scholarly journals Thermodynamic investigations of complexation between dibenzo 18-crown-6 with Ni2+, Zn2+ and Cd2+ cations in pure acetonitrile, pure dimethylesulfoxide and acetonitrile-dimethylesulfoxide binary mixtures using conductometric method

2019 ◽  
pp. 43-53
Author(s):  
Naresh Desai ◽  
Dhruvi Mehta ◽  
Raviprakash Chandrab ◽  
M.M. Maisuria
Keyword(s):  
Binary Mixtures ◽  
Stability Constants ◽  
Standard Enthalpy ◽  
Macrocyclic Ligand ◽  
Standard Entropy ◽  
Free Energies ◽  
Enthalpy Changes ◽  
Conductance Data ◽  
The Stability ◽  
Complexation Reactions

The stability constants of 1:1 (M-L) complexes of Dibenzo-18-crown-6 (DB18C6) with Ni2+, Zn2+ and Cd2+ cations have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and Ni2+, Zn2+ and Cd2+ cations is 1:1 (M:L). GENPLOT computer program used to find the stability constants of the complexes were obtained from fitting of molar conductivity curves. The selectivity order of DB18C6 for the metal cations changes with the nature and composition of the binary mixed solvent. We also determined the Gibbs standard free energies (∆G0), the standard enthalpy changes (∆H0) and standard entropy changes (∆S0) for formation of these complexes in acetonitrile – dimethylesulfoxide (AN-DMSO) binary mixtures for the complexation. The values of standard enthalpy changes (∆H0 ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy (∆S0) were calculated from the relationship ∆G0298.15 = ∆H0 - 298.15 ∆S0.

scholarly journals Solvents Influence On Thermodynamics Of Complexation Between Dibenzo 18-Crown-6 With Tl+, Cs+ And Uo22+ Cations In Pure Acetonitrile, Pure Dimethylesulfoxide And Acetonitrile-Dimethylesulfoxide Binary Mixtures By Conductometric Method

2019 ◽  
pp. 63-74
Author(s):  
Naresh Desai ◽  
Dhruvi Mehta ◽  
Raviprakash Chandra ◽  
M. M. Maisuria
Keyword(s):  
Binary Mixtures ◽  
Stability Constants ◽  
Standard Enthalpy ◽  
Macrocyclic Ligand ◽  
Standard Entropy ◽  
Free Energies ◽  
Thermodynamics Of Complexation ◽  
Enthalpy Changes ◽  
The Stability ◽  
Complexation Reactions

The stability constants of 1:1 (M-L) complexes of Dibenzo-18-crown-6 (DB18C6) with Tl+, Cs+ and UO22+ cations have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and Tl+, Cs+ and UO22+ cations is 1:1 (M:L). GENPLOT computer program used to find the stability constants of the complexes were obtained from fitting of molar conductivity curves. The selectivity order of DB18C6 for the metal cations changes with the nature and composition of the binary mixed solvent. We also determined the Gibbs standard free energies (∆G0), the standard enthalpy changes (∆H0) and standard entropy changes (∆S0) for formation of these complexes in acetonitrile – dimethylesulfoxide (AN-DMSO) binary mixtures for the complexation. The values of standard enthalpy changes (∆H0 ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy (∆S0) were calculated from the relationship ∆G0298.15 = ∆H0 - 298.15 ∆S0.

scholarly journals Complexation of Th(IV) and Eu(III) by α-isosaccharinic acid under alkaline conditions

2001 ◽  
Vol 89 (6) ◽  
Author(s):  
K. Vercammen ◽  
M.A. Glaus ◽  
Luc R. Van Loon
Keyword(s):  
Stability Constants ◽  
Data Sets ◽  
Complexation Reaction ◽  
Sorption Data ◽  
Alkaline Conditions ◽  
The Stability ◽  
Ph Range ◽  
Complexation Reactions ◽  
Best Fit ◽  
Isosaccharinic Acid

The complexation of Th(IV) and Eu(III) by α-isosaccharinic acid (ISA) has been studied in the pH range from 10.7 to 13.3 by batch sorption experiments, and the influence of Ca on the complexation was investigated. Sixteen data sets – each determined at variable ISA concentrations – are used to determine the stoichiometry of the complexation reactions and the stability constants. Based on best-fit analysis of the sorption data, it is postulated that 1:1 Th:ISA complexes are formed in the absence of Ca according to the complexation reaction: Th+ISA↔(ThISA)

Thermodynamic and kinetic studies of silver ion complexes with cyclic and open chain diaza-polyethers including cryptands in acetonitrile + water mixtures

1983 ◽  
Vol 36 (11) ◽  
pp. 2133 ◽  
Author(s):  
BG Cox ◽  
J Stroka ◽  
P Firman ◽  
I Schneider ◽  
H Schneider
Keyword(s):  
Stability Constants ◽  
Preferential Solvation ◽  
Sharp Decrease ◽  
Kinetic Studies ◽  
Strong Interactions ◽  
Free Energies ◽  
Open Chain ◽  
Free Energies Of Transfer ◽  
The Stability ◽  
Activated Complex

.The stability constants for Ag+ complexes of several diazapolyether ligands, L = (2,2,1), (2,1), (2,2) and (2) (Scheme 1), have been measured in acetonitrile and water mixtures. Rate constants for formation and dissociation of Ag(2,2,1)+, together with the free energies of transfer, ΔGtr, of (2,2,1) among the mixtures, are also reported, and are compared with corresponding values for the Ag+-(2,1,1) and Ag+-(2,2,2) systems. The solvent dependences of the stability constants and hence of ΔGtr(AgLCIO4) - AG,,(L) are almost identical for all systems, except for small differences at low water content between the behaviour of the bicyclic cryptand ligands [(2,2,2), (2,2,1), (2,1,1)] and the monocyclic and acylic ligands, attributable to effects of NH solvation in the latter group. The preferential solvation of Ag+ by acetonitrile in the mixtures results in a sharp decrease in the stability constants as acetonitrile is added to water, but the effect is partly compensated for by a corresponding decrease in the free energies of the complexes. A strong differentiation in the kinetic behaviour of the bicyclic cryptand ligands is observed. For (2,1,1) the formation rates are almost independent of solvent composition and the free energies of transfer of the activated complex, ΔG‡tr (Ag+. . .(2,1,1),ClO4-) closely parallels that of AgCIO4, whereas for the larger cryptands the formation rates show a stronger solvent dependence, and ΔG‡tr (Ag+. . .L,ClO4-) values much more closely resemble those of the stable complexes, ΔG‡tr (AgLClO4). It is suggested that for the smaller (2,1,1) ligand preferential solvation of Ag+ by acetonitrile still persists in the transition state, but that in the activated complex for (2,2,1) and (2,2,2) the strong interactions between Ag+ and the ligand nitrogens have already replaced the Ag+. . .N≡CCH3 interactions occurring for the uncomplexed Ag+ ion in the mixtures.

scholarly journals Study of Complex Formation Between Iodoquinol (IQ) and Co2+, Mn2+, Cd2+, Pb2+and Zn2+Cations in Binary Aqueous / Non-aqueous Solvent Using Spectrophotometry

2007 ◽  
Vol 4 (4) ◽  
pp. 581-586 ◽  
Author(s):  
A. Nezhadali ◽  
H. A. Hosseini ◽  
P. Langara
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Stability Constants ◽  
Spectrophotometric Method ◽  
Formation Constants ◽  
The Other ◽  
Aqueous Solvent ◽  
The Stability ◽  
Complexation Reactions

The complexation reactions between iodoquinol and Co2+, Mn2+, Cd2+, Pb2+and Zn2+cations were studied in different DMF/H2O binary mixtures at the ionic strength of 0.1(using NaNO3).The spectrophotometric method was used for the determination of formation constants and the stoichiometries. The stoichiometry of the complexes is established 1:1 by Job's and mole ratio methods. It was found that the stability constants of the complex formed between the ligand (IQ) and the cations in the all cases increase with increasing of the non-aqueous solvent. In the most cases the maximum formation constants between Zn2+ion and IQ were obtained respect to the other cations.

Using Linear Free Energy Relationship to Predict the Stability Constants of Aqueous Complexes of Metal-Organic Ligands

2004 ◽  
Vol 824 ◽  
Author(s):  
Huifang Xu ◽  
Yifeng Wang
Keyword(s):  
Free Energy ◽  
Metal Complexes ◽  
Stability Constants ◽  
Metal Cation ◽  
Dissociation Constants ◽  
Natural Environments ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Linear Free Energy ◽  
The Stability

AbstractThe Sverjensky-Molling linear free energy relationship was originally developed to correlate the Gibbs free energies of formation of an isostrutural family of solid phases to the thermodynamic properties of aqueous cations. In this paper, we demonstrate that the similar relationship also exists between metal complexes and simple metal cations in aqueous solutions. We extend the Sverjensky-Molling relationship to predict the Gibbs free energies of formation or dissociation constants for a family of metal complexes with a given complexing ligand. The discrepancies between the predicted and experimental data are generally less than 1.5 kcal/mol (or one log unit for stability constants). The use of this linear free energy correlation can significantly enhance our ability to predict the speciation, mobility, and toxicity of heavy metals in natural environments. According the obtained results, Gibbs free energies of formation of cations (δG0f, Mn+) can be used as an indicator for the hardness/softness of a metal cation (acid). The higher negative value of a metal cation, the harder acid it will be. It is logical to postulate that the coefficient a*ML characterizes the softness of a complexing ligand (base).

scholarly journals PHYSICAL AND CHEMICAL CHARACTERISTICS OF SUPRAMOLECULAR COMPLEXES OF GLYCIRRIZINIC ACID WITH PHYTOHORMONES

2020 ◽  
pp. 66-70
Keyword(s):  
Stability Constants ◽  
Uv Spectroscopy ◽  
Stoichiometric Composition ◽  
Supramolecular Complexes ◽  
Free Energies ◽  
Spectrometry Method ◽  
The Stability ◽  
Physical And Chemical ◽  
Ir And Uv Spectroscopy ◽  
Composition Of Complexes

The process of formation of supramolecular complexes of glycyrrhizinic acid with some phytohormones (indolylacetic acid, indolylbutyric acid, α-naphthyl acetic acid and kinetin) were studied with the aim of creation the plant growth stimulator. The complexes structure was studied using IR and UV spectroscopy methods. The prepared compounds described by some physicochemical parameters. The stability constants and stoichiometric composition of complexes were determined in an aqueous solution at pH of 7,2 using UV spectrometry method. In result, all complexes have composition as 1:1 ratio, except the kinetin complex which has 2:1 ratio. The stability constants were equal: KGA:IAA=1,86±1×104; KGA:IBA=2,51±1×103; KGA:NAA =2,70±1×103 и KGA:К=5,07±1×105. The Gibbs free energies of complex formation were calculated.

Mercury(II) and Lead(II) Complexes of 1-Oxa-7-thia-4,10-diazacyclododecane ([12]aneN2OS)

1999 ◽  
Vol 52 (1) ◽  
pp. 1 ◽  
Author(s):  
Trevor W. Hambley ◽  
Shahara Afshar ◽  
Sebastian T. Marcus ◽  
Lawrence R. Gahan
Keyword(s):  
Stability Constants ◽  
Macrocyclic Ligand ◽  
Protonation Constants ◽  
Secondary Amines ◽  
Monoclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Stability ◽  
Lead Complex

The mixed donor 12-membered macrocyclic ligand 1-oxa-7-thia-4,10-diazacyclododecane ([12]aneN2OS) has been synthesized and the mercury(II) and lead(II) complexes, [Hg([12]aneN2OS)(NO3)2] and [Pb([12]aneN2OS)(NO3)2], have been isolated and characterized by X-ray crystallography. Crystals of the mercury complex are monoclinic, space group P 21/c, a 9·576(2), b 10·757(2), c 14·789(4) Å, β 93·58(2)°, whilst crystals of the lead complex are monoclinic, space group P 21/n, a 19·490(7), b 8·010(2), c 19·576(6) Å, β 109·90(2)°. The protonation constants and stability constants have been determined potentiometrically in aqueous solution. The protonation constants for [12]aneN2OS (log KHL 9·13; log K H2L 6·85) appear typical for secondary amines in similar trans-substituted 12-membered macrocycles. The magnitudes of the stability constants (HgII, log KHgL 10·5; PbII, log KPbL 6·6) are consistent with trends observed previously for macrocyclic ligands as secondary amine donors are replaced with oxygen and thioether donors.

scholarly journals CONDUCTOMETRIC STUDY OF LIGAND STRUCTURE INFLUENCE ON THE Pb(II) COMPLEXATION WITH CROWN ETHERS

STED JOURNAL ◽  
2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Edita Bjelić ◽  
Mersiha Suljkanović ◽  
Jasmin Suljagić ◽  
Azra Kovačević
Keyword(s):  
Crown Ethers ◽  
Metal Ion ◽  
Macrocyclic Ligand ◽  
Complexation Reaction ◽  
Stoichiometric Ratio ◽  
Ligand Structure ◽  
Conductance Data ◽  
Conductometric Study ◽  
The Stability ◽  
Triton X

The conductometric study of ligand structure influence on the Pb(II) complexation with crown ethers in different solvents has been investigated. In this paper, the complexation reaction of macrocyclic ligand, 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), and Pb(II) cation was studied in different solvents: dichloromethane (DCM) and 1,2- dichloroethane (1,2-DCE). The effects of surfactant structure (Triton X-100 and Triton X-45) on the conductivity of the Pb(II) complex with 18-crown-6 and dibenzo-18-crown-6 ether have been investigated. The conductance data showed that the stoichiometry of the complexes in most cases is 1:1(ML). It is also demonstrated that the influence of crown ethers is deeply affected by the organic solvent used. In the solvents studied, the stability of the resulting complexes showed higher stability in dichloromethane comparing with 1,2- dichloroethane. Macrocyclic ligand 18-crown-6 showed more suitable for complexation of Pb(II) ions compared to dibenzo-18-crown-6. Adding a surfactant affected the higher absolute values of the conductivity of systems, but not the change in the stoichiometric ratio between a metal ion and macrocyclic ligand.

scholarly journals Phosphatidylcholine — Mg2+ equilibria in a monolayer at the air/water interface

2013 ◽  
Vol 11 (3) ◽  
pp. 424-429 ◽  
Author(s):  
Aneta Petelska ◽  
Zbigniew Figaszewski
Keyword(s):  
Surface Tension ◽  
Stability Constants ◽  
Equilibrium Theory ◽  
Water Interface ◽  
Free Energies ◽  
Air Water Interface ◽  
The Stability ◽  
Langmuir Method

AbstractAbstract The interaction between Mg2+ and a phosphatidylcholine (lecithin, L) monolayer at the air/water interface was investigated. Surface tension measurements (Langmuir method) of phosphatidylcholine monolayers as a function of Mg2+ concentration were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between phosphatidylcholine and Mg2+ result in significant deviations from additivity. An equilibrium theory was developed to obtain the stability constants and areas occupied by one molecule of LMg+ and L2Mg. The stability constants were K 1 = 9.95×102 m2 mol−1 and K 2 = 3.87×104 m2 mol−1. The area occupied by LMg+ is 77 Å2 molecule−1, while that occupied by L2Mg is 109 Å2 molecule−1. The Gibbs free energies of complexation for LMg+ and L2Mg are −16.91 ± 0.51 and −25.88 ± 0.76 kJ mol−1. Graphical abstract

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