Thermal, Spectroscopic, Cyclic Voltammetric, and Biological Activity Studies of Cobalt(II), Nickel(II), and Copper(II) Complexes of Dicarboxylic Amino Acids and 8-Hydroxyquinoline

Mixed ligand complexes of Co^II, Ni^II and Cu^II with dicarboxylic amino acids (aspartic, glutamic or H₂ADA) as primary ligands and 8-hydroxyquinoline as a secondary ligand were prepared and characterized by elemental analysis, conductivity measurements, thermal analysis, cyclic voltammetry, and electronic and infrared (IR) spectroscopy. Cyclic voltammetry reveals a reversibility of the Cu^II/Cu^I couple, while the reactions of the Co^II and Ni^II complexes are irreversible. All complexes have a metal-to-ligand ratios of 1:1:1 and octahedral structures are suggested to be attained by interactions among both of the amino acids and 8-hydroxyquinoline anions with the metal ions. The reaction orders and activation energies have been computed by means of the Coats–Redfern and Horowitz–Metzger equations. The biological activity of selected complexes as anti-fungal agents has been tested.