Investigation of DNA Binding of Newly Designed Zn (II) Complexes With N-N and O-O Donor Ligands as Potential Antioxidants: Spectroscopic, Electrochemical, and Molecular Docking Studies

Abstract

The complexes of [Zn (DAP)(SA)] (1) and [Zn (bpy)(DAP)]Cl₂ (2) (where DAP is 3,4-diaminobenzophenone, SA is a dianion of salicylate, and bpy is 2,2′-bipyridine) were synthesized and characterized using various techniques such as ¹H NMR, ESI-Mass, ¹³C NMR, FT-IR, thermal gravimetric analysis (TGA), and UV–Vis. The formation of these complexes was supported by theoretical DFT approach. It reveals that these complexes have tetrahedral geometry. The interaction of these complexes with CT-DNA was studied by different methods. The UV–Vis titration revealed a bathochromic shift and significant hypochromicity at 260 nm for the absorption band of CT-DNA in the presence of these complexes. The studies in this work showed that the intercalative interaction between these complexes and CT-DNA is not the main or strongest mode, but other modes such as groove binding play role in their interactions. The achieved results from viscosity and electrochemical measurement confirmed this finding. 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 complex (1) with DNA occurs through hydrophobic forces and for complex (2) via hydrogen bonding and van der Waals interaction. The antioxidant activity of these complexes was investigated by DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay. According to this test, the antioxidant activity compared to the standard sample (vitamin C) is as follows: vitamin C > 2 > 1. Furthermore, the docking result proposed the binding of these complexes to the groove of DNA.