Electrochemistry Applied to the Evaluation of the Interaction between Coumarins and the Copper Metal Ion: An Experimental Study with a DFT-Based Analysis

Coumarin belongs to the benzopyrones family commonly found in vegetables such as Guaco. These compounds have a diversity of applications, especially in medicine, because they have vasodilatory, anti-inflammatory, anti-asthmatic, and anti-allergic properties. In addition, metal complexes using coumarins in their structures have been widely studied for therapeutic purposes. Due to the importance of these molecules, in this work, was studied the interaction between coumarin (CM) and 7-hydroxycoumarin (7OHCM), the main metabolite of coumarin, with the metal ion copper (II), which is naturally present in the environment. Cyclic voltammetry studies showed a reduction peak at 0.39 V and an oxidation peak at 0.47 V for the Cu-CM complex under pencil graphite electrode. Cu-7OHCM showed a reduction peak at 0.40 V and an oxidation peak at 0.49 V, both with reversible process characteristics. In the presence of coumarin, Cu+ is stabilized in solution. Theoretical data suggest the formation of the complex and stabilization of Cu+ in solution. After the interaction, a decrease in the energy of the system occurs, as well as an overlap of the HOMO orbitals of the two species was observed. Furthermore, the studies indicated that the Cu-CM complex is more stable than the Cu-7OHCM complex.