Appended Aromatic Moieties Determine the Cytotoxicity of Neutral Cyclometalated Platinum(II) Complexes Derived from 2-(2-Pyridyl)benzimidazole.

A new family of neutral chiral cyclometalated platinum(II) complexes with formula [Pt(κ-())Cl(κ-())], where () = 2-phenylpyridinate and () = 2-(2-pyridyl)benzimidazole () or (N-(CH)--(2-(2-pyridyl)benzimidazole) ligands; ( = phenyl (), naphthyl (), pyrenyl ()), have been synthesized and completely characterized. The unexpected κ coordination mode of the 2-(2-pyridyl)benzimidazole-derived ligands has been confirmed by spectroscopic techniques and X-ray diffraction. The aromatic moieties on the ligands in the new platinum(II) complexes have a remarkable influence on the cytotoxicity and in the binding mode to DNA. complexes internalized more than cisplatin in the SW480 cancer cells even though only and display high cytotoxicity. H NMR and P{H}NMR pointed out that and complexes bind covalently to GMP, while the electrophoresis assays and CD experiments indicate that only is able to covalently interact with DNA, inducing the same conformational changes in the plasmid DNA as cisplatin. Although the complex intercalates into DNA, probably through the pyrenyl moiety, no biological activity is observed.