Solvent extraction of sodium from water into nitrobenzene by using strontium dicarbollylcobaltate in the presence of benzo-15-crown-5

Summary From extraction experiments andg-activity measurements, the extraction constant corresponding to the 2Na⁺(aq)+SrL(nb)?2NaL⁺(nb)+Sr²⁺(aq) equilibrium taking place in the two-phase water-nitrobenzene system (L=benzo-15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as log K_ex(2Na⁺,SrL)=1.0±0.1. Further, the stability constant of the benzo-15-crown-5-sodium complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log b_nb(NaL⁺)=7.8±0.1.     

COMPETITIVE NMR STUDY OF THE COMPLEXATION OF SOME ALKALINE EARTH AND TRANSITION METAL IONS WITH 12-CROWN-4, 15-CROWN-5 AND BENZO-15-CROWN-5 IN ACETONITRILE SOLUTION USING THE LITHIUM-7 NUCLEUS AS A PROBE

Abstract

⁷Lithium NMR measurements were used to determine the stoichiometry and stability of Li⁺ complexes with 12-crown-4, 15-crown-5 and benzo-15-crown-5 in acetonitrile solution. A competitive ⁷Li NMR technique was also employed to probe the complexation of Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ ions with the same crown ethers. In all cases, the stability of the resulting 1:1 complexes was found to decrease in the order 15-crown-5 > benzo-15-crown-5 > 12-crown-4. Ca²⁺ and Cd²⁺ ions formed the most stable complexes in the series.     

Redox responsive crown ethers containing a direct link between the ferrocene redox-active centre and benzo crown ether. Crystal structure of a ferrocene benzo-15-crown-5 sodium complex

The binding of Na⁺, K⁺ and Mg²⁺ to benzo-15-crown-5 and aza-15-crown-5 directly-linked ferrocenes results in shifts of the ferrocene oxidation wave to more positive potentials. The magnitude of these anodic shifts is related to the charge/radius ratio of the cationic guest. The results of an X-ray diffraction study of the structure of a ferrocene benzo-15-crown-5 sodium complex are also reported.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.Graphical Abstract Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali CationsYU LIU*, JIAN-RONG HAN, ZHONG-YU DUAN and HENG-YI ZHANG This revised version was published online in July 2005 with a corrected issue number.     

Crown ether-facilitated transfers of alkali metal ions across the water-nitrobenzene interface

The transfer of Li⁺, Na⁺, K⁺ and Cs⁺ from water to nitrobenzene at their interface as facilitated by benzo-12-crown-4, benzo-15-crown-5, 4′-methylbenzo-15-crown-5 and benzo-18-crown-6 was studied by cyclic voltammetry. The mechanism of the transfer process was discussed and the stability constants of the complexes formed in nitrobenzene were determined.     

The inclusion behavior of benzo-15-crown-5 with hydrated transition metal picrates

Six kinds of benzo-15-crown-5 (L) adducts having the stoichiometric formula M(Pic)₂ · L · xH₂O (M=Mn, Cu, x=2; M=Co, Ni, Zn, Cd, x=4; Pic means picrate anion) have been synthesized and characterized by EA, IR, UV and molar conductance. The X-ray crystal structural analysis of the benzo-15-crown-5 adduct with hydrated copper(II) picrate revealed that the benzo-15-crown-5 molecule virtually acts as a second-sphere ligand, which associates with the copper(II) ion by hydrogen bonding of the coordinating water molecule. By the comparison of the IR, UV spectra and molar conductance of the new adducts prepared, it can be deduced that the other adducts exhibit the similar coordination environment to that of the copper adduct.     

Potentiometric study of complexation of phenylaza-15-crown-5, 4-nitrobenzo-15-crown-5 and dibenzopyridino-18-crown-6 and other derivative of 18-crowns-6 with Na+ ion in methanol

The complexation reaction of phenylaza-15-crown-5, and 4-nitrobenzo-15-crown-5, benzo-15-crown-5 and dibenzopyrdino-18-crwon-6, dibenzo-18-crown-6,dicyclohexyl-18-crown-6(cis and trans), and 18-crown-6 with Na⁺ ion in methanol have been studied by potentiometric method. The Na⁺ ion-selective electrode has been used both as indicator and reference electrode. The stoichiometry and stability constants of complexes of these crown ethers with sodium ion were evaluated by MINIQUAD program. The major trend of stability of resulting complexes of these macrocycle with Na⁺ ion varied in the order DCY18C6 > DB18C6 > 18C6 > DBPY18C6 > phenylaza-15C5 > benzo-15C5 > 4-nitrobenzo-15C5. The obtained results in particular stability constant of complexes of DBPY18C6, phenylaza-15C5 and 4-nitrobenzo-15C5 with sodium ion in comparison with other crowns ether are novel, and interesting.     

Extraction of Alkali Metal (Li, Na, K) Picrates with Benzo-15-crown-5 into Various Organic Solvents. Elucidation of Fundamental Equilibria Determining the Extraction-ability and -selectivity

To quantitatively elucidate the effects of the benzo group on the extraction-selectively and -ability of benzo-15-crown-5 (B15C5)for alkali metal ions, the constants of the overall extraction (K_ex), thedistribution for various diluents having low dielectric constants (K_D,MLA), and the aqueousion-pair formation (K_MLA) of B15C5-alkali metal (Li, Na, K) picrate 1:1:1 complexes (MLA) weredetermined at 25 °C. The partition constants of B15C5were also measured at 25 °C. The log K_MLA values for Li⁺, Na⁺, and K⁺ are -0.32 ± 0.22, 2.66 ± 0.19, and 0.71 ± 0.47, respectively. In going from 15-crown-5 (15C5) to B15C5, the benzo group considerably decreasesthe K_MLA value for the same alkali metal ion. The distributionbehavior of B15C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regularsolution theory, omitting chloroform. Molar volumes and solubility parameters of B15C5and the 1:1:1 complexes were determined. For every diluent, the K_ex valuefor B15C5 increases in the order Li⁺ < K⁺ < Na⁺. K_D,MLA makes anunfavorable contribution to the Na⁺ extraction-selectivity of B15C5 because of the smallest molar volume of the Na(B15C5)A complex. The Na⁺ extraction-selectivity of B15C5 is determined completely by much the highest K_Na(B15C5)A value.The extraction-ability and -selectivity of B15C5 for the alkali metal picrates are compared with those of 15C5on the basis of the underlying equilibrium constants.     

Stabilities and Transfer Activity Coefficients from Water to Polar Nonaqueous Solvents of Benzo-15-Crown-5- and 15-Crown-5-Alkali Metal Ion Complexes

Stability constants (K_ML) of 1 : 1 benzo-15-crown-5 (B15C5) complexes with alkali metal ions were conductometrically measured in water at 25°C. Transfer activity coefficients of B15C5 and 15-crown-5 (15C5) from water to polar nonaqueous solvents were determined at 25°C. By using these data and the literature values, transfer activity coefficients of the B15C5 and 15C5 complexes with alkali metal ions from water to the polar nonaqueous solvents were calculated to study the solute-solvent interaction of the crown ether complexes. The stability of the B15C5 complex is lower in water than in any other nonaqueous solvent. The K_ML value for B15C5 is always smaller than the corresponding K ML value for 15C5. The interaction of the B15C5 or the 15C5 complex with the solvents depends on the alkali metal ion in the crown cavity. All the B15C5 and 15C5 complexes undergo hydrophobic hydration, which is particularly stronger for the B15C5 complexes with Na⁺ and K⁺. The unexpectedly lowest stability of the B15C5- or the 15C5-alkali metal ion complex in water among all the solvents is caused by the hydrogen bonding between ether oxygen atoms of uncomplexed B15C5 or 15C5 and water.     

Bis-substituted benzo-15-crown-5 ethers as ion carriers in potassium ion-selective electrodes

Lipophilic bis-substituted ester and ether derivatives of benzo-15-crown-5 have been synthesised. The correlation between the structure and potentiometric ion-selectivity has been studied in PVC membrane ion-selective electrodes. An ion-selective potassium sensitive electrode based on 4,5-bis (biphenyloxymethyl)benzo-15-crown-5 exhibited the best electrode properties. The detection limit was loga _K = -5.4; logK _K,Na ^ppot = -3.5. The effect of the lipophilicity of neutral carriers upon electrode performance has been also discussed.     

Thermochemistry of interactions of Na+ with benzo-15-crown-5 ether in acetonitrile-water mixtures at 298.15 K

Enthalpies of dissolution of benzo-15-crown-5 ether (B15C5) in mixtures of acetonitrile with water and in solutions of NaI and NaBPh₄ (I=0.05 mol dm^–3) in these mixtures were measured at 298.15 K. From the obtained results and appropriate literature data, the thermodynamic functions of B15C5/Na⁺ complex formation in acetonitrile-water mixtures were determined. The enthalpies of transfer of the complex B15C5/Na⁺ from pure acetonitrile to the examined mixtures were calculated and are discussed.     

Stability Constants of Some Univalent Cation Complexes of 2,3-Naphtho-15-crown-5 in Nitrobenzene Saturated with Water

The extraction of micro amounts of cesium by nitrobenzene solutions of sodium, potassium and rubidium dicarbollylcobaltates (M⁺B⁻;M⁺=Na⁺,K⁺,Rb⁺) has been investigated in the presence of 2,3-naphtho-15-crown-5 (N15C5, L). The equilibrium data were explained by assuming that ML⁺ and ML₂⁺ complexes (M⁺=Na⁺,K⁺,Rb⁺, Cs⁺; L=N15C5) were present in the organic phase. The stability constants of the complex species ML⁺ and ML₂⁺ have been determined in nitrobenzene saturated with water. It was found that the stability of the complex cation ML⁺ (where M⁺=Na⁺,K⁺,Rb⁺, Cs⁺; L=N15C5) in water-saturated nitrobenzene solutions increases along the series Cs⁺<Rb⁺<K⁺<Na⁺, whereas that of the species ML₂⁺ in the same medium increases in the order Cs⁺<Rb⁺<Na⁺<K⁺.     

Effects of the nature of counterions in solution on interactions of phenoxazones, xanthones, and carbazoles containing benzo-crown groups with DNA

The interactions of DNA with phenoxazones, xanthones, and carbazoles containing the (benzo-18-crown-6)-4′-yl and (benzo-15-crown-5)-4′-yl radicals bonded to the chromophore via spacers of different lengths in the presence of Na⁺ and K⁺ ions were studied by spectrophotometry, circular dichroism, and dynamic birefringence. The thermodynamic parameters of the binding of the compounds with DNA and changes in the macromolecular parameters of the DNA molecule during complexation were determined. Based on the results of these studies, we suggested the models of bonding of these compounds to the double helix of DNA. It is shown that the mode of DNA binding with a phenoxazone derivative containing two (benzo-15-crown-5)-4′-yl radicals bonded via a fragment of glycine to chromophore depends on the type of the counterion in solution. In the presence of Na⁺, the chromophore is intercalated into the double helix of DNA; in the presence of K⁺, it is bound to DNA in the form of a dimer outside the double helix. The type of the counterion does not affect the mode of binding of other crown-containing compounds of actinocin with DNA. For compounds containing the (benzo-18-crown-6)-4′-yl radical, the mode of binding to DNA adepends only on the spacer length.     

Solvent extraction of microamounts of cesium into nitrobenzene by using potassium and rubidium dicarbollylcobaltates in the presence of benzo-15-crown-5

Extraction of microamounts of cesium by nitrobenzene solutions of potassium dicarbollylcobaltate (K⁺B⁻) and rubidium dicarbollylcobaltate (Rb⁺B⁻) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The equilibrium data have been explained assuming that the complexes ML⁺ and ML₂⁺ (M⁺ = K⁺, Rb⁺, Cs⁺) are present in the organic phase. The stability constants of the species ML⁺ and ML₂⁺ (M⁺ = K⁺, Rb⁺) in nitrobenzene saturated with water have been determined.     

SYNTHESIS OF NOVEL AMINOPHOSPHONIC DERIVATIVES OF BENZO-15-CROWN-5 ETHER

Synthesis of new aminomethylphosphonic acids containing benzo-15-crown-5 ether, is described. These compounds were obtained from the 4′-formylbenzo-15-crown-5 by a sequence of reactions, which afforded 4′-(aminomethylphosphono)-benzo-15-crown-5 and its N-benzyl derivative in high yields.     

Solvent extraction of sodium perrhenate by 3m-crown-m ethers (m = 5, 6) and their mono-benzo-derivatives into 1,2-dichloroethane: Elucidation of an overall extraction equilibrium based on component equilibria containing an ion-pair formation in water

Equilibrium constants () for the ion-pair formation of a complex ion NaL⁺ with ReO₄⁻ in water were determined potentiometrically at 25 °C and the ionic strength (I) of 0 mol dm⁻³ using a Na⁺-selective electrode. Here, crown ethers, L, were 15-crown-5 ether (15C5), benzo-15C5, 18-crown-6 ether (18C6) and benzo-18C6. Also, NaReO₄ was extracted by the L into 1,2-dichloroethane and then extraction constants (K_ex/mol⁻² dm⁶) for the species, NaLReO₄, were determined at 25 °C by AAS. These K_ex values were resolved into four component equilibrium constants containing K_MLA calculated at given I values. Based on these data, extraction-abilities of the L against the perrhenate were discussed in comparison with those of sodium picrate-L systems reported previously.     

Extraction of lead from water into nitrobenzene by using strontium dicarbollylcobaltate in the presence of benzo-15-crown-5

Summary From extraction experiments andg-activity measurements, the extraction constant corresponding to the equilibrium Pb²⁺(aq)+SrL(nb)?PbL(nb)+Sr²⁺(aq)taking place in the two-phase water-nitrobenzene system (L = benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated aslog K_ex(Pb²⁺,SrL)=0.1±0.1. Further, the stability constant of the benzo-15-crown-5-lead complex in nitrobenzene saturated with water was calculated for a temperature of25 °C:log b_nb(PbL)=13.2±0.1.     

The Synthesis of Novel Macrocycles,Part V. The Coumarin Crown Ethers and Cation Binding with Fluorescence Spectra

Abstract

The 4-H, 4-methyl and 4-phenyl derivatives of benzo-α-pyrone of 12-crown-4 and 15-crown-5 were synthesised starting from 4-substituted-6,7-dihydroxy- and 7,8-dihydroxybenzo-α-pyrones which reacted with dichloropolyethylene glycols in DMF/water/alkali carbonate. The coumarin-macrocycles were identified by elemental analysis, IR, EI-GC-MS as well as ¹H, ¹³C NMR spectroscopy. The full experimental and spectral data is reported along with ion binding data studied in acetonitrile using fluorescence spectroscopy. The binding of the fluorogenic coumarin-crowns with Li⁺, Na⁺ and K⁺ were recognized as specific alterations on their fluorescence spectra that strongly originated from the structures. The observed CEQFS depending on the bound cation radii and macrocycle size evidenced the rules of cationic recognition of macrocycles. Some 15-crown-5 derivatives exhibited interesting Li⁺ and Na⁺ binding selectivities.     

Cation-Coordinating Properties of Perfluoro-15-Crown-5

The coordinative properties of perfluoro-15-crown-5 with monocations were investigated using ¹⁹F NMR spectroscopy and ion-selective electrodes with perfluoro-15-crown-5 as the matrix of their sensor membranes and the fluorophilic tetrakis[3,5-bis(perfluorohexyl)phenyl]borate as ion exchanger site. The results show that perfluoro-15-crown-5 interacts weakly but significantly with Na⁺ and K⁺. Assuming 1:1 stoichiometry, the formal complexation constants were determined to be 5.5 and 1.7 M⁻¹, respectively. This weak binding is consistent with the strong electron withdrawing nature of the many fluorine atoms in the perfluorocrown ether. While perfluorinated crown ethers have been known to form host-guest complexes with the anions O₂⁻ and F⁻ in the gas-phase, this is the first study that quantitatively confirms cation binding to a perfluorocrown ether.