Asian Journal of Chemistry, ( ISI ), Volume (20), No (1), Year (2008-4) , Pages (535-542)

Title : ( Study of complex formation between dicyclohexyl-18-crown-6 with La 3+, UO22+, Ag+ and NH 4+ cations in acetonitrile-nitromethane binary mixtures )

Authors: Glamhossein Ronagi , ,

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Abstract

The complexation processes of La3+, UO22+, Ag+ and NH4+ cations with macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6) was studied in acetonitrile-nitromethane binary solutions at different temperatures using the conductometric method. The conductance data show that with the exception of complexation of NH 4+ cation with this macrocyclic ligand, the stoichiometry of all the complexes which are formed in solutions, is 1:1 [M:L]. A different behaviour was observed in the case of complexation of NH4+ with DCH18C6 in which a 1:2 [M:L2] complex is formed in solutions. A non-linear behaviour was observed for changes of log Kf of (DCH18C6.La)3+, (DCH18C6.UO2)2+ and (DCH18C6.Ag)+ complexes versus the composition of the binary mixed solvents. This behaviour may be related to hetero selective solvation of the cations and the ligand and also solvent-solvent interactions in these binary mixed solvent systems. The values of thermodynamic quantities (ΔH°c, ΔS°c) for formation of the complexes were obtained from temperature dependence of their stability constants using the van t Hoff plots. The results show that in all solvent systems, positive values of ΔS°c characterize the formation of the complexes. The selectivity order of the ligand for the studied cations in pure acetonitrile and acetonitrile-nitromethane binary solutions (mol % AN = 50.0 and 75.0) was found to be La3+ > UO22+ > Ag+.

Keywords

, Acetonitrile, Nitromethane binary systems; Ag +; Conductometry; Dicydohexyl, 18, crown, 6; La3+; NH4+ cations; UO22+
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@article{paperid:1009111,
author = {Ronagi, Glamhossein and , },
title = {Study of complex formation between dicyclohexyl-18-crown-6 with La 3+, UO22+, Ag+ and NH 4+ cations in acetonitrile-nitromethane binary mixtures},
journal = {Asian Journal of Chemistry},
year = {2008},
volume = {20},
number = {1},
month = {April},
issn = {0970-7077},
pages = {535--542},
numpages = {7},
keywords = {Acetonitrile-Nitromethane binary systems; Ag +; Conductometry; Dicydohexyl-18-crown-6; La3+; NH4+ cations; UO22+},
}

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%0 Journal Article
%T Study of complex formation between dicyclohexyl-18-crown-6 with La 3+, UO22+, Ag+ and NH 4+ cations in acetonitrile-nitromethane binary mixtures
%A Ronagi, Glamhossein
%A ,
%J Asian Journal of Chemistry
%@ 0970-7077
%D 2008

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