Krossing VIP-Paper II: The Ideal Ionic Liquid Salt Bridge for Direct Determination of Gibbs Energies of Transfer of Single Ions, Part II: Evaluation of the Role of Ion Solvation and Ion Mobilities

Zweiteiler: In der “Angewandten Chemie” wurden zwei Publikationen eines Projektes back-to-back veröffentlicht! Teil 2 beschreibt die ersten experimentellen Ergebnisse und bestätigt damit das in Teil 1 vorgestellte Konzept. Die Bestimmung von Einzelionen-Transferenthalpien ohne Verwendung von außerthermodynamischen Annahmen ist zum Greifen nah.

Andreas Ermantraut, Valentin Radtke, Niklas Gebel, Daniel Himmel, Thorsten Koslowski, Ivo Leito und Ingo Krossing.

Abstract

An important intermediate goal to evaluate our concept for the assumption-free determination of single-ion Gibbs transfer energies Δ_trG°(i, S₁⟶ S₂) is presented. We executed the crucial steps a) and b) of the methodology, described in Part I of this treatise, exemplarily for Ag⁺ and Cl⁻ with S₁ being water and S₂ being acetonitrile. The experiments showed that virtually all parts of the liquid junction potentials (LJPs) at both ends of a salt bridge cancel, if the bridge electrolyte is an “ideal” ionic liquid, that is, one with nearly identical diffusion of anion and cation. This ideality holds for [N2225]⁺[NTf2]⁻ in the pure IL, but also in water and acetonitrile solution. Electromotive force measurements of solvation cells between S₁and S₂ demonstrated Nernstian behavior for Ag⁺ concentration cells and constant like cell potentials for solutions with five tested Ag⁺ counterions.

DOI: 10.1002/anie.201707334