Cu(II), Ni(II), Zn(II) and Fe(III) complexes containing a N2O2 donor ligand: Synthesis, characterization, DNA cleavage studies and crystal structure of [Cu(HL)Cl]

A polydentate ligand, H2L “[1-(5-isopropyl-2-methyl phenoxy)-3-(N-2-hydroxy benzyl-N-((pyridine-2-yl)amino) propan-2-ol]”, containing a N2O2 donor moiety was synthesized by refluxing 2-((5-isopropyl-2-methylphenoxy)methyl)oxirane and HBPA (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)amine). This synthesized ligand was used for the preparation of complexes with different metal ions, viz. [Cu(HL)Cl] (1), [Ni(HL)Cl] (2), [Zn(HL)Cl] (3) and [Fe(HL)Cl2] (4). The ligand and metal complexes were characterized by 1H NMR, mass, ESI-MS, elemental analysis, IR, UV–Vis and electron paramagnetic resonance (EPR) spectroscopy. The crystal structure for one of the complexes, [Cu(HL)Cl], was solved from the X-ray crystallography data. The structure of the complex, based on the trigonality index tau, suggests an intermediate geometry between square pyramidal (sp) and trigonal bipyramidal (tb). Both the ligand and the metal complexes show oxidative cleavage of plasmid DNA (pBR322) without addition of any exogenous agent, even at a concentration of 5 μM. The binding constants for these compounds were found to be in the range 5.33–0.065 × 105 M−1.

One of the predicted view (tbp) of the solved structure of [Cu(HL)Cl] complex from the single crystal X-ray crystallography.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of asymmetric polydentate ligand.
► Preparation of Cu(II), Ni(II), Fe(III) and Zn(II) complexes with N2O2 donor ligand.
► Crystal structure of Cu(II) complex having distorted trigonal bipyramidal geometry.
► DNA cleavage and DNA binding studies infer potential cleavage and binding by ligand, followed by complexes.