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The Sulfo-NHS ester is a mainstay reagent for facilitating amide bond formation between carboxylic acids and amine functionalities in water. However, the preparation of Sulfo-NHS esters currently requires hydrophobic carboxylic acids, which are poorly water-soluble, to first be reacted with the N -hydroxysulfosuccinimide sodium salt, which is insoluble in organic solvents. The mutually incompatible solvation requirements thus complicate the synthesis of Sulfo-NHS esters. As a simple, rapid, and cost-effective solution to this problem, we report that the use of 15-crown-5 to complex the sodium cation of N -hydroxysulfosuccinimide sodium salt circumnavigates these solvation incompatibility issues by rendering the N -hydroxysulfosuccinimide salt soluble in organic solvents, resulting in a cleaner esterification reaction and thus improved yields of activated ester product. We also demonstrate that the resultant "crowned" Sulfo-NHS-ester remains water-soluble and is no less reactive than its classic "uncrowned" Sulfo-NHS counterpart when used in bioconjugation reactions between protein amine-functionalities and hydrophobic carboxylic acids.

We report the synthesis of crown ether-ammonium, amide and amine [2]rotaxanes via transition state stabilization of axle-forming reactions. In contrast to the two-step "clipping" and "capping" strategies generally used for rotaxane synthesis, here the components assemble into the interlocked molecule in a single, reagent-less, step under kinetic control. The crown ether accelerates the reaction of the axle-forming components through the cavity to give the threaded product in a form of metal-free active template synthesis. Rotaxane formation can proceed through the stabilization of different transition states featuring 5-coordinate (e.g., SN2) or 4-coordinate (e.g., acylation, Michael addition) carbon. Examples prepared using the approach include crown-ether-peptide rotaxanes and switchable molecular shuttles. [ABSTRACT FROM AUTHOR]

Alkali metal cations (Na+, K+) and crown ether molecules (12C4, 15C5, 18C6) were used as additional reactants during the hydrothermal synthesis of uranyl ion complexes with cis/trans-1,3-, cis-1,2- and trans-1,2-cyclohexanedicarboxylic acids (c/t-1,3-chdcH2, c-1,2-chdcH2, and t-1,2-chdcH2, respectively, the latter as racemic or pure (1R,2R) enantiomer). Oxalate anions generated in situ are present in all the six complexes isolated and crystallographically characterized, [(UO2)2(c-1,3-chdc)2(C2O4)][UO2(H2O)5]·(12C4)·2H2O (1), [(UO2)4Na2(c-1,2-chdc)2(C2O4)3(15C5)2] (2), [(UO2)4K2(c-1,2-chdc)2(C2O4)3(18C6)1.5(H2O)1.5] (3), [(UO2)12K5(R-t-1,2-chdc)4(C2O4)10(18C6)5(OH)(H2O)3]·4H2O (4), [(UO2)12K5(rac-t-1,2-chdc)4(C2O4)10(18C6)5(OH)(H2O)3]·4H2O (5), and [(UO2)8K4(rac-t-1,2-chdc)4(C2O4)6(18C6)3(H2O)2] (6). In complex 1, the [UO2(H2O)5]2+ counterions link the ladderlike uranyl-containing one-dimensional polymers and the uncomplexed crown ether molecules through hydrogen bonds. In all the other complexes, two-dimensional uranyl/chdc/oxalate subunits are formed, with topologies depending on the stoichiometry, in which the 1,2-chdc2- ligands are bound to three uranium atoms, one of them chelated by the two carboxylate groups, and the oxalate ligands are bis-chelating. In complex 2, the Na(15C5)+ cations are bound to one layer through double Na-carboxylate or Na-oxo cis-bonding and they are thus mere decorating groups. In contrast, the quasi-planar K(18C6)+ groups in 3-6, partially affected by disorder, are generally trans-coordinated to two uranyl oxo groups pertaining to different layers, thus uniting the latter into a three-dimensional framework. [ABSTRACT FROM AUTHOR]

Crown ether decorated phthalocyanines were designed to form rigidly eclipsed aggregates with metal ions being sandwiched between the molecules. We studied tetra-[18]crown-6 ether functionalized zinc phthalocyanine (ZnPcTetCr) in the presence of excess NaCl by electrospray ionization mass spectrometry. ZnPcTetCr was found to form aggregates in the gas phase to which several neutral NaCl molecules are attached. Collision-induced dissociation experiments revealed that the ions observed in the positive- and negative-ion modes possess remarkably different structures. Their fragmentation behavior indicates that the sodium ions providing the charge of the positively charged aggregates are strongly bound inside the crown ether moieties, while the neutral salt units are less strongly attached. However, in the negatively charged ions, none of the sodium ions is embedded in the crown ether moieties, and the NaCl molecules were found to be attached as one large, weakly bound cluster. [ABSTRACT FROM AUTHOR]

Ionic liquid/crown ether compositions are an attractive alternative to traditional extractants in the processes for spent nuclear fuel and liquid radioactive wastes reprocessing. These compositions are exposed to ionizing radiation and their radiation stability, especially in the presence of metal salts, is a crucial issue. In the present study, the macrocyclic 18C6·Sr(BF4)2 and 18C6·Sr(PF6)2 complexes simulating the components of metal loaded ionic liquid/crown ether extractants were synthesized and their structures were characterized by FTIR spectroscopy and single-crystal X-ray diffraction analysis. Inclusion of Sr2+ cation into the 18C6 cavity resulted in more symmetric D3d conformations of the macrocycle. The structural transformations of the crown ether were accompanied by an elongation of polyether C--O bonds that could increase the possibility of radiolytic cleavage of the macrocycle. However, EPR study of the synthesized compounds subjected to X-ray irradiation revealed predominant formation of macrocyclic -CH2-ĊH-O- radicals. This result demonstrated an evidence for indirect action of ionizing radiation on individual components of the complexes and was reasonably described by a positive "hole" transfer from primary macrocyclic radical cation to fluorous anion at the primary stages of radiolysis and a subsequent interaction of fluorine atom with 18C6 macrocycle in secondary radical reactions. The observed effects may be partially responsible for enhanced sensitivity of the ionic liquid/crown ether extractants to ionizing radiation due to chemical blocking of the crown ether with radiolytic HF, radiation-chemical degradation of the 18C6 and precipitation of a low-soluble SrF2. [ABSTRACT FROM AUTHOR]

The first convex cesium-bound complex with a bowl-shaped carbanion, namely [{Cs+(dc-18-crown-6)}(C21H11-)] (1), has been isolated and crystallographically characterized. In the structure of 1, the cesium ion capped by dicyclohexano-18-crown-6 ether coordinates to the deprotonated five-membered ring of a sumanenyl bowl in an exo fashion with the Cs•••C distances ranging from 3.315(5) to 3.609(6) Å. Theoretical modeling, including a topological QTAIM approach, reveals the cumulative effect of multiple weak CH•••π interactions between the cationic {Cs+(dc-18-crown-6)} moiety and the convex surface of the C21H11- anion, explaining the formation and stability of the product. [ABSTRACT FROM AUTHOR]

We describe here a modularly tunable molecular strategy for construction and combinatorial optimization of highly efficient K+-selective channels. In our strategy, a highly robust supramolecular H-bonded 1D ensemble was used to order the appended crown ethers in such a way that they roughly stack on top of each other to form a channel for facilitated ion transport across the membrane. Among 15 channels that all prefer K+ over Na+ ions, channel molecule 5F8 shows the most pronounced optimum for K+ while disfavoring all other biologically important cations (e.g., Na+, Ca2+ and Mg2+). With a K+/Na+ selectivity of 9.8 and an EC50 value of 6.2 µM for K+ ion, 5F8 is clearly among the best synthetic potassium channels developed over the past decades. [ABSTRACT FROM AUTHOR]

We discover that the crystal morphology of zeolite-LTL could be modified by crown ether (21-crown-7, CE), where CE decreases the aspect ratio of zeolite-LTL while increasing the nucleation of domains on the (0001) face and hindering their growth along the c-axes. Moreover, the study using scanning electron microscopy supports that the ratio between the rates for generation of cancrinite columns and bridging cancrinite columns on the {1010} face remains constant among the LTL frameworks with different amounts of CE molecules. In addition, X-ray diffraction analysis shows that potassium cations redistribute into pore cavities (t-lil) from cancrinite cages (t-can) and t-ste cages by the strong interactions between potassium and CE as the amount of CE molecules is increased. Additionally, Monte Carlo simulations clarify that stabilization of the t-lil cage via the redistribution of potassium cations at high CE concentration is attributed to the dominant effect in the crystal morphology changes observed. To understand the catalytic and adsorption properties of zeolites, it is important to investigate their structure/property relationships. Especially, studying the morphology of an anisotropic zeolite crystals has been of great interest because of the strong influence on controlling its properties. Thus, morphological control of the material with a particular crystallographic direction is highly desirable to obtain maximum properties for applications. [ABSTRACT FROM AUTHOR]

Crown-ethers have recently been used to assemble porous liquids (PLs), which are liquids with permanent porosity formed by mixing bulky solvent molecules (e.g., 15-crown-5 ether) with solvent-inaccessible organic cages. PLs and crown-ethers belong to a novel class of materials, which can potentially be used for gas separation and storage, but their performance for this purpose needs to be assessed thoroughly. Here, we use molecular simulations to study the gas separation performance of crown-ethers as the solvent of porous liquids. The TraPPE force field for linear ether molecules has been adjusted by fitting a new set of torsional potentials to accurately describe cyclic crown-ether molecules. Molecular dynamics (MD) simulations have been used to compute densities, shear viscosities, and self-diffusion coefficients of 12-crown-4, 15-crown-5, and 18-crown-6 ethers. In addition, Monte Carlo (MC) simulations have been used to compute the solubility of the gases CO2, CH4, and N2 in 12-crown-4 and 15-crown-5 ether. The computed properties are compared with available experimental data of crown-ethers and their linear counterparts, i.e., polyethylene glycol dimethyl ethers. [ABSTRACT FROM AUTHOR]

The first arylogous Michael reaction of 3-aryl phthalides has been developed. The reaction, promoted by catalytic amounts of KOH or K3PO4 and dibenzo-18-crown-6, affords the corresponding 3,3-disubstituted phthalides in good to high yields and as single diastereomers in nearly all studied cases. [ABSTRACT FROM AUTHOR]

This paper reports on a theoretical analysis of the electronic structure and magnetic properties of the [Ni(dmit)2]- radical anions in four salt compounds resulting from the combination with supramolecular cation-crown ether assemblies. The selected compounds are representative examples of the diversity of stacking patterns and magnetic behaviors found for systems based on these [Ni(dmit)2]- anions. Difference Dedicated Configuration Interaction calculations have been performed on fragments containing two neighbor [Ni(dmit)2]- units to evaluate the intradimer, interdimer, and interchain magnetic coupling constants and analyze the electronic structure of the [Ni(dmit)2]- ions. The amplitude and sign of these through-space interactions are consistent with the structure and arrangement of the [Ni(dmit)2] monomers in the chain and the overlap and transfer integral between the magnetic orbitals. They accurately simulate the thermal dependence of the magnetic susceptibility but do not agree with the reported J values in two of the systems, both composed by chains of weak dimers. These results highlight the nonunivocal nature of the fitting in complex systems and the difficulties in defining interaction spin models solely based on the quality of the resulting curves. This work shows the limitations of the extended Hückel calculations on the interpretation of the main ingredients of the magnetism and the relevance of reference theoretical calculations as a complementary tool for the understanding of the magnetic behavior of [Ni(dmit)2]-based functional materials. [ABSTRACT FROM AUTHOR]

Conspectus: The relationship between fundamental and applied is often uneasy, particularly in modern political climates. A familiar political view, aimed negatively at the scientific community, is that the former is a waste of money whereas the latter gives value for investment. The answer that fundamental is required as the basis for practical suffers from the fact that the timelines between fundamental and practical are often long and the routes contorted and unexpected. This has been my experience. In this Account, examples are given from the research in which I have been involved wherein quite fundamental considerations have led to various applications. The longer the time, the clearer and broader the relationship. Fundamental can and does lead to application. They need and depend on each other. I have seen this both from the side of academia and from small companies. In the course of the past 40 plus years, I have been involved in various aspects of stereochemistry and, in particular, chirality. It has been rewarding to see that several of the developments, most originally grounded in fundamental research considerations, have been used in the chemical community and given new dimensions and often practical applications by others. In this Account, a path-not planned deliberately by me from orbital symmetry and Woodward-Hoffmann rules through crown ethers to conformational analysis to diastereomeric resolutions to deracemizations powered by Ostwald ripening and the Gibbs-Thomson effect to nucleation to helicenes is described. In order of discussion, the orbital symmetry aspects have via an unusual and unpredicted path has resulted in, among other things, a synthesis of hindered alkenes useful for the production of molecular motors. The crown ether aspects led to discovery of the utility of cesium salts particularly for racemization sensitive nucleophilic substitutions. Work on diastereomeric resolutions has concentrated on the mechanistic as well as practical/commercial aspects of the use of multiple resolving agents (Dutch resolution). During this work the complex relationship between nucleation and chirality in diastereomeric resolutions began to reveal itself. In general, nucleation, especially with involvement of chirality, is a topical challenge that has attracted the attention of many groups. The contribution of this knowledge to the development of attrition driven deracemizations of racemizable conglomerates is described. This remarkable technology allows, without intervention of chiral aids, conversion of certain racemates in quantitative yield and absolute enantiomeric excess to a single enantiomer. From a practical standpoint, this methodology has been used for the production in enantiomerically pure form of commercially interesting compounds like naproxen and clopidogrel (Plavix). Finally an STM investigation of the nucleation behavior of a helicene, prepared via a remarkably short and efficient route, on a metal surface is described. [ABSTRACT FROM AUTHOR]

We measure UV photodissociation (UVPD) spectra of benzo-12-crown-4 (B12C4) complexes with alkali metal ions, M+·B12C4 (M = Li, Na, K, Rb, and Cs), in the 36300-37600 cm-1 region. Thanks to the cooling of ions to 10 K, all the M+·B12C4 complexes show sharp vibronic bands in this region. For UV-UV hole-burning (HB) spectroscopy, we first check if our experimental system works well by observing UV-UV HB spectra of the K+ complex with benzo-18-crown-6 (B18C6), K+·B18C6. In the UV-UV HB spectra of the K+·B18C6 complex, gain signals are also observed; these are due to vibrationally hot K+·B18C6 complex produced by the UV excitation of cold K+·B18C6 complex. Then we apply UV-UV HB spectroscopy to the M+·B12C4 complexes, and only one conformer is found for each complex except for the Li+ complex, which has two conformers. The vibronic structure around the origin band of the UVPD spectra is quite similar for all the complexes, indicating close resemblance of the complex structure. The most stable structures calculated for the M+·B12C4 (M = Li, Na, K, Rb, and Cs) complexes also have a similar conformation among them, which coincides with the UVPD results. In these conformers the metal ions are too big to be included in the B12C4 cavity, even for the Li+ ion. In solution, it was reported that 12-crown-4 (12C4) shows the preference of Na+ ion among alkali metal ions. From the similarity of the structure for the M+·B12C4 complexes, it is suggested that the solvation of free metal ions, not of the M+·12C4 complexes, may lead to the selectivity of Na+ ion for 12C4 in solution. [ABSTRACT FROM AUTHOR]

In this article, our aim is to investigate the interaction of l-phenylalanine (l-Phe) fibrils with crown ethers (CEs). For this purpose, two different CEs (15-Crown-5 (15C5) and 18-Crown-6 (18C6)) were used. Interestingly, we have observed that both CEs have the ability to arrest fibril formation. However, 18C6 was found to be a better candidate compared to 15C5. Field emission scanning electron microscopy and fluorescence lifetime imaging microscopy were used to monitor the fibril-arresting kinetics of CEs. The arresting process was further confirmed by fluorescence correlation spectroscopy and nuclear magnetic resonance studies. [ABSTRACT FROM AUTHOR]

The interaction of the three-mercury anticrown (o-C6F4Hg)3 (1) with [PPh4][BF4] in methanol at room temperature leads to fluoride anion transfer from BF4- to 1 with the formation of a fluoride complex, [PPh4]{[(o-C6F4Hg)3]2F}, having a double-decker sandwich structure. The fluoride ion in this unique adduct is disposed between the mutually parallel planes of the central nine-membered rings of the anticrown units and cooperatively coordinated by all six Hg sites. The iodide anion also forms a double-decker sandwich in the interaction with 1, but this sandwich, [PPh4]{[(o-C6F4Hg)3]2I}, has a wedge-shaped geometry. The reaction of 1 with [nBu4N]Cl in dibromomethane at -15 °C affords a complex, [nBu4N]{[(o-C6F4Hg)3]2Cl(CH2Br2)2}, containing one chloride anion and two coordinated CH2Br2 species per two molecules of 1. A similar bromide complex of 1, containing two coordinated CH2Br2 moieties, has also been synthesized and structurally characterized. Both compounds represent wedge-shaped double-decker sandwiches wherein the halide anion is simultaneously bonded to all Hg centers of the anticrown molecules. The dibromomethane species in the isolated adducts are also arranged in the space between the mercuramacrocycles. One of these species is coordinated by each of its bromine atoms to a single Hg site of the adjacent macrocycle while the other interacts by only one bromine atom with a Hg center of the neighboring molecule of 1. [ABSTRACT FROM AUTHOR]

Several new iridium(I) and iridium(III) carbonyl complexes supported by aminophosphinite pincer ligands have been prepared and characterized. A surprising diversity of reaction pathways was encountered upon treatment of Ir carbonyl complexes with Li+, Na+, Ca2+, and La3+ salts. Iridium(III) hydridocarbonyl chloride complexes underwent either halide abstraction or halide substitution reactions, whereas iridium(I) carbonyl complexes underwent protonative oxidative addition reactions. When the nitrogen donor of the pincer ligand is an aza-crown ether macrocycle, cation-macrocycle interactions could be supported, leading to divergent reactivity in some cases. [ABSTRACT FROM AUTHOR]

Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from =10-4 to 0.38. The latter value is unusually high for olefins in solution. [ABSTRACT FROM AUTHOR]

Acrylamide-acrylamide nucleic acids are cross-linked by two cooperative functional motives to form shaped acrylamide-DNA hydrogels. One of the cross-linking motives responds to an external trigger, leading to the dissociation of one of the stimuliresponsive bridges, and to the transition of the stiff shaped hydrogels into soft shapeless states, where the residual bridging units, due to the chains entanglement, provide an intrinsic memory for the reshaping of the hydrogels. Subjecting the shapeless states to counter stimuli restores the dissociated bridges, and regenerates the original shape of the hydrogels. By the cyclic dissociation and reassembly of the stimuli-responsive bridges, the reversible switchable transitions of the hydrogels between stiff shaped hydrogel structures and soft shapeless states are demonstrated. Shaped hydrogels bridged by K+-stabilized Gquadruplexes/ duplex units, by i-motif/duplex units, or by two different duplex bridges are described. The cyclic transitions of the hydrogels between shaped and shapeless states are stimulated, in the presence of appropriate triggers and counter triggers (K+ ion/crown ether; pH = 5.0/8.0; fuel/antifuel strands). The shape-memory hydrogels are integrated into shaped two-hydrogel or three-hydrogel hybrid structures. The cyclic programmed transitions of selective domains of the hybrid structures between shaped hydrogel and shapeless states are demonstrated. The possible applications of the shapememory hydrogels for sensing, inscription of information, and controlled release of loads are discussed. [ABSTRACT FROM AUTHOR]

The aggregation of phthalocyaninesis well-known in solution but has never before been studied in thegas phase. We investigated the tetra-[18]crown-6 ether functionalizedzinc–phthalocyanine (ZnPcTetCr, M) with electrosprayionization mass spectrometry (ESI-MS) in the absence of coordinatingmetal cations. Apart from the molecular ion M+•, singly and multiply charged aggregates Mnz(+•)were observed,bound together by electrostatic interactions, without alkali metalcations inside the crown ethers. Collision-induced dissociation (CID)experiments indicate that these clusters consist of stacked neutral Mand radical cations M+•.After the oxidation of individual molecules at the electrospray needle,the aggregation occurs during desolvation of the charged dropletscreated in the source. Complete evaporation of the solvent and detectionof the aggregates was found to require an additional accelerationof the droplets in the transfer region of the instrument, the resultingcollisions with neutral gas assisting the desolvation process. [ABSTRACT FROM AUTHOR]

A detailed thermodynamicanalysis of the axle-wheel binding indi- and trivalent secondary ammonium/[24]crown-8 pseudorotaxanes ispresented. Isothermal titration calorimetry (ITC) data and doublemutant cycle analyses reveal an interesting interplay of positiveas well as negative allosteric and positive chelate cooperativitythus providing profound insight into the effects governing multivalentbinding in these pseudorotaxanes. [ABSTRACT FROM AUTHOR]

Themetallathiacrown ethers cis-Mo(CO)4{2,2′-(C12H8O2)PO(CH2CH2S)nCH2CH2OP(2,2′-(O2H8C12))} (n= 2, 3)and cis-Mo(CO)4{2,2′-(C12H8O2)POCH2CH2S-1-(C6H4)-2-SCH2CH2OP(2,2′-(O2H8C12))} have been prepared as softmetal selective molecular receptors.Multinuclear NMR spectroscopy and X-ray crystallography have beenused to show that byproducts formed during the syntheses of the metallathiacrownethers cis-Mo(CO)4{2,2′-(C12H8O2)PO(CH2CH2S)nCH2CH2OP(2,2′-(O2H8C12))} (n= 2, 3)are homobinuclear complexes with cis-Mo(CO)4(P-donor)(S-donor) centers. The abilities of the metallathiacrownethers to bind PdCl2and PtCl2have been assessedusing 31P{1H} NMR spectroscopy and X-ray crystallography.The complexes showed null results with PdCl2; however,the PtCl2experiments showed that the complexes cis-Mo(CO)4{2,2′-(C12H8O2)PO(CH2CH2S)nCH2CH2OP(2,2′-(O2H8C12))} (n= 2, 3)formed heterobinuclear cis,cis-{[Mo(CO)4{2,2′-(C12H8O2)PO(CH2CH2S)nCH2CH2OP(2,2′-(O2H8C12))}]PtCl2} (n= 2, 3) complexes. The 31P{1H} NMR spectra of these complexes suggest a cis-PtS2Cl2coordination environmentin each, which leads to asymmetric binding in the latter complex.Binding of HgCl2by the complexes cis-Mo(CO)4{2,2′-(C12H8O2)PO(CH2CH2S)nCH2CH2OP(2,2′-(O2H8C12))} (n= 2, 3) has been studied using 31P{1H} NMR spectroscopy. Each complex was titrated withHgCl2, and the quantitative shifts in the 31P{1H} NMR spectra were fit to a binding mechanism. The n= 2 metallathiacrown ether binds HgCl2to forma 1:1 complex with Ka= 12.0(0.2) M–1. In contrast, interaction of HgCl2withthe n= 3 metallathiacrown ether results in isomerizationto the trans complex, and HgCl2binds to both isomers.A model has been adapted to fit the titration data of this complexand to extract equilibrium constants for each step in the cycle: thecis–trans equilibrium of the free, Kfree(0.570 (0.004)), and bound, Kbound(0.16(0.03)), metallathiacrown ethers, as well as the association bindingconstants for the cis, Kcis([4.1(0.3)]× 102M–1) and trans, Ktrans([1.1(0.2)] × 102M–1), metallathiacrown ethers. The equilibrium constants demonstratethat the cis metallathiacrown ether binds more strongly to the HgCl2than does the trans metallathiacrown ether and that the cis–transequilibrium favors the cis metallathiacrown ether. [ABSTRACT FROM AUTHOR]

A novel tricylic host molecule 1 that consists of two pillar[5]arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane G1 and paraquat G2, with its two macrocyclic subunits, to form a four-component complex 2G1⊂1⊃G2. An ¹H NMR study of stepwise bindings of G1 and G2 to host 1 in CDCl3/DMSO-d6 revealed that the strength of the association between complex 2G1⊃1 and guest G2 was only one-fourth of that between free 1 and G2, demonstrating a negative heterotropic cooperativity of G1 in the binding of G2 to host 1. [ABSTRACT FROM AUTHOR]

The motions of biomolecular machines are usually multistep processes, and are involved in a series of conformational changes. In this paper, a novel triply interlocked [2](3)catenane composed of a tris(crown ether) host eTC and a circular ditopic guest with three dibenzyl ammonium (DBA) sites and three N-methyltriazolium (MTA) sites was reported. Due to the multivalency nature of the catenane, the acid-base triggered motion was performed by a stepwise manner. The coconformations of the four related stable states have been directly identified and quantified which confirmed the multistep process. In order to quantify the dynamics with environmental acidity changes, the values of the three levels of dissociation constant pKa have been determined. The special interlocked topology of the [2](3)catenane also endows the motion of each crown ether ring in the host with unexpected selectivity for the MTA sites. This study provides clues to comprehend the underlying motion mechanism of intricate biological molecular machines, and further design artificial molecular machine with excellent mechanochemistry properties. [ABSTRACT FROM AUTHOR]

A pillar[5]arene-crown ether fused bicyclic host 1 was found to be able to recognize an imidazolium ion G1 by its pillar[5]arene subunit and a viologen ion G2 by its crown ether receptor discriminatively. The simultaneous binding of G1 and G2 by 1 resulted in the formation of a three-component host-guest complex G11G2. Negative heterotropic cooperative effects were displayed by G1 and G2 in their binding to 1 and were investigated by stepwise bindings of G1 and G2 to 1. [ABSTRACT FROM AUTHOR]

A novel polymer polysulfone (PSF)-graft-4′-aminobenzo-15-crown-5-ether(AB15C5) (PSF-g-AB15C5) for lithium isotope separationwas prepared from PSF and AB15C5 as starting materials via nucleophilicsubstitution reaction. The chemical structure and properties of PSF-g-AB15C5 polymers were characterized by FT-IR, 1H NMR, XPS, and TGA. The polymers obtained were used for lithiumisotope separation by solid–liquid extraction. The effectsof the immobilization amount of crown ether grafting on PSF, the typeof counteranion of lithium salt, and the kind of solvent on the singlestage separation factor were explored. Results showed that the singlestage separation factor was only 1.002 ± 0.002 for AB15C5 inthe traditional liquid–liquid extraction system of H2O–LiCl/CHCl3–AB15C5, whereas the singlestage separation factor increased from 1.003 ± 0.001 to 1.015± 0.002 with the increase of the immobilization amount of crownether from 0.23 to 0.79 mmol g–1on PSF-g-AB15C5 polymers in the solid–liquid extractionsystem of CH3OH–LiCl/PSF-g-AB15C5polymers. The order of the single stage separation factor obtainedin different lithium salts was LiI > LiBr > LiClO4> LiCl.Further, the maximum value of single stage separation factor was 1.031± 0.002 for the extraction system of CH3NO2–LiCl/PSF-g-AB15C5 polymers. Moreover, 6Li and 7Li were enriched in the polymer phase andthe solution phase, respectively. [ABSTRACT FROM AUTHOR]

In-depth investigations of the specificion-responsive characteristicsbased on 2:1 “sandwich” structures and effects of crownether cavity sizes on the metal-ion/crown-ether complexation are systematicallyperformed with a series of PNIPAM-based responsive copolymers containingsimilar contents of crown ether units with different cavity dimensions(12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lowercritical solution temperature (LCST) values of copolymers in deionizedwater shift to lower temperatures gradually when the crown ether contentsincrease or the ring sizes decrease from 18C6 to 12C4. With increasingthe concentrations of alkali metal ions (Na+, K+, Cs+) or the contents of pendent crown ether groups,the copolymers with different crown ether cavity sizes exhibit higherselectivity and sensitivity to corresponding cations. Importantly,the ion sensitivities of the copolymers in response to correspondingalkali metal ions increase dramatically with an increase in the crownether cavity size. Interestingly, a linear relationship between thecrown ether cavity size and the diameter of corresponding cation forthe formation of stable 2:1 “sandwich” complexes isfound for the first time, from which the size of metal ions or otherguests that able to form 2:1 “sandwich” complexes withcrown ethers can be deduced. The results in this work are valuableand useful for further developments and practical applications ofvarious crown-ether-based smart materials. [ABSTRACT FROM AUTHOR]

The synthesis of new styryl dyes derived from 4-pyridine and 4-quinoline and having an ammonioalkyl N-substituent and benzocrown ether moieties of different sizes and with different sets of heteroatoms was developed. Spontaneous "head-to-tail" dimerization of these dyes via the formation of numerous hydrogen bonds between the terminal NH3+ groups and crown ether moieties was detected in MeCN solutions. The stability constants of the dimeric complexes having pseudocyclic structure were studied by ¹H NMR titration. The most stable complexes (log Kd up to 8.2) were found in the case of dyes with the 18-crown-6 ether moiety, which is most complementary for binding a primary ammonium group. Stacking interaction of the conjugated systems in the dimeric complexes contributes to their stability to a much lesser extent. In dimeric complexes, the ethylene bonds of the dyes are preorganized for stereospecific [2 + 2] photocycloaddition (PCA) induced by visible light. PCA yields only rctt isomers of bis-crown-containing cyclobutane derivatives. The dyes were studied by X-ray diffraction; it was found that the dimeric arrangement is also retained in the crystalline state. The possibility of topochemical PCA of the dyes in single crystals without their destruction was demonstrated. The possibility of retro-PCA of the obtained cyclobutane derivatives to give the starting dyes was shown. The elucidated regularities of PCA can be used to fabricate optical data recording systems based on ammonioalkyl derivatives of crown ether styryl dyes. [ABSTRACT FROM AUTHOR]

With the continual development of lanthanides (Ln) in current technological devices, an efficient separation process is needed that can recover greater amounts of these rare elements. Dicyclohexano-18-crown-6 (DCH18C6) is a crown ether that may be a promising candidate for Ln separation, but additional research is required. As such, molecular dynamics (MD) simulations have been performed on four divalent lanthanide halide salts (Sm 2+ , Eu 2+ , Dy 2+ , and Yb 2+ ) and one divalent actinide halide salt (Cf 2+ ) bound to three diastereoisomers of DCH18C6. Dy 2+ , Yb 2+ , Cf 2+ , DCH18C6, and tetrahydrofuran (THF) solvent were parameterized for the AMOEBA polarizable force field for the first time, whereas existing parameters for Sm 2+ and Eu 2+ were utilized from our previous efforts. A coordination number (CN) of six for Ln 2+ /An 2+ -O solvated in THF indicated that the cations interacted almost entirely with the oxygens of the polyether ring. A CN of one for Ln 2+ /An 2+ -N solvated in acetonitrile for systems containing iodide suggested that the N atom of acetonitrile was competitive with I - for cation interactions. Fluctuation between five and six CNs for Dy 2+ and Yb 2+ suggested that although the cations remained in the polyether ring, the size of the ring may not be an ideal fit as these cations possess comparatively smaller ionic radii. Gibbs binding free energies of Sm 2+ in all DCH18C6 diastereoisomers solvated in THF were calculated. The binding free energy of the cis-syn-cis diastereoisomer was the most favorable, followed by cis-anti-cis , and then trans-anti-trans . Finally, two major types of conformation were observed for each diastereoisomer that were related to the electrostatic interactions and charge density of the cations.

A protocol for the stereodivergent pentafluoroethylation of N -sulfinylimines using HFC-125 with KHMDS/triglyme has been developed. Both diastereomers of the pentafluoroethylated amines can be selectively synthesized based on the presence or absence of triglyme. This additive-controlled protocol allows the KHMDS/triglyme cryptate to be a straightforward and cheap alternative to previously reported base-controlled stereodivergent trifluoromethylation using potassium hexamethyldisilazide (KHMDS) versus P 4 - t Bu.

Sodiumand potassium complexes supported by a bulky monophenoxy with onexanthenyl group at the ortho-position and 18-crown-6 or 15-crown-5as an auxiliary ligand were synthesized and characterized. These complexesare highly iso-selective and active catalysts for the controlled ring-openingpolymerization of rac-lactide. The best isotacticity(Pm) achieved was 0.86, which is the highestiso-selectivity reported to date for an alkali-metal complex. In addition,the corresponding polymer exhibited a high Tmof 182 °C. Furthermore, the polymerization looks likean anti-Arrhenius reaction, which is slower at high temperatures thanat low temperatures. [ABSTRACT FROM AUTHOR]

Sterically congested o-terphenyl crown ethers with alkoxy substituents at the 2,3,4-position or 3,4,5-position were synthesized from the corresponding tetrabromodibenzo[15]crown-5 and the corresponding boronic acids or borolanes via Suzuki cross-coupling and subsequently cyclized to the corresponding triphenylenes utilizing the Scholl reaction. Both series of compounds were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction (SAXS, WAXS) regarding their mesomorphic properties. While all but one of the 3,4,5-substituted derivatives displayed liquid crystalline behavior (Colh and Colr), only the 2,3,4-substititued triphenylene with the shortest alkoxy chains was liquid crystalline (Colr). [ABSTRACT FROM AUTHOR]

Stable layers of crown ethers weregrown on muscovite mica usingthe potassium–crown ether interaction. The multilayers weregrown from solution and from the vapor phase and were analyzed withatomic force microscopy (AFM), matrix-assisted laser desorption/ionizationtime-of-flight (MALDI-TOF) mass spectrometry, and surface X-ray diffraction(SXRD). The results show that the first molecular layer of the threeinvestigated dibenzo crown ethers is more rigid than the second becauseof the strong interaction of the first molecular layer with the potassiumions on the surface of muscovite mica. SXRD measurements revealedthat for all of the investigated dibenzo crown ethers the first moleculelies relatively flat whereas the second lies more upright. The SXRDmeasurements further revealed that the molecules of the first layerof dibenzo-15-crown-5 are on top of a potassium atom, showing thatthe binding mechanism of this layer is indeed of the coordinationcomplex form. The AFM and SXRD data are in good agreement, and thecombination of these techniques is therefore a powerful way to determinethe molecular orientation at surfaces. [ABSTRACT FROM AUTHOR]

A tetra-armed cyclen bearing two benzo-15-crown-5 ethers in the side arms (1) is reported. When 1 equiv of Ag+ is added to 1, the aromatic side arms cover the Ag+ incorporated in the cyclen. Upon the addition of more than 1 equiv of Ag+ to 1, the cyclen moiety binds Ag+ first, before the crown ether in the side arms subsequently binds Ag+. The log K11, log K12, and log K13 values for the 1:1, 1:2, and 1:3 (= 1/Ag+) complexes were estimated to be 9.4, 5.8, and 4.0, respectively. We found that the tetra-armed cyclen possessing crown ethers in the side arms behaves like an argentivorous molecule even though the crown ether arms bind metal cations. [ABSTRACT FROM AUTHOR]

Three potassium crown ether salts, [K- (Et2O)2(18-crown-6)][Fe{N(SiMe3)Dipp}2] (la; Dipp = C6H3-2,6-Pri2) [K(18-crown-6)] [Fe{N(SiMe3)Dipp}2]-. 0.5phMe(lb ), and [K(l8-crown-6)][M{N(SiMe3)Dipp}2]- (M =Co, 2; M = Ni, 3), of the two-coordinate linear or near-linear bis-amido monoanions [M{N(SiMe3)Dipp}2]- (M = Fe, Co, Ni) were synthesized by one-electron reduction of the neutral precursors M{N(SiMe3)Dipp}² with KC8 in the presence of 18- crown-6. They were characterized by X-ray crystallography, UV--vis spectroscopy, cyclic voltammetry, and magnetic measurements. The anions feature lengthened M--N bonds in comparison with their neutral precursors, with slightly bent coordination (N--Fe--N = ca.172°) for the iron(I) complex, but linear coordination for the cobalt(l) and nickel(l) complexes. Fits of the temperature dependence of %MT of 1 and 2 reveal that the iron(l) and cobalt(l) complexes have large negative D zero-field splittings and a substantial orbital contribution to their magnetic moments with L = 2, whereas the nickel(l) complex has at most a small orbital contribution to its magnetic moment The magnetic results have been used to propose an ordering of the 3d orbitals in each of the complexes. [ABSTRACT FROM AUTHOR]

Densityfunctional theoretical calculation was performed to understandthe isotopic fraction of zinc in the nano cavity of different crownethers and crown ethers anchored on solid resin matrix. The structure,energetic, thermodynamics, and vibration IR spectra were also evaluated.The gas phase binding energy of Zn2+with crown ether ofvaried cavity can be correlated with NPA charge transfer but no suchcorrelation is obtained with the fraction of electron transfer, ΔN. The reduced partition function ratio (RPFR) of complexesof Zn2+ion with different solvents, crown ethers, andgrafted crown ethers was also computed to predict the isotope separationfactor of the Zn2+ion. The present study reveals thatwith increasing cavity size of the crown ether the RPFR was foundto be decreased leading to a high value of isotope separation factoras observed in the experiments. An attempt was made to correlate thecalculated RPFR and separation factor with binding energy of differentzinc-crown ether systems. Further, it is shown that the smaller thesolvation energy of the metal ion the higher will be distributionconstant of Zn2+ion as confirmed by experiments indicatingsolvents with low dielectric constant should be used for chromatographicseparation process. The present study should be useful in screeningthe nano cavity based grafted resin and for future development ofnew grafted materials for Zn and other isotope separation. [ABSTRACT FROM AUTHOR]

A novel bistable symmetric [2](2)rotaxane was prepared by a threading-followed-by-stoppering strategy and characterized with ¹H, 13C, and 2D ROESY NMR spectroscopy and HR-ESI spectrometry. The symmetric [2](2)rotaxane system consists of an anthracene-based bis(crown ether) as macrocycles, and each of the two dibenzo[24]crown-8 (DB24C8) rings is threaded by the pendant substituents of a symmetrically substituted central rotatable ferrocene subunit that possesses two distinguishable recognition sites for the DB24C8 ring: namely, a dibenzylammonium site and an N-methyltriazolium site. The uniform shuttling motion of the thread relative to the two DB24C8 rings in [2](2)rotaxane can be driven by external acid--base stimuli, which was evidenced by ¹H and 2D ROESY NMR spectroscopy. Furthermore, molecular dynamics simulations of the [2](2)rotaxane were carried out both in protonated (stretched) and in neutral (contracted) forms. The calculated percentage change in molecular length of the [2](2)rotaxane between the two end-capping bis(methoxyl)phenyl groups is about 48% in the two different states (in acetone), which is much larger than the percentage change ( 27%) in human muscle. Moreover, in the two states, the C*--Cp--Cp--C* dihedral angles are computed as -177° in the stretched state and -112° in the contracted state, indicating a correlation between the translational and rotational motions of the [2](2)rotaxane. [ABSTRACT FROM AUTHOR]

Improved methods for quickly identifying neutral organic compounds and differentiation of analytes with similar chemical structures are widely needed. We report a new approach to effectively “fingerprint” neutral organic molecules by using 19F NMR and molecular containers. The encapsulation of analytes induces characteristic up- or downfield shifts of 19F resonances that can be used as multidimensional parameters to fingerprint each analyte. The strategy can be achieved either with an array of fluorinated receptors or by incorporating multiple nonequivalent fluorine atoms in a single receptor. Spatial proximity of the analyte to the 19F is important to induce the most pronounced NMR shifts and is crucial in die differentiation of analytes with similar structures. This new scheme allows for the precise and simultaneous identification of multiple analytes in a complex mixture. [ABSTRACT FROM AUTHOR]

Syntheticmacrocyclic hosts have played key roles in the development of host–guestchemistry. Crown ethers are a class of macrocyclic molecules withunique flexible structures. They have served as the first generationof synthetic hosts, and researchers have extensively studied themin molecular recognition. However, the flexible structures of simplecrown ethers and their relatively limited modes of complexation withguests have limited the further applications of these molecules. Inrecent years, researchers have moved toward fabricating interlockingmolecules, supramolecular polymers, and other assemblies with specificstructures and properties. Therefore, researchers have developed morecomplex crown ether-based macrocyclic hosts with multicavity structuresand multicomplexation modes that provide more diverse and sophisticatedhost–guest systems. [ABSTRACT FROM AUTHOR]

Reactions of [MN*3] (M = Ce, U; N* = N(SiMe3)2) and NR4CN (R = Me, Et, or nBu) or KCN in the presence of 18-crown-6 afforded the series of cyanido-bridged dinuclear compounds [NEt4][(MN*3)2(µ-CN)] (M = Ce, 2a, and U, 2b), [K(18-crown-6)(THF)2][(CeN*3)2(µ-CN)] (2'a), and [K(18-crown-6)][(UN*3)2(µ-CN)] (2'b), and the mononuclear mono-, bis-, and tris(cyanide) complexes [NEt4][MN*3(CN)] (M = Ce, 1aEt, and U, 1bEt), [NMe4][MN*3(CN)] (M = Ce, 1aMe, and U, 1bMe), [K(18-crown-6)][MN*3(CN)] (M = Ce, 1'a, and U, 1'b), [NnBu4]2[MN*3(CN)2] (M = Ce, 3a, and U, 3b), [K(18-crown-6)]2[MN*3(CN)2] (M = Ce, 3'a, and U, 3'b), and [NnBu4]2[MN*2(CN)3] (M = Ce, 4a, and U, 4b). The mono- and bis(cyanide) complexes were found to be in equilibrium. The formation constant of 3'b (K3'b) from 1'b at 10 °C in THF is equal to 5(1) × 10-3, and -δH3'b = 104(2) kJ mol-1 and -δS3'b = 330(5) J mol-1 K-1. The bis(cyanide) compound 3a or 3b was slowly transformed in solution into an equimolar mixture of the mono- and tris(cyanide) derivatives with elimination of NnBu4N*. The crystal structures of 1aMe, 1bMe, 1'a·toluene, 1'b·toluene, 2'a, 2'b, 3a, 3'a, 3'b, 3'a·2benzene, 3'b·2benzene, 4a·0.5THF, and 4b·Et2O were determined. Crystals of the bis(cyanide) uranium complexes 3'b and 3'b·2benzene are isomorphous with those of the cerium counterparts 3'a and 3'a·2benzene, but they are not isostructural since the data revealed distinct coordination modes of the CN group, through the C or N atom to the U or Ce metal center, respectively. This differentiation has been analyzed using density functional theory calculations. The observed preferential coordination of the cyanide and isocyanide ions toward uranium or cerium in the bis(cyanide) complexes is corroborated by the consideration of the binding energies of these groups to the metals and by the comparison of DFT optimized geometries with the crystal structures. The better affinity of the cyanide ligand toward UIII over CeIII metal center is related to the better energy matching between the 6d/5f uranium orbitals and the cyanide ligand ones, leading to a non-negligible covalent character of the bonding. [ABSTRACT FROM AUTHOR]

The themes of coordination-drivenself-assembly, host–guestinteractions, and supramolecular polymerization are unified in anorthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes.Specifically, a bis(p-phenylene)-34-crown-10 derivative 1bearing two pyridyl groups polymerizes into a side-chainpoly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4in the presence of paraquat. Interestingly, by adding acompetitive guest 3, the poly[2]pseudorotaxane can realizea conversion in one pot. [ABSTRACT FROM AUTHOR]

The structures of actinyl--crown ether complexes are key to their extraction behavior in actinide partitioning. Only UO2 (l8C6 )2+ and NpO2(l8C6)+ (18C6 = 18-Crown-6) have been structurally characterized. We report a series of complexes of uranyl, neptunyl, and plutonyl with 18-Crown-6, 15-Crown-5 (lSC5), and 12-Crown-4 (12C4) produced in the gas phase by electrospray ionization (ESI) of methanol solutions of AnO2(C1O4)2 (An = U, Np, or Pu) and crown ethers. The structures of 1:1 actinyl--crown ether complexes were deduced on the basis of their propensities to hydrate. Hydration of a coordinated metal ion requires that it be adequately exposed to allow further coordination by a water molecule; the result is that hydrates form for outercoordination isomers but not for inclusion isomers. It is demonstrated that all the actinyl 18C6 complexes exhibit fully coordinated inclusion structures, while partially coordinated outer-coordination structures are formed with 12C4. Both inclusion and outer-coordination isomers were observed for actinyl--15CS complexes, depending on whether they resulted from ESI or from collision-induced dissociation. Evidence for the formation of 1:2 complexes of actinyls with 1SCS and 12C4, which evidently exhibit bis-outer-coordination structures, is presented. [ABSTRACT FROM AUTHOR]

Twotypes of Cs+ion-selective crown ether–Nafioncomposite membranes have been prepared. In one case, the dibenzo-21-crown-7(DB21C7) has been incorporated uniformly in the Cs+formof Nafion-117 membrane in varying molar ratio with respect to Cs+, and in the other case, Cs+driven loading ofDB21C7 has been confined (ion gating) to a very small thickness (25μm) from one of the surfaces of the Nafion-117 membrane. Thesurface confinement of Cs+in the ion-gated membrane hasbeen studied by energy dispersive X-ray spectroscopy and secondaryion mass spectrometry. The cation (Cs+/Na+)transport properties of the membranes have been studied under applicationof electric field. In the uniformly crown-ether-loaded membranes (Cs-Naf-CR),the decrease in crown ether molar ratio has been found to increasethe mobility of Cs+through the membrane at the cost ofmutual cationic selectivity (Cs+over Na+).On the other hand, enhanced selectivity of Cs+over Na+with significant cationic transport at room temperature hasbeen obtained with the ion-gated membrane (Cs-H-Naf-CR). When appliedto the simulated nuclear waste solution, selective transport of Cs+has also been obtained using this gated membrane even inthe presence of very high Na+(Cs+:Na+= 1:1428) concentration in aqueous solution. [ABSTRACT FROM AUTHOR]

The formation of catenated systems can be simplified greatly if one or more rings are generated via self-assembly. Herein we exploit the orthogonality of coordination-driven self-assembly and crown-ether host-guest complexation to obtain a [4] molecular necklace and a [7]molecular necklace based on a well-developed recognition motif of 1,2-bis(pyridinium)ethane/ dibenzo[24]crown-8. By adapting the bis(pyridinium) motif into the backbone of a donor building block, the resulting semirigid dipyridyl species can serve both as a structural element in the formation of metallacycles and as a site for subsequent host-guest chemistry. The pseudo-linear nature of the donor precursor lends itself to the formation of triangular and hexagonal central metallacycles based on the complementary acceptor unit used. This exemplary system organizes up to 18 molecules from three unique species in solution to afford a single supramolecular ensemble. [ABSTRACT FROM AUTHOR]

An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained. [ABSTRACT FROM AUTHOR]

Phosphatidylethanolamines (PE) and phosphatidylcholines (PC) are important phospholipids frequently present in many types of cells. In some cases, PE has been equated with PC because they are chemically very similar and are often isomeric species. In this study, we demonstrate that noncovalent complexation between PE and 18-crown-6 ether (18C6) can be used to quantitatively mass shift and separate PE from PC phospholipids. Detection of PE is also more sensitive by approximately an order of magnitude with addition of 18C6. This noncovalent complexation approach is used to separate and quantitatively characterize PE in a soy bean asolectin extract. 18C6 (modified with an iodobenzoyl moiety) can also be used to efficiently generate radical PE lipids following photoactivation in the gas phase. Subsequent collisional activation of these lipid radical ions leads to radical directed dissociation (RDD), which generates unique fragment ions relative to dissociation of comparable even electron ions. Interestingly, RDD produces fragment ions that reveal carbon bonding features within the lipid acyl chain substituents, such as double bond location or the presence of branching. Furthermore, several novel and abundant fragments were observed in unsaturated lipids. Mechanisms that can account for the high abundance of some of these product ions are proposed. [ABSTRACT FROM AUTHOR]

Thereadily available recognition motifs with high affinity andselectivity can undoubtedly expedite the development of host–guestchemistry from fundamental research to practical application in miscellaneousfields. In this work, a series of guest-mediated [2]pseudorotaxanesare successfully constructed by the incorporation of tetrasulfonated1,5-dinaphtho-38-crown-10 (14–) withthree kinds of dicationic substrates, i.e., the diquaternary saltsof 4,4′-bipyridine, 1,10-phenanthroline, and 2,7-diazapyrene,which are comprehensively explored by means of UV/vis, 1H NMR spectra, X-ray crystallography, and microcalorimetric titrations.Significantly, the interpenetration of 14–with N,N′-dimethyl-2,7-diazapyreniumsalt (DMDAP2+) gives an extraordinarily strong associationconstant (Ka) up to 108M–1order of magnitude in water. Moreover, the spectroscopicand crystallographic analyses jointly demonstrate that there is acompetitive binding process in the complexation of 14–with DMDAP2+and methyl viologen (MV2+), in which DMDAP2+is internally encapsulatedin the cavity of 14–, whereas MV2+is externally embedded in the crystallographic lattice toform the ternary supramolecular assembly of MV2+·DMDAP2+⊂14–. We also envisionthat the Kagradient obtained in our systematicwork illustrates a new and elegant strategy for attaining multicomponentnanomaterials engineered at a molecualr level. [ABSTRACT FROM AUTHOR]

A novel bis(m-phenylene)-32-crown-10derivativebearing two π-extended pyridyl groups was synthesized, and itshost–guest complexation with a paraquat derivative to forma threaded [2]pseudorotaxane was studied. Subsequently, a poly[2]pseudorotaxanewas constructed with a metallosupramolecular polymer backbone viametal coordination, which was comprehensively confirmed by the combinationof 1H NMR, 31P{1H} NMR, DOSY NMR,DLS, and EDX techniques. [ABSTRACT FROM AUTHOR]

A carboxyethyl substituted azacrown ether (CSAE) derivative was intercalated as a second host into a parent host of layered gadolinium hydroxides (LGdH) by an anion-exchange reaction. The influence of intercalation temperature and starting material ratios of CSAE/LRH on the structures and compositions of CSAE-LRH nanocomposites were investigated. Higher temperature and larger initial CSAE-LGdH weight ratios favor of higher degree of ion exchange at a certain range, while lower temperature gives good morphology for the composites. The adsorptive properties for transition and heavy metal ions were studied using the 20 °C-reacted composite, which showed higher adsorptivity toward transition and heavy metal ions, accompanied by the introduction of nitrate anions. The adsorptive capacity for transition metal ions was in the sequence of Cu2+ > Zn2+~Ni2+~Co2+ with a high selectivity to Cu2+. For the heavy metal ions Ag+, Hg2+, Pb2+, and Cd2+, the composite showed markedly high selectivity for Ag+ and Hg2+. When putting Cu2+, Ag+, Hg2+, Pb2+, and Cd2+ together, Ag+ and Hg2+ still have higher adsorptive selectivity over Pb2+ and Cd2+, and Cu2+ has also relatively high selectivity but not as high as Ag+ and Hg2+. The nanocomposites with a second host in the interlayer are one promising kind of material because of the synergy of the steric effect of the parent host (LRH layer) and the particular characteristics of the secondary host (interlayer crown ether anions). [ABSTRACT FROM AUTHOR]

Traditional drugs have the disadvantages of poor permeability and low solubility, which makes the utilization of pesticides lower and brings many side effects. With the continuous development of supramolecular chemistry in recent years, it has also played an irreplaceable role in the field of pharmaceutical science. Supramolecular macrocycles, such as crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are potentially good candidates for drug carriers due to their biocompatibility, hydrophobic cavity and ease of derivatization. The encapsulation of drugs based on host-guest interaction has the advantage of being adjustable and reversible as well as improving the low availability of drugs. Here, the recent advances in methods and strategies for drug encapsulation and release based on supramolecular macrocycles with host-guest interactions have been systematically summarized, laying a bright foundation for the development of novel nanopesticide preparations in the future and pointing out future directions of novel biopesticide research.