α-Diimine Cisplatin Derivatives: Synthesis, Structure, Cyclic Voltammetry and Cytotoxicity

Three new Pt(II) complexes [(dpp-DAD)PtCl(2)] (I), [(Mes-DAD(Me)(2))PtCl(2)] (II) and [(dpp-DAD(Me)(2))PtCl(2)] (III) were synthesized by the direct reaction of [(CH(3)CN)(2)PtCl(2)] and corresponding redox-active 1,4-diaza-1,3-butadienes (DAD). The compounds were isolated in a single crystal form and their molecular structures were determined by X-ray diffraction. The purity of the complexes and their stability in solution was confirmed by NMR analysis. The Pt(II) ions in all compounds are in a square planar environment. The electrochemical reduction of complexes I–III proceeds in two successive cathodic stages. The first quasi-reversible reduction leads to the relatively stable monoanionic complexes; the second cathodic stage is irreversible. The coordination of 1,4-diaza-1,3-butadienes ligands with PtCl(2) increases the reduction potential and the electron acceptor ability of the DAD ligands. The synthesized compounds were tested in relation to an adenocarcinoma of the ovary (SKOV3).