Fluorescigenic Magnetofluids Based on Gadolinium, Terbium, and Dysprosium-Containing Imidazolium Salts

Multistimuli responsive soft materials are urgently needed in many different fields, such as anticounterfeiting technology and microdroplet manipulation. Herein, the straightforward preparation of fluorescigenic magnetofluids by the introduction of the paramagnetic metal ions Gd³⁺, Tb³⁺, and Dy³⁺ into alkylimidazolium-based ionic liquids (ILs) is reported. Bright visible fluorescence was observed under UV irradiation for Tb- and Dy-containing ILs. Either pure samples or papers coated with these ILs exhibited pronounced magnetic responses. Consistent and stable structures of these salts were confirmed by systematical characterizations. Because of the competition of nitrate ligands, structural water in the precursors was eliminated easily under a vacuum. For Tb- and Dy-containing ILs, featured electronic transitions were observed and were assigned in the fluorescence spectra. The long lifetimes of these transitions were also confirmed. The field-cooling experiments showed that all of these ILs display paramagnetism at room temperature. At low temperature, small deviations from the Curie Law indicate the occurrence of antiferromagnetic coupling and spin canting in these ILs. Temperature-induced differences in magnetic properties were further verified by field-dependent magnetic susceptibility measurements carried out at 5 and 300 K.