Effect of Dimethyl Carbonate on the Dynamic Properties and Ionicities of Ionic Liquids with [MIII(hfip)4]− (M=B, Al) Anions

Several ionic liquids (ILs) comprising [B(hfip)4]− [hfip=OCH(CF3)2] or [Al(hfip)4]− anions and imidazolium or ammonium cations were prepared and mixed with up to 270 mol % of dimethyl carbonate (DMC). The viscosities, conductivities, and self‐diffusion constants of these mixtures and, where possible, of the neat ILs were measured and compared with common [NTf2]− based ILs and their mixtures with DMC. A tremendous decrease of the viscosities and a likewise increase of the conductivities and diffusion constants can be achieved for all classes of ILs. However, the order of the conductivities is partially reversed in the diffusion data. This is probably due to the low dielectric constant of DMC and the, thus, favored ion pairing, as evidenced, for example, by the calculated ionicities. Altogether, our data show that the chemically robust, but high‐melting and more viscous [B(hfip)4]− ILs might be candidates for electrolytes when mixed with suitable molecular solvents. Less is more: An study of the viscosities, conductivities, and self‐diffusion constants of mixtures of dimethyl carbonate (DMC) with a variety of ionic liquids with highly fluorinated anions reveals a severe decrease of the amount of free charge carriers with increasing DMC content (see picture). However, owing to a reduction of the viscosity, the mixtures are more conductive than neat ionic liquids and open the possibility of using high‐melting [B(OCH(CF3)2)4]− salts as electrolytes.