Chemistry Of Crown Ethers Research Articles

Topological Strain-Induced Regioselective Linker Elimination in a Chiral Zr(IV)-Based Metal-Organic Framework

Summary Zr-carboxylate metal-organic frameworks (MOFs) are structurally robust materials, in part due to their strong coordination bonds. The regioselective Zr–O bond cleavage and formation between 3D architectures are thus challenging and are heretofore unexplored. In this work, by introducing highly flexible 18-crown-6-ether functionalities into a homochiral Zr-MOF, we report an unprecedented topology transition in which a 4,10-connected framework undergoes a rapid solid-state transition into a thermodynamically more stable 4,8-connected analog by a regioselective-linker-elimination under ambient conditions. The transition process was unambiguously unraveled by single-crystal and powder X-ray diffraction studies, and we proposed a possible transition mechanism based on various control experiments and theoretical calculations. The excellent chemical stability and substantially expanded porosity and pore apertures endowed the transformed chiral MOF with an exceptional capacity for the enantioadsorptive and solid-phase extractive separation of the racemic drug molecule of lansoprazole with 98% ee and 93% ee, respectively.

Quantum Transmission of He Isotopes through Crown Ether-Embedded Graphene Nanomeshes: An Eckart Potential Approach

The remarkable performance of carbon membranes for the selective passage of various species has led to extensive research in designing smart membranes. The mechanical stability of graphene in conjunction with the excellent host-guest chemistry of crown ethers makes the recently synthesized family of crown ether-embedded graphene nanomeshes promising candidates for sieving applications. Inspired by the excellent control over pore architectures offered by such nanomeshes, we investigate the abilities of crown ether-embedded graphene nanomeshes for noble gas separation by the size-sieving mechanism and for He isotope separation by the quantum sieving mechanism. Unlike the previous studies that employ either a finite-difference approach or a wave packet approach, we employ an analytical Eckart potential approach to calculate the tunneling probabilities. Using tunneling-corrected transition-state theory, we examine the competing nature of the zero-point energy effects and tunneling effects in governing the total quantum transmission of the isotopes. Our analysis of the permeation barriers, diffusion rates, transmission probabilities, permeabilities, and selectivities suggests that crown ether-embedded graphene nanomeshes are a class of promising carbon membranes for He isotope separation.

Responsive Supramolecular Polymer Metallogel Constructed by Orthogonal Coordination-Driven Self-Assembly and Host/Guest Interactions

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.

Crown Ether Chemistry of Polydentate Complexing for Lithium Isotope Separation

Crown Ether Chemistry of Polydentate Complexing for Lithium Isotope Separation

ChemInform Abstract: Synthesis and Reaction of Hypervalent λ3‐Iodane—Crown Ether Complexes

AbstractReview: 32 refs.

Synthesis and Reaction of Hypervalent λ<sup>3</sup>-Iodane-Crown Ether Complexes

In this review, we show that intermolecular hypervalent I(III)…O interactions play an essential role in the complexation of organo-λ(3)-iodanes with crown ethers. In addition to the well-known driving force for the complexation of crown ethers, ion-dipole interaction, and hydrogen bonding interaction, our result provides a new class of interaction in supramolecular chemistry of crown ethers. Both solid state structure analysis and solution chemistry indicate that diaryl-, 1-alkenyl(phenyl)-, 1-alkynyl(phenyl)-, and hydroxy(phenyl)-λ(3)-iodanes form stable complexes with 18-crown-6 through hypervalent I(III)…O interactions. The complexation not only increases the stability of these hypervalent λ(3)-iodanes but also holds its high reactivity toward nucleophiles. The complex of hydroxy(phenyl)-λ(3)-iodanes with 18-crown-6 serve as versatile oxidizing agents, especially in water.

ChemInform Abstract: Chemistry of Crown Ethers. Synthesis of New Crown Ethers Containing Pyridazine Ring.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Perfluorocarbon Soluble Crown Ethers as Phase Transfer Catalysts

AbstractFluorous derivatives of dibenzo‐18‐crown‐6 ether were readily prepared by means of metal‐catalyzed cross‐coupling reactions, and then successfully applied as catalysts in representative solid‐liquid phase transfer catalysis (PTC) reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, and also in fluorous solvents, such as perfluoro‐1,3‐dimethylcyclohexane (PFDMC). It was clearly shown that properly designed fluoroponytailed crown ethers can promote the disintegration of the crystal lattice of alkali salts and transfer anions from the solid surface into an apolar, non‐coordinating perfluorocarbon phase. Far from being a simple chemical curiosity, this unprecedented observation has relevant implications in the design of PTC scenarios of wide applicability. This new paradigm represents an advance in crown ether chemistry, and their use as recyclable phase transfer catalysts.

Crown ether strategy toward chemical activation of biological protein functions

AbstractThe chemical activation of biological proteins is outlined, in which small molecules are used to alter the chemical and physical properties of biological proteins through direct or indirect interactions. Crown ethers have the potential to modulate the protein functions by supramolecular complexations, because they bind alkylammonium and other ionic residues of the proteins as well as ionic components in their systems. Two interesting examples are described in which crown ether derivatives improved the protein functions: (1) enhancement of reactivity and enantioselectivity in lipase‐catalyzed asymmetric reactions; and (2) generation of catalytic activity in the oxidation with cytochrome c. This chemical activation based on crown ether chemistry can be viewed as a complementary method to biological mutation in modifying the biological protein functions.

An investigation of the surface chemistry of crown ethers: the adsorption and reaction of 12-crown-4 on palladium ( [formula omitted

The adsorption of 12-crown-4 on Pd(1 1 1) is investigated using reflection–absorption infrared spectroscopy and temperature-programmed desorption. Analysis of the infrared spectrum of 12-crown-4 suggests that it adsorbs in a flat-lying geometry with C 4v symmetry with a saturation coverage of 0.073±0.008 monolayers. This implies that the crown ether bonds to the surface via the lone pair orbitals on the ether oxygen atoms. Estimating the saturation coverage for this geometry using Van der Waals' radii yields a value of 0.088 monolayers in good agreement with the measured value. 12-crown-4 thermally decomposes to leave predominantly CO and ethylidyne species on the surface where the desorbing CO removes three of the four crown ether oxygen atoms, the fourth remaining on the surface. Small amounts of ethylene are also found to desorb along with a high molecular weight product which is tentatively assigned to the formation of C 2H 5OCH 2CHO.

Investigation of the surface chemistry of crown ethers: the adsorption and reaction of 1,4-dioxane on palladium (111)

1,4-Dioxane adsorbs on Pd(111) at 80 K to form an overlayer saturating at an exposure of ∼4 L (1 L=1×10 −6 Torr s) and desorbs with a peak centered at ∼268 K in temperature-programmed desorption. Multilayer growth commences for exposures >2 L suggesting that they form before the monolayer is completed. The multilayers desorb at ∼160 K. Reflection–absorption infrared spectroscopy of both normal and perdeuterated dioxane suggests that it converts from its usual chair conformation in the gas phase into a boat conformation in the monolayer, allowing the lone pairs on both oxygen atoms to interact with the surface. A portion of the adsorbed dioxane thermally decomposes at or below ∼300 K to desorb ethylene and hydrogen and to deposit CO onto the surface. The adsorbed CO thermally desorbs at ∼460 K.

Some crown ether chemistry of Ti, Zr and Hf derived from liquid clathrate media

Download options Please wait... Article information DOI https://doi.org/10.1039/A707684C Article type Paper Download Citation J. Chem. Soc., Dalton Trans., 1998, 1223-1228 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Some crown ether chemistry of Ti, Zr and Hf derived from liquid clathrate media A. Alvanipour, J. L. Atwood, S. G. Bott, P. C. Junk, U. H. Kynast and H. Prinz, J. Chem. Soc., Dalton Trans., 1998, 1223 DOI: 10.1039/A707684C To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Abbas Alvanipour Jerry L. Atwood Simon G. Bott Peter C. Junk Ulrich H. Kynast Horst Prinz

Chemistry of crown ethers. Synthesis of new crown ethers containing a pyridazine ring

A method for preparation of crown ethers containing a pyridazine ring based on 1,2-dihydro-3,6-dioxopyridazine was developed.

Dipotassium and sodium/potassium crystalline picrate complexes with the crown ether 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n][1,4,7,10,13,16,19,22]octaoxacyclotetracosin (dibenzo-24-crown-8)

The crystal structures of the dipotassium and the mixed sodium/potassium picrate complexes with the crown ether dibenzo-24-crown-8 (DB24C8) were solved and found to be nearly identical. (I): NaK-pic2(DB24C8), [NaK(C6H2N3O7)2(C24H32O8)]. Mr = 966.8, triclinic, P1, a = 8.164 (2), b = 9.960 (2), c = 13.368 (3) A, alpha = 103.92 (3), beta = 108.03 (2), gamma = 93.23 (2) degrees, V = 993.0 (7) A3, Z = 1, Dm = 1.54 (T = 298 K). Dx = 1.62 (1) g cm-3, lambda = (Mo K alpha) 0.71069 A, mu = 2.37 cm-1, F(000) = 500, T = 103 K, R = 0.086 for 2904 unique reflections. (II): K2pic2(DB24C8), [K2(C6H2N3O7)2(C24H32O8)]. Mr = 982.9, triclinic, P1, a = 8.231 (4), b = 9.850 (2), c = 13.346 (4) A, alpha = 103.91 (2), beta = 106.82 (3), gamma = 93.37 (2) degrees, V = 995.7 (9) A3, Z = 1, Dm = 1.59 (T = 298 K), Dx = 1.638 (8) g cm-3, lambda (Mo K alpha) = 0.71069 A, mu = 3.30 cm-1, F(000) = 508, T = 163 K, R = 0.042 for 4835 unique reflections. Both structures feature eight-coordinated cations between alternating layers of relatively flat crown ligands and paired picrates. In the mixed-metal system the two cations are disordered between two P1-related sites; these metal sites have a coordination environment only slightly different from that in the dipotassium structure. Na+ is able to occupy an environment similar to that of K+ under the conditions of these crystals, a situation not previously observed in the chemistry of crown ethers or macrocylic multidentates.

ChemInform Abstract: “Remote Control” of Flavin Reactivities by an Intramolecular Crown Ring Serving as a Metal‐Binding Site.

AbstractThe two concepts, "remote functionalization" in steroid photochemistry and "lariat ethers" in crown ether chemistry are applied to design flavins with an allosteric functionality.

ChemInform Abstract: New Developments in the Chemistry of Crown Ethers with "Switch‐Function" and Perspectives in Their Progress

Chemischer InformationsdienstVolume 17, Issue 20 Reviews ChemInform Abstract: New Developments in the Chemistry of Crown Ethers with "Switch-Function" and Perspectives in Their Progress S. SINKAI, S. SINKAISearch for more papers by this author S. SINKAI, S. SINKAISearch for more papers by this author First published: May 20, 1986 https://doi.org/10.1002/chin.198620368Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue20May 20, 1986 RelatedInformation

ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY (PART IV E): NEW APPLICATIONS OF CROWN COMPOUNDS IN CHEMICAL ANALYSIS

Chemischer InformationsdienstVolume 15, Issue 27 Reviews ChemInform Abstract: PROGRESS IN CROWN ETHER CHEMISTRY (PART IV E): NEW APPLICATIONS OF CROWN COMPOUNDS IN CHEMICAL ANALYSIS E. WEBER, E. WEBERSearch for more papers by this author E. WEBER, E. WEBERSearch for more papers by this author First published: July 3, 1984 https://doi.org/10.1002/chin.198427371Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume15, Issue27July 3, 1984 RelatedInformation

The stability of coordination compounds of some crown ethers with lanthanide(III) ions

Moncyclic polyethers, the ‘crown ethers’, are noted for their affinity and high selectivity towards alkali and alkaline earth elements, and a large amount of work has been published concerning the coordination chemistry of crown ethers with these elements. However. information about the coordination behavior of crown ethers towards the lanthanides is relatively scarce and is badly needed because of its practical as well as theoretical significance. t001 Stability Constants, β, Coordination Compounds of Crown Ethers with Na + and Ln 3+ (Solvent: MeOH; Ionic Strength: 0.1 M Me 4NCl). Crown 18C6 DB18C6 26 ± 0.5 °C DCH18C6 26 ± 0.5 °C Logβ 15 ± 0.5 °C 26 ± 0.5 °C 35 ± 0.5 °C Izatt [2] Ion Na + 4.35 ± 0.05 4.17 ± 0.02 4.01 ± 0.05 4.33 4.18 ± 0.01 3.32 ± 0.01 La 3+ 3.21 +- 0.05 3.25 ± 0.01 3.31 ± 0.03 3.29 ± 0.03 no 2.49 ± 0.03 Ce 3+ 2.76 ± 0.02 2.81 ± 0.01 2.93 ± 0.04 3.57 ± 0.20 no 2.05 ± 0.05 Pr 3+ 2.36 ± 0.02 2.47 ± 0.01 2.57 ± 0.04 2.63 ± 0.28 no 1.62 +- 0.07 Nd 3+ 2.05 ± 0.11 2.16 ± 0.01 2.30 ± 0.09 2.44 ± 0.16 no <1.3 Sm 3 - <1.6 - 2.03 ± 0.07 no no Eu 3+ - <1.5 - 1.84 ± 0.14 no no Gd 3+ - <1.5 - 1.34 ± 0.12 no no Tb 3+ - <1.2 - no <1.5 no Dy 3+ - <1.2 - no <1.7 no Ho 3+ - <1.5 - no <1.7 no Er 3+ - <1.4 - no <1.5 no Tm 3+ - <1.3 - no <1.6 no Yb 3+ - no - no <1.4 no Lu 3+ - no - no <1.4 no t002 Thermodynamic Functions for the Coordination of 18-C-6 with Na + and Ln 3+ in Methanol at 25 °C Ion ΔG° (kcal/mol) ΔH° (kcal/mol) TΔS° (kcal/mol) Na + −5.72 −8.01 −2.3 La 3+ −4.47 2.30 6.7 Ce 3+ −3.89 3.84 7.7 Pr 3+ −3.38 4.45 7.8 Nd 3+ −2.96 6.14 9.1 A pNa method is developed for the determination of the stability constants of the coordination compounds of crown ethers and lanthanide ions, Ln 3+, based on the competition between Na + and Ln 3+ ions towards coordination with a given crown. It consists of setting up a cell using Na + as the competing ion, Na +-selective electrode as the indicating electrode and AgAgCl electrode as the reference electrode. The electromotive forces of such a cell (C = drown ether) AgAgCl¦0.1 M Me4NCl, x M Na +, y M C, z M Ln 3+¦ Na +-electrode are measured successively under those conditions: (1) only Na +, but neither crown nor Ln 3+ is present; (2) crown ether is present but not Ln 3+ ion is present; (3) both crown ether and Ln 3+ are present. From the electromotive forces measured, concentrations of free ions and then stability constants can be calculated. Details of this method were published in a short note [1]. With this method, stability constants of coordination compounds of 18-crown-6 (18-C-6), dibenzo 18-crown-6 (DB 18-C-6), dicyclohexyl 18-crown-6 (DCH 18-C-6), 15-crown-5 (15-C-5) and benzo 15-crown-5 (B 15-C-5) with all Ln 3+ ions except Pm 3+ in methanol are determined. The results are given in Table I and agree quite well with those reported by Izatt et al. [2] except for Ce 3+. It can be seen that for the lighter lanthanides, the stability constants of the coordination compounds with 18-C-6 or DCH 18-C-6 decrease with increasing atomic number of the lanthanides, a fact which can be explained by the better matching of the crown ether cavity size with cation diameter. The 18-C-6 also shows weak coordination with the heavier lanthanides whereas the DB 18-C-6 shows weak coordination only with the heavier lanthanides and no coordination is indicated for 15-C-5 or 15-C5 with any lanthanides. The stability constants of Na +, La 3+, Ce 3+ Pr 3+ and Nd 3+ are determined at three different temperatures for the determination of ΔH° calculated by plotting log β against 1/T, Δ° is calculated from the relation ΔG° = RTlnβ and then ΔS° calculated from the relation ΔG° = ΔH° - TΔS°. The results obtained are given in Table II. From the ΔH° and ΔS° values it can be seen that the observed stability is entropic in origin.

Thio crown ether chemistry. [Cobalt(II)·hexathio-18-crown-6], an octahedral low-spin complex of CoII

Hexathio-18-crown-6 wraps around CoII to yield a rare example of a low-spin octahedral CoII complexe, as shown by structural, magnetic, and e.s.r. studies.

Chemistry of crown ethers. Part XXII. Synthesis and complexing properties of monophospha‐crown ethers

AbstractThe synthesis of phenyl‐ and tert‐butyl‐phosphadibenzo‐18‐crown‐6 and phenylphosphadibenzo‐21‐crown‐7 is described. The complexation of alkali metal cations and rhodium(I) by these macrocycles and their phosphine oxides has been studied by NMR methods. The phosphorus crown ethers are all capable of solubilizing lithium cations into chloroform. The phosphine oxide macrocycles also solubilize sodium cations. It is remarkable that tert‐butyl‐phosphadibenzo‐18‐crown‐6 complexes the sodium cation, whereas phenylphosphadibenzo‐18‐crown‐6, whose cavity is about the same size, does not. The formation of a bimetallic (Rh(I),Li+) complex of phenylphosphadibenzo‐21‐crown‐7 is discussed.