Synthesis of paramagnetic polymers using ionic liquid chemistry

Herein, the synthesis of polymeric ionic liquids (PILs) with paramagnetic anions based on tetrachloroferrate(III) (FeCl4-) and tetrabromoferrate(III) (FeBr4-) is presented. The formation of the novel polymers encompassing the paramagnetic anions is proven by UV-VIS and Raman spectroscopy. Paramagnetic properties are analyzed using a SQUID measuring system. Some of the obtained PILs show higher magnetic susceptibility values than previously measured for paramagnetic ionic liquids. It is further found that the magnetic susceptibility can be tailored by controlling the iron content in the anion. Interestingly, casted films of the PILs show a strong response to a neodymium magnet. As a potential application, a microgel based on a paramagnetic PIL is used as a reusable catalyst in Friedel-Crafts alkylation. The paramagnetic PIL microgel can be easily separated and reused after the reaction making these new materials interesting for green chemistry processes.