Synthetic, structural, spectral and DNA binding aspects of copper(II), nickel(II) and zinc(II) dimers of new carboxylate-based tripodal ligand

Abstract

The synthesis, structural investigation, spectral properties and DNA binding aspects of three dimetallic complexes, [Cu2(L2)2(H2O)2]∙H2O (1), [Ni2(L2)2(H2O)2] (2) and [Zn2(L2)2(H2O)2] (3), based on carboxylate containing new asymmetric tripodal ligand, 3-(carboxymethyl-pyridin-2-ylmethyl-amino)-propionic acid (H2L2) are reported. All the complexes have been characterized by elemental analysis, solution molar electrical conductivity, FTIR, UV–Vis, mass spectrometry, including single crystal X-ray crystallography. The crystal structure of 1 reveals that the two copper(II) centers assume a six-coordinate distorted octahedral geometry with Cu---Cu separation of 3.283(2) Å. The single crystals of 2 and 3 could not be isolated; however, the DFT optimized structures of 2 and 3 disclose that two nickel(II) and zinc(II) centers are in a distorted octahedral geometry with Ni---Ni and Zn---Zn separations of 2.815 and 2.847 Å, respectively. In each of these complexes, the metal ions are bridged by the oxygen atoms of the propionate arms of two ligands in a μ2:η2 monodentate fashion, forming a M2O2 central core. DNA binding abilities of all complexes have been studied by UV–Vis and fluorescence spectroscopy, and viscosity measurements.