BODIPY-based Ir(III) rectangles containing bis-benzimidazole ligands with highly selective toxicity obtained through self-assembly

Abstract

Selectivity for cancerous cells over normal cells remains one of the most important issues in studies of the biological activities of metal-based drugs. Herein, we show that benzimidazole-based iridium BODIPY rectangles can be used to selectively kill cancer cells. New tetranuclear (2 + 2) metalla-rectangles 1 and 2 were synthesized through the self-assembly of benzimidazole and BODIPY ligands with dichloro (pentamethylcyclopentadienyl) iridium dimer. The new complexes were fully characterized using different analytical techniques and a single-crystal structure was obtained for rectangle 2. Cytotoxicity studies revealed that complex 1 is highly selective for cervical cancer cells (HeLa) and human glioblastoma (U87) cancer cells over non-malignant lung fibroblast cells (WI38). The selectivity of complex 1 is much superior than that of well-known drug cisplatin. The cellular uptake and intracellular localization of these complexes were examined through confocal microscopy studies, and complex 1 was found to localize primarily in the cytoplasmic region of cancer cells. Furthermore, the interactions of these complexes with biomolecules in solution were investigated through spectroscopic studies.