Linear free energy relationship for 4-substituted (o-phenylenediamine)platinum(II) dichloride derivatives using quantum mechanical descriptors

In the present work quantum mechanical methods were used to calculate the rate constants for the first step of the aquation of a set of 4-substituted (o-phenylenediamine)platinum(II) dichloride derivatives containing electron-donating and withdrawing substituents at the 4-position of the aromatic ring. A linear free energy relationship was obtained for log(kX/kH), k being the rate constant for the first step of hydrolysis, and the electronic Hammett constants σm and σp. The results showed that electron-donating groups promote the hydrolysis reaction. The quantitative models described here may be useful for the rational design of new, less mutagenic drugs based on platinum complexes.