Proton Conductivity in Phenolsulfonic Acids and Their Salts

T. S. Zyubina

Institute of Problems of Chemical Physics, Russian Academy of Sciences, pr. Akademika Semenova 1, Chernogolovka,
Moscow oblast, 142432 Russia

Received August 7, 2007

Abstract—The geometric parameters and energies of crystal hydrates of aromatic sulfonic acids and their salts,
as well as the pathways of proton transport in them, were calculated by the DFT (B3LYP) method with the
631G** basis set. For aromatic sulfonic acids, the proton relay mechanism was shown to be energetically more
favorable than rotation of the HSO group or direct proton transfer. Calculations show that an increase in the
number of water molecules located near the HSO₃ group from one to four decreases the barrier from 6 to
0.3kcal/mol. Hence, a moderate increase in humidity should enhance the conductivity, which is fully consistent
with experimental data. Calculations predict that the salts where all protons are substituted by metal atoms are
unlikely to show good conductivity. Conversely, mixed salts, for example, H₃C₆(OH)(NaSO₃)(HSO₃) and
H₃C₆(OH)(RbSO₃)(HSO₃), are expected to be thermally stable and resistant to deliquescence with an increase
in the humidity of a medium and to have good conductivity.

DOI: 10.1134/S0036023608090155

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