Influence of RTIL Nanodomains on the Voltammetry and Spectroelectrochemistry Of Fullerene C60 in Benzonitrile/Room Temperature Ionic Liquids Mixtures
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The cyclic voltammetry of fullerene C60 was examined in mixed benzonitrile/RTIL solvents in order to probe the effect of nanodomains in the mixed RTIL/benzonitrile solutions and their effect upon the voltammetry. In probing the interactions of the fullerides (up to C603−) with RTILs, BMIm+ (1-butyl-3-methylimidazolium, mostly planar) and tetraalkylammonium (more spherical/flexible) salts were used. In order to investigate these shifts in more detail, the ΔE12° (=E°1–E°2) and ΔE23° (=E°2–E°3) values, which were independent of the reference potential, were used. At higher concentrations of the RTILs, greater stabilization of the more highly charged fullerides were observed. These shifts were attributed to the interaction of the fullerides with nanodomains of the RTIL. This was further confirmed by examining the shifts in the E1/2 values of non-RTIL and RTIL salts at constant ionic strength and the changes in diffusion coefficient with %RTIL. The observed shifts in the E1/2 values with increased concentration of the RTIL salts could not be explained by ion pairing equilibria alone. Changes in the visible and near infrared spectra between benzonitrile and mixed benzonitrile/RTIL spectra were most significant for C603−, where voltammetric evidence indicates the strongest interaction between the fullerides and the RTIL. Among the RTILs studied, preliminary DFT calculations showed that the more flexible tetraalkylammonium ion was able to stabilize the C60-anionic species better than the planar BMIm+ species, under similar solution conditions.