A series of new benzimidazole containing compounds 2-((1-R-1-H-benzimidazol-2-yl)phenyl-imino)naphthol (R = methyl, ethyl or propyl, respectively) have been synthesized by Schiff base condensation of 2-(1-R-1-H-benzo[d]imidazol-2-yl)aniline and 2-hydroxy-1-naphthaldehyde. The reactions of with Cu(NO3)2·2.5H2O led to the corresponding copper(ii) complexes [Cu(L)(NO3)] . All the compounds were characterized by conventional analytical techniques and, for and , also by single-crystal X-ray analysis. The interactions of complexes with calf thymus DNA were studied by absorption and fluorescence spectroscopic techniques and the calculated binding constants (Kb) are in the range of 3.5 × 10(5) M(-1)-3.2 × 10(5) M(-1). Complexes effectively bind DNA through an intercalative mode, as proved by molecular docking studies. The binding affinity of the complexes decreases with the size increase of the N-alkyl substituent, in the order of > > , which is also in accord with the calculated LUMOcomplex energies. They show substantial in vitro cytotoxic effect against human lung (A-549), breast (MDA-MB-231) and cervical (HeLa) cancer cell lines. Complex exhibits a significant inhibitory effect on the proliferation of the A-549 cancer cells. The antiproliferative efficacy of has also been analysed by a DNA fragmentation assay, fluorescence activated cell sorting (FACS) and nuclear morphology using a fluorescence microscope. The possible mode for the apoptosis pathway of has also been evaluated by a reactive oxygen species (ROS) generation study.