Two new complexes i.e., [Zn(DAP)(8-QO)]Cl (1) and [Zn(DAP)(Phe)]Cl (2) were synthesized and characterized using various techniques (DAP is 3,4-diaminobenzophenone, 8-QO is an anion of 8-hydroxyquinoline, and Phe is the anion of phenylalanine amino acid). The cytotoxic activity of these complexes (1 and 2) in vitro conditions against HCT-116 colon cell lines and normal cells (NIH/3T3 fibroblast cells) were assessed and revealed promising results compared to cisplatin as a well-known anticancer drug. The in-detailed interaction of these complexes with CT-DNA was studied by UV–Vis absorption, fluorescence, gel electrophoresis, cyclic voltammetry (CV), and viscosimetry. The experimental studies in this work showed that these complexes can displace EB and compete with EB at the DNA binding site. Also, a competitive binding assay with the dye Hoechst 33258 as a known minor groove binder was studied by fluorescence emission spectroscopy. Based on the obtained results, it can be suggested that both intercalative and groove binding modes play a vital role in the interaction of these complexes with DNA. The fluorescence studies showed that the proposed mechanism of fluorescence quenching for both complexes is static quenching. The thermodynamic parameters (ΔH˚and ΔS˚) revealed that the interaction of both synthesized complexes with DNA takes place through hydrogen bonding and van der Waals forces.
