Correlation between hydration and deprotonation in hexaaqua metal complexes

The hydration energy of metallic cations determined with density functional calculations using a double-numerical plus p-polarization basis set, related to the acidity constants of hexaaqua metal complexes, was investigated in the present study. From the results calculated by Vosko-Wilk-Nusair (VWN), Becke-Perdew (BP) and Becke-Lee-Yang-Parr (BLYP) density functionals, a global linear correlation with the observed acidity constants in both main group [Mg(II), Ca(II) and Al(III)] and (post)transition group [Mn(II), Zn(II), Cd(II), Sc(III), Cr(III), Fe(III), Ga(III) and In(III)] hexaaqua metal complexes has been established: VWN density functional: pK(a) = 16.5760 + 0.0173E(hydr) kcal mol(-1) BP density functional: pK(a) = 15.7329 + 0.0182E(hydr) kcal mol(-1) BLYP density functional: pK(a) = 15.9448 + 0.0185E(hydr) kcal mol(-1) (C) 1998 Elsevier Science B.V. All rights reserved.