Singularity of proton transport in salts of orthoperiodic and orthotellurium acids: theoretical modeling using density functional calculations

Abstract

Density functional B3LYP calculations have been performed to investigate proton transport in orthoperiodic and orthotellurium acids, their salts MIO₆H₄ (M = Li, Rb, Cs) and CsH₅TeO₆, dimers of the salt*acid type MIO₆H₄*H₅IO₆ (M = Rb, Cs), CsIO₆H₄*H₆TeO₆, CsHSO₄*H₆TeO₆, Cs₂SO₄*H₆TeO₆, and also in double-substituted and binary salts Rb₂H₃IO₆ and Rb₄H₂I₂O₁₀. It has been shown that the energy of salt dimerization is 33–35 kcal mol⁻¹ and the activation barrier for proton migration between the neighboring octahedrons of the salt*acid → acid*salt type is calculated to be 3–13 kcal mol⁻¹. The activation energy of the proton migration along the octahedron, 20–30 kcal mol⁻¹, is comparable with the barrier for water molecule separation. Quantum-chemical calculations correlate with the results of X-ray and electrochemical studies.