. The cage is able to bind tetraalkylammonium ions that are too large for encapsulation inside the hexameric resorcin[4]arene capsule. Most importantly, it retained its catalytic activity, and the accelerated conversion of a large substrate that does not fit the closed hexameric resorcin[4]arene capsule was observed. Thus, it will help to expand the limited substrate size scope of the closed hexameric resorcin[4]arene capsule.

Solid-State Emissive Pillar[6]arene Derivative Having Alternate Methylene and Nitrogen Bridges

Macrocyclic arenes show conformational adaptability, which allows host-guest complexations with the size-matched guest molecules. However, their emission properties are often poor in the solid states due to the self-absorption. Herein, we newly synthesized pillar[6]arene derivatives having alternate methylene and nitrogen bridging structures. Solvatochromic study reveals that the nitrogen-embedding into the cyclic structures can strengthen the intramolecular charge transfer (CT) nature compared to that of the linear nitrogen-bridged precursor. Owing to the large Stokes shift in the solid state, one of the nitrogen-embedded pillar[6]arenes shows high absolute photoluminescence quantum yield (ΦPL=0.36). Furthermore, it displays a turn-off sensing ability toward nitrobenzene (NB) vapor; a fluorescence quenching is observed when exposed to the NB vapor. From the structural analysis before and after the exposure of NB vapor, the amorphous nitrogen-embedded pillar[6]arene efficiently co-crystallize with NB and formed non-emissive intermolecular CT complexes with NB.

Supramolecular Synthesis of Star Polymers

Supramolecular polymers, in which monomers are assembled via intermolecular interactions, have been extensively studied. The fusion of supramolecular polymers with conventional polymers has attracted the attention of many researchers. In this review article, the recent progress in the construction of supramolecular star polymers, including regular star polymers and miktoarm star polymers, is discussed. The initial sections briefly provide an overview of the conventional classification and synthesis methods for star polymers. Coordination-driven self-assembly was investigated for the supramolecular synthesis of star polymers. Star polymers with multiple polymer chains radiating from metal-organic polyhedra (MOPs) have also been described. Particular focus has been placed on the synthesis of star polymers featuring supramolecular cores formed through hydrogen-bonding-directed self-assembly. After describing the synthesis of star polymers based on host-guest complexes, the construction of miktoarm star polymers based on the molecular recognition of coordination capsules is detailed.

Cyclotribenzylene alkynylgold(I) phosphine complexes: synthesis, chirality, and exchange of phosphine

Two different alkynyl-substituted C3-symmetric cyclotribenzylenes (CTB) were synthesized in racemic and enantiomerically pure forms, and six gold(I) phosphine complexes differing by the nature of the CTB and the phosphine were prepared and characterized, in particular by NMR spectroscopy, DOSY, electronic circular dichroism (ECD), and electrospray ionization mass spectrometry (ESI-MS). Their ECD patterns depended on the substitution of the starting CTBs and were shifted bathochromically by comparison with the latter. ESI-MS in the presence of HCO2H allowed us to detect the complexes as proton adducts. The intensities of the signals were stronger when the phosphine was more electron-rich. This technique was also used to investigate the exchange of phosphine betweeen pairs of CTB complexes. The scrambling reaction was demonstrated by the higher intensity of the signals of the complexes subjected to the exchange of a single phosphine ligand by comparison with the intensity of the signals of the starting complexes.

Dual-controlled guest release from coordination cages

Despite having significant applications in the construction of controlled delivery systems with high anti-interference capability, to our knowledge dual-controlled molecular release has not yet been achieved based on small molecular/supramolecular entities. Herein, we report a dual-controlled release system based on coordination cages, for which releasing the guest from the cage demands synchronously altering the coordinative metal cations and the solvent. The cages, Hg5L2 and Ag5L2, are constructed via coordination-driven self-assembly of a corannulene-based ligand. While Hg5L2 shows a solvent-independent guest encapsulation in all the studied solvents, Ag5L2 is able to encapsulate the guests in only some of the solvents, such as acetone-d6, but will liberate the encapsulated guests in 1,1,2,2-tetrachloroethane-d2. Hg5L2 and Ag5L2 are interconvertible. Thus, the release of guests from Hg5L2 in acetone-d6 can be achieved, but requires two separate operations, including metal substitutions and a change of the solvent. Dual-controlled systems as such could be useful in complicated molecular release process to avoid those undesired stimulus-responses.

Silapillar[n]arenes: Their Enhanced Electronic Conjugation and Conformational Versatility

During recent decades, methylene-bridged macrocyclic arenes have been widely used in supramolecular chemistry. However, their π-conjugations are very weak, as the methylene bridges disrupt the electronic communication between π orbitals of the aromatic units. Herein, we successfully synthesized a series of silapillar[n]arenes (n = 4, 6, and 8) using silylene bridging. These showed enhanced electronic conjugation compared with the parent pillar[n]arenes because of σ*-π* conjugation between σ* (Si-C) orbitals and π* orbitals of the benzenes. Owing to the longer Si-C bond compared with the C-C bond, silylene-bridging provides additional structural flexibility into the pillar[n]arene scaffolds; a strained silapillar[4]arene was formed, which is unavailable in the parent pillar[n]arenes because of the steric requirements. Furthermore, silapillar[n]arenes displayed interesting size-dependent structural and optical properties.

Encapsulation in Charged Droplets Generates Distorted Host-Guest Complexes

The ability of various hydrogen-bonded resorcinarene-based capsules to bind α,ω-alkylbisDABCOnium (DnD) guests of different lengths was investigated in solution and in the gas-phase. While no host-guest interactions were detected in solution, encapsulation could be achieved in the charged droplets formed during electrospray ionisation (ESI). This included guests, which are far too long in their most stable conformation to fit inside the cavity of the capsules. A combination of three mass spectrometric techniques, namely, collision-induced dissociation, hydrogen/deuterium exchange, and ion-mobility mass spectrometry, together with computational modelling allow us to determine the binding mode of the DnD guests inside the cavity of the capsules. Significant distortions of the guest into horseshoe-like arrangements are required to optimise cation-π interactions with the host, which also adopt distorted geometries with partially open hydrogen-bonding seams when binding longer guests. Such quasi "spring-loaded" capsules can form in the charged droplets during the ESI process as there is no competition between guest encapsulation and ion pair formation with the counterions that preclude encapsulation in solution. The encapsulation complexes are sufficiently stable in the gas-phase - even when strained - because non-covalent interactions significantly strengthen in the absence of solvent.

Leveraging Torsional and Steric Strains: A Pre-macrocyclization Strategy Enables Conformation-Specific Fullerene Binding in m-Cyclophanes

Though the chemistry of resorcinarenes is half a century old, the conformationally-locked resorcinarene crowns are generally constructed using hydrogen bonds or covalent tethers. Often, covalent tethering involves extra post-macrocyclization steps involving upper-rim functionalities. We have leveraged the torsional and steric strains through α-substituents of the lower-rim C-alkyl chains and accomplished conformationally-rigid fluorescent m-cyclophane deep-crowns in a predetermined way. The strategy offers a pre-macrocyclization route conserving upper-rim functionalities, an aspect overlooked in resorcinarene chemistry. X-ray structural and computational analyses unveil the cause for conformational rigidity in m-cyclophanes due to α-branching in C-alkyls (linear vs. α-/β-branched). The conformationally-locked fluorescent deep-crown with a preorganized cavity captures hydrophobic spherical guest C60 in both solution and solid states specifically, when compared to conformationally-dynamic boats, enabling conformation-specific binding.

Shape-Persistent Triptycene-Derived Pillar[6]arenes: Synthesis, Host-Guest Complexation, and Enantioselective Recognitions of Chiral Ammonium Salts

Construction of macrocyclic hosts with a novel structure and excellent property has emerged as an intriguing undertaking for the past few years. Here, we reported the synthesis of shape-persistent triptycene-derived pillar[6]arene (TP[6]). The single crystal structure analysis revealed that the macrocyclic molecule adopts a hexagonal structure, featuring a helical and electron-rich cavity capable of encapsulating electron-deficient guests. In order to obtain chiral TP[6] from an enantiomerically pure triptycene building block, an efficient resolution of chiral triptycene was successfully developed through introducing chiral auxiliaries into triptycene skeletons. The ¹H NMR and isothermal titration calorimetry investigations demonstrated that chiral TP[6] exhibited enantioselectivity toward four pairs of chiral guests containing a trimethylamino group, implying a significant promising application in area of enantioselective recognition.

Homo- and Heteromultinuclear Pseudocapsules Assembled from Calix[6]-mono-crown-5 and Alkali Metal Ions

The formation of pseudocapsule type homo- and heteromultinuclear complexes of calix[6]-mono-crown-5 (H₄L) encapsulating from 4 to 6 alkali metal ions is reported. H₄L reacts with KOH to yield a hexanuclear potassium(I) complex [K₆(HL)₂(CH₃OH)₂]·CHCl₃ (1) in which two bowl-shaped tripotassium(I) complex units are linked in a rim-to-rim fashion via the interligand C-H···π interactions. In the same reaction condition, RbOH afforded a tetranuclear rubidium(I) complex [Rb₄(H₂L)₂(CH₃OH)₂(μ-H₂O)₂]·6CHCl₃ (2). In 2, again two bowl-shaped dirubidium(I) complex units are held together by two bridging water molecules and C-H···π interactions that act as a glue to generate such an elegant pseudocapsule. Interestingly, a mixture of KOH and RbOH yielded a heterotetranuclear complex [K₂Rb₂(H₂L)₂(CH₃OH)₂(μ-H₂O)₂]·6CHCl₃ (3). Similarly, two heterodinuclear bowl units [KRb(H₂L)] in 3 are held together by two bridging water molecules and C-H···π interactions to form a heteromultinuclear pseudocapsule. In each heterodinuclear K⁺/Rb⁺ bowl unit of 3, Rb⁺ occupies the center of the crown loop while K⁺ locates inside the calix rim. Consequently, the proposed host discriminates not only on the types and numbers of the metal ions but also on their positional preferences in forming pseudocapsules. Solution studies by nuclear magnetic resonance and electrospray ionization-mass support the heterometallic (K⁺/Rb⁺) complexation by showing the superior binding affinity of Rb⁺ over K⁺ toward the crown loop. These results demonstrate how the metal-driven pseudocapsules are formed and present a new perspective on the metallosupramolecules of the calixcrown scaffold.

Noncovalent tailoring of coordination complexes by resorcin[4]arene-based supramolecular hosts

Molecular recognition of guest molecules in a confined cavity is one of the important phenomena in biological and artificial molecular systems. When the guest is trapped within an artificial nano-space, its conformation is fixed in an unusual fashion by noncovalent interactions with host frameworks, and also the guest is kept away from the bulk solvent by the steric effect of the host. Therefore, host-guest formations lead to the effective modulation of the chemical and physical properties of guests via noncovalent interactions. In contrast to the many examples of organic guests, the examples of host-guest formation using coordination complex guests have been less explored. This is simply due to the size and shape complementarity problem between small hosts and large coordination complex guests. Resorcin[4]arene-based supramolecular hosts have been shown to provide internal cavities that are large enough to fully accommodate coordination complexes within the internal spaces via effective molecular interactions. In this article, we focus on supramolecular strategies to control the chemical and physical properties of the coordination complex guests within resorcin[4]arene-based supramolecular hosts. By the careful selection of the host and guest complexes, these combinations can produce a new supramolecular system, showing unusual structures, redox, catalytic, and photophysical properties derived from the entrapped coordination complexes.

Macrocycle with Equatorial Coordination Sites Provides New Opportunity for Structure-Diverse Metallacages

Reported here is the synthesis of a macrocycle with equatorial coordination sites for the construction of self-assembled metallacages. The macrocycle is prepared via a post-modification on the equator of biphen[n]arene. Utilizing this macrocycle as a ligand, three prismatic cages and one octahedral cage were synthesized by regulating the geometric structures and coordination number of metal acceptors. The multi-cavity configuration of prismatic cage was revealed by single-crystal structure. We prove that a macrocycle with equatorial coordination sites can be an excellent building block for synthesizing structure-diverse metallacages. Our results provide a typical example and a general method for the design and synthesis of metallacages.

Anion-Directed Self-Assembly of Calix[4]arene-Based Silver(I) Coordination Polymers and Photocatalytic Degradation of Organic Pollutants

Coordination polymers (CPs) have recently emerged as promising candidates for heterogeneous photocatalysis due to their structural designability and tunable properties. Herein, we developed two novel Ag(I)-calix[4]arene coordination polymers with the formula {[Ag₂(μ-NO₃)L¹]}_n (CP 1) and {[AgL¹]·PF₆}_n (CP 2) (L¹ = 2-mercapto-5-methyl-1,3,4-thiadiazole resorcinol calix[4]arene). Crystallography revealed that anion coordination and self-inclusion behavior induced the cavitand and silver ions to self-assemble into well-defined CPs 1 and 2 with different topological coordination frameworks, respectively. Furthermore, CPs 1 and 2 display high photocatalytic activity for the photodegradation of rhodamine B (RhB) and methyl orange (MO) in an aqueous solution under mild conditions (WLED and UV irradiation). The comparison results demonstrate that CP 1 exhibited better photocatalytic performance than CP 2, which correlated well with the differences in their molecular structure and HOMO-LUMO energy gaps. The photocatalysis products and possible intermediates were successfully monitored and determined using mass spectrum, gas chromatography, and electron paramagnetic resonance measurements. The rational photocatalysis mechanism was further investigated and proposed.

Megalo-Cavitands: Synthesis of Acridane[4]arenes and Formation of Large, Deep Cavitands for Selective C70 Uptake

Deep cavitands, concave molecular containers, represent an important supramolecular host class that has been explored for a variety of applications ranging from sensing, switching, purification and adsorption to catalysis. A major limitation in the field has been the cavitand volume that is restricted by the size of the structural platform utilized (diameter approx. 7 Å). We here report the synthesis of a novel, unprecedentedly large structural platform, named acridane[4]arene (diameter approx. 14 Å), suitable for the construction of cavitands with volumes of up to 814 ų . These megalo-cavitands serve as size-selective hosts for fullerenes with mM to sub-μM binding affinity for C₆₀ and C₇₀ . Furthermore, the selective binding of fullerene C₇₀ in the presence of C₆₀ was demonstrated.

Organo-macrocycle-containing hierarchical metal-organic frameworks and cages: design, structures, and applications

Developing hierarchical ordered systems is challenging. Using organo-macrocycles to construct metal-organic frameworks (MOFs) and porous coordination cages (PCCs) provides an efficient way to obtain hierarchical assemblies. Macrocycles, such as crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, can be incorporated within MOFs/PCCs and they also endow the resultant composites with enhanced properties and functionalities. This review summarizes recent developments of organo-macrocycle-containing hierarchical MOFs/PCCs, emphasizing applications and structure-property relationships of these hierarchically porous materials. This review provides insights for future research on hierarchical self-assembly using macrocycles as building blocks and functional ligands to extend the applications of the composites.

Purely Covalent Molecular Cages and Containers for Guest Encapsulation

Cage compounds offer unique binding pockets similar to enzyme-binding sites, which can be customized in terms of size, shape, and functional groups to point toward the cavity and many other parameters. Different synthetic strategies have been developed to create a toolkit of methods that allow preparing tailor-made organic cages for a number of distinct applications, such as gas separation, molecular recognition, molecular encapsulation, hosts for catalysis, etc. These examples show the versatility and high selectivity that can be achieved using cages, which is impossible by employing other molecular systems. This review explores the progress made in the field of fully organic molecular cages and containers by focusing on the properties of the cavity and their application to encapsulate guests.

An electron-deficient supramolecular macrocyclic host for the selective separation of aromatics and cyclic aliphatics

Host 1 with an electron-deficient nanometer-sized cavity were synthesized in two steps. Moreover, 1 has been successfully used as a gas chromatographic stationary phase to prepare a packed column for the separation of PhH/Cy and Tol/MCy.

Two Giant Calixarene-Like Polyoxoniobate Nanocups {Cu12 Nb120 } and {Cd16 Nb128 } Built from Mixed Macrocyclic Cluster Motifs

Cup-shaped molecules are of great interest due to their appealing architectures and properties. Compared with widely studied calixarenes, polyoxometalate-based cup-shaped molecules currently remain a virgin land waiting for exploration. In this work, we report the first discovery of two giant cup-shaped inorganic-organic hybrid polyoxoniobates (PONbs) of {Cu₁₂ Nb₁₂₀ } and {Cd₁₆ Nb₁₂₈ }. The former integrates three tricyclic Nb₂₄ clusters and a hexacyclic Nb₄₈ cluster into a cup-shaped molecule via a Cu₁₂ metallacalixarene, while the latter unifies two tricyclic Nb₂₄ clusters and a brand-new pentacyclic Nb₄₀ cluster into another cup-shaped molecule via a hybrid Cd₁₆ unit. With 132 and 144 metal centers, {Cu₁₂ Nb₁₂₀ } and {Cd₁₆ Nb₁₂₈ } show the largest two inorganic-organic hybrid PONbs known to date.

Metal-dependent selective formation of calix[4]arene assemblies based on dynamic covalent chemistry

The reaction of calix[4]arene derivatives 1a and 1b bearing four salicylaldehyde moieties with 1,3-propanediamine gave macrocyclic trimers 5a and 5b, respectively, which have intramolecular bridges formed via the flattened cone conformation. In contrast, a capsular-shaped dimeric cage [7a·2Na]²⁺ was selectively formed when the conformation of the calix[4]arene moiety of 1a was fixed in the spread cone conformation by complexation with Na⁺ at the lower-rim amide groups.

Xanthene[n]arenes: Exceptionally Large, Bowl-Shaped Macrocyclic Building Blocks Suitable for Self-Assembly

A new class of macrocycles denoted as "xanthene[n]arenes" was synthesized. In contrast to most other macrocycles, they feature a conformationally restricted bowl shape due to the attached alkyl groups at the linking methylene units. This facilitates the synthesis of cavitands and the self-assembly to molecular capsules via noncovalent interactions. The derivatization potential of the novel macrocycles was demonstrated on the xanthene[3]arene scaffold. Besides a deep cavitand and an oxygen-embedded zigzag hydrocarbon belt[12]arene, a modified macrocycle was synthesized that self-assembles into a hydrogen-bonded tetrameric capsule, demonstrating the potential of xanthene[n]arenes as a new set of macrocyclic building blocks.

Catalysis in Single Crystalline Materials: From Discrete Molecules to Metal-Organic Frameworks

Catalysis is one of the key techniques for people's modern life. It has created numerous essential chemicals such as biomedicines, agricultural chemicals and unique materials. Heterogeneous catalysis is the new emerging method with reusable catalysts. Among heterogenous catalysis patterns developed so far, single crystalline catalysis has become the promising one owing to its high catalytic density and selectivity resulted by the inherent porosity, orderliness of the lattices and permeability. These crystalline catalysts could be used in various reactions such as photo-dimerization, Diels-Alder reaction, CO₂ transformation and so on. In this review, we highlighted the reported works about the single crystalline catalysts. Both discrete small molecules and metal-organic frameworks (MOFs) have been used to prepare single crystals for catalysis. For discrete molecules based crystalline catalysts, coordinated and covalent molecules have been used. There were more catalytic modes in crystalline MOF catalysts. Three patterns were identified in this review: single crystalline MOFs i) without catalytic sites, ii) with inherent catalytic features and iii) with introducing catalytic units by post synthetic modification. Based on these examples, this review committed to provide the inspirations for the further design and application of single crystalline materials.

Resorcinarene-Based Supramolecular Capsules: Supramolecular Functions and Applications

A resorcinarene is a synthetic macrocycle consisting of four resorcinol molecules covalently linked by methylene bridges. The interannular bridges produce a cavitand that has a bowl-shaped structure. We have developed supramolecular capsules through Ag(I) or Cu(I) coordination-driven self-assembly of cavitands possessing 2,2′-bipyridyl arms in their upper rims. The self-assembled capsules accommodate various molecular guests and supramolecular assemblies possessing acetoxy groups. The host–guest chemistry of the molecular capsules has been applied in the fabrication of supramolecular polymers. This account describes recent developments in the supramolecular chemistry of resorcinarene-based coordination capsules and provides a brief history of resorcinarene-based capsules and related capsules.

Water-stable hydrazone-linked porous organic cages

Although porous organic cages (POCs), particularly imine-linked (C[double bond, length as m-dash]N) ones, have advanced significantly over the last few decades, the reversible nature of imine linkages makes them prone to hydrolysis and structural collapse, severely limiting their applications under moist or water conditions. Herein, seven water-stable hydrazone-linked (C[double bond, length as m-dash]N-N) POCs are prepared through a simple coupling of the same supramolecular tetraformylresorcin[4]arene cavitand with different dihydrazide linkers. Their structures are all determined by single-crystal X-ray crystallography, demonstrating rich structural diversity from the [2 + 4] lantern, [3 + 6] triangular prism, and unprecedented [4 + 8] square prism to the extra-large [6 + 12] octahedron. In addition, they respectively exhibit tunable window diameters and cavity volumes ranging from about 5.4 to 11.1 nm and 580 to 6800 ų. Moreover, their application in the water environment for pollutant removal was explored, indicating that they can effectively eliminate various types of contaminants from water, including radionuclide waste, toxic heavy metal ions, and organic micropollutants. This work demonstrates a convenient method for rationally constructing versatile robust POCs and presents their great application potentialities in water medium.

Thioderivatives of Resorcin[4]arene and Pyrogallol[4]arene: Are Thiols Tolerated in the Self-Assembly Process?

Three novel thiol bearing resorcin[4]arene and pyrogallol[4]arene derivatives were synthesized. Their properties were studied with regards to self-assembly, disulfide chemistry, and Brønsted acid catalysis. This work demonstrates that (1) one aromatic thiol on the resorcin[4]arene framework is tolerated in the self-assembly process to a hexameric hydrogen bond-based capsule, (2) thio-derivatized resorcin[4]arene analogs can be covalently linked through disulfides, and (3) the increased acidity of aromatic thio-substituent is not sufficient to replace HCl as cocatalyst for capsule catalyzed terpene cyclizations.

Negative Cooperativity in Guest Binding of a Ditopic Self-Folding Biscavitand

A brand-new self-folding biscavitand was synthesized from a feet-to-feet-connected bisresorcinarene. The X-ray crystal structure of the biscaivtand showed that the two cavities are tightly connected with four butylene linkages. The conformationally coupled two cavities accommodated two cationic guests, showing a homotropic negative cooperativity in nonpolar solvents (toluene and chloroform). A polar tetrahydrofuran solvent weakened the cyclic hydrogen bonding interactions of the biscavitand, which resulted in noncooperative guest binding.

Efficient ethylene purification by a robust ethane-trapping porous organic cage

The removal of ethane (C₂H₆) from its analogous ethylene (C₂H₄) is of paramount importance in the petrochemical industry, but highly challenging due to their similar physicochemical properties. The use of emerging porous organic cage (POC) materials for C₂H₆/C₂H₄ separation is still in its infancy. Here, we report the benchmark example of a truncated octahedral calix[4]resorcinarene-based POC adsorbent (CPOC-301), preferring to adsorb C₂H₆ than C₂H₄, and thus can be used as a robust absorbent to directly separate high-purity C₂H₄ from the C₂H₆/C₂H₄ mixture. Molecular modelling studies suggest the exceptional C₂H₆ selectivity is due to the suitable resorcin[4]arene cavities in CPOC-301, which form more multiple C–H···π hydrogen bonds with C₂H₆ than with C₂H₄ guests. This work provides a fresh avenue to utilize POC materials for highly selective separation of industrially important hydrocarbons.

The removal of ethane from ethylene is of importance in the petrochemical industry, but similar physicochemical properties of these molecules makes separation a challenging task. Here, the authors demonstrate that a robust octahedral calix[4]resorcinarene-based porous organic cage can separate high-purity ethylene from ethane/ethylene mixtures.

Solvatomorphism Influence of Porous Organic Cage on C2H2/CO2 Separation

Porous organic molecular (POM) materials can exhibit solvatomorphs via altering their crystallographic packing in the solid state, but investigating real gas mixture separation by porous materials with such a behavior is still very rare. Herein, we report that a lantern-shaped calix[4]resorcinarene-based porous organic cage (POC, namely, CPOC-101) can exhibit eight distinct solid-state solvatomorphs via crystallization in different solvents. This POC solvatomorphism has a significant influence on their gas sorption capacities as well as separation abilities. Specifically, the apparent Brunauer-Emmett-Teller (BET) surface area determined by nitrogen gas sorption at 77 K for CPOC-101α crystallized from toluene/chloroform is up to 406 m² g^-1, which is much higher than the rest of CPOC-101 solvatomorphs with BET values less than 40 m² g^-1. More interestingly, C₂H₂ and CO₂ adsorbed capacities, in addition to the C₂H₂/CO₂ separation ability at room temperature for CPOC-101α, are superior to those of CPOC-101β crystalized from nitrobenzene, the representative of POC solvatomorphs with low BET surface areas. These results indicate the possibility of adjusting gas sorption and separation properties of POC materials by controlling their solvatomorphs.

Three Resorcin[4]arene-Based Two-Dimensional Zn(II) Supramolecular Isomers Synthesized via a Structure-Directing Strategy for Knoevenagel Condensation

Herein, in the presence of three structure-directing agents (SDAs), a family of imidazole-functionalized resorcin[4]arene-based coordination polymers (CPs), [Zn(TIC4R)(HCOO)]·HCOO·0.5DMF·1.5H₂O (1), [Zn(TIC4R)(CN)]·HCOO·DMF·2.5H₂O (2), and [Zn(TIC4R)(H₂O)]·2HCOO·2H₂O (3), were assembled under solvothermal conditions [TIC4R = tetra(imidazole) resorcin[4]arene]. 1 exhibits a double-layer structure with rectangle windows, and 2 and 3 display monolayer structures. The layers of CPs 2 and 3 are slides with different offsets along the a-axis. In addition, three CPs were used as catalysts to catalyze Knoevenagel condensations. Strikingly, all CPs exhibit remarkable catalytic performance for several substrates. To the best of our knowledge, this is the first time that a small organic acid as SDA was used in the syntheses of resorcin[4]arene-based supramolecular isomers.

Phase-Dependent Reactivity and Host-Guest Behaviors of a Metallo-Macrocycle in Liquid and Solid-State Photosensitized Oxygenation Reactions

The photochemical oxygenation reactions of a host-guest complex, pCp⊂[Ag₂L0](SbF₆)₂ (pCp = [2.2]paracyclophane) have been investigated in solution and in the solid state, using the macrocyclic ligand L0 having four anthracene moieties in the framework. As a result, it was found that the reactivity and host-guest functions show remarkable phase dependence. In solution, the photosensitized oxygenation of all the anthracene moieties of L0 resulted in a fully oxygenated macrocycle [Ag₂L4](SbF₆)₂ as the final product, while simultaneously the guest molecule was dissociated from the macrocyclic cavity. On the other hand, in an amorphous solid of pCp⊂[Ag₂L0](SbF₆)₂ prepared by decomposing single crystals through the removal of the crystalline solvent, the oxygenated site of L0 was significantly controlled to provide a site-selectively oxygenated inclusion complex, pCp⊂[Ag₂L1](SbF₆)₂, possessing a mono-oxygenated C_s-symmetrical macrocyclic skeleton.

Concentration-Dependent Self-Assembly of an Unusually Large Hexameric Hydrogen-Bonded Molecular Cage

The sizes of available self-assembled hydrogen-bond-based supramolecular capsules and cages are rather limited. The largest systems have volumes of approximately 1400-2300 ų . Herein, we report a large, hexameric cage based on intermolecular amide-amide dimerization. The unusual structure with openings, reminiscent of covalently linked cages, is held together by 24 hydrogen bonds. With a diameter of 2.3 nm and a cavity volume of ∼2800 ų , the assembly is larger than any previously known capsule/cage structure relying exclusively on hydrogen bonds. The self-assembly process in chlorinated, organic solvents was found to be strongly concentration dependent, with the monomeric form prevailing at low concentrations. Additionally, the formation of host-guest complexes with fullerenes (C₆₀ and C₇₀ ) was observed.