Crown Ether Research Articles

Highly Selective Lithium Transport through Crown Ether Pillared Angstrom Channels.

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.

Highly Selective Lithium Transport through Crown Ether Pillared Angstrom Channels

AbstractBiological 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.

Eu3+ -Directed Supramolecular Metallogels with Reversible Quadruple-Stimuli Response Behaviors.

Smart luminescent materials that have the ability to reversibly adapt to external environmental stimuli and possess a wide range of responses are continually emerging, which place higher demands on the means of regulation and response sites. Here, europium ions (Eu3+ )-directed supramolecular metallogels are constructed by orthogonal self-assembly of Eu3+ based coordination interactions and hydrogen bonding. A new organic ligand (L) is synthesized, consisting of crown ethers and two flexible amide bonds-linked 1,10-phenanthroline moieties to coordinate with Eu3+ . Synergistic intermolecular hydrogen bonding in L and Eu3+ -L coordination bonding enable Eu3+ and L to self-assemble into shape-persistent 3D coordination metallogels in MeOH solution. The key to success is the utilization of crown ethers, playing dual roles of acting both as building blocks to build L with C2 -symmetrical structure, and as the ideal monomer for increasing the energy transfer from L to Eu3+ 's excited state, thus maintaining the excellent luminescence of metallogels. Interestingly, such assemblies show K+ , pH, F- , and mechano-induced reversible gel-sol transitions and tunable luminescence properties. Above findings are useful in the studies of molecular switches, dynamic assemblies, and smart luminescent materials.

Supramolecular Aza Crown Ether Modulator for Efficient and Stable Perovskite Solar Cells

AbstractMolecular modulators have been demonstrated to be an effectual strategy for reducing the defect at the interface and in bulk of perovskite and ameliorating the performance and stability of perovskite solar cells (PSCs). Herein, 1‐aza‐15‐crown 5‐ether (A15C5), with a unique nitrogen heterocyclic structure as a molecular modulator is introduced at the interface between perovskite layer and hole transport layer of PSCs. Multiple supramolecular synergistic interaction between A15C5 and perovskite dramatically suppress and passivate defects, resulting in a 38% decrease in electron trap‐state density in perovskite. The formation of two‐dimensional/th3D perovskite heterojunctions induced by planar A15C5 releases residual strain of perovskite film, optimizes the match of energy level array and boosts the stability of devices. Consequently, A15C5‐modulated PSC achieves an impressing efficiency of 24.13% along with excellent humidity, light and thermal stability. This work provides a typical strategy to utilize supramolecular crown ether in PSCs.

Liquid–liquid extraction of strontium from acidic solutions into ionic liquids using crown ethers

Abstract90Sr is one of the most monitored fission products. New efficient methods for strontium separation are therefore sought. Over the past 20 years, crown ethers solutions in ionic liquids (ILs) have been confirmed to efficiently extract strontium from acidic solutions. Despite all the work done in this field, the extraction mechanism is still not completely clear. Depending on experimental conditions, the extraction is believed to proceed either in the form of an ion-association complex [Sr·CE·(NO3)2] or via exchange between [Sr·CE]2+ and two IL cations. This work aims to study the influence of several extraction parameters and compare them with the presumed mechanisms.

Access to 1,2,3-triphospholide ligands by reduction of di-tert-butyldiphosphatetrahedrane.

Di-tert-butyldiphosphatetrahedrane (tBuCP)2 (A) is a reactive tetrahedral molecule which may serve as a source of new phosphaorganic molecules and ligands. However, the redox chemistry of this compound has not yet been investigated. Here, we show that the reduction of A with alkali metals (AM = Li, Na, K, Rb and Cs) affords 1,2,3-triphospholides [AM(crown ether)][1,2,3-P3C2tBu2] (1-5, [AM(crown ether)] = [Li([12]crown-4)2]+, [Na([15]crown-5)2]+, [K([18]crown-6)]+, [Rb([18]crown-6)]+, and Cs+) with 1,3-diphospholides [AM(crown ether)][1,3-P2C3tBu3] (6-10) formed as by-products. The potassium salt 3 was isolated on a preparative scale, allowing for reactivity studies. Transmetalation with iron(II) and ruthenium(II) chlorides yielded the sandwich complexes [Cp*M(η5-1,2,3-P3C2tBu2)] (11, M = Fe; 12, M = Ru, Cp* = C5Me5) featuring η5-coordinated triphospholide ligands. Treatment of 3 with [Cp2Fe][BAr4F] or [H(Et2O)2BAr4F] (BAr4F = B{C6H3(CF3)2}4) afforded the polyphosphorus compound tBu4C4P6 (13), which presumably results from the dimerisation of a 1,2,3-triphospholyl radical intermediate (1,2,3-P3C2tBu2)˙ (3˙). Tetracyclic 13 is closely structurally related to an isomer of the hydrocarbon hypostrophene (C10H10).

Enhancing Li+ recovery in brine mining: integrating next-gen emotional AI and explainable ML to predict adsorption energy in crown ether-based hierarchical nanomaterials.

Artificial intelligence (AI) is being employed in brine mining to enhance the extraction of lithium, vital for the manufacturing of lithium-ion batteries, through improved recovery efficiencies and the reduction of energy consumption. An innovative approach was proposed combining Emotional Neural Networks (ENN) and Random Forest (RF) algorithms to elucidate the adsorption energy (AE) (kcal mol-1) of Li+ ions by utilizing crown ether (CE)-incorporated honeycomb 2D nanomaterials. The screening and feature engineering analysis of honeycomb-patterned 2D materials and individual CE were conducted through Density Functional Theory (DFT) and Gaussian 16 simulations. The selected honeycomb-patterned 2D materials encompass graphene, silicene, and hexagonal boron nitride, while the specific CEs evaluated are 15-crown-5 and 18-crown-6. The crown-passivated 2D surfaces held a significant adsorption site through van der Waals forces for efficient recovery of Li+ ions. ENN predicted the targeted adsorption sites with high precision and minimal deviation. The eTAI (XAI) based Shapley Additive exPlanations (SHAP) was also explored for insight into the feature importance of CE embedded 2D nanomaterials for the recovery of Li+ ions. The extreme gradient boosting algorithm (XGBoost) model demonstrated a RT-2-MAPE = 0.4618% and ENN-2-MAPE = 0.4839% for the feature engineering analysis. This research would be an insight into the AI-driven nanotechnology that presents a viable and sustainable approach for the extraction of natural resources through the application of brine mining.

Intra-host π-π interactions in crown ether complexes revealed by cryogenic ion mobility-mass spectrometry.

Cryogenic ion mobility-mass spectrometry was performed to investigate the relative abundance of conformers of dinaphtho-24-crown-8 (DN24C8) complexes with alkali metal cations M+ (M = Li, Na, K, Rb, and Cs). The "closed" conformers of M+(DN24C8) with short distances between two naphthalene rings in the crown ethers were predominantly observed for all complexes at 86 K. The two noncovalent interactions, host-guest and intra-host interactions, were analyzed separately by density functional theory calculations to reveal the origin of the stability of the closed conformers. As a result, it was revealed that the intra-host π-π interactions have a more critical role in determining the stability of the conformers than the host-guest interactions. The closed conformers of M+(DN24C8) also have wider regions of the π-π interactions than those of the M+(dibenzo-24-crown-8) complexes.

Dense arrangement of crown ethers in graphene: novel graphitic carbon oxides with enhanced optoelectronic properties.

Incorporating crown ethers into a graphene lattice presents an efficient means of tuning its properties and expanding its range of potential applications. This study employed density functional theory calculations to introduce a series of novel graphitic carbon oxides through the dense arrangement of crown ethers featuring varying cavity sizes within the graphene structure. These newly developed graphitic carbon oxides exhibit thermodynamic and dynamic stability. They also manifest improved stability relative to previously reported graphene oxides with similar oxygen content. Notably, a robust linear relationship is observed between the cohesive energies and the proportion of oxygen atoms. The electronic properties of these graphitic carbon oxides span a spectrum of characteristics, including semi-metallic, metallic, and semi-conducting behavior. Their calculated band gaps range from 0.11 eV to 4.38 eV. Specifically, our analysis reveals that C6G-1, characterized by its largest crown ether-like nanopore with six oxygen atoms, holds potential as a material for photocatalytic water splitting. Moreover, these materials exhibit anisotropic optical properties, showcasing a significant enhancement in absorption within the infrared and visible regions relative to pristine graphene. Given the successful experimental synthesis of crown ether in graphene, we anticipate that our findings will contribute to the widespread utilization of graphene derivatives in low-dimensional electronic, catalytic, and optical devices.

THERMODYNAMICS OF COMPLEXATION WITH 18-CROWN-6 WITH L-CARNOSINE AND ITS CONFORMATIONAL ANALYSIS

The study of model biological "guest-host" processes between dipeptides and crown ethers allows us to understand the nature of molecular recognition in living systems. The reaction of the formation of the molecular complex of the crown ether 18-crown-6 (18K6) with L-carnosine (L-Carn) in water at T = 298.15 K was studied using isothermal titration calorimetry. The mixing heats of aqueous solutions of L-carnosine with aqueous solutions of 18-Carn-6 were determined on a TAM III titration calorimeter system (TA Instruments) equipped with a 20 mL titration cell. In the main experiment, the heat of mixing of aqueous 18K6 solution with aqueous L-Carn solution was determined. In separate experiments the heat effect of dilution of L-Carn solution in water was measured, which was taken into account in determining the thermal effect of complex formation. From the thermochemical data, the thermodynamic parameters of the molecular complex formation reaction were calculated. It was found that the presence of a histidine fragment in the L-Carn structure leads to an increase in the stability of the molecular complex L-Carn with 18K6 and to a decrease in the exothermicity of complex formation as compared to the complex formation of alanine with 18K6. Thermodynamic parameters of [L-Carn 18K6] formation reaction are similar to thermodynamics of 18K6 complex formation with histidine. Quantum-chemical calculations were performed within the framework of the electron density functional theory using the GAUSSSIAN 03 software package. The results were visualized using the ChemCraft software. We performed the conformational analysis of L-Carn within the framework of the density functional theory (version B3LYP/6-31G**) to analyze the reactivity of L-Carn structural fragments. For three stable conformers in the M062X/ aug-cc-pVTZ approximation the geometric parameters were obtained and the electron density distribution was analyzed within the framework of the QTAIM method as well as the NBO scheme. For citation: Usacheva T.R., Belova N.V., Saturina E.V., Krutova O.N., Lukanov M.M., Pavlova E.A. Thermodynamics of complexation with 18-crown-6 with l-carnosine and its conformational analysis. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 5. P. 21-31. DOI: 10.6060/ivkkt.20236605.6781.

Molecular vessels from preorganised natural building blocks.

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

APPLICATION OF SULFUR RADICAL ANIONS IN ORGANIC SYNTHESIS. DETERMINATION OF FORMS OF SULFUR

The study of reactions involving sulfur anion radicals in organic synthesis has become an area of active research in the last few years. The role of polysulfide radicals in the electrochemical processes of lithium-sulfur (Li-S) batteries has been particularly discussed. Understanding the pathways of the electrochemical reactions is crucial for improving the performance of Li-S batteries. In order to summarize and analyze the most relevant literature data, the review presents information on the application and study of sulfur anion radicals in organic synthesis and methods for the determination of sulfur forms. We have classified and discussed in detail the spectra of various forms of sulfur in the ultraviolet and visible ranges. The article describes the choice of solvent, the correlation between the properties of solvents, the influence of the nature of the solvent on the absorption band shift of sulfur particles and on the stability of the anion radical, the identification of sulfur forms in the ultraviolet and visible spectrum regions, and the possibility of stabilizing anion radicals by complexation with crown ethers. The absorption bands for S22-, S32-, S52-, S72- strongly overlap with other particles while having lower intensities, leading to different conclusions regarding the distribution of polysulfides and different forms of sulfur in aqueous media. The data presented in the review have an applied meaning, contribute to the understanding of the application of sulfur anion radicals in organic synthesis and can be used for the choice of method for the determination of sulfur forms and solvent. This review article may be of interest to specialists in the field and will help to plan studies on the study of sulfur forms and the interpretation of spectra of different sulfur forms.

Optimization and kinetics of crown ether-based hydroxyl-rich organic polymers for sustainable CO2 fixation and iodine vapor adsorption

Hydroxyl-rich organic polymers with crown ethers were fabricated and utilized for sustainable CO2 fixation and iodine adsorption. The synergistic mechanism was proved in terms of experimental results and study of kinetics.

Tuning of the antiferromagnetic-type interaction in photo-excited single-decker porphyrin-lanthanide complexes with different crown capping ligands.

The magnetic interaction between the total angular momentum (J) of the 4f electrons in a lanthanide ion and the orbital angular momentum (L) of a porphyrin in the photo-excited states of 5,10,15,20-tetraphenylporphyrinato Dy(III) complexes capped with a crown ether with one of two different symmetries, 12-crown-4 or 1-aza-12-crown-4, was investigated by temperature- and magnetic dependent magnetic circular dichroism (VT-VH MCD). The analysis was conducted on the complexes with different non-aromatic ligands to investigate how different symmetries of the non-aromatic ligands have an impact on the electronic interaction causing an anti-parallel orientation of J and L. The magnitude of the J-L interaction was determined from simulation-based fitting to experimental ratios. While in both cases an antiferromagnetic-type interaction between J and L was identified, an asymmetric non-aromatic ligand resulted in an increased magnitude of the J-L interaction.

Multi-stimuli-responsive luminescence enabled by crown ether anchored chiral antimony halide phosphors

The chirality-dependent lattice distortion assisted by a crown ether leads to an intense STEs emission along with CPL. The distinct STEs endows the Sb halides with multi-stimuli-responsive PL behaviours towards excitation wavelength and temperature.

Electromigration separation of lithium isotopes with B12C4, B15C5 and B18C6 systems

In the aqueous-organic biphasic electromigration system, the larger cavity size of crown ethers, the weaker binding between crown ethers and Li+, and the lower dissociating voltage of complexes and initial voltage enriching 6Li in the catholyte.

Designing 2D stripe winding network through crown-ether intermediate Ullmann coupling on Cu(111) surface.

Chemical synthesis typically yields the most thermodynamically stable ordered arrangement, a principle also governing surface synthesis on an atomically level two-dimensional (2D) surface, fostering the creation of structured 2D formations. The linear connection arising from energetically stable chemical bonding precludes the generation of a 2D random network comprised of one-dimensional (1D) convoluted stripes through on-surface synthesis. Nonetheless, we underscored that on-surface synthesis possesses the capability not solely to fashion a 2D ordered linear network but also to fabricate a winding 2D network employing a precursor with a soft ring and intermediate state bonding within the Ullmann reaction. Here, on-surface synthesis was exhibited on Cu(111) employing a 2D self-assembled monolayer array of 4,4',5,5'-tetrabromodibenzo[18]crown-6 ether (BrCR) precursors. These precursors were purposefully structured, with a crown ether ring at the core and Br atoms positioned at the head and tail ends, facilitating preferential connections along the elongated axis to foster a 1D stripe configuration. We illustrate how adjustments in the quantities of the intermediate state, serving as a primary linkage, can yield a labyrinthine, convoluted winding 2D network of stripes. The progression of growth, underlying mechanisms, and electronic structures were scrutinized using an ultrahigh vacuum low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) setup combined with density functional theory (DFT) calculations. This experimental evidence opens a novel functionality in leveraging on-surface synthesis for the formation of a 2D random network. This discovery holds promise as a pioneering constituent in the construction of a ring host supramolecule, augmenting its capability to ensnare guest atoms, molecules, or ions.

Novel chalcone-based crown ethers: synthesis, characterization, antioxidant activity, biological evaluations, and wastewater remediation.

Macrocycles play a pivotal and indispensable role within the realms of both medicine and industry. In the course of our research endeavors, we have successfully synthesized five distinct macrocyclic chalcone entities, each showcasing remarkable biological and anti-oxidative properties. Furthermore, these compounds exhibit exceptional promise as potent agents for the removal of dyes in wastewater treatment processes. The synthesis of these key constituents was achieved through the judicious application of the Robinson ether synthesis and Claisen-Schmidt condensation reactions. The structures of compounds 1a-f and 2a-e were characterized by using analytical techniques such as FTIR, 1H NMR, 13C NMR, and DEPT 13C NMR spectroscopy. These macrocycles also underwent in vitro assessments to measure their antibacterial activity using the agar well diffusion method. The results revealed that the macrocyclics were more sensitive to Gram-positive than Gram-negative bacteria. For example, compound 2d exhibited an inhibition zone of 20 mm at 150 ppm. The antioxidant activity as determined via the DPPH method established that all tested compounds showed moderate radical-scavenging ability. Specifically, compound 2e (at 1000 ppm) exhibited antioxidant activity of 79% inhibition of radicals, in comparison to 90% for the standard ascorbic acid. The latter was demonstrated by using methylene blue as an adsorbate under simulated wastewater conditions. Outstandingly, the most effective compounds were 2d and 2c, which achieved removal rates of 96.54% and 92.37%, respectively, for methylene blue dye.

A redox-responsive macrocycle based on the crown ether C7Te for enhanced bacterial inhibition.

Due to increasing bacterial resistance to disinfectants, there is an urgent need for new therapeutic agents and strategies to effectively inhibit bacteria. Accordingly, we have designed and synthesized a novel crown ether known as C7Te, and its oxidized form C7TeO. These compounds have demonstrated antibacterial effectiveness against Gram-negative E. coli (BL21). Notably, C7Te has the capability to enhance the inhibition of E. coli and the prevention of biofilm formation by H2O2 through a redox response. It can also effectively disrupt preformed E. coli biofilms by penetrating biofilm barriers effectively. Additionally, computer modeling of the bacterial cell membrane using nanodiscs composed of phospholipids and encircled amphipathic proteins with helical belts has revealed that C7Te can insert into and interact with phospholipids and proteins. This interaction results in the disruption of the bacterial cell membrane leading to bacterial cell death. The utilization of redox-responsive crown ethers to augment the antibacterial capabilities of H2O2-based disinfectants represents a novel approach to supramolecular bacterial inhibition.

Fast fabrication of μm-thick perovskite films by using a one-step doctor-blade coating method for direct X-ray detectors

The inclusion of a high-content crown ether in the perovskite precursor effectively increases the thickness of the doctor-bladed perovskite film and enhances the X-ray photoresponse of the direct X-ray detector.