Multinuclear NMR spectroscopy and antiproliferative activity in vitro of platinum(II) and palladium(II) complexes with 6-mercaptopurine

A series of Pd(II) and Pt(II) complexes with 6-mercaptopurine (6-Hmp) of formulae Pd(6-Hmp)2Cl2 (1), Pd(6-mp)2$2H2O (2), Pt(6-mp)2$2H2O (3), Pt(6-mp)(dmso)Cl (4) was synthesized and studied by IR, far-IR, 1H, 13C, 15N NMR. (1) has an ionic character and consists of distinct [Pd(6-Hmp)2]2C cations and uncoordinated ClK anions, whereas (2,3) are neutral species with central atoms bis-chelated by the deprotonated 6-mpK ligands. NMR studies suggest that S and N(7) are the complexation sites, while far-IR spectra indicate the squareplanar geometry of Pd(II) or Pt(II). In (4) the Pt(II) atom is coordinated by one chelating 6-mpK anion, S-bonded dmso molecule and a terminal chloride. The antiproliferative activity in vitro of (2–4) was tested against human leukaemia HL-60 cells, being exhibited for (2) at the level ca. six times lower than in case of cisplatin. q 2004 Elsevier B.V. All rights reserved.