Three Arene-Ru(II) compounds of 2-halogen-5-aminopyridine: Synthesis, characterization, and cytotoxicity

Three novel compounds, (η6-p-cymene)RuCl2(2-fluoro-5-aminopyridine) (compound 1), (η6-p-cymene)RuCl2(5-amino-2-chlorpyridine) (compound 2) and (η6-p-cymene)RuCl2(2-bromo- 5-aminopyridine) (compound 3), were synthesized and characterized. The compound 1 and 3 were determined by X-ray diffraction, showing a distorted piano-stool type of geometry with similar bond lengths and angles around the ruthenium. Compound 2 exhibited moderate in vitro activity against A549 and MCF-7 human cancer cells, the other two lower activities. The UV–vis and fluorescent absorption titrations showed that three compounds binded with CT-DNA in a minor groove. The intrinsic binding constants (Kb) were calculated to be 2.13(±0.03) × 105 M−1, 2.89(±0.03) × 105 M−1 and 2.45(±0.03) × 105 M−1 for compound 1, 2 and 3, respectively, by using UV–vis absorption titrations data. Among the three compound, the highest value of intrinsic binding constant of compound 2 was consistent with its highest cytoxicity against A549 and MCF-7 human cancer cells in vitro.