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(k(X)/k(H)), k being the rate constant for the first step of hydrolysis, and the electronic Hammett constants sigma(m) and sigma(p). 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. (C) 2004 Elsevier Inc. All rights reserved.