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 [Ln₂(bdc)₃(H₂O)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<i>x</i>Ln'_{2 -2<i>x</i>}(bdc)₃(H₂O)₄]_∞ with 0 ≤ <i>x</i> ≤ 1 based either on heavy ([Eu_2<i>x</i>Tb_{2 - 2<i>x</i>}(bdc)₃(H₂O)₄]_∞) or light ( [Nd_2<i>x</i>Sm_2-2<i>x</i>(bdc)₃(H₂O)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.