Abstract Cu complexes were synthesized by substituting the hydrogen of the amine group of basic ligand 2, 2'-dipicoylamine (dpca) (complex 2) with CH₃CO (complex 1), phenyl (complex 3), and methyl (complex 4), respectively, and their DNA cleavage activity was investigated using linear dichroism (LD) and electrophoresis. The DNA cleavage efficiencies of Cu complexes 3 and 4 with phenyl and methyl, which are electron-donating functional groups, turned out to be the highest, and LD magnitudes rapidly decreased at 260 nm. In particular, Cu complex 3 showed a rapid LD magnitude reduction to 63% of the total for 90 minutes, and to 50% of the total at 12 minutes. DNA cleavage efficiencies were high in the order of phenyl > methyl >H = CH₃CO, and the highest DNA cleavage efficiency was observed in the presence of electron-donating groups. The electrophoresis results are also consistent with the changes in LD spectra over time. The Cu complexes (1-4) were found to cleave DNA through oxidative pathways, and the major ROS involved in DNA cleavage were the superoxide radical, singlet oxygen and hydroxyl radical.