Self-Assembled Supported Ionic Liquids

Separation and reuse of the catalytically active metal complexes are persistent issues in homogeneous catalysis. Supported Ionic Liquid Phase (SILP) catalysts, where the catalytic center is dissolved in a thin film of a stable ionic liquid, deposited on a solid support, present a promising alternative. However, the dissolution of the metal center in the film leaves little control over its position and its activity. We present here four novel, task-specific ionic liquids [FPhnImHR]I (n=1, 2; R=PEG2, C12H25), designed to self-assemble on a silica surface without any covalent bonding and offering a metal binding site in a controlled distance to the support. Advanced multinuclear solid-state NMR spectroscopic techniques under Magic Angle Spinning, complemented by molecular dynamics (MD) simulations, allow us to determine their molecular conformation when deposited inside SBA-15 as a model silica support. We provide here conceptual proof for a rational design of ionic liquids self-assembling into thin films, opening an avenue for a second, improved generation of SILP catalysts. Supported Ionic Liquid Phase catalysts combine advantages from homogeneous and heterogeneous catalysis. Control of the catalyst position in the IL film will boost their performance. Four ionic liquids are presented with NHC ligands deposited on SBA-15. Solid-state NMR and MD simulations yield a full model of the IL self-assembled monolayer.+ image