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

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. (C) 2018 Elsevier B.V. All rights reserved.