共查询到20条相似文献,搜索用时 15 毫秒
1.
Zh. F. Gesse V. A. Isaeva G. I. Repkin V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(1):53-58
Enthalpy changes are determined by calorimetry for the reactions of glycinate ion (Gly−) proto- nation and its complexation with Ag+ ion at a temperature of 298 K and ionic strength 0.1 (NaClO4) in an aqueous ethanol solvent containing 0.0–0.4 and 0.0–0.3 mole fraction of alcohol, respectively. An abnormal relationship
of enthalpy changes is found for the processes of stepwise formation of mono- and bis-glycinates of silver(I) in water. It
is shown that varying the ethanol content has virtually no effect on the exothermicity of Ag+ complexation reactions with glycinate ions at either coordination step and does not change the relationship of the step enthalpies.
An analogy is observed in the relationship of solvation contributions from the reagents to the value of Δtr
H° for the reactions of glycinate ion protonation and its complexation with silver(I) in aqueous ethanol solvents. 相似文献
2.
Mahmood Payehghadr Rahman Heidari 《Journal of inclusion phenomena and macrocyclic chemistry》2013,75(1-2):205-210
The complexation reaction between 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6, ligand and Li+, Na+, K+, Mg2+, and Ba2+ ions were studied conductometrically in acetonitrile, ethanol, and methanol solutions. The formation constants of the 1:1 and 2:1 complexes (metal to ligand) were calculated from the computer fitting of the molar conductance in various mole ratios at 10, 20, 30, and 40 °C. The enthalpy and entropy changes of the complexation reactions in acetonitrile, ethanol, and methanol were estimated at four different temperatures. 相似文献
3.
M. Izadyar G. H. Rounaghi S. Tarahomi M. Mohajeri 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(12):2039-2043
Conductometric titrations have been performed in acetonitrile-ethylacetate (AN-EtOAc) binary solutions at 288, 298, 308, and 318 K to obtain the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of Cd2+, Ni2+, and Ag+ cations with 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (cryptand 22DD). The stability constants of the resulting 1: 1 complexes formed between the metal cations and the ligand were determined by computer fitting of the conductance-mole ratio data. There is a non-linear relationship between the logK f values of complexes and the mole fraction of ethylacetate in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the Cd2+, Ni2+, and Ag+ cations with the ligand changes with the nature of the solvent. The standard enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, the complexation processes of the metal cations with the C22DD, is mainly entropy governed and the values of thermodynamic parameters are influenced by the nature and composition of the binary mixed solvent solutions. 相似文献
4.
The complexation reactions between Ag+ andTl+ ions with 15-crown-5 (15C5) and phenyl-aza-15-crown-5(PhA15C5) have been studied conductometrically in 90%acetonitrile-water and 50% acetonitrile - water mixed solvents attemperatures of 293, 298, 303 and 308 K. The stability constants of theresulting 1 : 1 complexes were determined, indicating that theTl+ complexes are more stable than the Ag+complexes. The enthalpy and entropy of crown complexation reactions were determined from the temperature dependence of the complexation constants.The enthalpy and entropy changes depend on solvent composition and the T S0
o–H0 plotshows a good linear correlation, indicating the existence of entropy –enthalpy compensation in the crown complexation reactions. 相似文献
5.
V. G. Alekseev A. N. Semenov P. M. Pakhomov 《Russian Journal of Inorganic Chemistry》2012,57(7):1041-1044
The complexation of Ag+ ions with L-cysteine anions (Cys2?) at 25°C was studied potentiometrically against the background of 0.1 M KNO3. The AgCys? (log?? = 11.14 ± 0.10), AgHCys (log?? = 20.77 ± 0.06), Ag2Cys (log?? = 20.32 ± 0.17), and Ag2HCys+ (log?? = 27.28 ± 0.12) soluble complexes were found to be formed. 相似文献
6.
Usacheva T. R. Sharnin V. A. Ledenkov S. F. 《Russian Journal of General Chemistry》2001,71(5):707-711
The stability of complexes and enthalpy of interaction of Ag+ ions with 18-crown-6 in waterdimethyl sulfoxide (DMSO) mixtures were determined by calorimetric titration in the range of mole fractions XDMSO from 0.0 to 0.97 at 298.15 K. With increasing concentration of the nonaqueous component in the solvent to XDMSO 0.3, the stability of the complex ion [AgL]+ increases, which is followed by a decrease in logK(AgL+) to 0.35 plusmn 0.15 at XDMSO 0.97. The exothermic effect of the reaction shows a similar trend. The presence of the extremum in the logK-XDMSO and r
H-XDMSO dependences is explained by the competition of two solvation contributions: destabilization of the ligand with decreasing water content in the solvent and formation of strong solvation complexes of Ag+ with DMSO. 相似文献
7.
S. F. Ledenkov V. N. Vandyshev A. S. Molchanov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(6):959-964
Enthalpies of the interaction of protonated dopamine with a hydroxide ion in water-ethanol mixtures in the concentration range
of 0–0.8 EtOH mole fractions are measured calorimetrically. The neutralization process of dopamine hydrochloride is shown
to occur endothermally in solvents with an ethanol concentration of ≥0.5 mole fractions. Standard thermodynamic characteristics
(Δr
H
○, Δr
G
○, and Δr
S
○) of the first-step acid dissociation of dopamine hydrochloride in solutions are calculated with regard to the autoprotolysis
enthalpy of binary solvents. It is found that dissociation enthalpies vary within 9.1–64.8 kJ/mol, depending on the water-ethanol
solvent composition. 相似文献
8.
M. A. Zevakin K. V. Grazhdan S. V. Dushina V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(8):1269-1272
The distribution coefficients of nicotinamide (NicNH2) and solubility products of nicotinamide-silver perchlorate were determined by the distribution and solubility methods over a wide range of water-ethanol (EtOH) solvent compositions. The Gibbs energies of transfer of NicNH2 and the AgNicNH 2 + complex cation from water into water-ethanol mixtures were calculated. The influence of H2O-EtOH solvent compositions on the stability of the nicotinamide-Ag+ complex was studied potentiometrically at a 0.25 ionic strength of the medium (NaClO4) and 25.0 ± 0.1°C. The stability of complexes increased as the concentration of ethanol in mixtures grew. Reagent solvation contributions to complex formation equilibrium shifts were analyzed. 相似文献
9.
N. N. Kuranova S. V. Dushina V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(5):792-795
The enthalpies of stepwise protonation of nicotinate ion (L−) in water-ethanol solvents were determined calorimetrically at 298.15 K. It was found that the reduced exothermicity of the
reaction of nicotinate ion protonation upon an increase of the organic component content in solution is due mainly to increased
solvation of the proton. The minor influence of solvent on the enthalpy of protonation of nicotinic acid (HL) is characterized
by compensation from solvation of the proton, the ligand, and its protonated form (H2L+). 相似文献
10.
Malihe Samadi Kazemi Elham Ataeei Malihe Nasrabadi 《Russian Journal of Electrochemistry》2016,52(10):975-982
The complexation reaction between Tl+, Ag+ and Pb2+ cations with 2,6-di(furyl-2yl)-4-(4-methoxy phenyl)pyridine as a new synthesis ligand in acetonitrile (ACN)–H2O and methanol (MeOH)–H2O binary solutions has been studied at different temperatures using conductometric method. The conductometric data show that the stoichiometry of the complexes is 1: 1 [M: L] and the stability constant of complexes changes with the binary solutions identity. Also, the structure of the resulting 1: 1 complexes was optimized using the LanL2dz basis set at the B3LYP level of theory using GAUSSIAN03 software. The results show that the change of logKf for (DFMP.Pb)2+ and (DFMP.Ag)+ complexes with the mole ratio of acetonitrile and for (DFMP.Ag)+ and (DFMP.Tl)+ complexes with the mole ratio of methanol have a linear behavior, while the change of logKf of (DFMP.Tl)+complex in ACN–H2O binary solutions (with a minimum in XACN = 0.5) and (DFMP.Ag)+ complex in MeOH–H2O binary solutions (with a minimum in XMeOH = 0.75) show a non-linear behavior. The selectivity order of DFMP ligand for these cations in mol % CAN = 25 and 75 obtain Tl+ > Pb2+ > Ag+ but in mol % CAN = 50, the selectivity order observe Pb2+ > Tl+ > Ag+. Also, this selectivity sequence of DFMP in MeOH–H2O (mol % MeOH = 75 and 100) and (mol % MeOH = 50) is obtained Pb2+ > Ag+ and Tl+ > Ag+ > Pb2+ respectively. The values of thermodynamic parameters show that these values are influenced by the nature and the composition of binary solution. In all cases, the resulting complexes are enthalpy stabilized and entropy destabilized. The TΔSC° versus ΔHC° plot of all obtained thermodynamic data shows a fairly good linear correlation which indicates the existence of enthalpy-entropy compensation in the complexation reactions. 相似文献
11.
K. V. Grazhdan S. V. Dushina V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(10):1734-1736
The heat effects of protonation of nicotinamide and formation of its complex with iron(III) were determined calorimetrically
at 25.00 ± 0.01°C and ionic strength 0.25(NaClO4) in water-ethanol solvent containing 0–0.75 ethanol mol fractions. The experimental and literature data were used to construct
the dependences of the enthalpy, entropy, and Gibbs energy of the reaction on the composition of the water-ethanol solvent.
The dependence of the enthalpies of both reactions passed an exothermic minimum at 0.1 ethanol mol fractions. The reagent
solvation contributions to the thermodynamic characteristics of transfer were analyzed. 相似文献
12.
V. N. Vandyshev N. A. Litova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(9):1592-1594
Heats of solution of L-proline in water-ethanol mixtures at ethanol mole fractions in the range 0.00 < X EtOH < 0.70 are measured at 298.15 K via calorimetry. Standard enthalpies of solution of proline in water and water-alcohol mixtures are calculated and analyzed. Enthalpy coefficients of pair and triple acid-alcohol interactions in water at low alcohol concentrations are calculated in terms of the McMillan-Mayer theory. The obtained enthalpy characteristics are compared to those for previously investigated proline-containing water-alcohol systems. 相似文献
13.
G. A. Gamov K. V. Grazhdan M. A. Gavrilova S. V. Dushina V. A. Sharnin A. Baranski 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(6):967-972
Solutions of iron(III) perchlorate in water, water-ethanol, and water-dimethyl sulfoxide solvents ( $x_{H_2 O} $ = 0.7 and 0.25 mole fractions) at ionic strength values I = 0.1, 0.25, and 0.5 are studied by IR spectroscopy. Analysis of the absorption bands of perchlorate ion shows that it does not participate in association processes. It is demonstrated that in the range of ionic strength values between 0 and 0.5 (NaClO4), it affects neither the results from potentiometric titration to determine the stability constants of the iron(III)-nicotinamide complex nor the thermal effects of complexation determined via direct calorimetry in a binary solvent containing 0.3 mole fractions (m.f.) of a non-aqueous component. 相似文献
14.
Usacheva T. R. Ledenkov S. F. Sharnin V. A. Gzejdzak A. 《Russian Journal of Coordination Chemistry》2001,27(3):203-207
The effect of a water–dimethyl sulfoxide solvent (X
DMSO= 0–0.97, where X
DMSOis the mole fraction of DMSO) on the thermodynamics of complexation between Ag+and 18-crown-6 and the solvation of all reagents involved in this equilibrium were studied. In aqueous solutions, the complex is stable mainly because of the enthalpy contribution to
r
G°. For X
DMSO> 0.3, the contributions from entropy and enthalpy become comparable in magnitude, but they are opposite in sign. In the binary solvent, the complex is most stable at X
DMSO= 0.2 to 0.3. Analysis of the enthalpy characteristics of reagent solvation showed that this solvent effect was due to the superposition of two opposite solvation contributions occurring with an increase in the DMSO concentration in the binary solvent, namely, the destabilization of the ligand solvate sphere and the formation of stable Ag+complexes with DMSO. 相似文献
15.
The complexation of Ag+ ions with anions of β-lactam antibiotics, such as benzylpenicilline (Bzp?) and oxacilline (Oxa?), in aqueous solution at 25°C and an ionic strength of 0.1 (KNO3) was studied potentiometrically using a silver indicator electrode. The formation constants of the complexes AgBzp (logβ = 2.21 ± 0.01), AgBzp 2 ? (logβ = 3.91 ± 0.02), Ag2Oxa+ (logβ = 4.89 ± 0.01), AgOxa (logβ = 2.88 ± 0.01), (logβ = 5.43 ± 0.01) were determined. 相似文献
16.
Deeb Marji Ziyad Taha 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):331-339
The thermodynamic stabilities of Ag+, Ni2+ and Fe3+with diaza-crown ethers have been determinedconductometrically in acetonitrile at temperatures of 293, 298, 303 and 308 K.Both the size of the macrocyclic ring and the hard and soft acidand base (HSAB) character of the metal ions influence the relative stabilities of the complexes. For the metal ions with diazacrown ethers the values of log Kf for the 1 : 1 complexesfollow the order Ag+ > Ni2+ > Fe3+in accordance with Pearson's principle of HSAB character. The enthalpy and entropy of complexation were determined from the temperature dependence of the complexationconstants. The complexation process is entropy governed. 相似文献
17.
Mehdi Taghdiri Mohammad Kazem Rofouei Mojtaba Shamsipur 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):181-186
The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K+, Rb+, Cs+ and Tl+ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation
constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data
at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the
order Tl+ > K+ > Rb+ > Cs+. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation
constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent
mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence
of enthalpy–entropy compensation in the complexation reactions. 相似文献
18.
M. A. Zevakin K. V. Grazhdan V. A. Sharnin S. V. Dushina 《Russian Journal of Inorganic Chemistry》2006,51(3):495-498
The effect of the water-ethanol and water-DMSO solvent composition on the stability of nicotinamide (NicNH2) complexes with Ag+ ions at an ionic strength of 0.25 (NaClO4) and a temperature of 25 ± 0.1°C is studied by potentiometric titration. An increase in the EtOH concentration in the mixed solvent is found to result in a higher stability of the nicotinamide complex with silver(I) ions; as the DMSO concentration increases, the complex becomes less stable. The results of the study are analyzed in terms of the solvation thermodynamic approach taking into account the electronic structure of the ligand and the solvation contributions of the fragments of the molecule. 相似文献
19.
Razieh Sanavi Khoshnood Elaheh Hatami Donya Arefi Fatemeh Zahra Maknoni 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(2):308-317
In the present work the complexation process between Ag+ and Mg2+ cations and 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine (HBFPY) ligand was studied in pure dimethylformamide (DMF), ethanol (EtOH), acetonitrile (AN) and in (DMF-EtOH), (AN-EtOH) and (DMF-AN) binary mixed solvent solutions at different temperatures using the conductometric method. Also in this work the complexation reaction between Ca2+, K+ cations and HBFPY ligand, was studied in pure dimethylformamide (DMF), propanol (PrOH), 1,4-dioxane (DOX), ethanol (EtOH) and in DMF-PrOH, DMF-DOX and DMF-EtOH binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between this ligand and the studied cations is 1 : 1 [ML]. In most cases, addition of HBFPY to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The stability constant of [Mg(HBFPY)]2+ complex in various neat solvents at 15°C decreases in order: EtOH > DMF > AN and the stability constant of [Ag(HBFPY)]+ complex in various neat solvents at 35°C decreases in order: DMF > EtOH. The values of standard enthalpy changes (ΔH° c ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS° c ) were calculated from the relationship ΔH° c,295.15= ΔH° c –298.15ΔS° c . 相似文献
20.
T. R. Usacheva I. A. Kuz’mina V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(5):747-750
The thermodynamic characteristics of complex formation between Ag(I) and 2,2′-dipyridyl (Dipy) in H2O-DMSO solvents were studied. The calorimetric data obtained were used to calculate the enthalpies of formation of [AgDipy]+ and [AgDipy2]+ in water-dimethylsulfoxide solvents containing from 0.0 to 0.8 mole fractions of DMSO. The solvation contributions of all reagents to changes in the stability of the [AgDipy]+ and [AgDipy2]+ complexes were analyzed. An increase in the concentration of dimethylsulfoxide in solvents was found to have opposite effects on the energy characteristics of formation of mono-and biligand complexes between Ag+ and Dipy. 相似文献