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Improving the slow redox kinetics of sulfur species and shuttling issues of soluble intermediates induced from the multiphase sulfur redox reactions are crucial factors for developing the next‐generation high‐energy‐density lithium‐sulfur (Li−S) batteries. In this study, we successfully constructed a novel molecular electrocatalyst through in situ polymerization of bis(3,4‐dibromobenzene)‐18‐crown‐6 (BD18C6) with polysulfide anions on the cathode interface. The crown ether (CE)‐based polymer acts as a spatial "fence" to precisely control the unique redox characteristics of sulfur species, which could confine sulfur substance within its interior and interact with lithium polysulfides (LiPSs) to optimize the reaction barrier of sulfur species. The "fence" structure and the double‐sided Li+ penetrability of the CE molecule may also prevent the CE catalytic sites from being covered by sulfur during cycling. This new fence‐type electrocatalyst mitigates the "shuttle effect", enhances the redox activity of sulfur species, and promotes the formation of three‐dimensional stacked lithium sulfide (Li2S) simultaneously. It thus enables lithium‐sulfur batteries to exhibit superior rate performance and cycle stability, which may also inspire development facing analogous multiphase electrochemical energy‐efficient conversion process. [ABSTRACT FROM AUTHOR]

Crown ethers (CEs), known for their exceptional host–guest complexation, offer potential as linkers in covalent organic frameworks (COFs) for enhanced performance in catalysis and host–guest binding. However, their highly flexible conformation and low symmetry limit the diversity of CE‐derived COFs. Here, we introduce a novel C3‐symmetrical azacrown ether (ACE) building block, tris(pyrido)[18]crown‐6 (TPy18C6), for COF fabrication (ACE‐COF‐1 and ACE‐COF‐2) via reticular synthesis. This approach enables precise integration of CEs into COFs, enhancing Ni2+ ion immobilization while maintaining crystallinity. The resulting Ni2+‐doped COFs (Ni@ACE‐COF‐1 and Ni@ACE‐COF‐2) exhibit high discharge capacity (up to 1.27 mAh ⋅ cm−2 at 8 mA ⋅ cm−2) and exceptional cycling stability (>1000 cycles) as cathode materials in aqueous alkaline nickel‐zinc batteries. This study serves as an exemplar of the seamless integration of macrocyclic chemistry and reticular chemistry, laying the groundwork for extending the macrocyclic‐synthon driven strategy to a diverse array of COF building blocks, ultimately yielding advanced materials tailored for specific applications. [ABSTRACT FROM AUTHOR]

Lithium‐oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next‐generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor life, which lay a significant gap between laboratory research and commercial applications. In this work, we adopt 15‐crown‐5 ether (C15) as solvent to regulate the generation of discharge products in lithium‐oxygen batteries. The coronal structure endows C15 with strong affinity to Li+, firmly stabilizes the intermediate LiO2 and discharge product Li2O2. Thus, the crystalline Li2O2 is amorphized into easily decomposable amorphous products. The lithium‐oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm−2 to 5.7 mAh cm−2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm−2. The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li2O2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li2O2 amorphization and reduce charge overpotential in lithium‐oxygen batteries. [ABSTRACT FROM AUTHOR]

Precise control of substrate positioning and orientation (its proximity to the reactive unit) is often invoked to rationalize the superior enzymatic reaction rates and selectivities when compared to synthetic models. Artificial nonheme iron (IV) oxo (Fe(IV)=O) complexes react with C(sp3)−H bonds via a biomimetic Hydrogen Atom Transfer/Hydroxyl Rebound mechanism, but rates, site‐selectivity and even hydroxyl rebound efficiency (ligand rebound versus substrate radical diffusion) are smaller than in oxygenases. Herein, we quantitatively analyze how substrate binding modulates nonheme Fe(IV)=O reactivity by comparing rates and outcomes of C−H oxidation by a pair of Fe(IV)=O complexes that share the same first coordination sphere but only one contains a crown ether receptor that recognizes the substrate. Substrate binding makes the reaction intramolecular, exhibiting Michaelis–Menten kinetics and increased reaction rates. In addition, C−H oxidation occurs with high site selectivity for remote sites. Analysis of Effective Molarity reveals that the system operates at its maximal theoretical capability for the oxidation of these remote sites. Remarkably, substrate positioning also affects Hydroxyl Rebound, whose efficiency only increases on the sites placed in proximity by recognition. Overall, these observations provide evidence that supramolecular control of substrate positioning can effectively modulate the reactivity of oxygenases and its models. [ABSTRACT FROM AUTHOR]

Cumulenes and heterocumulenes with three or more cumulative multiple bonds are usually reactive species that serve as valuable building blocks for more complex molecules but tend to isomerize or cyclize and therefore are difficult to isolate. Using a mild ligand exchange reaction at the carbon in α‐metalated ylides, we have now succeeded in the synthesis and gram‐scale isolation of the elusive cyanoketenyl anion [NC3O]−. Despite its assumed cumulene‐like structure and the delocalization of the negative charge across the whole 5‐atom molecule, it features a bent geometry with a nucleophilic central carbon atom. Computational studies reveal an ambiguous bonding situation in the anion, which can be illustrated only by a combination of different resonance structures. Nonetheless, the anion features remarkable stability, thus allowing the storage of its potassium‐crown ether salt and its application as a highly functional synthetic building block. The cyanoketenyl anion readily reacts with a series of small molecules to form more complex organic compounds, including industrially valuable compounds such as cyanoacetate. This work demonstrated that reactive species can be generated by novel synthesis methods and open up atom‐economic pathways to complex compounds from small abundant molecules. [ABSTRACT FROM AUTHOR]

Cumulenes and heterocumulenes with three or more cumulative multiple bonds are usually reactive species that serve as valuable building blocks for more complex molecules but tend to isomerize or cyclize and therefore are difficult to isolate. Using a mild ligand exchange reaction at the carbon in α‐metalated ylides, we have now succeeded in the synthesis and gram‐scale isolation of the elusive cyanoketenyl anion [NC3O]−. Despite its assumed cumulene‐like structure and the delocalization of the negative charge across the whole 5‐atom molecule, it features a bent geometry with a nucleophilic central carbon atom. Computational studies reveal an ambiguous bonding situation in the anion, which can be illustrated only by a combination of different resonance structures. Nonetheless, the anion features remarkable stability, thus allowing the storage of its potassium‐crown ether salt and its application as a highly functional synthetic building block. The cyanoketenyl anion readily reacts with a series of small molecules to form more complex organic compounds, including industrially valuable compounds such as cyanoacetate. This work demonstrated that reactive species can be generated by novel synthesis methods and open up atom‐economic pathways to complex compounds from small abundant molecules. [ABSTRACT FROM AUTHOR]

Inspired by interlocked oligonucleotides, peptides and knotted proteins, synthetic systems where a macrocycle cages a bioactive species that is "switched on" by breaking the mechanical bond have been reported. However, to date, each example uses a bespoke chemical design. Here we present a platform approach to mechanically caged structures wherein a single macrocycle precursor is diversified at a late stage to include a range of trigger units that control ring opening in response to enzymatic, chemical, or photochemical stimuli. We also demonstrate that our approach is applicable to other classes of macrocycles suitable for rotaxane and catenane formation. [ABSTRACT FROM AUTHOR]

Enantiomerically enriched crown ethers (CE) exhibit strong asymmetric induction in phase transfer catalysis, supramolecular catalysis and molecular recognition processes. Traditional methods have often been used to access these valuable compounds, which limit their diversity and consequently their applicability. Herein, a practical catalytic method is described for the gram scale synthesis of a class of chiral CEs (aza‐crown ethers; ACEs) using Rh‐catalyzed hydroamination of bis(allenes) with diamines. Using this approach, a wide range of chiral vinyl functionalized CEs with ring sizes ranging from 12 to 36 have been successfully prepared in high yields of up to 92 %, dr of up to >20 : 1 and er of up to >99 : 1. These vinyl substituted CEs allow for further diversification giving facile access to various CE derivatives as well as to their three‐dimensional analogues using ring‐closing metathesis. Some of these chiral CEs themselves display high potential for use in asymmetric catalysis. [ABSTRACT FROM AUTHOR]

We report a novel strategy for reversible modulation of the supramolecular chirality based on guest‐facilitated heteroleptic assembly of helical anionocages. Two triple‐stranded helical anionocages including a chiral cage 1 (A2L13) and a crown ether functionalized achiral cage 2 (A2L23) were synthesized by anion coordination of bis‐monourea‐based ligands and PhPO32−. Both cages exhibited favorable binding with tetraethylammonium TEA+ and cobaltocenium Cob+ (endo‐guest, bound in the cavity). Additionally, cage 2 could reversibly release and recapture the guests through binding the exo‐guest potassium ions (K+) in the crown ethers and subsequent removal of the K+ by [2,2,2]‐cryptand. The circular dichroism (CD) spectrum of cage 1 was not significantly affected by guest encapsulation or mixing with the "empty" cage 2. However, in the presence of both cage 2 and an endo‐guest/exo‐guest, the Cotton effects were reversed at 391 nm and significantly enhanced at 310 nm. This observation was attributed to the guest‐facilitated formation of heteroleptic cages that enabled effective chirality transfer from the chiral to the achiral ligands. The CD changes induced by K+ could be fully reversed by removing it with [2,2,2]‐cryptand. Sequential addition and removal of K+ allowed reversible modulation of the chirality for at least 10 cycles without significant attenuation. [ABSTRACT FROM AUTHOR]

Biological ion channels use the synergistic effects of various strategies to realize highly selective ion sieving. For example, potassium channels use functional groups and angstrom‐sized pores to discriminate rival ions and enrich target ions. Inspired by this, we constructed a layered crystal pillared by crown ether that incorporates these strategies to realize high Li+ selectivity. The pillared channels and crown ether have an angstrom‐scale size. The crown ether specifically allows the low‐barrier transport of Li+. The channels attract and enrich Li+ ions by up to orders of magnitude. As a result, our material sieves Li+ out of various common ions such as Na+, K+, Ca2+, Mg2+ and Al3+. Moreover, by spontaneously enriching Li+ ions, it realizes an effective Li+/Na+ selectivity of 1422 in artificial seawater where the Li+ concentration is merely 25 μM. We expect this work to spark technologies for the extraction of lithium and other dilute metal ions. [ABSTRACT FROM AUTHOR]

The large‐scale deployment of CO2 electroreduction is hampered by deficient carbon utilization in neutral and alkaline electrolytes due to CO2 loss into (bi)carbonates. Switching to acidic media mitigates carbonation, but suffers from low product selectivity because of hydrogen evolution. Here we report a crown ether decoration strategy on a Cu catalyst to enhance carbon utilization and selectivity of CO2 methanation under acidic conditions. Macrocyclic 18‐Crown‐6 is found to enrich potassium cations near the Cu electrode surface, simultaneously enhancing the interfacial electric field to stabilize the *CO intermediate and accelerate water dissociation to boost *CO protonation. Remarkably, the mixture of 18‐Crown‐6 and Cu nanoparticles affords a CH4 Faradaic efficiency of 51.2 % and a single pass carbon efficiency of 43.0 % toward CO2 electroreduction in electrolyte with pH=2. This study provides a facile strategy to promote CH4 selectivity and carbon utilization by modifying Cu catalysts with supramolecules. [ABSTRACT FROM AUTHOR]

Ether‐based electrolytes are promising for secondary batteries due to their good compatibility with alkali metal anodes and high ionic conductivity. However, they suffer from poor oxidative stability and high toxicity, leading to severe electrolyte decomposition at high voltage and biosafety/environmental concerns when electrolyte leakage occurs. Here, we report a green ether solvent through a rational design of carbon‐chain regulation to elicit steric hindrance, such a structure significantly reducing the solvent's biotoxicity and tuning the solvation structure of electrolytes. Notably, our solvent design is versatile, and an anion‐dominated solvation structure is favored, facilitating a stable interphase formation on both the anode and cathode in potassium‐ion batteries. Remarkably, the green ether‐based electrolyte demonstrates excellent compatibility with K metal and graphite anode and a 4.2 V high‐voltage cathode (200 cycles with average Coulombic efficiency of 99.64 %). This work points to a promising path toward the molecular design of green ether‐based electrolytes for practical high‐voltage potassium‐ion batteries and other rechargeable batteries. [ABSTRACT FROM AUTHOR]

Nuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal–organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF‐18Cr6, in which 1D channels are formed using 18‐crown‐6‐ether‐containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF‐18Cr6 possesses regular 18‐crown‐6‐ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high‐performance MOF adsorbents for separating target substances from complex aqueous environments. [ABSTRACT FROM AUTHOR]

Protein channels on the biofilm conditionally manipulate ion transport via regulating the distribution of charge residues, making analogous processes on artificial membranes a hot spot and challenge. Here, we employ metal–organic frameworks (MOFs) membrane with charge‐adjustable subnano‐channel to selectively govern ion transport. Various valent ions are binded with crown ethers embedded in the MOF cavity, which act as charged guest to regulate the channels' charge state from the negativity to positivity. Compared with the negatively charged channel, the positive counterpart obviously enhances Li+/Mg2+ selectivity, which benefit from the reinforcement of the electrostatic repulsion between ions and the channel. Meanwhile, theoretical calculations reveal that Mg2+ transport through the more positively charged channel needed to overcome higher entrance energy barrier than that of Li+. This work provides a subtle strategy for ion‐selective transport upon regulating the charge state of insulating membrane, which paves the way for the application like seawater desalination and lithium extraction from salt lakes. [ABSTRACT FROM AUTHOR]

Dispersing metal‐organic framework (MOF) solids in stable colloids is crucial for their availability and processibility. Herein, we report a crown ether surface coordination approach for functionalizing the surface‐exposed metal sites of MOF particles with amphiphilic carboxylated crown ether (CEC). The surface‐bound crown ethers significantly improve MOF solvation without compromising the accessible voids. We demonstrate that CEC‐coated MOFs exhibit exceptional colloidal dispersibility and stability in 11 distinct solvents and six polymer matrices with a wide range of polarities. The MOF‐CEC can be instantaneously suspended in immiscible two‐phase solvents as an effective phase‐transfer catalyst and can form various uniform membranes with enhanced adsorption and separation performance, which highlights the effectiveness of crown ether coating. [ABSTRACT FROM AUTHOR]

We report the synthesis and chiroptical properties of novel chiral carbon nanorings Sp‐/Rp‐[12]PCPP containing a planar chiral [2.2]PCP unit, and demonstrate that Sp‐/Rp‐[12]PCPP can not only host crown ether 18‐Crown‐6 to form ring‐in‐ring complexes with a binding constant 3.35×103 M−1, but also accommodate the complexes of 18‐Crown‐6 and S/R‐protonated amines to form homochiral S@Sp‐/R@Rp‐ and heterochiral S@Rp‐/R@Sp‐ ternary complexes, displaying significantly larger binding constants of up to 3.31×105 M−1 depending on the chiral guests. Importantly, homochiral S@Sp‐/R@Rp‐ ternary complexes exhibit an enhanced CD signal, while the heterochiral S@Rp‐/R@Sp‐ ones have a constant CD signal compared with the chiral carbon nanorings, respectively, which suggests that homochiral S@Sp‐/R@Rp‐ ternary complexes display a highly narcissistic chiral self‐recognition for S/R‐protonated chiral amines, respectively. Finally, the chiral ternary complexes can be further applied to determine the ee values of chiral guests. The findings highlight a new application of carbon nanorings in supramolecular sensors, beyond the common recognition of π‐conjugated molecules. [ABSTRACT FROM AUTHOR]

Supramolecular polymer networks (SPNs) demonstrate great potential in the development of smart materials owing to their attractive dynamic properties. However, as they suffer from the inherent weak bonding of most noncovalent cross‐links, it remains a significant challenge to construct SPNs with outstanding mechanical performance. Herein, we exploit the cryptand/paraquat host‐guest recognition motifs as cross‐links to prepare a class of highly strong and tough SPNs. Unlike those supramolecular cross‐links with relatively weak binding abilities, the cryptand‐based host‐guest interactions have a high association constant and steady complexing structure, which effectively stabilizes the network and resists mechanical deformation under external force. Such favorable structural stability endows our SPNs with greatly enhanced mechanical performance, compared with the control‐1 cross‐linked by the weakly complexed crown ether/secondary ammonium salt motif (tensile strength: 21.1±0.5 vs 2.8±0.1 MPa; Young's modulus: 102.6±4.8 vs 2.1±0.3 MPa; toughness: 90.4±2.0 vs 10.8±0.6 MJ m−3). Moreover, our SPNs also retain abundant dynamic properties including good abilities in energy dissipation, reprocessability, and stimuli‐responsiveness. These findings provide novel insights into the preparation of SPNs with enhanced mechanical properties, and promote the development of high‐performance intelligent supramolecular materials. [ABSTRACT FROM AUTHOR]

Lithium‐oxygen batteries (LOBs) are well known for their high energy density. However, their reversibility and rate performance are challenged due to the sluggish oxygen reduction/evolution reactions (ORR/OER) kinetics, serious side reactions and uncontrollable Li dendrite growth. The electrolyte plays a key role in transport of Li+ and reactive oxygen species in LOBs. Here, we tailored a dilute electrolyte by screening suitable crown ether additives to promote lithium salt dissociation and Li+ solvation through electrostatic interaction. The electrolyte containing 100 mM 18‐crown‐6 ether (100‐18C6) exhibits enhanced electrochemical stability and triggers a solution‐mediated Li2O2 growth pathway in LOBs, showing high discharge capacity of 10 828.8 mAh gcarbon−1. Moreover, optimized electrode/electrolyte interfaces promote ORR/OER kinetics on cathode and achieve dendrite‐free Li anode, which enhances the cycle life. This work casts new lights on the design of low‐cost dilute electrolytes for high performance LOBs. [ABSTRACT FROM AUTHOR]

The stability of cationic functional groups is one of the key factors determining lifetime of alkaline anion‐exchange membranes (AAEMs) and the AAEM‐based electrochemical devices. Main‐group metal and crown ether complexes are stable cations due to the absence of degradation pathways including nucleophilic substitution, Hofmann elimination, and cation redox. However, the binding strength, a key feature for AAEM applications, is overlooked in previous work. We herein propose the use of barium [2.2.2]cryptate ([Cryp‐Ba]2+) as a new cationic functional group for AAEMs due to its extremely strong binding (109.5 M−1 in water at 25 °C). The [Cryp‐Ba]2+‐AAEMs with polyolefin backbones remain stable after treatment in 15 M KOH at 60 °C for over 1500 hours. More importantly, these AAEMs are successfully applied in water electrolyzers, and an anolyte‐feeding switch method is designed to further reveal the influence of binding constants. [ABSTRACT FROM AUTHOR]

Switching between the formation/dissociation of rotaxanes is important to control the function of various types of rotaxane‐based materials. We have developed a convenient and simple strategy, the so‐called "accelerator addition", to make a static rotaxane dynamic without apparently affecting the chemical structure. As an interlocked molecule that enables tuning of the formation/dissociation speed, a metallorotaxane was quantitatively generated by the complexation of a triptycene‐based dumbbell‐shaped mononuclear complex, [PdL2]2+ (L=2,3‐diaminotriptycene), with 27C9. As a result of the inertness of the Pd2+‐based coordination structure, the metallorotaxane was slowly formed (the static state). This rotaxane formation was accelerated 27 times simply by adding Br− as an accelerator (the dynamic state). A similar drastic acceleration was also demonstrated during the dissociation process when Cs+ was added to the metallorotaxane to form the free axle [PdL2]2+ and the 27C9‐Cs+ complex. [ABSTRACT FROM AUTHOR]

Lithium (Li) extraction from brines is a major barrier to the sustainable development of batteries and alloys; however, current separation technology suffers from a trade‐off between ion selectivity and permeability. Herein, a crown ether mechanically interlocked 3D porous organic framework (Crown‐POF) was prepared as the porous filler of thin‐film nanocomposite membranes. Crown‐POF with penta‐coordinated (four Ocrown atoms and one Ntert‐amine atom) adsorption sites enables a special recognition for Li+ ion. Moreover, the four Ntert‐amine atoms on each POF branch facilitate the flipping motion of Li+ ion along the skeletal thread, while retaining the specified binding pattern. Accordingly, the crown ether interlocked POF network displays an ultrafast ion transfer rate, over 10 times that of the conventional porous materials. Notably, the nanocomposite membrane gives high speed and selectivity for Li+ ion transport as compared with other porous solid‐based mixed‐matrix membranes. [ABSTRACT FROM AUTHOR]

Macrocycle engineering is a key topic in supramolecular chemistry. When synthesizing a ring, one can obtain either complex mixtures of macrocycles of different sizes or a single ring if a template is utilized. Here, we unite these approaches along with post‐synthetic modifications to transform a single tether into multiple rings—up to five per tether. The macrocycles contain two bridged phenylpyridine ligands that are connected through a Pt atom, which defines the rings' shape, size, and host activity. All rings undergo redox reactions (between PtII and PtIV) that allow for large conformational changes. Their reactivity, together with their host performance, is a convenient way to control the capture and release of guests, to mediate ring transformations, and to control pseudorotaxane‐to‐pseudorotaxane conversions. This novel approach could serve to assemble other libraries of small ring molecules, create cyclic polymers bridged by responsive‐at‐metal nodes, and produce processable mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

Crownphyrins are hybrid macrocycles combining structural features of porphyrin and crown ethers. The molecular architecture renders them an intriguing class of hosts capable of binding neutral, and ionic guests. The presence of dynamic covalent imine linkages connecting the dipyrrin segment with the ether chain enables unusual coordination behavior of crownphyrins, as demonstrated by the formation of two classes of strikingly different complexes. The remarkable metal‐mediated expansion to the helical [2+2] macrocyclic complex is reversible. The reaction of the figure‐eight mercury(II) assembly with [2.2.2]cryptand results in ring contraction providing the metal‐free crownphyrin macrocycle. [ABSTRACT FROM AUTHOR]

The Lewis superacid bis(perchlorocatecholato)silane catalyzes C−O bond metathesis of alkyl ethers with an efficiency outperforming all earlier reported systems. Chemoselective ring contractions of macrocyclic crown ethers enable substrate‐specific transformations, and an unprecedented ring‐closing metathesis of polyethylene glycols allows polymer‐selective degradation. Quantum chemical computations scrutinize a high Lewis acidity paired with a simultaneous low propensity for polydentate substrate binding as critical for successful catalysis. Based on these mechanistic insights, a second‐generation class of silicon Lewis superacid with enhanced efficacy is identified and demonstrated. [ABSTRACT FROM AUTHOR]

The inherently tenuous adhesion strength and limited environmental tolerance of supramolecular adhesives severely restrict their application scenarios. It is challenging for the development of robust adhesives with extreme temperature tolerance. Herein, we report a new type of temperature‐resistant crown‐ether‐protein (CEP) adhesive by harnessing synergistic host–guest molecular interactions between engineered crown ether and protein building blocks. The outputs of CEP adhesive demonstrate ultrahigh shearing adhesion strength of ≈22 MPa over a wide temperature range from −196 to 200 °C, superior to other established supramolecular or polymeric adhesives. The temperature‐induced phase transition and internal bound water stabilized the system and led to superb adhesion under extreme conditions. Thus, this work pioneers a molecular engineering approach for the generation of adhesives with tailored applications in extreme settings. [ABSTRACT FROM AUTHOR]

An azobenzene‐functionalized bis‐bis(urea) ligand (Lazo) and phosphate anion assemble to give the first photoactive "aniono" constructs, tetrahedron (A4L6) and helicate (A2L3), which readily undergo interconversion through cis‐trans isomerization of the azo group under irradiation/heating. Most strikingly, the tetrahedral cage can accommodate an [18]crown‐6 molecule, which can capture two tetramethylammonium (TMA+) ions with an unusually high affinity, even capable of replacing K+ in [K([18]crown‐6)]+ to form a {(TMA)2⊂ ([18]crown‐6)}⊂ cage "Russian doll" structure. Thus, the current work may provide a model for the light‐driven binding and exchange of the biologically important K+ and TMA+ ions. [ABSTRACT FROM AUTHOR]

Electro‐reforming of renewable biomass resources is an alternative technology for sustainable pure H2 production. Herein, we discovered an unconventional cation effect on the concurrent formate and H2 production via glycerol electro‐reforming. In stark contrast to the cation effect via forming double layers in cathodic reactions, residual cations at the anode were discovered to interact with the glycerol oxidation intermediates to steer its product selectivity. Through a combination of product analysis, transient kinetics, crown ether trapping experiments, in situ IRRAS and DFT calculations, the aldehyde intermediates were discovered to be stabilized by the Li+ cations to favor the non‐oxidative C−C cleavage for formate production. The maximal formate efficiency could reach 81.3 % under ≈60 mA cm−2 in LiOH. This work emphasizes the significance of engineering the microenvironment at the electrode–electrolyte interface for efficient electrolytic processes. [ABSTRACT FROM AUTHOR]

Proton transfer is vital for many biological and chemical reactions. Hydrogen‐bonded water‐containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown‐ether‐free analogues showed very small enhancement. Inhibition studies by adding 1) external 18‐crown‐6‐ether to extract water molecules and 2) potassium ion or N‐benzyl‐n‐butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water‐containing networks. [ABSTRACT FROM AUTHOR]

Inspired by the nontrivial and controlled movements of molecular machines, we report an azobenzene‐based molecular shuttle PR2, which can perform light‐gated ion transport across lipid membranes. The amphiphilicity and membrane‐spanning molecular length enable PR2 to insert into the bilayer membrane and efficiently transport K+ (EC50=4.1 μm) through the thermally driven stochastic shuttle motion of the crown ether ring along the axle. The significant difference in shuttling rate between trans‐PR2 and cis‐PR2 induced by molecular isomerization enables a light‐gated ion transport, i.e. ON/OFF in situ regulation of transport activity and single‐channel current. This work represents an example of using a photoswitchable molecular machine to realize gated ion transport, which demonstrates the value of molecular machines functioning in biomembranes. [ABSTRACT FROM AUTHOR]

Strategies to generate heteromeric peptidic ensembles via a social self‐sorting process are limited. Herein, we report a crystal packing‐inspired social self‐sorting strategy broadly applicable to diverse types of H‐bonded peptidic frameworks. Specifically, a crystal structure of H‐bonded alkyl chain‐appended monopeptides reveals an inter‐chain separation distance of 4.8 Å dictated by the H‐bonded amide groups, which is larger than 4.1 Å separation distance desired by the tightly packed straight alkyl chains. This incompatibility results in loosely packed alkyl chains, prompting us to investigate and validate the feasibility of applying bulky tert‐butyl groups, modified with an anion‐binding group, to alternatively interpenetrate the straight alkyl chains, modified with a crown ether group. Structurally, this social self‐sorting approach generates highly stable hetero‐oligomeric ensembles, having alternated anion‐ and cation‐binding units vertically aligned to the same side. Functionally, these hetero‐oligomeric ensembles promote transmembrane transport of cations, anions and more interestingly zwitterionic species such as amino acids. [ABSTRACT FROM AUTHOR]

Crown ethers are a class of macrocyclic molecules with unique flexible structures but they are rarely integrated in covalent organic frameworks (COFs). To date, employing flexible organic units such as crown ethers to construct COFs with high crystallinity and surface area are still a challenge. In this work, two new COFs with different flexible crown ethers as backbone rather than side chains are synthesized and further employed for alkali metal ions separation. Both of COFs possess high surface areas, good crystallinity, and excellent chemical stability. Interestingly, these two new COFs with 18‐crown‐6 or 24‐crown‐8 units showed remarkable binding ability of K+ or Cs+ owing to the size‐fit effect. This work demonstrated that the unique structural features of crown ethers will lead to increase interest in fabricating COFs with crown ethers. [ABSTRACT FROM AUTHOR]

In many critical biological processes, host–guest chemistry of protein receptors is regulated by effector molecules to realize cascaded delivery of messenger molecules between different targets. Mimicking these natural processes with artificial receptors remains a challenge. Herein, we report a cascaded guest delivery between two anionocages (anion‐coordination‐driven cages), in a reversible manner, wherein binding of K+ ions by a crown ether functionalized, heteroleptic A2L3 (A=anion, L=ligand) anionocage triggers the release and delivery of a TEA+ (tetraethylammonium) guest to another A2L3 anionocage that is a weaker and less K+‐sensitive receptor. Elimination of the K+ with [2,2,2]‐cryptand enables recapture of the TEA+ by the crown ether functionalized anionocage and thus realizes a reversed guest delivery. Moreover, integrative self‐sorting of anionocages is firstly reported, leading to heteroleptic cages with enhanced guest binding affinities. [ABSTRACT FROM AUTHOR]

Chemical reduction of a benzo‐fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of 1. The doubly‐reduced helicene 12− has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes, 13− and 14−, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb+ ions each, leaving three remaining Rb+ ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of 1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in 14− vs. 2.09 Å in 1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in 1 to 20.7° in 14−. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data. [ABSTRACT FROM AUTHOR]

A series of heteroditopic receptors containing halogen bond (XB) and unprecedented chalcogen bond (ChB) donors integrated into a 3,5‐bis‐triazole pyridine structure covalently linked to benzo‐15‐crown‐5 ether motifs exhibit remarkable cooperative recognition of halide anions. Multi‐nuclear 1H, 13C, 125Te and 19F NMR, ion pair binding investigations reveal sodium cation–benzo‐crown ether binding dramatically enhances the recognition of bromide and iodide halide anions, with the chalcogen bonding heteroditopic receptor notably displaying the largest enhancement of halide binding strength of over two hundred‐fold, in comparison to the halogen bonding and hydrogen bonding heteroditopic receptor analogues. DFT calculations suggest crown ether sodium cation complexation induces a polarisation of the sigma hole of ChB and XB heteroditopic receptor donors as a significant contribution to the origin of the unique cooperativity exhibited by these systems. [ABSTRACT FROM AUTHOR]

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room‐temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K+ was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10‐fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials. [ABSTRACT FROM AUTHOR]

Highly alkaline electrolytes have been shown to improve the formation rate of C2+ products in the electrochemical reduction of carbon dioxide (CO2) and carbon monoxide (CO) on copper surfaces, with the assumption that higher OH− concentrations promote the C−C coupling chemistry. Herein, by systematically varying the concentration of Na+ and OH− at the same absolute electrode potential, we demonstrate that higher concentrations of cations (Na+), rather than OH−, exert the main promotional effect on the production of C2+ products. The impact of the nature and the concentration of cations on the electrochemical reduction of CO is supported by experiments in which a fraction or all of Na+ is chelated by a crown ether. Chelation of Na+ leads to drastic decrease in the formation rate of C2+ products. The promotional effect of OH− determined at the same potential on the reversible hydrogen electrode scale is likely caused by larger overpotentials at higher electrolyte pH. [ABSTRACT FROM AUTHOR]

Reversible oxidation reactions in electrochemically switchable oligorotaxanes with tetrathiafulvalene (TTF) decorated 24‐crown‐8 ether wheels generate intramolecular mixed‐valence and radical‐cation interactions between the wheels. This induces shuttling of the wheels and a contraction of inter‐wheel distances. Further oxidation generates repulsive forces between the TTFs and maximizes the inter‐wheel distances instead. These interactions and co‐conformational changes were not observed for structurally similar controls in which acetyl groups along the axle prevent translational motion of the wheels. This operation mode of oligorotaxanes, which is reminiscent of an accordion‐like motion, is promising for functional materials and nanodevices such as piston‐type rotaxane motors. [ABSTRACT FROM AUTHOR]

Abstract: Crown ethers have been known for over 50 years, but no example of a complex between a noble‐gas compound and a crown ether or another polydentate ligand had previously been reported. Xenon trioxide is shown to react with 15‐crown‐5 to form the kinetically stable (CH2CH2O)5XeO3 adduct, which, in marked contrast with solid XeO3, does not detonate when mechanically shocked. The crystal structure shows that the five oxygen atoms of the crown ether are coordinated to the xenon atom of XeO3. The gas‐phase Wiberg bond valences and indices and the empirical bond valences indicate that the Xe‐ ‐ ‐Ocrown bonds are predominantly electrostatic and are consistent with σ‐hole bonding. Mappings of the electrostatic potential (EP) onto the Hirshfeld surfaces of XeO3 and 15‐crown‐5 in (CH2CH2O)5XeO3 and a detailed examination of the molecular electrostatic potential surface (MEPS) of XeO3 and (CH2CH2O)5 reveal regions of negative EP on the oxygen atoms of (CH2CH2O)5 and regions of high positive EP on the xenon atom, which are also in accordance with σ‐hole interactions. [ABSTRACT FROM AUTHOR]

Abstract: Catalytic reduction of N2 to NH3 by a Ti complex has been achieved, thus now adding an early d‐block metal to the small group of mid‐ and late‐d‐block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH3 by N2 reduction and protonolysis under homogeneous, abiological conditions. Reduction of [TiIV(TrenTMS)X] (X=Cl, 1A; I, 1B; TrenTMS=N(CH2CH2NSiMe3)3) with KC8 affords [TiIII(TrenTMS)] (2). Addition of N2 affords [{(TrenTMS)TiIII}2(μ‐η1:η1‐N2)] (3); further reduction with KC8 gives [{(TrenTMS)TiIV}2(μ‐η1:η1:η2:η2‐N2K2)] (4). Addition of benzo‐15‐crown‐5 ether (B15C5) to 4 affords [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2)][K(B15C5)2]2 (5). Complexes 3–5 treated under N2 with KC8 and [R3PH][I], (the weakest H+ source yet used in N2 reduction) produce up to 18 equiv of NH3 with only trace N2H4. When only acid is present, N2H4 is the dominant product, suggesting successive protonation produces [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2H4)][I]2, and that extruded N2H4 reacts further with [R3PH][I]/KC8 to form NH3. [ABSTRACT FROM AUTHOR]

Abstract: Eine neue Familie von Heterometallkatalysatoren auf Basis von dreifach metallierten makrocyclischen Tris(salen)‐Liganden und Seltenerdmetallen wurde hergestellt und strukturell charakterisiert. Das LaZn3‐System mit seinen anionischen Liganden wie Acetat spielt eine zentrale Rolle bei der katalysierten alternierenden Copolymerisation von Cyclohexenoxid (CHO) und CO2 und liefert ein Produkt mit einem hohen Gehalt an Carbonatverknüpfungen. Bei den Lanthanoiden zeigt das CeZn3‐System eine hohe katalytische Aktivität mit einer Wechselzahl (TOF) von über 370 h−1. Die NMR‐spektroskopische Analyse des Komplexes und die Bestimmung der Endgruppen im Polymer weisen auf einen schnellen Austausch der Acetatliganden hin. Die koordinierten Acetate werden nicht nur untereinander, sondern auch gegen zugesetzte Carboxylat‐Anionen ausgetauscht. Mit solch einzigartigen Eigenschaften ist dieses System das erste Beispiel für eine als Telomerisierung ablaufende Copolymerisation von CHO und CO2. [ABSTRACT FROM AUTHOR]

Site-selective C−H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp3)-H hydroxylation with H2O2 is equipped with 18-benzocrown-6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site-selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C−H bonds, no matter the chain length. [ABSTRACT FROM AUTHOR]

Keywords: Crown Ether; MOF Nanoparticle; Mixed-Matrix Membrane; Phase-Transfer Catalyst; Universal Dispersibility EN Crown Ether MOF Nanoparticle Mixed-Matrix Membrane Phase-Transfer Catalyst Universal Dispersibility 1 1 1 08/17/23 20230821 NES 230821 B Dispersing metal-organic framework b (MOF) solids in stable colloids is critical for their availability and processibility. The crown ether-coated MOFs exhibit potential as effective phase-transfer catalysts and enable the fabrication of uniform membranes with improved performances. In their Communication (e202303280), Hang Xing et al. report a crown ether surface coordination approach that enables the universal suspension of various MOF powders into immiscible polar and nonpolar solvents, exhibiting exceptional dispersibility without compromising the accessible voids. [Extracted from the article]

The structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1-calcio-4-lithio-1,3-butadiene, 1,4-dicalcio-1,3-butadiene, and a Ca4[O] inverse crown ether complex, via the reaction between 1,4-dilithio-1,3-butadienes and calcium iodide in THF. Single-crystal X-ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds. [ABSTRACT FROM AUTHOR]

Rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with a macrocyclic 'pincer-crown ether' ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [ κ5-(15c5NCOP iPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. [ABSTRACT FROM AUTHOR]

Das Vorhandensein von Iminbindungen, die das Dipyrin-Segment mit der Etherkette verbinden, ermöglicht das ungewöhnliche Koordinationsverhalten von Crownphyrinen, wie die Bildung von zwei Klassen auffallend unterschiedlicher Komplexe zeigt, über die Bartosz Szyszko und Mitarbeiter in ihrem Forschungsartikel berichten (e202211671). Crown Ethers, Porphyrinoids, Receptors, Self-Assembly, Supramolecular Chemistry Keywords: Crown Ethers; Porphyrinoids; Receptors; Self-Assembly; Supramolecular Chemistry EN Crown Ethers Porphyrinoids Receptors Self-Assembly Supramolecular Chemistry 1 1 1 11/30/22 20221205 NES 221205 B Crownphyrine b sind Makrozyklen, die die strukturellen Merkmale von Porphyrinen und Kronenethern kombinieren. [Extracted from the article]

Macromolecular [2]rotaxanes comprising a polymer axle and crown ether wheel were synthesized to evaluate the effect of component mobility on the properties of the axle polymer, especially its crystallinity. Living ring-opening polymerization of δ -valerolactone with a pseudorotaxane initiator with a hydroxy group at the axle terminus was followed by end-capping with a bulky isocyanate. This yielded macromolecular [2]rotaxanes (M2Rs) possessing polyester axles of varying molecular weights. The crystallinity of the axle polymers of two series of M2Rs, with either fixed and movable components, was evaluated by differential scanning calorimetry. The results revealed that the effect of component mobility was significant in the fixed and movable M2Rs with a certain axle length, thus suggesting that the properties of the axle polymer depend on the mobility of the polyrotaxane components. [ABSTRACT FROM AUTHOR]

Keywords: Crown Ether; Crystal Engineering; Hydrogen Bond; Porous Framework; Proton Conduction EN Crown Ether Crystal Engineering Hydrogen Bond Porous Framework Proton Conduction 1 1 1 11/03/22 20221107 NES 221107 B Ein protonenleitendes b , wasserstoffverbrücktes organisches Gerüst (HOF) wurde aus einem I C i SB 3 sb -symmetrischen hexatopen Carbonsäurederivat mit einer 18-Krone-6-Ether-Komponente aufgebaut. Trotz der Flexibilität des Makrozyklus ermöglichen die H-Brückenmodule dem Derivat, ein hexagonal vernetztes Gerüst mit permanenter Porosität zu bilden. Wie Takayoshi Nakamura, Ichiro Hisaki et al. in ihrer Zuschrift (e202211686) berichten, besitzt das HOF 1D-Kanäle mit einem Engpass bestehend aus den Makrozyklen und zeigt Protonenleitfähigkeit (1.12×10 SP -7 sp S cm SP -1 sp ) mittels Grotthuss-Mechanismus ( I E i SB a sb =0.27 eV) unter 98 %RH. [Extracted from the article]

The bacterial KcsA channel conducts K+ cations at high rates while excluding Na+ cations. Herein, we report an artificial ion-channel formed by H-bonded stacks of crown-ethers, where K+ cation conduction is highly preferred to Na+ cations. The macrocycles aligned along the central pore surround the K+ cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration. In contrast, the Na+ cation does not fit the macrocyclic binding sites, so its dehydration is not completely compensated. The present highly K+-selective macrocyclic channel may be regarded as a biomimetic of the KcsA channel. [ABSTRACT FROM AUTHOR]