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 Rationalisation of the activities of phenolic (vitamin E-type) antioxidants

2003 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Christopher J. Rhodes ◽  
Thuy T. Tran ◽  
Philip Denton ◽  
Harry Morris
Keyword(s):  
Free Energy ◽  
Vitamin E ◽  
Gibbs Free Energy ◽  
State Theory ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Gibbs Free Energy Change ◽  
Linear Free Energy ◽  
Free Energy Of Activation ◽  
Enthalpy And Entropy

Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

Potentiometric and thermodynamic studies of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)-sulfamoyl]phenylazo}-2-pyrazolin-5-one and its metal complexes

2006 ◽  
Vol 60 (1) ◽  
Author(s):  
A. Fouda ◽  
A. Al-Sarawy ◽  
E. El-Katori
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Stability Constants ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Effect Of Temperature ◽  
Water Mixture ◽  
Dissociation Process ◽  
The Stability ◽  
Metal Ligand

AbstractThe dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Cu2+, La3+, Hf3+, UO22+, Zr4+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable.

Linear Free Energy Relationship (LFER) Analysis of Dissociation Constants of 8-Hydroxyquinoline and Its Derivatives in Aqueous and Dioxane–Water Solutions

2013 ◽  
Vol 58 (6) ◽  
pp. 1470-1482 ◽  
Author(s):  
Waldemar Robak ◽  
Wiesław Apostoluk ◽  
Paweł Maciejewski ◽  
Julia Agnieszka Pielka ◽  
Joanna Natalia Kwiotek
Keyword(s):  
Free Energy ◽  
Dissociation Constants ◽  
Linear Free Energy Relationship ◽  
Water Solutions ◽  
Linear Free Energy

Chelating Tendencies of some N-(2-Acyl-1,3-Indandione) Tri Alkyl Ammonium Iodides

1971 ◽  
Vol 26 (9) ◽  
pp. 865-867
Author(s):  
M. K. Bachlaus ◽  
K. L. Menaria ◽  
P. Nath
Keyword(s):  
Free Energy ◽  
Complex Formation ◽  
Stability Constants ◽  
Copper Complex ◽  
Dissociation Constants ◽  
Iron Complex ◽  
Potentiometric Studies ◽  
The Stability ◽  
Alkyl Ammonium

The L-T.M.A.I. and L-T.E.A.I. have been synthesised and their dissociation constants are 7.943 × 10-10 and 1.413 × 10-10 respectively. The potentiometric studies show that these reagents form 1 : 1 complex with copper (II) and iron (II). The stability constants of copper complex and iron complex with L-T.M.A.I. are 5.75 and 6.05 respectively and for L-T.E.A.I., 5.97 and 6.215 respectively. The free energy of complex formation at 25°C are 7841 cals/mole and 8150 cals/mole for Cu(II) -L-T.M.A.I. and Fe(II) -L-T.M.A.I. respectively, whereas the free energy of the Cu(II) -L-T.E.A.I. and Fe(II) -L-T.E.A.I. are 8141 cals/mole and 8375 cals/mole respectively.

scholarly journals Estimating Free Energies of Formation of Titanate () and Zirconate () Pyrochlore Phases of Trivalent Lanthanides and Actinides

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Anpalaki J. Ragavan ◽  
Dean V. Adams
Keyword(s):  
Free Energy ◽  
First Principles ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Empirical Parameter ◽  
Trivalent Lanthanides ◽  
Linear Free Energy ◽  
Free Energy Of Formation ◽  
The Difference ◽  
Energy Of Formation

A linear free energy relationship was developed to predict the Gibbs free energies of formation (, in kJ/mol) of crystalline titanate (M2Ti2O7) and zirconate (M2Zr2O2) pyrochlore families of trivalent lanthanides and actinides (M3+) from the Shannon-Prewitt radius of M3+ in a given coordination state (, in nm) and the nonsolvation contribution to the Gibbs free energy of formation of the aqueous M3+ (). The linear free energy relationship for M2Ti2O7 is expressed as . The linear free energy relationship for M2Zr2O7 is expressed as . Estimated free energies were within 0.73 percent of those calculated from the first principles for M2Ti2O7 and within 0.50 percent for M2Zr2O7. Entropies of formation were estimated from constituent oxides (J/mol), based on an empirical parameter defined as the difference between the measured entropies of formation of the oxides and the measured entropies of formation of the aqueous cation.

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