A series of new palladium allyl complexes bearing purine-based carbenes derived from caffeine, theophylline and theobromine have been prepared and characterized by NMR spectroscopy, and elemental analysis and in two cases by single crystal X-ray diffraction. The cytotoxic and proapoptotic activities of compounds have been determined in vitro on human ovarian cancer A2780 and SKOV-3 cell lines. These experiments have shown that the palladium-allyl fragment induces a general cytotoxicity, but the choice of the supporting ligands is of paramount importance for achieving the best results. In particular complexes 4c, 4d and 5d exhibit a higher antiproliferative effect (IC₅₀: 0.09, 0.81 and 0.85 μM respectively) than cisplatin (IC₅₀: 1.5 μM) on A2780 cells, and 4d (IC₅₀: 1.7 μM vs. 5.94 μM) on SKOV-3 cell line. Moreover in many cases it has been proved that the cytotoxicity of our complexes is associated with the induction of apoptosis.

The synthesis of a new dinuclear Pd(i) complex bearing two bis(NHC) ligands is discussed. This compound exhibited excellent bioactivity against several cancer cell lines and low toxicity toward normal cells. Its mode of action is also discussed.