Hydration structure of trifluoromethanesulfonate studied by quantum chemical calculations

Our recent study based on infrared spectroscopy reported hydration structure of Nafion side chain terminal (S. Morita, K. Kitagawa, Temperature-dependent structure changes in Nafion ionomer studied by PCMW2D IR correlation spectroscopy, J. Mol. Struct. 974 (2010) 56–59). In the present study, detailed hydration structure of Nafion ionomer was explored by means of quantum chemical calculations (QCCs) using a model side chain terminal of trifluoromethanesulfonate (TFMS). The result indicates that the hydration of TFMS induces deprotonation of sulfonic acid group in TMFS and formation of hydronium anion with hydrating water molecules. Hydration energies of TFMS deprotonated anion with H3O+, H 5 O 2 + and H 7 O 3 + are calculated to be 599.6, 474.1 and 464.6 kJ mol−1, respectively.