Lanthanide-Based Coordination Polymers Molecular Alloys Stability: A Thermochemical Approach.

In this study, we investigate the thermodynamics of lanthanide-based coordination polymer molecular alloys. We demonstrate that if lanthanide ions have many chemical similarities, the solubility of homo-lanthanide-based coordination polymers can vary significantly from one lanthanide ion to another. Indeed, we experimentally determine the solubility constants of a series of isostructural homo-lanthanide coordination polymers, with general chemical formula [Ln 2 (bdc) 3 (H 2 O) 4 ] ∞ with Ln = La-Er plus Y and where bdc 2- symbolizes 1,4-benzene-di-carboxylate. Then, we extend the study to two series of isostructural molecular alloys with general chemical formula [Ln 2 x Ln' 2 -2 x (bdc) 3 (H 2 O) 4 ] ∞ with 0 ≤ x ≤ 1 based either on heavy ([Eu 2 x Tb 2 - 2 x (bdc) 3 (H 2 O) 4 ] ∞ ) or light ( [Nd 2 x Sm 2-2 x (bdc) 3 (H 2 O) 4 ] ∞ ) lanthanide ions. We found that whatever the solubility difference of the homo-nuclear compounds is, the configurational entropy is the main driving force of the stabilization of molecular alloys.