- Complexation of Diaza Crown Compounds with Some Alkali Metal Ions in Acetonitrile and in Methanol at 25 deg C
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Conductometric measurements of lithium and potassium picrate in pure methanol, in pure acetonitrile, and in the presence of 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane and N-methyl-N'-dodecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane macrocyclic ligands have been carried out at 25 deg C.The analysis of the results obtained with the different systems shows that the interaction forces, correlated with the molecular details of ions, solvents, and ligands, are, in most cases, superimposed on the ion-dipole forces acting between cations and macrocyclic cavities to such an extent as to prevent the cation macrocyclic ligand complexation.The effect of side chains attached to the main diazo crown ether ring on the complexation process is also discussed.
- D'Aprano, Alessandro,Sesta, Bianca
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- Uncommon complex stoicheiometry in solvent extraction: Solution-phase dicationic complex formation of crown ethers
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A solvent extraction study with 18-crown-6, 24-crown-8, and their dibenzo-derivatives has revealed that the following ligand-cation combinations give dicationic complexes in the solution phase: 18-crown-6 with Li+; 24-crown-8 with Li+, Na+, K+; dibenzo-24-crown-8 with Na+, K+, Ag+, Sr2+. The facile formation of dicationic complexes in the solvent extraction is attributed to the effective charge-shielding co-ordination by the bulky, lipophilic picrate anions in the contact ion-pair complex extracted.
- Inoue, Yoshihisa,Liu, Yu,Amano, Fumie,Ouchi, Mikio,Tai, Akira,Hakushi, Tadao
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- Buckyball-Based Spherical Display of Crown Ethers for de Novo Custom Design of Ion Transport Selectivity
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Searching for membrane-active synthetic analogues that are structurally simple yet functionally comparable to natural channel proteins has been of central research interest in the past four decades, yet custom design of the ion transport selectivity still remains a grand challenge. Here we report on a suite of buckyball-based molecular balls (MBs), enabling transmembrane ion transport selectivity to be custom designable. The modularly tunable MBm-Cn (m = 4-7; n = 6-12) structures consist of a C60-fullerene core, flexible alkyl linkers Cn (i.e., C6 for n-C6H12 group), and peripherally aligned benzo-3m-crown-m ethers (i.e., m = 4 for benzo-12-crown-4) as ion-transporting units. Screening a matrix of 16 such MBs, combinatorially derived from four different crown units and four different Cn linkers, intriguingly revealed that their transport selectivity well resembles the intrinsic ion binding affinity of the respective benzo-crown units present, making custom design of the transport selectivity possible. Specifically, MB4s, containing benzo-12-crown-4 units, all are Li+-selective in transmembrane ion transport, with the most active MB4-C10 exhibiting an EC50(Li+) value of 0.13 μM (corresponding to 0.13 mol % of the lipid present) while excluding all other monovalent alkali-metal ions. Likewise, the most Na+ selective MB5-C8 and K+ selective MB6-C8 demonstrate high Na+/K+ and K+/Na+ selectivity values of 13.7 and 7.8, respectively. For selectivity to Rb+ and Cs+ ions, the most active MB7-C8 displays exceptionally high transport efficiencies, with an EC50(Rb+) value of 105 nM (0.11 mol %) and an EC50(Cs+) value of 77 nM (0.079 mol %).
- Li, Ning,Chen, Feng,Shen, Jie,Zhang, Hao,Wang, Tianxiang,Ye, Ruijuan,Li, Tianhu,Loh, Teck Peng,Yang, Yi Yan,Zeng, Huaqiang
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- Synthesis, binding properties and theoretical studies of p-tert-butylhexahomotrioxacalix[3]arene tri(adamantyl)ketone with alkali, alkaline earth, transition, heavy metal and lanthanide cations
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p-tert-Butylhexahomotrioxacalix[3]arene tri(adamantyl)ketone (1b) was synthesized for the first time. Compound 1b was obtained in a cone conformation in solution at room temperature, as established by NMR spectroscopy (1H and 13C). The binding properties of ligand 1b for alkali, alkaline earth, transition, heavy metal and lanthanide cations have been assessed by phase transfer and proton NMR titration experiments. Molecular mechanics and ab initio techniques were also employed to complement the NMR data. The results are compared to those obtained with other closely related homooxacalixarene derivatives. Although triketone 1b is a weak extractant, it shows a strong peak selectivity for Na+ and also some preference for Ag+. Proton NMR titrations indicate the formation of 1:1 complexes between 1b and the cations studied, and also that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Although the molecular mechanics results show little correlation with the NMR data, a good agreement was obtained with the ab initio models.
- Marcos, Paula M.,Ascenso, José R.,Segurado, Manuel A.P.,Bernardino, Raul J.,Cragg, Peter J.
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experimental part
p. 496 - 503
(2009/04/07)
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- A study of C-F···M+ interaction: Alkali metal complexes of the fluorine-containing cage compound
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The C-F···M+ interaction was investigated by employing a cage compound 1 that has four fluorobenzene units. The NMR (1H, 13C, and 19F) spectra and X-ray crystallographic analyses of 1 and its metal complexes showed clear evidence of the interaction. Short C-F···M+ distances (CF···K+, 2.755 and 2.727 A; C-F···Cs+ 2.944 and 2.954 A) were observed in the crystalline state of K+ ? 1 and Cs+ ? 1. Furthermore, the C-F bond lengths were elongated by the interaction with the metal cations. By calculating Brown's bond valence, it is shown that the contribution of the C-F unit to cation binding is comparable or greater than the ether oxygen in the crystalline state. Representative spectroscopic changes implying the C-F···M+ interaction were observed in the NMR (1H, 13C, and 19F) spectra. In particular, 133Cs-19F spin coupling (J = 54.9 Hz) was observed in the Cs+ complex.
- Takemura,Kon,Kotoku,Nakashima,Otsuka,Yasutake,Shinmyozu,Inazu
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p. 2778 - 2783
(2007/10/03)
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- Design and synthesis of a new class of nonmacrocyclic alkali metal host compounds
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A new class of nonmacrocyclic metal ion hosts has been examined that features a polyspirocyclic framework that offers a 1,3,5-triaxial presentation of ligating centers. These compounds are easily synthesized and exploit stereoelectronic influences to preorganize the metal ion binding site. While compounds bearing oxygen substituents (X = OH, OMe) failed to show appreciable binding of alkali metals, the aminated host (X = NHBn) exhibitied strong binding with association constants (Ka) greater than 107-108 as measured by picrate extraction analysis.
- McGarvey, Glenn J.,Stepanian, Marshall W.,Bressette, Andrew R.,Sabat, Michal
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p. 3453 - 3456
(2007/10/03)
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- New supramolecular hosts: Synthesis and cation binding studies of novel Troger's base-crown ether composites
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A simple and straightforward synthesis of a novel class of supramolecular hosts containing the Troger's base moiety is reported. The cation binding properties of these macrocycles were investigated using Cram's picrate extraction method.
- Manjula, Alla,Nagarajan, Madhavarao
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p. 11859 - 11868
(2007/10/03)
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- Host - Guest Complexation. 36. Spherand and Lithium and Sodium Ion Complexation Rates and Equilibria
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Thermodynamiic and kinetic parameters for complexation by three spherands of lithium and sodium picrates in CDCl3 are reported.The host are composed of the following units (Chart I) bonded to one another in 18-membered-ring systems: 2,6-disubstituted 4-methylanisyl (A); 2,6-disubstituted 4-methylanisyl deuterated in the methoxy group (Ad); 2,6-disubstituted 4-methylphenol (Ah); 2,6-disubstituted 4-methyl-1-allyloxybenzene (Aa); 2,6-disubstituted 4-methylphenyloxy (B); 1,3-phenylene (P); 1,2-cyclohexano(Cy); ethylene (E); methylene (M); oxygen (O); and nitrogen (N).The orders of the letters in the line formulas indicate the orders of attachment of the units in the cyclic or bicyclic hosts.In the polycyclic hosts, transannular B units serve as the bridgeheads linked through their oxygens to M3 or EOE units to transannular B units, at their 2-positions to A units, and at their 6-positions to either other B units (spherands) or to M units (hemispherands).In the cryptands, the nitrogen atoms act as bridgeheads.Chart II identifies the letters with the structures of the units and the structures and compound numbers with the line formulas.The hemispherands listed were useful in proving low, known concentrations of guests while the chorand listed was used for dissolving sodium and lithium picrates in CDCl3.The Ka and -ΔGo values for 2 (2) binding sodium picrate were determined at 25 deg C in CDCl3 saturated with D2O by the direct picrate extraction method.The Ka values for A(AA)2A (1) and 2 (3) binding sodium picrate and for all three spherands binding lithium picrate could not be measured directly.Accordingly, values were obtained kinetically.Decomplexation rates for Ad(AdAd)2Ad (1d), 2 (2d), and 2 (3d) were prepared.With 1H NMR techniques at three temperatures in CDCl3 saturated at 25 deg C with D2O, the rate constants were determined for Li(1+) or Na(1+) transfering from nondeuterated to deuterated hosts.Because the reaction rate was comparable to rates of demethylation of the complex at high temperatures, only a maximum value could be placed on the rate constant for .Values for δH and ΔS for decomplexation were calculated, and decomplexation rate constants were extrapolated to 25 deg C.Rate constants for A(AA)2A (1), 2 (2) and 2 (3) complexing sodium picrate were determined at 25 deg C by following the 1H NMR changes as guest was transferred from BB.NaPic (6.NaPic) to each of the three spherands.The complexation rate for complexing NaPic is much higher for 6 than for 1,2, or 3.The role of 6.NaPic was to provide a preequilibrium concentration of NaPic low enough to bring the complexation rate of the spherands onto the human time scale.The complexation rate constant of 1 with LiPic was determined by competition experiments between NaPic and LiPic, which were delivered in CDCl3 s
- Cram, Donald J.,Lein, George M.
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p. 3657 - 3668
(2007/10/02)
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- FORMATION OF PICRATES IN THE REACTIONS OF PICRYL HALIDES PicX (X = F, Cl, I) WITH ORGANOMETALLIC SALTS R3EM (E = Se, Ge AND M = Li, K, Cs), BORATES, AND CARBANIONS. POSSIBLE REACTION MECHANISMS
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The reaction of picryl halides PicX (X = F, Cl, I) with organometallic compounds Me3SnM (M= Li, K, Cs), Et3GeK, borates Me4NBR4 (R = Bu, CH2SiMe3, CH2GeMe3), and 9-fluorenylpotassium was investigated.It was shown that for picryl fluoride and picryl chloride the reaction leads to the corresponding picrate.In the case of picryl iodide 1,3,5-trinitrobenzene is formed in addition to the picrate.The formation of the picrate also accompanies the reaction of PicX (X = F, Cl, I) with potassioacetoacetic ester, the main product from which is picrylacetoacetic ester.Possiblemechanisms are considered for the reaction leading to the picrates.
- Artamkina, G. A.,Egorov, M. P.,Beletskaya, I. P.,Reutov, O. A.
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p. 1649 - 1659
(2007/10/02)
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- REACTION OF METHYL AND PHENYL PICRATES WITH NUCLEOPHILES
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The reactions of 2,4,6-trinitroanisole with various nucleophiles Me3SnM, Me3SiLi, BuLi, Me4NBBu4, PhMgI, CN-, lithium (potassium) succinimide, F-, Cl-, Br-, SCN-, NO2-, NO3-, HCO3-, PhSO2-,AcO-, S2- were investigated.It was found that the final products are the picrate and the corresponding methyl derivatives.The formation of intermediate ? complexes was detected in a series of the reactions (Me3SnLi, potassium succinimide, Bu4B-, CN-, NO2-, PhSO2-).Possible mechanisms for the reaction are examined.Reactions of 2,4,6-tricyanoanisole and phenyl picrate with certain nucleophiles were also investigated.
- Artamkina, G. A.,Egorov, M. P.,Beletskaya, I. P.,Reutov, O.A.
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- REACTIONS OF AROMATIC NITRO COMPOUNDS. LII. ALKALINE CLEAVAGE OF ? COMPLEXES OF 2,4,6-TRINITROANISOLE WITH ALKALI-METAL METHOXIDES IN THE PRESENCE OF NEUTRAL SALTS
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The kinetics of the alkaline cleavage of ? complexes of 2,4,6-trinitroanisole with lithium, sodium, and potassium methoxides in the presence of the chlorides of these metals were investigated.The nature and concentration of the salt have a significant effect on the reaction rate.The reason for such an effect lies both in the formation of ion pairs and triplets in the reaction system and in the salt effect.Disruption of the framework structure of water by the bulky cations also has a significant effect on the process rate.
- Golopolosova, T. V.,Gitis, S. S.,Glaz, A. I.,Kaminskii, A. Ya.,Savinova, L. N.
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p. 898 - 901
(2007/10/02)
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