Fe(II) complexes of 2,2':6',2''-terpyridine ligands functionalized with substituted-phenyl groups: synthesis, crystal...

With the aim of developing potential anticancer drug candidates, a series of Fe(II) complexes were synthesized using nine 2,2':6',2''-terpyridine ligands functionalized with substituted-phenyl groups, and their biological activities were systematically investigated. Their bis-terpyridine sandwich-like structures were determined by single crystal X-ray crystallography. In vitro antiproliferative experiments based on three human cancer cell lines, including human hepatoma cancer cell line (Bel-7402), human esophageal cancer cell line (Eca-109), and human cervical squamous cancer cell line (SiHa), indicate the high antiproliferation activities of these complexes compared with commercial cisplatin. And their toxicity to normal cells was estimated based on human normal hepatocyte (HL-7702) cell line. In particular, when the phenyl in terpyridine ligand was modified by a carboxyl group, the corresponding complex 3 exhibited much higher antiproliferation to cancer Bel-7402 cells (IC₅₀ = 3.653 μmol L^-1) than cisplatin and low toxicity to normal HL-7702 cells (IC₅₀ = 99.92 μmol L^-1), implying a significant selectivity for 3 in killing hepatoma cancer cells. Combined with the fact that iron element is more accessible than platin, this series of Fe(II) complexes comprises potential candidates for anticancer drugs with specific inhibition of hepatoma cancer. UV titration experiments and circular dichroism (CD) showed a strong binding affinity between these nine complexes and CT-DNA. However, molecular docking simulation revealed the competitive binding of DNA and protein to these complexes. Further, the interactions between these complexes and bovine serum albumin (BSA) have been studied by fluorescence titration and CD spectroscopy.