A Thermodynamic Study Between Kryptofix5 with Hg2+ and La3+ Cations in Acetonitryl – Methanol , Acetonitryl – Methyl acetate and Acetonitrile – Tetrahydrofurane Binary Mixtures Using The Conductometric Method

The complexation reaction between mercury (II) and lantanium (III) Cations with macrocyclic ligand,1,13-bis(8-quinolyl)-1,4,7,10,13-entaoxatridecane (Kryptofix5) was studied at different temperatures inacetonitrile–methanol (AN/MeOH), acetonitrile–methyl acetate (AN/MeOAc) and acetonitrile– tetrahydrofuran (AN/THF) binary mixtures using the conductometric method. The results show that in In most cases, the stoichiometry of the complex is 1:1 (ML). The values of formation constant of the complexwhich were determined using conductometric data, show that the stability of (Kryptofix5.Hg)2+ complex inpure solvents at 25°C changes in the following order: MeOAc AN MeOH THF and in the case of binarymixed solutions at 25°C it follows the order: AN– MeOAc  AN– MeOH AN–THF and the stability of (Kryptofix5.La)3+ complex in pure solvents at 25 °C changes in the following order: AN  THF  MeOAc MeOH and in the case of binary mixed solutions, it follows the order: AN–THF  AN–MeOAc  AN–MeOH. The values of standard thermodynamic quantities (H c and S c ) for formation of (Kryptofix5.Hg)2+ and (Kryptofix5.La)3+ complexes were obtained from temperature dependence of theformation constant using the Van’t Hoff plots. The results show that in most cases, the complex is entropyand enthalpy stabilized and these parameters are influenced by the nature and composition of the mixedsolvents. In most cases, a non-linear behavior was observed for variation of log Kf of the complexs versus the composition of the binary mixed solvents. In all cases, an enthalpy–entropy compensation effect was observed for formation of (Kryptofix5.Hg)2+ and (Kryptofix5.La)3+ complex in the binary mixed solvents.

کلیدواژه ها:

Hg2+ and La3+Cations ، Acetonitrile–Methanol ، Acetonitrile-Methyl acetate ، Acetonitrile-Tetrahydrofurane ، Conductometry ، Kryptofix5