"Half-sandwich" Schiff-base Ir(III) complexes as anticancer agents.

A series of "half-sandwich" Schiff-base Ir(III) complexes were synthesized and investigated for their in vitro activities against the leukemia K562 cell line. These compounds demonstrated antiproliferative activities against K562 cells with IC50 values of 0.26-4.77 μM. In particular, compound 10c showed cytotoxicity against five cancer cell lines/sublines and stronger activities than cisplatin in K562, K562/A02, MCF-7, MCF-7/ADM, and A549 cells. Mechanism studies illustrated that compound 10c increased the level of reactive oxygen species and induced apoptosis of K562 cells. This compound effectively decreased the mitochondrial membrane potential and the protein level of Bcl-2. It also increased the protein levels of Bax, caspase-3, and caspase-9, and led to release of cytochrome c in K562 cells, indicating that the apoptosis induced by compound 10c was mediated by the intrinsic mitochondria apoptosis pathway.