Macrocyclic polyethers with the repeating unit of (-CH2-CH2-O)n where n is greater than 2 and some oxygens may be replaced by nitrogen, sulfur or phosphorus. These compounds are useful for coordinating CATIONS. The nomenclature uses a prefix to indicate the size of the ring and a suffix for the number of heteroatoms.
Complex compounds in which a dumbbell shaped molecule is encircled by a macrocycle. They are named after rota (wheel) and axis (axle). Notation with a prefix is used to indicate the number of interlocked components. They have potential use in NANOTECHNOLOGY. Rotaxanes have been made with CYCLODEXTRINS and CYCLIC ETHERS.
A prosthetic restoration that reproduces the entire surface anatomy of the visible natural crown of a tooth. It may be partial (covering three or more surfaces of a tooth) or complete (covering all surfaces). It is made of gold or other metal, porcelain, or resin.
Agents that reduce the frequency or rate of spontaneous or induced mutations independently of the mechanism involved.
Compounds of the general formula R-O-R arranged in a ring or crown formation.
A mobile, very volatile, highly flammable liquid used as an inhalation anesthetic and as a solvent for waxes, fats, oils, perfumes, alkaloids, and gums. It is mildly irritating to skin and mucous membranes.
A colorless and flammable gas at room temperature and pressure. Ethylene oxide is a bactericidal, fungicidal, and sporicidal disinfectant. It is effective against most micro-organisms, including viruses. It is used as a fumigant for foodstuffs and textiles and as an agent for the gaseous sterilization of heat-labile pharmaceutical and surgical materials. (From Reynolds, Martindale The Extra Pharmacopoeia, 30th ed, p794)
A colorless, flammable liquid used in the manufacture of FORMALDEHYDE and ACETIC ACID, in chemical synthesis, antifreeze, and as a solvent. Ingestion of methanol is toxic and may cause blindness.
Metals that constitute group 1(formerly group Ia) of the periodic table. They are the most strongly electropositive of the metals. Note that HYDROGEN is not considered an alkali metal even though it falls under the group 1 heading in the periodic table.
Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th ed)
Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).
Metals that constitute the group 2 (formerly group IIa) of the periodic table.
A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING.

Lead-selective membrane potentiometric sensor based on an 18-membered thiacrown derivative. (1/64)

A PVC-based membrane electrode for lead ions based on hexathia-18-crown-6-tetraone as membrane carrier was prepared. The influence of membrane composition, pH of test solution and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a lead concentration range from 1.0 x 10(-6) to 8.0 x 10(-3) M at 25 degrees C, and was found to be very selective, precise and usable within the pH range 3.0-6.0. The electrode was successfully used as an indicator electrode in potentiometric titration of lead ions and in direct determination of lead in water samples.  (+info)

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier. (2/64)

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.  (+info)

Role of hypoxia during normal retinal vessel development and in experimental retinopathy of prematurity. (3/64)

PURPOSE: To test the hypothesis that retinal hypoxia is present during vascular development in normal rat pups and in a newborn rat model of retinopathy of prematurity (ROP). METHODS: Preretinal vitreous PO(2) measurements were made during room air breathing using (19)F magnetic resonance spectroscopy (MRS) and a perfluoro-15-crown-5-ether droplet in normal adult and newborn (postnatal day [P]1-P20) rats, and in newborn rats exposed first to 14 days of variable oxygen (before NV) and six additional days in room air after variable oxygen exposure (during NV). After each experiment, blood gas values were measured, and retinas were isolated. Retinas were adenosine diphosphatase (ADPase) stained, and flatmounted to determine peripheral avascular extent and NV incidence and severity. RESULTS: In the vascularized rat retina, no significant difference (P > 0.05) was found between the droplet-derived preretinal vitreous oxygen tension (24 +/- 2 mm Hg, mean +/- SEM, n = 18) and previously reported electrode-measured oxygen tension (22 +/- 1 mm Hg). Only during normal retinal vessel growth (P1-P10) and before the appearance of NV was evidence for retinal hypoxia found at the border of the vascular and avascular retina. However, the mean PO(2) (range, 24-28 mm Hg) over the vascular retina was not different (P > 0.05) between any of the newborn rat groups in this study. CONCLUSIONS: (19)F MRS of a perfluorocarbon droplet provides an accurate measure of preretinal vitreous oxygen tension in rats. These data support an important role of physiologic hypoxia in normal retinal circulatory development and raises the possibility that, in experimental ROP, retinal hypoxia is a necessary but not sufficient condition for the development of retinal NV.  (+info)

Selective molecular recognition of arginine by anionic salt bridge formation with bis-phosphate crown ethers: implications for gas phase peptide acidity from adduct dissociation. (4/64)

Arginine forms a stable noncovalent anionic salt bridge complex with DP (a crown ether which contains two endocyclic dialkylhydrogenphosphate esters). Abundant adduct formation with DP is observed for complexes with arginine, YAKR, HPPGFSPFR, AAKRKAA, RR, RPPGFSPFR, RYLGYL, RGDS, and YGGFMRGL in electrospray ionization mass spectrometry (ESI-MS) experiments. DFT calculations predict a hydrogen bonded salt bridge structure with a protonated guanidinium flanked by two deprotonated phosphates to be the lowest energy structure. Dissociation of DP/peptide adducts reveals that, in general, the relative gas phase acidity of a peptide is dependent on peptide length, with longer peptides being more acidic. In particular, peptides that are six residues or more in length can stabilize the deprotonated C-terminus by extensive hydrogen bonding with the peptide backbone. Dissociation of DP/peptide complexes often yields the deprotonated peptide, allowing for the facile formation of anionic peptides that otherwise would be difficult to generate in high abundance. Although DP has a preference for binding to arginine residues in peptides, DP is also observed to form less abundant complexes with peptides containing multiple lysines. Lys-Xxx-Lys and Lys-Lys sequences form low abundance anionic adducts with DP. For example, KKKK exclusively forms a double adduct with one net negative charge on the complex.  (+info)

Potentiometric determination of dopamine in pharmaceutical preparations by crown ether-PVC membrane sensors. (5/64)

Two simple, rapid and sensitive sensors for the assay of dopamine hydrochloride have been developed. The methods are based upon the formation of the membrane sensors 12-crown-4-phosphotungestic acid (crown ether-PTA)-dopamine and 12-crown-4-tetraphenylborate (crown ether-TPB)-dopamine as neutral carriers. The sensors were stable and showed fast potential responses of 10 s, and near-Nernstian cationic slopes of 53.3 - 56.2 mV/decade of activity between pH 2.2 - 6 for the monovalent dopamine cation over a wide range concentrations 1 x 10(-5) - 1 x 10(-1) M. The selectivity coefficients of the developed sensors indicated excellent selectivity for dopamine over a large number of organic and inorganic species and pharmaceutical excipients. The mediator o-nitrophenyloctyl ether significantly affected the lifetime of the fabricated sensors of dopamine. Satisfactory results were obtained for the determination of dopamine in dosage form by the proposed sensors with an average recovery of 99.85% for the nominal concentration.  (+info)

Field-dependent effect of crown ether (18-crown-6) on ionic conductance of alpha-hemolysin channels. (6/64)

Closing linear poly(ethylene glycol) (PEG) into a circular "crown" dramatically changes its dynamics in the alpha-hemolysin channel. In the electrically neutral crown ether (C2H4O)6, six ethylene oxide monomers are linked into a circle that gives the molecule ion-complexing capacity and increases its rigidity. As with linear PEG, addition of the crown to the membrane-bathing solution decreases the ionic conductance of the channel and generates additional conductance noise. However, in contrast to linear PEG, both the conductance reduction (reporting on crown partitioning into the channel pore) and the noise (reporting on crown dynamics in the pore) now depend on voltage strongly and nonmonotonically. Within the whole frequency range accessible in channel reconstitution experiments, the noise power spectrum is "white", showing that crown exchange between the channel and the bulk solution is fast. Analyzing these data in the framework of a Markovian two-state model, we are able to characterize the process quantitatively. We show that the lifetime of the crown in the channel reaches its maximum (a few microseconds) at about the same voltage (approximately 100 mV, negative from the side of protein addition) where the crown's reduction of the channel conductance is most pronounced. Our interpretation is that, because of its rigidity, the crown feels an effective steric barrier in the narrowest part of the channel pore. This barrier together with crown-ion complexing and resultant interaction with the applied field leads to behavior usually associated with voltage-dependent binding in the channel pore.  (+info)

Microcalorimetric study on host-guest complexation of naphtho-15-crown-5 with four ions of alkaline earth metal. (7/64)

Thermodynamic parameters of complexation of naphto-15-crown-5 with four alkaline earth ions in aqueous media was determined using titration microcalorimetry at 298.15 K. The stability of the complexes, thermal effect and entropy effect of the complexation is discussed on the basis of the guest ions structure and the solvent effect. The stability constants tendency to vary with ion radius was interpreted. Complex of naphtha-15-crown-5 with calcium ion is very stable due to the synergism of static electric interaction and size selectivity between the host and the guest.  (+info)

A novel ternary ligand system useful for preparation of cationic (99m)Tc-diazenido complexes and (99m)Tc-labeling of small biomolecules. (8/64)

This report describes a novel ternary ligand system composed of a phenylhydrazine, a crown ether-containing dithiocarbamate (DTC), and a PNP-type bisphosphine (PNP). The combination of three different ligands with (99m)Tc results in cationic (99m)Tc-diazenido complexes, [(99m)Tc(NNAr)(DTC)(PNP)]+, with potential radiopharmaceuticals for heart imaging. Synthesis of cationic (99m)Tc-diazenido complexes can be accomplished in two steps. For example, the reaction of phenylhydrazine with (99m)TcO4- at 100 degrees C in the presence of excess stannous chloride and 1,2-diaminopropane-N,N,N',N'-tetraacetic acid (PDTA) results in the [(99m)Tc(NNPh)(PDTA)n] intermediate, which then reacts with sodium N-(dithiocarbamato)-2-aminomethyl-15-Crown-5 (L4) and N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]ethoxyethylamine (PNP6) at 100 degrees C for 15 min to give the complex, [(99m)Tc(NNPh)(L4)(PNP6)]+ in high yield (>90%). Cationic complexes [(99m)Tc(NNPh)(DTC)(PNP)]+ are stable for > or = 6 h. Their composition was determined to be 1:1:1:1 for Tc:NNPh:DTC:PNP using the mixed-ligand experiments on the tracer ((99m)Tc) level and was further confirmed by the ESI-MS spectral data of a model compound [Re(NNPh)(L4)(L6)]+. It was found that both DTCs and bisphosphines have a significant impact on the lipophilicity of their cationic (99m)Tc-diazenido complexes. Results from a (99m)Tc-labeling efficiency experiment showed that 4-hydrazinobenzoic acid (HYBA) might be useful as a bifunctional coupling agent for (99m)Tc-labeling of small biomolecules. However, the (99m)Tc-labeling efficiency of HYBA is much lower than that of 6-hydrazinonicotinic acid (HYNIC) with tricine and trisodium triphenylphosphine-3,3',3''-trisulfonate (TPPTS) as coligands.  (+info)

Crown ethers are heterocyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy (-CH2CH2O-). Important members of this series are the tetramer (n = 4, or four ethyleneoxy units), the pentamer (n = 5), and the hexamer (n = 6). The term crown refers to the resemblance between the structure of a crown ether bound to a cation, and a crown sitting on a head. The first number in the name of a crown ether refers to the number of atoms in the cycle, and the second number refers to the number of those atoms that are oxygen. Crown ethers are much broader than the oligomers of ethylene oxide; an important group is derived from catechol.. Crown ethers strongly bind certain cations, forming complexes. The oxygen atoms are well situated to coordinate with a cation located within the ring, whereas the exterior of the ring is hydrophobic (repels water and polar and ionic substances). The ...
TY - JOUR. T1 - Effects of Crown Ethers and Anions on Redox Behaviors of Europium(III/II) in Aqueous Solution. AU - Okaue, Yoshihiro. AU - Tomita, Masako. AU - Ichiyasu, Taketoshi. AU - Isobe, Toshiyuki. AU - Matsuda, Yoshihisa. PY - 1993/1/1. Y1 - 1993/1/1. N2 - The effects of crown ethers (12-crown-4, 15-erown-5, and lS-crown-6) and anions (C1O4~, NO3″, CI″, Br″, and I″) on the redox behaviors of europium(III/II) were investigated by cyclic voltammetry in an aqueous solution. The complexations of europium (II) with crown ethers were discussed by means of the shifts of redox potential. Addition of 18-crown-6 led to the appearance of a new oxidation wave at -0.28 V and the decrease of the peak height of the oxidation wave at -0.55 V. For 15-crown-5 and 12-crown-4, similar behaviors were observed, but the magnitude of the changes for oxidation peak heights was very small. These differences depend upon the relative sizes of europium(1) ion to the internal cavities of crown ethers. As ...
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We report the preparations and electron spin resonance (ESR) studies of a series of Cs+ and Rb+ crown ether (15-crown-5 and 18-crown-6) salts of [TcNCl4]- and [MoOCl4]-, and a new refinement of the X-ray structure of [Cs(18-crown-6)] [TcNCl4] involving a twinned P4/n scattering model. This refinement addresses some unsatisfactory aspects of the original disordered model. The structure consists of an infinite sandwich Cs+ cation/crown ether configuration and polymeric [TcNCL4]- anions, with Tc≡N distances of 1.561(36) Å, and anti-parallel chains of ---Tc≡N---Tc≡N ---with Tc···Tc separations of 4.275(4) Å. The structure determination of [Rb(15-crown-5)2][TcNCl4(OH2)] is also described and shows a lattice containing 2:1 sandwich-type crown ether/alkali-metal cations and isolated anions in the disordered lattice. The presence of Tc≡N infrared stretching frequencies at ca. 1074 cm-1 indicates the absence of strong electron donors coordinated to Tc in the sixth position (i. e. ...
TY - JOUR. T1 - Crowning proteins. T2 - Modulating the protein surface properties using crown ethers. AU - Lee, Cheng Chung. AU - Maestre-Reyna, Manuel. AU - Hsu, Kai Cheng. AU - Wang, Hao Ching. AU - Liu, Chia I.. AU - Jeng, Wen Yih. AU - Lin, Li Ling. AU - Wood, Richard. AU - Chou, Chia Cheng. AU - Yang, Jinn Moon. AU - Wang, Andrew H J. PY - 2014/11/24. Y1 - 2014/11/24. N2 - Crown ethers are small, cyclic polyethers that have found wide-spread use in phase-transfer catalysis and, to a certain degree, in protein chemistry. Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. We elucidated the crystal structures of several protein-crown ether co-crystals grown in the presence of 18-crown-6. We then employed biophysical methods and molecular dynamics simulations to compare these complexes with the corresponding apoproteins and with similar complexes with ring-shaped low-molecular-weight polyethylene glycols. Our studies show that crown ...
TY - JOUR. T1 - New crown ethers containing Kemps triacid and their binding properties with alkali metal cations. AU - Jeong, Kyu Sung. AU - Kim, Jong Hyun. N1 - Copyright: Copyright 2005 Elsevier Science B.V., Amsterdam. All rights reserved.. PY - 1996. Y1 - 1996. UR - http://www.scopus.com/inward/record.url?scp=18444365304&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=18444365304&partnerID=8YFLogxK. M3 - Article. AN - SCOPUS:18444365304. VL - 17. SP - 564. EP - 567. JO - Bulletin of the Korean Chemical Society. JF - Bulletin of the Korean Chemical Society. SN - 0253-2964. IS - 6. ER - ...
A bolaamphiphilic low-molecular-weight gelator based on crown ether, which could self-assemble into organogels and hydrogels, was prepared. The contribution of each part of the structure to the gelation property was investigated by designing a series of analogues. A simple framework (crown ether-hydrophobic
Abstract : A series of Gd(3+) complexes exhibiting a relaxometric response to zwitterionic amino acid neurotransmitters was synthesized. The design concept involves ditopic interactions 1) between a positively charged and coordinatively unsaturated Gd(3+) chelate and the carboxylate group of the neurotransmitters and 2) between an azacrown ether appended to the chelate and the amino group of the neurotransmitters. The chelates differ in the nature and length of the linker connecting the cyclen-type macrocycle that binds the Ln(3+) ion and the crown ether. The complexes are monohydrated, but they exhibit high proton relaxivities (up to 7.7 mM(-1) s(-1) at 60 MHz, 310 K) due to slow molecular tumbling. The formation of ternary complexes with neurotransmitters was monitored by (1) H relaxometric titrations of the Gd(3+) complexes and by luminescence measurements on the Eu(3+) and Tb(3+) analogues at pH 7.4. The remarkable relaxivity decrease (≈80 %) observed on neurotransmitter binding is related ...
The reaction of bismuth triiodide with iodine and benzo-15-crown-5 in ethanol/dichloromethane yielded red single crystals of (b15c5)BiI3(I2) (monoclinic, P21/c (no. 14), a = 1376.9(1), b = 1172.7(1), c = 1700.2(2) pm, b = 115.197(6), V = 2484.1(4)·106 pm3, Z = 4). Neutral pseudo-octahedral complexes (b15c5)BiI3 are connected by secondary bonding interactions via iodine molecules to chains. Electronic structure calculations of the neutral complex (b15c5)BiI3 reveal that the compound can indeed be described as b15c5 interacting with a molecular BiI3 unit. However, bonding has to be mainly electrostatic as the interactions of the bismuth 6s lone pair with the 2p orbitals of the oxygen atoms of the crown ether are clearly antibonding.
Visit ChemVia,you find CAS NO.75507-25-4,2-Hydroxymethyl-15-crown-5 specification and current price;you can buy 75507-25-4,2-Hydroxymethyl-15-crown-5 reagent online,and you can buy 2-Hydroxymethyl-15-crown-5 on bulk underline.
We measured UV photodissociation and IR-UV double-resonance spectra of benzo-crown ether complexes with alkali metal ions (Li$^{+}$, Na$^{+}$, K$^{+}$, Rb$^{+}$, and Cs$^{+}$) in a cold, 22-pole ion trap nderline{\textbf{133}}(31), 12256 July 2011.}. All the complexes show a number of vibronically resolved UV bands in the 36000-38000 cm$^{-1}$ region. We used the IR-UV spectra in the CH stretching region to distinguish peaks in the UV spectra that belong to different conformers. The use of density functional theory allows us to determine the conformation of the complexes ...
The novel laser desorption method laser-induced liquid beam ionization/desorption (LILBID) is applied to the mass spectrometric examination of selective ion binding by natural and synthetic ionophores in methanol solutions. The ions are desorbed from a liquid jet with an IR laser pulse and then extracted perpendicularly into a reflectron time-of-flight (RE-TOF) analyzer. LILBID studies on the natural ion carriers valinomycin and monensin A are presented, as well as those on the synthetic crown ethers 18-crown-6, diaza-18-crown-6, and benzo-15-crown-5. No fragment ions are detected, and the measured ion selectivity is in good qualitative agreement with published stability constants of the complexes. The observed specific recognition of silver ions by diaza-18-crown-6 can be rationalized by the principle of hard and soft acids and bases, which predicts stable complexes when the polarizabilities of Lewis acid and base are similar. Weak, noncovalent interactions like those in the sandwich complex ...
|p|Icotinib Hydrochloride is a potent and highly selective inhibitor of epidermal growth factor receptor tyrosine kinases (EGFR-TKI) with IC50 value of 5 nM.|br /|EGFR is an oncogenic driver which is expressed on the cell surface of normal cells and cance
The present thesis describes the construction of differently shaped di- to hexavalent crown ethers by coordination-driven self-assembly and their investigations according (pseudo¬-) rotaxane formation and kinetics of the dynamic ligand exchange. First, bipyridine and terpyridine ligand moieties as well as crown ether host moieties were synthesized. Then a toolbox of crown ether-substituted bi- and terpyridines was created by connecting the host and ligand moieties by Sonogashira reaction. In order to obtain predefined structures in the desired assemblies the ligands were designed applying the directional bonding approach. The prepared ligands were connected by coordination-driven self-assembly with several 3d transition metal (Fe(II), Co(II), Ni(II)) and ruthenium(II) ions providing the corresponding di- to hexavalent crown ether-substituted complexes. Whereas complex formation with ruthenium(II) ions provides kinetically inert complexes with moderate yields, coordination of the ligands to 3d ...
Complexes of dibenzo-18-crown-6 (DB18C6, host) with water, ammonia, methanol, and acetylene (guest), formed in supersonic jets, have been characterized by using various spectroscopic methods: laser induced fluorescence (LIF), UV-UV hole-buning (UV-UV HB), and IR-UV double resonance (IR-UV DR) spectroscopy. Firstly, we reinvestigated the conformations of bare DB18C6 (species m1 and m2) and the structure of DB18C6-H2O (species a) [R. Kusaka, Y. Inokuchi, T. Ebata, Phys. Chem. Chem. Phys., 2008, 10, 6238] by measuring the IR-UV DR spectra in the region of the methylene CH stretching vibrations. From the IR-UV DR spectra, it was found that the IR spectral feature of the methylene CH stretch of DB18C6-H2O is clearly different from those of bare DB18C6 conformers, suggesting that DB18C6 changes its conformation when it forms the complex with a water molecule. With the aid of Monte Carlo simulation for extensive conformational search and density functional calculations (at B3LYP and M05-2X/6-31+G* ...
A variety of novel cage-functionalized pyridyl containing crown ethers have been prepared for use in selective alkali metal complexation studies. A highly preorganized, cage-functionalized cryptand also has been designed and has been synthesized for use as a selective Li+ complexant. The alkali metal picrate extraction profiles of these cage-functionalized crown ethers also have been studied. Novel cage-functionalized diazacrown ethers have been prepared for selective alkali metal complexation studies. Alkali metal picrate extraction experiments have been performed by using this new class of synthetic ionophores to investigate the effects of cage-annulation and the influence of N-pivot lariat sidearms upon their resulting complexation properties. Novel pyridyl containing calix[4]arene receptors were prepared. Analysis of their respective 1H NMR and 13C NMR spectra suggests that calix[4]arene moieties in the ligand occupy the cone conformation. The complexation properties of these host molecules were
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Macrocyclic molecules such as crown ethers have useful ion-binding properties, and their incorporation into a matrix can create materials with new properties, especially if these ring structures are left free for binding metals. Sharma and Clearfield have now found that derivatized crown ethers bearing a phosphonate group can self-assemble into well-defined leaflet structures in the presence of the divalent metal ions Co2+ and Cd2+. In the Co2+ complex (2), the metal does not coordinate with the phosphonates; the self-assembly proceeds through hydrogen bonding to form a polyphosphonate chain. In the Cd2+ complex, the Cd cations form part of a more complicated one-dimensional polymer network.-PDS. J. Am. Chem. Soc.122, 1558 (2000).. ...
Actually, anions are not unstable in organic phases per se. There is no intrinsic physical property of organic phases that would make anions inherently unstable: the main problem is that most heteroatoms in organic solvents are more electronegative than carbon and therefore carry a slightly negative charge which attracts cations more easily than anions.. Most organic phases are best classified as ionophobe, however. They will not like cations or anions in their vicinity. Remember that organic phases are typically mainly hydrocarbons with the odd heteroatom, so they have a low polarisablility. Water, on the other hand, is a highly polarised dipole and able to stabilise both cations and anions easily with the appropriate side of the water molecule.. Now if we add a phase transfer catalyst to a biphasic mixture of water and an organic solvent - typical examples would be $\ce{Bu4N+ I-}$ or crown ethers - then these will readily transfer themselves into the organic phase. In the case of crown ethers, ...
Calculated speciation curves for (a) 3,5-dnba and (b) 4-aba in methanol. Lines between points have been added as a guide to the eye. ...
Fingerprint Dive into the research topics of Meridional vs. facial coordination geometries of a dipodal ligand framework featuring a secondary coordination sphere. Together they form a unique fingerprint. ...
Icotinib is approved for the treatment for EGFR mutation-positive, advanced or metastatic non-small cell lung cancer (NSCLC). Upon initial approval, icotinib was indicated as a second-line or third-line treatment for patients who have failed at least one prior treatment with platinum-based chemotherapy. In 2014, icotinib was approved to treat NSCLC patients with EGFR mutation regardless of past chemotherapy use.[6] The ICOGEN trial was a double-blind, head-to-head phase III study comparing icotinib with gefitinib in all-comers. From 27 centers in China, 399 patients were randomized between the two treatments testing for a primary objective of progression-free survival and secondary objectives of overall survival, time to progression, quality of life, percentage of patients who achieved an objective response, and toxic effects. The ICOGEN results showed icotinib to have a median PFS of 4.6 months (95% CI 3.5 - 6.3) as compared to gefitinib which has a PFS of 3.4 months (95% CI 2.3 - 3.8). After ...
A novel fluorescent pH sensor with tunable response range was designed based on highly fluorescent 3,4:9,10-perylene tetracarboxylic ammonium, which could coordinate the paramagnetic Fe(3+) ions to turn off its fluorescence and could also release Fe
Process for the preparation of compounds of the formula (1) ##STR1## in which R.sub.1 denotes a phenyl or naphthyl radical which can be substituted by alkyl, cycloalkyl, alkoxy, aryloxy, arylazo or nitro groups or halogen atoms, and R.sub.2 denotes a hydrogen atom or a phenyl or naphthyl radical which can be substituted by alkyl, cycloalkyl, alkoxy, aryloxy, arylazo or nitro groups or halogen atoms, or denotes an alkyl (C.sub.1 -C.sub.8) radical, by condensation, at between 100.degree. C. and 300.degree. C., of perylene-3,4,9,10-tetracarboxylic dianhydride or a monoanhydride monoimide of the formula (2) ##STR2## in which R.sub.2 has the abovementioned meaning, with an arylamine of the formula (3)in which R.sub.1 has the abovementioned meaning, in the presence of dialkylamines of the formula (4) ##STR3## in which R and R
Level 1: Standard whole brain radiation therapy plus icotinib 125 mg Tid (375 mg per day) from day1 until disease progression or intolerable toxicity.. Level 2: Standard whole brain radiation therapy plus icotinib 250 mg Tid (750 mg per day) from day1 until disease progression or intolerable toxicity.. Level 3: Standard whole brain radiation therapy plus icotinib 375 mg Tid (1125 mg per day) from day1 until disease progression or intolerable toxicity.. Level 4:Standard whole brain radiation therapy plus icotinib 500 mg Tid (1500 mg per day) from day1 until disease progression or intolerable toxicity. ...
Theoretical Study on the Extraction of Alkaline Earth Salts by 18-Crown-6: Roles of Counterions, Solvent Types and Extraction Temperatures
Methyl기를 포함하는 새로운 5종의 crown ether를 합성하였다. 2,3,4,5: 9,10,11,12-Dibenzo-8,8-dimethyl-15,18,1-trioxacycloeicosane, 2,3,4,5: 9,10,11,12-dibenzo-8,8-dimethyl-15,18,21,1-tetraoxacyclotricosane, 2,3,4,5 : 9,10,11,12-dibenzo-8,8-dimethyl-15,18,21,24,1-pentaoxacyclohexacosane, 2,3,4,5 : 9,10,11,12 : 22,23,24,25 : 29,30,31,32-tetrabenzo-8,8,28,28-tetramethyl-15,18,21,35,38,1-hexaoxacyclotetracontane 그리고 2,3,4,5 : 9,10,11,12 : 25,26,27,28:32,33,34,35-tetrabenzo-8,8,31,31-tetramethyl-15,18,21,24,38,41,44,1-octaoxacyclohexatetracontane은 (M = Na, K)존재하에서 4,4-isopropylidenediphenol과 di-, tri- 그리고 tetraethyleneglycol ditosylate의 반응에 의해 합성하였다. Diethyleneglycol ditosylate, triethyleneglycol ditosylate, tetraethyleneglycol ditosylate는 NaOH존재하에서 diethyleneglycol, triethyleneglycol 그리고 tetraethyleneglycol과 p-toluenesulfonylchloride의 반응에 의해 합성하였다 ...
The isolation and X-ray structure of an adduct formed between 18-crown-6 and cisplatin, (D. R. Alston, J. F. Stoddart, and D. J. Williams), J. Chem. Soc., Chem. Commun. 1985, 9, 532-533. ...
Buy 4-(2,4-Dinitro-6-trifluoromethylphenyl)-aminobenzo-15-crown-5 (CAS 78857-86-0), a product for proteomics research, from Santa Cruz Biotechnology.
A set of four hybrid host-guest complexes based on the inorganic crown ether analogue [H12W36O120]12− ({W36}) have been isolated and characterised. The cluster anion features a central rigid binding site made up of six terminal oxygen ligands and this motif allows the selective binding of a range of alkali and alkali-earth-metal cations. Here, the binding site was utilised to functionalise the metal oxide-based cavity by complexing a range of protonated primary amines within the recognition site. As a result, a set of four hybrid organic-inorganic host-guest complexes were obtained whereby the interactions are highly directed specifically within this cavity. The guest cations in these molecular assemblies range from the aromatic 2-phenethylamine (1) and 4-phenylbutylamine (2) to the bifunctional aromatic p-xylylene diamine (3) and the aliphatic, bifunctional 1,6-diaminohexane (4). Compounds 1-4 were structurally characterised by single-crystal X-ray diffraction, elemental analysis, flame ...
The first part of this work deals with the interactions of amino acids and neutral macrocyclic ligands (18-crown-6 and cryptand 222). Solubilities and Gibbs energies of solution of several amino acids and their complexes with 18-crown-6 in acetonitrile, as well as of some amino acid ester salts in chloroform have been determined at 298.15 K. An increase in the solubility data for the amino acid complexes relative to the free amino acids has been found, as a result of the interactions of the guest molecules with the macrocyclic ligands. Stability constants, Gibbs energies, enthalpies and entropies of complexation of a series of L- and D-amino acids with 18-crown-6 and with cryptand 222 in methanol at 298.15 K were obtained by titration calorimetry. The similar Gibbs energies of complexation found for these systems are the result of an enthalpy-entropy compensation effect. No significant differences have been found between the thermodynamic parameters of complexation of the L- and D-amino acids ...
A general review on macrocyclic ligands with particular emphasis to dibenzocryptand 222 and dibenzo 18 crown 6 is given in the first part of the thesis (Chapter 1). This is followed by an exhaustive literature survey on the stability constants (hence free energies of complexing), enthalpies and entropies of metal cations with cryptands (dibenzocryptand 222, benzocryptand 222, cryptand 222) and crown ethers (dibenzo 18 crown 6, benzo 18 crown 6, 18 crown 6) in water and in non-aqueous solvents at 298.15 (Chapter 2). The experimental part (Chapter 3) also includes a detailed description of the principals involved in calorimetry as well as the methods used for the calculation of reaction enthalpies. Stability constant data for alkali-metal and silver cations with dibenzocryptand 222 in five dipolar aprotic solvents (N,N dimethyl-formamide, dimethylsulphoxide, acetonitrile, propylene carbonate and nitromethane) at 298.15 K are reported. These data are used to calculate the standard free energies of ...
TY - JOUR. T1 - Nanosized thermometric NMR sensors based on the paramagnetic complex ion pairs of lanthanides(III) for temperature determinations in low-polar nonaqueous solutions. AU - Babailov, S. P.. PY - 2008/5. Y1 - 2008/5. N2 - For temperature determination in solutions it is suggested that the temperature dependence of the paramagnetic lanthanide-induced shifts (LIS) in the NMR spectra on the ligand nuclei be used for [Ln(PTA)2(18-crown- 6)]+[Ln(PTA)4]- complex ion pairs formed in CCl4, CDCl3, CD2Cl2, CD 3C6D5, and C2D3N type low-polar solvents (Ln = La, Ce, Pr, Nd, Eu; PTA is the pivalyltrifluoroacetonato anion). It was found experimentally that the [Ln(PTA)2(18-crown-6)]+ complex cation molecules (Ln = Ce and Pr) proved most suitable for use as nanosized (≈1.1 nm) probes for temperature determinations in nonaqueous solutions. A linear dependence of the LIS on the 1H nuclei of different groups and the difference between the LIS corresponding to the CH2 groups of the 18-crown-6 ...
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Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice ...
TY - GEN. T1 - Sodium ion effect on photoinduced electron transfer of porphyrin-crown ether-affixed quaterthiophene-[60]fullerene triad as a gated molecular switch. AU - Araki, Yasuyuki. AU - Zhang, Huimin. AU - Ito, Osamu. AU - Oike, Takuro. AU - Kurata, Tomoyuki. AU - Takimiya, Kazuo. AU - Otsubo, Tetsuo. AU - Aso, Yoshio. PY - 2007. Y1 - 2007. N2 - A porphyrin-quaterthiophene-fullerene triad, in which the center of the quaterthiophene spacer is additionally bridged with a crown ether chain in a sash manner (abbreviated as H2P-(2T(crown)2T)-CM), has been newly synthesized. Photoinduced charge-separation (CS) and charge-recombination processes in the absence and presence of Na+ have been investigated by time-resolved fluorescence and transient absorption spectroscopic methods. Upon photo-excitation of H2P-(2T(crown)2T)-C60 in benzonitrile, CS via 1H2P* generating H 2P*+-2T(crown)2T-C60*- took place, followed by a hole shift to a more energetically stable H 2P-(2T(crown)2T)*+-C60* -. In the ...
G. S. Zabrodina,@ M. A. Katkova, E. V. Baranov, G. Yu. Zhigulin, and S. Yu. Ketkov. G.A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, 603905 Nizhny Novgorod, Russia. @Corresponding author E-mail: [email protected] Dedicated to Professor Dieter Wöhrle on the occasion of his 80th Birthday. DOI: 10.6060/mhc190866z. Macroheterocycles 2019 12(3) 300-306. Polynuclear metallamacrocyclic complexes named as metallacrowns are considered as a promising exceptional class of macroheterocyclic compounds that structurally resembles crown ethers. In this communication, we report a general synthetic approach and characterization of the first metallamacrocyclic Bi(III)-Cu(II) 15-MC-5 complex derived from pyrazinohydroxamic acid. The molecular and crystal structures of complex were determined from single-crystal X-ray diffraction studies. The single‐crystal structure reveals the classic metallamacrocyclic 15‐MC‐5 configuration. The Bi(III) ion is located at the center of the ...
0066] In a preferred embodiment of this application, the chelating agent employed for the preparation of solvent based compositions is selected from the group comprising polyols, gluconates, sorbitals, mannitols, carbonates, heptonates, hydroxamates, catechols, α-amino carboxylates, alkanolamines, metal-ion sequestrants, hydroxy-carboxylic acids, aminocarboxylic acids, amino polycarboxylic acids, polyamines, polyphosphates, phosphonic acids, crown ethers, amino acids, polycarboxylic acids, cyclodextrin, phosphonates, polyacrylates or polymeric polycarboxylates and condensed phosphates. However, the particular sequestering or chelating agents of the present application would include but are not limited to acetic acid, adenine, adipic acid, ADP, alanine, alanine, albumin, arginine, ascorbic acid, asparagine, aspartic acid, ATP, benzoic acid, n-butyric acid, casein, citraconic acid, citric acid, cysteine, dehydracetic acid, desferri-ferrichrysin, desferri-ferrichrome, desferri-ferrioxamin E, ...
A method and apparatus for detecting contaminants in an aqueous flow. The method includes the steps of providing a conduit having at least one collection portion upon which is disposed a selective film, disposing the aqueous flow through the conduit, attracting contaminants to the collection portion such that they are bonded to the selective film, and detecting a contaminant, or contaminants, based upon a predetermined property of the plurality of contaminants bonded to the ion collection portion. The selective film may include a molecularly imprinted polymer, a crown ether, an antibody selective for biological contaminants, such as Giardia Lamblia and cryptosporidia, or for detecting organics such as dioxin or furan, a cyclodextrin, or a cyclophane. The apparatus includes a conduit having an collection portion with a selective film disposed thereon, a sensor that senses contaminants collected on the collection portion and sends a signal corresponding to a value of a predetermined property of the
Silicone grease is widely used as a temporary sealant and a lubricant for interconnecting ground glass joints, as is typically used in laboratory glassware. Although silicones are normally assumed to be chemically inert, several historically significant compounds have resulted from unintended reactions with silicones.[3][4] The first salts of crown ethers (OSi(CH3)2)n (n = 6, 7) were produced by reactions of organolithium and organopotassium compounds with silicone greases[5] or the serendipitous reaction of stannanetriol with silicone grease to afford a cage-like compound having three Sn-O-Si-O-Sn linkages in the molecule.[6]. Lubrication of an apparatus with silicone grease may result in the reaction mixture being contaminated with the grease. The impurity may be carried through purification by chromatography in undesirable amounts. In NMR spectroscopy, the methyl groups in polydimethylsiloxane display 1H and 13C chemical shifts similar to trimethylsilane (TMS), the reference compound for ...
a Photovoltaic metrics of devices without Cs doping (control), with homogeneous Cs doping, after treatment with DB21C7-CsI (target) and after just crown ether (DB21C7) treatment. b J-V curves of the champion control and target PSCs. The inset shows the maximum power point tracking data. An anti-reflection coating was used for the champion devices. c Photoluminescence spectral photon flux Φ measured on full devices. d Breakdown of losses derived from the J-V curves in b; radiative JSC and VOC losses are shown in green and grey, respectively; non-radiative VOC and FF losses in black and red; transport losses affecting FF in blue. ...
A binucleating ligand has been prepared that contains an SCS pincer and three oxygen donor atoms in a partial crown ether loop. To enable metalation with Ni0, a bromoarene precursor was used and resulted in the formation of a nickel-bromide complex in the SCS pincer portion of the ligand. Reaction of the nic
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High nitrogen materials are sought as a potentially dense, powerful but insensitive explosive and propellant ingredients. Elucidation of the structure and chemistry of dibenzo-1 ,3a,4,6a-tetraazapentalenes has continued, with particular attention to a putative C12N12O12 derivative initially prepared at the University of New Orleans. This research contributed substantially to identification of the actual o-quinone hydrate structure, and explanation of the apparently anomalous explosive insensitivity of the material. Synthesis of the novel 5,7-dinitrobenzo-1 ,2,3,4-tetrazine-1,3-dioxide has been repeated, its structure has been confirmed, and preliminary evaluation of its explosive sensitivity has been completed.*NITROGEN
Balundgi, R. H. ; Chakravorty, A. (1973) New mixed-ligand complexes of cobalt(II) Inorganic and Nuclear Chemistry Letters, 9 (10). pp. 1045-1048. ISSN 0020-1650 Full text not available from this repository.. Official URL: http://www.sciencedirect.com/science/article/pii/0.... Related URL: http://dx.doi.org/10.1016/0020-1650(73)80108-4 ...
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This week, I made a birthday crown for Ember. It was a rare opportunity... As my sons primary caregiver, I do most of my crafting in the spaces between
Our research program uses fundamental principles of molecular design to address some of the grand challenges in the fields of small molecule activation and catalysis. We are interested in developing strategies to reversibly store energy in the form of chemical bonds, and also to rapidly convert abundant chemical (bio)feedstocks into value-added chemicals and fuels.. The overarching themes of our research program are to (a) understand how to exploit carefully positioned secondary-sphere sites to control reactivity, and (b) develop transition metal compounds to promote otherwise difficult transformations of small molecule chemical feedstocks such as N2, CO2, O2, and CO.. We are working to establish new ways by which molecular catalysts can be tuned by the incorporation of pendent functional groups within a metals secondary coordination sphere environment. We are using these appended functional groups (hydrogen bond donor/acceptors, or Lewis acid/bases) to augment reactivity of the central ...
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Sousa, Lynn R.; Larson, James M. (1977-01-01). "Crown ether model systems for the study of photoexcited state response to ... Interaction of saxitoxin with the sensor's crown ether moiety kills its PET process towards the fluorophore and fluorescence is ... Silva, A. Prasanna de; Silva, Saliya A. de (1986-01-01). "Fluorescent signalling crown ethers; 'switching on' of fluorescence ...
Possibly, the crown ethers will serve, in a small way, to mark my footprint on earth" and Izatt believing this too shares ... It was while working on this research that Pedersen made his discovery of crown ether. Through studying the bio[2-(o- ... Izatt was looking forward to the possibilities of studying these crown ethers with his thermionic titration technique. Izatt ... Pedersen, Charles J (1988). "The Discovery of Crown Ethers". Science. 241 (4865): 536-540. Bibcode:1988Sci...241..536P. doi: ...
10.1021/ja00538a026 Photoresponsive crown ethers. 2. Photocontrol of ion extraction and ion transport by a bis(crown ether) ... 85550-7 Photoresponsive crown ethers. 1. Cis-trans isomerism of azobenzene as a tool to enforce conformational changes of crown ... Preparation of a crown-ether by photocycloisomerization Jean-Pierre Desvergne and Henri Bouas-Laurent J. Chem. Soc., Chem. ... construct a crown ether already incorporating the anthracene units (an anthracenophane) and also study ion uptake vs ...
Thiacrown ligands are analogous to crown ethers. The best studied thiacrown ligands have the formula (SCH2CH2)n (n = 3,4,5,6). ... Unlike ethers, thioethers occasionally serve as bridging ligands. The complexes Nb2Cl6(SMe2)3 is one such example. It adopts a ... complexes with 12-16-membered cyclic tetrathia ethers". Inorganic Chemistry. 22 (24): 3661-3670. doi:10.1021/ic00166a033. Shaw ...
... "crown" compounds with variety of ring sizes, a number of ether oxygens and substituent groups. Shortly after crown compounds, ... Classic examples are crown ethers and porphyrins. Macrocyclic ligands exhibit particularly high affinity for metal ions. ...
Dications Stabilized by Azamacrocycles and Crown Ethers". Angewandte Chemie. 121 (28): 5254-5256. doi:10.1002/ange.200901247. ...
"Cation Complexation and Conductivity in Crown Ether Bearing Polyphosphazenes". Macromolecules. 29 (23): 7544-7552. Bibcode: ... H. R. Allcock; S. R. Pucher; M. L. Turner; R. J. Fitzpatrick (1992). "Poly(organophosphazenes) with Poly(alkyl ether) Side ... Other side groups, such as non-fluorinated alkoxy or oligo-alkyl ether units, yield hydrophilic or hydrophobic elastomers with ...
In 1976, less than ten years after the discovery of crown ether, Cram et al. developed a functionalized binapthyl crown ether ... The catalyst makes use the crown ether motif's ability to capture cation to bind to the ammonium ion part of the substrate and ... A notable example of catalysts that employ this mechanism is Jean-Marie Lehn's crown ether. In addition, catalysts based on ... Self-assembled molecules have an advantage over crown ether and cyclodextrin in that they can capture significant larger ...
Ge(II) cationic species have been isolated with several crown ether ligands, including [12]crown-4, [15]crown-5, and [18]crown- ... such as crown ethers and [2.2.2]cryptand. Crown ethers and cryptands are typically known for their ability to bind metal ... In the Ge(II) crown ether complexes presented above, only the sandwich complex with [12]crown-4 clearly bears a ... germanium crown ether complexes can adopt different geometries and cation charges depending on the size of the crown ether and ...
The crown ethers are often generated in the presence of an alkali metal cation, which organizes the condensing components by ... Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature ... Pedersen, Charles J. (1988). "Macrocyclic Polyethers: Dibenzo-18-Crown-6 Polyether and Dicyclohexyl-18-Crown-6 Polyether". ... from flexible crown ethers to rigid cyclophanes". Chemical Society Reviews. 46 (9): 2459-2478. doi:10.1039/c7cs00185a. PMID ...
... from flexible crown ethers to rigid cyclophanes". Chemical Society Reviews. 46 (9): 2367-2650. doi:10.1039/c7cs00185a. PMID ...
Crown ethers, like 15-crown-5, may be used as a phase-transfer catalyst. Sodium content of samples is determined by atomic ... Sodium forms complexes with crown ethers, cryptands and other ligands. For example, 15-crown-5 has a high affinity for sodium ... because the cavity size of 15-crown-5 is 1.7-2.2 Å, which is enough to fit the sodium ion (1.9 Å). Cryptands, like crown ethers ...
Crown ethers arise from dialkylations that are templated by alkali metals. Other template reactions include the Mannich and ... The alkali metal-templated syntheses of crown ether syntheses are notable exceptions. Metal Phthalocyanines are generated by ... The phosphorus analogue of an aza crown can be prepared by a template reaction. Where it is not possible to isolate the ... George W. Gokel; Donald J. Cram; Charles L. Liotta; Henry P. Harris; Fred L. Cook (1988). "18-Crown-6". Organic Syntheses.; ...
Many synthetic ionophores are based on crown ethers, cryptands, and calixarenes. Pyrazole-pyridine and bis-pyrazole derivatives ...
Crown-ethers bind to polyamine complexes through their second coordination sphere. Polyammonium cations bind to the nitrogen ...
PTs with pendant crown ether functionalities exhibit properties that vary with the alkali metal. and main-chain. Polythiophenes ... Bäuerle, Peter; Scheib, Stefan (1993). "Molecular recognition of alkali-ions by crown-ether-functionalized poly(alkylthiophenes ... selective ionochromic response in crown ether-containing polythiophenes". Journal of the American Chemical Society. 115 (25): ... and not diethyl ether, xylene, acetone, or formic acid), and speculated that the polymerization may occur at the surface of ...
In the research lab, crown ethers are used for this purpose. Polyethylene glycols are more commonly used in practical ... and the sodium cyanide does not dissolve well in the ether. Upon the addition of small amounts of hexadecyltributylphosphonium ...
... has also been the director and co-director of many Ph.D.'s •Chemistry: Biomimetic chemistry, crown ethers ... crown-ether and cryptates). After his Ph.D. (1978) he spent one year at ONERA for his military service. He was then hired by ...
"Complexation of caesium and rubidium cations with crown ethers in N,N-dimethylformamide". Polyhedron. 15 (21): 3897-3903. doi: ...
Ions studied by argon tagging include the hydrated proton H+(H2O)nAr with n=2 to 5, hydrated 18-crown-6 ether alkali metal ions ... "Probing Ionophore Selectivity in Argon-Tagged Hydrated Alkali Metal Ion-Crown Ether Systems". Journal of the American Chemical ...
... such as crown ethers of different sizes. The property of these peptide-crown channels depend strongly on the identity of the ... The above diagram illustrates one example, where a crown-ether was fixed across the mouth of the ion-passing portal. This ... Jochen R. Pfeifer; Philipp Reiß; Ulrich Koert (2005). "Crown Ether-Gramicidin Hybrid Ion Channels: Dehydration-Assisted Ion ...
Crown ethers. neutral. primarily for alkali and alkaline earth metal cations 2,2,2-cryptand. hexadentate. primarily for alkali ...
Since the salt is poorly soluble in nonpolar solvents, crown ethers are typically used. The tetraethylammonium salt is also ...
The first salts of crown ethers (OSi(CH3)2)n (n = 6, 7) were produced by reactions of organolithium and organopotassium ... Jamie S. Ritch and Tristram Chivers (2007). "Silicon Analogues of Crown Ethers and Cryptands: A New Chapter in Host-Guest ...
A bodipy dye attached to a crown-ether and two pyridyl groups separated by spacers (as shown below) works according to an AND ... Excess acid locks the crown ether by protonation and again the complex is dethreaded. A full adder system based on fluorescein[ ... This process is accompanied by an increase in emission intensity at 343 nm resulting from freed crown ether. Added ... phenyldiaminocarboxylate and crown ether receptors. The processing mode operates similarly as discussed above - fluorescence is ...
"Critical evaluation of stability constants and thermodynamic functions of metal complexes of crown ethers". Pure Appl. Chem. 75 ...
Classically artificial enzymes bind substrates using receptors such as cyclodextrin, crown ethers, and calixarene. Artificial ...
1,2-Dioxane 1,3-Dioxane Dioxolane 9-crown-3 Crown ether Dioxane tetraketone Oxalic anhydride Sodium laureth sulfate Dioxanone ... Dioxane resembles a smaller crown ether with only two ethyleneoxyl units. In the 1980s, most of the dioxane produced was used ... It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane ... Like some other ethers, dioxane combines with atmospheric oxygen upon prolonged exposure to air to form potentially explosive ...
Chan, Matthew (31 July 2018). "Philippines Dominate MSC 2018 with Aether Main Bringing Home the Crown!". IGN (SEA). Archived ...
... elastomer Viton fluoroelastomer Kalrez perfluoroelastomer Vamac ethylene acrylic elastomer Nobel Prize work on crown ethers by ...
Georgia, New Jersey, and Massachusetts also appointed him as their agent to the Crown. Franklin lodged in a house in Craven ... experimented by continually wetting the ball of a mercury thermometer with ether and using bellows to evaporate the ether. With ... proving that they had encouraged the Crown to crack down on Bostonians. Franklin sent them to America, where they escalated the ... that was known for its revolutionary sentiments and criticisms of the policies of the British Parliament and the Crown. He ...
1384 - Jadwiga is crowned King of Poland, although she is a woman. 1590 - Prince Gesualdo of Venosa murders his wife and her ... 1846 - William T. G. Morton administers ether anesthesia during a surgical operation. 1847 - The novel Jane Eyre is published ...
Yuvraj (Crown Prince) Karan Singh after serving as the President of Jammu and Kashmir from 1952-64 would go on to become the ... Kalhana's Rajatarangini makes no mention of a kingdom by this name, but it could have been referred to by its capital (ether ... His son Yuvraj (Crown Prince) Karan Singh too abdicated and was elected Sadr-e-Riyasat ('President of the Province') and ... Crown Prince) Karan Singh, who subsequently accepted the position of a constitutional head of state (Sadr-i-Riyasat) and ...
... and the 5.0L LTD Crown Victoria. These vehicles could operate on either gasoline or methanol with only one fuel system. ... for bioethanol fuel in the United States was stimulated by the discovery in the late 90s that methyl tertiary butyl ether (MTBE ... demand for ethanol fuel in the United States was stimulated by the discovery in the late 1990s that methyl tertiary butyl ether ...
Book of Mormon, Ether 3:22. Quinn (1998, pp. 195-196). Book of Mormon, Ether 4:5. According to Martin Harris, anyone who looked ... "The mode of procedure consisted in Joseph's placing the Seer Stone in the crown of a hat, then putting his face into the hat, ... recorded by Ether on a set of 24 plates later found by Limhi, and then "sealed up". Book of Mormon, Ether 1:2. According to ... 11-12). Smith's dictated text of the Book of Ether (chapter 2) also made reference to three witnesses, stating that the plates ...
During British rule in India, the crown found that Madras had some of the most talented and intellectual artistic minds in the ... Long after personal, political and professional tensions have fragmented the Surrealist group into thin air and ether, Magritte ...
Zinc porphyrin could also bind to oxidized SWNHs through covalent bonding with a spacer and a crown ether. This nanohybrid ...
The expedition was financed by the Spanish Crown. On August 10, 1519, the five ships under Magellan's command departed from ... and aether. In proposition 2 of the First Book of his treatise "On floating bodies," Archimedes demonstrates that "The surface ...
Aepytus Aeschines Aeschines of Sphettus Aeschylus Aeschylus of Rhodes Aesop Aethalides Aether (classical element) Aether ( ... On Spirals On the Chersonese On the Crown On the Equilibrium of Planes On the False Embassy On the Halonnesus On the Heavens On ...
Neither the crown (fruit, mescal button) of the Peyote cactus nor the roots of the plant Mimosa hostilis, Peganum Harmala that ... Circa 1999, the Government of Spain proposed amending Schedules I and II to include isomers, esters, ethers, salts of isomers, ... Neither the crown (fruit, mescal button) of the Peyote cactus nor the roots of the plant Mimosa hostilis nor Psilocybe ... esters and ethers, and any "substance resulting from modification of the chemical structure of a substance already in Schedule ...
Flamini, Roland (1994). Thalberg: The Last Tycoon and the World of M-G-M. New York: Crown Publisher, Inc. ISBN 0-517-58640-1. ... These cuts included the administration of ether in the dental scenes and certain instances of foul language. Although these ...
Melf is known to have authored or co-authored the following works: Treatise of Universal Astronomy Weapons of the Ether (with ... the infamous wizard featured in the module White Plume Mountain using a magical device called the Crown of Mortality. According ...
Aether History: Practical aether travel as we know it today all began with Professor Etienne Moreau, who in 1860 hypothesised ... Smith, G. E. (January-February 1989). "The Royal Crown Colony of Syrtis Major?: The Imperial Space Age is Here!". Space Gamer/ ... In 1868 Edison perfected his prototype and called it an aether propeller, a device that manipulated the aether by generating an ... In the setting, Thomas Edison invented an "ether propeller" which could propel ships through the "luminiferous aether" (the ...
In 1961, the New York Tribune listed an exhibition of her recent paintings in Crown Gallery, 881 Seventh Ave, New York. On her ... Peavy here suggest brightly colored embryos or sleek flying saucers drifting among amniotic fluids or intergalactic ethers." As ...
The Dragon Crown is a magical artifact of great power. In ages long past, the powerful sorcerer Kirun created the crown using ... Alyx retreats into her mind to call for help from the Black Dragon in the ether realm chamber of her secret society. The black ... The Crown heads don't want him spreading word of Chytrine's promise to return. Without his mask, he is without his identity so ... Chytrine wins out in the end with the help of her dragon and takes hold of the Fortress and the two other pieces of the Crown ...
Alkali metal cations bound by crown ethers are common lipophilic countercations, as illustrated by [Li(12-crown-4)2]+. Many ...
1987: Charles J. Pedersen wins the Nobel Prize in Chemistry for his methods of synthesizing crown ethers 1988: President Ronald ...
NDIs are used ins supramolecular chemistry due to their tendency to form charge-transfer complexes with crown ethers, e.g. to ...
The first usage is in a narrative about Crown Prince Dan from the state of Yan (d. 226 BCE) and the future Emperor Qin Shi ... Things belonging to the same category naturally attract each other [類同相召]; things that share the same ethers [qi 氣] naturally ... in the purer ether, when A acts on B, B will not only be moved by it, but will respond actively. (1958: 38) Noting that Chinese ... But if inert matter is only the essentially active ether ch'i in an impure state, this kind of action will only be of minor ...
Kansas City proposed to relocate the NCAA back downtown near the Crown Center complex and would locate the visitors' center in ... vinyl ether)s for coating applications". INFORM: International News on Fats, Oils, and Related Materials. 26 (7): 472-475. doi: ...
... and crown ethers. Although nonactin (and all nactins) exhibits an especially high cation selectivity for potassium ions over ...
Doc then informs the riders that the time vehicle Biff has stolen had a sub-ether time-tracking scanner; that way whatever time ... Once inside, Doc reveals some of the inventions he had been working on, including his "crowning achievement" - an 8-passenger ...
Although the holy persons are signified with crowns of light, they appear otherwise terrestrial. If not for their crowns of ... seeded the Italian pictorial revolution that extracted figures from the gilded ether of Byzantine iconography into pictorial ...
Mild Lewis basic solvents such as THF and diethyl ether do not break up the tetrameric structure, which persists in the solid, ... For example, DMF, DMSO, hexamethylphosphoramide (HMPA), and 18-crown-6 interact with the potassium center, enhancing the ... Its steric bulk inhibits the group from participating in nucleophilic addition, such as in a Williamson ether synthesis or an ...
See D&C 57:1-2; 84:1-2; Ether 13:3-6, 10; 2 Ne 20:22; and Art of Faith 1:10. Montgomery, James A. (1907). The Samaritans, The ... and on the crown of the head of him that was separate from his brethren ... (Gen 49:22-26 KJV) Thus, before he died, the old ... "And there shall they fall down and be crowned with glory, even in Zion [the New Jerusalem of the Americas], by the hands of the ...
The Treaty of Waitangi was between the Māori and the British Crown and was first signed in 1840. This list contains notable ... protests against employers ether for the disruption caused or their results on society and working conditions. It also includes ...
... to the carbonyl groups that line each end of the cavity and can interact with cations in a similar fashion to crown ethers. The ...
"Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation". ...
Crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers ... The smallest crown ether still capable of binding cations is 8-crown-4, with the largest experimentally confirmed crown ether ... aza crown ether thia crown ether 9-Crown-3 Cryptand Metallacrown van der Ham, Alex; Hansen, Thomas; Lodder, Gerrit; Codée, ... Crown ethers are much broader than the oligomers of ethylene oxide; an important group are derived from catechol. Crown ethers ...
Ridge National Laboratory has discovered a way to dramatically increase the selectivity and binding strength of crown ethers by ... Traditional crown ethers have dipoles that do not point directly at the metal, but the dipoles of the crown ethers in graphene ... Crown ethers come in different sizes, so they can accommodate ions of different diameters. In a crown ether, the electric ... limiting the crown ethers selectivity. Despite their flexibility, crown ethers surprisingly cannot adopt an optimal shape to ...
In chemistry, an aza-crown ether is an aza analogue of a crown ether (cyclic polyether). While the parent crown ethers have the ... 2.2.2-Cryptand is an aza-crown of the mixed ether-amine variety. The synthesis of aza crown ethers are subject to the ... Many kinds of aza crown ethers exist. Variable length linkers Aza crowns often feature trimethylene ((CH2)3) as well as ... Lariate crowns The presence of the amine allows the formation of Lariat crown ethers, which feature sidearms that augment ...
Structures of some common crown ethers. Structures of common crown ethers: 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown ... Aza-crowns. "Aza-crowns" consist of crown ethers wherein an ether oxygen has been replaced by an amine group. A well-known ... Crown ethers are heterocyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ... Crown ethers in nature. Crown ethers are not the only macrocyclic ligands that have affinity for the potassium cation. ...
T 0238/88 (Crown ether) of 25.4.1991. European Case Law Identifier:. ECLI:EP:BA:1991:T023888.19910425. ... The term crown ethers is ascribed to cyclic polyethers which, according to the statements in the description, in general ... Claim 1 includes as definitions for linking groups W and W1 and for substituents R to R1 in the crown ether structure the ... pages 11 and 12). Formula LXI is given as a typical example for a crown ether having (alternate) carbon and oxygen atoms in the ...
Strong, specific electrostatic binding of crown ethers may advance sensors, chemical separations, nuclear-waste cleanup, ... Ridge National Laboratory has discovered a way to dramatically increase the selectivity and binding strength of crown ethers by ... This sheet of graphene contains an array of crown ethers that can strongly bind select guest ions or molecules. ...
This chapter provides the diffusion coefficient of dicyclohexano-24-crown-8-ether in ethanol at different concentrations ... Winkelmann J. (2018) Diffusion coefficient of dicyclohexano-24-crown-8-ether in ethanol. In: Lechner M.D. (eds) Diffusion in ... This chapter provides the diffusion coefficient of dicyclohexano-24-crown-8-ether in ethanol at different concentrations ...
34 Crown 10 Ether (26ZJ20)? Graingers got your back. Price:$839.45. Easy ordering & convenient delivery. Log-in or register ...
Get Crown Ethers at Spectrum Chemical. SpectrumChemical.com carries a full line of fine chemicals, lab appliances and lab ... 15-Crown 5-Ether TCI-C0859 , 33100-27-5 , C10H20O5 , TCI America 15-Crown 5-Ether is the cyclic pentamer of ethylene oxide. It ... 4-Acetylbenzo-15-crown 5-Ether TCI-A1603 , 41757-95-3 , C16H22O6 , TCI America 4-Acetylbenzo-15-crown 5-Ether ... 4-Acetylbenzo-18-crown 6-Ether TCI-A1604 , 41855-35-0 , C18H26O7 , TCI America 4-Acetylbenzo-18-crown 6-Ether ...
Crown Ether Complexes of Alkali-Metal Chlorides from SO. [Kirsten Reuter, Stefan S Rudel, Magnus R Buchner, Florian Kraus, ...
... crown-ether or (2) diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. The crown-ether ... We investigate strategies for increasing the thermopower of crown-ether-bridged anthraquinones. The novel design feature of ... crown-ether or (2) diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. The crown-ether ... Increasing the thermopower of crown-ether-bridged anthraquinones A. K. Ismael, I. Grace and C. J. Lambert, Nanoscale, 2015, 7, ...
1-Aza-15-crown 5-Ether 98.0 %, TCI America 1G Chemicals:Organic Compounds:Organic nitrogen compounds:Organonitrogen compounds: ... aza-15-crown-5,1-aza-15-crown 5-ether,1-aza-15-crown-5,1-aza-15-crown,1-aza-4,7,10,13-tetraoxacyclopentadecane. ... aza-15-crown-5,1-aza-15-crown 5-ether,1-aza-15-crown-5,1-aza-15-crown,1-aza-4,7,10,13-tetraoxacyclopentadecane. ...
Contact to Crown Ethers Exporters in India, Crown Ethers Wholesalers, Crown Ethers Distributors and Traders from India. ... Search Indian Crown Ethers Manufacturers and Suppliers Details - ...
The Chemistry of Ethers Crown Ethers Hydroxyl Group and Their Sulphur Analogue, Supplement E, Part 1, Volume 1. ... The Chemistry of Ethers Crown Ethers Hydroxyl Group and Their Sulphur Analogue, Supplement E, Part 1, Volume 1. Saul Patai ( ...
... nanofibers functionalized with dibenzo-18-crown-6 (DB18C6) crown ether and showed the potential of these fibers for the ... The maximum adsorption capacity of the crown ether modified nanofibers for K+ was 0.37 mmol g−1 and the nanofibers followed the ... Polyacrylonitrile (PAN)/crown ether composite nanofibers for the selective adsorption of cations S. Tas, O. Kaynan, E. Ozden- ... Adsorption of Ba2+ ions onto crown ether-modified nanofiber was examined by XPS and the results confirmed the adsorption of the ...
Functionalized Derivatives of Benzo-Crown Ethers. Part 4. Antifungal Macrocyclic Supramolecular Complexes of Transition Metal ... Poly- and mononuclear metal complexes of 2,3,11,12-bis[4-(10-aminodecylcarbonyl)]benzo-18- crown-6 (L) and Cu(II); Ni(II); Co( ... In the newly prepared complexes the crown moiety oxygen atoms of the macrocyclic host did not generally interact with metal ...
The effect observed is shown to vary with the hydrophobicity of the crown ether. Water-soluble crown ethers enhance the ... a result of the exclusion of the crown ether from the resin phase and the formation of cation-crown complexes in the solution ... Effect of crown ethers on the ion-exchange behavior of alkaline earth metals. Toward improved ion-exchange methods for the ... The effect of selected crown ethers on the uptake of alkaline earth cations by sulfonic acid and diphosphonic acid-based cation ...
Y. Kudo, K. Harashima, S. Katsuta, and Y. Takeda, "Solvent extraction of sodium permanganate by mono-benzo 3m-crown-m ethers (m ... Extraction of Sodium Picrate by 3m-Crown-m Ethers and Their Monobenzo Derivatives (m = 5, 6) into Benzene: Estimation of Their ... Y. Kudo, N. Horiuchi, S. Katsuta, and Y. Takeda, "Extraction of cadmium bromide and picrate by 18-crown-6 ether into various ... Y. Kudo, J. Usami, S. Katsuta, and Y. Takeda, "On the difference between ion-pair formation constants of crown ether-complex ...
Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiffs bases and crown ethers have ... Schiffs bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the ... Liquid membrane sensors based on Schiffs bases and crownethers will then be discussed. ... Crown Ether Supramolecule; Potentiometric membrane; Sensor; Ion Selective Electrode; Schiffs Base; Crown Ether ...
... a type of cyclic ether consisting of a ring of carbon and oxygen atoms , with two or more... , Meaning, pronunciation, ... crown ether is in the lower 50% of commonly used words in the Collins dictionary ... a type of cyclic ether consisting of a ring of carbon and oxygen atoms, with two or more carbon atoms between each oxygen atom ...
Calculated speciation curves for (a) 3,5-dnba and (b) 4-aba in methanol. Lines between points have been added as a guide to the eye. ...
Use of crown ethers can also be made in testing e.g.... ... A brief review is given on the use of crown ethers in ... Use of crown ethers can also be made in testinge.g. lithium salts for potassium by extraction as LKpicrate, L being 18-crown-6. ... A brief review is given on the use of crown ethers in solubilizing salts of alkali and alkaline earth ions in organic polar or ... Some comments on extraction analysis of cations complexed with a crown ether. ...
The CH2 vibrational modes of crown ethers have been identified and found to be split due to their interaction with ether oxygen ... Crown Ethers at the Aqueous Solution-Air Interface: 2. Electrolyte Effects, Ethylene Oxide Hydration and Temperature Behaviour ... VSFS, SFG, interface, crown ethers, ethylene oxides, ionic liquids, fatty acids, domains. Nationell ämneskategori Fysikalisk ... The presence of even small amounts of adsorbed crown ethers at the water interface is shown to considerably perturb the water ...
... ... We measured UV photodissociation and IR-UV double-resonance spectra of benzo-crown ether complexes with alkali metal ions (Li ...
... Online Crown Ethers And Phase Transfer Catalysis In ... The online Crown Ethers and Phase explains a previous t fact, and by onwards the most per- Term been by a Baul violence. It ... In online Crown Ethers; pp., service David Lowery holds Info; on fiscal minutes as local books for command and will handle list ... The online Crown Ethers and Phase Transfer Catalysis in Polymer Science can thank not or now. The d enjoys additional) EPs when ...
Solvent Extraction of Sodium Permanganate by Mono-benzo 3m-Crown-m Ethers (m = 5, 6) into 1,2-Dichloroethane and Nitrobenzene: ... by crown ethers (L) into polar. diluents. Then, NaMnO4 was extracted at 25 ?C by benzo-15-crown-5 and -18-crown-6 ethers (B15C5 ... Solvent Extraction of Sodium Permanganate by Mono-benzo 3m-Crown-m Ethers (m = 5, 6) into 1,2-Dichloroethane and Nitrobenzene: ...
... crown ether (15-crown-5 and 18-crown-6) salts of [TcNCl4]- and [MoOCl4]-, and a new refinement of the X-ray structure of [Cs(18 ... 1 crown ether/Cs+ sand-wich cations and isolated [TcNCl4]- anions, could be obtained from reaction of Cs+/18-crown-6 and [ ... Spectra for other crown ether salts are consistent with isolated [TcNCL4]- or [TcNCL4(OH2)]- anions, with dipolar broadening ... The structure consists of an infinite sandwich Cs+ cation/crown ether configuration and polymeric [TcNCL4]- anions, with Tc≡N ...
ion and the aza crown ether. The binding of the ammonium. ion to the aza crown ether increases the emission intensity of. the ... Luminescent Hybrids Combining a Metal Complex and a Crown Ether - Receptors for Peptidic Ammonium Phosphates ... Hybrid compounds combining a luminescent aza crown. ether and 1,4,7,10-tetraazacyclododecane (cyclene) or bis-. (pyridin-2- ... Hybrid compounds combining a luminescent aza crown ether and 1,4,7,10-tetraazacyclododecane (cyclene) or bis- (pyridin-2- ...
MRI Sensing of Neurotransmitters with a Crown Ether Appended Gd3+ Complex * Multiplication of microbes below 0.690 water ... Macrocyclic Gd(3+) Complexes with Pendant Crown Ethers Designed for Binding Zwitterionic Neurotransmitters. Chemistry - A ... Macrocyclic Gd(3+) Complexes with Pendant Crown Ethers Designed for Binding Zwitterionic Neurotransmitters ... ion and the crown ether. The complexes are monohydrated, but they exhibit high proton relaxivities (up to 7.7 mM(-1) s(-1) at ...
  • Crown ethers strongly bind certain cations, forming complexes. (wikipedia.org)
  • Apart from its high affinity for potassium cations, 18-crown-6 can also bind to protonated amines and form very stable complexes in both solution and the gas phase. (wikipedia.org)
  • Those protonated amino groups can bind to the cavity of 18-crown-6 and form stable complexes in the gas phase. (wikipedia.org)
  • In the newly prepared complexes the crown moiety oxygen atoms of the macrocyclic host did not generally interact with metal ions, whereas the two amino groups of the ligand always did. (hindawi.com)
  • We measured UV photodissociation and IR-UV double-resonance spectra of benzo-crown ether complexes with alkali metal ions (Li$^{+}$, Na$^{+}$, K$^{+}$, Rb$^{+}$, and Cs$^{+}$) in a cold, 22-pole ion trap nderline{\textbf{133}}(31), 12256 July 2011. (osu.edu)
  • Hybrid compounds combining a luminescent aza crown ether and 1,4,7,10-tetraazacyclododecane (cyclene) or bis- (pyridin-2-ylmethylamine) (bpa) metal complexes were prepared. (uni-regensburg.de)
  • Addition of SbCl5 (1 mol) to ScCl3 (THF)(3) (1 mol) in acetonitrile followed by in situ addition of a crown ether (1 mol) provides the [ScCl2 (crown)][SbCl6] complexes where crown = 15-crown-5, dibenzo-24-crown-8, dibenzo-30-crown-10, 1-aza-15-crown-5 and 1-aza-15-crown-6. (warwick.ac.uk)
  • The conductance data showed that the stoichiometry of the complexes in most cases is 1:1(ML). It is also demonstrated that the influence of crown ethers is deeply affected by the organic solvent used. (stedj-univerzitetpim.com)
  • We synthetized bis(azacrown ether)s containing an acridinone signalling unit, and we showed that the one having two aza-18-crown-6 ether receptor units is able to form complexes with both 1:1 and 1:2 ligand to metal ion ratios. (mtak.hu)
  • Why macromolecule ligands such as Crown ethers form more stable complexes than open chain ligands? (stackexchange.com)
  • Solvent effects in the metal interchange of crown ether-alkali metal cation complexes. (gc.ca)
  • We have investigated the inhibitory effect of K- crown (18- crown -6 potassium picrate) on photosystem II (PSII)-enriched membrane fragments and O2-evolving core complexes. (bvsalud.org)
  • Cerium(III) complexes of two ligands of a diaza-crown ether with different functional groups as side arms were synthesised and characterised. (sciencereviews2000.co.uk)
  • The solid-state behaviour of four alkali metal TCNQ complexes: (15-crown-5)LiTCNQ ( 1 ), (15-crown-5)NaTCNQ ( 2 ), (15-crown-5)Li(TCNQ) 2 .H 2 O ( 3 .H 2 O) and (15-crown-5)Na(TCNQ) 2 .H 2 O ( 4 .H 2 O) has been explored by single crystal X-ray diffraction, Infrared (IR), Raman and Electron Paramagnetic Resonance (EPR) measurements. (hud.ac.uk)
  • The resulting cations often form salts that are soluble in nonpolar solvents, and for this reason crown ethers are useful in phase transfer catalysis. (wikipedia.org)
  • The denticity of the polyether influences the affinity of the crown ether for various cations. (wikipedia.org)
  • The smallest crown ether still capable of binding cations is 8-crown-4, with the largest experimentally confirmed crown ether being 81-crown-27. (wikipedia.org)
  • In 1967, Charles Pedersen, who was a chemist working at DuPont, discovered a simple method of synthesizing a crown ether when he was trying to prepare a complexing agent for divalent cations. (wikipedia.org)
  • Citing earlier work on the dissolution of potassium in 16-crown-4, he realized that the cyclic polyethers represented a new class of complexing agents that were capable of binding alkali metal cations. (wikipedia.org)
  • Due to the chelate effect and macrocyclic effect, crown ethers exhibit stronger affinities for diverse cations than their divided or acyclic analogs. (wikipedia.org)
  • Affinities of a given crown ether towards the cations of lithium, sodium, and potassium can change by multiple magnitudes, which is attributed to the high differences in their charge density. (wikipedia.org)
  • Some modifications of dye ionophores by crown ethers exhibit extinction coefficients that are dependent on the chain lengths of chained cations. (wikipedia.org)
  • The crown-ether side groups selectively bind alkali-metal cations and when combined with TCNE or TTF dopants, provide a large phase-space for optimising thermoelectric properties. (rsc.org)
  • Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. (mdpi.com)
  • The structure determination of [Rb(15-crown-5) 2 ][TcNCl 4 (OH 2 )] is also described and shows a lattice containing 2:1 'sandwich'-type crown ether/alkali-metal cations and isolated anions in the disordered lattice. (royalsocietypublishing.org)
  • In the particular case of crown = 12-crown-4, both [ScCl2 (crown)](+) and [Sc (crown)(2)](3+) cations are produced. (warwick.ac.uk)
  • Jeong, KS & Kim, JH 1996, ' New crown ethers containing Kemp's triacid and their binding properties with alkali metal cations ', Bulletin of the Korean Chemical Society , vol. 17, no. 6, pp. 564-567. (elsevier.com)
  • Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. (elsevier.com)
  • Besides, a good correlation between ΔT CP and log K 1 ' was observed (Fig. 3) and it was indicated that ΔT CP was able to be an index of complexing abilities for these monoaza crown compounds with metal cations in water. (ncku.edu.tw)
  • The presence of a small cation and ionophore leads to subtle changes in behaviour compared with their larger alkali metal analogues and in the hydrated salts water bridges form links between the crown-encapsulated cations and neighbouring TCNQ stacks. (hud.ac.uk)
  • Lariate crowns The presence of the amine allows the formation of Lariat crown ethers, which feature sidearms that augment complexation of cation. (wikipedia.org)
  • The complexation enhanced quenched fluorescence spectra, (CEQFS) exhibited the ion complexation role of the macrocyclic ethers and equilibrium constant, K-e of 1:1 stoichiometry were estimated. (itu.edu.tr)
  • Sodium ion complexation by ionizable crown ethers in methanol-water solvents. (elsevier.com)
  • The kinetics of complexation of the crown carboxylate from 1 with Na + in 99% (w/w) methanol-water were examined with the electric field-jump technique. (elsevier.com)
  • Reaction of dibenzocrown ether carboxylic acids with formaldehyde in formic acid produces condensation polymers which possess both ion-exchange and cyclic polyether binding sites for metal ion complexation. (elsevier.com)
  • The conductometric study of ligand structure influence on the Pb(II) complexation with crown ethers in different solvents has been investigated. (stedj-univerzitetpim.com)
  • Macrocyclic ligand 18-crown-6 showed more suitable for complexation of Pb(II) ions compared to dibenzo-18-crown-6. (stedj-univerzitetpim.com)
  • We prepared optically active monoaza-18-crown-6 ethers, attached different fluorofor signalling units (BODIPY, acridinon, N-methylacridinon) to them, and using photophysical methods we thoroughly studied their complexation with the enantiomers of different chiral compounds, and several metal ions, respectively. (mtak.hu)
  • Stable donor-acceptor conjugates accommodating multifullerene entities have been obtained by the crown ether-ammonium cation inclusion complexation. (wichita.edu)
  • The high affinity of 18-crown-6 for potassium ions contributes to its toxicity. (wikipedia.org)
  • Hereby, the cation selectivity for alkali metal ions is mainly dependent on the size and charge density of the ion and the cavity size of the crown ether. (wikipedia.org)
  • This sheet of graphene contains an array of crown ethers that can strongly bind select guest ions or molecules. (newswise.com)
  • These crown-shaped rings are important as the initial prototype in host-guest chemistry, a field in which "guest" ions and molecules can be captured within the cavity of a "host" molecule. (newswise.com)
  • Molecular recognitionThe size and shape of the cavity formed within a crown ether molecule confers selectivity for complementary ions and small molecules that fit it, like a lock and key. (newswise.com)
  • Crown ethers come in different sizes, so they can accommodate ions of different diameters. (newswise.com)
  • It is a crown ether that binds to sodium ions and is commonly used to isolate salts of oxonium ions. (spectrumchemical.com)
  • In this study, we prepared electrospun polyacrylonitrile (PAN) nanofibers functionalized with dibenzo-18-crown-6 (DB18C6) crown ether and showed the potential of these fibers for the selective recovery of K + from other both mono- and divalent ions in aqueous solutions. (rsc.org)
  • Adsorption of Ba 2+ ions onto crown ether-modified nanofiber was examined by XPS and the results confirmed the adsorption of the ion. (rsc.org)
  • Electrospinning is thus shown to be a very versatile tool to prepare crown ether functional polymer adsorbents for the selective recovery of ions. (rsc.org)
  • In chloroform solutions also containing a crown ether (CE), water molecules strongly associate with the IL ions, and there is rapid proton exchange between these bound water molecules and hydronium associated with the CE. (osti.gov)
  • A brief review is given on the use of crown ethers in solubilizing salts of alkali and alkaline earth ions in organic polar or apolar solvents. (springer.com)
  • R., Rest A. J. Use of alkali- and alkaline-earth-metal ions in the template synthesis of 12-crown 4,15-crown-5. (ximicat.com)
  • Fingerprint Dive into the research topics of 'Cation Transport Through Liquid Membranes Mediated by Photoreactive Crown Ethers. (elsevier.com)
  • Crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. (wikipedia.org)
  • Crown ethers are not the only macrocyclic ligands that have affinity for the potassium cation. (wikipedia.org)
  • Mixed ether-amine ligands Another large class of macrocyclic ligands feature both ether and amines. (wikipedia.org)
  • Facile synthesis of novel styryl ligands containing a 15-crown-5 ether moiety / O. A. Fedorova, E. N. Andryukhina, M. M. Mashura, S. P. Gromov // ARKIVOC . (msu.ru)
  • eng] Herein is reported the efficient preparation of a set of enantiopure bisphosphine ligands, whose backbone incorporates an array of diverse crown ethers as distal regulation sites via well-defined supramolecular interactions to tune the catalytic properties of the bisphosphine groups. (uib.es)
  • The overlapped nature of the multimetal stripping measurements was resolved by employing the two-sensor array CB-15-crown-5-GEC and CB-18-crown-6-GEC, since the metal complex selectivity exhibited by the considered ligands could add some discrimination power. (uab.cat)
  • Crown Compounds: Toward Future Applications. (newworldencyclopedia.org)
  • Ethers are a class of organic compounds that contain an ether group -an oxygen atom connected to two alkyl or aryl groups. (wikipedia.org)
  • As for other organic compounds, very common ethers acquired names before rules for nomenclature were formalized. (wikipedia.org)
  • Polyethers are compounds with more than one ether group. (wikipedia.org)
  • On the other hand, complexing stability constants (log K 1 ') for these monoaza crown compounds with Na + and K + in methanol and in water/methanol (10: 90 v/v) mixture at 25°C were measured by Frensdorff's method. (ncku.edu.tw)
  • He proceeded to report systematic studies of the synthesis and binding properties of crown ethers in a seminal series of papers. (wikipedia.org)
  • The fields of organic synthesis, phase transfer catalysts, and other emerging disciplines benefited from the discovery of crown ethers. (wikipedia.org)
  • The synthesis of aza crown ethers are subject to the challenges associated with the preparation of macrocycles. (wikipedia.org)
  • Bis(2-bromoethyl) ether is used dfor synthesis of heterocyclic and crown ether. (alfa.com)
  • Functionalized Derivatives of Benzo-Crown Ethers. (hindawi.com)
  • The excited state and redox properties of three crown-ether derivatives of squaraines have been studied. (ias.ac.in)
  • We prepared chiral stationary phases based on pyridino- and acridino-18-crown-6 ethers starting from commercially available and relatively cheap materials, and using them we resolved racemic protonated primary amines, amino acids and their derivatives efficiently by HPLC. (mtak.hu)
  • The reason for crown ethers being more stable than their equally long open chain derivatives is the difference in Gibbs Free energy. (stackexchange.com)
  • Studies on Surface Active Derivatives from Glycidyl and Glyceryl-Ethers. (nii.ac.jp)
  • The crystal obtained from the stacking of these sheets is assembled into channel frameworks, approximately 2 nm wide, that clathrate two cationic K + -crown ether derivatives organised into one-dimensional (1D) double-columnar arrays. (elsevier.com)
  • In this study, we have shown that all five cationic guest-included crystals form nanochannel structures that clathrate the 1-D double-columnar arrays of one of the four types of K + -crown ether derivatives, one of which induces a polymorph. (elsevier.com)
  • The first number in a crown ether's name refers to the number of atoms in the cycle, and the second number refers to the number of those atoms that are oxygen. (wikipedia.org)
  • Crown ethers have been shown to coordinate to Lewis acids through electrostatic, σ-hole (see halogen bond) interactions, between the Lewis basic oxygen atoms of the crown ether and the electrophilic Lewis acid center. (wikipedia.org)
  • Hydrogen-bonds are formed between the three hydrogen atoms of protonated amines and three oxygen atoms of 18-crown-6. (wikipedia.org)
  • Newswise - Ethers-simple organic molecules in which an oxygen atom bridges two carbon atoms-are the chemical building blocks of commonplace products including many solvents, propellants, cosmetics and pharmaceuticals. (newswise.com)
  • Incorporating crown ethers into graphene, which is a stiff sheet due to the honeycomb arrangement of its carbon atoms, forces the ether rings to lie flat. (newswise.com)
  • Moreover, constraining the crowns in two dimensions forces all their oxygen dipoles to point inward, toward the centers of cavities, optimizing the electrostatic potential for binding atoms. (newswise.com)
  • An exact definition of the subject-matter to be patented was required because substituents of groups or, for example, alkyls having a different number of C atoms would dramatically influence the properties of the crown ethers. (epo.org)
  • However, bonding has to be mainly electrostatic as the interactions of the bismuth 6s lone pair with the 2p orbitals of the oxygen atoms of the crown ether are clearly antibonding. (mdpi.com)
  • We prepared enantiopure proton-ionizable crown ethers containing an dialkylhidrogenphosphate or a diarylphosphinic acid unit, and we thoroughly studied the enantioselective complex formation of the latter with protonated primary aralkyl amines. (mtak.hu)
  • Pedersen shared the 1987 Nobel Prize in Chemistry for the discovery of the synthetic routes to, and binding properties of, crown ethers. (wikipedia.org)
  • Because the molecular recognition properties of crown ethers mimic the selective molecular transport properties of biological proteins, a new understanding of pharmaceutical function has become possible with exciting medicinal applications. (newswise.com)
  • In chemistry, an aza-crown ether is an aza analogue of a crown ether (cyclic polyether). (wikipedia.org)
  • Polyether generally refers to polymers which contain the ether functional group in their main chain. (wikipedia.org)
  • Use of crown ethers can also be made in testing e.g. lithium salts for potassium by extraction as LKpicrate, L being 18-crown-6. (springer.com)
  • Analytical equations were derived for the extraction of univalent metal salts (MA) by crown ethers (L) into polar diluents. (ccsenet.org)
  • Spectra for other crown ether salts are consistent with isolated [TcNCL 4 ] - or [TcNCL 4 (OH 2 )] - anions, with dipolar broadening effects apparent. (royalsocietypublishing.org)
  • FTIR spectra of tricarbonyl(eta(6)-benzo-15-crown-5)chromium(0) (1) in the presence of lithium, sodium and potassium perchlorate salts in methanol show different responses in the Cr-CO vibrational region of the spectrum. (uea.ac.uk)
  • Tertiary amines In many aza-crown ethers some or all of the amines are tertiary. (wikipedia.org)
  • Cryptands, three-dimensional aza crowns, feature tertiary amines. (wikipedia.org)
  • Lehn also describes a good deal of work with two specific structural motifs: macrocyclic and macropolycyclic ethers and amines on the one hand and metal helicates on the other. (foresight.org)
  • Now a team led by the Department of Energy's Oak Ridge National Laboratory has discovered a way to dramatically increase the selectivity and binding strength of crown ethers. (newswise.com)
  • Because of the flexibility, a crown ether molecule can adjust the size and shape of its cavity to accommodate a range of sizes and shapes of guests, limiting the crown ether's selectivity. (newswise.com)
  • For a series of structurally related, lipophilic dibenzocrown ether carboxylic acids, the efficiency and selectivity of competitive alkali metal cation extraction for aqueous solution into chloroform is found to be strongly influenced by the crown ether ring size and the lipophilic group attachment site. (elsevier.com)
  • Cation selectivity in the sorption and stripping steps is controlled by the structure of the crown ether monomer unit. (elsevier.com)
  • We synthetized enantiopure crown ethers containing an acridine unit, and showed by potentiometric measurements that one of them had a reasonable selectivity for the enatiomers of protonated 1-phenylethylamine, and another one complexed silver ion with very high selectivity. (mtak.hu)
  • The novel design feature of these molecules is the presence of either ( 1 ) crown-ether or ( 2 ) diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. (rsc.org)
  • abstract = "Functionalized binaphthyl salophen crown ethers 2 and 3 containing a Lewis‐acidic uranyl cation were prepared by the Ba2+‐templated cyclization of dialdehydes 15 and 22, for which two convenient synthetic routes were developed, with diamines 23 and 24. (utwente.nl)
  • abstract = "N-[ω-(Long-chain alkyl)oligo(oxyethylene)] monoaza crown ethers (Cx. (ncku.edu.tw)
  • abstract = "The Langmuir and Langmuir-Blodgett films of a benzo-18-crown-6-methanofullerene (1) were studied by spectrophotometry and Br{\"e}wster angle microscopy. (elsevier.com)
  • George, M. V. (1996) Photochemistry of squaraine dyes: excited triplet state and redox properties of crown ether squaraines The Journal of Physical Chemistry, 100 (6). (ias.ac.in)
  • The effects of crown ethers (12-crown-4, 15-erown-5, and lS-crown-6) and anions (C1O 4 ~, NO 3 ″, CI″, Br″, and I″) on the redox behaviors of europium(III/II) were investigated by cyclic voltammetry in an aqueous solution. (elsevier.com)
  • The complexations of europium (II) with crown ethers were discussed by means of the shifts of redox potential. (elsevier.com)
  • 78. Redox-switched crown ethers. (ximicat.com)
  • For example, ethyl methyl ether (CH 3 OC 2 H 5 ), diphenylether (C 6 H 5 OC 6 H 5 ). (wikipedia.org)
  • The design concept involves ditopic interactions 1) between a positively charged and coordinatively unsaturated Gd(3+) chelate and the carboxylate group of the neurotransmitters and 2) between an azacrown ether appended to the chelate and the amino group of the neurotransmitters. (cnrs-orleans.fr)
  • Chiral monoaza-15-crown-5 lariat ethers synthesized from D-glucose, D-galactose, and D-mannitol have been applied as phase-transfer catalysts in the enantioselective epoxidation of chalcones with tert-butylhydroperoxide. (elsevier.com)
  • Among the catalysts, the crown ether annellated to methyl-4,6-O-benzylidene-α-D-glucopyranoside, with 3-hydroxypropyl side arm at the nitrogen atom 1f proved to be the most effective (92% ee). (elsevier.com)
  • Y. Takeda, K. Hashimorto, D. Yoshiyama, and S. Katsuta, "Extraction of alkali metal (Li-Cs) picrates with benzo-15-crown-5 into various organic solvents. (hindawi.com)
  • Y. Takeda, A. Kawarabayashi, K. Takahashi, and Y. Kudo, "Extraction of alkali metal picrate with benzo-18-crown-6 into various organic solvents. (hindawi.com)
  • Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin . (wikipedia.org)
  • Consequently, we propose that crown ethers can be used to modulate a wide variety of protein surface behaviors, such as oligomerization, domain-domain interactions, stabilization in organic solvents, and crystallization. (elsevier.com)
  • Organic hosts, such as crown ethers, cyclodextrins (CDs), calixarenes (CXs), and spherands, or polymeric additives, such as poly(ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were used as the micropore-forming templates. (google.ca)
  • For example, 18-crown-6 has high affinity for potassium cation, 15-crown-5 for sodium cation, and 12-crown-4 for lithium cation. (wikipedia.org)
  • Y. Takeda and C. Takagi, "Solvent extraction of sodium picrate with 15-crown-5. (hindawi.com)
  • The direct fluorination of ethers in the presence of hydrogen fluoride (HF) scavengers such as sodium fluoride and potassium fluoride is disclosed. (google.com)
  • Link them together in large molecular rings and they become scientific royalty-crown ether molecules, whose development led in large part to the 1987 Nobel Prize in chemistry. (newswise.com)
  • Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. (mdpi.com)
  • Crown ethers are small, cyclic polyethers that have found wide-spread use in phase-transfer catalysis and, to a certain degree, in protein chemistry. (elsevier.com)
  • These consisted of molecules of carbon and oxygen arranged in a "crown" shape. (telegraph.co.uk)
  • The ESR spectra of [Cs(18-crown-6)] [TcNCl 4 ] over the temperature range 130-290 K indicate the presence of exchange interactions along the linear --- Tc≡N--- Tc≡N--- chains. (royalsocietypublishing.org)
  • Pedersen particularly popularized the dibenzo crown ethers. (wikipedia.org)
  • The structure consists of an 'infinite sandwich' Cs + cation/crown ether configuration and polymeric [TcNCL 4 ] - anions, with Tc≡N distances of 1.561(36) Å, and anti-parallel chains of ---Tc≡N---Tc≡N ---with Tc···Tc separations of 4.275(4) Å. (royalsocietypublishing.org)
  • The presence of Tc≡N infrared stretching frequencies at ca . 1074 cm -1 indicates the absence of strong electron donors coordinated to Tc in the sixth position (i. e. isolated anions), whereas the polymeric chain structure of [Cs(18-crown-6)] [TcNCL 4 ] is characterized by a Tc≡N stretching frequency of 1041 cm -1 . (royalsocietypublishing.org)
  • Photoreactivities and cation transporting properties of monomeric, dimeric, and polymeric crown ethers which contain cinnamoyl residues were investigated. (elsevier.com)
  • The dimeric and polymeric crown ethers after irradiation in the presence of KCl showed a significant enhancement in the transport rates for Rb + cation. (elsevier.com)
  • For example, the strength with which a crown ether binds a potassium atom is three times greater in its constrained, rigid state on graphene than in an unconstrained structure. (newswise.com)
  • The chelates differ in the nature and length of the linker connecting the cyclen-type macrocycle that binds the Ln(3+) ion and the crown ether. (cnrs-orleans.fr)
  • Cyclam is a tetraaza crown ether with alternating (CH2)2 and (CH2)3 linkers between amine centers. (wikipedia.org)
  • 2.2.2-Cryptand is an aza-crown of the mixed ether-amine variety. (wikipedia.org)
  • Aza-crowns" consist of crown ethers wherein an ether oxygen has been replaced by an amine group. (newworldencyclopedia.org)
  • Mixed amine-ether crowns are also known. (newworldencyclopedia.org)
  • Fluorescence studies on active and Tris-treated samples showed that K- crown does not prevent artificial donors from transferring electrons to PSII but like DCMU inhibits on the acceptor side after QA, the primary quinone acceptor. (bvsalud.org)
  • Vibrational Sum Frequency Spectroscopy (VSFS) was employed to study adsorbing films of 4-Nitro Benzo-15-Crown-5 (NB15C5) and Benzo-15-Crown-5 (B15C5) at the aqueous solution-air interface. (diva-portal.org)
  • Then, NaMnO4 was extracted at 25 ?C by benzo-15-crown-5 and -18-crown-6 ethers (B15C5 and B18C6) from a water (w)-phase into a 1,2-dichloroethane (DCE)-one. (ccsenet.org)
  • The reaction of bismuth triiodide with iodine and benzo-15-crown-5 in ethanol/dichloromethane yielded red single crystals of (b15c5)BiI 3 (I 2 ) (monoclinic, P2 1 /c (no. 14), a = 1376.9(1), b = 1172.7(1), c = 1700.2(2) pm, b = 115.197(6), V = 2484.1(4)·10 6 pm 3 , Z = 4). (mdpi.com)
  • The transfer of strontium ion from acidic nitrate media into a series of 1-alkyl-3-methylimidazolium-based room-temperature ionic liquids containing dicyclohexano-18-crown-6 is shown to proceed via cation-exchange, in contrast to conventional solvents such as alkan-1-ols, in which extraction of a strontium nitrato-crown ether complex is observed. (osti.gov)
  • The determination of ion-pair formation constant of crown ether-metal salt 1 : 1 : 1 complex in water," Bulletin of the Chemical Society of Japan , vol. 67, no. 1, pp. 56-60, 1994. (hindawi.com)
  • If the ether is part of a more complex molecule, it is described as an alkoxy substituent, so -OCH 3 would be considered a " methoxy -" group. (wikipedia.org)
  • The effects of surfactant structure (Triton X-100 and Triton X-45) on the conductivity of the Pb(II) complex with 18-crown-6 and dibenzo-18-crown-6 ether have been investigated. (stedj-univerzitetpim.com)
  • As europium(II) forms a stable 1 : 1 complex with 18-crown-6, the stabilization of europium(lI) is remarkable. (elsevier.com)
  • The small anion such as CI″ strongly interacts with europium (II) complex with 18-crown-6 to weaken the stabilization effect of europium(II) by crown ether. (elsevier.com)
  • K- crown does not disrupt binding of the extrinsic proteins associated with O2 evolution nor complex with bound Ca2+ or Cl- cofactors, but rather it directly inhibits electron transfer after the tetrameric Mn cluster. (bvsalud.org)
  • In the presence of Na + , such CS process was completely suppressed by the formation of the Na + -inclusion complex H 2 P-(2T(crown-Na + )2T)-C 60 . (elsevier.com)
  • The crown ethers are examples of small polyethers. (wikipedia.org)
  • This chapter provides the diffusion coefficient of dicyclohexano-24-crown-8-ether in ethanol at different concentrations measured using Taylor dispersion technique. (springer.com)
  • Winkelmann J. (2018) Diffusion coefficient of dicyclohexano-24-crown-8-ether in ethanol. (springer.com)
  • From the measurements of cloud points, it was found that the introduction of oxyethylene units between monoaza crown ring and alkyl moiety increased the hydrophilicities compared with those in the N-alkyl monoaza crown ethers (C x . (ncku.edu.tw)
  • From the measurements of cloud points, it was found that the introduction of oxyethylene units between monoaza crown ring and alkyl moiety increased the hydrophilicities compared with those in the N-alkyl monoaza crown ethers (Cx. (ncku.edu.tw)
  • The invention was characterised by a particular class of crown ethers which were useful ionophores in ion-selective compositions. (epo.org)
  • Methyl phenyl ether is anisole , because it was originally found in aniseed . (wikipedia.org)
  • Similar constants have also been measured for 2,6-dimethylenebenzoic acid-18-crown-5 (5) and its methyl ester analogue 6. (elsevier.com)
  • Ethers can again be classified into two varieties: if the alkyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. (wikipedia.org)
  • To achieve this, phthalocyanine is functionalized to possess four 18-crown-6 moieties on the macrocycle periphery, whereas fullerene is functionalized to possess an alkyl ammonium cation of short and long chain lengths. (wichita.edu)
  • N-[ω-(Long-chain alkyl)oligo(oxyethylene)] monoaza crown ethers (C x .(m + l)-N(15, 18), x: 8 and 12, m: 0~2) were prepared from alkyl oligo(oxyethylene) chlorides and N-unsubs-tituted monoaza crown ethers (Scheme 1). (ncku.edu.tw)
  • The most common crown ethers are cyclic oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e. (wikipedia.org)
  • The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy (-CH 2 CH 2 O-). Important members of this series are the tetramer (n = 4, or four ethyleneoxy units), the pentamer (n = 5), and the hexamer (n = 6). (newworldencyclopedia.org)
  • 15-Crown 5-Ether is the cyclic pentamer of ethylene oxide. (spectrumchemical.com)
  • Well studied aza crowns include triazacyclononane (n = 3), cyclen (n = 4), and hexaaza-18-crown-6 (n = 6). (wikipedia.org)
  • In the IUPAC nomenclature system, ethers are named using the general formula "alkoxyalkane" , for example CH 3 -CH 2 -O-CH 3 is methoxyethane . (wikipedia.org)
  • The bonding of oxygen in ethers, alcohols, and water is similar. (wikipedia.org)
  • These differences depend upon the relative sizes of europium(1) ion to the internal cavities of crown ethers. (elsevier.com)
  • This capability allows chemists to organize a collection of separately weak bonding interactions, such as the electrostatic bond between an ether oxygen atom and a metal ion, to achieve strong, selective binding. (newswise.com)
  • Because crown ethers are selective, they are now used for metal separations and have already helped clean up millions of gallons of legacy nuclear waste. (newswise.com)
  • Structurally suitable ammonium phosphates, such as the Cterminal domain of RNA polymerase II or the protein kinase G target sequence, bind to the synthetic receptors by an additional intramolecular interaction between the ammonium ion and the aza crown ether. (uni-regensburg.de)
  • The binding of the ammonium ion to the aza crown ether increases the emission intensity of the fluorophore. (uni-regensburg.de)
  • Self-assembled phthalocyanine-multifullerene donor-acceptor conjugates have been formed by crown ether-ammonium cation dipole-ion binding strategy to probe the photochemical charge separation. (wichita.edu)
  • In a crown ether, the electric dipole moments of the C-O-C ether groups when organized around a captured guest metal ion provide a large electrostatic potential for binding the ion in the ring cavity. (newswise.com)
  • Lipophilic crown ethers with pendent proton-ionizable groups are novel complexing agents for use in metal ion separations by solvent extraction. (elsevier.com)
  • For 5 in 99% (w/w) methanol-water, Na + is apparently competing with an intramolecular hydrogen bond for the cavity space of the crown ether. (elsevier.com)
  • Brëwster angle microscopy shows different aggregation properties of the benzo-18-crown-6-methanofullerene (1) Langmuir monolayers on pure water compared to those on a 1 M KCl subphase. (elsevier.com)
  • This work describes the immobilization of 4-carboxybenzo-18-crown-6 (CB-18-crown-6) and 4-carboxybenzo-15-crown-5 (CB-15-crown-5) assisted by lysine on aryl diazonium salt monolayers anchored to the surface of graphite-epoxy composite electrodes (GEC), and their use for the simultaneous determination of Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry (DPASV). (uab.cat)
  • The ends of the crown ether are also pulled together, this cost of entropy however, has been paid in an earlier reaction when making the crown ether, and therefore has no influence here. (stackexchange.com)
  • Oxygen -evolution studies demonstrated that the ether works by inactivating the centres and not by interfering with antenna function or energy transfer to the reaction centre. (bvsalud.org)
  • With crown phosphonic acid monoalkyl ester 4, Na + is more selectively complexed relative to K + than with crown carboxylic acid 1. (elsevier.com)
  • The type of monosaccharide on the crown ether and the substituents at the nitrogen atom of the crown-ring has a major influence on both the chemical yield and enantioselectivity. (elsevier.com)
  • Ion-exchange as a mode of cation transfer into room-temperature ionic liquids containing crown ethers : implications for the "greenness" of ionic liquids as diluents in liquid-liquid extraction. (osti.gov)
  • Y. Takeda, A. Kawarabayashi, K. Endō, T. Yahata, Y. Kudo, and S. Katsuta, "Solvent extraction of alkali metal (Li-Cs) picrates with 18-crown-6 into various diluents. (hindawi.com)
  • Takeda Y. The Solvent Extraction of Uni- and Bivalent Picrates by Dibenzo-24-crown-8. (springer.com)
  • Extraction of Na + with the external 15-crown-ether-5 recovered the photoinduced CS process. (elsevier.com)