Structural, Magnetic, DFT, and Biological Studies of Mononuclear and Dinuclear Cu-II Complexes with Bidentate N-Heteroaromatic Schiff Base Ligands

Abstract

Copper(II) complexes with the condensation derivative of methyl hydrazinoacetate and 2-acetylpyridine were synthesized. The X-ray crystal structures for both complexes revealed that they are polymerized isomers. A common feature of both complexes is the bidentate coordination of the ligand by one hydrazone and one pyridine nitrogen atom. In the monomeric complex, the copper(II) center is tetracoordinate, whereas dimerization through chlorido bridges results in a pentacoordinate arrangement about the metal ions in the dimer. The electronic and magnetic properties of both complexes are discussed on the basis of their X-ray structures, electron paramagnetic resonance (EPR) spectroscopy studies, and superconducting quantum interference device (SQUID) magnetization measurements combined with DFT calculations. Magnetostructural comparisons with structurally similar copper(II) complexes are also provided, and a possible correlation has been established. The antitumor activities of the Cu-II complexes were investigated against six different cancer cell lines, and the results suggest that the antiglioma action of the dimeric species is based on oxidative-stress-mediated phosphatidylserine externalization and caspase activation, which indicate apoptosis.