共查询到20条相似文献,搜索用时 31 毫秒
1.
Emanuel Makrlík Petr Vaňura Jan Budka 《Monatshefte für Chemie / Chemical Monthly》2009,140(6):583-585
Abstract The stability constant of the dibenzo-18-crown-6·H3O+ cationic complex species dissolved in nitrobenzene saturated with water has been determined from extraction experiments in
the two-phase water–nitrobenzene system and from γ-activity measurements. Various structures of protonated dibenzo-18-crown-6 are discussed.
Graphical abstract
相似文献
2.
A combined extraction and DFT study on the complexation of the silver cation with dibenzo-18-crown-6
Emanuel Makrlík Petr Toman Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2011,286(1):137-140
Abstract
Extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements were used to determine the stability constant of the dibenzo-18-crown-6·Ag+ complex species in nitrobenzene saturated with water. Furthermore, the structure of the resulting complex was derived by means of theoretical calculations at the density functional level. 相似文献3.
From extraction experiments with 22Na tracer, the exchange extraction constants corresponding to the NH4
+(aq) + NaL+ (nb)NH4L+(nb) + Na+ (aq) equilibrium taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and dibenzo-24-crown-8; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the NH4L+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the order dibenzo-24-crown-8 (DB24C8) < dibenzo-18-crown-6 (DB18C6) < dicyclohexyl-18-crown-6 (DCH18C6) < 18-crown-6 (18C6). 相似文献
4.
Petr Toman Emanuel Makrlík Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2011,287(2):569-571
Abstract
By using quantum mechanical calculations, the most probable structures of free dibenzo-18-crown-6 ligand and the cationic complex species of Cs+ both with one and with two dibenzo-18-crown-6 ligands were derived. In these two complexes, the “central” cation Cs+ is bound by strong bond interactions to the corresponding ethereal oxygen atoms of the parent crown ligand. 相似文献5.
P. K. Mohapatra V. K. Manchanda 《Journal of inclusion phenomena and macrocyclic chemistry》1996,25(4):257-265
Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL+].[HPu(Cl)
6
–
] and [HL+]2·[Pu(Cl)
6
2–
] as ion-pairs (where L represents the crown ether) is suggested. 相似文献
6.
Petr Toman Emanuel Makrlík Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2010,287(2):301-304
Abstract
From extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements, the stability constant of the benzo-18-crown-6–ammonium complex in nitrobenzene saturated with water was determined. Furthermore, the structure of the resulting complex was derived by means of theoretical calculations at the density functional level. 相似文献7.
Purvi B. Desai Rahul M. Kotkar Ashwini K. Srivastava 《Journal of Solid State Electrochemistry》2008,12(9):1067-1075
The electrochemical behaviour of pyridoxine hydrochloride (pyridoxine HCl) at the plain carbon paste electrode and the electrode
modified with oxa crown ether has been studied using voltammetric and impedance measurements. The macrocycles used as modifiers
were 18-crown-6, dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 and dibenzo-24-crown-8, out of which DB18C6 gave better
response for pyridoxine HCl. Tris buffer (pH 10.3) was chosen as an appropriate medium among the several supporting electrolytes
of varying pH studied. The characterization of the DB18C6-modified electrode (CME-DB18C6) using kinetic parameters such as
number of electrons (n) and electron transfer coefficient (α) is studied by cyclic voltammetry. Electrochemical impedance spectroscopic measurements obtained confirm the current enhancement
over the modified electrode. Analytical applications of this electrode have been studied for the determination of pyridoxine
HCl. A sensitive linear working range of 0.6 to 100 μg cm−3 with a detection limit of 0.4 μg cm−3 by differential pulse voltammetry was observed for pyridoxine HCl on CME-DB18C6. However, on decreasing the scan rate to
5 mV s−1, the detection limit lowered to 0.2 μg cm−3. Interference from some vitamins like thiamine hydrochloride, riboflavin, nicotinamide, para-aminobenzoic acid, cyanocobalamin, folic acid and d-biotin and amino acid l-tryptophan was studied, and simultaneously, riboflavin, thiamine hydrochloride and pyridoxine HCl were determined over the
modified electrode, CME-DB18C6. The modified electrode is successfully used for the determination of pyridoxine HCl in multivitamin
pharmaceutical preparations. 相似文献
8.
G. H. Rounaghi M. Mohajeri S. Tarahomi R. Rahmanian 《Journal of solution chemistry》2011,40(3):377-389
The complexation reactions of dibenzo-18-crown-6 (DB18C6) with Ce3+, Y3+, UO22 +\mathrm{UO}_{2}^{2 +} and Sr2+ cations were studied in acetonitrile–dioxane (AN–dioxane) binary solvent solutions at different temperatures by the conductometric
method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance–mole
ratio data. The results show that dibenzo-18-crown-6 does not exhibit selectivity for the cation whose ionic size is closest
to the cavity size of this macrocyclic ligand in AN–dioxane binary solvent solutions. A nonlinear relationship was observed
between the stability constants (log 10
K
f) of these complexes with the composition of the AN–dioxane binary solvent. Values of thermodynamic parameters (DHc°, DSc°\Delta H_{\mathrm{c}}^{\circ}, \Delta S_{\mathrm{c}}^{\circ}) for complexation reactions were obtained from the temperature dependence of the stability constants. The results show that
the values along with the sign of these parameters are influenced by the nature and composition of the mixed solvent. 相似文献
9.
E. Makrlík P. Vaňura P. Selucký 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):549-554
Extraction of microamounts of calcium, strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of dibenzo-18-crown-6 (DB18C6, L) has been investigated. The equilibrium data have been explained assuming
that the complexes HL+, ML2+, ML22+ and MHL23+ (M2+ = Ca2+, Sr2+, Ba2+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. 相似文献
10.
E. Makrlík P. Vaňura P. Selucký 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(2):285-289
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. 相似文献
11.
A. N. Chekhlov 《Russian Journal of Inorganic Chemistry》2009,54(3):467-471
A new compound, dibenzo-18-crown-6 diaqua(dibenzo-18-crown-6)potassium triiodide [K(Db18C6)(H2O)2)+ · I3− · Db18C6 (I), is synthesized and studied by X-ray crystallography. The crystals of compound I are orthorhombic: a = 22.065 ?, b = 22.140 ?, c = 9.433 ?, Z = 4, space group Pccn. Structure I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation
to R = 0.098 for all 5974 unique reflections. Structure I contains the following asymmetric units: a half of the I3− centrosymmetric anion and two halves of the mixed equally average [K(Db18C6)(H2O)2]+ host—guest complex cation (a) and a free Db18C6 molecule, each stacked on the axes 2 of the perpendicularly averaged plane
of the eighteen-membered macroheterocycle. In complex I, both Db18C6 molecules (a and b) have a “butterfly” conformation with
approximate symmetry C
2v
.
Original Russian Text ? A.N. Chekhlov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 516–520. 相似文献
12.
Extraction of strontium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6
(DB18C6, L) has been investigated. the equilibrium data and the typical maxima concerning the dependencies of the Sr distribution
ratios on the total analytical concentration of DB18C6 in the system under study can be explained assuming that the particles
Sr2+, SrL2+, SrL2
2+, SrHL3+ and SrHL2
3+ are extracted into the nitrobenzene phase. The values of the corresponding extraction and stability constants of the extracted
species in nitrobenzene saturated with water have been determined. 相似文献
13.
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Na+(aq)+HL+(nb)⇆NaL+(nb)+H+(aq) taking place in the two-phase water-nitrobenzene system (L=18-crown-6; aq=aqueous phase, nb=nitrobenzene phase) was evaluated
as logK
ex
(Na+,HL+)=0.1. Further, the stability constant of the 18-crown-6-sodium complex in nitrobenzene saturated with water was calculated:
logβ
nh(NaL+)=8.0. 相似文献
14.
Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6 (DB18C6, L) was investigated. It was found, that besides hydrated cesium ion Cs
org
+
the complexes CsL
org
+
and CsL
2,org
+
were extracted to nitrobenzene phase. No maximums on dependencies of the cesium distribution ratio (D) on the concentration of crown in the systemc
L was found andD increased monotony withc
L. Values of extraction constants and stability constants of extracted species in nitrobenzene have been determined. 相似文献
15.
Guseva E. V. Busygina T. E. Gracheva L. S. Polovnyak V. K. Khasanshin R. A. Yarkova E. G. Yusupov R. A. 《Russian Journal of General Chemistry》2001,71(2):217-221
The products of the reactions between potassium hexachloroplatinate {K2PtCl6} and 18-crown-6 or dibenzo-18-crown-6 in acetonitrile were studied. Pure crystalline compounds [2K·2(18-crown-6)· 2CH3CN]2+·[PtCl6]2-·2H2O, [2K·dibenzo-18-crown-6·CH3CN]2
+·[PtCl6]2
-, and [2K·dibenzo-18-crown-6·CH3CN]2
+·[Pt2Cl10]2
- were obtained. Physicochemical properties of these compounds were studied, and their near- and far-IR IR spectra and thermogravimetric curves were considered. The composition of the complexes is determined by metal:ligand molar ratio and crown ether nature. It was found that acetonitrile is coordinated via the nitrogen atom. 相似文献
16.
Experimental and theoretical study on the complexation of the cesium cation with dibenzo-30-crown-10
E. Makrlík P. Toman P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1137-1140
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs+ (aq) + A− (aq) + 1(nb)
\rightleftarrows \rightleftarrows
1·Cs+(nb) + A−(nb) taking place in the two-phase water–nitrobenzene system (A− = picrate, 1 = dibenzo-30-crown-10; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex (1·Cs+, A−) = 4.0 ± 0.1. Further, the stability constant of the 1·Cs+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β
nb (1·Cs+) = 5.9 ± 0.1. Finally, by using quantum–mechanical DFT calculations, the most probable structure of the resulting cationic
complex species 1·Cs+ was derived. 相似文献
17.
Jan S. Jaworski Agnieszka Lewicka Romana Anulewicz 《Journal of inclusion phenomena and macrocyclic chemistry》2003,46(3-4):207-211
The complexation of mercury(II) cyanide with macrocyclic ligands 15-crown-5,18-crown-6 and dibenzo-24-crown-8 in dimethylsulfoxide was studied using199Hg NMR measurements. No significant complexation with 15-crown-5was observed. The stability constants Ks for 1 : 1 complexes with two other ligands were determined and found to be similar, in contrary to the results reported in nitrobenzene. Solvent effects on Ks values obtained are discussed in comparison with the literature data. X-ray crystal structure of Hg(CN)2.A18-crown-6 was also determined. 相似文献
18.
Y. Kudo T. Miyakawa Y. Takeda H. Matsuda S. Yajima 《Journal of inclusion phenomena and macrocyclic chemistry》1996,26(4):331-341
Stability constants (
1
NB
) of the 1:1 cationic complexes of Li+ Na+, K+ Ca2+ Sr2+ and Ba2+ with benzo-18-crown-6 (B18C6), Ca2+ and Sr2+ with 18C6 and dibenzo-18C6 and Li+, Na+, Ca2+, Sr2+ and Ba2+ with dibenzo-24-crown-8 in a nitrobenzene (NB) solution saturated with water (w) were determined at 25°C by ion-transfer polarography. From these values, distribution constants (K
D,ML) of the 18C6-derivative complex cations between the w- and NB-phases were evaluated using the thermodynamic relation:K
D,ML =K
1
NB
, whereK (mol dm–3) is an overall equilibrium constant of the processes related to the complexation in the w-phase. The data on the distribution of the 18C6-derivative complex cations between the two phases and the complexation in the NB-phase were examined on the basis of an increase in the number of water molecules hydrated to the species relevant to these processes. The 18C6 derivatives showed higher solubilities in the NB-phase than in the w-phase by complexing with the univalent-metal ions, while, for the divalent-metal ions, the derivatives showed lower solubilities in the NB-phase. 相似文献
19.
The dibenzo-18-crown-6 derivatives such as di(nitrobenzo)-18-crown-6 and di(aminobenzo)-18-crown-6 were synthesized by nitration reaction and catalytic hydrogenation with high selectivity. The chemical structures were determined by FTIR, 1H NMR, 13C NMR, and UV. Regarding the mixture of Ac2O and HNO3 as nitrating agent, the reaction exhibited commendable trans-isomer selectivity. Effects of nitrating agent ratio, reaction temperature and reaction time on yield of trans-di(nitrobenzo)-18-crown-6 were investigated. The yield of trans-di(nitrobenzo)-18-crown-6 was 62.9% for nitrating agent ratio of 1/1, reaction temperature of 50?°C and reaction time of 5?h. Moreover, effect of reaction time on trans-di(aminobenzo)-18-crown-6 was also studied. 相似文献
20.
G. H. ROUNAGHI M. S. KAZEMI 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):347-352
The transport experiments of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ag+ and Pb2+ metal cations were carried out by dibenzo-18-crown-6 (DB18C6), dibenzyl-diaza-18-crown-6 (Dibenzyl-diaza-18C6) and di-tert-butyl-dibenzo-18-crown-6 (Di-tert-butyl-DB18C6) using chloroform (CHCl3), 1,2-dichloroethane (1,2-DCE) and nitrobenzene (NB) organic solvents as liquid membranes. The source phase contained equimolar concentration of these metal cations and the source and receiving phases being buffered at pH=5 and pH=3, respectively. The obtained results show that the selectivity and the efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membranes in these experiments. A good selectivity was observed for silver (I) ion by dibenzyl-diaza-18C6 in all membrane systems. Dibenzo-18C6 and di-tert-butyl-DB18C6 showed the highest transport efficiency for cobalt (II) ion. The effect of stearic acid on transport efficiency was also investigated and the results show that the efficiency of transport of the heavy metal cations increases in the presence of this organic acid. 相似文献