Synthesis, Characterization, and Antimicrobial Activity of Copper(II) Complexes Containing Ligands Derived from Azoles and Coumarins

Four Cu(II) complexes with coumarin-derived ligands are synthesized and fully characterized, confirming a ratio of 1:1 ligand to metal. The complex C3 presents a geometry between a square pyramid and a trigonal bipyramid with a supramolecular arrangement ruled by hydrogen bonding. Photophysical studies show absorption and emission bands mainly by the contribution of the aromatic groups, mainly by the coumarin moiety. Furthermore, the Cu(II)/Cu(I) pair of these complexes is associated with irreversible redox reactions, according to electrochemical investigations. In addition, the complexes are tested against bacterial and fungi strains, with being C1 the most active complex with fungicidal activity and a good selectivity index. It is suggested that the mechanism of action of the complex is oxidative distress. The studies of the mechanism of action show that the possible antifungal activity of the complexes is by oxidative distress, which is also supported by electrochemical studies and changes in the membrane potential using a probe, JC-1.