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Showing 1 to 20 of 47 for “"Crown Ethers"”.
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Explorations with optically active, cage-annulated crown ethers.
A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these …
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Synthesis and properties of novel cage-functionalized crown ethers and cryptands.
… of a K+-complexed bis-cage-annulated 20-crown-6 was obtained. The associated picrate anion was found to be intimately involved in stabilization of the host-guest complex. The interaction energy between the host-guest complex and picrate anion has been calculated, and the energy thereby …
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Separation of alkali metal cations and alkaline earth cations using ionizable crown ethers
Proton-ionizable crown ethers are novel agents for the separation of metal ions by extraction and membrane transport processes. A series of novel crown ether carboxylic acids , crown ether phosphonic acid monoesters, and crown ether phosphonic acids which possess lipophilic pendant groups were …
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Self-Assembly: Synthesis and Complexation of Crown Ethers and Cryptands with R2-NH2 Ions
… rotaxanes between several large bisphenylene crown ethers (> 22 atoms) with secondary ammonium salts. Also of great interest was to understand the complexation behavior of the crown ethers with the salts, with emphasis on determining the stoichiometries and association constants of the …
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Design and Synthesis of Novel Cage-Functionalized Crown Ethers: A New Class of Ag Complexants.
Three different types of cage crown ethers have been prepared and their complexation properties with Ag(I) have been studied. Atomic absorption, fluorescence quenching, and UV absorption have been used to study the interaction between the hosts (cage crown ethers) and guests (Ag+). For the …
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The use of immobilised crown ethers as in-situ protecting groups for organic synthesis within flow reactors
… requirement for orthogonal protecting groups. Crown ethers are commonly associated with the complexation of metal ions, but the 18-crown-6 species also readily bind ammonium ions with complexation occurring via hydrogen bonding. As discussed in Chapter 1, crown ethers have previously been …
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Synthesis and host-guest interaction of cage-annulated podands, crown ethers, cryptands, cavitands and non-cage-annulated cryptands.
Symmetrical cage-annulated podands were synthesized via highly efficient synthetic strategies. Mechanisms to account for the key reaction steps in the syntheses are proposed; the proposed mechanisms receive support from the intermediates that have been isolated and characterized. An unusual …
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Modeling Ionophore Selectivity in the Gas Phase: IR Spectroscopy of Solvated Metal Ion-Crown Ether Complexes
Crown ethers are a family of compounds that are closely related to a variety of biological and naturally-occurring ionophores. Thus, crown ethers have become the prototypical ionophore-model systems in chemistry and biology. Insight gained by studying the interaction of crown ethers with metal ions …
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Synthesis and characterization of liquid crystalline polyrotaxanes based on poly(azomethine)s
… are new polymers. Macrocyclic molecules, such as crown ethers, are threaded by linear or branched polymer chains. There is no covalent bond between the crown ethers and the polymer backbone. After the crown ethers are threaded onto the polymer backbone, both ends of the polymer can be blocked by …
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Syntheses and structures of some polyoxomolybdates and polyoxotungstates
Since the discovery of the crown ethers supramolecular chemistry has been dealing with molecular containers. Over the decades, the flat crown ethers have given way to three-dimensional shapes including cryptands, cavitands and ultimately capsules, designed to encapsulate molecular hosts. Now the …
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Dibenzo-30-crown-10: Synthetic optimization and studies of the binding conformation
Dibenzo-30-crown-10 (DB30C10) is one of the first-generation macrocyclic hosts discovered by Pedersen. Crown ethers originally attracted attention due to their ability to encapsulate metal cations and render them soluble in organic solvents. These studies helped to launch host-guest chemistry as a …
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New polymer architectures: synthesis and characterization of polyurethane-crown ether based polyrotaxanes
… their unique architectures. The studies include crown ether and blocking group syntheses, synthetic methodologies leading to rotaxanes and polyrotaxanes and structure-property relationships of polyrotaxanes. Crown ethers (30-crown-10, 36-crown-12, 42-crown-14, 48-crown-16 and 60-crown-20) were …
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Supramolecular architectures: macrocycles, catenanes and polyrotaxanes
… of styrene. As cyclic components, aliphatic crown ethers (30-crown-lO, "42-crown-14" and "6O-crown-20") were synthesized by multi-piece combination methods. The purification of the crown ethers was achieved by treatment with poly(methacryloyl chloride), column chromatography and …
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Self-Assembly, Templation and Biomimetics
… approach for the synthesis of large aromatic crown ethers, using resorcinarenes as templates, has been developed. This simple threestep process generated a new family of aromatic crown ethers in up to 50% overall yield. As intermediates from these three-step syntheses, a large variety of …
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Macrocyclic chemistry: Part I - Characterization of a mixed-valence di-iron complex and synthesis of a new poly-iron complex. Part II - Synthesis, characterization of new diphosphoester macrocyclic polyethers
<p>Our research involved two projects: Crown Aza and Crown ether. Crown Aza are compounds that have nitrogens as the hetero-atoms in the macrocycle. In the first aim, the 1 H NMR spectrum of strongly-coupled di-iron complexes shows 5 different conformations, but is unable to identify these …
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Molecular composites of a conducting polymer: syntheses and characterization of poly(1,4-phenylenevinylene)-crown ether rotaxanes
… as the linear backbone and different sizes of crown ethers (42C14, 60C20) as macrocycles, molecular composites of the conducting polymer were generated To compare with the PPV rotaxanes, PPV was synthesized and characterized by NMR, IR, UV-vis, photoluminescence spectroscopy, and TGA. The …
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Metal ion complexation, extraction and transport by crown and lariat ether compounds
A wide variety of crown ethers have been employed for alkali and alkaline earth metal cation separations due to their superior binding ability for these metal ions. Lariat ethers are crown ethers with one or more donor-groupbearing arms. Attachment of one or more side arms with potential metal ion …
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Synthesis and characterization of phosphorous containing macromolecular polyether compounds
… is used in positron emission tomography. Neutral crown ethers and cryptands have been studied as carrier ligands for Rb<sup>+</sup> but exhibit low ion carrying capacity and high toxicity. The present study involved investigating a lariat ether containing an ionizable phosphoryl moiety and a …
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Molecular necklaces: polyester rotaxanes
… consisting of 30-60 membered aliphatic crown ether macrocycles whose cavities are pierced by polysebacate chains were synthesized by several polymerization approaches including transesterification polymerization, the acid chloride method, and interfacial polymerization. The polyrotaxanes …
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