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1.
The equilibria between tungsten(VI) and iminodiacetic acid (IDA) have been studied in aqueous solution. The stoichiometry
and stability constants of the complexes formed are determined from a combination of potentiometric and Uv spectroscopic measurements.
All measurements are carried out at 25°C, pH 7.5 and different ionic strengths ranging from (0.1 to 1.0) mol dm−3 (NaClO4). According to these results, tungsten(VI) forms a mononuclear complex with IDA of the type (WO3L2−). By introducing two empirical parameters C and D in the complex-formation reaction between tungsten(VI) and IDA, the dependence
of the dissociation and stability constants on ionic strength is described by a modified Debye-Huckel-type equation. Finally,
a pattern for the ionic strength dependence is obtained. 相似文献
2.
《Physics and Chemistry of Liquids》2012,50(3):257-268
The formation constants of species formed in the systems H+?+?W(VI)?+?nitrilotriacetic acid (NTA) and H+?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm?3 NaClO4, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO3L3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO3L2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported. 相似文献
3.
N. K. Chaudhuri R. M. Sawant D. D. Sood 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):993-1011
Literature data on the stability constants of the fluoride complexes of the actinides in different oxidation states have been
compiled. In order to have a reasonable inter-comparison, the stability constant (β1) values obtained in diverse ionic strength media are converted to so called thermodynamic stability constants, β
1
0
using the DAVIES equation (a modification of Debye-Huckel equation). A correlation of the β
1
0
values with the fundamental properties of the actinide ions using various models available in the literature has been attempted.
Using the values of inonic radii and best available values of the stability constants of a large number of metal ions from
recent compilations a comparative study of the various models or relations available in the literature has been tried. For
metal ions in general, the semi-empirical relation recently developed by BROWN, SYLVA and ELLIS (BSE equation)_gives the best
correlation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification
in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally
determined values for actinides in different oxidation states is obtained in most of the cases. Further improvements in theoretical
relation as well as experimental data are required for better correlation. 相似文献
4.
E. P. Grishina A. M. Pimenova L. M. Ramenskaya 《Russian Journal of Electrochemistry》2009,45(8):938-940
The effects of temperature and component ratio to electroconductivity of ionic liquid BMImBr — (1.5 to 1.88 mol %) Ag Br were
studied. At 10 mol % AgBr concentration, the properties of ionic liquid were stabilized and the values of specific electroconductivity
χ, viscosity-corrected specific electroconductivity χη, and equation coefficients of the temperature curve of χ changed insignificantly.
The diffusion coefficient of silver complex ion was calculated: D
Ag + p = 1.07 × 10−7 cm2s−1. 相似文献
5.
The stability constants of complexes of dioxovanadium (V) ion and L-asparrtic acid were determined potentiometrically at various
ionic strengths of I = 0.1, 0.3, 0.5, and 0.7 mol. dm−3 at 25°C. A sodium chloride solution was used to maintain the ionic strength. The parameters based on these formation constants
were calculated and the dependence of protonation and the stability constants on ionic strength are described by a Debye-Huckel
type equation. 相似文献
6.
V. Ya. Kavun A. B. Slobodyuk E. I. Voit S. L. Sinebryukhov E. B. Merkulov V. K. Goncharuk 《Journal of Structural Chemistry》2010,51(5):862-868
The NMR (19F and MAS NMR 19F), IR, and Raman spectroscopic methods are used to study the ionic mobility and structure of a series of new glasses in ZrF4—BiF3—MF2 (M = Sr, Ba, Pb) systems in a temperature range of 180 K to 500 K. The temperature range, in which diffusion of fluorine
ions becomes the dominant form of ionic motion, is determined by the nature of the M2+ cation. The factors determining the basic model of the structure of glasses in ZrF4—BiF3—MF2 (M = Sr, Ba, Pb) systems and conditions under which bismuth polyhedra can participate in the construction of the glass network
are considered. According to the data of impedance spectroscopy, the studied glasses have relatively high ionic conductivity
(δ ≥ 10–4 S/cm above 480 K). 相似文献
7.
G. G. Gorboletova S. N. Gridchin A. A. Lutsenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(11):1856-1861
Heats of the interaction of Cu(NO3)2 solutions with L-glutamine solutions were measured directly by calorimetry at a temperature of 298.15 K and ionic strength
values of 0.5, 1.0, and 1.5 (KNO3). Using RRSU universal software, the experimental data were subjected to rigorous mathematical treatment with allowances
made for several concurrent processes in the system. The heats of formation of the CuL+ and CuL2 complexes were calculated from the calorimetric measurements. The standard heats of the complex formation of Cu2+ with L-glutamine were obtained by extrapolation to zero ionic strength. The complete thermodynamic characteristic (Δr
H
o, Δr
G
o, Δr
S
o) of the complex formation processes in a Cu2+—L-glutamine system was obtained. 相似文献
8.
Krisztina Kurin-Cs?rgei Viktor Horváth Miklós Orbán 《Reaction Kinetics and Catalysis Letters》2007,90(2):405-411
The BrO
3
−
— BrAc — Ru(bpy)
3
2+
subsystem is shown to represent the core oscillator that serves as source of the long lasting temporal and spatial periodic
behaviors observed in the BrO
3
−
— H2PO
2
−
— acetone — Mn2+ — Ru(bpy)
3
2+
— acid “double substrate-double catalyst” oscillatory batch system. The BrAc — the substrate of the core oscillator — is
formed and accumulated in the reactions taking place in the six-component system. BrAc was produced in a separate experiment
with bromide, acetone, acid and excess bromate and the mixture was used for bringing about patterns in the thin solution layer
after adding the Ru(bpy)
3
2+
catalyst. The two-dimensional reaction-diffusion patterns that appear in the subsystem and its parent system are very similar
in wave speed, wavelength, color and in the duration of the pattern evolution, therefore a common chemical origin is supposed
to exist in their formation. The role that the BrAc may play in the mechanism of the BrO
3
−
— reductant — acetone — catalyst type oscillators (∼ 30 variants) is also pointed out. 相似文献
9.
B. B. Tewari 《Russian Journal of Inorganic Chemistry》2011,56(1):133-138
Quantitative indication of the process of forming a complex comes from the evaluation of the stability constants or formation
constant, which characterize the equilibria corresponding to the successive addition of ligands. Paper electrophoretic technique
is described for the study of beryllium(II) and cobalt(II) biologically significant binary complexes with sarcosine. The stability
constants of ML and ML2 complex species of Be(II)/Co(II)—sarcosine have been found to be (6.17 ± 0.09, 4.06 ± 0.04) and (4.27 ± 0.07, 2.98 ± 0.11)
(log-arithm stability constant values), respectively at ionic strength 0.1 Mol L−1 and a temperature of 35°C. 相似文献
10.
Aleksander Kufelnicki Jan Jaszczak Urszula Kalinowska-Lis Cecylia Wardak Justyn Ochocki 《Journal of solution chemistry》2006,35(5):739-751
Equilibrium studies have been carried out on complex formation of M2+ ions (M=Co, Ni, and Zn) with L = thymine, 6-chloromethyluracil, 5-hydroxymethyluracil, uracil, 6-methyluracil, and 6-umpm (dimethyl 6-uracilmethylphosphonate) in aqueous solution, at 25 ∘;C and an ionic strength of I=0.1 mol⋅L−1 (KNO3). Potentiometric results indicate the formation of ML species (coordination via N3) for Co(II) and Ni(II) as well as a hydroxo complex MLH−1—with a deprotonated water of the inner coordination sphere. Titrations of Zn(II) confirmed both the existence of ML and MLH−1 species with 6-chloromethyluracil as well as 5-hydroxymethyluracil, whereas for uracil, thymine, and 6-methyluracil the only species accepted pH-metrically was MLH−1. For all the ligands under study the complexation with Zn(II) was reinvestigated by means of ion-selective electrodes (ISE). The role of substituents is discussed. 相似文献
11.
The electron-transfer kinetics of the ionic surfactant complex cis-chloro/bromo(cetylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous perchlorate medium at μ=1.0 mol⋅dm−3 ionic strength have been studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an
excess of the reductant. The effects of [H+], ionic strength and [Fe2+] on the rate were determined. The reaction was found to be second order and showed to be independence of the acid concentration
in the range [H+]=0.05–0.25 mol⋅dm−3. The second order rate constant increased with surfactant–cobalt(III) concentration and the occurrence of aggregation of
the complex itself altered the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested
that the reaction of Fe2+(aq) with the cobal (III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of
these surfactant–metal complexes were obtained in aqueous solution from conductance measurements. Specific conductivity data
(at 303, 308 and 313 K) served for the evaluation of the temperature-dependence of the critical micelle concentration (CMC)
and the thermodynamics of micellization (ΔG
mo,ΔH
mo and ΔS
mo). 相似文献
12.
The development of an accurate aqueous thermodynamic model is described for oxalate species in the Na—Ba—Ca—Mn—Sr—Cl—NO3—PO4—SO4—H2O system at 25 °C. The model is valid to high ionic strength (as high as 10 mol·kg−1) and from very acid (10 mol·kg−1 H2SO4) to neutral and basic conditions. The model is based upon the equations of Pitzer and co-workers. The necessary ion-interaction
parameters are determined by comparison with experimental data taken from the literature or determined in this study. The
proposed aqueous activity and solubility model is valid for a range of applications from interpretation of studies on mineral
dissolution at circumneutral pH to the dissolution of high-level waste tank sludges under acidic conditions. 相似文献
13.
Clemente Bretti Concetta De Stefano Claudia Foti Ottavia Giuffrè Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1225-1245
Protonation constants of one thiocarboxylate (thioacetate) and four sulfur-containing carboxylates (2-methylthioacetate, thiolactate,
thiomalate, 3-mercaptopropionate) were determined by potentiometric measurements in a wide ionic strength range [0≤I≤5 mol⋅L−1 in NaCl and 0 ≤I≤3 mol⋅L−1 in (CH3)4NCl] at t=25 °C. For two of these ligands (2-methylthioacetate and thiolactate), the protonation enthalpies were also determined by
calorimetric measurements in NaCl ionic medium [0 ≤I≤5 mol⋅L−1] at t=25 °C. Individual UV spectra of the protonated and unprotonated 3-mercaptopropionate species, together with values of the
protonation constants, were obtained by spectrophotometric titrations. Results were analyzed in terms of their dependence
on the ionic medium by using different thermodynamic models [Debye-Hückel type, SIT (Specific ion Interaction Theory) and
Pitzer’s equations]. Differences among protonation constants obtained in different media were also interpreted in terms of
weak complex formation. 相似文献
14.
N. Sh. Lebedeva R. S. Kumeev G. A. Al’per E. V. Parfenyuk A. S. Vashurin T. V. Tararykina 《Journal of solution chemistry》2007,36(6):793-801
For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C6H4—OC11H23)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods.
It has been found that in o-xylene at concentrations of Zn(4—O—CO—C6H4—OC11H23)Pc higher than 6×10−4 mol⋅L−1
π–π dimers species are formed (λ
max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C6H4—OC11H23)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes.
Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C6H4—OC11H23)Pc—DABCO—Zn(4—O—CO—C6H4—OC11H23)Pc sandwich dimers (λ
max= 675 nm). 相似文献
15.
Ternary complex species formed by the V3+ cation with the picolinic acid (Hpic, HL) and dipicolinic acid (H2dipic, H2L) ligands in aqueous solutions have been studied potentiometrically (25 °C, I=3.0 mol⋅dm−3 KCl ionic medium) and by spectrophotometric measurements. Application of the least-squares computer program LETAGROP to the
experimental emf (H) data, taking into account the hydrolytic V(III) species and the binary V3+–picolinic acid and V3+–dipicolinic acid complexes, shows that under the investigated conditions the following ternary complexes are formed: [V(dipic)(pic)],
[V(dipic)(pic)(OH)]− and [V(dipic)(pic)2]−. The stability constants of the ternary complexes were determined by potentiometric measurements whereas the spectrophotometric
measurements were done in order to obtain a qualitative characterization of the complexes formed in aqueous solution. 相似文献
16.
The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu4BPh4) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed
using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λo) and the association equilibrium constants (K
A) have been derived. The limiting ion conductivities (λ_±o) have been evaluated according to the method of Krumgalz. The λ+
o values have been compared with λ+
o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G
A
o), enthalpy (Δ H
A
o) and entropy (Δ S
A
o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH
∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions. 相似文献
17.
Hemayat Shekaari Abolfazl Bezaatpour Rasoul Elhami 《Journal of solution chemistry》2012,41(3):516-524
The apparent molar volumes and viscosities of N,N′-bis(salicylaldehyde)-1,3-diaminopropane Schiff base (Salpr) have been determined in ionic liquid {1-pentyl-3-methylimidazolium
bromide ([PnMIm]Br)} + N,N-dimethylformamide (DMF) solutions at 298.15 K from density and viscosity measurements using a vibrating tube densimeter and
übbelohde type viscometer, respectively. These data have been used to calculate standard partial molar volumes, Vf 0V_{\phi} ^{0}, transfer partial molar volumes, Δtr
V
0, and viscosity B-coefficients of the solutions. The transfer partial molar volumes are negative, and decrease with increasing the concentration
of ionic liquid for all of the investigated solutions. It found that this ionic liquid interacts strongly with the Schiff
base (Salpr) and has desolvation effect on the Schiff base molecules. 相似文献
18.
Farukh Arjmand Shamima Parveen Mala Chauhan Shaiba Parveen Sartaj Tabassum 《Transition Metal Chemistry》2006,31(2):237-245
New mononuclear and dinuclear complexes [3-hydroxyethyl-1,3,5,8,11pentaazacyclotridecane]copper(II) (1)/nickel(II) (2) perchlorate and O,O ethane bridged bis-copper(II) (3)/nickel(II) (4) macrocycles have been synthesized and characterized by various spectroscopic techniques, viz. i.r., n.m.r., e.p.r., u.v.–vis. and conductance measurements. Spectral data and conductance measurements reveal that all
the complexes are consistent with square-planar geometry and are ionic in nature. The catalytic activity of the dinuclear
Cu(II) complex (3) in the presence of pyrocatechol was determined spectrometrically by monitoring the increase of the o-benzoquinone characteristic absorption band at 25,000 cm−1 with respect to time in DMF saturated with molecular oxygen. The kinetic parameters Vmax (2.8×10−3 M s−1) and KM (1.4×10−3 mm) have been determined by Michaelis–Menten method. Electrochemistry of the dinuclear Cu(II) complex has been studied in the
presence of molecular oxygen with pyrocatechol and without pyrocatechol at a scan rate of 0.1 V s−1 by cyclic voltammetry. On addition of pyrocatechol, complex shows a shift in Epc, Epa and E1/2 values indicating the oxidation of substrate (pyrocatechol). 相似文献
19.
E. P. Grishina A. M. Pimenova L. M. Ramenskaya 《Russian Journal of Electrochemistry》2009,45(12):1358-1362
The methods of potentiometry, electrochemical impedance spectroscopy, cyclic voltammetry, and gravimetry were used to study
the electrochemical behavior of a silver electrode in low-temperature ionic liquids of BMImBr and BMImBr—AgBr, and also the
process of cathodic reduction of Ag(I) compounds out of a BMImBr—AgBr melt. It is shown that an AgBr film is formed on the
silver surface and its properties are determined by the ionic liquid composition. It is found that the process of silver electrodeposition
from a BMImBr—AgBr binary alloy occurs irreversibly, at a high current efficiency (up to 100%) and a good quality of the deposit
at low current densities. At 70°C, the transfer coefficients of the cathodic process (α = 0.56 and 0.16) and diffusion coefficients
(D
Ag(I) = 0.48 × 10−7 cm2/s and 3.3 × 10−7 cm2/s) of silver-containing ions are determined in ionic liquids with the AgBr concentration of 0.81 and 1.53 mol/kg BMImBr,
accordingly. 相似文献
20.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):227-235
The complexation of terfenadine (Terf) with β-cyclodextrin (β-CD) in solution and solid state has been investigated by phase solubility diagram (PSD), differential scanning calorimetry
(DSC), powder X-ray diffractometry (PXD) and proton nuclear magnetic resonance (1H-NMR). The PSD results indicated that the salt saturation with the buffer counter ion (citrate−2, H2PO4−1 and Cl−1 ions) of Terf (pK
a = 9.5) and the hydrophobic effect play in tandem to increase the value of the complex formation constant (K11) measured at different conditions of pH, ionic strength, buffer type and buffer concentration. The correlation of the free
energy of complex formation (ΔG11) with the free energy of inherent solubility of Terf (ΔGSo) obtained by changing the pH, ionic strength and buffer concentration was used to measure the contribution of the hydrophobic
effect (desolvation) to complex formation. The hydrophobic effect was found to constitute 57.8% of the driving force for complex
stability, while other factors including specific interactions contribute −13.4 kJ/mol. 1H-NMR spectra of Terf–citrate and Terf–HCl salts gave identical chemical shift displacements (ΔΔ) upon complexation, thus
indicating that the counter anions are positioned somewhere outside of the β-CD cavity. DSC, XRPD and 1H-NMR proved the formation of solid Terf/acid/β-CD ternary complexes. 相似文献