A novel series of ferrocene tethered ionic liquids (ILs) has been synthesized by quaternization of 1-N-(ferrocenylmethyl)benzimidazole, 1-N-(ferrocenylmethyl)imidazole and 1-N-(ferrocenylmethyl)-1,2,4-triazole with long chain alkyl bromides. The synthesized ILs were screened for their anticancer activity against human breast cancer cell line MCF-7. ILs 2a-d and 4b displayed significant anticancer activity (GI(50) 0.016-0.064 mu M). IL 2d was found to be the most active with GI(50) value of 0.016 mu M which was even less than the standard drug doxorubicin (GI(50) = 0.018 mu M). AII ILs exhibit moderate to good selectivity against breast cancer cells MCF-7 over normal Vero cells. The ADME prediction studies revealed that all the ILs exhibit good pharmacological parameters. The molecular docking studies ascertained mode of action of the ILs via inhibition of lysosomal peptidase cathepsin B. (C) 2019 Elsevier B.V. All rights reserved.