Cytotoxic Activities of Half-sandwich M(III) Complexes (m=rh, Ir) Bearing Chloro-substituted Bidentate-coordinated Phenanthroline or Terpyridine Ligands

The synthesis and characterization of four compounds [M(& eta;(5)-C5Me5)(N<^>N)Cl]PF6 [N<^>N=4,7-dichloro-1,10-phenanthroline with M=Rh, 1, and M=Ir, 2, and N<^>N=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine in the & kappa;N-2,N'-coordination mode with M=Rh, 3, and M=Ir, 4] are described. All compounds were characterized by spectroscopic means and their molecular structures in the crystal were confirmed by single-crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated by MTT assay against the three cancer cell lines HeLa (cervical carcinoma), HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma). The complexes 3 and 4 display promising activity with IC50 values of 1 & mu;M. The rhodium(III) complex 1 also shows highly improved cytotoxicity compared to cisplatin against the cancer cell lines HT-29 and MCF-7. In contrast to this, the iridium(III) complex 2 is even less active against the HeLa cell line than cisplatin.