Transition metal compounds as probes for ionic liquid acidity

• Applicant: Professorin Dr. Anja-Verena Mudring
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 92117152

Whenever using ionic liquids as solvents, the solvation behaviour is of vital importance. It has been realized that the rule of thumb “like dissolves like” only poorly holds true for ILs as many ILs show rather poor solubilities for other salts. In a microscopic view all solvent-solute interactions can be looked at as special cases of donor-acceptor interactions. In this sight the Lewis acidity (electron acceptor power) and basicity (electron donor power) becomes important. It is the goal to investigate the acidity and basicity of ionic liquids by probing their acceptor and donor power through d- and f-metal compounds to establish independent scales for cation acidities and anion basicities. For ionic liquids it is anticipated that the cation is the primary acidic, electron accepting functionality whereas the IL anion is the main basic, electron donating functionality. In the past funding period we successfully established several independent methods to probe ILs for their acid-base character using UV-Vis absorption and luminescence spectroscopy as well as electrochemistry (cyclic voltammetry). We would now like to extend the successful methods to a wide range of ILs to test our methods to fully access their power and limitations. Special attention will be directed on how ILs bearing donating groups on the IL cation will influence the overall IL basicity which usually depends on the IL anion, and vice versa. Studies will be completed by methods based on vibrational spectroscopy (Raman). The final aim is to obtain a consistent and coherent picture of ionic liquid acidity by putting our results and those of others (inside and outside the SPP) together at the end of the program.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1191: Ionic Liquids