Novel access to ionic liquids based on trivalent metal–EDTA complexes and their thermal and electrochemical characterization

Abstract Two series of ionic liquids (ILs) consisting in metal-EDTA complex anions ([MEDTA], with V, Cr, Mn, Fe and Co as metal center) and 1-butyl-3-methylimidazolium ([BMIM]) or trioctylmethylphosphonium ([TOMP]) cations have been prepared via a new synthetic approach based on the related acidic EDTA complexes (HMEDTA). A strong influence of both the coordinated metal and the cation type on the thermal behavior of the obtained ILs was assessed through DSC and TGA, while the solubility features were found to be primarily affected by the cation nature. The observed solubility results for [TOMP] series ILs in organic solvents showed the preparation of ILs as an effective way to solubilize metal-EDTA complexes into non-aqueous solutions, opening new investigation potential and applicative perspectives. The electrochemical properties of the synthesized ILs have been studied both in aqueous and non-aqueous environments, providing insights on the strong solvent effect on metal-EDTA complexes electrochemistry and, for many of the ILs, showing promising characteristics for electrochemical applications both in water and in organic solvents.