The 2,2`-bipyridine (bpy) ligand is one of the most widely used in coordination chemistry. It was first synthesized at the end of the 19^th century, with the iron(II) tris(bpy) being the first complex of this ligand ever observed¹. Over the years a diversity of metals complexed with bpy have been synthesized and extensively studied, and recently some applications of these complexes have been proposed, e.g. the use of iron (II) and nickel (II) tris(bpy) complexes for non-aqueous electrolytes of batteries² and the use of cobalt (II) tris(bpy) for thermo electrochemical cells³. Also, currently there is a growing interest in using ionic liquids (ILs) for electrochemical applications, because these compounds, broadly defined as salts that are liquid at or close to room temperature, usually present some interesting properties, such as low volatility, non-flammability and intrinsic ionic conductivity. The semi-integral electroanalysis is a powerful method for investigating the kinetics of redox reactions and determining the diffusion coefficients⁴ and was used to aid the interpretation of the electrochemical behaviour of tris(bpy) complexes.

The purpose of this work was to study the electrochemistry of the tris(bpy) complexes of cobalt (II)⁵, nickel (II) and iron (II)⁶ in ILs and organic solvents, thus contributing to the understanding of how these compounds behave in these media. Four ILs (two having the imidazolium cation and two the pyrrolidinium cation) and three organic solvents were used and the basic electrochemical properties of these complexes were investigated, including the redox potentials and the chemical and electrochemical reversibility of the redox reactions, as well as the kinetics of the oxidation reactions. The semi-integral electroanalysis was used for determining diffusion coefficients and for a qualitative analysis of the reversibility of the redox reactions.

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