In this study, the new copper(II) based cytosine arabinoside (ara-C) analog was synthesized and characterized by analytical and spectroscopic methods. Especially the data obtained from FT-IR spectroscopy showed that ara-C coordinated with copper(II) ions through -C = O and -N-ring groups and formed a complex compound in a tetrahedral structure. The proposed structure of this dimeric copper(II) complex was defined as [Cu-2(ara-C)(2)Cl-4]. Also, the ability of both compounds to bind to double helix fish sperm DNA (dsDNA) and the damage to the HeLa cell line was investigated. All theoretical chemical activity analyses (hardness and softness parameters, Fukui functions, net charges) of the ara-C and [Cu-2(ara-C)(2)Cl-4] molecules were performed with DFT with mixed basis set including LANL2DZ for Cu atom and 6-311G(d,p) for carbon, oxygen, nitrogen, chlorine and hydrogen atoms with B3LYP functional was applied. The stability of the molecule arising from hyperconjugative interactions, charge delocalization was analyzed by using natural bond orbital analysis (NBO) for optimized structure of [Cu-2(ara-C)(2)Cl-4]. Also, the interactions between the studied molecules (ara-C and [Cu-2(ara-C)(2)Cl-4] with DNA bases such as adenine, cytosine, guanine, and thymine were investigated by using the ECT (electrophilicity-based charge transfer) method. Furthermore, the best binding sites of the DNA (PDB:1BNA) protein to the ligands (ara-C and [Cu-2(ara-C)(2)Cl-4] were examined and the binding energies and interaction states were determined by molecular docking study. (c) 2022 Published by Elsevier B.V.