Evaluating the influence of the diamine unit (ethylenediamine, piperazine and homopiperazine) on the molecular structure, physical chemical properties and superoxide dismutase activity of copper complexes

Abstract The synthesis, characterization and superoxide dismutase (SOD) mimetic activity of three copper(II) complexes are presented. The complexes were synthesized with similar ligands that differ from each other in their diamine units (ethylenediamine, piperazine and homopiperazine). Two propanamide units were attached to these diamines, resulting in tetradentate ligands that induce N 2 O 2 coordination to the copper(II) ions. The X-ray analyses of the complexes showed that the complex containing the ethylenediamine unit presents a square planar geometry, whereas the structures of the complexes containing piperazine and homopiperazine were square pyramidal due to the presence of water in the apical position. Studies in solution indicated that the complexes showed a pseudo-octahedral geometry in water. This geometry was maintained in a DMSO solution for the complexes containing ethylenediamine and homopiperazine. However, the complex containing piperazine presented a five coordinate copper center in a DMSO solution. All three complexes presented high SOD-like activity with IC 50 values in the nanomolar range (100–200 nmol dm −3 ).