Synthesis, characterization and cytotoxicity of novel Pt(II) κ2O,O′-acetylacetonate complexes with nitrogen ligands

Synthetic procedures to obtain the new β-diketonate compounds [Pt(acac-κ2O,O′)(acac-κ-C3)(NH3)] (1) and [Pt(acac-κ2O,O′)(acac-κ-C3)(py)] (2) and their characterization by multinuclear, multidimensional NMR spectroscopy are reported. The new complexes have been designed and synthetized in order to establish the role of the sulphur ligand (DMSO/DMS) in the cytotoxic activity of [Pt(acac-κ2O,O′)(acac-κ-C3)(DMSO)] and [Pt(acac-κ2O,O′)(acac-κ-C3)(DMS)]. These complexes, already reported by our research group, were extensively studied for their outstanding biological activities. [Pt(acac-κ2O,O′)(acac-κ-C3)(DMS)] showed high cytotoxicity on cisplatin resistant cell lines and selective cytotoxic effects against breast cancer cells in primary cultures at concentrations lower than cisplatin. The new β-diketonate complexes (1 and 2), containing a nitrogen ligand (NH3 or pyridine) in place of DMSO/DMS ligand, have been obtained and isolated as stable products by cleavage of binuclear [{PtI2(NH3)}2] or starting with cis-[PtI2(py)2] monomer in the presence of excess acac. In this respect the used synthetic pathways were completely different from those previously used in the case of analogues containing sulphur ligands (DMSO/DMS). Preliminary in vitro cytotoxic effects (MTT and clonogenic assays) of complex 1 on cisplatin resistant MCF-7 breast cancer cell line are reported and compared with the [Pt(acac-κ2O,O′)(acac-κ-C3)(DMS)] activity.