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Vol. 25 No. 7 (2013): Vol 25 Issue 7

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Determination of Stability Constants of Dibenzo-18-Crown-6 Complexes with Ce3+, Y3+, UO22+ and Sr2+ Cations in Acetonitrile-Dimethylformamide Binary Solutions

https://doi.org/10.14233/ajchem.2013.AB215
G.H. Rounaghi
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran
M. Mohajeri
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran
R. Rahmanian
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran
S. Tarahomi
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran

Corresponding Author(s) : M. Mohajeri

mahmoh10@yahoo.com

Asian Journal of Chemistry, Vol. 25 No. 7 (2013): Vol 25 Issue 7

Abstract

The complexation reactions between Ce3+, Y3+, UO22+ and Sr2+ cations with dibenzo-18-crown-6 (DB18C6) was studied in acetonitrile-dimethyl formamide binary mixtures at different temperatures using conductometry method. The stability constants of the resulting 1:1 complexes were calculated from computer fitting of the molar conductance-mole ratio data. A non-linear relationship was observed between the stability constants (log Kf) of these complexes with the composition of acetonitrile-dimethyl formamide binary solutions, which was explained on the basis of changes occurring in the structure of the mixed solvents and also the preferential solvation of the cations, ligand and the resulting complexes in solutions. The results show that the selectivity order of dibenzo-18-crown-6 for the metal ions in pure DMF at 25 ºC is: UO22+ > Sr2+ > Ce3+ > Y3+, but this selectivity order is changed with the composition of the mixed solvents. The corresponding thermodynamic parameters (DHºC, DSºC) were obtained from temperature dependence of the stability constants using the van't Hoff plots. The results show that both parameters are affected by the nature and composition of the solvent systems.

Keywords

Dibenzo-18-crown-6 Mixed non-aqueous solvents Conductometry
Rounaghi, G., Mohajeri, M., Rahmanian, R., & Tarahomi, S. (2013). Determination of Stability Constants of Dibenzo-18-Crown-6 Complexes with Ce3+, Y3+, UO22+ and Sr2+ Cations in Acetonitrile-Dimethylformamide Binary Solutions. Asian Journal of Chemistry, 25(7), 4103–4106. https://doi.org/10.14233/ajchem.2013.AB215
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