Modeling the Proton Transport in Orthoperiodic and Orthotelluric Acids and Their Salts

Abstract

Orthoperiodic and orthotelluric acids, their salts MIO₆H₄ (M = Li, Rb, Cs) and CsH₅TeO₆, and dimers of the salt · acid type are calculated within density functional theory B3LYP and basis set LanL2DZ complemented by the polarizationd,p-functions. According to calculations, the salt · acid dimerization is energetically favorable for compounds MIO₆H₄ · H₅IO₆ (M = Rb, Cs) and CsIO₆H₄ · H₆TeO₆. The dimerization energy is equal to 138–146 kJ mol^–1. With relatively small activation energies equal to 4 kJ mol^–1 (M = Li) and 11 kJ mol^–1 (M = Rb, Cs), possible is rotation of octahedron IO₆ relative to the M atom in monomers of salt molecules. The proton transfer along an octahedron occurs with activation energies of 63–84 kJ mol^–1. The activation energy for the proton transfer between neighboring octahedrons of the type salt · acid → acid · salt equals 8–17 kJ mol^–1. Quantum-chemical calculations nicely conform to x-ray diffraction and electrochemical data.