Synthesis and characterization of a new alkyne functionalized bis(pyrazolyl)methane ligand and of its Pd(II) complexes: Evaluation of their in vitro cytotoxic activity

A novel bis(pyrazolyl)methane ligand bearing alkyne substituents (single bondCtriple bond; length of mdashCsingle bondtBu) in the C-4 position of the pyrazole rings has been synthesized together with its Pd(II) dichloride and diacetate complexes. Both the Pd(II) complexes are monomeric species stable in the solid state and in organic solution. The crystal structure of the Pd(II) dichloride complex displays a slightly distorted square-planar geometry and the molecules tend to form dimers associated through π–π stacking interactions between the pyrazolyl rings. The in vitro antitumor activities of the free ligand and of its corresponding Pd(II) complexes toward some human cancer cell lines, such as HeLa, SHSY-5Y and K562, have shown to be lower than cisplatin but with a better response in comparison to their parent free ligand.