Imidazolium acetate ionic liquids are of specific interest, since due to the basicity of the acetate anion a proton transfer from the cation to the anion is possible, providing the special feature of intrinsic carbene activity for these materials. This opens a wide variety of possible applications, including chemical carbon dioxide absorption, organocatalysis and biomass processing. However, it was still not clear until very recently how imidazolium acetates can show carbene-like activities, and many chemical and structural questions arise regarding the corresponding reactions. In this presentation our ab initio molecular dynamics simulations and static quantum chemical calculations will be presented, revealing the chemical properties of these ionic liquids that lead to the accessibility of carbenes, and to the chemical absorption of carbon dioxide.Although the Lewis acid CO2 should (locally) decrease the carbene formation by quenching the basicity of the acetate anions, due to the competing solute-cation and cation-anion interactions this effect of the solute-anion interplay is suppressed, hence the carbene activity is retained. Moreover, the neutral CO2 inserts defects in the charge network, which also suppress the destabilization of the neutral carbene in the solution with respect to the charged imidazolium cation. The basic acetate anion prohibits the formation of the highly stable C---H-C type hydrogen bonds between the carbene and the cation's ring hydrogen atoms by occupying these positions, making the carbene preserving its reactivity in the liquid. Apart from these results, the possible use of this versatile ionic liquid in nuclear waste management will also be discussed, showing the possibility of carbene complex formation in the liquid from inorganic uranyl(VI) salts, which indicates a possibly of higher solubility for uranyl derivatives in these ionic liquids.

Absorbtion of carbon dioxide in ionic liquids: A mechanistic view

248th National Meeting (2014)

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