Structural characterization, ROS-inductive and proteasome inhibitory properties of ternary and binary copper(II) complexes of N2- and N2O2-ligands

• [Cu(edda)(en)] and [Cu(edda)] are neutral molecules in solid and solution.
• [Cu(en)Cl2] and [Cu2(Hedda)2Cl2] dissociate in solution to release their chlorides.
• Antiferromagnetic interaction in [Cu(edda)(en)] is weak but strong in [Cu2(Hedda)2Cl2].
• All the Cu(II) complexes produce more OH radicals than free Cu(II) ions.
• Cationic Cu(II) complex species inhibits proteasome more than neutral Cu(II) species.

The four copper(II) complexes involving ethylenediamine-N,N-diacetic acid (H2edda) and ethylenediamine (en), viz. [Cu(edda)(en)]H2O 1, [Cu(en)Cl2] 2, [Cu(edda)] 3 and [Cu2(Hedda)2Cl2] 4, were synthesized and characterized by various physical means. The crystal structures of 1 and 4 established them as mononuclear and dichlorido-bridged dicopper(II) complexes respectively. Complexes 1 and 4 showed weak and strong antiferromagnetic Cu…Cu interaction. Dynamic light scattering data of 3 suggested it to be a 3-dimensional coordination polymer in aqueous solution, gel and solid forms. The copper(II) species of 1–4 in aqueous solution were analysed by UV–visible and molar conductivity data. The weak hydroxyl radical-inducing property of free copper(II) ions in solution was enhanced by the chelation of both types of ligands. However, chelation of each or both of these ligands reduce the strong proteasome inhibitory property of the copper(II). All complexes inhibited the three proteolytic sites of the 20S proteasome, with the Trypsin-like site been mostly selectively inhibited.

Report synthesis and characterization of a set of copper(II) complexes of N2- and N2O2-ligands, including crystal structures of 1 and 4, together with their ROS-inducing and 20S proteasome inhibitory properties.Figure optionsDownload as PowerPoint slide