Synthetic Strategies for Tailoring the Physicochemical and Magnetic Properties of Hydrophobic Magnetic Ionic Liquids

Abstract

Magnetic ionic liquids (MILs) are a subclass of ionic liquids (ILs) containing paramagnetic components and are readily manipulated by an external magnetic field. Due to their hydrophilic nature, very few applications of MILs in aqueous systems have been reported. In this study, three general classes of hydrophobic MILs including monocationic, symmetrical/unsymmetrical dicationic, and symmetrical/unsymmetrical tricationic MILs were synthesized and characterized. By tuning the structure of the MIL, various physicochemical properties including water solubility, magnetic susceptibility, and melting point were regulated. MILs synthesized with the benzimidazolium cation were shown to exhibit lower water solubility (0.1% (w/v)) when compared to those containing imidazolium cations (0.25% (w/v)). By incorporating asymmetry into the cationic component of the MIL, the melting point of dicationic MILs was lowered while the effective magnetic moment (μeff) and hydrophobicity remained unchanged. Tricationic MILs paired with three [FeCl3Br–] anions exhibited an μeff as high as 11.76 Bohr magnetons (μB), the highest ever reported for MILs. The synthetic strategies employed in this study facilitate the generation of hydrophobic MILs that show great promise for liquid–liquid extraction and catalytic studies where the MIL can be easily removed or in microfluidic applications where the MIL microdroplet can be manipulated by an external field.

Identifying important structural features of ionic liquid stationary phases for the selective separation of nonpolar analytes by comprehensive two-dimensional gas chromatography

“…The halide counteranion was then exchanged to [FeCl 3 Br] − using equimolar amounts of iron(III) chloride hexahydrate in methanol to obtain IL 1. ILs 2, 4-10 were synthesized following previously reported procedures [32,33]. The synthetic route for the dication platform is shown in Fig.…”

Ionic liquids: solvents and sorbents in sample preparation

“…Analytes were readily introduced to the HS within aerosol droplets to facilitate rapid mass transfer into the IL extraction solvent. Yang et al found that analyte recoveries for the UNE-HS-IL-SDME method were comparable to a traditional hydrodistillation method using the [C 8 MIM + ][PF 6 − ] IL. Jiang et al demonstrated the benefit of using UNE-HS-IL-SDME to afford shorter extraction times (i.e., 25 min) relative to HS-SPME and stir-bar sorptive extraction (approx.…”

“…The chlorophenols were detected using HPLC with a dual wavelength detector. Another study used the [C 8 MIM + ][PF 6 − ] IL for the preconcentration of kanamycin sulfate before detection using electrochemiluminescence [34]. Wang et al investigated the extraction of three phthalate esters using the [C 4 MIM + ][PF 6 − ] as the acceptor phase and 1-nonanol as the extraction phase in a HF-LPME method [35].…”

“…To exploit the paramagnetic properties of MILs [89] in aqueous sample environments, hydrophobic components must be incorporated into the cation or anion of the MIL to minimize water solubility [7]. Recent efforts by our group and others to generate hydrophobic MILs have led to new opportunities in magnet-based aqueous extraction systems [8,[94][95][96].…”

“…In this study, the MIL was dispersed using acetone in combination with vortexing and subsequently collected using an external magnet. PAHs were back-extracted from the MIL using n-hexane, reconstituted in acetonitrile, and analyzed by HPLC with fluorescence detection to reveal that the [N 8 [98]. Relative to MIL-HS-SDME, MIL-DLLME required shorter extraction times and exhibited higher enrichment factors for nonvolatile compounds like acetophenone, 2-chloroaniline, and phenanthrene.…”