Enabling Superprotonic Phase Transitions in Solid Acids via Supramolecular Complex Formation: The Case of Crown Ethers and Alkali Hydrogen Sulfates

This investigation, combining both structural and spectroscopic analyses, sheds light on the intricate relationship between conduction properties and the initiation of dynamic motions within the anhydrous crystalline materials of 18-crown-6·KHSO4 (1) and 18-crown-6·RbHSO4 (2) and proves how the formation of supramolecular complexes is pivotal for inducing solid–solid transitions, leading to superprotonic phases, i.e., crystalline solids exhibiting an enhanced ability to conduct protons, as elucidated through impedance spectroscopic measurements. This multifaceted approach deepens our understanding of the phenomenon and sets the stage for further exploration and application in solid-state protonic conductors.