Synthesis, characterization, solution equilibria and DNA binding of some mixed-ligand palladium(II) complexes.: Thermodynamic models for carboplatin drug and analogous compounds

A series of ternary complexes of palladium(II) with ethylenediamine (en) and dicarboxylate ligands of the type [Pd(en)L], where L = malonato (I), methylinalonato (II), dimethylmalonato (III) and 1,1-cyclobutanedicarboxylato (IV), were synthesized and characterized by elemental analysis, IR spectroscopy and TG-DTA thermal analysis. The X-ray crystal structures for the compounds H and IV are described. The stability of these dicarboxylato complexes in aqueous solution has been investigated by potentiometric measurements. The formation constants calculated for these dicarboxylato complexes and those reported in the literature for the corresponding hydroxo- and chloro- complexes of the Pd(en) moiety have been used to obtain species distribution diagrams. In addition, the interaction of the dicarboxylato complexes and the dichloro complex [Pd(en)Cl-2] (V) with DNA was studied by various methods. UV spectral data and melting curves do not reveal differences in the reactivity of these complexes with DNA. This and other features are correlated with the stability of the complexes studied. (C) 2002 Elsevier Science B.V. All rights reserved.