Cytotoxic organometallic [Ru(η6-anethole)(en)(X)]PF6 (X = Br or I) complexes: Synthesis, characterization and in vitro biological evaluation

Abstract

Two new organometallic compounds with the general formula [Ru(η6-anethole)(en)(X)]PF6, where X=Br (5) or I (6) and en=ethylenediamine, were synthesized and fully characterized using standard techniques (NMR, MS and elemental analysis). Displacement of the proton and carbon aromatic chemical shifts of anethole to the upper field in both compounds indicated organometallic Ru(η6-anethole) bond formation, and the characteristic “piano-stool” structure of these types of compounds was confirmed by the single crystal X-ray diffraction of compound 5. Compounds 5 and 6 exhibited interesting cytotoxicity, especially toward the human colon tumor cell line HT-29, similar to the previously studied compound [Ru(η6-anethole)(en)(Cl)]PF6 (4). A slight tendency toward cytotoxicity could be observed by varying the halogen leaving group (IC50 value): 6 (10±2μM)>5 (18±2μM)=4 (18±3μM). Compound 6 showed 3-fold more biological activity in HT-29 cells than toward the non-tumor colon cell line CCD-841, making it an interesting candidate for further studies and drug development.