Spectroscopic and Electrochemical Studies of Europium(III) Chloride in Aluminum Chloride‐1‐Methyl‐3‐ethylimidazolium Chloride Room Temperature Molten Salts

Abstract

Absorption spectroscopy and titration experiments suggest that the addition of to basic aluminum chloride‐1‐methyl‐3‐ethylimidazolium chloride molten salt produces , and this species can be reduced at a glassy carbon electrode via a one‐electron, quasi‐reversible electrode reaction to produce Eu(II) species. The standard heterogeneous rate constant and the cathodic transfer coefficient in the 44.4/55.6 mole percent melt are and 0.7, respectively. The formal redox potential, E°′, obtained from Nernst plots is dependent upon the pCl of the melt, indicating the loss of chloride ion from the coordination sphere of the complex anion during reduction to form a species of the type for which x may be 2. It is possible to electrochemically generate stable solutions of this reduced species in the absence of oxygen. In acidic melt, the Eu(III)/(II) redox reaction appears to be a one‐electron reversible redox reaction. The average Stokes‐Einstein products for Eu(III) and Eu(II) species in both basic and acidic melts are measured. The values indicate that Eu(III) and Eu(II) species are less solvated in acidic melt than in basic melt. UV‐vis spectroscopic data are recorded for Eu(III) and Eu(II) species in both type of melts.