Diffusion Coefficient of Ferrocene and Its Derivatives In Ionic Liquids

Ferrocene has been recommended for use as internal reference redox couple in room temperature ionic liquids and in conventional aprotic solvents. In this study, the electrochemical behavior of ferrocene, ethylferrocene, and 1-1'-dimethylferrocene in a variety of room temperature ionic liquids is reported. Electrochemical techniques, such as cyclic voltammetry and impedance spectroscopy were used to measure diffusion coefficients of ferrocene, ethylferrocene, and 1-1'-dimethylferrocene in a variety of ionic liquids at different concentrations and temperatures. Diffusion coefficients are found to be on the order of ~10^-7 cm^2/sec. The role of side groups of ferrocene and the properties of ionic liquids on diffusivities will be discussed. Finally, a correlation for diffusion coefficients of ferrocene derivatives in ionic liquids will be presented.