Application of microwave-assisted heating to the synthesis of Pt(II) complexes

The microwave-assisted synthesis of Pt(II) complexes containing several pyridines (i.e., pyridine L1, 2-picoline L2, 3-picoline L3, 4-picoline L4, 2,2′-bipyridine L5) is reported. For L1-L5, the reaction was successful in about 50% yield with all the ligands except L2. The same method applied to 4,4′-bis(2-morpholinoethoxy)-2,2′-bipyridine (L6, a ligand showing interesting antiproliferative properties because of a high DNA affinity), was unsatisfactory. The corresponding complex cis-[PtCl₂(L6)] was obtained only heating at reflux a mixture of [PtCl₂(1,5-cyclooctadiene)] and L6 in acetonitrile for 24 h. Antiproliferative activity of [PtCl₂(L6)] on four cancer cell lines (ovarian A2780 and its cisplatin-resistant variant A2780cisR, prostate PC3 and breast cancer MDA-MB-231) was compared with that of its ligand and the model complex [PtCl₂(L5)]. These studies showed that [PtCl₂(L6)] has just marginal activity towards the tested cells if compared with cisplatin.