Solution thermodynamics of lanthanide(III) cations (La3+, Pr3+ and Nd3+) and cryptands in propylene carbonate and in acetonitrile

Abstract

The thermodynamic parameters of complexation (ΔG^°_c, ΔH^°_c and ΔS^°_c) of lanthanide cations (La³⁺, Pr³⁺ and Nd³⁺) with cryptand 222 and cryptand 221 in acetonitrile and in propylene carbonate at 298.15 K are reported. The complexation process between these cations and these ligands in these solvents is enthalpy-controlled. The higher stability observed for these cations and these ligands in propylene carbonate with respect to acetonitrile is attributed to the increase in entropy observed for the complexation reaction in propylene carbonate. Enthalpies of solution of lanthanide and lanthanide(III) cryptates are reported. These data are used to derive singleion enthalpies of transfer of La³⁺, Pr³⁺ and Nd³⁺ from propylene carbonate to acetonitrile based on the Ph₄AsPh₄B convention. Enthalpies of coordination of lanthanide(III) cryptates in the solid state are calculated.