Zinc(II)-selective sensors based on dibenzo-24-crown-8 in PVC matrix

Membranes of dibenzo-24-crown-8 (I) as an ion active material in poly(vinylchloride) (PVC) based matrix have been tried for zinc(II)-selective sensors. The effect of anion excluder, sodium tetraphenylborate (NaTPB) and plasticizers, tris(2-ethylhexyl)phosphate (TEP), tributylphosphate (TBP), dibutylphthalate (DBP), dibutyl(butyl)phosphonate (DBBP), 1-chloronaphthalene (CN) and dioctylphthalate (DOP) on the performance of the membrane electrodes has also been studied. It was observed that the membrane having the composition (I): PVC:NaTPB:DOP in the ratio 10:200:2:100 gave the best results with a wide working concentration range of 9.2 × 10⁻⁵ to 1.0 × 10⁻¹ M, Nernstian slope of 29.0 ± 0. 5 mV/decade of activity, fast response time of 12 s and good selectivity over a number of mono-, bi-, and trivalent cations. The sensor works well in a pH range 4.8-6.2 and can be employed for the estimation of zinc ions in partially non-aqueous medium having up to 10% (v/v) methanol, ethanol or acetone content. The practical utility of the sensor has been demonstrated by using it successfully as an indicator electrode in the potentiometric titration of Zn²⁺ with EDTA and also for the determination of Zn²⁺ in a real sample analysis of wastewater.     

Complexes of dibenzo-24-crown-8 with some sodium monoalkyl benzeneazophosphonates

Syntheses and properties of complexes of dibenzo-24-crown-8 with the sodium monoethyl ester and the sodium monobutyl ester of [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid, [α-(4-benzeneazoanilino)-N-4-hydroxybenzyl]phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl]phosphonic acid have been studied. The crystalline complexes formed were found to depend not only on the size of the cation and the crown ether cavity but also on the choice of anion and the reaction solvent. It was shown that the molecular structure and electronic configuration of the anion are important factors in a salt-ligand system which influence the case of solubilization and charge separation in solution. The complexes obtained were characterized on the basis of conductance measurements and UV, IR and ¹H NMR spectra.     

Supramolecular phthalocyanine dimers based on the secondary dialkylammonium cation/dibenzo-24-crown-8 recognition motif

[formula: see text] New unsymmetrically substituted DB24C8-phthalocyanines, which are able to form complexes with suitable dialkylammonium cations, have been prepared. These complexes most probably have a pseudorotaxane geometry.     

Paraquat substituent effect on complexation with a dibenzo-24-crown-8-based cryptand

Dibenzo-24-crown-8-based cryptand 4 forms 1:1 inclusion complexes with three paraquat derivatives, P1, P2, and P3, as demonstrated by proton NMR spectroscopy and X-ray analysis. However, it was found that methyl-substituted paraquat derivatives, P2 and P3, can bind cryptand 4 more strongly than non-methyl-substituted paraquat derivative P1. The association constants (Ka) were determined in acetone by using a UV-vis titration method to be 5.0 x 10(3) M(-1) for 4.P1, 1.0 x 10(5) M(-1) for 4.P2, and 1.2 x 10(5) M(-1) for 4.P3, respectively. In the solid state, 4.P2 and 4.P3 have similar T-type inclusion complexation conformations, which are very different from the pseudorotaxane-type complexation conformation of 4.P1. Theoretical calculations were done to explain these experimental results.     

二苯并-24-王冠-8、KI体系萃取痕量铜

王冠化合物选择性地结合阳离子,使无机盐溶于有机溶剂及类似酶功能的特性在分析化学、有机合成、高分子合成、金属离子的捕集和分离,以及对光学异构体的拆分、酶模拟、生物化学、生物物理、医药及农业等方面应用前景广泛。     

Solvent extraction separation of uranium(VI) with dibenzo-24-crown-8

Uranium(VI) was quantitatively extracted with 0.01M DB-24-crown-8 in nitrobenzene from 6 to 10M hydrochloric acid. From the organic phase uranium was stripped with 2M nitric acid and determined spectrophotometrically with PAR at 530 nm. Uranium(VI) was separated from a large number of elements in binary mixtures as well as from multicomponent mixtures. The method was extended to the analysis of uranium in geological samples and animal bone.     

New bis(benzimidazole) cations for threading through dibenzo-24-crown-8

[reaction: see text] We report a simple bis(benzimidazole) dication which can act as new template for threading through dibenzo-24-crown-8. The effect of the solvent and counterion on the magnitude of the binding interaction and on the hydrogen bonding array in the solid state is described.     

Solvent extraction separation of cesium with dibenzo-24-crown-8 from picrate solution

Cesium (25 g) was extracted with 0.03M DB-24-crown-8 at pH 3.0 from 0.01M picric acid in the presence of 2 ml methanol. It was stripped with 3 M perchloric acid and was determined by atomic absorption spectrophotometry. The nature of the extracted species was 111. Dichloromethane was a suitable diluent. Nitric and perchloric acid were the best stripping agents. Cesium was not only separated from alkali and alkaline earth elements but also from zirconium, hafnium, thorium, usually present in fission products. The method is applicable for determination of cesium from real samples.     

133Cs NMR study of Cs+ ion complexes with dibenzo-21-crown-7 and dibenzo-24-crown-8 in some mixed solvents

Complexation of the cesium ion with macrocyclic ligands, dibenzo-21-crown-7 and dibenzo-24-crown-8, was studied in binary solvent mixtures of dimethylsulfoxide with acetone, acetonitrile, propylene carbonate, pyridine and hexamethylphosphoramide (HMPA) as well as in pyridine-methanol mixtures. In the first four binary mixtures the complexation constants increased with decreasing amounts of dimethylsulfoxide (DMSO), the trend is reversed in the DMSO-HMPA system. In all of the above cases, the variation of the stability constant with composition was monotonic and showed good correlation with the inherent solvating ability of the neat solvents which form the mixture. In the pyridine-methanol system, however, for both complexes, the log K_f vs composition plots show several changes in direction. This behavior is probably due to a change in the structure of this binary solvent as the composition of the medium is varied.     

Extraction of microamounts of calcium into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of dibenzo-21-crown-7 and dibenzo-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CaL²⁺, CaL₂²⁺ and CaHL₂³⁺ (L = DB21C7, DB24C8) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Thermodynamics of cesium cation complexation with dibenzo-24-crown-8 in mixed nonaqueous solvents

Thermodynamics of complexation of cesium cation by dibenzo-24-crown-8 was studied in three binary solvent mixtures: acetonitrile-nitromethane (AN/NM),N,N-dimethylformamide-nitromethane (DMF/NM) and acetonitrile-propylene carbonate (AN/PC) using the¹³³Cs-NMR technique. In all cases the variation of the formation constant,K _f, with the solvent composition was monotonic:K _f increased as the mole-% of the solvent of low donicity was increased. The temperature dependence ofK _f indicated that the complexes are generally enthalpy stabilized, but entropy destabilized. The enthalpy and entropy of complexation reactions are quite sensitive to the solvent composition. However, their variation with solvent composition was not monotonic but showed maxima or minima at the isosolvation points of the cation or the complexed cation. In all cases an enthalpy-entropy compensating effect was observed.     

Complex formation of methyl viologen and diquat with macrocyclic ether dibenzo-24-crown-8

The complex formation of a coplanar N,N'-ethylene-bipyridinium dication and dibenzo-24-crown-8 in methanol was detected by electrochemical techniques. It is demonstrated here that a coplanar ring arrangement is not required for an efficient charge-transfer interaction between bipyridinium and crown. The much stronger complexation of methyl viologen was investigated by both electrochemical and spectral techniques. The presence of a benzene ring in the crown molecule is a condition for complex formation. The described complex exerts catalytic activity for the reduction of oxygen.     

Controlled photophysical behaviors between dibenzo-24-crown-8 bearing terpyridine moiety and fullerene-containing ammonium salt

A novel [2]pseudorotaxane was successfully constructed by the complexation of dibenzo[24]-crown-8 (DB24C8) derivative bearing terpyridine moiety (1) with lanthanide ion (Tb(3+)) and fullerene-containing ammonium salt (2), exhibiting the controlled photophysical behaviors as a reversible luminescent lanthanide switch in the presence of K(+) or 18-crown-6 (18C6).     

A cyclopendant complexon based on dibenzo-18-crown-6

A derivative of dibenzo-18-crown-6 containing dihydroxyphosphorylmethyl groups in the 4, 5, 4′, and 5′ positions of the benzene ring has been synthesized. Unlike dibenzo-18-crown-6, its phosphorylated derivative does not form stable complexes with cations of alkali and alkaline-earth metals. Complexes with transition metals are water-insoluble in most cases. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1789–1791. September, 1998.     

NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo-24-crown-8

Interaction of hydrated protons (HPs) with dibenzo-24-crown-8 (DBC in nitrobenzene-d(5) was studied by (1)H and (13)C NMR under assistance of ab initio-density functional theory (DFT) quantum calculations. HPs were afforded by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) with 3.5 M excess of H(2)O. The forming of a complex between HP and DBC leads to marked and additive relative shifts of both (1)H and (13)C signals. This was utilized for the estimation of the stabilization constant K of the complex. Its value is at least 10(6) l/mol, which agrees with the result of independent extraction method (log K = 6.3). Using absolute integral intensities of the HP signal in a water-saturated system, it was shown that the form of HP present in the complex must be H(5)O(2)(+), in accord with formerly published structure of the complex in crystalline form. The investigation of the dynamics of exchange between bound and free DBC by transverse relaxation using variably spaced pulses in the Carr-Purcell-Meiboom-Gill (CPMG) sequence or on-resonance rotating-frame relaxation with variable spin-lock field intensity was partly hampered by the fast relaxation of some signals in the complex because of relative immobilization of its internal motions. In order to remove these effects, a pulse sequence dipolar interaction-free transverse relaxation (DIFTRE) for static DIFTRE was devised and the MLEV17 pulse sequence with high intensity of electromagnetic field was used in a separate series of experiments. Using the results of these latter experiments, the correlation time of exchange was established to be about 0.8 ms, which complied with the shape of the spectra. The accompanying ab initio DFT calculations showed that the apparent symmetry of the molecules of both DBC and its complex with H(5)O(2)(+) was probably the result of averaging of energetically close conformations (five for DBC and four for the complex). Both NMR and the calculations show that the basic mode of binding of the ion in the complex is analogous to that found in crystal but the most pronounced conformation is slightly different.     

Modification of salsoline, salsolidine, and anabasine with dibenzo-24-crown-8-dicarboxylic acid dichloride

New derivatives of dibenzo-24-crown-8-dicarboxylic acid diamide with salsoline, salsolidine, and anabasine moieties were prepared by condensation of the alkaloids with 4′,4″(5″)-dibenzo-24-crown-8-dicarboxylic acid dichloride. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 471–473, September–October, 2006.     

Extraction of cesium into nitrobenzene using hydrogen dicarbollylcobaitate in the presence of dibenzo-24-crown-8

Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-24-crown-8 (DB24C8,L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺ and CsL⁺ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.