LAUSR

A new series of tetrafluorinated azobenzene‐imidazolium salts is reported. The azobenzene and imidazolium moieties were functionalized with long alkyl chains and connected via a methylene spacer of varying lengths (n = 3–12). They were characterized using FTIR and NMR spectroscopy, and elemental microanalysis. The cytotoxic potential of these ionic dimers against neuroblastoma (SHSY‐5Y), estrogen‐positive breast cancer cells (MCF‐7), triple‐negative breast cancer cells (MDA‐MB‐231), cervical cancer cells (HeLa), and human skin fibroblasts (Hs27) was evaluated using the MTT assay. The cytotoxicity of these ionic liquids (ILs) was dependent on the spacer length. A cut‐off effect was observed, wherein the cytotoxicity of the ILs was enhanced by increasing the nonpolar, hydrophobic spacer length up to a threshold and the potency was leveled off upon chain elongation. All ILs exhibited selective and remarkable inhibition potentials against HeLa cells in a dose‐dependent manner, which was 2–22 times stronger than that of etoposide, a clinical anticancer drug. These ILs were less toxic toward skin fibroblasts as implied by much higher IC50 values. The long‐spacer ILs (n = 7–10) were very selective toward HeLa cells. They had a broad safety window with selectivity indices ranging between 5.6 and 11.0. The selectivity of these compounds toward HeLa cells may serve as a new strategy for the design and development of safe and effective chemotherapeutics.