A new and selective capillary column coated with cationic diazacrown ether for separation of organic and inorganic anions by capillary electrophoresis

A new coated capillary has been introduced for capillary electrophoretic separation of anions by using a positively charged diazacrown ether with a 12-membered ring. A positive charge spread over the inner capillary surface led to a substantial anodic electroosmotic flow (EOF) over the range of migrating buffer of pH 2-11. Under the optimum conditions of 25 mM phosphate buffer at pH 7, the diazacrown-coated capillary showed a successful simultaneous separation of 7 inorganic anions and 13 aromatic anions (including positional isomers) in less than 15 min. The migration times of the sample anions and EOF marker for consecutive runs on a single column were highly reproducible, giving a relative standard deviation of 1%. Theoretical treatment of the migration behavior clearly demonstrated that ion association between the diazacrown and analyte anions is strongly dependent on the nature of the functional groups of anions (e.g., sulfonate groups > carboxyl groups) and the number of negative charges (e.g., trivalent anions > divalent anions > monovalent anions) on the analyte.     

Palladium-catalyzed amination in the synthesis of aza- and diazacrown trismacrocyclic compounds

Palladium-catalyzed C-N-cross-coupling of N,N′-bis(bromobenzyl) diazacrown compounds with two equivalents of 1-aza-15-crown-5 and 1-aza-18-crown-6 ethers furnished trismacrocyclic compounds with isolated macrocycles. Macrotricyclic cryptands were obtained when diazacrown ethers were used as N-components.     

Synthesis of Lariat Diazacrown Ethers with Terminal Amino Groups in the Side Chains

Treatment of diazacrown ethers with N-(haloalkyl)- and N-(haloethoxy)phthalimides gives the corresponding N,N'- substituted diazacrown ether. Hydrazinolysis of the latter then gives diazacrown ethers with terminal primary amino groups in the side chain. Their reductive methylation using formaldehyde in formic acid gives the dimethylamino derivatives. The presence of a lariat effect was demonstrated by treating the compounds obtained with picrates of alkali and alkaline-earth metals.     

Cationic diazacrown ethers as selectors for the separation of inorganic anions by capillary electrophoresis

Two types of positively charged diazacrown ether derivatives involving two quaternary ammonium ions in the 12- and 18-membered rings have been investigated as selectors for the separation of inorganic anions by capillary electrophoresis. Both the cationic macrocycles largely affected the electrophoretic mobilities of analyte anions, and a group of seven inorganic anions examined in this study was completely separated in less than 2.2 min by the use of the low concentration of the additives. From the determination of ion association constants, the cationic diazacrowns were found to show greater electrostatic interaction with divalent anions than with monovalent ones.     

Synthesis of azacrown ethers and benzocryptands by macrocyclization of podands at high concentrations of reactants

The reactions of 1,2-bis(2-Y-ethoxy)benzenes, N,N-bis(2-Y-ethyl)-N-phenylamines, or 2,6-bis(Y-methyl)pyridines (Y = I, Br, or OTs) with α,ω-polyoxaalkanediamines or diazacrown ethers in the presence or absence of alkali carbonates in a concentrated acetonitrile solution of the reactants afforded the corresponding azacrown ethers or cryptands in high yields.     

Macroheterocycles. 49. Simple synthesis of cryptands based on intracomplex macrocyclization

An effective method for synthesizing cryptands by reaction of bis(methyleneepoxy) diazacrown ethers with benzylamine and N,N-dibenzylethylenediamine is reported. The good yields of cryptands are explained by formation of an intermediate in which the placement of reaction centers is favorable for intramolecular closure due to binding of the macrocycle to substrate.For Communication 48, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1673–1675, December, 1989.     

Vibrational spectroscopy and dynamics of small anions in ionic liquid solutions

Fourier-transform infrared (FTIR) and time-resolved IR spectroscopies have been used to study vibrational band positions, vibrational energy relaxation (VER) rates, and reorientation times of anions in several ionic liquid (IL) solutions. The ILs primarily investigated are based on the 1-butyl-2,3-dimethylimidazolium ([BM(2)IM]) cation with thiocyanate (NCS-), dicyanamide (N(CN)2-), and tetrafluoroborate (BF4-) anions. Spectroscopic studies are carried out near 2000 cm-1 for the C[Triple Bond]N stretching bands of NCS- and N(CN)2- as the IL anion as well as for NCS-, N(CN)2-, and azide (N3-) anions dissolved in [BM2IM][BF4]. The VER studies of N(CN)2- are reported for the first time. VER of N3-, NCS-, and N(CN)2- is measured in normal solvents, such as N-methylformamide, to compare with the IL solutions. The spectral shifts and VER rates of the anions in IL solution are quite similar to those in polar aprotic, conventional organic solvents, i.e., dimethylsulfoxide, and significantly different than those in methanol, in which there is hydrogen bonding. Similar studies were also carried out for the anions in another IL, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), in which the C2 hydrogen is present. The results for the anions are similar to those in the [BM2IM] containing ILs, in which the C2 hydrogen is methyl substituted. This suggests that substituting this hydrogen has, at most, a minor effect on the degree of hydrogen bonding in the anion-IL solvation interaction based on the infrared spectra and dynamics.     

Spectrophotometric characterization of diazacrown ethers having two carbodithioate groups.

Diazacrown ethers having two carbodithioate groups were synthesized, and their spectrophotometric properties were studied. Diammonium 1,4,10,13-tetraoxa-7,16-diazacycrooctadecane-N,N'-bis(carbodithioate) (DA18CC) and ammonium 1,4,10-trioxa-7,13-diazacycropentadecane-N,N'-bis(carbodithioate) (DA15CC) reacted with most heavy-metal ions through their two carbodithioate groups, and also reacted with alkali-metal ions or alkaline earth-metal ions through their diazacrown rings. Although the UV-VIS absorption spectra of DA18CC and DA15CC were hardly influenced by the addition of alkali-metal ions or alkaline earth-metal ions, the spectra of some heavy-metal chelates of DA18CC and DA15CC were influenced. The composition ratio (metal:ligand) of Cu(II) and Pb(II) chelates of DA18CC and DA15CC was altered from 1:1 to 1:2 by the addition of alkali-metal ions or alkaline earth-metal ions. It is suggested that the change in the absorption spectra and the composition ratio of the chelates can be attributed to an alteration of the equilibrium among species of the heavy-metal chelates of DA18CC and DA15CC due to the coordination of alkali-metal ions or alkaline earth-metal ions into the diazacrown ring.     

Complexation of silver(I) with different substituted diaza-18-crown-6 ethers in methanol

A large number of derivatives of the diaza-18-crown-6 ligand have been synthesized and characterized. These derivatives have different alkyl or aryl side arms at the nitrogen donor atoms of the macrocyclic diazacrown ether. In some side chains additional donor atoms are available. These diazacrown ethers are used as ligands for the complexation of Ag^I in MeOH. The complexation reactions have been studied using potentiometric and calorimetric methods. The thermodynamic data show the absence of a lariat effect. The increase of the values of the reaction enthalpies are due only to changes in solvation of the different ligands.     

Complexation and fluorescence behavior of diazacrown ether carrying two anthryl pendants

Photoinduced electron transfer (PET) fluoroionophores (1b, 2b) that consist of diazacrown and two 9-anthryl pendants show fluorescent enhancement with various guest salts. The diaza-12-crown-4 derivative (2b) exhibited Zn(2+) selectivity and in the presence of this cation the host fluorescence intensity was increased by a factor of 182. The guest cation-induced fluorescence enhancement of 2b was larger than the diaza-18-crown-6 derivative (1b).     

EDTA-type Polymer Based on Diazacrown Ether as the Solubilizer of Barium Sulfate to Water

The EDTA dianhydride reacted with diazacrown ethers to obtain the water-soluble EDTA-diazacrown ether polymers 1-3. The effects of crown ether ring in the polymer chains including its cavity size on the solubilization of barium sulfate to water were investigated by comparison with the crown ring-free analogue 4. The result shows that the polymer 2 is the efficient solubilizer of BaSO4 and the highest solubilization efficiency of the BaSO4 to water is up to 72.5%.     

The nitrogen position effect on the selectivity of diazacrown ethers to metal ion

In this paper, the nitrogen position isomers of diaza-18-crown-6, diaza-15-crown-5, diaza-12-crown-4, and their complexes with Na⁺ ion are studied by the density functional theory. Their stable structures are identified by geometry optimization without strict for their geometry. The binding capability that reflects the selectivity of these diazacrown ethers to metallic ions is estimated by the binding energy. The position effects of nitrogen on the stability of these complexes are also investigated by the explicit natural bond orbital and atoms-in-molecule analysis. It is found that different nitrogen position in crown ring will result in different relative energy. To those diazacrown ethers under consideration, the calculation results show that 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane, 1,4-diaza-7,10,13-trioxacyclopentadecane, and 1,7-diaza-4,10-dioxacyclododecane exhibit higher metal binding selectivity than their corresponding nitrogen position isomers, respectively. Clearly, the position of nitrogen plays an important role in the selectivity of diazacrown ethers to metal ions in the system involved. This work will be help for the material design of ionic recognition and other related fields.     

TAS+(Z)-Me3CNSN- and TAS+(E)-Me3SiNSN-: does the anion-cation interaction influence the configuration?

TAS+ salts (TAS = (Me2N)3S) of the sulfur diimide anions Me3XNSN- (X = C (1a), Si (1b)) were prepared by Si-N bond cleavage from the corresponding sulfur diimides Me3XNSNSiMe3 and TAS-fluoride ((Me2N)3S+Me3SiF2-) and characterized by X-ray crystallography and multinuclear NMR spectroscopy. According to the experimentally determined bond lengths and theoretical calculations, the Me3XNSN- anions are best described as thiazylamides Me3X-N-S identical to N rather than sulfur diimides Me3X-N=S=N. In agreement with the calculated and experimentally determined structures of the isoelectronic thionylimides RNSO, 1a adopts the Z-configuration, which is electronically favored due to anomeric effects. The electronically disfavored E-configuration of 1b in the solid state can be explained by weak anion-cation interaction.     

Heats of protonation of amines,diazacrown ethers and cryptands in methanol

The heats of protonation of different amines, diazacrown ethers and cryptands in methanol have been measured using calorimetric titrations. The values of the reaction enthalpies decrease in going from primary over secondary to tertiary amines. The results for the protonation of diazacrown ethers and cryptands are not comparable with those obtained for the alkyl amines. Additional interactions between the proton and the oxygen donor atoms influence the values of the reaction enthalpy for the first protonation. The results for the second protonation reaction indicate that this proton is located outside the cavities of the macrocyclic and macrobicyclic ligands. This revised version was published online in July 2006 with corrections to the Cover Date.     

An ion pair receptor showing remarkable enhancement of anion-binding strengths in the presence of alkali metal cations

An ion pair receptor was prepared by coupling of a diazacrown ether and a rigid biindole scaffold bearing hydrogen bond donors of two indole NHs. The former serves as the cation-binding site and the latter functions as the anion-binding site. The anion-binding affinities to the receptor, determined by ¹H NMR titration experiments in 10% (v/v) DMSO-d₆/CD₃CN at 24 ± 1 °C, have been greatly improved when an alkali metal cation binds to the adjacent diazacrown ether. For example, the association constant between chloride and receptor alone is 7 M⁻¹, but the magnitudes increase into 120 M⁻¹, 14,000 M⁻¹, and 6200 M⁻¹ in the presence of lithium, sodium, and potassium ions, respectively. The enhanced binding affinities must be attributed to electrostatic interactions by possibly forming contact ion pairs.     

Permselectivity between two anions in anion exchange membranes crosslinked with various diamines in electrodialysis

A membranous copolymer crosslinked with divinylbenzene reacted with N,N,N′,N′-tetra-methylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propanediamine, and N,N,N′,N′-tetramethyl-1,6-hexanediamine to prepare highly crosslinked anion exchange membranes. More than 80% of both tertiary amino groups of the diamines reacted with chloromethyl groups of the membrane to form crosslinkage. After formation of the high crosslinkage of the membrane was confirmed with dialysis of a neutral molecule, electrochemical properties of the obtained membranes (mainly, relative transport number between two anions in electrodialysis) were evaluated: nitrate ions to chloride ions, sulfate ions to chloride ions, fluoride ions to chloride ions, and bromide ions to chloride ions. Though larger anions, in general, were difficult to permeate through the membranes due to high crosslinkage, the number of methylene groups of the diamines (which means the increase in hydrophobicity of anion exchange groups) also affected the relative transport number between two anions. The lower the hydration of anions, the higher the relative transport number of the anions through the membranes with the hydrophobic anion exchange groups. © 1996 John Wiley & Sons, Inc.     

Synthesis of a New Diaazacrown Ether Compound Interconnected with an Azacrown Ether and Decorated with a Long Lipophilic Chain

The synthesis of an original compound consisting of an azacrown ether interconnected with a diazacrown ether bearing an alkyl chain is described herein. This derivative is promising for numerous applications.     

Macrocyclic polyfunctional lewis bases-IX azacrown ethers

Several new diazacrown ethers and one tetraazacrown ether have been obtained.     

Carbon chains of type C2n+1N(-) (n=2-6): A theoretical study of potential interstellar anions

Linear anions of type C(2n+1)N(-) (n=2-6), which are expected to be good candidates for experimental investigation by microwave spectroscopy and radio astronomy, were studied by means of the coupled cluster variant CCSD(T). Making use of corrections taken over from HC(3)NC(3)N(-) and HC(5)N, accurate equilibrium structures ( approximately 0.0005 A accuracy in bond lengths) have been established for all five anions. The electric dipole moments increase strongly with increasing chain length. For C(13)N(-), a very large equilibrium dipole moment of 16.53 D (with respect to center-of-mass coordinate system, negative end of dipole at terminal carbon site) is predicted. The lowest vertical detachment energies, leading to (2)Sigma states of the radicals for C(3)N(-) and C(5)N(-) and to (2)Pi states in the case of the larger anions, are calculated to lie in the range of 4.40-4.63 eV. The ground-state rotational and quartic centrifugal distortion constants of C(5)N(-) are predicted to be 1389.4 MHz and 33.8 Hz, respectively. All anions studied appear to be fairly normal semirigid linear molecules. Throughout, good agreement with available matrix isolation IR spectroscopic data is obtained and many predictions of spectroscopic properties are made.     

Synthesis of diaza-crown-ether cholesteric liquid crystals

Five diaza-crown-ethers were synthesized and four of them shown to have smectic liquid crystalline properties. Their properties were determined by DSC and polarized microscopy. This type of smectogenic diazacrown ether has not been reported so far. A novel lyotropic crown ether liquid crystal was obtained from the thermotropic crown ether liquid crystal 7.