Design, synthesis and characterization of hybrid ionic liquid supramolecular gels – a computational and laboratory study

In this study, we have developed functionalized mono- and dicationic 1,4-diazabicyclo[2.2.2]octane (DABCO) based ionic liquid salts ([CnDABCO+][Br−] or ([Bz CnDABCO2+] [2Br−]. For the dicationic salts, the nitrogen atoms of DABCO were conjugated to a benzyl group at one end and various long-chain alkyl groups – where n ranged from 10 to 18—at the other end. The interactions of the DABCO salts with ionic liquids such as 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [Bmim] [Ntf2] and 1-butyl-3- methylimidazolium dicyanamide [Bmim] [DCA] were examined computationally. As proof of concept, the most optimal DABCO salts were synthesized and their gelation ability with ionic liquids [Bmim] [Ntf2] and [Bmim] [DCA] was examined. Our results indicate that the length of alkyl chains of the DABCO salts as well as the anionic component of the ionic liquids played a key role in the gelation process. The DABCO salts with n > 12 formed gels more efficiently in the presence of [Bmim] [Ntf2], while [Bmim] [DCA] gels were formed when n > 14. Furthermore, the dicationic DABCO salt gels were found to form nanofibers or nanowires in the presence of [Bmim] [Ntf2] while the [Bmim] [DCA] gels exhibited gelatinous structures. The monocationic DABCO salts formed dense nanorods or nanofibrillar structures regardless of the ionic liquid components. The thermal properties of the gels indicated that overall the gels formed with [Bmim] [Ntf2] showed higher stability. Additionally, we explored the ability of the gels to extract the environmental pollutant dye methyl orange. Our results indicated that the gels were able to extract the dye efficiently and thus may be potentially developed for trapping environmental pollutants from industrial waste. This study provides a better understanding of the interactions occurring between the DABCO salts and the ILs [Bmim] [DCA] and [Bmim] [Ntf2] and may open new doors for developing nanoscale gelatinous structures for applications in environmental remediation.