Use Of Crown Ethers Research Articles

Single Layer of Crown Ether Enables Efficient, Stable, and Pb Leakage-Free Inverted Perovskite Solar Cells.

Significant challenges in ensuring long-term stability, addressing environmental safety issues, and improving efficiency have hindered the commercialization of inverted Pb-based halide perovskite solar cells (PeSCs). One reasonable approach to addressing these issues is to place an effective buffer layer between the perovskite active layer and the electrode. In this study, we demonstrate the use of crown ether, di-tert-butyl dibenzo-18-crown-6, as a single buffer layer to improve the efficiency, long-term stability, and environmental safety of PeSCs for the first time. The crown ether buffer layer suppressed Ag diffusion from the Ag metal electrodes, thereby improving the performance and lifetime of the device. In addition, it effectively captures Pb ions that may leak into the environment during the whole lifetime of devices, thereby enhancing the environmental safety of PeSCs. Furthermore, PeSCs incorporating crown ethers as buffer layers demonstrated enhanced stability in a nitrogen atmosphere and achieved a high power conversion efficiency of 22.8%. Consequently, this crown ether buffer layer offers an effective and straightforward strategy capable of achieving efficient, stable, and environmentally safe PeSCs.

Ammonium-Binding Bifunctional Aza-Crown Ether Catalysts for Substrate-Selective Hydroxyl Functionalization.

Herein, we describe a new bifunctional macrocyclic catalyst that employs multiple weak noncovalent interactions to enable substrate-selective O-silylation of ammonium alcohols over more reactive aliphatic alcohols with up to >20:1 substrate selectivity. Our catalytic strategy merges (i) the use of crown ethers as ammonium-binding receptors and (ii) the exploitation of N-methyl imidazole as a catalytic motif. Our collective mechanistic studies reveal the importance of receptor size, conformational preorganization, and the number of hydrogen-bonding acceptor units needed to achieve high selectivity within the macrocyclic binding pocket.

New Wine in Old Bottle: Crown Ether-Functionalized Digital Polymer toward Efficient MALDI-TOF MS/MS Decoding via a Classical Supramolecular Interaction.

Digital polymers (DPs), which serve as promising molecular-level storage media, have increasingly garnered interest. Their application significantly depends on the efficiency of the information writing (synthesis) and reading processes (sequencing). For reading, rational incorporation of weak bonds in the main chain was applied in most cases in order to improve readability of the tandem mass spectra (MS/MS), which would limit the chain length of DPs, thus reducing the information storage capacity. In this study, the introduction of commercially available crown ether (CE) at the terminus of digital oligo(γ-butyrolactone)s (DOBLs) significantly enhances the predictability and fidelity of matrix-assisted laser desorption/ionization time-of-flight tandem mass spectra (MALDI-TOF MS/MS), thus improving the decoding process. The use of crown ether, leveraging a well-established supramolecular interaction with alkali cations known since 1967, offers a strong affinity between ionization agents and CE motifs, to form a selective effect of the desired fragments during the tandem MS. This method is particularly effective for long-chain DPs, extending up to 32-mer, and allows for customizable fragmentation patterns. The incorporation of CE at the DP chain end presents a novel and efficient strategy for enhancing MS/MS readability and amplifying the information storage capacity of polymers.

Extraction of cesium and strontium from nitric acid hlw by a mixture of extractants of -18-crown-6 and -21-crown-7 derivatives in organic solvents

The processes of extraction of stable isotopes of cesium and strontium by solutions of macrocyclic polyesters in organic solvents from nitric acid mediums have been studied. The e ect of the crown ether structure and solvent type on the distribution coe cients of cesium ( D Cs) and strontium ( D Sr) has been studied. Extraction systems for the combined extraction of cesium and strontium were tested, in which 1,1,7-trihydrododeca uoroh eptanol and chlorohydrocarbons were used as solvents. It is shown that the highest D Cs and D Sr in the combined extraction of metals are observed when using a mixture of DTBDB18C6 and DCH18C6. Experimental data con rm the high e ciency of the use of crown ethers for the extraction of cesium and strontium into a separate fraction when handling radioactive waste.

Accelerated Polymerization of Lactide Driven by a DBU‐based Salt and a 15‐Crown‐5 Ether Sacrificial Kinetic Booster

The recent advances in polymerization of lactide (LA) from organic salts enriched the toolbox to prepare well-defined materials. Herein we report the use of crown ether (CE) to catalyze the polymerization of L-LA initiated by 12-hydroxydodecanoic acid (HDA) activated by one equivalent of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). While both size and structure of the ether catalyst play an important role on the overall rate of reaction, the CE decomplexation is crucial to outpace transfer reactions and also permit the process to be moderately conducted under air atmosphere by an efficient water trapping process.

In-situ growth of low-dimensional perovskite-based insular nanocrystals for highly efficient light emitting diodes

Regulation of perovskite growth plays a critical role in the development of high-performance optoelectronic devices. However, judicious control of the grain growth for perovskite light emitting diodes is elusive due to its multiple requirements in terms of morphology, composition, and defect. Herein, we demonstrate a supramolecular dynamic coordination strategy to regulate perovskite crystallization. The combined use of crown ether and sodium trifluoroacetate can coordinate with A site and B site cations in ABX3 perovskite, respectively. The formation of supramolecular structure retard perovskite nucleation, while the transformation of supramolecular intermediate structure enables the release of components for slow perovskite growth. This judicious control enables a segmented growth, inducing the growth of insular nanocrystal consist of low-dimensional structure. Light emitting diode based on this perovskite film eventually brings a peak external quantum efficiency up to 23.9%, ranking among the highest efficiency achieved. The homogeneous nano-island structure also enables high-efficiency large area (1 cm2) device up to 21.6%, and a record high value of 13.6% for highly semi-transparent ones.

The use of crown ethers as sensor material in potentiometry technique

The use of crown ethers as sensor material in potentiometry technique

Soluble alkali-metal carbon nanotube salts for n-type thermoelectric composites with improved stability

We present a method to dissolve carbon nanotubes that simultaneously allows to prepare n-doped films. These films are composed of thinner bundles of longer tubes when compared to films prepared using surfactants and sonication. Their negative Seebeck coefficient and high electrical conductivity make them good candidates for thermoelectric applications. We investigate their stability in air by aging them at elevated temperatures, showing stabilities over 500 h, which is further improved by the use of crown ethers. Finally, we demonstrate the usefulness of the prepared materials by fabricating an organic thermoelectric generator comprising 40 legs.

Accelerated polymerization of N-carboxyanhydrides catalyzed by crown ether

The recent advances in accelerated polymerization of N-carboxyanhydrides (NCAs) enriched the toolbox to prepare well-defined polypeptide materials. Herein we report the use of crown ether (CE) to catalyze the polymerization of NCA initiated by conventional primary amine initiators in solvents with low polarity and low hydrogen-bonding ability. The cyclic structure of the CE played a crucial role in the catalysis, with 18-crown-6 enabling the fastest polymerization kinetics. The fast polymerization kinetics outpaced common side reactions, enabling the preparation of well-defined polypeptides using an α-helical macroinitiator. Experimental results as well as the simulation methods suggested that CE changed the binding geometry between NCA and propagating amino chain-end, which promoted the molecular interactions and lowered the activation energy for ring-opening reactions of NCAs. This work not only provides an efficient strategy to prepare well-defined polypeptides with functionalized C-termini, but also guides the design of catalysts for NCA polymerization.

Enantioselective Alkenylation of Aldehydes with Protected Propargylic Alcohols in the Presence of a Crown Ether as an Additive

AbstractThe enantioselective alkenylation of aldehydes with protected propargylic alcohols catalyzed by chiral amino thiol has been developed. The best results were obtained for the hydrozirconation‐transmetallation to zinc protocol. The key element of the method is the use of crown ethers as an additive. The enantioselectivity of the reaction performed in the presence of the crown ether was substantially higher than in the absence of this additive and the enantiomer ratio reached 98:2.magnified image

Crown ethers reverse P-glycoprotein-mediated multidrug resistance in cancer cells

Multidrug resistance (MDR) is a widespread phenomenon exhibited by many cancers and represents a fundamental obstacle for successful cancer treatments. Tumour cells commonly achieve MDR phenotype through overexpression and/or increased activity of ABC transporters. P-glycoprotein transporter (P-gp, ABCB1) is a major cause of MDR and therefore represents a valuable target for MDR reversal. Several naturally occurring potassium ionophores (e.g. salinomycin) were shown to inhibit P-gp effectively. We have previously shown antitumour activity of a number of 18-crown-6 ether compounds that transport potassium ions across membranes. Here we present data on P-gp inhibitory activity of 16 adamantane-substituted monoaza- and diaza-18-crown-6 ether compounds, and their effect on MDR reversal in model cell lines. We show that crown ether activity depends on their lipophilicity as well as on the linker to adamantane moiety. The most active crown ethers were shown to be more effective in sensitising MDR cells to paclitaxel and adriamycin than verapamil, a well-known P-gp inhibitor. Altogether our data demonstrate a novel use of crown ethers for inhibition of P-gp and reversal of MDR phenotype.

Use of crown ethers to isolate intermediates in ammonia-borane dehydrocoupling reactions.

The presence of 18-crown-6 in the Lewis acid-promoted dehydrocoupling reaction of ammonia borane permits isolation of [(THF)BH2NH3](+) and [BH2(NH3)2](+) cations. [(THF)BH2NH3](+) reacts with Lewis bases to give either boron adducts or by deprotonation at nitrogen to give borazine and ammonia-borane.

Thermodynamic and Polarization Parameters of Dibenzo-18- crown- 6 in Mixed Methanol Water Solvents

The different thermodynamic parameters for the solvation (Free energies, enthalpies, and entropies) ( ΔGs, ΔHs &TΔSs) for dibenzo-18-crown-6 in mixed methanol-water solvents were calculated form the experimental solubility data at different temperatures. From the experimental refractive indices and densities for the saturated solutions, the total polariza- tion (Pt), polarizability (α), induced dipole moment (μ) and the contribution of the electronic permittivity (e∞) were evaluated. The solvation behavior of the crown ether used in these media was discussed in view of the estimated refraction and po- larization parameters.Since dibenzo 18-crown-6 has a wide applications in analytical, industrial and biological ones, then the aim of this study is to explain its solvation behaviours in methanol. 1. Intoduction In recent years, macrocyclic ligands have been used in ion chromatography as components of both the stationary and mobile phases. The interest in these molecules derives from their selectivity in binding specificcations. Some labs fo- cused on the use of macro-cycles in ion chromatography in the separation of both cations and anions .Nakagawa et al. investigated the use of crown ethers in the mobile phase for the separation of amine cations, peptides, and sulfonic acids. They showed that the increase in capacity factors is related to the stability of the complex for those compounds that form complexes with the crown ether. They also showed that the concentration of crown ether influences the capacity factors for some compounds. Peak resolution between mono- and divalent cations using an unmodified silica gel column . The

The use of immobilized crown ethers as in-situ N-protecting groups in organic synthesis and their application under continuous flow

In addition to their high affinity for inorganic cations, crown ethers have been shown to efficiently sequester ammonium ions, forming a stable adduct via hydrogen bonding. Using this principle, several authors have reported the use of crown ethers as protecting groups for amines however to date, their widespread use has been somewhat precluded by the difficulties associated with removal of the crown ether from the resulting reaction mixture. In order to address this problem, we report the preparation of an immobilized 18-crown-6 ether derivative and its incorporation into a flow reactor, demonstrating the ability to use and recycle the reagent for the chemoselective O-acylation and alkylation of bifunctional compounds such as 4-(2-aminoethyl)phenol and 4-nitrophenol.

Amplification of the index of refraction of aqueous immersion fluids with crown ethers

There is a current need for high refractive index (RI) materials that can be used in aqueous systems for improving 193-nm immersion photolithography. Although heavy metal salts such as Ca2+ and Ba2+ have the potential to substantially increase the RI of aqueous solutions, the water solubility of these salts with common anions is often too low to achieve concentrations that significantly increase the RI to the desired values. We therefore investigate the use of crown ethers to enhance the solubility of these cations. Most of crown ethers are soluble in water, are inexpensive materials, and are available commercially. 15-crown-5-ether and 12-crown-4-ether are liquids at room temperature and therefore can be used as neat immersion fluids without dilution in water. Saturation of crown ethers with inorganic salts do not lead to any increase in the refractive index due to their low solubility in such an apolar medium. Thus, the use of inorganic salts as refractive index enhancement agents does not seem to be a desirable proposition in the present case. Instead, the use of crown ethers or their derivatives can be an alternative system, since these compounds have properties such as density, viscosity, and boiling point similar to aqueous media.

Molecular Manipulation Based on Allosteric Crown-Appended Units and Related Systems

Synthesis of many potentially useful molecular units by chemists promotes the development of methods for constructing supramolecular architectures. Indeed, programmed supramolecular interactions play crucial roles in the preparation of well-defined nanoscale assemblies. This review highlights successful approaches in designing for specific functions systematically. The incorporation and synergistic communication of conformation-switchable segments into molecules bears great promise. Allostery, which is often observed in naturally occurring proteins, provides a hint for molecular manipulation. In supramolecular chemistry crown ethers can serve not only as substrate-binding sites but also as function-tuning sites. With the combination of synthetic versatility and well-tailored design, diverse capabilities (molecular recognition, catalytic properties, chirality, actuation, and so on) become possible at the molecular or mesoscopic level. The synthetic preparation of advanced molecular units allows the systems to become smarter, and promise nanosystems with programmable functions. This review considers mainly the use of crown ethers which act as anchoring as well as allosteric sites, from the standpoint of design for molecular manipulation. It also gives a brief discussion of recent progress in molecular manipulation, based on related systems. The "synthetic systems" described in the present review should contribute to not only to more elaborate "chemical systems", but also to the evolving field of "molecular machinery", that can utilize these systems.

A Synthesis of Heteroaromatic S- and N-β-Glycosides of N-Acetylglucosamine under Phase-Transfer Conditions

The use of crown ethers for a phase transfer-catalyzed synthesis of heteroaromatic glycosides of N-acetylglucosamine was studied. The solid-liquid system and the catalysis by 15-crown-5 were found to provide for both a 100% conversion of the alpha-D-glucosaminyl chloride peracetate and a high reaction rate. The interaction of alpha-D-glucosaminyl chloride peracetate and oxadiazole and triazole mercapto derivatives capable of thiol-thione tautomerism carried out at room temperature in acetonitrile in the presence of anhydrous potassium carbonate and crown ethers was shown to lead to both S- and N-glycosides. The structures of the compounds synthesized were confirmed by X-ray analysis and 13C and 1H NMR spectroscopy.

A solution to stripping problems caused by organophilic anion impurities in crown-ether-based solvent extraction systems: a case study of cesium removal from radioactive wastes

A problem related to stripping efficiency has been identified in the use of crown ether derivatives to extract alkali metal salts, and a simple solution is proposed. Focusing on the specific case of cesium extraction from simulants of alkaline nuclear waste by a calix-crown ether, calix[4]arene-bis( tert-octylbenzo-crown-6) (BOBCalixC6), it has been shown that low concentrations of a common surfactant, dodecylsulfonate, seriously impairs stripping. This surfactant has been identified as a trace component in laboratory simulants and was subsequently studied in experiments in which it was added in controlled amounts. Computer modeling of stripping behavior is consistent with the formation of a 1:1:1 organic-phase complex of the calix-crown with cesium and its nitrate counterion. In the presence of an organophilic surfactant anion, cesium ion can only effectively be stripped from the solvent until its organic-phase concentration becomes equivalent to that of the surfactant anion. Cleanup of nuclear waste requires a high decontamination factor for 137Cs, and insufficient stripping therefore leads to process failure. This difficulty raises a generic issue for use of crown ethers for waste decontamination or for other hydrometallurgical applications. However, remediation is possible by simply adding an alkylamine to the solvent. The alkylamine in its ammonium form acts as a counterion of the organophilic anion, suppressing the deleterious effects of the organophilic anion and allowing the cesium cation to be stripped efficiently. Trioctylamine (TOA) at a concentration of only 1 mM was found effective at restoring stripping performance while not affecting extraction. Ultimately, this solvent amendment enabled the development of a robust solvent for the Caustic-Side Solvent Extraction (CSSX) process and its successful demonstration on actual nuclear waste.

Crown ether-doped sol-gel materials for strontium(II) separation

Hybrid organic/inorganic sol-gel materials containing an encapsulated crown ether ligand were found to selectively remove 91.4 +/- 1.3% of Sr2+ from a solution containing excess of competing ions such as Ca2+. The crown ether ligand, 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-bis(malonate) ligand (Na4oddm), with known high affinity for Sr2+ was encapsulated in hydrophilic SiO2 through a simple sol-gel process. Washing the Sr(2+)-loaded gel with acid or ethylenediaminetetraacetic acid disodium salt recovered the Sr2+ from the sol-gel sorbent and regenerated the doped gel for subsequent Sr2+ intake. The approach reported here is a new alternative to the use of crown ethers in metal ion separation through, for example, solvent extraction or the use of sorbents containing chemically grafted crown ether ligands.

Capillary electrophoretic separation enhanced by a macrocyclic dioxopolyamine additive

Macrocyclic polyamines, or in particular dioxopolyamines, are strong receptors for analytes such as metal ions, catechol and catecholamine derivatives. In this paper, based on their interaction with a dioxopolyamine compound: 1,4,7,10-tetraazacyclotridecane-11,13-dione (or dioxo[13]aneN 4), we report its use as an additive in capillary electrophoresis (CE) to improve the separation resolution and selectivity of various model analytes. Using an imidazole–acetic acid electrolyte with dioxo[13]aneN 4 as the only additive, alkali metal, alkaline earth metal and NH 4 + ions can be effectively separated and detected by using CE with indirect UV detection, as opposed to the use of crown ether in which another additive, such as α-hydroxyisobutyric acid, is needed. The host–guest interaction between dioxo[13]aneN 4 and metal and NH 4 + ions can modify their electrophoretic mobilities, and therefore can be used to differentiate the various cations, especially between K + and NH 4 +, and between Sr 2+ and Ca 2+. We have also found that dioxo[13]aneN 4 is an effective additive in CE to resolve nitrophenols and, in particular, dihydroxybenzenes. Moreover, unlike previous reports, the separation of various biogenic monoamine neurotransmitters can be achieved at neutral or physiological pH. This work demonstrates that one of the macrocyclic dioxopolyamine derivatives: dioxo[13]aneN 4 is a promising additive in CE separations for any chemical species: cationic, anionic and neutral.