Mononuclear zinc(II) complexes of 2-((2-(piperazin-1-yl)ethylimino)methyl)-4-substituted phenols: Synthesis, structural characterization, DNA binding and cheminuclease activities

•The molecular structure of complex was elucidated by single crystal XRD analysis.•DNA binding studies support the intercalative mode of binding.•Cleavage mechanism implies the involvement of hydroxyl radical as ROS.•Complex containing the hydrophobic CH3 substituent shows higher DNA interactions.

Four new zinc(II) complexes [Zn(HL1–4)Cl2] (1–4), where HL1–4 = 2-((2-(piperazin-1-yl)ethylimino)methyl)-4-substituted phenols, have been isolated and fully characterized using various spectro-analytical techniques. The X-ray crystal structure of complex 4 shows the distorted trigonal–bipyramidal coordination geometry around zinc(II) ion. The crystal packing is stabilized by intermolecular NH⋯O hydrogen bonding interaction. The complexes display no d–d electronic band in the visible region due to d10 electronic configuration of zinc(II) ion. The electrochemical properties of the synthesized ligands and their complexes exhibit similar voltammogram at reduction potential due to electrochemically innocent Zn(II) ion, which evidenced that the electron transfer is due to the nature of the ligand. Binding interaction of complexes with calf thymus DNA was studied by UV–Vis absorption titration, viscometric titration and cyclic voltammetry. All complexes bind with CT DNA by intercalation, giving the binding affinity in the order of 2 > 1 ≫ 3 > 4. The prominent cheminuclease activity of complexes on plasmid DNA (pBR322 DNA) was observed in the absence and presence of H2O2. Oxidative pathway reveals that the underlying mechanism involves hydroxyl radical.

Graphical abstractMononuclear zinc(II) complexes have been synthesized and characterized. X-ray crystal structure of complex 4 shows the distorted trigonal–bipyramidal geometry around the metal ion. Titration and voltammetry studies suggest the intercalation mode of binding with CT DNA. Oxidative cleavage of plasmid DNA proving the involvement of hydroxyl radical as ROS. DNA binding and cheminuclease activity exhibit a similar trend while expressing their potentials.Figure optionsDownload full-size imageDownload as PowerPoint slide