Synthesis, properties of pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) and the mutual solubility of (MRTILs + cyclohexane) and (MRTILs + n-octane) binary systems

The application of guanidinium-based ionic liquids (ILs) is a newly emerging area in the fields of extraction desulfurization. Herein, four novel pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) [CnTMG][FeCl3Br] (n = 2, 4, 6, 8) were synthesized and characterized by FT-IR, Raman and HRMS (ESI) spectra. The physical properties including thermal stability, density, viscosity, conductivity and magnetic properties were determined and revealed that the MRTILs were liquids at room temperature and have good thermal stability (Td > 250 °C), high magnetic susceptibility (>3.8 × 105 emu·g−1) and low viscosities (<160 mPa·s, 25 °C). Moreover, the mutual solubility behaviors for binary systems of MRTILs with representative non-polar organic solvents (cyclohexane, n-octane) were measured at temperatures from 5 to 65 °C, showed a low miscibility between MRTILs and organic solvents and a typical lower critical solution temperature (LCST) phenomenon. The results are supposed to provide useful information for further application as “green” liquid desulfurization extractants or others potential dispersive liquid-liquid microextraction applications.