The Buoy Effect: Surface Enrichment of a Pt Complex in IL Solution by Ligand Design

The targeted enrichment of a Pt complex with an ionic liquid (IL)‐derived ligand system in IL solution is demonstrated by using angle‐resolved X‐ray photoelectron spectroscopy. When the ligand system is complemented with fluorinated side chains, the complex accumulates strongly at the IL/gas interface, while in an equivalent solution of a complex without these substituents no such effect could be observed. This buoy‐like behavior induces strong population of the complex at the outermost molecular layer close to surface saturation, which was studied over a range from 5 to 30 %(mol). The surface enrichment was found to be most efficient at the lowest concentration, which is particularly favorable for catalytic applications such as supported ionic‐liquid‐phase (SILP) catalysis.