Absolute Single-Ion Solvation Free Energy Scale in Methanol Determined by the Lithium Cluster-Continuum Approach
2013
Pliego, Josefredo R. | Miguel, Elizabeth L. M.
Absolute solvation free energy of the lithium cation in methanol was calculated by the cluster-continuum quasichemical theory of solvation. Clusters with up to five methanol molecules were investigated using X3LYP, MP2, and MP4 methods with DZVP, 6-311+G(2df,2p), TZVPP+diff, and QZVPP+diff basis sets and including the cluster solvation through the PCM and SMD continuum models. Our calculations have determined a value of −118.1 kcal mol–¹ for the solvation free energy of the lithium, in close agreement with a value of −116.6 kcal mol–¹ consistent with the TATB assumption. Using data of solvation and transfer free energy of a pair of ions, electrode potentials and pKₐ, we have obtained the solvation free energy of 25 ions in methanol. Our analysis leads to a value of −253.6 kcal mol–¹ for the solvation free energy of the proton, which can be compared with the value of −263.5 kcal mol–¹ obtained by Kelly et al. using the cluster pair approximation. Considering that this difference is due to the methanol surface potential, we have estimated that it corresponds to −0.429 V.
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