Proposta mecanística de redução de oxigênio e oxidação de água por complexos de cobre contendo bipiridinas modificadas

Abstract

The electronic properties of copper complexes have sparked great interest in the scientific community due to their biochemical potential in the development of cancer treatment drugs. In addition to their potential in cancer treatment, it also shows catalytic properties that could be used to promote water splitting with production of reactive oxygen species (ROS). Studies have explored the ability of these compounds to inhibit the growth of cancer cells, induce apoptosis, and reduce tumor angiogenesis. One strategy employed in this field is the structural modification of copper complexes, with the incorporation of ligands containing polycyclic aromatic hydrocarbons (PAH’s). These ligands confer specific characteristics to the complexes, allowing them to be designed to target specific cancer cells. This approach increases the selectivity and efficacy of the complexes, making them more effective in cancer treatment. Another important aspect is the ability of copper complexes to generate radical species, with a focus on the hydroxyl radical (HO•). This, in turn, has been frequently associated in the literature with the possibility of water oxidation by copper complexes. Although the mechanisms involved in this reaction are not yet fully elucidated, they arouse great interest in both the biochemical and energy fields. These approaches, which involve the structural modification of copper complexes and their ability to generate radical species, offer promising potential for the development of new anticancer drugs. These advancements significantly contribute to the search for more effective and less toxic treatments for cancer patients. In this context, the present work aims to present the synthesis and characterization of two novel copper(II) complexes, using ligands containing the naphthalene and anthracene fragments, PAH’s linked to a bipyridine through an imine group, and denoted as [Cu(mbpy-naph)2]2+ where mbpy-naph is the ligand (1-(4'-methyl-[2,2'-bipyridin]-4-yl)-N-(naphthalen-2-yl)methanimine) and [Cu(mbpy-anth)2]2+, where mbpy-anth is the ligand (N-(anthracen-2-yl)-1-(4'-methyl-[2,2'-bipyridin]-4-yl)methanimine). It was identified that the synthesized compounds can undergo spontaneous reduction in the presence of traces of water, resulting in the formation of the hydroxyl radical as one of the reaction products. Additionally, the ability of these compounds to generate superoxide radical and hydrogen peroxide was observed, indicating their capability in both water oxidation and reduction of molecular oxygen in the solution. Based on the obtained results, a mechanism was proposed to explain the two redox pathways.