Conductometric study of 4',4''(5'')-Di-tert-butyldibenzo-18-crown-6 with mercury(II) and lantanium(III) metal cations in pure and binary mixed organic solvents

The complexation reaction of macrocyclic ligand, 4',4''(5'')-Di-tert-butyldibenzo-18-crown-6 with mercury(II) and lantanium(III) metal cations were studied in acetonitrile-tetrahydrofuran (AN/THF) and acetonitrile-methylacetate (AN/MeOAc) binary mixed solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complex formed between 4',4''(5'')-Di-tert-butyldibenzo-18-crown-6 (DtBDB18C6) with Hg2+and La3+ cations are affected by the nature of the solvent systems. A non-linear behavior was observed for changes of log Kf of (DtBDB18C6.Hg)2+ and (DtBDB18C6.La)3+ complexs versus the composition of the binary mixed solvents. The values of thermodynamic quantities (S°c, H°c) for formation of (DtBDB18C6.Hg)2+ and (DtBDB18C6.La)3+ complexs were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex is enthalpy stabilized and in all cases entropy stabilized and both parameters are affected by the nature and composition of the mixed solvents. In addition, the complex formation between 4',4''(5'')-Di-tert-butyldibenzo-18-crown-6(DtBDB18C6) with Hg2+and La3+cations were studied in pure AN and THF.

کلیدواژه ها:

4' ، 4''(5'')-Di-tert-butyldibenzo-18-crown-6 ، acetonitril-tetrahydrofuran ، acetonitril-methylacetate ، mercury (II) and lantanium (III) metal cations ، mixed organic solvents ، conductometry