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1.
The complexation reactions between Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions and benzo-15-crown-5, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and 1,10-diaza-18-crown-6 have been studied in dimethylsulphoxide solution at 25 degrees by means of a competitive spectrophotometric method using murexide as a metallochromic indicator. With the exception of Pb(II)(benzo-15-croqn-5)(2) the stoichiometry of the resulting complexes was found to be 1:1. The formation constants of the complexes were determined, and found to follow the Irving-Williams rule for the cations of the first transition series. It was found that the metal ion-18-crown interactions are strongly dependent on the nature of the substituents on the ring. 相似文献
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A glassy carbon electrode was modified with Nafion, carbon nanotubes and benzo-18-crown-6 to give an electrode for the selective determination of lead(II) via square wave anodic stripping voltammetry. The use of carbon nanotubes with their extraordinary electrical conductivity and strong adsorption ability warrants high sensitivity. Benzo-18-crown-6 is employed as a “molecular scavenger” because of its excellent selectivity for lead(II). The modified electrode shows enhanced sensitivity, reproducibility and selectivity for lead(II) even without applying an electrical potential during the accumulation time. It responds linearly to lead(II) in the 1 to 30 nM concentration range (with a correlation coefficient of 0.9992) after a 10-min accumulation time. The detection limit is 1 nM. The sensor exhibits excellent selectivity over other heavy metal ions such as Cd(II), Cu(II), Zn(II), and Hg(II). Figure
Bi-functional mixture of carbon nanotube and crown ether is established for square wave anodic stripping voltammetric analysis of lead(II). The glassy carbon electrode modified with Nafion, Carbon Nanotube, and Benzo-18-Crown-6 showed excellent selectivity and also low detection limit (1 nM). 相似文献
4.
The formation constants (K(ML)) in water of 1:1 complexes of benzo-18-crown-6 (B18C6) and 18-crown-6 (18C6) with Zn(2+) and Cd(2+), the sizes of which are much smaller than the ligand cavities, were determined at 25 degrees C by conductometry. Compared with Cd(2+), the crown ethers form more stable complexes with Zn(2+) although the size of Zn(2+) is less suited for the cavities. B18C6 forms a more stable complex with each metal ion than 18C6. Moreover, the extraction equilibria of these metal ions (M(2+)) with B18C6 (L) for the benzene/water system in the presence of picric acid (HA) were investigated at 25 degrees C. The association between L and HA in benzene was examined for evaluating the intrinsic extraction equilibria of M(2+) with B18C6. The extracted species were found to be MLA(2) and ML(2)A(2), and the overall extraction constants (K(ex,1) and K(ex,2), respectively) were obtained. The values of K(ex,1) for these metal ions are almost the same, but the K(ex,2) is larger for Zn(2+) than for Cd(2+). The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K(ML), the ion-pair extraction constant of ML(2+) with A(-), and the adduct formation constant of MLA(2) with L in benzene. 相似文献
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《Analytical letters》2012,45(10):821-827
Abstract New poly- and bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 moieties were synthesized as extracting reagents, and by a preliminary solvent extraction of alkali metal picrates the poly- and bis-(crown ether)s were found to extract the cations capable of forming sandwich-type 2:1 complexes more effectively than their monomeric analogs. 相似文献
7.
Synergistic solvent extraction of 14 lanthanides with mixtures of 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) and the
crown ethers (S), 18-crown-6, benzo-18-crown-6 or dibenzo-18-crown-6 from an aqueous chloride medium with the constant ionic
strength of 0.1 mol dm−3 was investigated using benzene as a diluent. The composition of the species extracted was determined as LnP3 · S. The addition
of a crown ether to the chelating extractant produced rather significant synergistic effects. On basis of experimental data,
values of equilibrium constants, synergistic coefficients, and separation factors were calculated. 相似文献
8.
P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》1998,228(1-2):43-46
The extraction of cesium, strontium and barium by a nitrobenzene solution of dicarbollylcobaltate in the presence of various crown ethers has been investigated and the influence of the substituent of crown to the extraction possibility has been observed. It has been found, that the addition of DB15C5, DB18C6 and DB21C7 (but not DB24C8 and DCH24C8) increases the distribution ratio of Cs by one order of magnitude. The fivemembered crowns are usually more efficient extractants for strontium than DCH18C6, which is widely used for strontium separation. The distribution ratio of strontium DSr decreases in the order 15-crown-5>benzo-15-crown-5>2-hydroxymethyl-15-crown-5>cyclohexyl-15-crown-5 >dibenzo-15-crown-5> nitrobenzo-15-crown-5. The selectivity α(Sr/Ca) decreases in the order 15C5>B15C5>DB15C5>2HM15C5>CH15C5. A selectivity factor α(Sr/Ca)≥1000 can be reached in the presence of 15C5 and B15C5. Six-membered and four-membered crowns extract strontium worse than most of the five-membered crowns. The selectivity factors α(Sr/Ca)≈100 have been reached for six-membered crowns and α(Sr/Ca)<1 has been found for 12C4. The extraction of barium by a nitrobenzene solution of dicarbollylcobaltate in the presence of 15C5 is even more efficient as the extraction of strontium. In that system DSr>104 and DBa>104 have been found for the extraction of Sr and Ba by a 0.01M nitrobenzene solution of dicarbollylcobaltate (cB=0.01 mol/l) from 0.1M HNO3. Maximal values of separation factor α(Ba/Sr) have been found in the system containing DB21C7. 相似文献
9.
Reactions of Potassium Iodomercurate(II) with Crown Ethers and Cryptands: Crystal Structures of Bis[di(benzo-15-crown-5)potassium]-, Di[(benzo-18-crown-6)potassium]-, Di[(cryptand 221)potassium]-, and Di[(cryptand 222)potassium] Hexaiododimercurate(II) The reactions of potassium iodomercurate(II) with the crown ethers benzo-15-crown-5, and benzo-18-crown-6, resp. as well as with the cryptands 221 and 222 were investigated. In all cases only the potassium ion was complexed. As anions only hexaiododimercurate(II) ions were formed but no higher oligomers. If the complexed potassium ion is not completely shielded by the ligand, further coordination by terminal iodine atoms of the mercurate anions takes place, leading to the formation of dimers or chains. 相似文献
10.
M. Atanassova 《Russian Journal of Inorganic Chemistry》2007,52(8):1304-1311
The synergistic solvent extraction of 13 lanthanides with mixtures of 8-hydroxyquinoline (HQ) and the crown ethers (S) 18-crown-6
(18C6) or benzo-18-crown-6 (B18C6) in 1,2-dichloroethane has been studied. The composition of the extracted species has been
determined as LnQ3 · S. The values of the equilibrium constant and separation factor have been calculated. Here, the effect of the synergistic
agent (18C6 or B18C6) on the extraction process is discussed. 相似文献
11.
Takumi Maeda Keiichi Kimura Toshiyuki Shono 《Fresenius' Journal of Analytical Chemistry》1982,313(5):407-410
Summary Solvent extraction of alkaline earth metal picrates with poly- and bis(crown ether)s containing benzo-15-crown-5- and benzo-18-crown-6 moieties was carried out in a water-chloroform system. The poly- and bis(crown ether)s showed larger extractability for the metal picrates than the corresponding monocyclic crown ethers. Especially, poly- and bis(benzo-15-crown-5), and bis(benzo-18-crown-6) were found to have relatively high extractability and selectivity for Ba2+ and Sr2+, respectively.
Lösungsmittelextraktion von Erdalkalipikraten mit Hilfe von Poly- und Bis-Kronenethern
Zusammenfassung Poly- und Bis-Kronenether mit Benzo-15-krone-5- und Benzo-18-krone-6-Einheiten wurden zur Extraktion von Erdalkalipikraten im Wasser-Chloroform-System verwendet. Die genannten Ether zeigten eine bessere Extraktionsfähigkeit für die Pikrate als die entsprechenden monocyclischen Kronenether. Im Falle von Ba2+ und Sr2+ ergab sich eine besonders gute Extrahierbarkeit und Selektivität mit Poly- und Bis(benzo-15-krone-5)- und Bis(benzo-18-krone-6)-Ethern.相似文献
12.
A series of crown ether appended macrocyclic amines has been prepared comprising benzo-12-crown-4, benzo-15-crown-5, or benzo-18-crown-6 attached to a diamino-substituted cyclam. The Co(III) complexes of these three receptors have been prepared and characterized spectroscopically and structurally. Crystal structures of each receptor in complex with an alkali metal ion and structures of the benzo-12-crown-4 and benzo-15-crown-5-receptors without guest ions are reported. 2D NMR and molecular mechanics modeling have been used to examine conformational variations upon guest ion complexation. Addition of cations to these receptors results in an appreciable anodic shift in the Co(III/II) redox potential, even in aqueous solution, but little cation selectivity is observed. Evidence for complex formation has been corroborated by (23)Na and (7)Li NMR spectroscopy and electrospray mass spectrometry. 相似文献
13.
Jerzy Strzelbicki A. Charewicz Richard A. Bartsch 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(1):57-64
The proton-ionizable crown ethers, 2-[(sym-dibenzo-14-crown-4)oxy]-decanoic acid (1), 2-[sym-dibenzo-16-crown-5)oxy]decanoic acid (2), and 2-[sym-dibenzo-19-crown-6)oxy]decanoic acid (3) efficiently extract Co(II) and Ni(II) ammine cations from highly alkaline aqueous solutions (pH>10) into chloroform. For extractions of the individual metal species,2 is more efficient than1 or3. In competitive extraction systems, good selectivity for Co(II) ammine cations over Ni(II) ammine cations is observed. 相似文献
14.
A. N. Chekhlov 《Russian Journal of General Chemistry》2009,79(2):278-282
New mixed complex compound aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)(tetrachlorocuprato(II)-Cl)potassium, [K(CuCl4)(Db18C6)]? · [K(Db18C6)(H2O)]+, is synthesized and its crystal structure is studied by the method of x-ray structural analysis. The structure includes two independent complex ions, both of guest-host type: two cations K+ are located in the respective cavities of the Db18C6 crown-ligand (one in each) and each is coordinated by all its six O atoms and one Cl atom of the anion-ligand [CuCl4]2? or O atom of the ligand water molecule. Coordination of these two K+ cations is completed to hexagonal pyramidal one by formation by each of unusually weak coordination bond K+ → π(\(C\dddot - C\)) with two C atoms of respective benzene ring in the neighboring Db18C6 ligand. In this crystal structure the complex anions and cations form dual infinite chains via these coordination bonds and interionic O-H?Cl hydrogen bonds. 相似文献
15.
The properties of cis- and trans-bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 units as complexants and extractants for alkali metal picrates have been studied. The optical spectra suggest that the cis-bis(crown ether)s can form intramolecular 2:1 crown ether unit/cation complexes with particular metal cations easily, while the trans-bis(crown ether)s can form only 1:1 crown ether unit/cation complexes because of the unfavourable trans configuration for the formation of the 2:1 complexes. It was found that the cis isomer possesses much higher extractive power than the trans isomer for the metal cations, which also reflects their complexing properties. The extraction equilibrium constants and thermodynamic quantities have been also evaluated, and the effect of the stereochemical structure of the bis(crown ether) on the complexing and extractive properties is discussed. 相似文献
16.
Bis(Benzo-18-crown-6) Derivatives: Synthesis and Ion-Sensing Properties in Plasticized PVC Membranes
Róbert Bereczki Béla ÁGai István Bitter László Tōke Klára Tóth 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(1-2):45-50
Several mono-and bis(benzo-18-crown-6) ethers comprising o-nitrophenyl urethanemoieties were synthesized and studied as ionophores in PVC membrane electrodes. Thebis(crown ether)s were found to exhibit good potentiometric Cs+ selectivity overmono and divalent cations as compared to the respective mono(crown ether)s. 相似文献
17.
Monika Wysocka-?o?opa Krzysztof Winkler Suresh Gadde Francis D’Souza 《Journal of Solid State Electrochemistry》2012,16(1):65-74
Redox active films have been generated via electrochemical reduction in a solution containing palladium(II) acetate and fulleropyrrolidine
with covalently linked crown ethers, viz., benzo-15-crown-5 and benzo-18-crown-6. In these films, fullerene moieties are covalently
bonded to palladium atoms to form a polymeric network. Films show ability to coordinate alkali metal cations from the solution.
Therefore, in solutions containing salts of alkali metal cations, benzo-15-crown-5-C60/Pd and benzo-18-crown-6-C60/Pd films are doped with cations coordinated by crown ether moiety and anions of supporting electrolyte which enter the film
to balance positive charge. These films are electrochemically active in the negative potential range due to the reduction
of the fullerene moiety. Reduction of the polymer is accompanied by the transport of supporting electrolyte ions between solution
and solid phase. In solution containing alkali metal salts, the process of film reduction is accompanied by the transport
of anions from the film to the solution. In the presence of tetra(alkyl)ammonium salts, transport of cations from the solution
to the film takes place during the polymer reduction. 相似文献
18.
L. A. Kartsova O. V. Markova A. I. Amel’chenko N. D. Ostryanina 《Journal of Analytical Chemistry》2000,55(3):270-279
The use of crown compounds (18-crown-6, benzo-18-crown-6, dibenzo-18-crown-6, benzo-15-crown-5, dibenzo-24-crown-8, 4,13-diaza-18-crown-6,4,13-dibenzyl-diaza-18-crown-6,
and cryptand [2.2.2]) as components of stationary phases in the determination of organic compounds by gas chromatography is
studied. The polarity, selectivity, efficiency, and working temperature ranges of stationary phases based on crown ethers
and cryptand as well as conventional stationary phases for gas chromatography are compared. The influence of the type and
number of heteroatoms, the conformational lability of the cavity, and the presence of substituents on the polarity and selectivity
of the stationary phases under study is revealed. Preferable types of interactions of stationary phases containing crown compounds
with organic compounds of different classes are discussed. It is concluded that phases of the mixed type based on crown ethers
are promising for improving the selectivity and efficiency of gas-chromatographic separation 相似文献
19.
S. V. Paramonov O. A. Fedorova V. P. Perevalov V. Lokshin V. Khodorkovsky 《Russian Chemical Bulletin》2008,57(11):2381-2384
The reaction of hydroxy-substituted benzo-15(18)-crown-5(6) ether or benzo-18-crown-6 ether with β-phenylcinnamaldehyde in
the presence of titanium tetraethoxide yielded crown-annulated 2,2-diphenylbenzopyrans. The compounds are photochromic, and
the spectral characteristics of their colored form are unusual for this class of chromenes. 相似文献
20.
Keiichi Kimura Hiroshi Tamura Toshiyuki Shono 《Journal of Electroanalytical Chemistry》1979,105(2):335-340
Caesium-selective PVC membrane electrodes based on bis(crown ether)s containing benzo-18-crown-6 moieties were prepared using two kinds of plasticizers. Selectivity coefficients for various interfering monovalent ions were determined by the mixed solution method, and were found to relfect the complexing property and extractability of the bis-(benzo-18-crown-6)s. The electrochemical selectivity was also compared with that of the corresponding monocyclic analog and valinomycin. 相似文献