Synthesis, Structure and in Vitro Cytotoxic Studies of Novel Paramagnetic Palladium(III) Complexes with Hematoporphyrin IX

Two coordination compounds of Pd(III) with hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp), dinuclear [Pd(III)2(Hp-3H)Cl3(H2O)5]·2PdCl2, 1 and mononuclear [Pd(III)(Hp-2H)Cl(H2O)]·H2O, 2 were obtained and structurally characterized in solid state and solution using spectroscopic, thermal and magnetic methods. In the dinuclear complex, 1 one of the Pd(III) ions is coordinated to the deprotanated COO(-) groups from the side chains of the porphyrin ligand and the second Pd(III) ion - to two adjacent pyrrole N-atoms on the top of the porphyrin ring and a Pd(III)-Hp-Pd(III) system was formed. The Pd(III) ion in the mononuclear complex, 2 is incorporated in the porphyrin core. The Pd(III) centers in both complexes have a distorted octahedral coordination filled with additional donor species such as Cl(-) and H2O. The studied compounds showed in vitro cell growth inhibitory effects at micromolar concentration against a panel of human tumor cell lines. A DNA fragmentation assay indicated that the growth inhibitory effects are at least partly mediated by induction of apoptosis.